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SF33 1/6 scale

Posted: 13 Oct 2018, 14:27
by Peter Balcombe
I have just started building a 2.5m version of the SF33 motor glider from the Cliff Charlesworth plan using a short kit of parts provided by Cliff Evans as usual.
Starting with the fuselage, this is built from two 1/16" balsa sides and a few sticks of 1/8 sq. balsa.
I built mine upside down, using the straight upper fuselage rail as a reference.
The difficult bit is to get the sides stuck to the formers without introducing a banana curve along the centreline.

The fuselage bottom will be covered with cross grain 1/16" balsa, except for the nose area which uses thicker balsa sheet, sanded to profile later.
SF33 Top_small.jpg
SF33 Bottom_small.jpg

Re: SF33 1/6 scale

Posted: 14 Oct 2018, 18:25
by FrankS
This looks a handy size, looking forward to following the build.

Re: SF33 1/6 scale

Posted: 14 Oct 2018, 21:38
by Peter Balcombe
Frank,
To further whet your appetite, you may be interested in the following link to a thread covering the build of the same model on another modelling forum.
There are some pictures of the almost complete model plus a flying shot further down.
http://www.gliderireland.net/forum/inde ... pic=3274.0

Peter

Re: SF33 1/6 scale

Posted: 14 Oct 2018, 22:04
by chris williams
Here's Cliff with the prototype at the old Lords Hill Club back in 2002...
06010001 copy.jpg

Re: SF33 1/6 scale

Posted: 15 Oct 2018, 14:34
by B Sharp
Peter, here are a couple of pictures of my version, which flew very successfully for many years. The airframe still resides in my attic and could be revived with the addition of radio and a motor.
Brian. :D
SF33_001.jpg
SF33_002.jpg
SF33_003.jpg

Re: SF33 1/6 scale

Posted: 15 Oct 2018, 16:08
by Peter Balcombe
Very nice indeed Brian 😀
I will need to have a chat about the arrangement for fixing the motor/clearing the forward former on the motor hatch.
The plan appears to show the top of the front bulkhead as a separate piece above the motor centre-line, but I wonder if that is intended to just be the cut line marking a separate part former (1A) to be used as the basis for the forward part of the top hatch (with much of the former removed to clear the motor.)
Can you recall if your motor bulkhead was fitted as top & bottom, or a single full height motor bulkhead, with duplicate top part for the hatch front?
Peter

Re: SF33 1/6 scale

Posted: 15 Oct 2018, 18:58
by B Sharp
Peter, I also was a bit confused with the front end. I used a Tornado BM600kv 1000 motor from Overlander with a Jeti Spin 44 esc. this was bolted to one solid former. Rather than a weakening hatch I built the front coming as solid. Interestingly I used a variable pitch setting prop from Steve Mettan at " Modelhaus" which allowed me to alter the pitch without changing the diameter.
Brian.

Re: SF33 1/6 scale

Posted: 15 Oct 2018, 19:54
by Peter Balcombe
Thanks for info Brian.
As I had already put in the supplied part-height (up to motor centre) front bulkhead (which allowed the fuselage to be built upside down over a plan view on a flat board, my plan is to now to epoxy the top part of the bulkhead on, but then fit a full bulkhead as a doubler.
I don’t expect a hatch to detract from the strength very much as the top is only 1/16” balsa sheet anyway.
The benefit is that it will allow easy access to the motor & ESC.
I have an old Dualsky XM3548CA-4 1080kv outrunner motor plus matching ESC which should provide ample power & run off a 3S LiPo.

Re: SF33 1/6 scale

Posted: 16 Oct 2018, 18:05
by Peter Balcombe
A bit more progress, including completion of sheeting & wheel attachment on the bottom (still needs shaping), addition of some of the upper fuselage formers and also the front bulkhead doubler after drilling the motor fixing holes.
Bottom sheeting
Bottom sheeting
Top formers
Top formers

Re: SF33 1/6 scale

Posted: 28 Oct 2018, 09:33
by Peter Balcombe
The liteply battery mounting plate, servo tray and tail surface bowden tubes have now been fitted to the fuselage.
Next job is to prepare the top turtle deck skin and set the curvature ready for fixing in place, probably using the ammonia technique.
Servo tray and rear tubes
Servo tray and rear tubes
Battery tray
Battery tray

Re: SF33 1/6 scale

Posted: 03 Nov 2018, 10:56
by Peter Balcombe
Now with the rear turtle deck fitted & ready to move on to fitting the forward part.
Rear turtle deck
Rear turtle deck

Re: SF33 1/6 scale

Posted: 05 Nov 2018, 16:41
by Peter Balcombe
Tailplane & rudder framework made up from 1/4" sq balsa, with additional 1/4" sheet infill as necessary.
It is only possible to make up the fin framework once these parts are clear of the board as the tailplane drawing overlaps the fin structure!
Tailplane_Rudder framework
Tailplane_Rudder framework

Re: SF33 1/6 scale

Posted: 12 Nov 2018, 18:58
by Peter Balcombe
Tail feathers now built and ready to add the control horns/make the upper/rear fuselage fairing.
Tail frames complete.jpg

Re: SF33 1/6 scale

Posted: 19 Nov 2018, 15:03
by Peter Balcombe
At the front end, the fuselage top has been skinned after making a simple framework for a removeable cowl.
Both sides of the cowl /fuselage interface were protected with a gloss masking tape to aid later removal & the joint line maked on the fusealge to aid placement of a scalpel blade to run around the joint later.
Everything went to plan & the cowl was easily removed once the glue had set.
The photos below show the cowl fitting ok with the motor in place.
The internal cowl framework can be seen on the 2nd pic.
Front cowl on
Front cowl on
Cowl internal framework
Cowl internal framework

Re: SF33 1/6 scale

Posted: 24 Nov 2018, 19:06
by Peter Balcombe
Canopy frame built from Liteply, with solid front & rear plus side rails to leave a space in the middle for a drop-in unit to be added for cockpit detail.
Attachment is a peg at front and a registration lip + small magnet at the rear.
Canopy frame in place
Canopy frame in place
Frame showing attachments
Frame showing attachments

Re: SF33 1/6 scale

Posted: 29 Nov 2018, 20:34
by Peter Balcombe
Moving on to the first wing, this is built up on the bottom spar with outer TE packed up to give 5mm washout over the aileron length.
The plan shows the 5mm TE glued directly to the rear of each rib, but I added a 6mm wide strip of 1/16" balsa sheet under the rear of each rib (same thickness as balsa skin/cap strips to be added later) and then added further 1/16" balsa strips between each rib. Once a further 6mm wide strip is added to the top, this will give a more solid edge to secure the TE.
The top spar, joiner tubes, angled root sub-spar and balsa dummy LE have also been fitted, plus upper aileron hinge spars, so this panel is nearly ready to have the top skin fitted.
Most of the internal details (servos, joiner tube area webbing, main spar webbing etc. will be fitted once the top skin is in place.
Wing structure
Wing structure
Wing root area
Wing root area

Re: SF33 1/6 scale

Posted: 07 Dec 2018, 15:28
by Peter Balcombe
A bit more progress over the last couple of weeks in that the top D box skin and most of the spar webbing is in place, together with the upper aileron spars & top skin.
A note here that although the plan calls for 3mm square balsa aileron spars, I have only fitted the upper ones so far as the notches need to be cut in situ as the plan doesn't show any slots on the rib templates. I also decided that as the top spars left little 'meat' on the ribs, I would leave the lower spar slots until the aileron area had top skin support.
Also, with the upper 1/16 balsa strip fitted across the rear of the rib, the 15mm wide TE strips could be added (inboard & outboard of the aileron break).
The remaining spar webbing has now been added, so the remaining upper skins can be added at the root end and the TE strips profiled to section.
The aileron & spoiler servo cables need to be added before the route is covered up by the lower D box skin.
Wing top D Box.jpg
Wing_Top D Box sheeted.jpg
Wing root.jpg

Re: SF33 1/6 scale

Posted: 13 Dec 2018, 12:19
by Peter Balcombe
With the 15mm wide TE strip added, spar webbing complete (including the angled spars), the upper root end skins have been fitted.
Next jobs are to fit the spoiler arrangement and servos prior to adding the lower D box skin.
Upper root end skin
Upper root end skin

Re: SF33 1/6 scale

Posted: 14 Dec 2018, 01:56
by Tonyw51
G'day Peter,
I have just today received my e plans and laser cutting e plan for this model. It is my first attempt at a scale model and I am finding your Build Log very helpful. I have sent off the cutting plans for a quote and hope I will be able to start the build early in the new year.

Looking forward to your continuing Log.

Cheers,

TonyW51
Melbourne, Aust.

Re: SF33 1/6 scale

Posted: 14 Dec 2018, 07:32
by Peter Balcombe
Hi Tony.
Very glad to have you on board.
The plan is probably not one of Cliffs best (God rest his soul), but I can help fill in missing info./telling you what I have done.
It does appear to turn out to make up a very nice looking model which appears to fly well.
The photos below are from an Irish build thread.
C1CC41CE-AD17-49F8-94CD-DAA0A23A9284.jpeg
C79374FE-2038-435B-B04C-C028B9DE37C0.jpeg
E3AD312B-9BB4-4C75-BD51-DE2073048BA0.jpeg
13C6BDA4-4F00-4BB6-829E-A057AF238365.jpeg

Re: SF33 1/6 scale

Posted: 14 Dec 2018, 21:34
by Tonyw51
Cheers Cliff. I'm onto that today.

Thanks and regards
Tony

Re: SF33 1/6 scale

Posted: 14 Dec 2018, 21:38
by Tonyw51
Thanks Peter, I must say that it was the Irish posting that sparked my initial interest in this model.

I look forward to asking for your assistance in the not too distant future.

Thanks and regards,

Tony

Re: SF33 1/6 scale

Posted: 27 Dec 2018, 13:54
by Chris V
Hi there, I am really interested in building this lovely little motor glider

What electric set up is everybody going to use ie which motor and what power set up 3s or 4s lipo ???

Thanks Chris

Re: SF33 1/6 scale

Posted: 27 Dec 2018, 16:15
by Peter Balcombe
I have an old Dualsky XM3548CA-4 1080kv motor plus Dualsky XC4118BA 40A ESC which is expected to be used with a 9x6 or 10x6 folding prop.
Battery will be 2 or 3S to suit power required (I cannot remember at the moment what the Irish model setup was).

Re: SF33 1/6 scale

Posted: 09 Jan 2019, 02:39
by Tonyw51
G'day Peter & Chris,
Much excitement in the workshop today with the arrival of my short kit from SC Models. So now have the plans printed, mirrored and printed again (and they are a perfect match), the short kit and the canopy "in the mail" from Sarick. I am in the process of completing a Brolga (2.0 mtr. Australian model) and as soon as it has had its maiden flight I shall start on the SF-33.

I am very happy with the quality of laser cutting and I shall start to rifle though the stores of strip and sheet to put together a complete kit, so all is looking good.
IMG_1941.jpg

Re: SF33 1/6 scale

Posted: 12 Jan 2019, 15:33
by Peter Balcombe
Spoiler now added together with servo & operation checked.
(Will need to be top wing surface hinged using film or tape in due course)

Aileron servo position added.
Spoiler + aileron servo
Spoiler + aileron servo
Spoiler servo
Spoiler servo

Re: SF33 1/6 scale

Posted: 12 Jan 2019, 17:21
by StephenB
Very neat job on the spoiler installation Peter with the servo nicely hidden by the sheeting.

Having never done it before(always used commercial brakes), but about to tackle this job, how have you secured the servo and is the pushrod connection a z bend at both ends? Have you mde the spoiler from 1/16" sheet with ply reinforcement? The way you have done it looks a lot simpler than some methods I have seen which often employ a 6mm sq. balsa framework and a more complicated linkage arrangement.

Re: SF33 1/6 scale

Posted: 12 Jan 2019, 20:31
by Peter Balcombe
Stephen,
Servo body located in a slot in an extra 2mm Liteply sub-rib, with servo mounting lugs trapped behind balsa spaced off rib by thickness of lug. A touch of hot glue will firmly secure in place before bottom sheeting added later.
Yes, thin wire pushrod with Z bend each end. Needs to be exact length, but cannot come loose later when under sheeting.
Spoiler is 1/16” balsa with thin ply backing & 1/16” epoxy board horn glued in.

Re: SF33 1/6 scale

Posted: 12 Jan 2019, 21:41
by chris williams
Er, what will you do if the servo fails later on, Peter?

Re: SF33 1/6 scale

Posted: 12 Jan 2019, 22:05
by Peter Balcombe
Chris,
Could make a small balsa framed hatch on underside with 1/16” sheet balsa cover taped in place if need be, else cut out a small area of lower skin and make good if and when a fault occurs.
Similar issue with aileron servo as the 1/6 scale wings aren’t very thick. However this servo will be in an open structure area, so covering can be cut away locally and a patch put over when done.
Peter

Re: SF33 1/6 scale

Posted: 12 Jan 2019, 22:36
by B Sharp
Don't worry too much about the servo failing Peter. I have buried servos in numerous models over the years and I can remember only one failing. I tend to use the best and most reliable servos that I can afford . I have models with buried servos on airbrakes, rudders and on the elevator of my Dart. Seven or so years on they still operate without a problem.
Brian. :)

Re: SF33 1/6 scale

Posted: 13 Jan 2019, 00:33
by chris williams
Looks like Brian's got immunity from Murphy's Law... :D

Also...7 years? That's still brand new!

Re: SF33 1/6 scale

Posted: 13 Jan 2019, 08:24
by Trevor
Like Brian, I usually just bury wing servos. I rationalise my laziness by the argument that if you do have to cut your way in to replace one, the resulting patch is normally no more visible than a hatch would have been anyway, so why disfigure the aircraft with all those hatches beforehand? It does pay to take a few photos of the installation before covering it up though, so you can work out where to make the incision when the servo fails 20 years later!

Whichever way you do it, Murphy's law dictates that the servo will be out of production by the time it fails so you'll probably have to replace two of them and hack the mounting about - hatch or no hatch.

Re: SF33 1/6 scale

Posted: 13 Jan 2019, 20:28
by Noël Rumers
Hi,
I do the same, never had a problem...
I know Murphy too!
But I know where to cut and that is ifffiiiiffff....
Noël

Re: SF33 1/6 scale

Posted: 13 Jan 2019, 20:43
by Peter Balcombe
There you go then.
I think I will definitely go for the buried servos & smooth finish option, keeping a sharp scalpel handy in case of a problem.

Re: SF33 1/6 scale

Posted: 18 Jan 2019, 16:44
by Peter Balcombe
Lower sheeting now in place - with spoiler servo buried!
Balsa LE strip has since been fitted together with aileron hinge area sheet.
Next job will be to complete sanding of the sheeting around the aileron before cutting this free.
Lower sheeting added
Lower sheeting added

Re: SF33 1/6 scale

Posted: 16 Apr 2019, 11:57
by Tonyw51
G'day Peter,

How is the build going?

Cheers,
Tony

Re: SF33 1/6 scale

Posted: 16 Apr 2019, 12:14
by Peter Balcombe
No more progress yet I’m afraid as I have been diverted by the SG38 , PIK20 rebuild and other projects.
Hope to get back onto it soon though.

Re: SF33 1/6 scale

Posted: 18 Apr 2019, 14:11
by Tonyw51
Yes I know the problem, I have just started building a bass guitar for my son which is receiving the attention and enthusiastic priority of my wife. I think modeling is on the back burner for a couple of weeks

Re: SF33 1/6 scale

Posted: 20 May 2019, 10:50
by Peter Balcombe
Just got back to the SF33 build, so have started on the LH wing.
The build is pretty much as for the 1st wing & I am currently notching the ribs for the aileron spars.
Once the upper hinge spar spar glue has set, it will be time to cut notches for the top aileron LE spar.
LH Wing started
LH Wing started

Re: SF33 1/6 scale

Posted: 20 May 2019, 19:11
by Peter Balcombe
And now with both wings fitted to fuselage to epoxy the carbon main joiner tube in place.
Main Fuz joiner install
Main Fuz joiner install

Re: SF33 1/6 scale

Posted: 20 May 2019, 23:39
by Tonyw51
G'day Peter, Good to see you back on this project. Could I ask you to put in a feed of detailed photos on the wing construction. Thanks, Tony

Re: SF33 1/6 scale

Posted: 21 May 2019, 10:50
by Peter Balcombe
Hi Tony.
Please look at the earlier part of this thread for photos taken during the 1st wing build, but I will add a few more as I put the 2nd one together.

As mentioned before, this plan is hand drawn and suffers from several inconsistencies & what I consider to be missing build info.
Thus it is not a good 'first build' model, but looks as if it can be made into a nice model with a little care and ingenuity.

As stated previously, I started my wing construction y laying down a pre-spliced lower main spar over the plan, spaced off the building board using 1/16" balsa spacers to simulate the bottom sheeting to be applied later. I also laid down a 1/4" wide strip of 1/16" balsa immediately forward of the TE section upon which to lay the rear of each rib.
Each rib can now be glued onto the main spar and TE strip after fettling to adjust the spar slot width and also the front edge to ensure a straight line at the front for fitting the dummy LE strip next. The most important ribs to get sorted out before assembly are the ply ones (R1 & R3), a these are harder to adjust in situ. I filled the spaces between each rib at the TE with balsa strip, sanded down flush with the tops of the ribs later.
Once a further 1/16" balsa strip is added, this gives a solid TE structure to fit the TE onto.

With all ribs in position (remember to angle the root rib & to fit a washout wedge under the TE from inner end of aileron), the dummy LE can be butt-jointed to each rib and then the 1/8" balsa root corner gussets added.

A length of 8mm ID carbon tube can now be inserted trough the holes in the root ribs & epoxied into position, followed by addition of the top spar (after fettling the rib slots to suit).

Now add the spruce top drag spar and the additional wedge behind the main spar over the joiner tube. The ribs are only cut for a wedge spar out to R4, but I took mine out to the drag spar intersection to give support for the webs to be fitted out to there. (I also added a cap to the joiner tube and filled the void between joiner tube & top/bottom spars/edges with hardwood/epoxy later, before the area was sealed with the webs).

There are no pre-cut notches for the aileron hinge & LE spars, this this has to be done manually. Bearing in mind the slimness of the ribs at this point, I decided to only fit the upper spars until the area had been sheeted in order to provide support whilst the lower notches were cut later. Hence i measured the spar locations & carefully notched & cut the ribs for the upper hinge spar only, fitted the spar & once secure, cut & fitted the 2 aileron end riblets, tack gluing these in place whilst spaced off the full ribs. Then the intermediate ribs can be very carefully notched and the top aileron LE spar fitted.

At this point, you are about ready to apply the upper sheeting once the dummy LE has been sanded flush to the top of the ribs & other areas prepared.
The rear incidence tube could be fitted before the top sheeting is added, but this can be easily done later before the lower sheeting is fitted. Holes are provide in the root ribs but when fitting, ensure that the incidence rod is parallel to a fitted main joiner in both front-rear & plan views.
The rear tubes could be also fitted using the fuselage as a iig as a single rod is used for each of the main joiner & rear incidence alignments.

A few detailed photos below may also be of use.
LH wing root spars
LH wing root spars
LH wing main joiner tube
LH wing main joiner tube
LH Ail hinge spar
LH Ail hinge spar
LH Ail spars
LH Ail spars
LH wing TE layers
LH wing TE layers

Re: SF33 1/6 scale

Posted: 23 May 2019, 10:04
by Tonyw51
G'day Peter,
Thank you for your post 21 May. You are so right with regards your comments about "first build". However, I am slowly muddling my way through and having a great deal of enjoyment in the process.

I really do appreciate your comments and instructions, they are a great help and confirm a great deal of what I have read into the plans, which is really comforting.

As a side, I was originally brought up using imperial measures, but when I started to play with European and Japanese motor bikes I built my workshop to metric and that was 40 years ago. Fortunately I still have fluency in "Imperial".

Cheers and thanks,

Tony.

Re: SF33 1/6 scale

Posted: 27 May 2019, 20:04
by Peter Balcombe
Tony, we have to be fluent in both Imperial & metric in the UK :?

Moving swiftly on ... Once the top D box skin has been put on (with washout wedge in place), the rear edge of the balsa sandwich at the back of the wing ribs can now be straightened as required to fit the balsa TE stock.
At the root end, I now add the underside drag spar and joiner area sub spars to match those on the topside.
The front spar webs can be put in place over the first few rib bays & then the wing stood on its dummy LE to epoxy spruce infill around the joiner tube & firmly bond the tube to the main spars.
Once that has been done, the remaining spar webs can be added, including those behind the drag spar.

With both wing structures available I have also installed the rear incidence joiner tube into the fuselage and the 2nd wing, temporarily setting everything up with the fuselage to make sure that everything lines up & will subsequently rig easily.
Note; As far as I can see, the forward wing retention hook has to be fitted further forward of that shown on the plan due to a significant cable access hole forward of the main joiner. Moving it forward between 6-10mm should work.
Main joiner support
Main joiner support
Root end webs in place
Root end webs in place

Re: SF33 1/6 scale

Posted: 27 May 2019, 22:29
by Peter Balcombe
Front hook centre has been placed 30mm behind front of dummy LE, so 36mm behind LE at the root (which puts the rear edge of the doubler at the forward edge of the laser cut cable hole). I used 1/2”x1/4” Spruce strip doublers glued to inside of the root rib at the attachment points & will probably screw in small hooks at these points for use with elastic bands or similar through the fuselage.
Note that the rear attachment is directly beneath my rudder/elevator servos, so the band will need to be fished through each time, or left attached to pegs each side to ease rigging :o

Re: SF33 1/6 scale

Posted: 28 May 2019, 08:01
by Tonyw51
Hi Peter,
Yes I can see the rear hook will be well covered by the servo tray. I have a PA-22 model that uses a grub screw through the wing spar tube and it seems to work quite well. Maybe the same could happen in the rear incidence tube. Something to consider, I also shall consider a peg/hook mounted on a the bulkhead.

Looking at the vertical stabiliser I am not sure of the mounting strength of gluing it to the 6mm plate in the fuse. What have you done there?

What type of hinges are you using for the control surfaces? I am considering the hinged Du-Bro.

Cheers,
Tony

Re: SF33 1/6 scale

Posted: 28 May 2019, 08:56
by Peter Balcombe
Tony,
Tail feathers are made but not yet attached until they have been covered.
I will almost certainly glue them on, making sure there is good clear contact between the wood on each side (covering overlaps removed as required).
(I have used this method on a 1/4 scale Mick Reeves Fournier RF4, so not a problem at 1/6 scale as long as you have wood/wood contact).

I have used Mylar strip hinges (approx 3/8” wide) on the tailplane & rudder (have previously also used this on up to 1/4 scale). I will also use this method on the ailerons to provide a basic hinge, using a full length Blenderm type tape gap seal.
I would have thought Du-bro hinges will be rather prominent & not really necessary for a smaller model of this type.

Re: SF33 1/6 scale

Posted: 05 Jun 2019, 03:09
by Tonyw51
Hi Peter,
Thanks for your comments, I just feel uncomfortable with the lack of bracing from the attach point through the butt joints. I have covered the the Fin and Horizontal Stabiliser with 0.5mm ply which has added very little weight but it has stiffened the parts and spread the loads. See attached

Image

I am happy with the Du-Bro hinges which have fitted quite well.

Looking forward to your updates.

Cheers,
Tony
IMG_2077.jpg

Re: SF33 1/6 scale

Posted: 05 Jun 2019, 15:17
by Peter Balcombe
Just made up a couple of cowl cheeks.
Only a plan view of the cheeks showing internal hollowing out is shown on the plan, so have plumped for 1” height in side view with freehand curves. Balsa block is roughed out then sanded to give outer curves.

I will now Glass the cheeks to give some strength before hollowing out & fixing in place (centreline on the hatch edge!)
(The fuselage will also be glassed to provide a painting surface rather than try to apply film).
Cowl cheek blanks
Cowl cheek blanks

Re: SF33 1/6 scale

Posted: 19 Jun 2019, 21:29
by Peter Balcombe
The 2nd wing is now also about ready for covering although aileron horns still be made & fitted.
Meanwhile, I have applied 2 layers of lightweight glass cloth to the cowl cheeks, sanded smooth & then waxed prior to making a backup plaster mould before digging out the majority of the balsa from the resultant shells - just in case ;)
Once I have cut a nose aperture on each, the cheeks will be epoxied to the cowl hatch & then the relevant part of the hatch sides cut away to allow cooling air to be directed into the motor/ESC.

The fuselage has also been glassed & given an initial dust with primer to see how much further work is required prior to painting.
Cowl cheeks1.jpg
Cowl cheeks2.jpg

Re: SF33 1/6 scale

Posted: 22 Jun 2019, 13:38
by Peter Balcombe
With removable motor access hatch fixing sorted using pegs and magnets, the cowl cheeks were epoxied to the hatch so that they straddled the join line.
A liitle bit of joint reinforcement later, the cheeks can be used as finger holds whilst removing the hatch.
With the fuselage glassed & rubbed back, it's nearly ready for painting.
Motor access
Motor access
Hatch with cheeks
Hatch with cheeks
IMG_1846.jpg
IMG_1847.jpg

Re: SF33 1/6 scale

Posted: 03 Jul 2019, 13:03
by Peter Balcombe
Fuselage primed and then given a couple of coats of SigMarine gloss white, cockpit given a (short) pilot figure and canopy glued on with Canopy glue.
Tail feathers also covered using HK covering film (with slightly contrasting colours/paterns top & bottom to help with model orientation).

The wings have also had the aileron servo & spoiler installed prior to covering with the same HK heatshrink film.
The outrigger legs have also be fitted after drilling a locating hole in the spruce subspar at the inboard end & then removing a narrow strip of the balsa skin to accept the leg after covering. The outboard end of the legs are retained by small plates screwed into the hardwood sub-spar/main spar.
Fuselage parts2.jpg
Fuselage parts3.jpg
IMG_1856.jpg
Outrigger leg.jpg

Re: SF33 1/6 scale

Posted: 03 Jul 2019, 18:39
by Peter Balcombe
With the tail feathers glued in place, its time for the first overall assembly.
Power train and wheels to fit, but nearly there now.
First assembly
First assembly

Re: SF33 1/6 scale

Posted: 05 Jul 2019, 11:54
by Tonyw51
G’day Peter
That’s looking good. I am interested in the glassing of the fuselage, what weight and cut did you use? I figure that is the way to go as the fuselage is very light in structure and a laminate of glass would be a very beneficial move

Cheers
Tony

Re: SF33 1/6 scale

Posted: 05 Jul 2019, 15:33
by Peter Balcombe
Hi Tony,
I used the standard 25gsm lightweight wing skinning variety, with just a single layer, essentially done as 2 sides with overlap along top & bottom centres.
Resin applied sparingly over the cloth with a brush, making sure that everything was fully wetted out.
Rubbed back before applying a dust coat of primer to help see & correct the worst imperfections (particularly around wing roots) before brushing on a couple of coats of Sigmarine white.

Re: SF33 1/6 scale

Posted: 09 Jul 2019, 23:04
by Peter Balcombe
Power train now installed.
I am using an old Dualsky XM3548 brushless motor with XC4018 ESC supplied by a 3S 2200mAH Lipo.
(There is plenty of space to fit a larger capacity battery if needed).
With a fixed 2 blade 9x6 Master Airscrew prop, this combination gives just over 300w on the wattmeter, with just over 30A at full throttle.
Max motor efficiency current is 35A, so a little more is available, but max current is 40A.

With the model (currently still less it’s tailwheel assembly & Rx) balanced (2200 battery fully forward), the overall weight comes in at 1.8Kg (4lbs), including about 200g of lead hot glued to the bottom of the motor bay.

Currently trying to find a tailwheel assembly with a bracket small enough the match the fuselage rear end, which can also be fitted with a 15mm tailwheel. (Cliff May need to 3D print a slightly smaller version of the Commercial unit I have!)
Also need to find & fit a couple of small outrigger wheels - otherwise it’s about ready to commit to aviation once a receiver has been fitted & set up.

Re: SF33 1/6 scale

Posted: 04 Jul 2020, 12:19
by StephenB
Peter, did you resolve the wheel issues and get this airborne? I ask as I'm thinking of having a crack at one, it's a handy size for ease of transport and rigging so I'd be interested to know how it flies on your power set-up.

Re: SF33 1/6 scale

Posted: 04 Jul 2020, 13:34
by Peter Balcombe
Hi Stephen,
Yes, the wheels were sorted (using commercial types as far as I can remember & Cliff Evans took delivery.
I am pretty sure that it was flown ok by Cliff last year, but will wait for him to comment on the flying aspects.
Peter

Re: SF33 1/6 scale

Posted: 04 Jul 2020, 13:53
by Cliff Evans
I have not managed to get it to take off from the ground, there is not enough prop clearance. I just hand launch. Flys well no vices at all.

Re: SF33 1/6 scale

Posted: 04 Jul 2020, 14:50
by StephenB
Thanks Peter and Cliff - that answered another question as to whether it would r.o.g. I thought prop clearance may be an issue. How do the outriggers fare - are they vulnerable on landing??

Re: SF33 1/6 scale

Posted: 04 Jul 2020, 21:45
by Cliff Evans
Really depends on how long the grass is! Not really had any problems with them.

Re: SF33 1/6 scale

Posted: 12 Jul 2020, 18:38
by IanT-White
Peter , I have a two thirds scale SF33 ,which flies really well , with a King 190 twin , with onboard electric starter takes off very easily and climbs 6 to 7 metres second
Occasionally the outriders bend if they catch a tuft but easily straightened ,115 lbs
Good luck with your flights
Ian Turney-White

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 13:39
by StephenB
No mention of control throws on Cliff's plan, what did you dial in Peter?

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 15:30
by Peter Balcombe
Stephen, I cannot remember exactly, as I passed the model over to Cliff with servos linked up & checked using a servo tester, but no receiver in place, leaving him to set up the Rx and actual control throws.
I would have given Cliff something like as much rudder as I could reasonably get mechanically say 3/4” or more each way.
Elevators would have been about 1/4-3/8” each way & ailerons probably something like 3/8” up & 3/16” or so down.
(I basically set up what looked enough travel & left it up to Cliff to use what he thought necessary from there)

I expect that Cliff will be along soon to advise what he actually used.

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 17:29
by Cliff Evans
rudder 3/4” each way.
Elevator 3/8" each way
Aileronse 3/8” up 3/16” down

Is exactly as mine is set up 65% expo on elevator.

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 17:35
by Peter Balcombe
Cliff Evans wrote: 12 Oct 2020, 17:29 rudder 3/4” each way.
Elevator 3/8" each way
Aileronse 3/8” up 3/16” down
Wow, that was a good guess 8-)

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 20:45
by StephenB
Many thanks Peter and Cliff, a little less than I had "estimated", so probably saved a fraught first flight experience!

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 20:47
by Cliff Evans
The elevator is still quite lively!

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 22:21
by StephenB
Cliff Evans wrote: 12 Oct 2020, 20:47 The elevator is still quite lively!
Noted!

Re: SF33 1/6 scale

Posted: 12 Oct 2020, 23:36
by Tonyw51
G'day Peter and Hi to Stephen & Cliff,

Great to see your post on control throws as I had been mulling over that recently. It is all somewhat academic at this stage as we are still in lock-down and the field has been closed since June. I have not had the opportunity to take the model to my local model shop to discuss fit up of a couple of final items and frustration is starting to set in. Anyway, I have attached a couple of photos of my example. This is my first attempt at a scratch build and I am quite pleased with the result. (My second scratch build is a "Wood Pecker" out of RCM&E November 2017, photo attached of the maiden flight. The field was closed again in the following week).

Cheers,
Tony W
IMG_2402.jpeg
IMG_2197.jpeg
IMG_2403.jpeg

Re: SF33 1/6 scale

Posted: 13 Oct 2020, 08:42
by Peter Balcombe
Looks very nice Tony.
I hope all goes ok when you get the chance for the maiden.
Peter

Re: SF33 1/6 scale

Posted: 13 Oct 2020, 09:16
by Cliff Evans
Looks good Tony.

Re: SF33 1/6 scale

Posted: 13 Oct 2020, 09:30
by StephenB
Nice job on the SF33 Tony, very striking colour scheme. Let us know how the maiden goes.

Re: SF33 1/6 scale

Posted: 14 Oct 2020, 01:18
by Tonyw51
Thanks. Yes I shall report the event just as soon as it can happen.

Cheers

Re: SF33 1/6 scale

Posted: 25 Nov 2020, 10:04
by Tonyw51
Hi styx2020,
I went to OfficeWorks here in Melbourne and they were able to do the job for me. I had them do 2 copies of both original and mirror so I could cut and hack.

I have had a couple of sessions at the paddock to get my fingers and brain acting together again and am now waiting on the weather to improve for the SF33 maiden post our pandemic lockdown.
Cheers,
Tonyw51

Re: SF33 1/6 scale

Posted: 14 Jan 2021, 08:08
by StephenB
I've made some progress on mine, albeit slow progress.

I'm finding that smaller models don't necessarily equate to less building time, smaller parts need careful handling and the construction is a lot more "fiddly", this model being a case in point and where anomalies and missing information also lead to confusion. At least on my part!

The build log courtesy of Peter has been a godsend and I've used it as my reference, his idea of reinforcing the trailing edge is a clever and very useful modification. The strange triangular sub spar arrangement around the wing root is hard work and seems overly complicated when a single longer tapered sub spar may have done the job, I'm sticking to the plan but it's heavy going.

Some of the specified material sizes ar also a bit odd, for instance the spar webbing is specified as 1mm ply front and back full length of the wing - overkill? I have either 0.8mm or 1.5mm available to me so will use 0.8mm.

Here's where I'm at now:

Fuselage and tail feathers more or less completed:
IMG_0822.jpeg

First wing under construction:
IMG_0821.jpeg

Re: SF33 1/6 scale

Posted: 14 Jan 2021, 09:11
by Peter Balcombe
Well done Stephen, its looking good :)
Don’t worry about being too precious about wood sizes. I use the nearest equivalent of a similar wood type.
So for 1mm, use 0.8mm etc.
I’m sure that back in Cliff Charlesworth’s day, he would have used imperial sizes anyway!
Peter

Re: SF33 1/6 scale

Posted: 20 Mar 2021, 15:51
by StephenB
Finally finished mine, for a smallish model it seemed to take a long time!

Fuselage covered in lightweight glass cloth and Eze-Kote, brush painted with two coats of Oraclour for the white and red. Flying surfaces covered in Easycoat seconds.

Constructed as per the plan but incorporating Peters building mods, air brakes and outrunner legs/wheels fitted, I opted to leave off the tiny tailwheel due to the less than billiard table smoothness of my landing strip and fitted a tailskid to protect the rudder. With 200g or so of lead in the nose she comes out at a smidgeon under 1900g

Motor is an Overlander Tornado 1250Kv driving an Aeronaut CamCarbon 9.5 x 6 which my wattmeter tells me is putting out 250W @30A, this coincides with ecalc. Perhaps a 10 x 6 prop would be a good idea to give me a little more margin on the power.


IMG_0864.jpeg

IMG_0857.jpeg

IMG_0861.jpeg

Re: SF33 1/6 scale

Posted: 12 Apr 2021, 11:39
by Robcrad
Hi everyone,
I too am nearly finished building one of these, hoping it will be a gentle Sunday afternoon flyer, one question I have is how much elevator compensation are people using with the spoilers?
Once I get the fuz painted I will upload a couple of pics.
I would like to thank all the contributor's to this thread, it has made my build so much easier.

Thanks
Regards

Rob

Re: SF33 1/6 scale

Posted: 12 Apr 2021, 13:35
by Cliff Evans
I found about 6mm up and down was more than enough on the elevator. Air brakes do not make much difference at all!

Re: SF33 1/6 scale

Posted: 13 Apr 2021, 11:19
by Robcrad
Thanks Cliff

Re: SF33 1/6 scale

Posted: 14 Apr 2021, 17:31
by StephenB
Cliff Evans wrote: 12 Apr 2021, 13:35 Air brakes do not make much difference at all!
Now he tells us :lol:

I could have saved the time, effort and two servos!

Re: SF33 1/6 scale

Posted: 15 Apr 2021, 08:54
by Barry_Cole
I may be wrong here, but I don't think he meant that the airbrakes do not make any difference.

I think he meant that operation of the airbrakes did not need any elevator compensation..

But maybe you all knew that??

8-) 8-) 8-) 8-)

BC

Re: SF33 1/6 scale

Posted: 15 Apr 2021, 09:15
by Cliff Evans
Barry_Cole wrote: 15 Apr 2021, 08:54 I may be wrong here, but I don't think he meant that the airbrakes do not make any difference.

I think he meant that operation of the airbrakes did not need any elevator compensation..

But maybe you all knew that??

8-) 8-) 8-) 8-)

BC
Thank you Barry!

Re: SF33 1/6 scale

Posted: 22 Apr 2021, 15:46
by Robcrad
Hi everyone,
well almost ready for the maiden of my SF33, few tweaks and good to go,
just wanted to thank everyone on this thread, made my build much easier!

Regards

Rob
SF33 2.jpg
SF33.jpg

Re: SF33 1/6 scale - Reply to Peter regarding plans inaccuracies...

Posted: 03 Aug 2021, 16:56
by Steve Naidamast
Peter...

I have been working on my SF33 for several weeks now and have found the same issues you described in your previous email of May 21, regarding the inaccuracies you found with the plans.

Though I have built a number of kits in the past, this is my first build of a short-kit. And being here in the States, I had to do a bit of work to get as accurate a set of measurement conversions to the Imperial standard as I could.

So far, I have been getting my left-wing set up with a number of the ribs ready for gluing but I am waiting until I have all of them fitted.

Working on the build this morning, I noticed that the nearer to the root I went with fitting the ribs, the more level their fronts became with my leading edge. Though I double checked the height that the leading edge should be, it appears that it may be somewhat low as a result of what I have seen with the inner ribs.

As a result, I will probably add a Balsa strip on top of the composite leading edge I already have (the Balsa backing has already been glued successfully). This additional height should allow all of the ribs to have their sheeting fall flush with the leading edge after sanding it down slightly into the rounded edge the LE should have.

Thank you for your very informative notes on this build. I thought it was me, since this is my first short-kit build, when I noticed how poorly everything appeared against the plans forcing me to do a lot of light sanding to ensure that everything at least fit within the expected boundaries that the plans depicted.

Writing to Cliff Charlesworth on this issue with the wing ribs, he suggested what I had to do in any case, sand where needed...

Steve Naidamast
New York, USA

Re: SF33 1/6 scale

Posted: 03 Aug 2021, 17:36
by Cliff Evans
Steve, although my name is Cliff and I supply the Cliff Charlesworth plans and short kits I am not Mr Charlesworth (I wish)! Cliff passed away some years ago now and left me all of his plans. Sorry for the confusion. Cliff and myself were very good friends for many years. Unfortunately there are inaccuracies in all hand drawn plans and also when printing plans there can be significant differences in the scales printed, this will depend on a number of factors, humidity for one and even software used for printing can make a difference.

Re: SF33 1/6 scale

Posted: 03 Aug 2021, 18:10
by Peter Balcombe
Steve,
As Cliff has already mentioned, this plan is one of the original hand drawn designs from the Cliff Charlesworth range, so it is not unusual to have to send things here & there to achieve good fits.
The ribs are a particular area where sanding across several ribs is needed to achieve a smooth line.
Although CNC designs are better, you are still likely to have a small difference between the printed plan & the parts due to changes in the paper.
I’m afraid nothing is perfect, so ‘fettling’ or adjustment to some degree as you go along is often part of the normal build process ;)
Anyway, the model does come out to look nice & flies well once finished.
Peter

Re: SF33 1/6 scale

Posted: 03 Aug 2021, 18:51
by Steve Naidamast
Cliff & Peter...

Thank you both for your updates.

I am sorry to hear that Cliff Charlesworth passed away.

I am not taking the inaccuracies with the plans as a negative but instead as a challenge. I believe I am a good enough builder to make the adjustments where needed. I believe in the idea of "add more and sand down", though I did sand two of my ribs so far a little short in the rear. However, some Balsa filler or 1/16 inch wood should fill in the gaps quite nicely.

I am writing up my own documentation that details my work on my project. I have two documents already produced and expect to create a third one after I complete fitting all of the wing-ribs on my left wing.

I will be forwarding a question regarding the upper sheeting on the wings but I need to finish my rib fittings first so I can take a few pictures of the wing to clarify what I will be asking.

Thank you again for your notes... :-)

Steve Naidamast
New York, USA

Re: SF33 1/6 scale

Posted: 06 Aug 2021, 22:10
by Peter Balcombe
Steve,
With regard to the wing ribs & false LE, I would suggest that you assume the CNC rib profiles are correct and fit the false LE so that it can get sanded to suit the rib profiles along the wing.
I would have done this, fitting an oversize false LE & sanding back to suit the ribs along the span, then fitting the top skins to sit on all rib edges & false LE.
(If the false LE was CNC cut & a little undersize then don’t worry as long as the skins fit well to the ribs & there is a minimal gap between false LE & skins. The LE will bond to the front edge of the skins & false LE if you use an aliphatic (or similar) glue which fills small gaps & dries hard enough to sand well to a smooth surface.)
With the top skin in place, largely locking in the wing D box profile, I would have turned over the wing, removed any rib building tabs & sanded back the false LE to the rib profile before adding the lower skin.

I find that the false LE & false TE profiles given by CNC design programs tend to err on the large side, so generally need sanding back to suit the rib profile.
Once both skins are on, they are sanded back flush with the false LE before fitting & profiling the LE.
Hope this helps.
Peter

Re: SF33 1/6 scale

Posted: 06 Aug 2021, 23:11
by Steve Naidamast
Hi Peter.

Thank you very much for your reply and its informative notes.

I completely understand what you are saying by providing for an oversized Leading-Edge.

So my question then becomes, with what my email to Cliff described, would you simply add to the height of the existing Leading-Edge composite that I have already created (which turns out to not be high enough to accommodate the overlay sheeting comfortably, which is what my own solution was, or would you simply develop a new Leading-Edge composite altogether by simply purchasing new wood with greater measurements for the height?

Steve

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 09:22
by Peter Balcombe
Steve,
If you haven’t glued anything yet, then I suggest increasing the width of your wood to make a better job. (You can always butt glue another narrow strip to your existing false LE & LE strips to build them up before glueing to the ribs).

Cliff has reminded me that the SF33 design doesn’t have building tabs, so the wing is built up on the lower spar, flat on the building board with tip TE washout taper wedge inserted as shown on the plan to get the necessary tip twist. Note that although it isn’t shown in the rib section sketches, the plan view shows what looks like a 1/16” thick false LE with thicker LE strip (1/4”) on the front. (It wont matter much if you end up with 5/16” total instead of 1/4”, but a plan measurement would identify whether it’s 1/4” total, so 1/16” false LE & 3/16” LE).

Anyway,
I suggest that you initially fit just the 1/16” false LE to the front of the ribs (widening it if neccessary & positioning it vertically to make contact with the whole of the front of each rib). Note that a 0 to 5mm washout taper wedge should be fitted at the tip end TE as shown on the plan, which will cause the tip end LE to rotate downwards.
The LE strip is fitted only after both skins are in place so that it bonds to the front of both skins and can be profiled to the external wing thickness.

With the false LE sanded as necessary to get flush with the ribs, the top skin can be fitted, ensuring that it sits down onto the false LE all the way along. (It’s a good idea to use Aliphatic glue as this dries hard, but sands well, unlike Cyano which is harder & more difficult to sand back to balsa without taking off unwanted balsa! White wood glue is ok, but leave a “stringy” joint which is difficult to sand cleanly.
(I tend to use Aliphatic as my general glue for all wood builds, plus epoxy for high strength areas only. This makes joint sanding much easier.

With the top skin applied & carefully sanded back to the front of the false LE, turn the wing over, prepare the underside, fit wing retention blocks, cables, spoiler, servo hatch frames etc. before fitting lower skin.
Then sand off front of lower skin back to false LE to give a clean face with edges of skins top & bottom to fit the LE strip. The LE strip must be wide enough to cover front of top & bottom skins. Fix this with Aliphatic glue & then sand down flush with skins & to LE profile.

I hope this helps, but don’t hesitate to query if unclear.
Another SF33 was built by Stephen in Hungary after my build, so Stephen may add his thoughts if he sees this thread.

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 14:32
by Peter Balcombe
Steve,
I you haven't done so already, check out this build thread around Nov 2018 as this has photos of my wing build, showing a just a false LE fitted to front of ribs.
viewtopic.php?p=20644#p20644

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 17:09
by Steve Naidamast
Hi Peter...

Thank you again for your latest notes.

As to the Leading-Edge and its backing (the False-LE), I have already set that up and have the backing already glued to the Leading-Edge.

The Leading-Edge itself is 1/4 inch in width(thickness) and 1/2 inch in height. The False-LE is 1/16 inch with the same height as the Leading-Edge.

What I need to do is raise the height of the False-LE and the Leading-Edge so that when I apply the wing's overlay sheeting, it falls slightly below the composite Leading-Edge so that I can sand down the Leading-Edge so that it is flush with the overly sheeting.

I believe I have settled on adding a top-strip of about 1/8 inch as a heightner to the Leading-Edge so that the composite Leading-Edge will now be composed of three pieces instead of 2; the Leading-Edge, the False-LE(backing), and the top-strip that will add some height to the existing composite Leading-Edge

The attached JPG image shows my left wing layout as of now (wing ribs are not glued yet). You can just see the seam of my False-LE and Leading-Edge, which are currently glued together.

Steve
IMG_0683.JPG

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 18:04
by Peter Balcombe
Ok Steve, you should be able to get it to work - as long as you can butt the skins hard up against the rear face of the composite LE (ideally they will need a slight chamfer to account for the <90 degree angle with respect to the LE face.)
The other thing you need to do is make sure that the skin is down onto the front of the ribs & in a straight line between each one. (You could pin a length of strip Balsa placed along the very front of the skin into the composite LE, but you will need to stop glue sticking to this piece, say by putting a strip of cellotape along it to act as a release layer.)

The above is a reason why the false LE is added separately, before the main LE. ;)
Peter

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 19:16
by Steve Naidamast
Peter...

Yes, I believe I can get everything to work the way I have my layout set up currently.

And working over some wax paper on top of each rib should not be an issue.

Your suggestion of placing a 1/4-inch or 1/2-inch strip of 1/16-inch strip of Balsa as the front-most piece of the overly skin is a very good idea. This way I can manage more easily the straightness of the entire component across the length of all the ribs. I'll just have to sand a side very gently to create a slight angle so that the piece sits cleanly against the composite Leading-Edge.

The only thing I did not understand was your following statement... "The other thing you need to do is make sure that the skin is down onto the front of the ribs & in a straight line between each one."

My composite Leading-Edge is straight now. I would assume that any piece being fitted against it on top of the ribs would be straight as well.

I also have not sanded any of the ribs' tops; just the fronts, the rears, and the main spar notches so I could fit them cleanly within the plan outlines.

Steve

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 19:37
by Peter Balcombe
Stephen,
What I meant was that although your skin will butt up against your straight composite LE in the plan view, you don’t want the skins dipping or bulging in the vertical plane between ribs.
The length of strip Balsa will help keep the skin from bulging upwards as well as ensuring it is held down against the rib tops, but won’t stop any tendency to droop between them.
However, if there are no local pressure points forcing the skin away from a straight line, all should be well.
Peter

Re: SF33 1/6 scale

Posted: 07 Aug 2021, 19:56
by Steve Naidamast
Peter...

OK, I understand what you mean now.

I'll make sure that the sheeting does not experience any dips or bulges. However 1/16-inch sheeting should not be susceptible to such issues.

At worst, I could cut a small forward notch in the ribs and lay down an upper mini-spar to ensure that no dips occur.

Thank you so much for all your help with this.

Steve

Re: SF33 1/6 scale

Posted: 15 Aug 2021, 17:22
by Steve Naidamast
Hi Peter...

I have sanded down my composite Leading Edge and have begun the gluing of my wing-ribs. I tend to begin in the center of the wing, working to the wing-tip first before going towards the root.

I have a question about a statement you made regarding a strip of balsa right behind the Leading Edge. What did you mean by the following? ...
>>>
You could pin a length of strip Balsa placed along the very front of the skin into the composite LE, but you will need to stop glue sticking to this piece, say by putting a strip of cellotape along it to act as a release layer.
<<<

Thank you...

Steve

Re: SF33 1/6 scale

Posted: 15 Aug 2021, 18:16
by Peter Balcombe
Does that mean that it all looks good now Steve?
Peter

Re: SF33 1/6 scale

Posted: 16 Aug 2021, 17:38
by Steve Naidamast
So far Peter, the gluing appears to be going well. I am going to do some more this afternoon.

Looking at the bottom front part of the wing ribs, it appears an additional bottom piece of stripping will have to be added to the Leading Edge in order that the skinning of the bottom part of the wing will meet the bottom part of the Leading Edge properly.

I have received an order of Balsa stripping that should take care of all of it.

As far as the skinning goes, I was thinking of using 1 inch wide/ 1/16 inch thick stripping. Though this will incur slightly more gluing, it will avoid any depressions or bubbling in the wood.

As I had mentioned in my last email, I did not understand what you meant by the following statement you made in a previous email to me...
>>>
You could pin a length of strip Balsa placed along the very front of the skin into the composite LE, but you will need to stop glue sticking to this piece, say by putting a strip of cellotape along it to act as a release layer.

<<<

Could you please clarify.

Thank you...

Steve

Re: SF33 1/6 scale

Posted: 16 Aug 2021, 18:37
by Peter Balcombe
Steve,
What I meant by the comment was:

As I normally just fit the false LE to the ribs & then sand this down flush with the rib front profile before adding the skins, I can fit the skins down onto the ribs and the false LE, overlapping the false LE by a couple of mm. The skin front can also be held down using many strips of masking tape placed around the LE from top to underside.

However, if you have a composite LE (main LE strip already fitted to the false LE, each skin has to be fitted with its front edge butting up against the LE & hopefully also sitting down onto the top of false LE.

My suggestion was to (just after the skin has been put in place against the LE strip) pin a temporary strip of wood along the top front of the skin in order to ensure that the skin stays down against all ribs & flat in between them. The cellotape (or similar) acts as a release layer to make sure the temporary strip can be easily removed again once the glue has dried. (surplus glue may seep upwards through the front joint line & grab the temporary strip!)

Hopefully all is now clear.
Peter

Re: SF33 1/6 scale

Posted: 16 Aug 2021, 19:19
by Steve Naidamast
Peter...

Thank you for your explanations. It is all clear now.

I am being quite careful with my gluing. For example, I have only placed glue on the front of the wing-rib face currently dry only about half way up the rib-face. This way, no glue seepage will occur at the top of rib where the skinning is supposed to lay.

To strengthen the fronts of the wing ribs I am planning on adding triangular strengtheners to each side of the rib front, whereby the strengtheners will be glued to the back of the Leading Edge and to the sides of the rib fronts.

The strengtheners are approximately 1/4 inch on its triangular sides.

Steve

Re: SF33 1/6 scale

Posted: 16 Aug 2021, 21:39
by Peter Balcombe
Steve,
I had assumed that your false LE is butt jointed to the rear of your LE & that you would be fitting/glueing your skin hard up against the straight rear face of the LE in order to get a good bond to ribs, False LE & LE.
Thus glue needs to be in the area of the skin/LE joint & my experience is “ if it can happen, then sure as eggs it will at some point” ;)
Peter

Re: SF33 1/6 scale

Posted: 16 Aug 2021, 23:04
by Steve Naidamast
Peter...

I have been writing my own documentation on my progress with the my build of the SF33.

I have just completed the third document in this series. They are all titled with document numbers. In this case, documents 1 through 3.

I thought you would be interested in reviewing them so I have attached them with this note.

Steve
The Schriebe SF33 Motor Glider - Build Document 2.pdf
(414.82 KiB) Downloaded 100 times

Re: SF33 1/6 scale

Posted: 17 Aug 2021, 09:14
by Peter Balcombe
Hi Steve,
I’ve just read the 1st episode so far, but seem very thorough.

A couple of comments, some of which you are probably already aware, but I mention them just in case …

Although the SF33 was designed & hand drawn by Cliff Charlesworth many years ago, Cliff Charlesworth died at least 5 years ago. Laser Cut Sailplanes is run by Cliff Evans. The text indicates that Cliff Charlesworth/Cliff Evans & LCS are all the same person.

As you mention, the plan doesn’t quite tie up with the laser cut parts in some areas. This due to a number of factors: 1. The accuracy of the original hand drawn design;
2. Variations in the original paper plan copy scanned for digitising.
3. Part cutting accuracy
4.The variations in the printed plan due to paper moisture content (particularly when printed)

Part cutting accuracy will be within a ‘thou’ or so of the CAD drawing , although they do tend to have a cut edge roughness which can prevent sliding fits (particularly on the harder ply part). As you say, this can be solved by a quick rub with sandpaper.
Most errors are largely due to the original plan & printed paper moisture content between original printing & use.

In general, where laser cut parts do not form a fully interlocked structure, I go by the printed plan as you have done (no matter if it is slightly out or not). I find that even with fully CAD designed & large fully interlocking structures (where the assembly is totally driven by the cut parts) there are still significant difference against some printed plans ((say 10mm in 2 metres!). However, note that we are still talking about <1% variation.

With regards to construction, it is much easier to make up your wing structure using just the LE backing as you call it, rather than making a composite structure with the main LE. The LE is generally only fitted once the wing has been skinned top & bottom.
I would recommend the use of Aliphatic glue for general wood bonding as this dries hard, but is very sandable, whereas epoxy is too hard & you will probably end up taking off more surrounding balsa than you intend whilst trying to get any surplus cured epoxy sanded back. I only use 30 minute epoxy for high stress areas such as wing joiner attachment to man spars.

Finally, I tend to buy balsa sheet (4” wide generally) & cut strips as required - thus for the LE backing & LE it is a simple matter to cut a tapered width strip. You will need sheet material for the fuselage sheeting anyway.

At the end of the day, each builder has his own preferences, so the above is certainly not the only way to do it.
It’s what works for you that is the important thing.

Hope these comments are useful.
Peter

Re: SF33 1/6 scale

Posted: 17 Aug 2021, 16:49
by Steve Naidamast
Hi Peter...

Thank you very much for your review. Your notes are very much appreciated.

Since you encapsulated your thoughts so well, I will incorporate them as a Preface by Britain's Senior Builder in the first document. This way, your thoughts will be included as is and a builder who reads my documents will be able to make a choice as to how he or she will proceed.

However, these documents, as you are aware, are my own experiences to date with this project. As a result, I try to detail my own mistakes as well, while providing corrections. This is specifically oriented towards the construction of the Leading-Edge, whereby my mistake was calculating the height incorrectly. I believe I state that in the second document. If not, I will review it again and include this information.

I have also discussed how to correct sanding gaps to the wing-ribs rear-ends if too much sanding is done, leaving a gap between a rib's rear-end and the Trailing Edge.

As to the bottom of the Leading-Edge, there appears to be little room for adding skinning, even though the wing ribs do arc up slightly against the back of the it. These rib upward arcs do not appear to be enough in order to comfortably add skinning Balsa. As a result, an additional strip of Balsa would have to be added and then sanded down to allow for this. I believe this would happen no matter what measurements would have been used with the height of the Leading-Edge.

Again, thank you for taking the time to read my writing...

Steve

Re: SF33 1/6 scale

Posted: 26 Aug 2021, 20:29
by Steve Naidamast
Hi Peter...

I am down to the last 4 wing-ribs that need gluing. These are rib #s 1-4.

My question is that given the requirement to angle the the wing root-rib (rib #1) at an inward angle of approximately 16 degrees to acommodate for the aircraft's wing dihedral, is this inward angling done for both wing root-ribs or just one.

The plans do not make this very clear, in that the requirement is only shown against the left wing.

Thank you...

Steve

Re: SF33 1/6 scale

Posted: 26 Aug 2021, 22:47
by Peter Balcombe
Steve,
Plans often show one wing only (usually Right wing) & you have to reverse print or trace onto the rear of the plan for the other side.
However, as the wings fit onto the fuselage sides on the SF33 (and as is usually the case), you have to make the 2nd wing a mirror image of the first, so yes repeat everything for the other wing, remembering that things are ‘handed’.
Thus for instance, you will find that aileron servos are usually mounted with horns both either on root or tip side, joiners on the root side etc.

I think the ‘dihedral’ you are referring to (if 16 degrees) is actually an angle in plan view at the root due to the fuselage width taper. This is just to make sure the wing roots are flush along the chord with the single piece main wing joiner. The wing dihedral (span-wise angle of the wing relative to the horizontal plane when seen from the front) should only be 2-3 degrees or so, to provide some lateral stability, but still allow the ailerons to provide adequate roll control.
The root rib is slightly angled in the vertical plane to ensure it sits flush with the fuselage given the small wing dihedral. (So the root rib may be angled in both plan view and vertical plane to sit flush with the fuselage)

Note that a trick to remember if you end up with a gap between wing root rib & fuselage, is to make a slightly oversize root rib for each side. Assemble each wing with this extra rib between wing & fuselage & glue it to the wing whilst the fuselage side is flush with the fuselage - leaving a small angled gap between wing & extra rib (ensuring no glue gets to the joiners or fuselage side of the extra rib). When the glue is dry, remove the wing & fill the gap between the original root rib & the extra rib before sanding back flush with the wing surface. The wing should now fit perfectly with no gaps.
Peter

Re: SF33 1/6 scale

Posted: 29 Aug 2021, 16:49
by Steve Naidamast
Hi Peter...

Just to confirm then, angle both wing rib #1s (root ribs) to an inner 16 degree angle?

Thank you...

Steve

Re: SF33 1/6 scale

Posted: 29 Aug 2021, 21:01
by Peter Balcombe
Steve,
You certainly need to do something very similar for both wings, but the essential point is that both wings need to nicely mate with the fuselage when attached by joiner the system, which I think from memory was a 8mm or so carbon main joiner rod forward & probably a 3mm or so rear incidence rod.
If the main joiner isn’t at a right angle to the fuselage centreline, or the fuselage side curvature is not identical, then the wing root angles won’t be identical.

If you have already fixed the main joiner in place (hopefully square to the fuselage centreline & horizontal with the fuselage flat on the table) then temporarily rig the partially built wings to the fuselage & see how each wing looks.
You can always use this dry assembly to see how each root rib needs to be setup to match the fuselage.
Peter

Re: SF33 1/6 scale

Posted: 30 Aug 2021, 16:22
by Steve Naidamast
Peter...

Thank you for confirming the need to angle both wing root ribs.

I have yet to glue the wing root rib to my left wing, which is the one currently being worked on. But all the other ribs are now set so I can begin to add the front and rear rib strengtheners, which should be rather straight forward.

I have never done any rod bending or the like. Are there any services that you know of that can do this for me with the appropriate tubing?

Thank you again...

Steve

Re: SF33 1/6 scale

Posted: 30 Aug 2021, 17:27
by Peter Balcombe
Steve,
What size rod/tube are you talking about.
If you need fairly tight bends in smallish gauge wire, up to 3/32” or so, then holding the wire in a metal vice & tapping the wire slowly around the end of the jaw (hitting fairly close to the bend) should work.

There are a couple of wire benders (Mini & Mighty wire benders), both made by K&S I think. These are intended for cold forming a range of piano wire type rod sizes from small angles to multi turn spring type configurations. I attach a copy of the Mini wire bender instructions, but basically the tool uses a lever to bend wire around a hardened pin.

You can also get a Z bend tool which is essentially a large set of pliers with a Z shaped jaw. (I find the Z a bit big).

Tubes are a bit more tricky as unless you are very careful, bends will cause the tube to kink rather than bend. You can get ‘bending springs’ which you slide over the tube & support it along it length during the bend, but these are normally for larger diameters (like 1/2” copper water pipe). If you want a bend in small brass tube, it’s after better to cut, or at least partially cut, & solder the joint at the required angle.

On the SF33 I don’t think there is much wire bending required other than the outrigger legs & wire pushrods which all use thin piano wire & could be done with a vice/set of pliers.
Peter
Wire Bender instructions.pdf
(4.31 MiB) Downloaded 96 times

Re: SF33 1/6 scale

Posted: 31 Aug 2021, 00:20
by Steve Naidamast
Peter...

I was asking about the two tubes that are installed by both wing roots. Aren't these two tubes supposed to hold metal, bent rods to connect both of the wings together in a way that allows for easier transport through the separation of both wings?

Steve

Re: SF33 1/6 scale

Posted: 31 Aug 2021, 06:44
by Cliff Evans
Steve, the wing joining rods are not meant to be bent as the dihedral is set by the tubes in the wings.

Re: SF33 1/6 scale

Posted: 31 Aug 2021, 09:01
by Peter Balcombe
Steve,
Cliff is correct.
The first few wing ribs nearest the wing root should have holes in them between the main spars (or thereabouts) set at differing heights to set the main joiner & rear incidence tubes at the dihedral angle and set the wings at the correct angle in plan view when the wings are attached using a one-piece straight joiner from one wing, through fuselage into the other wing.
Just cut the joiner rod slightly shorter than the total length of the the fuselage width + 2x the wing tube length (similar with rear incidence rod).
Peter

Re: SF33 1/6 scale

Posted: 01 Sep 2021, 13:02
by Cliff Evans
I do not understand where the 16° angle is coming from!

Re: SF33 1/6 scale

Posted: 01 Sep 2021, 15:03
by Steve Naidamast
Hi Cliff...

The 16 degree angle is shown on the plans for wing-rib #1 or the root-rib, whereby it both root ribs are angled slightly inward towards the wing tips at approximately 16 degree.

From what I could ascertain, this angling of these ribs was to provide the ability for the wings to angle slightly upwards, forming a dihedral when the wings are joined.

This is why I have been asking about the inner tubing to each of the wings. I believe Peter said that these tubes are to acommodate a straight metal rod going into each to bring the wing halves together. However, a straight rod could not fit between the two wing halves and still provide for the slight dihedral in the wings.

I will get a snapshot that part of the plant of the area on the plans I am talking about as far as the angle is concerned...

Steve

Re: SF33 1/6 scale

Posted: 01 Sep 2021, 17:03
by Cliff Evans
Ok, it should be a straight rod as the dihedral is set with the tubes in the wings.

Re: SF33 1/6 scale

Posted: 02 Sep 2021, 11:40
by Robcrad
Steve,
as Cliff says the Joiner is straight, the tube through the fus is straight, the dihedral is formed by the straight wing tubes being fitted lower at the tip end rib and central in the root rib. This results in the wing tip being higher when attached to the fuselage. If you have the short kit from Cliff, this is all done for you and is accurate, I have built one from Cliff's kit it is on page 9 or ten and you can clearly see dihedral.

Rob

Re: SF33 1/6 scale

Posted: 02 Sep 2021, 15:21
by Steve Naidamast
Hi Peter & Cliff...

OK, what I am trying to understand is the following...

As the first attachment shows (wing root ribs angled inward), both wing root ribs (#1) are to be angled inward by approximately 16-degrees. Doing this when bring both wing-halves together will provide the slight dihedral.

The second attachment shows the two inner tubes that are supposed to be inserted in the root area ribs (sample for left wing).

If the two wing halves are to be angled against each other when connected by the rods that are supposed to be inserted into the tubing, how can they then accomodate "straight" rods when such rods would have to bent to a similar angle as the root ribs?

Thank you...

Steve

Re: SF33 1/6 scale

Posted: 02 Sep 2021, 17:46
by Cliff Evans
Can I suggest you try a straight rod between the two wings. Trust me the rod has to be straight! The tubes are angled in the wings to give the dihedral!

Re: SF33 1/6 scale

Posted: 02 Sep 2021, 17:57
by Steve Naidamast
Thank you, Cliff...

I will take your suggestion as soon as I have done some work on the other wing.

Steve

Re: SF33 1/6 scale

Posted: 02 Sep 2021, 21:40
by Trevor
A right angle is 90 degrees so that 84 degrees marked on the plan implies a 6 degree dihedral on each wing, not 16 degrees as you keep saying. That may help you to accept that straight rods will work, as long as the tubes in the wing are angled at 6 degrees.

Re: SF33 1/6 scale

Posted: 03 Sep 2021, 00:09
by Steve Naidamast
Trevor...

What was I thinking? Thank you for the correction.

For some reason I had it in my head that I was relating the angle to 100 degrees and not 90 degrees.

Must be getting old...

Steve

Re: SF33 1/6 scale

Posted: 03 Sep 2021, 06:49
by Robcrad
Steve,
On your first attachment of the root angle, draw a line at 90 deg from the face of the root rib towards the other rib. you will see that the line will be lower on the other ribs compared to the root. If you now draw the line out to the left of the root rib which is through the fuz you can see everything is straight but you have got the required dihedral. flip the wing drawing to the other side of the fuz and wing joiner straight, both wing panels angled up.

Rob

Re: SF33 1/6 scale

Posted: 05 Sep 2021, 16:45
by Steve Naidamast
Rob...

Thank you for your notes.

Though I have built a number of kits over the years, this is my first short-kit, which I believe is coming along quite well. However, though very good at research, trying to under the plans has sometimes been a bit difficult.

But I believe you, Cliff and Peter, have cleared up my confusion over this issue.

Thank you again...

Steve