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Help with repairing cowl

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Cliff Bastow24/09/2016 11:42:45
824 forum posts
426 photos

Hi all,

I have been given a 25 year old model of a P40 which is in generally reasonable condition. however it has a large plastic cowl which is curved in two directions. this is damaged with quite a large section missing on one side.

I know several ways to patch this but what I cant see is how do I get the right shape? I cant use the other side to make a mould as obviously it is a mirror image.

I am sure someone out there will have the answer.

Thanks in advance,Cliff

Geoff Sleath24/09/2016 12:19:54
3300 forum posts
251 photos

You could carve a blue foam model of the whole cowl and use it to make a new fibre glass one. Or use the foam cowl inside the existing plastic one to help you to shape the repair. I'd go for making a new cowl.


Phil 924/09/2016 12:42:31
4281 forum posts
224 photos

there are a few different p40 models and plans out there. It may be possible to find a cowl that will fit and just buy a new one.

look at cowls in my hobby store or traplet

gangster24/09/2016 13:45:33
941 forum posts
16 photos

Repairing cowls can be very doable and very rewarding. The last one I repaired was a really flimsy abs job. I used the fine glass cloth and epoxy resin that you use to glass cloth wooden models. Whilst you cannot use the othe side as a mould you can use it to make card or balsa templates to check the profile Someone suggested a blue foam mould but you can also use foam inside as a support cutting away afterwards even temporary balsa ribs or block inside to hold the glass out. Maybe laminate balsa inside and out and carve to profile. Grinding most of the wood away afterwards. On each successive layer of glass even if you sand most of it away you will be getting closer each time. Then a layer or two of the glass cloth over the lot. Bear in mind though if you have to buy the materials especially for the job it will cost more than a new cowl. But if unavailable the only option is to mend

Bob Cotsford24/09/2016 14:57:32
7931 forum posts
436 photos

There's a good chance that it will be the old 'Red Box' TopFlite P40 at 25 yo. Would it be simplest to get your hands on the later Gold Box version cowl which is still available, or even the 60 ARTF cowl?

I just happen to have the older Red Box kit waiting to be built, if you get really stuck I could lend you the cowl from that to take a plug from.

If you measure the span and length and supply a few other details it might be possible to tie down which version it is - for example the Red Box one has fixed U/C and sheet tail surfaces while the Gold Box version has retracts and a built up tailplane.

Red Box - 60" span, Gold Box - 65"

Edited By Bob Cotsford on 24/09/2016 14:58:58

kc24/09/2016 18:34:08
5962 forum posts
168 photos

The plan for the Top Flite P40 is available to download on Outerzone That might identify your model.

The plan has instructions for the cowl which seems to be a plastic lower part with balsa block top.

Allan Bennett24/09/2016 20:37:30
1534 forum posts
39 photos

The way I've done it in the past is to install a fibreglass patch where there's a bit missing, and then, when set, plaster it with P38 and sand it until it's the right shape. You can make a cardboard template from the good side to check the curvature of your repair. Then, after sanding everything smooth and painting it, I applied release agent and made a female fibreglass mould, from which I eventually made a replacement fibreglass cowl. I keep the fibreglass moulds in the shed in case I have another accident. I've already used my Magnatilla cowl mould twice for replacements!

Cliff Bastow24/09/2016 21:11:49
824 forum posts
426 photos

Some good ideas there chaps, many thanks to all.


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