Cowling bump

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Jim Alex
Posts: 47
Joined: Sun Feb 17, 2008 9:00 pm

Cowling bump

Post by Jim Alex » Wed Oct 23, 2013 8:15 pm

Does anyone know a source of aluminium or fibre "power bulges" to fit to a cowling?
Jim Alexander
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johnmichie
Posts: 57
Joined: Wed Jan 07, 2009 10:35 am
Location: White Waltham

Re: Cowling bump

Post by johnmichie » Thu Oct 24, 2013 12:09 am

Jim

mold the speed bulge with modelling clay or glue on and carve and sand styrofoam. Make it as smooth as possible and cover with thin strips of parcel tape. This acts as a release agent. Then cover with three or more layers of glass cloth and resin. When cured pop it off, remove the clay/foam, clean up the bump and fix in place with resin/ glue/rivets.

This method using a male form gives a rough outside and requires much more filling/rubbing down than a female mold, but it is very cheap.

PM me direct if you would like some pictures or to talk.

John
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Ian Melville
Posts: 1000
Joined: Mon Feb 11, 2008 7:21 pm

Re: Cowling bump

Post by Ian Melville » Thu Oct 24, 2013 8:58 am

Like John I would just knock one up myself as it is more likely to fit the cowl. Or you could try one of these
http://www.honeybournemouldings.co.uk/f ... bulges.htm
Ian Melville
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Jim Alex
Posts: 47
Joined: Sun Feb 17, 2008 9:00 pm

Re: Cowling bump

Post by Jim Alex » Fri Oct 25, 2013 8:52 am

:D Thanks guys.
Jim Alexander
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Adrian Hatton
Posts: 31
Joined: Sat Jul 05, 2008 9:22 pm

Re: Cowling bump

Post by Adrian Hatton » Sat Oct 26, 2013 4:47 pm

Jim,
If you do make your own 'bump', it is worth using some decent epoxy resin and 2*2 twill glass cloth - once it is cured at room temp then post-cure it as per resin recomendation to reduce the risk of shrinkage due to engine heat bringing the cloth weave to the surface after you have painted your pride and joy cowling.

Post curing can be surprisingly effective and requires lots of heat for a set time - e.g We commonly use Schuefler L285/H285 resin systems for glider repairs and the usual post cure is at 54C for 18 hours (but can be as high as 80C on some applications).

Severn Valley Sailplanes carry good stock of GRP repair materials:-

http://svsponline.co.uk/Composite-Mater ... d-Repairs/


Hope this helps

Adrian

cardiffrob
Posts: 370
Joined: Wed Jan 16, 2008 3:56 pm

Re: Cowling bump

Post by cardiffrob » Sun Nov 10, 2013 5:43 pm

Image


Image


If anyone gets stuck, I make stuff like this for vintage cars. No big 'charge'...just the cost of materials and postage. (unless you have any Austin Seven spares!) :D

A few other pics on the website shown above.
Rob Thomas
Nr RAF St Athan.
01446 795489
Rob Thomas
034851

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