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SZD-8 Jaskolka 1/3 Scale**

Posted: 27 Sep 2021, 13:03
by Peter Balcombe
With workbench nearly cleared of other projects, it’s time to start the next major build from the Laser Cut Sailplanes range - this one being a 1/3 scale version of the Jaskolka from the drawing board of Jilles Smits.
I’ve always wanted to build a Jaskolka & nearly did the 1/4 scale one from the John Watkins plan many years ago.

A couple of areas have been in hand for a few weeks in order to identify potential mods to the standard short kit - these being the nose tow release and retract.

The bespoke nose release is similar to that built for the Olympia & ASK13, but is based on a 7/16” brass tube, so I wanted to make sure that I could reliably get a tow loop into it before fixing in the 3D printed nose cone & front former.
The release mechanism comprises a 45degree front angled dowel in the brass tube plus an 1/8” brass rod cross-bar and 2mm release pin which goes through the dowel & rests on the top of the cross-bar.
I used a piece of 3/32” x 1/8” strip resting on the inside of the tube to drill very small (0.7mm or so) pilot holes across the tube at just under 5mm up from the bottom of the inside, then opened these holes up to take the cross pin.
This allowed a builders line sized loop to be slid under the cross-pin & just left enough room above it to get the release pin to go through the loop.
The other tip is to make sure the angled dowel is far enough behind the cross-pin to allow the loop to pass & angle up to the top of the tube. The drawing gives dimensions for wedge & cross-pin distances from the rear of the tube.

Tube & cross-piece
Tube & cross-piece
Tube from front
Tube from front
Tube & loop in place
Tube & loop in place
View from rear
View from rear

The plan identifies the use of a 4” Dubro wheel, but I am using a firmer FEMA wheel which is 8mm wider - hence the retract & fuselage mounting need modification.
For the retract, the mods are as simple as making the brass spacing pillars & 1/8” steel pins 8mm longer. The F9 & F13 formers are also tweaked to move the retract mounting slots out by 4mm each side & up by 2mm to prevent the retract metalwork protruding from the curved fuselage. Cliff will be cutting some modified formers to check-out these mods.
Meanwhile, the retract looks like this:

Wheel down
Wheel down
Wheel up
Wheel up

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 27 Sep 2021, 21:54
by Elliot Howells
ooh, 1:3 scale Jaskolka?! Yum.

Can't wait to see your build pics, Ell.

would love to see some thumbnails of the plan, what type of wingjoiner etc?

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 27 Sep 2021, 22:23
by Peter Balcombe
Hi Elliot,
Wing joiners are twin 15x2 steel blades mounted into a substantial laminated fuselage scissors type block.
Tailplane halves have separate servos & are mounted using a pair of 1/4” diameter round joiners.
The wings are quite busy as there is what appears to be a good Fowler flap operating mechanism, plus the normal top/bottom Schemp Hirth airbrakes

Fuselage assembly will start tomorrow with the laser cut forward fuselage parts, including the long sliding canopy cockpit surround, whilst I await the revised formers to take the wider retract assembly. Hopefully, the fuselage skeleton will go together over the next week or two once I receive my impending stripwood order.
Peter

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 28 Sep 2021, 08:03
by Steve Walton
Hi Peter
The retract unit looks very neat & tidy , Is it your own work

Steve

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 28 Sep 2021, 08:33
by Cliff Evans
The retract unit was designed by Jilles and is on one of the plan sheets.

Screenshot (76).png

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 28 Sep 2021, 09:15
by Peter Balcombe
The retract parts have been a collaborative effort, with 3mm steel (rather than 4mm aluminium) side plates laser cut by Stuart Marriott & the longer FEMA wheel brass spacers turned up by Steve Vincent - many thanks lads :)
The torsion spring used to counterbalance the wheel weight is from a mole trap mechanism, but a little too strong. I may end up making a bespoke spring which relieves servo forces in both up & down directions as at present the down going load is much higher.

The wing joiner arrangement is shown below. The removeable retract goes through the section noted as to be removed later & fits between 2 keel pieces which extend from the nose to just aft of the retract area.
Wing joiner arrangement
Wing joiner arrangement

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 28 Sep 2021, 09:42
by Steve Walton
Thanks Cliff
Very neat design
Steve

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 28 Sep 2021, 14:46
by Peter Balcombe
The fuselage is now being built up on a straight/flat length of 6” x 1” planed softwood, 2.4m long to cope with the 2.2m+ length over the fuselage formers.
With the board sitting on a flat bench & a centreline marked along its length - let’s get started :)

First job was to glue the base of Former F1a to the building board in parallel with adding the 2 nose skid doublers to the centre keel. I then used the notched centre keel to position the next two ‘based’ formers (F5 & F8) on the building board.
At this point, I realised that once these extra formers were fixed to the building board, I wouldn’t be able to slide the 2 main keel pieces into position, so added small hardwood strips to the bases of F1a & F8 to enable them to be screwed back into the correct place once removed (see photo).

Forward formers secured to board
Forward formers secured to board

Once this had been done, it was a simple matter to remove the 3 formers + centre keel assembly & fit the 2 main keel (K1) pieces into place before re-fixing everything back onto the building board. Formers F2 & F3 can then be fitted & secured at the top centre with S2. F6 & F7 can also be added, plus the tow release & retract servo trays ST1 & 2.
I’ve currently left fitting the canopy frame surround & upper nose strips (S3) as these need the former slots to be angled from their 90degree laser cuts. Thus I will wait until the glue has set on the initial assembly.

Forward Assy + servo trays
Forward Assy + servo trays

Whilst waiting for the glue to set, I can glue up the main wing joiner box assembly using epoxy to provide a really rigid unit. This unit comprises 4off slotted ply pieces (each taking a 16x3mm brass tube) sandwiched between 2 ply formers & everything pegged together using 4 alignment dowels.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 28 Sep 2021, 22:06
by Peter Balcombe
Fuselage build now with upper nose longeron strips, canopy front and canopy frame in place, although rearmost canopy frame joints as yet unglued to allow it to be raised slightly whilst further formers are fitted behind F8.

D2138ECC-B9D4-449A-853D-62731FC66EA0.jpeg

Note that a good way to position the bottom legs of F4 is to temporarily screw the front canopy plate (C4) onto the top of the sloping fuselage canopy frame (CF) using the pre-cut holes/pilot holes provided.
The bottom legs of F4 should rest against the front face of C4.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 01 Oct 2021, 10:02
by Peter Balcombe
My stripwood order from SLEC arrived yesterday, plus some 15x2 joiner strip/tube from Cliff - so onwards with the fuselage build :)
The joiner tubes (each 226mm long) are glued into the 4off F11 parts as these are sandwiched (2 LH next to F10, followed by 2 RH, followed by F12) between F10 & F12 & everything positioned using 4 dowels through everything.
Remember to use epoxy for these bonds as noted on the drawing.
Fit F9A to the rear of F9 and F13A to the front of F13 (retract attachment doublers) & then the formers back to F14 can be added (remembering to fit BR6 between F12 & F14 via F13 as you go).
Most of these formers need the canopy base to be raised up a little as they are inserted & dropped into their keel slots, so the rear of the canopy base can be secured once TE formers are in place.

With all the formers in place, the wing Root LE profile FR1 can be inserted, followed by the root ribs which slot over several formers. Note that the root ribs are settled in slightly different places to suit the staggered joiner positions.
Finally, F14A can be added behind F14, aligning the circular lightening holes to get the rear incidence tube slots in the correct place.

Moving rearwards, the top spine piece can be slotted into the tops of F13 & 14 & F15 to help position the rear fuselage formers in due course. Meanwhile, splice up two lengths of 3/8” x 3/16” spruce to produce the rear keel strip S6.
Centre section
Centre section
Wing joiner area
Wing joiner area
Rear incidence doubler
Rear incidence doubler

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 01 Oct 2021, 17:16
by Peter Balcombe
Using the rear fuselage spine strip notches to locate the rear formers, plus the front of the rear keel strip (S7) fitted into its slots in the forward formers (F13-15) it is a straightforward task to add the full length formers back to F21, followed by the intermediate ones. (I checked each was vertical & secured the bottoms of the full length ones to the baseboard as for the forward formers.
F21 also needs the fin LE strip adding to the rear of the spine strip. (This is notched into the spine and slots into the top of F21). Note that S7 projects well behind F21 as this ends just behind the fin post.

The tailplane mounting assembly can now be assembled between F22 & F24, also comprising the BR1 & BR2 braces plus the tailplane root ribs and bottom fin rib. The completed assembly can then be sat onto S7, with the lower fin rib FR3 notching onto the fin LE immediately below a rearwards projecting shape.

Full length Fin post F25 can be added, notching into the rear of FR3 and it’s angle defined when the top rib FR7 is put in place. FR4-6 can be fitted to complete the fin structure.

Finally, the 2 wing TE fairings FR2 can be fitted between F15, F16 and the root ribs to complete the laser cut item build stage.
All laser parts fitted
All laser parts fitted
Tailplane mount & fin
Tailplane mount & fin

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 06 Oct 2021, 10:11
by Peter Balcombe
All fuselage stringers/longerons are now fitted and 1/8” balsa doubler strips fitted around the edges of the front end formers in order to increase glueing area for the ply skins.

The 3D printed nose has also been fitted with captive M3 screw studs & the tow release tube in readiness for installation once the forward skins are in place. Temporarily fixed in position for assembly check prior to skinning (Note that an 1/8” brass rod will be epoxied through the rear of the tube when finally fixed, to transfer tow loads to the front formers).

The first of the four (top/bottom & left/right) 3D wing root fairings has also been printed (albeit with my only available filament colour!) & check fitted. This print failed on the last legs but shows the smooth complex curves.
Nose & former edge doublers
Nose & former edge doublers
Wing root fairing
Wing root fairing

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 06 Oct 2021, 21:21
by Cliff Evans
Dash panel done!

20211006_211949.jpg

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 08 Oct 2021, 11:43
by Peter Balcombe
Fuselage skinning now started & going quite well as the smooth natural curves allow several former bays to be covered in one go. Thus, I have managed to apply the 0.8mm ply on the forward fuselage in only 3 pieces each side - going down to the main longeron (S1).

The front section back to the canopy front was the most difficult, due to the larger compound curves, but with a bit of care & initial steaming in-situ (wetted ply & hot covering iron to steam off the moisture) it stuck ok using the iron-on technique. The 2 other pieces were a doddle.

Upper nose skin
Upper nose skin

Note that the 2nd section only goes back to the wing LE as the 3D printed root fairings fill up most of the fuselage side back to F9. The 3rd piece covers the entire over wing section back to F15, where 0.6mm ply takes over.

Upper wing area
Upper wing area

Note that I have added extra 1/8” balsa doublers in several places to increase the skin glueing area.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 08 Oct 2021, 15:49
by Peter Balcombe
1st 3D printed fin fairing just out of the printer & check fitted ok.
(These fairings could be used to ensure that the relevant fuselage formers are parallel to each other if available at that stage of the build).

Note that the solid base & front/rear could probably be removed after printing to leave the curved shell only - otherwise holes need to be made in base & rear in order to pass the rudder C/L tube through.
RH fin fairing
RH fin fairing

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 10 Oct 2021, 20:10
by Peter Balcombe
And a full set of 3D printed fairing are now complete.
They each took a while on my basic printer, but the end results look good.
(Background selected just for Brian S 8-)
Fin & wing LE fairings
Fin & wing LE fairings


Meanwhile, the fuselage upper skins have been fitted back to the fin, where 0.4mm ply will now take over from the 0.6mm material for the fin and fin base.
A start has also been made with the wing stubs, fitting the 1st layer of 0.4mm in 20mm strips spanwise. A 2nd layer will be fitted with joints staggered to achieve a 0.8mm thickness, but allowing a better fuselage/wing fillet curve.
Upper rear fuselage skins
Upper rear fuselage skins

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 13 Oct 2021, 13:36
by Peter Balcombe
The rear upper skins have now been fitted between the main longeron and the lower fin rib as shown below, using more 1/8” balsa doubler strips to provide additional glueing area and support for skin joints as appropriate.
The fin fairing pieces have also been epoxied into position, plus the rudder C/L tubes fitted - just need to break out the rear ends of the tubes through the skins shortly.
Lower fin skin/fairing
Lower fin skin/fairing

Skinning the wing roots has also progressed to the stage where the 2nd layer of 0.4mm ply strips is now being fitted.
The upper LE fairings can be put in place once the top layer in in place & the edges cleaned up.

LH root fairing strips
LH root fairing strips
Both fairings
Both fairings

With the upper fuselage skins in place, the fuselage should now be stiff enough to remove from the building board to deal with the lower half. However, I will leave for the present whilst I complete the wing root area skins.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 14 Oct 2021, 09:55
by Jilles
From one beginner to an other beginner. it is looking promising

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 14 Oct 2021, 10:44
by Mike F
Hi Peter

Thanks for sharing your build with us.

May I ask, are the printed fairings part of jilles original design, or is this an adaptation that you have created? The leading edge fairings should reproduce the smooth flowing transition from wing root to fus.

Many thanks
Mike

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 14 Oct 2021, 11:09
by Peter Balcombe
Hi Mike,
The fairings are all part of Jilles’s design & I’m sure can be supplied with the short kit, much the same as the 3D printed nose cone.

(Cliff originally had some problems printing some of the fairings, so I had a go & got them out ok.
I since have sent my print settings to Cliff, so hopefully all is sorted now.)

Peter

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 17 Oct 2021, 18:22
by B Sharp
This is all very interesting Peter. The problem with using 3D printed components is that not everyone has the facilities.
Brian. ;)

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 17 Oct 2021, 19:30
by Peter Balcombe
Brian,
I think the intention is for Cliff to supply the 3D printed parts as part of the kit, so the builder doesn’t need any printing facilities :)
The only reason I printed some for this first build was that Cliff was having trouble getting a good print at the time.
Peter

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 17 Oct 2021, 20:02
by Cliff Evans
3D--printed parts are not necessary. They will be an add-on to the kit if wanted. The parts they replace are easily carvable by the modeller if that is what they would prefer. The fowler flap runners are also available as 3D-printed parts, but they will be printed in carbon loaded filament to add strength and consistent accuracy to the parts. These can also be made from glass board, again, the choice of the modeller.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 18 Oct 2021, 14:59
by Peter Balcombe
With both upper wing root areas now double skinned with 0.4mm ply & the upper root fairings added, the fuselage has been removed from the building board and the former stands removed. (The structure feels very light at this stage).
Fuselage removed from board
Fuselage removed from board


Inverting the structure on a model stand, the lower front can be prepared (more balsa former edge doublers added & sanded to profile) for skinning.
I have so far added the first 2 segments on each side, prior to fitting the 3D printed nose cone complete with ballast weight & tow release.

The carbon loaded nose cone is quite short on this model (compared to the Oly), so I have decided to epoxy M3 screws into the 4 fixing holes (fitted from the inside) & then epoxy the tow release tube into position, checking that the tow release tube fits through the hole in the front former such that the 1/8” brass anchor cross-pin can be fitted later.
I’ve added lead to take the overall nose cone assembly to just over 600g so far. I don’t want to add too much in order to ease fixing loads & ensure that the model isn’t nose heavy to start with!
Ballasted nose cone
Ballasted nose cone


With the fuselage off the building board, it is now possible to trial fit the retract unit with wheel fitted. (The view from the top is past some temporary former cross-pieces still to be removed)
Retract unit trial fitted
Retract unit trial fitted


External views of the wheel up shows that the lower edges of retract frame is at the correct height relative to the external skin. The wheel-up photo shows the wheel a little lower than full up, but that is due to it’s position being governed by the wheel counterbalance spring only. Once the retract servo is connected, the servo will provide th small amount of force to ensure the retract rests against it’s mechanical (cap heads resting on bottom of side plates) ‘Up’ stop.
Wheel nearly fully up
Wheel nearly fully up


In the ‘Down’ position, the wheel is locked down by an over-centre linkage.
Wheel down
Wheel down

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 19 Oct 2021, 15:34
by Peter Balcombe
With the nose area skinned & nose cone prepared/checked, the cone has now been epoxied & bolted to the fuselage, plus the retention cross-pin epoxied into the tow release at the back of the front former as shown on the plan.
The release pin has also been made from a hard 2mm servo rod & operation checked with an available std servo.
Nose cone fitted
Nose cone fitted


The release pin is set up on the servo to engage the loop with full forward servo travel (no load on the servo). Release requires the servo to rotate approx. 1/4 turn to one side or the other, pulling the pin back.
Pin forward
Pin forward
Pin back
Pin back

Meanwhile, the temporary cockpit area crossbars have been removed & the retract temporarily fitted -again using the available 5kg torque servo. This servo is easily able to actuate the retract.
Note that if using the FEMA wheel option, the M3 tapped hole spacing on the retract retention plate should be revised to 44mm to suit the holes in F9/9A. (Due to the wider retract frame tabs occupying the normal hole areas in the Dubro wheel variant)



With the cockpit area crossbars removed, the cockpit starts to look the part.
Cockpit crossbars now removed
Cockpit crossbars now removed

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 23 Oct 2021, 18:16
by Peter Balcombe
The forward (0.8mm ply) lower skinning has now been completed, using mostly single bay pieces to reduce complex curves, although a triple bay piece was easily fitted around the wheel aperture.
Further skins will be 0.6mm until the very aft sections (as for the upper skins).

Lower forward skins
Lower forward skins

The retract assembly has been refitted to get an idea of external appearance now that the skins are in place.
Not sure if the full size wheel opening is infilled to follow the wheel contour, especially at the rear.
A balsa block could be fitted prior to glassing the fuselage.

Wheel retracted
Wheel retracted
Wheel down
Wheel down

Noting that the elevator servos are mounted in the tailplane halves, with the 2 servo cables being totally enclosed until they exit the fuselage at the root ribs, the cables must be installed before the rear fuselage is closed up 😉
Thus, 2 elevator servo cables have been fitted & secured to F21 using tie wraps through the holes provided.
It will probably also be prudent to all secure the cables at the tailplane root end to make sure the connectors cannot fall back inside the fuselage 😎

Elevator servo cable exit
Elevator servo cable exit
Fuselage fixings
Fuselage fixings

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 24 Oct 2021, 10:39
by Mike F
Hi Peter

I have this photo from a polish website (can't recall which one) which shows a Jaskolka wheel well. Hope this helps.

Mike

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 24 Oct 2021, 17:14
by Peter Balcombe
Thanks Mike,
It will probably leave the rectangular opening for the present at least.

Meanwhile, I have been thinking of how to retain the wings, particularly as with the fairly large fuselage wing root stubs, there is something like 360mm between each root.
There is no method shown on the plan, but an email chat with Jilles has led to me going for a variation on the clamped tongue method used on both the recent Olympia and the ASK13 builds.

I have made up a 4mm ply fuselage plate with 4mm ply doublers & M4 captive nuts at each end which is fixed to the underside of internal fuselage cross brace BR6 just behind former F13, so that the fixings are easily accessible via the root rib opening just in front of the rear incidence location. The wings will be fitted with 1mm aluminium tongues projecting from the wing roots that slide just underneath the fuselage plate & can be clamped against the fuselage plate using M4 cap head bolts inserted from the underside. Note that the arrangement is intended to provide sufficient friction to retain the wings under normal flight conditions, but allow the tongues to slide out if all goes pear shaped!

Fuselage plate
Fuselage plate
Underside view of installation
Underside view of installation
View through from underside
View through from underside

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 29 Oct 2021, 13:32
by Peter Balcombe
The fuselage skinning is now nearly complete (except for lower wing root fairings), with just the bottom of the fin to do now.
Lower fuselage skins
Lower fuselage skins

The rear skid appears to be shown on the plan as a single 6mm ply piece glued onto the underside of the skinned fuselage. However, I thought it better to at least anchor the skid to the 3/8”x 3/16” lower keel strip to provide a bit more resistance to getting side-swiped off in the event of a less than straight landing touchdown.

Thus, I initially made up a 3/16” thick skid from 4mm ply sandwiched between 2 pieces of 0.4mm ply, then added two 0.8mm ply side plates which extend over the sides of the keel strip in the large gap between formers. All is epoxied together.
Laminated tail skid
Laminated tail skid

Balsa strips will now be added & sanded to profile on each side of the skid to support the final piece of 0.4mm ply skin.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 31 Oct 2021, 16:13
by Peter Balcombe
With the fuselage skinning virtually complete following application of the pieces each side of the tail skid, it’s time to move on to the wing structures before closing up the lower fuselage root areas.

Once the 1/2” x 1/4” spruce main spars have been spliced up/tip ends tapered & the false LE + main spar web pieces joined up, it’s a straightforward task of assembling the majority of the wing structure.
I started by glueing the spar onto the lower front face of the spar web, remembering to have the tapered main spar surface on the inside of the wing & also remembering that the web ends at R28 - not the tip!
Also remember to fit the main spar doubler at the root end of the spar.
Note that the spar web only goes inboard to R6 as individual web sections go between each rib towards the root.

I started at R6, working steadily outboard, adding servo plates, flap linkage pivot plates etc. as I worked outboard.
If a few widely spaced ribs are initially fitted onto the spar web/lower spar + false LE, then subsequent ribs can be dropped in between these two span-wise main members.

I suggest adding the slotted & tabbed flap & aileron LE webs before the full span rear spars are added, as these will locate the rear of most ribs. If you leave this till later, you are likely to find that the rib rear ends are in the wrong place ;)

Anyway, after only a day & a bit, I now have the 1st wing with nearly all of its cut parts & spars.
Root end view
Root end view
Tip end view
Tip end view
Flap/brake servo areas
Flap/brake servo areas
Outer flap/Inner aileron break
Outer flap/Inner aileron break

The twin brass joiner tubes have also been slid into position.
Note that R1 & R6 are handed for right & left wings as the joiner slot positions are staggered differently in these ribs for each wing.
Right wing joiners in position
Right wing joiners in position

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 02 Nov 2021, 11:14
by Peter Balcombe
A little more progress in the last day as the main joiner tubes have been completely blocked in to fill all voids between the brass tubes and the main spars, making this area a completely solid lump.
The RH wing tubes fit up against the spar web at the rear, so 1/2” x 1/4” strip has been used edgewise to block in above & below, with 2 layers of 3mm ply in front.
W9 & W12 are provided as front spar webs at each end of the joiner area.

I may also fit additional front webs between W9 & W12 as on the Left wing, the staggered joiners are towards the front of the spar. Thus the 2 x 3mm ply infill will be at the back, so a front web will finish things off.
(An ex Stress Engineer fried has since advised it prudent to fit the proposed extra webs, plus additional front webs in the next 3 or 4 bays outboard of R6 in order to provide a more gradual stress relief taper.)

Main joiner boxing
Main joiner boxing

Meanwhile, attention is turning to fitting the TE and the flap tracks.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 05 Nov 2021, 17:26
by Peter Balcombe
Moving on to the wing trailing edge, I have now assembled the 3 tracks from the supplied parts, 3D printed from Carbon loaded filament.
I’ve initially assembled the tracks with just the rear brass cross-pin, plus M2 bolts instead of brass pins in the forward (sliding) fixings. My reasoning is that the bolts will allow easier disconnection/re-connection of the flap assembly until after the flap LE & wing shroud have been fashioned & all has been shown to work correctly.

Flap tracks closed
Flap tracks closed
Flap tracks extended
Flap tracks extended

The 3 working flap tracks can then be epoxied into the wing structure, the fixed part notching into a front vertical plate & the rear wedged between the rear top & bottom spars.
At this point, it becomes clear if the rear of the ribs are in the correct position or not - the movable part of the flap tracks are notched to sit in the notched flap LE webs. If the ribs re not quite aligned correctly then they won’t line up with the web notches and/or the intended gaps between the fixed TE & flap/aileron TE will be wrong!!
(So it is strongly suggested that the flap & aileron LE webs are used to correctly locate the rear of each rib BEFORE the ribs are fixed to the rear spars. You can see in the photos below where some of the LE webs have been cut and extended by a couple of mm to get the control surface ends in the correct place).

Inner flap track
Inner flap track
Centre flap track
Centre flap track
Outer flap track
Outer flap track

I am deviating from the plan (3mm ply TE core) to use a 1/16” Balsa/1/16” Ply/1/16” Balsa TE sandwich which allows me to profile the TE down to the 1.6mm ply core rather than sand ply. The sandwich is kept straight by clamping the outer layers to a sturdy spruce strip whilst the glue between balsa & ply dries.
The photos show only the upper balsa TE strip fitted to the aileron so far.

Flap/root TE core
Flap/root TE core
Aileron TE core/top strip
Aileron TE core/top strip

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 06 Nov 2021, 11:27
by Mike F
Hi Peter

Thank you for sharing your detailed build progress on the Jaskolka. Jilles solution to the flap mechanism looks well engineered and I am also trying to adapt it to suit the John Watkins 1/4 scale version.

I now have the modified parts to suit the 1/4 scale model and your build log will be of major assistance in getting a functioning flap installation.

Thanks for sharing your build details.

Mike

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 06 Nov 2021, 17:32
by Peter Balcombe
Once the rib sections in flap LE/shroud gap (except for the few ribs which end with a full shroud profile) have been removed, we get the following gap forward of the flap LE web & the flap can be slid back on its 3 tracks.

Separated flap
Separated flap
Full movement check
Full movement check

Next up will be cutting out the aileron & installing the flap actuation mechanism.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 07 Nov 2021, 20:15
by Dopieman1
Thanks for posting the construction of this rather complex wing! I am following with great interest!!!

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 09 Nov 2021, 00:37
by Jilles
When the design of this model was started the request was to have scale like working Fowler flaps.
Some info was available about the distance travelled and rotation of the full scale flaps. The model flaps do move now to scale as dictated by the full scale data.
A test jig was made to see if it all worked and that did not have any problems
it is a complicated setup and I would not recommend this on smaller scale model with identical Fowler flaps
Even with this large scale 1:3 model you need all the space the get it moving and make sure all push rods and servo can work without interference
Not easy to build but these type of models do need more expereinced builders anyway
I am in regular contact with Peter during this build and I am sure Peter will make it work satis factory
Cheers
Jilles

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 13 Nov 2021, 11:36
by Peter Balcombe
The majority of the flap actuation mechanism has now been assembled, albeit using metric sized links instead of 2-56 threaded parts a shown on the plan.
The long 1/4“ dowel pushrods were also changed to 6x3mm carbon rods, with short M2 threaded rods epoxied into the ends to mate with M2 ball-link ends. The three pushrods going to the flap tracks were upped to M3 & the M2 ball-link ends drilled 2.4mm & then tapped M3. The M2 ball-link at the flap track ends were drilled out to 2.4mm to accept the 3/32” track pins which will be fitted instead of the current M2 bolts at the end.

The cranks are shown on the plan & could possibly be made from servo arms, but Cliff kindly printed some equivalents to that shown on the plan using carbon loaded filament.

The 3 flap track links & associated crank connections to the interconnecting pushrod are shown below.

Outer end
Outer end



Inner end
Inner end

I have also drawn up (& got Cliff to cut) some 1/16” ply templates for the flap & aileron LE/shrouds.
The plan is to use these to aid profiling of solid balsa LEs & act as a seat for 0.4mm ply shrouds.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 15 Nov 2021, 18:50
by Peter Balcombe
Whilst waiting for some longer M2 machine screws to arrive, I’ve assembled the tailplane & rudder structures.
The tailplane halves include elevator servo mounts and also accept joiner tubes to give the tailplane its distinctive dihedral.

Tailplane halves on joiner bars
Tailplane halves on joiner bars

Whilst the plan shows that the rudder ribs are mounted at 88.9 degrees to the rudder post, this is easy to sort once the 2 TE pieces have been joined & then glued to the rudder post spar (the ribs then fit into notches at each end).
I’ve fitted a 1/4” balsa strip to the front of the rudder post spar in preparation for fitting a 3/32” Al. guide tube for a long hinge pin passing through all three 3/16” pin hinges, thereby allowing the large rudder to be easily removed.

Rudder framework
Rudder framework

Although the plan says that the balsa rudder base should be 12mm thick, this I only for the first 70mm. I have therefore fitted a 1/4” doubler, plus an extra 1/4” for 70mm adjacent to the rudder post spar.

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 16 Nov 2021, 15:21
by Peter Balcombe
The tailplane is attached using two 1/4” Al. joiner rods, with the rear one secured to each tailplane half by an M3 machine screw inserted from the bottom into the outer end of the joiner.
I’ve just drilled & tapped the rear bar to take the screws & checked all fits nicely - adding the unfinished rudder for effect.

Tail feathers coming along
Tail feathers coming along

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 17 Nov 2021, 18:41
by Cliff Evans
Peter has only gone and got them working!


Re: SZD-8 Jaskolka 1/3 Scale

Posted: 17 Nov 2021, 18:48
by Peter Balcombe
Longer (20mm to cut down as required) M2 screws arrived today, so I was able to fully secure the 3 flap cranks to their supports & connect the 3 flap pushrods to the track attachments in place of the 3/32” brass pins which will be fitted later.
The temporary M2 fixings give a little bit more play than should be present when the final 3/32” (2.38mm) track pins are fitted & M2 locknuts will be fitted to other attachments, but the servo appears to operate the long flap ok.
Note that the wing is inverted ;)

Re: SZD-8 Jaskolka 1/3 Scale

Posted: 17 Nov 2021, 20:49
by Peter Balcombe
Rudder hinge pin guide tubes fitted today using 3/32” aluminium tube spaced 0.4mm off the 1/4” initial balsa LE to place the hinge centreline 8mm in front of the rudder post spar. As shown below, the tube sections were glued in place once aligned with a long 16swg wire through all 3 dry fitted hinge points.


Rudder hinge pin guides
Rudder hinge pin guides


The hingeless pin hinges will now be removed & the guide tube buried inside the balsa LE when the remaining thickness is added. The pin hinge centres will be rediscovered from the rear & opened up in due course.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 18 Nov 2021, 10:47
by Mike F
Nice work on the flap mechanism, Peter!

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 22 Nov 2021, 14:56
by Peter Balcombe
The rudder structure now has the rest of the LE balsa fitted & cut to the correct outline prior to nose profiling.
The balsa tip has also been fitted & rough shaped. The pic below shows the long hinge pin going from top to bottom.

Rudder LE & hinge wire
Rudder LE & hinge wire

The flap has been disconnected & removed from the wing by undoing a few M2 fixings & then short pieces of 3/16” spruce used as temporary spacers between the 3 sets of flap tracks to support them at the front - particularly the centre one - to keep the flap straight & resist a tendency for the TE to snap as there is not much meat to resist bending loads when the flap assembly is off the wing.
I have fitted flap & aileron LE profile templates every few ribs then infilled with balsa to give a LE profile guide on each item. Seems to be working ok & I should have a much more accurate & consistent LE on each part.
The balsa TE outer layers have been sanded back to give a tapered profile with ply core just exposed at the rear to give a uniform TE thickness prior to adding the ply capping.
The aileron LE strip is 1/2” balsa, whereas the flap LE is a bit wider, so I’m using two thicknesses of 3/8” balsa & sanding back to the templates.

Flap LE prep
Flap LE prep

Flap & both ailerons
Flap & both ailerons

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 24 Nov 2021, 11:47
by Peter Balcombe
Th fin skinning has now been completed and the balsa fin top added/shaped.

Fin top added
Fin top added

With the extra strip of balsa added to the flap LE, this is now ready for shaping back to expose the ply templates.
Meanwhile, attention has turned back to the cockpit area.

Th front canopy hoop has been added with the top 11mm forward of vertical & balsa dummy panel former/side rails added to support the 0.4mm ply binnacle sheeting. The dummy panel former has been mounted 5mm forward of its normal position to allow for the visible panel thickness (see much earlier post for pic of panel made by Cliff Evans).
Note that the forward canopy is removeable as it slots into the fuselage former at the front & is retained using 2 screws (inserted from below) at the rear.

Front canopy binnacle prep
Front canopy binnacle prep

The sliding canopy uses 3 slotted brass section rails (available from Mick Reeves models). A rail is fitted each side of the fuselage canopy opening at the front, with a single (central) rear rail fitted in the underside of the canopy as shown below. M2 cap head screws are fitted in the sliding canopy side frames & the rear fuselage to engage in the slotted rails.

Fuselage side rails
Fuselage side rails
Rear rail
Rear rail
Canopy frame sat in place
Canopy frame sat in place

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 24 Nov 2021, 17:13
by Peter Balcombe
And after a productive afternoon getting the three M2 cap screws in place, the sliding canopy now fits & slides ok.
Next up will be fitting the forward canopy binnacle sheeting, the sliding canopy hoop & headrest, prior to tackling the metalwork for the canopy latch.

Front slide retaining cap heads
Front slide retaining cap heads

Rear slide cap head in fuselage
Rear slide cap head in fuselage

Fully back - rear just engaged
Fully back - rear just engaged

Closed
Closed

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 25 Nov 2021, 16:40
by Peter Balcombe
Forward canopy binnacle now in place and Cliff’s dash panel just sat in place for now (until canopy unit painted ready for glazing in due course).
Front hoop also epoxied to the front of the sliding canopy, so can now see the overall effect.

Printed dash panel
Printed dash panel
Forward canopy frame in place
Forward canopy frame in place
Sliding canopy closed
Sliding canopy closed
…and open
…and open

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 26 Nov 2021, 20:21
by Peter Balcombe
Onto the canopy latching mechanism today.
The notched brass strip is made from 1/32” brass strip (Four 2mm holes slotted to the edge).
The tiny brass crank is also fashioned from 1/32” brass strip before being fitted (soldered) with short pins.
I found an eBay outlet that made 4mm tension springs to any defined length.
The knurled knob will be secured on the outside of the canopy later. This allows the latch pin to be lifted to disengage it.
The 4 positions are: Closed, 15mm gap, 30mm gap & fully open.

Latch parts
Latch parts
Left side
Left side
Detent strip & latching pin
Detent strip & latching pin

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 02 Dec 2021, 17:23
by Peter Balcombe
Having started a spate of metal fettling, I’ve moved on to the airbrakes & cut out the 6 brass arms & soldered the pivot tubes in all items at the same time as shown on the plan to ensure all have the same centres etc.
There are 3 arms per brake, so 6 blade pivot pins & 3 box pivots are required per brake assembly.

Brake assy metal part set
Brake assy metal part set


Small laser cut 0.8mm ply axle washers are provided to fit on the inside of each blade, acting as pivot hole doublers.
Make sure that these washers are fitted on the correct side for each ‘handed’ brake assembly, otherwise the blade assembly will not fit in the 9.5mm wide brake assembly.
The plans call for 6mm wide blade spacers, but I’m hoping to get away with 1/4” balsa.

The RH brake blades have been glued up & dry assembled onto one of the brake box sides (front) as shown below in both closed & fully open positions.

RH brake closed check
RH brake closed check
RH brake open check
RH brake open check

The blade pins can now be carefully epoxied into the blades, hopefully ensuring that the pins rotate freely in the blade axle tubes. Once the pins have been filed flush to the blades, the assembly can be fitted into the wing box & connected to its servo, plus the blades profiled to match the wing outer surface - which means the blade tops being distinctly angled front to rear.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 03 Dec 2021, 13:49
by Peter Balcombe
With blade pins safely epoxied into position & then filed flush, the brake assembly can be slotted into the box gap, the 3 main pivot pins inserted and a check made to ensure free movement (may need to tweak main pivot pin alignment to make sure the blades sit centrally fore & aft in the box aperture).
My use of a 1/4” blade spacer gave me a snug (0.8mm gap each side) fit in the box, so any distortion is more critical, but it seems to work ok with the blades centralised using 0.8mm ply strips as feeler gauges.
1/8” hardwood/ply pivot pin support doublers are fitted on the outer faces of the box at each pin position & these help to maintain any tweaked pin positions & get good free movement. It is also a good idea to take the sharp edges off of the brake box openings & blades to help guide the blades back into the box, rather than jam.

I hooked the brake up to another slim wing servo using a 2mm pushrod, extenders & M2 clevises.
Note that the photos below are all from the underside of the wing in order to see the servo connection better.

Brake inboard end
Brake inboard end
Brake outboard end
Brake outboard end

Hopefully, Cliff can add a video of the brake cycling shortly.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 03 Dec 2021, 14:17
by Cliff Evans

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 04 Dec 2021, 13:15
by Peter Balcombe
Twin rudder horns made & fitted in balsa support block plus rudder LE profiled, so a mandatory hingeing check with forward pin hinges part dry fitted into the fin post.

Rudder hinge check
Rudder hinge check

Ply cap strips yet to be fitted, plus optional rudder light bezel.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 05 Dec 2021, 22:47
by Cliff Evans
Elevator test



Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 15 Dec 2021, 12:37
by Peter Balcombe
Work has been progressing on the tail & these are now virtually ready for the covering stage.
The rudder top has been revised to take a 3D printed clear glass effect rudder light fitting (unlit due to relatively dim bulb fitted on full size for night flying only).
A thin surround will be fitted over the light in due course to represent the full size attachment cover.

Rudder hinged
Rudder hinged
Rudder light mod
Rudder light mod

Meanwhile, the tailplane & elevator have now been skinned & finished off ready for covering.

Finished tailplane assemblies
Finished tailplane assemblies

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 19 Dec 2021, 09:56
by Peter Balcombe
Back to the wing now.
Using the ply flap & aileron shroud templates as a guide, balsa strips were added using Aliphatic glue & then the shroud profiles sanded using a 12” long length of 3/8” dowel with 120 grit emery paper glued to make a long round file.
With the balsa sanded down flush with the ply templates, the control surfaces fit nicely.

The brass tubes which take the aileron hinge barbs have also been epoxied into place with the ailerons in situ. to ensure correct positioning - the tubes being pushed back to ensure maximum barb engagement.
The photos below show how the tubes project behind the shroud line.
The current gap between the inner & outer ailerons will be reduced by adding a doubler to one end riblet.

The flap was refitted (using bolts again) to check shroud fit & operation. A 25mm section has been removed from both shroud & flap LE at each track position to allow the pairs of track holes to be accessed, but I realised that the shroud could be left intact if the flap is attached in the extended position, so this will now be replaced.
A previously mentioned, 3 keeper sections of flap LE will need to be able to fitted on final flap assembly in order to retain the ball link on the actuation pin. These can either 3D printed or could be end sections of a full balsa sanded LE, temporarily removed after LE sanding to allow fixings to be put into place until final assembly.

The upper D box skin has also been added over the whole wing using 0.6mm ply. The 0.6mm ply is much more resistant to finger damage during handling/rigging - although it currently seems to be expensive & hard to find :(
As it comes in 50” Sq. sheets, the wing can be done with just a single spanwise joint.
Note that I have initially sheeted to halfway across the 1/2” wide main spar in order to apply the rear sections separately. (The upper outer rear section has 2 top aileron horn pushrod penetrations & the inner bottom rear sheet prevents further access to the flap actuation linkage).

Aileron hinge barb tubes
Aileron hinge barb tubes
Twin aileron ends
Twin aileron ends
Inner flap track
Inner flap track
Centre flap track
Centre flap track
Outer flap track
Outer flap track
Ailerons in place
Ailerons in place
Inner D box top skin
Inner D box top skin
Outer D box top skin
Outer D box top skin

Note that the aileron hinges are not fully pushed into their tubes in the above outer wing pic. Hence the strange TE line!

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 19 Dec 2021, 15:24
by Peter Balcombe
Trial fitted some simple non-tapered (25mm long) LE profile sections for each of the 3 flap track positions.
These will probably need a small rebate notch at the track end to accept the rear of the ball-link moulding.
In hindsight, the ball-link probably cannot move sideways enough to come off the brass actuation pin due to it being restrained by the width of the vertical slot in the rear spar web - just forward of the flap LE :)
However, access to the rear brass slide pin is still required to insert this & hence the gap needs to be filled once done - unless you want to leave a 21mm+ gap in the LE adjacent to each slide :o

Outer flap LE insert
Outer flap LE insert

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 21 Dec 2021, 12:56
by Peter Balcombe
Upper root end rear skin section now fitted, airbrake released, then airbrake cap strip glued in place.
The wing cables have also been cut & fitted with an 8 pin MPX type connector at the root.
The step in rear of skin is where the flap shroud ends - aileron shroud is slightly smaller than flap at this point.

Upper root skins
Upper root skins

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 21 Dec 2021, 15:26
by B Sharp
I am glad that it's you and not me trying to set that all up Peter. Well done that man!
Brian. :o

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 23 Dec 2021, 10:13
by Peter Balcombe
1st wing D box now skinned & spruce strip hatch openings put in for flap & brake servos.
8 pin MPX connector receptacle also mounted on a plate in fuselage wing root with internal harness to reach to the expected Rx location behind the pilot seat.

Root D box
Root D box
Tip D box
Tip D box
Wing root connector
Wing root connector

The wing just needs the retention tongue fitted into the root rib & it will be time to take a stiff drink before closing up the rear root section, complete with flap actuation linkage & airbrake opening!
I think that I will need to make the brake opening in a sheet & then finally fit to suit that ;)

The LE can now be added (1/2”, with 1.5” wedge at root). I’m thinking of making this with a 1/4” hardwood face to help reduce impact damage in view of the likely flying sites! The wings will be glassed using lightweight cloth (except for control surfaces) so this should also help.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 27 Dec 2021, 17:07
by Peter Balcombe
1st wing now completely skinned & the flap mechanism & airbrakes still seem to work :)
Lower root skins
Lower root skins
Lower top skins
Lower top skins


All 4 wing servo apertures have also been released ready for simple skin ply thickness covers - which on this model have no pushrod penetrations as the ailerons are actuated by top mounted horns, so penetrate the top skins.
The full size (at least on SP3675) appears to have a single aileron pushrod shroud on the upper wing surface as the single/split aileron horn(s) is located at roughly the centre of the overall aileron length.


The model has separate servos & top horns for inboard & outboard sections, so 2 pushrod exits & shrouds are needed.

Although I have previously used the free online TinkerCad application for making simple 3D shapes, I thought I would try Fusion 360 (free online tool for non commercial/personal use) as this allows objects to be created by ‘lofting’ between 2 or more shapes (in this case, 2 half ellipses + half a racetrack shape) to create a solid which could then be hollowed out (shelled) & the bottom chopped off to give the required result. A bit of a learning curve, but lots of videos to help 8-)
The results appear to come out well when printed on my simple 3D printer & seem to be a decent fit :)
(The 3D solid object could probably alternatively be used as a pattern to create plunge moulded or vac-formed items)

3D printed shrouds
3D printed shrouds
Dry fitted shroud
Dry fitted shroud

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 27 Dec 2021, 17:27
by Peter Balcombe
Forgot to add that that the wing retention tongue was also epoxied into the 1/8” ply root rib doubler prior to fitting the lower rear root skin.
This was done after a dry check & then epoxied with the wing fitted to the fuselage & the tongue held by the clamping bolt - ensures that it will all go back together again ;)

Wing retention tongue & connector
Wing retention tongue & connector


The photo also shows the wing 8 pin MPX connector plugged into the fuselage loom.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 27 Dec 2021, 21:22
by Dopieman1
Peter Balcombe wrote: 27 Dec 2021, 17:27 Forgot to add that that the wing retention tongue was also epoxied into the 1/8” ply root rib doubler prior to fitting the lower .....,
Peter, thanks for posting! I will apply same construction on my Ikarus Meteor

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 31 Dec 2021, 21:50
by Peter Balcombe
2nd wing now started & I used a modified assembly schedule this time in order to ensure that the rib TE areas were all in the correct places.
As before, I started by splicing & tapering the main spars, plus glued the spar web & false LE sections into complete lengths. I then attached the lower main spar to the spar web, ensuring it was the right way around & overhung the web correctly at each end to allow for tip & root ribs later.

Ribs were then slotted ‘dry’ onto the web/lower spar & false LE , with the rear ends located using FWA, FWB, W7 & W8. All other items that notch into the ribs, such as servo trays, flap assembly plates were located & placed in rough position ready for assembly.
With the structure notched together & all building tabs sat down on the building board, it provides a self jigging assembly, enabling individual/rib pair to be slid upwards to temporarily remove, glue & servo trays etc added & then replaced into the structure.

Th root end ribs can be added in sequence, using the separate webs 4a-4d to correctly space on the spar, plus BS1, HP1 & BR5 at the rear.
2nd wing structure dry assembly
2nd wing structure dry assembly

The brake box sides & upper rear spar can be fitted once all ribs are in place.

Ribs & webs glued
Ribs & webs glued

Before fitting the root rib, the joiner area doubler & my additional wing retention doubler are fitted. (The hole near retention tongue slot enables the long flap pushrods to be slid into place once the plate blocks most of the root rib access hole)

Root rib doublers
Root rib doublers

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 12 Jan 2022, 16:22
by Peter Balcombe
I’ve not posted for a few weeks, but the 2nd wing has steadily progressed & the airbrakes are now installed as well as the flap linkage.
Reading the wing drawing again, I decided to mount the inboard flap crank pivot doubler on the upper side of the pivot bracket, rather than the lower side as for the centre & outer - this is much better for crank/fixing clearance through R3 at full travel.

By the way, I measured my flap pushrods to help others get the fit right when the assembly is slid in from the root rib. My inner pushrod is 472mm between ball-link attachment hole centres, with the outer one being 564mm.
Once again, I fitted a spacer nut between the central crank & the double-ended ball link connector in order to allow the screw head on the servo pushrod fixing to clear this connector at full travel.
My 3 flap track actuation rods are all 93mm between attachment centres (as initially installed).

Flap & aileron LE balsa has been fitted & is awaiting sanding back to the ply profile templates as done on the 1st wing.
The hinge shrouds will again use a similar construction method.

2nd wing brake & flap linkage
2nd wing brake & flap linkage

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 07 Feb 2022, 09:53
by Peter Balcombe
Both wings are now fully skinned and the 1st has had an additional thin root facing rib applied to ensure a flush fit against the fuselage rib when rigged. (The fuselage root rib was straight & flat, but the wing root rib slightly dished - so a small gap in centre) :o

With both wings nearly complete (LE profiling to be completed) & virtually ready for glassing, attention has moved back to the fuselage wing root to skin the underside sections of the root stubs.
Ply faced balsa blocks (complete with wing retention bolt clearance hole) have been fixed in place over the retention plates, leaving an 1/8” gap for the retention tab to slot in. With the lower surface of the block profiled to the wing surface, skinning can be put on. Note that there are 2 overlapped layers of 0.4mm ply to fit.
Retention tab slot
Retention tab slot
Bolt/washer clearance hole
Bolt/washer clearance hole
1st root stub skin layer
1st root stub skin layer

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 27 Feb 2022, 14:02
by Peter Balcombe
With the lower section of the fuselage wing root fairing now skinned & all lightly filled to achieve nice blended curves, it’s time for a rigging session (less wing flappy bits!) to check the fuselage/wing & tailplane skin surface levels & fill as required to level.
The skim of filler cut through with a scalpel when it goes to a plastic constituency.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 09 Mar 2022, 22:45
by Peter Balcombe
Lightweight glass cloth has now been applied to the fuselage, wings & stabilisers, with a 2nd weave filling coat of epoxy applied yesterday/today on both wings once the aileron pushrod shrouds had been fitted.
Wings glassed
Wings glassed

The missing radio set has also been fitted to the instrument panel.
Fully populated panel
Fully populated panel

The ‘flappy bits’ will now be completed (rib caps etc. fitted) & Ceconite covering added whilst giving the fuselage glassing epoxy a bit more time to harden ready for sanding back joint edges etc.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 17 Mar 2022, 11:59
by Peter Balcombe
Fuselage has just received its glass weave fill coat, plus 1st side of stabilisers (forgot to do 1st side with 1st side of fuselage ;) ) so just those bit to do now to finish epoxy tasks.
Meanwhile, the control surfaces have had their rib caps fitted, so nearly ready to cover.

Front fuselage & servo hatch covers
Front fuselage & servo hatch covers
Rear fuselage & stab
Rear fuselage & stab

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 23 Mar 2022, 11:38
by Peter Balcombe
With fuselage epoxy coat given an initial sand back to remove bumps etc., forward canopy frame & instrument binnacle in place, it’s time to try the sliding canopy for size 😀

Canopy trial fit
Canopy trial fit

The brass headrest support structure will now be fitted & all the sliding canopy framework painted light grey before the glazing is fitted.
I was going to install the front canopy section glazing first, but on reflection, this needs to be done once the sliding canopy glazing Is in place as there needs to be a small ‘lip’ over the canopy joint & the front glazing angle should make this more easily done later.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 23 Mar 2022, 20:43
by MartinE
That canopy has a great shape to it! Glad you got the sliding mech working.

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 23 Mar 2022, 21:15
by Peter Balcombe
Thanks Martin.
The canopy has 3 ‘C’ rails (2 fitted to fuselage at front sides & 1 fitted centrally at rear, under the canopy frame) which slide along entrapped cap head screw heads to give a fully parallel sliding action.
This is unlike the full size where the (narrower) metal canopy frame allows the rear to dip down along the top of the rear fuselage as the canopy is slid back - the canopy frame clearing the sides of the fuselage further forward.
However, Jilles has kept the simple latch mechanism which allows the canopy to be locked in the closed & several partially open positions.
Apparently it was common for Jaskolka pilots to fly with the canopy open 6” or so to get more ventilation, despite the higher noise level. (I think the only other ventilation was via a simple small triangular flap type vent at the forward RH corner of the sliding canopy).

Triangular vent flap
Triangular vent flap

Canopy dips at rear
Canopy dips at rear

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 28 Mar 2022, 21:18
by Peter Balcombe
Sliding canopy glazing fitted today. With the canopy glue virtually all dry (clear), I’ve just removed the masking tape holding the edges down & checked that the canopy still moves. 👍

Sliding canopy glazing
Sliding canopy glazing

I also thought it worth adding a representation of the rear lifting handle assembly (in closed position) to the rear fuselage. This has been done by epoxying a shaped 93mm length of 1/4” dowel to the top of the fuselage above Former 20 & then carefully slitting in 2 places to mark the ends of the retracted handle.

Rear lifting handle
Rear lifting handle

Last job today was to fit the elevator servo cable connectors so that I can check the completed tailplane units. Note the tie-wrap used to prevent the cable from disappearing into the fuselage 😎

Elevator servo connector
Elevator servo connector

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 28 Mar 2022, 22:19
by Peter Balcombe
This is the rear lifting handle (in the open position) on a full size Jaskolka.
The lifting handle rotates to be in-line for storage & is raised at 90 degrees for use.
Rear lifting handle
Rear lifting handle

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 31 Mar 2022, 08:58
by Peter Balcombe
Front canopy glazing formed from 1mm PTEG sheet.
I first cut the sheet roughly to size, then put into a curve by wafting a heat gun over it, before cutting to near shape.
A final waft with the heat gun settled the front curve nicely before final trimming & glueing (frame sat on a shiny tape to act as release layer) - sliding canopy temporarily slid on to hold rear hoop in position until glue had started to set, then backed off to prevent everything sticking together.
All seemed to go well & the edges tidied up nicely.
Now looks a lot more like a Jaskolka 😀

Canopy fully glazed
Canopy fully glazed

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 03 Apr 2022, 12:53
by Peter Balcombe
Last post for a while as the Jaskolka is now paint-shop ready, so should pop out some time in the Yellow livery of SP-3675, now back in Polish hands.

Final rigging check
Final rigging check
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Tail feathers
Tail feathers
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Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 03 Apr 2022, 18:33
by MartinE
Looks great.
Will you paint the fibre covered control surfaces?

Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 03 Apr 2022, 19:03
by Peter Balcombe
MartinE wrote: 03 Apr 2022, 18:33 Looks great.
Will you paint the fibre covered control surfaces?
Martin,
The intention is that she looks like this when finished, so yes, everything is due to be painted.
Everything is currently an epoxy finish except for the Ceconite covered control surfaces which have been sealed with a couple of coats of cellulose dope, thus paint needs to be compatible with this.
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Re: SZD-8 Jaskolka 1/3 Scale**

Posted: 10 Apr 2022, 10:32
by VinceC
What a stunning model you have made Peter. Great credit to you and now looking forward to the finish