Cowl

[Diamond Geezer]

Hi peeps

Need some help how do I make a balsa ring for the front of the cowl broke it with a heavy landing.tia

[Allan Bennett]

What material is that -- aluminium, firbrglass, plastic?  It would help if we had some idea of what the front should look like.

 

Since it looks like the remaining piece is meant to be unfastened to remove it from the model, is the front ring meant to be a plug that fits into the piece in the photo once it's installed and closed up?  If so, I think I might form a ring of, say, 1/16" balsa to fit snuggly inside the closed-up cowl by about 1/4", then build it up with further layers of balsa that can then be sanded down to form whatever curve is required.

 

I only say that because you mention balsa.  My preferred solution would to be to use fibreglass to build up a ring, or even to make a complete new cowl.  That would entail making a mould first, probably out of balsa.

 

 

[Diamond Geezer]

Hi  Allan

The material is aluminium and yes the front is a plug that is meant to fit into the cowl when it’s screwed together I mentioned balsa because the one that came out was made from balsa.

[Paul De Tourtoulon]

I can't see it properly but if you tape up the inside of the cowl ( so that the resin won't stick ) then tape the cown in place to the fuselage then run a band of fibreglass on the inside over lapping the firewall that will give you something to screw into.

[Diamond Geezer]

Hi Paul

thanks for the reply that is not the problem it’s the other end,the front end as it were it had a balsa ring fitted to the front end which fitted inside the cowl and was about 3/4 x 3/4 

[Eric Robson]

One way of building up a balsa cowl ring is to use segments of balsa, your 3/4" cowl would be built up with 3 layers of 1/4" balsa. I use as many offcuts as possible,

Draw a circle the size required and also the inner circle, divide it into segments and use the pattern to cut the balsa segments glue the first layer flat on the board and build the other layers with the joins offset from each other, use aliphatic glue to avoid ridges then sand to shape when dry.

[Diamond Geezer]

Thanks Eric.

[kc]

The techniques for this type of cowl and much more are shown in Peter Hollands book 'Model Aeroplane Building Sketch by Sketch' which is available to download free from RCLibrary.  He suggests building the balsa onto a ply ring.  See page 76.    Worth buying this book when it comes up on Amazon at a reasonable price -often about 3 pounds with postage. Currently £2.69 for the older version which I think may be best as it may be clearer.

 

You could also consider using 1/64 ply for the outer surface too, as it bends easily if the grain is correct.

Edited July 4, 2022 by kc

[Diamond Geezer]

Hi Kc

thanks for the info ordered the book

[DaveyP]

I've been watching this thread with interest, and have now also ordered the book  ?

[kc]

I don't think you will be disappointed with that book - it's full of Peter Holland's great drawings which explain all the classic aeromodelling techniques.    Watch the amazon price rocket now several have been sold!   Wait a few weeks and it will probably drop back again.