Bladder split-mold vs 2-half vacuum bag and joining

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#1

So I’m looking to build a bike frame whose tubes aren’t necessarily round, but they should have side angles positive enough for removal from a mold. My main concern is this: is there a significant strength loss from creating something like this from 2 halves and then joining them down the middle? Obviously the method of joining would be important, but I just want to make sure that it wont catastrophically fail due to a flawed assumption on my part and it will be just as strong in the proper directions.

Any input would be greatly appreciated! Bladder split-molding is an option, but it would be fairly complicated and expensive on a per-try basis, so if it’s possible, I’d much prefer doing it in two halves, split vertically through the center.

Sorry I don’t have a picture of the actual frame, everything has been molded by hand, but it’s extremely similar to this Audi electric bike frame and is just for personal use.
http://www.electricbikee.com/wp-content/uploads/2012/09/audi-11.jpg

#2

I think it would help if you described what materials your using, are you leaving the frame hollow or will you use a core material? Resin system ?

#3

If the seam between the two halves is constructed properly then the seam will not be the weak point. A co-cured seam is best.

#4

Thanks for the replies!

So far, the plan is to use 2x2 twill, probably 3k, and some epoxy that my brother bought when he worked with fiberglass for a school project a little while ago, I don’t really know the specifics on that, though. I was going to wet lay-up into a female mold and then vacuum bag it in two halves, split vertically from front to back.

What did you mean by co-curing?

#5

Co-cured means that the seam and the layup are all cured together during one curing session.