jetpack

My Feedback: (1)

How do I take kit supplied vacuum-formed parts or sheets and make a durable mold for making fiberglass copies? Nose cowlings, wheel pants, fairings, ect......

These are small items I would like to try and duplicate, usually found in rubber powered kits. If it is simpler to accomplish this using a vacuum table I guess I could go through the building of one, but think makes more sence to keep just a small pattern and be able to paste one up with glass wouldn't it?

scalebldr

My Feedback: (7)

you need to make a mold of the inside of the part.for vacum forming i have used plaster of paris but have found that though it feel smoothes when the hot plastic covers the plasrer small pockmark develop from heated air in the plaster,i have heard that clear coating with poly u will solve that problem but have nut tried it.another substance to make a muld/plug for your purpose would be bondo ,but you need a negative type mold for best results/if you use a positive mold i would suggest using the petit hoppypoxy easy does it method,where you fit a ballon over the finished layup to get a smooth finish when the epoxy cures.

Countryboy

My Feedback: (25)

Durham's Rock Putty
http://www.waterputty.com/

Very hard & durable once cured. Great for forming canopies, cowls, etc...

jetpack

My Feedback: (1)

If I use water putty to form a mold, do I just simply lay the sheet face up (detail side up) and build a box around it and pour in water putty? Do I need form release of some kind? What about when I go to fiberglass? Do I need to wax it or spray it?

kdheath

If you want to make some killer composite parts, one of the masters at making molds and such is Windy Urtnowski. It may be a little more than you're looking for, but worth thinking about. He uses two-part RTV silicone rubber for molds. Give him a buzz and he can fix you up with tapes of all the info you can possibly use.
http://www.windyurtnowski.com/
[email protected]
Phone 201 896 8740
Fax 201 896 8740

Windy Urtnowski
93 Elliott Place
Rutherford NJ 07070
USA

Countryboy

My Feedback: (25)

jetpack,

You have the box part correct, but pour the water putty in from the back side (cavity side). You will not need to wax the vacuum formed sheets prior too pouring in the water putty, because as the putty cures, it will shrink slightly. You will have to prep (Wax & PVA) the formed water putty mold just like any other mold when you do the glass lay-up for the actual part.

Countryboy

My Feedback: (25)

jetpack,

Got a couple of pics for you showing a plug made from the water putty. The part is the detailed ABS supercharger covers that go on a KMP P-38.

In the first pic, you will notice the small holes drilled in the corners of the recesses...this is so that the vacuum machine can pull the heated ABS sheet down tight in the corners. You can also see that bondo has been used to smooth any imperfections in the hardened water putty plug. In the second pic, the top part is the actual ABS part that is formed over the water putty plug shown at the bottom.