Campy

My Feedback: (1)

I will be ready to do my cowl shortly. I had planned on doing it via the "Lost Foam" method with finishing resin and 2 oz glass cloth (3 layers). I have been hearing about all the "good" stuff from using water based polyurethane on 3/4 oz cloth for wings - will that work with 3 layers of 2 oz cloth over a foam mold for use as a cowl ? I plan on using a 2 stroke 61 and the engine will be totally enclosed in the cowl, including the muffler (I will have to cut for air flow and for
heat release).

Is this a good idea ? Has anyone ever done a cowl this way ? If it is a good idea (for strength and rigidity) will using gasoline to remove the foam damage the cowl ?

Thanks

Ollie

Polyurathane cures by evaporation. This makes it a poor choice for structures such as cowls. Use a good laminating epoxy.

The layup schedule depends on the shape and size of the cowl as well as the desired stiffness and mounting method. The beauty of the lost foam method is that you can do a trial layup, remove the foam and check the stiffness before final finishing. If the results aren't stiff enough, you can add a few layers of light cloth before final finishing.

BTW, I don't use solvents to remove the foam. I pulverise it mechanically and sand off the residue. It's easier than you might think and not as messy, smelly, expensive or likely to interfere with adding more glass cloth.

aircav82

I tryed using two layers of heavy glass cloth and water based poly. The cowl was not near stiff enough. I think the epoxy would have been a better choice. Now i have to carve another cowl.