Repairing a Glass Fibre Fuselage Soarer

[Glider Guider]

At the Nats this year I bought a Pat Teakle PIK 20 4m soarer complete with airbrakes and five servos for the princely sum of £30 from the Sunday ‘table top’ sale. Just the airbrakes and servos would fetch more than that on Ebay so there must be a catch somewhere I hear you cry especially as a similar one has just fetched £240 on Ebay. There is a catch, unfortunately it has had a heavy ‘one point landing’ which had detached the tail and caused cracking below the cockpit as well as in one wing and the tailplane, but as I paid less than nothing for it I’m not complaining.

I have just reattached the tail and thought it might be of interest to someone and hopefully generate some discussion so here goes.

As you can see below the tail was well broken off and it wasn’t a nice clean break.

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[Glider Guider]

I decided to repair it as described at http://www.windandwavemodels.com/Repair.html by fabricating a glass fibre splint that is inserted into the two halves of the fuselage. Making the splint 6” long was convenient as I had some 6” wide wing joining glass and this gave 2” into undamaged fuselage each side of the damaged area which I thought would be sufficient to give a strong repair.

The first job was to make a plug to wrap the splint around as using the fuselage itself was not practical due to the extent of the damage. This was made from four 8” lengths of 1” square balsa glued together which was then planed down to the outside diameter of the fuselage as measured at the forward extent of the splint. By using the outside diameter there would be an overlap of the splint which would press against the fuselage both holding the splint in place and giving a better joint. The plug was then tapered over 6” of its length again to the outside diameter of the rear fuselage leaving 2” to be held in the vice as illustrated below.

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[Glider Guider]

The splint was made from three layers of glass and epoxy resin sandwiched between acetate sheets. This sandwich (including the acetate sheets) was then compressed with a wallpaper roller to expel any trapped air and then wrapped around the plug and held in place with sticky tape. After 24 hour to allow the resin to fully cure the splint was cut from the plug by using a razor saw along its length.

I wouldn’t recommend using polyester resin, although it is cheaper and it goes off faster (20 minutes against 20 hours) the result is more brittle than epoxy resin and you also want plenty of time to get things right before it goes off.

Finally remove the acetate sheets and give the splint a rub with glass or emery paper to roughen the beautifully smooth glass like finish of the splint. Although it looks nice it is not a good surface for the epoxy to adhere to when the splint is fitted into the fuselage.

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[Glider Guider]

The tail is quite heavy so there was no chance of just inserting the splint, binding it up and expecting the tail to be in the right position when the epoxy had cured so I built up a jig on a fuselage building board which is conveniently inscribed with squares which assist alignment. This held the fuselage still while I adjusted the tail position by using wooden wedges. Once alignment was correct the position of the wedges was marked.

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[Glider Guider]

The splint and the inside of the fuselage were now given a liberal coating of epoxy resin and the repair was made; all being held firm by the jig. At this point I decided to bind the repair in acetate sheet and I also made a simple gauge to check the fin was at right angles to the wing-joining rod with the aid of the Mk 1 eyeball.

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[Glider Guider]

I was concerned that the epoxy resin was very thin compared to resins I’ve used in the past and quite a lot of resin was dripping from the repair (one of the reasons I bound it) and running inside the fuselage; but nothing to be done until it had fully cured when the fuselage could be removed from the jig and the resulting strength of the repair judged.

I allowed a full 48 hours for it to cure and removed the fuselage from the jig. Although the strength of the joint seemed satisfactory I decided to reinforce it with carbon fibre tows. The joint was filled with two part filler, sanded down and a number of grooves were ground through the gelcoat until you could see the glass fibre. The tows were glued in place with cyano (superglue).

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[Glider Guider]

This really stiffed up the joint and a final application of filler and a rub with 240 ‘wet and dry’ used wet gave the result shown below which is almost ready for spraying.

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[Glider Guider]

Health Warning!!!

I couldn't finish without a few health warnings about procedures used in this repair.

When sanding or sawing glass fibre always wear a respirator.

For a while now I have had what appears to be quite bad hayfever occasionally but this didn’t seem to relate to the current pollen levels and I wondered if it was caused by cyano glue fumes. The afternoon after gluing the carbon tows the question was answered when my nose blocked up totally and started pouring also my eyes felt sore and now 48 hours later I am still suffering but things are improving slowly. On the bottle it has an irritant warning and says not to breath the fumes but I’ve used cyano for years with no problems and it’s only recently that I’ve become allergic to it.

I’m now on the look out for a respirator that guards against fumes, Screwfix have one at £2.50 or so but the P&P on one item makes it more like £7.50, and I will wear a set of goggles as well. Other people who have had this problem have apparently used a fan to blow the fumes away before they reach the face with good effect and also the low odour cyano causes less problems - but after this bout I’m taking no chances in future, it will be respirator, goggles and a fan.

Has anyone else had this problem, if so how have you got over it?

 

[adzam]

:clap3: :poster_ke :goodpost:

 

[wonwinglo]

Very informative Dave,there is a lot of good user information contained in these postings,the warnings about these cyno fumes are very real as I have heard many people say that sometimes after years of use the user can suffer,after suffering myself from a bad skin problem on my hands these past few years now I take much greater care with these products,in this case tests showed that epoxy resin was one of the irritants but after years of usung glo-fuel,dopes and various adhesives these cannot be ruled out,herbal treatment has sorted out the skin but it is a long expensive process.

Without fear mongering it is a well known fact that the constituents of glo-fuel can cause senile dementia,so please take care and use a good barrier cream and wash your hands soon as possible,do not under estimate the dangers of some of the products we use in our model making,build and fly safely.

 

[Greyhead]

Nice work Dave, with those carbon fibre tows I wouldn't mind betting it's a fair bit stronger than the original!!

Grahame

 

[orion1210]

Hi,

Your fuz repair thread has really helped me since i snapped my pat teakle ASW17 fuz in the same place.

Just wondering what paint you used for priming and final spraying... did you get a good colour match??

PLease post a pic of finished article.

Many Thanks

Ben

 

[Glider Guider]

Hi,Your fuz repair thread has really helped me since i snapped my pat teakle ASW17 fuz in the same place.

Just wondering what paint you used for priming and final spraying... did you get a good colour match??

PLease post a pic of finished article.

Many Thanks

Ben

Ben

The fuselage is awaiting better weather before I spray but I'm going to use Halfords aerosol White Primer and Spectrum top coat. When spraying I use fast thinner from the local motor factors for Spectrum and Solarlac as it’s a thousand times cheaper and works just fine. I give a couple of coats of primer which is rubbed down, then give it a quick flash over with black and rub down, by doing this you can see the imperfections as black marks which can be given a bit of filler or rubbed out.

Unless you know the original paint you'll struggle to get an exact match in white, I'm going to re-spray the whole model not just the damaged areas. You might get away with a close matching paint between fuselage and wings but I doubt that just spraying the tail section will give satisfactory results but try it and see if it stands out, you can always continue with the rest of the fuselage if it doesn’t work.

I will be posting a photo when it is finished.

I’m please my article has helped you - it makes it all worth the while.

 

[Glider Guider]

I saw my first swallow today over Swithland Reservoir in Leicestershire which means that the spraying season can’t be far away. The PIK 20 fuselage is going to be boring white so I dusted it off and gave the areas of repair a quick flash of black paint.

Why? This is then removed with wet & dry and all the minor imperfections that are normally invisible until you have just applied the final coat become easy to see and fix with a dab of acrylic stopper.

It was as I sanded away the black paint that I realised my mistake – the black paint doesn’t show up at all on the carbon tows I used for the repair, so after that stopping is applied and rubbed down I’ll give it a coat of a different colour. Now I’ve got some white paint somewhere ……..

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[George]

I saw my first swallow today over Swithland Reservoir in Leicestershire which means that the spraying season can’t be far away. The PIK 20 fuselage is going to be boring white so I dusted it off and gave the areas of repair a quick flash of black paint.Why? This is then removed with wet & dry and all the minor imperfections that are normally invisible until you have just applied the final coat become easy to see and fix with a dab of acrylic stopper.

It was as I sanded away the black paint that I realised my mistake – the black paint doesn’t show up at all on the carbon tows I used for the repair, so after that stopping is applied and rubbed down I’ll give it a coat of a different colour. Now I’ve got some white paint somewhere ……..

'Halford's' do a good spray and fill paint aswell. covers and fills any small imperfections at the same time. I have used it on model boat hulls before the final sanding. :zoo_taz:

 

[wonwinglo]

'Halford's' do a good spray and fill paint aswell. covers and fills any small imperfections at the same time. I have used it on model boat hulls before the final sanding. :zoo_taz:

*** Great stuff George,it is called 'High Build' primer,the material flows into inperfections and sands easily,it is acrylic based as well.

Nice job Dave on the fuselage,I have been listening and watching with great interest how you have gone about this job.

 

[Glider Guider]

The fuselage is now sprayed up and although the repair is not undetectable it is pretty good and only someone who knew it was there would spot it.

I sprayed it with high build primer but there were some small but deep holes that needed a dab of filler, it was then sprayed using thinned Flair Spectrum that gives good results.

I was giving the fuselage its final coat when I thought that I’d need another tin to finish off the model – that’s when the penny dropped. Flair went bust a couple of weeks ago so when present stocks have gone that’s it, no more paint, so I got on to my local model shop and managed to get one of their last tins – phew!

I’m now fitting new servo boxes into the wing to suit the new mini servos I treated myself to and then I just have to spray the flying surfaces before taking it to the hill. The PIK has a total of 9 servos so a big battery will be called for.

I’ll post some photos of the completed model when it is finished.

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[Glider Guider]

The PIK 20 is complete and ready for the slopes.

 

[Mark Townsend]

Hi really enjoyed your article on the pic 20. I have a Vaga that’s been in the shed for a number of years, wings had been solar filmed unfortunately damp has got into the later part of the wing tips causing a warp and delamination of veneer. Do you think I could glass fibre my way back into the air with this type of problem? And do you have an article waiting in the wings on the subject, as I do not have a clue about glassing a 2mtr long wing. Mark.

 

[Glider Guider]

I’m pleased you found my ‘article’ interesting Mark especially if it helps motivate you into restoring your Vega.

If I was in your position I would carefully remove the veneer from the whole wing, however if some of the veneer is still so well bonded that it won’t come off easily leave it as you must not damage the surface of the foam core. Obechi veneer is not easy to find but I noticed some on Ebay yesterday, 10 off 36” x 6” packs plus instructions on its use for £12.50 inc P&P which seems a good price. I use Copydex used as a contact adhesive to stick down my veneer, this works well but is quite expensive.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=34056&item=5987886727&rd=1&ssPageName=WDVW

I would always cover the wing with glass on a high aspect ratio wing as it gives a lot of extra strength at the expense of a bit of weight gain. To bond the glass you can either use epoxy resin or one of the new water based adhesives.

There are two water based adhesives that I know of Poly C and Skincrylic (from Falcon Aviation http://www.falcon-aviation.com). Do a search for Poly C on this board as Greyhead started a tutorial thread a while back that is quite informative.

As to which to use on your Vega? If you can remove all of the old veneer and totally recover the wing with a good bond then I would go for one of the water based products as they are nicer to use, but if you can only partly re-veneer then I would use epoxy resin as my gut feeling is that it gives more strength to the wing plus there is no chance of the water base causing areas of veneer to lift where they are not fully bonded.

If using epoxy resin apply the resin with a roller not a brush and use many thin coats as thick coats can cause disappointing results, rollers and materials are available from Fibretech http://www.fibretechgb.co.uk.

I bought a ‘started’ Pat Teakle HP-18 recently, unfortunately some not so careful previous owner has rather butchered one wing so I will need to glass it and I will write it up for this forum but it won’t be for a while yet I’m afraid. I had a word with the Falcon Aviation rep at the Teeside MFC Show and he said to lay the glass over the wing and but a heavy(ish) strip of adhesive down the length of the wing then brush this out towards the leading and trailing edges. If either the leading or trailing edges are straight then you can use one piece of glass cloth, do one side leave it until it is almost dry then turn the wing over and quickly do the other side.

Hope this helps.