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PT PIK20 Spoiler refurb

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mjcp
Posts: 103
Joined: 29 Jul 2015, 08:14
Location: A wind swept hill with no wind, in driving distance of Windsor, UK
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PT PIK20 Spoiler refurb

Post by mjcp »

My recently acquired, vintage, Pat Teakle PIK 20 has been having some spoiler issues, culminating in the port spoiler staying extended after a landing.

After a discussion with a few like-minded individuals, a plan was hatched to try to locate the linkage in the wing, through the lower skin. Alas... there was no linkage, just a spar-cap.
IMG_1012.jpeg

Looking the top of the wing, with a side light, there was a feint outline of a small square visible. Once opened, there was an old plastic clevis visible, detached from the actuator of the spoiler.
IMG_1015.jpeg

Opening up further revealed a boxed area where the bowden cable exits, giving enough room to access the cable and clevis for work/replacement.

Easy? No... alas the spoiler was stuck /up for a reason and now that it was /down... that reason was revealed as a snapped plastic lug.

Time to replace the spoiler I think... once removed, the non working mechanism is revealed in all its (broken) glory.

On closer inspection, I realised the two arms that the spoiler blades are attached to were identical. The one at the actuator end was the one that had the broken lug, but the far end was intact; its lug was unused in the actuation process.

I then found I could push the pins through the housing to release the arms, unscrew the blades and sawp the parts around to make up working set once more.

Assembly is the reverse of disassembly (except you swap the legs)
IMG_1021.jpeg

Once re-assembled and a bit of silicone spray to lubricate, the action was great: no slop and a positive "lock" in the retracted position.

https://youtu.be/tV4tJ3nMwBw

Marc
m̶j̶c̶p̶ Marc

Hanger -
Graupner (old) K-8b, Mini Solius chuck glider conversion, UMX ASK-21, HF/Czech 2m ASW27, DG808s 4m, X-models Mini-blade, Lidl glider pitcheron.

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

Re: PT PIK20 Spoiler refurb

Post by Peter Balcombe »

Well done Marc :)

What you think is a spar cap is almost certainly the lower spar itself as Pat used to set top & bottom Ramin spars directly into channels hot-wire cut into the foam cores. There is no spar web.
However, Pat’s wings were always strong enough for normal flying, particularly if glassed with lightweight cloth.
If the brake cable bowden tube wasn’t set into a channel cut from the bottom of the wing, then Pat must have done it from the upper side (probably whichever side gave him the minimum depth slot to cut & then refill once the bowden outer had been inserted.
The broken plastic clevis pin is the reason why I always use metal clevises - otherwise it’s an accident just waiting to happen ;)

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mjcp
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Joined: 29 Jul 2015, 08:14
Location: A wind swept hill with no wind, in driving distance of Windsor, UK
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Re: PT PIK20 Spoiler refurb

Post by mjcp »

Yup! I got fed up with my solder not bonding to the old cable for replacing the clevis to metal, so a slight delay, I will be binning it and replacing with new.

Otherwise, happy with the remediation!



Since I have things in bits, I'll check the aileron linkage too (there's a mess of poor surface repair at the tip anyway) and replace any iffy looking bits there too...

Then sand back and recover, considering glass too as it is NOT currently glassed. (though that may need some assistance / outsource!)

Marc
m̶j̶c̶p̶ Marc

Hanger -
Graupner (old) K-8b, Mini Solius chuck glider conversion, UMX ASK-21, HF/Czech 2m ASW27, DG808s 4m, X-models Mini-blade, Lidl glider pitcheron.

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

Re: PT PIK20 Spoiler refurb

Post by Peter Balcombe »

Marc,
Yes, old bowden steel wire will be a big problem to solder due to oxidisation of the wire surface. Much better to use shiny new cable/wire & tin the end before making the soldered joint itself.

Glassing the wings would probably require removing the control surfaces & skinning them separately, but otherwise it’s a fairly straightforward job once you have sanded the surfaces back to give a good/smooth surface.
Use lightweight 25gsm? cloth & either a finishing epoxy (or one of the water based materials if you don’t like resin).
Modern resins are not as viscous as they used to be, so can be applied using a small (2”) foam roller or brush, rather than needing a spreader.
(Have a look at the Bucks Composites website for skinning tips) I used to get materials from them, but not sure if they are supplying at present.
Peter

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