PIK20 rebuild

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

PIK20 rebuild

Post by Peter Balcombe » 14 Feb 2019, 15:23

Having designed a set of built-up wings for the PT Pik20, a friend gave me a PIK20 fuselage which had previously been "repaired" after having its tail snapped off. Also, the damaged fin had been split with a razor saw around the original join seam in order to clean up the inside of the fuselage join area.

Whoever had attempted the previous repair had used a shiny blue outer surface carbon? tube, but had apparently used an epoxy or similar glue which was still gooey in places & had certainly not bonded very well to the original polyester glass. I was able to twist out the tube in strips & then clean out the goo/harder stuff fairly easily, cleaning off further using an IPA wetted cloth to get back to clean polyester glass.
The additional external glass epoxied directly onto the top of the original smooth gel coat was easy to peel/pick off!
It also looked as if the fin post had been similarly glued as the hard brownish glue could be sliced/pinged off from the original polyester glass.
There was also an equipment mounting tray fitted in a similar way in the cockpit area. This also pulled off in one piece pretty easily as shown below.

Although I didn't get any photos of the original state, I include a few taken after I had removed the joint tube, finpost, tailplane mount, cockpit tray and as much of the joint material as i could to get back to the original polyester glass surfaces.
Apart from the rear fuselage/fin break, the forward end of the fuselage is pretty much undamaged.

My repair plans are currently:
1. Make a new polyester glass rear fuselage internal support tube, using the outer gel coat surface as a mould. This is then slit to remove from the fuselage and the slit widened to allow it to be compressed enough to slide inside the fuselage break area & be attached with polyester resin.
2. Put a lightweight glass cloth layer on the inside of each fin half to stabilise these before rejoining & then carefully refit to the fuselage over the new tube stub.
3. Once the fin has been correctly reassembled, pick off the gel coat around the joint & apply an external glass bandage before filling as necessary to achieve a smooth finish before repainting the whole fuselage once other minor damage had been repaired.

Hopefully, apart from a little extra weight, it should give a firmly bonded repair. We shall see in due course ;)
Attachments
PIK20 Cleaned parts1.JPG
PIK20 cleaned parts2.JPG
PIK20 cleaned parts3.JPG

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 24 Feb 2019, 10:33

During a gap in other build activity, I have managed to tape up the rear fuselage to act as a release layer, then apply a few overlapping layers of glass with polyester resin to make up an inner reinforcement tube.
The resultant tube was then carefully slit without much gel coat damage to enable it to be opened out slightly & released from the Fuz.
It came off nicely & the Fuz. cleaned up again.
The slit is now being widened as required to allow the sleeve to be compressed enough to be inserted into the fuselage.
Attachments
Sleeve layup_small.jpg
Tube lay-up
Sleeve off_small.jpg
Tube removed

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 03 Mar 2019, 16:56

Well, the reinforcing tube needed shortening & the slit widened a fair bit in order to be able to squeeze it together enough to fit into the fuselage (from the front!) & polyester resin bonded into place.
Meanwhile, a layer of 25gsm cloth was applied to the insides of the fin halves to back up the cracks & holes.
The fin halves were then held together using masking tape all around the seam & re-joined using some 1” wide glass tape & polyester resin.
I am now ready to fit the fin back onto the fuselage.
Attachments
D34E731B-0E24-43D6-86CB-2E7A5E467E2B.jpeg
Fuselage stub
125543B6-EF39-43A1-97D0-B3E12BB8FD3B.jpeg
Re-joined fin
16957EB6-9551-475E-AC8B-ECAA2EA8CD75.jpeg
Fin seam

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 04 Mar 2019, 11:01

Fin re-attached & a start made in removing gel coat around the break so that an external bandage can be applied over the joint prior to making good with lightweight filler.
The gel coat will probably also be locally removed to make good other major gel coat damaged areas.
Attachments
06850463-539C-4FF6-BF9F-4F3E7CBB98C1.jpeg

StephenB
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Joined: 26 Dec 2018, 08:45
Location: Hungary

Re: PIK20 rebuild

Post by StephenB » 04 Mar 2019, 12:08

Going well Peter, watching with interest as I used to have one of these and it's such a pretty aircraft. I do like a glass fus/foam wing combination too.

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 05 Mar 2019, 22:29

Thanks Stephen.
Tail joint now given a couple of layers of external glass cloth prior to filling once the resign has fully cured.
Meanwhile, the forward fuselage major damaged gel coat areas has been picked off to remove the worst & cyano run into the exposed glass layer prior to filling (thankfully none large enough to warrant external glass cloth).
I think I will add a glass layer to the inside of the forward fuselage (wing joiner to nose) just to provide additional stiffness as there are various areas where there is minor gel coat crazing & I am not going to pick it all off!
The small added forward weight is hardly likely to matter as it will be needed anyway to balance the tail repair.

Once the rear fuselage joint has fully cured, I will tidy up the remaining external fin damage by picking off the gel coat in the worst affected areas and filling. The hardwood internal tailplane support block can also be replaced using polyester resin.

The existing wing joiner & incidence pin boxes/tubes will probably have to be replaced as Murphy’s Law is sure to declare that they are in slightly the wrong place for the new built-up wing design, but that will be left until later in order to keep that area more rigid during other work ;)

More pics when I have got back to a tidy fuselage ready to move forward with normal installation activities.

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 14 Mar 2019, 18:58

Joint plus other cracked gel coat areas now tidied up and ready to paint once the wing joiner positions have been changed to suit the new built-up wings.
Attachments
19A7EEEE-25CA-4437-AB2D-DECEFD8EA4BD.jpeg

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 30 Mar 2019, 15:00

Old fuselage wing joiners were in about the right place, but were 14mm blade type, so had to be removed anyway to change to the new 15mm type :|
However, this is just as well as the previous joiner had also been fixed in place using epoxy!
Removal just needed a hacksaw blade through the middle of the joiner assembly, followed by a tweak on each half to release cleanly from the polyester fuselage ;)

New 15mm joiner strip is now available, so the previously part built wings have been extracted from their hiding place in the workshop for finishing prior to making up a new scissors type fuselage joiner box - fitted using Polyester resin.
Attachments
PIK20 fuz_wings_small.jpeg
Fuz + part built wings

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 30 Mar 2019, 15:04

If anybody out there with a PT PIK20 is able to trace around their Tailplane & Rudder assemblies & attach as 1:1 pdfs, it would be greatly appreciated.
Many thanks,
Peter

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Peter Balcombe
Posts: 892
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: PIK20 rebuild

Post by Peter Balcombe » 02 Apr 2019, 15:56

Whilst waiting for glue to dry on assembled balsa skin pieces for the top of the 2nd wing, I have decided to fabricate a fuselage scisssors joiner assembly from 2 rectangles of 1/8” ply, plus 2 pieces of 1/4 x 1/8” Spruce strip (sawn diagonally across width over the 145mm length to give 6mm to zero wedges).
With the parts glued together around 2 lengths of 15mm joiner tube, I have an assembly giving 2 1/4 degrees angle on each side.
The joiner tubes are a little over length & are only dry fitted, so can be removed to encase the assembly in glass tape/resin prior to fitting in the fuselage. The joiner tubes will be slid/fixed into place from outside the fuselage to allow them to be cut flush with the outside of the fuselage root fairings.
Once everything is in the right place, the joiner assembly will be bonded to the inside of the fuselage with polyester resin/flock
Then for wing attachment, a fully removable steel joiner strip slides into each wing/side of the joiner box, rather than have the joiner permanently fixed into the wing as for Pat’s original suggested approach.
Hardwood blocks will be fitted inside the fuselage to retain rear incidence rod location tubes at the correct dihedral angle.
Wing retention will be via Multiplex Uniloc fixings.
Attachments
FDB4D3D6-D835-4CC5-80DC-6340A240C282.jpeg
Wooden scissors box assembly
3E2E2555-6B67-445D-97EE-4CB4AFCAE237.jpeg
End - no tube
E226EA4C-668E-4B8F-A09B-305A075B1478.jpeg
End - tube in place

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