What to use for the mold?

Hi guys I am new here looks like a very informative site.

What I am looking for is some information on building a small mold for vacuum bagging carbon fiber parts.
I plan on doing this on a boat I am building but first will practice on some simple parts for probably Jet Ski’s and motor cycles and use glass at first. I have a pretty good concept on the vacuum bagging of parts but what I still need more information on is creating the mold I have a hood I can copy for a test but what would be the best product to cover this hood in to make a mold plaster?

Thanks,
Mark44

 

Hi Mark

There's more than one way to skin that cat. Not to cast any discredit on boatdesign.net forums or its members, there's plenty of good advice and a tremendous amount of knowledge here but this site specializes in just what you're looking for. www.compositeforum.werksberg.com Hopefully I won't get into trouble for posting that link, not meant to take any members away from here.

Rick

 

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Thanks,
I will look into that!

 

What to use for a mold--fiberglass of course!!!

Yo mark44: bud, just use fiberglass mat..and a little plywood.
1st: see that metal thing your "cowl" is setting on.....put a piece of plywood between it and your cowl, now put a hole in the plywood, so that the cowl slips through the hole. So what you have is something like a wooden picture frame....OK.
2nd: spray some pva(mold release) on your cowl.....three coats should do it.
Do the blue side that says Yamaha............
3rd: start laying up some mat 1oz on your part. 4 layers is good. Cover all of the blue.
Don't let the mat hange over into the inside
4th: now lay on big sheet of wetted-out mat on your part and plywood frame.
In other words, drape the wooden frame and cowl with a sheet, tuck in the sides and try to
keep it, the mat, as close as you can....
___the plywood frame makes your flange for your vacuum bag..
5th: flip your part over and take it out of the mold.
6th: take some bondo(automotive filler) and fill any voids between the mold and the wooden frame.
7th: put a light coat or resin over the plywood and bondo......but don't get it inside of the mold......
________________Let's try it out_____________________
a). shoot 3 coats of pva inside your mold
b). shoot some gel-coat in there
c). lay in some mat
d). wait for kick and remove part.
________these are the steps that I use, you are going to need to practice so you can refine the process for your self, i.e more glass for a stiffer mold, more gel-coat or no gel-coat. More Bondo for filler of no bondo......wider flange, round flange it's all up to you. But the 7 steps above will work....just make sure there are no Negative planes on your part of you won't be able to get it out of the mold.........You understand the need to a two part mold right.....In other word, the angle of all the slops have to be negative fro the opening of the mold. For example, If you fill a paper cup with water and freeze the water....you can get out the ice. Why, the angle of the walls on the cup don't turn into a positive angle from the bottom to the top....Think of this. If you froze water in a wine bottle you would have to have a two part mold. Why, well, two reasons. First, the ice is to large to fit through the wine bottle opening and, second, the bottle has a curve in the top. That is why you would have to cut the wine bottle in two, hence two part mold, and flange it, hence the plywood picture frame I was talking about earlier....get it......Check out some You Tube mold making stuff also.....