wonwinglo
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- Joined
- Apr 18, 2004
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- Barry
If you have ever had to make a radial engined cowl then you know what is involved,effective cowlings for such models can be made in the following manner-
Firstly cut a disc of quarter inch balsa,this will serve as the rear of the cowl,for the sake of this exercise we will be making a 6 inch diameter example.
Now cut two similar discs for the front of the cowl and glue them cross grain with PVA adhesive,place a weight on them and leave overnight to set,the rear part of the front disc should have been cut undersized to allow for the inset of the wrap around miralyte ply we are about to add ie it will be flush,now tack glue with cyno to the front and back plate cowl ends and gently wrap and wind the thin miralyte ply arond the two,as you do this spot glue with the cyno and eventually the two halves will meet up,just overlap the ends as these can be feathered in later with fine finishing paper.
Next job is to round off the front of the cowl,first use a surform and finish off with medium glasspaper.
Now mark the front cowling rim and with a tool such as an abrafile or any internal file cut out the centre and finish the inside edges with a half round permagrit tool,the rear of the cowl will need to be cut to accomodate the rear tank installation etc or you could glue the entire unit into place and do this later.
If you want a sturdier cowl then make the miralyte ply two layers by binding tightly with masking tape as the glue sets,if you do this then dont forget to add a double recess so that it lies flush.
Such cowls can be easily cut to accomodate the cylinder head of the engine and needle valve etc,to finish off give two coats of fuel proofer (first) then add paint then trap that lot with a further coat of fuel proofer,cowls get fuel soaked very quickly hence the important attention to fuel proofing.
I have made scores of cowls this way and they have served me well over the years.
Firstly cut a disc of quarter inch balsa,this will serve as the rear of the cowl,for the sake of this exercise we will be making a 6 inch diameter example.
Now cut two similar discs for the front of the cowl and glue them cross grain with PVA adhesive,place a weight on them and leave overnight to set,the rear part of the front disc should have been cut undersized to allow for the inset of the wrap around miralyte ply we are about to add ie it will be flush,now tack glue with cyno to the front and back plate cowl ends and gently wrap and wind the thin miralyte ply arond the two,as you do this spot glue with the cyno and eventually the two halves will meet up,just overlap the ends as these can be feathered in later with fine finishing paper.
Next job is to round off the front of the cowl,first use a surform and finish off with medium glasspaper.
Now mark the front cowling rim and with a tool such as an abrafile or any internal file cut out the centre and finish the inside edges with a half round permagrit tool,the rear of the cowl will need to be cut to accomodate the rear tank installation etc or you could glue the entire unit into place and do this later.
If you want a sturdier cowl then make the miralyte ply two layers by binding tightly with masking tape as the glue sets,if you do this then dont forget to add a double recess so that it lies flush.
Such cowls can be easily cut to accomodate the cylinder head of the engine and needle valve etc,to finish off give two coats of fuel proofer (first) then add paint then trap that lot with a further coat of fuel proofer,cowls get fuel soaked very quickly hence the important attention to fuel proofing.
I have made scores of cowls this way and they have served me well over the years.