What to use for the mold?

[Mark44]

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

[KnottyBuoyz]

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

[Mark44]

Thanks,
I will look into that!

[ratrace2]

Originally Posted by Mark44

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

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.....