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1/5 Scale Slingsby T51 Dart 17.

Posted: 04 Jul 2019, 13:00
by B Sharp
Following my recent foray into 1/5 scale with the Mike Trew Skylark 4 I decided to follow up with another build to the same scale. Back in 2012 I built a Dart 17R from the CW plans so I felt that a scale model of a scale model was in order. I remembered that Pat Teakle used to make a Dart 15 kit so I contacted Cliff Evans to see if I could purchase a glass fuselage which could save me some time and effort. At Middle Wallop in June Cliff turned up with the fuselage, but also a nicely drawn plan for a built up wing and packets of pre-cut wing ribs. Better and better, thanks Cliff!
The fuselage is fabricated with glass mat and polyester resin but it has a couple of issues for me. First of all it is a bit short for true scale as the rear fuselage should be 130mm longer for true scale. This will mean that I have to redesign a tailplane which is a bit larger to maintain stability. Secondly there is a front skid moulded into the fuselage which will have to be removed.
The supplied wing plan is fine although I will make changes to suit my own construction methods (Sorry, I cant leave things alone and have to insert my individual preferences). I have also added 3 rib bays to the tip to recreate the 17 metre wing.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 05 Jul 2019, 14:06
by Peter Balcombe
Brian,
If Cliff has passed on the alternative built up wing design that I did, you may be interested to know that the wing section is different from the original foam wings.
I used HQ3.5/13 at the root, changing to HQ3.5/12 at the tip.
Consequently, I jacked up the wing root TE by 1/4” at the rear of the fuselage aperture to maintain a longitudinal dihedral of approx. 2 degrees & try to reduce maiden flight nerves - especially with an AMT back end ;)

Other changes I made to improve flight performance (after speaking to Mr Teakle) was to cut off the top of the tail fin (top of the straight LE) & extend this upwards 2”? before sticking the top back on (original fin then extended rearwards 1/2” to line up). My rudder post length is 11.5”.
I also made a built-up tailplane (open structure behind joiners) + built up rudder to reduce ballast weight requirements.

The resultant model flies very nicely & doesn’t seem to be prone to vicious tip stalling like the original I built many years ago.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 05 Jul 2019, 17:35
by B Sharp
Thanks Peter. I had already worked out the HQ 3.5/13 - 12 change and that was precisely what I had intended to use when I initially planned this build. However I had not checked the fin height against my scale drawing so thanks for the heads- up on that. I had already planned to increase all tail surfaces by 10% due to the shorter moment arm.
I have not used your form of trailing edge construction before but I will give it a go as it would be a shame not to use all these nicely cut ribs. I will however be altering the centre section attachment to the fuselage as I don't fancy four bolts down through the wing. I will also be using servos out in the wing tips for the ailerons as I hate long pushrods and bellcranks.
I hope you don't mind me altering your work as I'm sure that there will be lots of changes as the build progresses.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 05 Jul 2019, 18:07
by Peter Balcombe
Hi Brian,
No problem, do whatever works for you.

I’m not sure how the enlarged (or original) tail compares with scale, but I made the alterations for flight characteristics only on Pat’s suggestion, plus using built-up construction on the suggestion of another West Mendip club modeller.
(My Dart came out even lighter than his).

Not sure if Cliff sent you my Mk1 version design which had a flat centre section & dihedral starting where the wing halves plugged on (non scale), or the Mk2 version where the centre section was angled (after I worked out that I could just about get a single straight joiner through everything).
I built the Mk1 version.
In both cases, I worked on the basis that the centre section would stay attached to the fuselage, so attachment can be more solid here. My Dart uses MPX Unilocs to secure the wing halves to the centre section & steel screws to attach the centre section. My wing cover is removeable but only after removing a couple of screws at the rear of the cockpit.
I work on the principle that if something can go wrong, then sooner or later it will & I will need access to fix it!

I would have liked to fit aileron servos at the horn location, but chickened out due to the reduced wing thickness with the HQ section. However it may well be possible with slim wing servos, so await the outcome of your build with interest.

N.B. If you find any issues with the drawings, please let Cliff/me know so that they can be improved.
Peter

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 05 Jul 2019, 18:12
by B Sharp
I have reinforced the fuselage floor with a patch of glass cloth and polyester resin. Once that had dried I cut and ground off the forward skid. I will now require to add a little P38 to the bottom of the fuselage before sanding it all back to profile. While I was in dust creating mode I cut the hole for a fixed undercarriage (I don't want to mess about with retracts at this scale) as although the model will be flown mostly off the slope I still want to do the occasional aerotow launch. I also trimmed down the sides of the cockpit and wing openings to get a neater finish.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 06 Jul 2019, 15:16
by B Sharp
I was trying to resolve in my mind the whole “tail volume” problem that Peter mentioned in his post. I resorted to drawing a complete fuselage/fin/rudder at 1/5 scale as measured from my 3-view drawings. I checked this with the CW drawings as well and found that there were only very minor differences (well done Chris). When I superimposed the fuselage moulding on top of the scaled drawing the difference became instantly apparent as you will see from the attached image. Pat and Peters approach of adding 2 inches to the top of the fin is not really the answer as it actually only needs to be elongated by just over an inch (30mm). The rear of the fin needs to be stretched backwards by nearly an inch and the hinge line rake increased.
Ok, how am I going to achieve this?
Don’t know as yet! It’s time for a little thinking and perhaps a little glass of Scottish falling down liquid.
Brian. :?

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 06 Jul 2019, 20:15
by chris williams
Believe me, Brian, when I built my 3.5 Dart, I had many sleepless nights over the size of the tiny tailplane. It turned out to be no problem at all: that, and the experience of losing one half of an Algebra tailplane with no noticeable effect, has led me to believe that the tailplanes on a lot of models were much larger than they needed to be.

When it comes to the smaller models, though, I have become a great advocate of increasing the chord of the wing by at least 5%. Wing loading becomes increasingly relevant the smaller the size of the glider, and any unnecessary weight has a greater significance...

BTW If you'd kept quiet about the shape of the fin, I can guarantee that nobody would have noticed!

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 06 Jul 2019, 21:26
by B Sharp
Yes Chris, all very true. However, I would know and it would annoy me.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 06 Jul 2019, 21:43
by chris williams
I have always found that the secret of a happy life is learning how to keep secrets from yourself... :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 07 Jul 2019, 00:18
by Jolly Roger
Really excited about your build Brian.

A question about the fuselage. To me the fin looks pretty close to scale outline, but did you say the rear fus was 130mm too short? This would bother me more than the fin discrepancy.

And a very fine point of detail (cos I know you like this stuff Brian!) I spent this afternoon crawling over a full-size Dart 17R and noticed that even the retracting u/c version has a very slight nose skid. Who knew?

The skid protrudes about 1/4" below the fuselage, is maybe 3" wide and runs from about a foot back from the nose tip to the wheel bay. It's slightly filleted so that you would only notice it if you looked for it. See photo.

I asked the owner if this was the vestige of it originally having a fixed u/c and skid but he confirmed it came out the factory like this, as did all Dart 17Rs.

I only mention this now as I know you'll be filling and sanding your fuselage about now and may wish to include this feature with a strip of 1/16" ply or whatever.

Cheers,
Rog

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 07 Jul 2019, 08:16
by B Sharp
Rog, what I think I will do is to extend the hinge line of the fin rearwards by 23mm and remove the top of the fin and replace with the correct shape. This will give a final shape which is much closer to scale and increase the tail volume at the same time. This is illustrated in the image attached.
A check of my scale drawings shows the full size Dart 17 fuselage length from nose to rudder post to be 7.0 metres as near as I can make out. At 1:3.5 scale this equates to 1.40 metres (which is pretty much the length of my 1:3.5 model by CW). The glass fuselage is 1.255m which scales up to 6.275m, 0.725m short or 0.145m at 1:5 scale. As I intend to add a further 23mm to the rear of the fin this will make the finished fuselage length 1.485m which equates to 122mm shorter than scale.
Now I suspect that the fuselage has probably been shortened by this amount in order to cut down the amount of lead that is required to balance the model. I know that in my CW Dart the majority of the nose cone is either lead or filler which makes it a bit of a lump.
However I am not sugesting in any way that a Dart built to the plan and unmodified will not fly well. All of Pats aeroplanes fly well. It is just my tendency to be finiky that leads me to make these proposed modifications.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 07 Jul 2019, 08:57
by Barry_Cole
Pat's ??

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 07 Jul 2019, 16:03
by B Sharp
Yes Barry. This fuselage dates back to West Mendip Sailplanes (Pat Teakle) as I have flown a couple from that era. Granted that these are now produced under the ownership of our own Cliff Evans. Can anyone correct me on this?
Brian. :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 09 Jul 2019, 17:40
by B Sharp
Before I do any work on the modifications to the fin/rudder area I need to get the equipment bay sorted out. I need to be able to locate a servo and pushrod so a servo/Rx tray has to be installed. However before that I have to install the wheel well and axel supports. These were made out of ply and were glassed into place.
The servo tray is also made of ply and fitted just above the wheel well once again glassed in place. All very easy-peasy.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 11 Jul 2019, 17:21
by B Sharp
Having sorted out the wheel and servo arrangements at the front end its now back to the tail end again.
This afternoon I have built the tailplane halves. Due to the shorter than expected tail moment arm I have increased the area by 10% to retain the stability factor. You can see that the blanks have a very simple structure which mirrors the construction used by CW in his plans. I will leave these to set up solid for 24 hours before sanding them to section tomorrow.
I also constructed the all-moving-tailplane horn using epoxy board and brass tubing.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 13 Jul 2019, 16:27
by B Sharp
The tailplane is now finish sanded and weighs in at only 1.4oz or 42 gm with which I am very pleased.
The fin was carefully drilled and the actuation slot formed. The slot allows for a little more up elevator than down. The elevator crank fitted in perfectly and the tailplane now sits neatly in place.
The next task will be to manufacture and fit the pushrod before finally fixing the crank into place.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 16 Jul 2019, 15:24
by B Sharp
A nice 6mm carbon fibre tube has been formed into a pushrod with clevises at both ends and the tailplane crank swivel tube has been glued in place. The tailplane now sits absolutely square with a long baton sitting across the wing seat.
The fin extension pieces have been manufactured out of ½ inch balsa sheet (stiff but light) the front edged of which has been grooved to allow the balsa to sit inside the moulding by 6mm. I cut the top off the fin and a balsa substitute will take its place.
This has increased the width of the fin considerably and the height by about 30mm.
The next job will be to “pretty up” the whole assembly.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 22 Jul 2019, 10:02
by B Sharp
I have now just about finished with the tail end of the Dart. The fin extensions were glued into place and a 5mm strip of 1/64 ply attached each side to form shrouds for the rudder hinge line. After sanding I skimmed the fin with a very thin coat of filler and sanded it all back to smooth. I was pleased to find that this only added 30gm (1 oz) to the total weight of the fuselage.
The rudder was constructed and after final sanding it weighed in at 14gm (0.4 oz)
Yes, I have made a whole pile of extra work for myself by reconstructing the fin/rudder area, and yes, the plane would probably have flown absolutely fine without the modifications. However I’m happier that the whole of the tail is much closer to the scale outline.
The only work still to be done is to attach tailplane root ribs onto the side of the fin which will help support the tailplane pivot tube and tidy up the fin/tailplane junction.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 22 Jul 2019, 17:23
by B Sharp
A wet afternoon has allowed me to get on with the tail end of the Dart. I have now attached the stub roots for the tailplane and applied a little filler to fair them into the fin. Image #2 below shows the complete fin, tailplane and rudder assembly. I have only the hinges and horn to fit to the rudder before these are ready to cover.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 24 Jul 2019, 10:34
by B Sharp
Having now finished the tail end the next job is the wing centre section. The plans show this centre section protruding out from the fuselage sides slightly and being attached to the fuselage with 4 x 4mm bolts. The implication being that the assembly stays bolted to the fuselage semi-permanently and the wing halves attach to that.
Once again I can’t leave things alone and I have planned to attach this assembly to the fuselage with a single dowel peg to the rear and with a metal flange/wooden block and two bolts at the front, accessed through the cockpit. This will mean that I don’t have four bolt heads visible from the top.
The laser-cut ribs for the assembly fit together very quickly and accurately. My only comment is that there are 2 x F1 ribs which have to be glued together to locate in the centre. A single F1 rib made of 3mm ply would have been more sensible.
The whole construction is absolutely straight forward with the exception of the trailing edge. Here the plans show a 1/32 plywood trailing edge which butts up against the rear of the ribs and is held in place by the balsa sheeting above and below. I have to say that I have never seen this form of construction before. After a bit of thought I constructed a TE component from the ply laminated with an oversized piece if 1/16 balsa sheet on the underside. I made extensions to the rib up-stands to support the TE in the correct position whilst gluing the sheeting to the underside of the ribs. Once the top sheeting is in place this should stabilise the TE.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Jul 2019, 17:41
by B Sharp
I now have the wing centre section basically complete. The images below show top and bottom. The rectangular holes will house multiplex six-pin sockets. The underside has holes for the servo wires to drop down into the fuselage. The hardwood block near the leading edge is there to mount an alloy flange which will locate against (and be screwed to) a hardwood bar in the fuselage.
The trailing edges haven’t worked out as I had expected. You can see from the images below that they look great in the drawings but rather less so in reality. I think I will try sanding them a little more in the hope of getting a more accurate shape.
Brian. :? :? :?

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Jul 2019, 20:14
by Peter Balcombe
Brian,
Upper surface contour not too difficult, but the concave lower surface needs a bit more work to remove the natural angular effect ;)
A couple of quick snaps of my (now a bit careworn) centre section & matching wing root for info.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Jul 2019, 20:50
by B Sharp
Hi Peter. I notice that your underside at the rear is a bit angular as well.
However, I made up a couple of shaped sanding blocks and the profile is now very much better. Strangely the underside is now very close to my template while the upper is still slightly concave. However I suspect that it will be fine and the vast majority will never notice.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Jul 2019, 21:01
by Peter Balcombe
It just goes to show what a craftsman you are Brian :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Jul 2019, 22:12
by B Sharp
Awh, shucks Peter. Most of my friends just say I'm fussy and slightly anal.
Brian :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 26 Jul 2019, 17:56
by B Sharp
I have now set up the alloy flange on the centre section underside and the retaining bar in the fuselage. The flange is held onto the hardwood bar by two 4mm screws and will be a semi-permanent fixture, removable for maintenance.
I have attached an 1/8 ply former at the rear of the centre section assembly and this has a dowel which locates it firmly to the fuselage. I just have to add some filler to the fuselage to form a snug wing seat.
It looks as though I will have to start the wings fairly soon.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 29 Jul 2019, 19:53
by B Sharp
I have now formed the wing seat using good old P38 filler and the wing now sits snugly to the fuselage. The wing fairing came with the fuselage and is a polyester/glass moulding. I have to say that it took a whole afternoon of trimming with a Dremel, knives, a file, sandpaper and a couple of tins of elbow grease but I did end up with a pretty good fit.
The next job is to manufacture the canopy frame, even although I haven't got a canopy as yet.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 01 Aug 2019, 14:21
by B Sharp
I have spent a very enjoyable couple of hours building the canopy frame. It is built primarily from 1/8 ply, the side panels being 1/32 ply. It is held in place on the fuselage by a peg at the front and 4 button magnets at the rear (2 in the fuselage and 2 in the frame). A canopy moulding is on its way from Barry at Sarik. He informs me that it was taken from the original Pat Teakle moulds.
This will probably be my last post on the little Dart for a while as other “Life” matters will be taking up my time for the next several weeks.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 01 Aug 2019, 15:30
by Jolly Roger
Tidy work as always Brian. Looks very scale too. Good luck with "Life".

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 01 Aug 2019, 15:44
by Barry_Cole
The words Canopy and Enjoyable should never be used in the same sentence.....

:shock: :shock: :shock: :shock:

BC

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 01 Aug 2019, 18:55
by GeeW
To clarify the above, he was talking about the nice wooden canopy frame and not the clear plastic bit that gives all the aggro..so enjoyable can be used in this context I believe?

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 01 Aug 2019, 23:32
by B Sharp
GeeW is not far wrong! Timber wrestling is no problem at all, entertaining, relaxing and enjoyable. Plastic canopy wrestling is whole different ball game, which is why I always order two (just in case).
Brian. :D :) :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 02 Aug 2019, 00:28
by chris williams
Barry_Cole wrote:
01 Aug 2019, 15:44
The words Canopy and Enjoyable should never be used in the same sentence.....

:shock: :shock: :shock: :shock:

BC
How would you know...? You get some other shmuck to do it for you :roll:

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 02 Aug 2019, 09:22
by B Sharp
Maybe I should set up in business as a "Canopy Shmuck" since so many people hate the job!
Brian. :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 02 Aug 2019, 11:39
by Barry_Cole
B Sharp wrote:
02 Aug 2019, 09:22
Maybe I should set up in business as a "Canopy Shmuck" since so many people hate the job!
Brian. :D :D :D
Take care what you wish for !!!!!!!

:shock: :shock: :shock: :shock:

BC

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 13 Aug 2019, 17:05
by B Sharp
It’s been a wet day, I couldn’t get the grass cut and the fruit and veg harvest was halted as well. So I resorted to the workshop and trimmed up the canopy to fit the frame. The frame will now have to be painted before I attach the canopy with good old canopy glue and lots of masking tape.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 13 Aug 2019, 19:57
by Barry_Cole
AAAAAAAAAAAAAhhhhhhhhhhhhhhhhhhh

I can't stand all this tidiness......

:shock: :shock: :shock: :shock:

BC

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 13 Aug 2019, 21:19
by chris williams
Come round to my place...that'll calm you down!

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 14 Aug 2019, 09:38
by B Sharp
Barry, would it sooth you if I left a couple of artistically placed wood shavings in my photos in future?
Brian. :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 14 Aug 2019, 12:32
by Barry_Cole
B Sharp wrote:
14 Aug 2019, 09:38
Barry, would it sooth you if I left a couple of artistically placed wood shavings in my photos in future?
Brian. :D :D :D
It would certainly help, Brian.......
:D :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 14 Aug 2019, 14:31
by Tony Woods
How about a good Razor as well. :lol: :lol: :lol:

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 14 Aug 2019, 17:47
by B Sharp
Ah jolly banter. Goodness how I realy miss it!
Brian. ;)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 16 Aug 2019, 10:00
by Tony Woods
Barry can hand it out but I am just testing to see if he can take it. :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 16 Aug 2019, 10:56
by Barry_Cole
I have a razor plane, I can make shavings too. I just cannot clear them up as fast as Brian.

The Wookie will remain quite and aloof as ever.

:o :o :o :o

BC

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 16 Aug 2019, 11:44
by Peter Balcombe
Barry_Cole wrote:
16 Aug 2019, 10:56
I have a razor plane, I can make shavings too. I just cannot clear them up as fast as Brian.

The Wookie will remain quite and aloof as ever.

:o :o :o :o

BC
If only..... :lol: :lol:

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 19 Sep 2019, 15:48
by B Sharp
Life is starting to return to normal for me so I felt I had better get back to the Dart 17 build. The easy start was to finish off the cockpit and canopy. The canopy and frame are now painted in the same colours I used for my 1:3.5 version. I manufactured an instrument panel and binnacle and that has been glued to the frame after painting. You may notice that I have also made a very simple seat and the side fittings in the fuselage which will be painted later.
By the way, if you look closely in the background you can see all the spars etc which are now ready to begin the wing build.
Brian. :) :) :)

Oh, Sorry Barry, I forgot to leave a couple of wood shavings in the pictures. :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Sep 2019, 12:26
by B Sharp
The dart build is progressing once again. I have started on the right hand wing build and it is going reasonably well. The plan shows servo trays in the wing for ailerons and brakes. However I am putting servos out at the aileron positions and I will use electronic brakes. This means that there will be a little bit of modification required. The wing extension to make a 17 rather than a 15 wing has gone ok so far. :) :) :)
I have left my bench untidy this time for the photo in an effort to help Barry Cole's "TIDY" anxiety problem. :D :D :D
Brian.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 25 Sep 2019, 12:35
by Barry_Cole
I feel so much better now.....

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

BC

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 26 Sep 2019, 11:57
by terry white
Hi Brian, I couldn't work with such an untidy bench. :roll:

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 26 Sep 2019, 13:24
by B Sharp
I know what you mean Terry, it is absolutely atrocious, but you have to take Barry's sensibilities into account.
Brian. :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 06 Oct 2019, 17:47
by B Sharp
This has to be the slowest build that I have ever done. However it has been bucketing rain today so I have managed to spend several hours in the workshop.
The wing joiner boxes and their packing pieces were slid into place and glued up. At the moment there is no easy way for me to check their alignment so I will just have to trust in the laser cutting. The webbing between the spars has been added, 1/16 ply at the wing root and 1/16 balsa the rest of the way to the tip.
The upper leading edge sheeting has been glued and pinned in place. I nearly ran out of pins! I also cut out the slots for the airbrakes and dry – fitted the assembly in place. I have uses 0.225 electric units from “Gliders” as I have found them to be reliable in the past and it saves me messing about with servos and pushrods.
The weather forecast for the next few days is a bit variable so I suspect I will get some more of the upper surface sheeting in place quite soon.
Brian. :) :) :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 06 Oct 2019, 18:11
by Peter Balcombe
Looking good Brian. 🙂👍

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 08 Oct 2019, 17:10
by B Sharp
The top surface sheeting is now almost complete and has been trimmed up round the edges. The more observant among you will have noticed that I have opted for the more scale like open structure inner trailing edge rather than the all sheeted version. Having said that, at fifty feet no-one will know the difference (except me of course). ;)
I have now started the underside sheeting. I am keeping my fingers crossed that I haven’t forgotten to install anything crucial before it is all closed off. :roll:
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 11 Oct 2019, 17:27
by B Sharp
Well that’s one wing now basically complete. The underside sheeting and rib caps have been added. The servo bay has been cut and prepped for the aileron servo. The wing tip and leading edge have been added and the whole wing sanded to shape.
I have also fitted the electric air brake, capped it and sanded it all to the wing profile. I am quite pleased with the finished panel as it is very light and fairly stiff. :)
The next job will be to repeat the process on the other (left) wing.
Note to self: Make sure it’s the left wing, make sure it’s the left wing, make sure it’s the .................. :D :D :D
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 11 Oct 2019, 19:56
by B Sharp
Gee, That was helpful Cliff! I can now look forward to Barry's little gem of wisdom.
Brian. :?

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 11 Oct 2019, 23:37
by Barry_Cole
I give in. I cannot beat that....

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

BC

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 12 Oct 2019, 08:59
by Peter Balcombe
You will soon know if you have made the right wing Brian, you won’t have any left overs :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 12 Oct 2019, 11:03
by B Sharp
Problem is Peter that I have made the right wing and I still have plenty of left overs!
Brian :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 23 Oct 2019, 12:57
by B Sharp
With the completion of the left wing, all of the main building on the Dart is now done. Today I was able today to assemble the whole airframe for the first time. Once again the tailplane size is giving me a little concern. Even although I increased the area by 10% it still looks very small. As usual there are also one or two minor fitting issues to be sorted out before covering can begin.
I suspect that I will be spending the next week covering and possibly painting however that is weather dependent to a certain extent.
There are still loads of little finishing jobs to be done as well as all the elictrickery installation to be finalised. Plenty to keep me occupied!
Brian. :) :) :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 27 Oct 2019, 13:04
by B Sharp
I have managed to move things on a bit with the Dart in the last few days. I have done a bit of painting as you will see. I have also started the radio installation with the receiver seat, elevator and rudder servos and also the tow release servo down on the cockpit floor. All of this has gone without any difficulty. I have also started the covering process with the tailplane halves using white “Profilm”.
The wings will be next.
Brian. :) :) :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 28 Oct 2019, 08:16
by John Vella
Brian, I wouldn't be concerned over the smallish tailplane on the Dart as it does have a long moment arm. The full size flew okay. I would be more concerned on keeping the back end of the Dart as light as possible for begnine handling. Regards John.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 28 Oct 2019, 08:26
by B Sharp
John, the reason that I am so concerned about the tailplane area is that the fuselage of this model is shorter than scale as was discussed way back in the first couple of posts on this thread. On my 1:3.5 version, which has a scale length, I had a tailplane half fall off in flight and still remained controllable. Knowing that the fuselage is shorter on this model I designed the tail to be 10% larger to give me a little margin of safety.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 28 Oct 2019, 09:11
by Peter Balcombe
Brian,
The Dart15 version flies well with the original size tailplane which was solid balsa in Pat’s original kit, but made as semi-open structure in the later design to reduce nose ballast & overall weight.
The extra 10% tail area you added should be fine, even with the increased span.
Peter

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 28 Oct 2019, 09:29
by B Sharp
Peter, I didn't recieve any plans for a tailplane so I checked drawings and also my 1:3.5 unit and calculated a 1.5 tailplane. I then increased the volume by 10% as a rough guess. It still looks small by comparison to the wing area, but that's a Dart trait. As I said earlier my big one flew on 1/2 tailplane so If I have any major problems I can make a slightly enlarged version.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 28 Oct 2019, 11:43
by Peter Balcombe
Sorry Brian,
I now recall that when I remodelled my Dart15 tail feathers, I took the original tailplane half planform & knocked up an equivalent with what looks like a solid front (covering both joiners) with a few rear riblets to simulate the full size open rear structure.
I never got around to putting the tailplane detail down on paper, so the built up plan only covered the wing.
Each tailplane half is 275mm long, Root chord approx. 125mm, tip chord approx. 97mm
The pic below gives an idea of the internal structure.
Peter

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 30 Oct 2019, 16:19
by B Sharp
Peter, Your tailplane construction looks almost identical to mine although the area of mine is fractionally less than yours. It looks as though "Great minds think alike". (We will now wait for the usual response to that last comment from any number of the usual people !)
Today has been spent doing "Life" things but I will get down to work soldering up the wiring harness after tea.
Brian. :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 03 Nov 2019, 14:21
by B Sharp
I now have two completed and covered wing halves. The wiring has been completed with Mpx plugs and sockets and the Mpx wing retainers have also been fitted in the wing roots.
The thin wing servos have been glued into the servo bays in the wings and the ailerons fitted and hinged with “Sylglas” tape. The aileron pushrods are so short that it proved a bit of a problem to make them adjustable. I usually fit two metal clevises back to back on a threaded rod however there was no room to do this on the dart. You will be able to see from the photos how I resolved the problem.
The fuselage is also nearing completion. All the radio gear is now in place with the exception of the battery and the wheel has been fitted. The battery will be fitted once I start balancing.
I am now fast approaching the point when I will have to assemble the component parts and work out the C of G. The default position will be just forward of the spar but I will use a CG calculator to find the range of settings that I want.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 03 Nov 2019, 14:50
by B Sharp
I have just done the CofG calks and they are very interesting (to me at any rate).
The set of drawings which Clive has recently sent me show the CofG at 57 mm back from the leading edge of the wing.
My first calculation with the static margin set at 15% (safe) has the CofG at 53mm back from the leading edge.
With the static margin re-set at 10% (which is where I will likely end up after a couple of trimming flights) the CofG comes in at 61mm from the leading edge. This gives the recommended 57mm a calculated static margin of 12.7% - not unreasonable at all under the circumstances.
It looks like I will add lead to the nose till I get 57mm then work backwards from there towards 61mm.
Brian. :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 03 Nov 2019, 15:53
by Peter Balcombe
All looks very nice Brian :)
I look forward to hearing of the successful maiden flight.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 03 Nov 2019, 17:30
by B Sharp
Thanks Peter. However, the way the weather is shaping up at the moment it may be some time before I get the Dart in the air.
Brian :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 05 Nov 2019, 14:30
by B Sharp
Well the Dart 17 build is now officially over.
After a moulded lump of lead weighing 570gm was added to the nose the final weight of the model came in at 2.86kg (6lb 4oz in old money). This gave a wing loading of 18oz/ft2. I am quietly pleased with this weight and loading as it will be easy to carry up my local hill and should have a reasonable light wind performance.
I have attached a pile of photos to this post showing the fully assembled model. The photo of the tail end shows the much modified fin and rudder which I think justifies the effort involved as it looks just right to me. I was a little worried that the centre section/wing joint area would look a little strange but the photo from above shows that I managed to achieve the classic Dart outline.
The only thing left to do is fly the model. I would ideally like a 8mph to 12mph West to South-westerly with no rain and not too cold. When I do manage the maiden and if I get some photo I will post them in the “Who’s building what for” thread.
A Very Happy and Contented Brian. :D :D :D :D :D

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 05 Nov 2019, 15:59
by Peter Balcombe
Very nice Brian :)
I’m sure that it will fly very nicely.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 10 Nov 2019, 09:58
by StephenB
Another cracking job Brian!

Being surrounded by flat terrain only relieved by volcanoes which are covered in trees or vineyards, and so un-flyable, I'm very envious of your slope - what a wonderful view.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 10 Nov 2019, 18:20
by B Sharp
Thanks Stephen. Yes it is a super slope with a great view down the River Tay valley. Its the only and best Easterly slope in a 60 mile radius of where I live and only 10 minutes drive from my house. It curves round to the West where it becomes a southerly slope as well. The only problem with most Scottish hills is that they also involve a 15 to 20 minute walk, usually uphill. Hey Ho, it keeps me fit.
Brian. :)

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 11 Nov 2019, 22:39
by FrankS
Brian, super job, looks great.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 12 Nov 2019, 11:43
by roo Hawkins
Looks great mate.what are you building next.

Re: 1/5 Scale Slingsby T51 Dart 17.

Posted: 12 Nov 2019, 22:28
by B Sharp
Thanks Roo. I lost (quite literally! ) my 2.00m electric thermal model quite recently. This was my go-to model for relaxed flying from my garden so it had to be replaced asap. A nice new semi kit from the Czech Rep. is now taking shape on the workbench and should be operational by early December. After that I have another scale job lined up - one that I have never modelled before!
Brian. :)