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SZD-8 Jaskolka 1/3 Scale**

Let us all watch your new project progress.
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B Sharp
Posts: 891
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: SZD-8 Jaskolka 1/3 Scale

Post by B Sharp »

This is all very interesting Peter. The problem with using 3D printed components is that not everyone has the facilities.
Brian. ;)
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Peter Balcombe
Posts: 1499
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
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Cliff Evans
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Joined: 29 Dec 2019, 15:13
Location: Bristol
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Re: SZD-8 Jaskolka 1/3 Scale

Post 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.
https://lasercutsailplanes.co.uk
https://patteaklegliders.co.uk
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
Mike F
Posts: 96
Joined: 18 Mar 2015, 14:08
Location: Gloucestershire

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
Attachments
Jaskolka Wheel Well Details
Jaskolka Wheel Well Details
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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.
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: SZD-8 Jaskolka 1/3 Scale

Post 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
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