Building 1/12 scale radial engine cowl
11-06-2017, 07:37 PM
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Building 1/12 scale radial engine cowl
My plans from the 70's call for the cowl to be built using the "balloon method" Anyone ever heard of this and how it is accomplished?
Last edited by skoda450; 11-06-2017 at 07:38 PM. Reason: misspelled word
11-07-2017, 05:01 AM
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That technique showed up in several build articles in magazines back then. You start with a male plug. Lay the glass and resin on the outside of the plug. Then get a balloon and blow it up and pinch off the nozzle(???). Next force the balloon over the glass and plug while slowly letting the air escape from the balloon. You should end up with the balloon tightly stretched over the layup. I never did do this myself.
Chuck
Chuck
11-07-2017, 12:03 PM
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That'a what I thought. It sounds like a great way to limit the amount of work needed on a one-off mold like this. I have the male mold built and some 12" balloons. The process almost works on a dry run w/o resin/fiberglass on the mold. I think the balloons are too small as the plug is 5" across and 4" long. I can get the balloon to about 2/3 down the plug but I can never get it to cover the whole thing when the air is let out.
I think before before I go too much further I need to try a mock-up with resin/fiberglass to see if the balloon does release when the epoxy is cured. If not, this process is flawed and I will need to go another route.
I think before before I go too much further I need to try a mock-up with resin/fiberglass to see if the balloon does release when the epoxy is cured. If not, this process is flawed and I will need to go another route.
11-07-2017, 01:35 PM
#5
That'a what I thought. It sounds like a great way to limit the amount of work needed on a one-off mold like this. I have the male mold built and some 12" balloons. The process almost works on a dry run w/o resin/fiberglass on the mold. I think the balloons are too small as the plug is 5" across and 4" long. I can get the balloon to about 2/3 down the plug but I can never get it to cover the whole thing when the air is let out.
I think before before I go too much further I need to try a mock-up with resin/fiberglass to see if the balloon does release when the epoxy is cured. If not, this process is flawed and I will need to go another route.
I think before before I go too much further I need to try a mock-up with resin/fiberglass to see if the balloon does release when the epoxy is cured. If not, this process is flawed and I will need to go another route.
Fiberglass Specialties Inc Catalog
under the "cowl & accessories for plans" page.
