Cowl bumps

My latest scratch project is a Stinson Model A (tri-motor). Each of the cowls has 18 bumps for the rocker boxes on the radial engines. Don’t fancy making all those teardrop shaped bumps. I was thinking of making a pattern and doing resin castings for the second and third cowl. Still, don’t like the idea of even having to make 18 of those little things. Each is a little over a quarter inch long by about fifty mils wide. Any idea of any existing product- like something from a craft store or something- that would eliminate having to make these little suckers?

A picture of what you need would help us a bit. if the bumps are close together you could always make one long piece in that shape and just put an indent between to simulate separate parts

my suggestion is to get some styrene half rod in the proper size, then cut to length and file to shape.

Yeah, that is my backup procedure. I was hoping someone else had an easier way to make 18 of these little things (they are small, fifty mil wide). And, to answer another post, they are bump outs (standing above the rest of the cowl), not depressions. My plan, if I do make each one from half round, is to keep them solid. I may have to grind the rocker boxes off the engines, but that is okay, they are not visible on a cowled engine anyway. I had thought to maybe make three or four, then an RTV mold to cast, in several batches, the remaining ones, but that is still a lot of work.

So far, I’ve only found two ways of doing this,…Evergreen half round rod cut to length, and sanded to shape. Second,…Strut stock, (The kind with tapered airfoil shape), cut and sanded to shape. Good luck!..Its a tedious pain in the you know what! I don’t envy you! Dave.

Carve or sand the shape you need (slightly smaller than actual size) from wood and then heat some styrene sheet (over a candle or using a heat gun) and stretch the heated sheet over the carved shape. Then trim the edges and you’ll have a hollowed ‘bump’ you can glue to the cowl. Repeat as many times as you need.

Hey, that is a great idea! Thanks.

It’ll have to be thin styrene, since the bumps are about fifty mils high, but I do have some ten mil styrene, so I’ll give that a try. Thanks.