How to create LARGE fibreglass molds/parts??

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Johnnycrash
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How to create LARGE fibreglass molds/parts??

Post by Johnnycrash »

Hey all,

So, some time ago (years), I got this idea in my head. It all started with research for a much desired project. That project has almost come to fruition (taking longer than expected, again sorry to all those involved). The research, with a little bit more work, lends itself well to a MUCH larger project.

I am now working up the new larger plans needed. Still a fair bit of engineering to do, and source some hard to fins parts, and things... It is looking more and more viable. But... To make it really doable (and maybe repeatable), many elements will need to be mastered, molded, and cast.

The parts I am looking at duplicating are bigger than your average model parts (even for studio scale stuff). The three parts that I have so far that will need casting measure out as follows: 1) 38" roundish x 38", hollow, with inner and outer detail. 2) 30" disk x 15" that fits into part #1. And 3) 30" disk x 4". Part #1 is smooth inner and outer (but with one undercut), parts #2 & #3 are one sided, but contain many thinner fins and rings that stick out from the surface. They are not supper thin (3/4" x 2 1/4" deep), so getting material into them will not be an issue (I think).

To do these, the idea is to make a master out of whatever works, make a set of fiberglass molds, and then cast them in fiberglass in those molds. While I understand the principle in this method, I have not made BIG molds or parts like this before. Mold release becomes VERY important in this, I know that. Usually a wax based product.

For part #1, I was thinking of two molds/parts that are then joined together in a jig. They can either be, for the final product, set up over a wooden frame for the, or filled up expanding foam. The jig would hold the parts stiff, so the foam would not distort the part. I guess parts #2 & #3 could be back filled with foam as well to make them strong and less susceptible to damage.

Thoughts?? Ideas?? Advice?? Links to more info??

Thanks in advance guys. :D
John Fleming
I know that's not what the instructions say, but the kit's wrong anyway.
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Rogviler
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Post by Rogviler »

I'm afraid I don't have any good links for how-tos, but it sounds like what a lot of guys do to make new bumpers and hoods for cars. For instance (small example):

http://www.youtube.com/watch?v=uB-2_pM7HFo

That's the direction I would be looking anyway. I've seen some pretty complex shapes done with multi-part molds, so it's definitely doable.

-Rog
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Johnnycrash
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Post by Johnnycrash »

That's exactly what I meant. The panels and such are bigger than most car panels, but the principle is the same. I'm thinking I may divide part #1 into left/right halves, or top/bottom. Which ever is best to hide the seem work after. That would make the master, and molds, more manageable. Parts #2 & #3 I can build in the house, but part #1 as a one-piecer... Nope. I only have 32" doors. :shock:

YouTube strikes again. Should have been able to think of that myself. :oops: Thanks for the link Rog.

And I do need to brush up on fiber glassing in general. To give this the best chance of surviving in the real world environment (mostly plywood construction), it will need to be completely covered in a layer of glass.
John Fleming
I know that's not what the instructions say, but the kit's wrong anyway.
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Umi_Ryuzuki
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Post by Umi_Ryuzuki »

Here is a nice build up of a boat hull master and mold.

Finish work takes place on page 3 and 4.

Mold set up on page 5.

http://www.rcgroups.com/forums/showthread.php?t=1721619

:)
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modelnutz
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Post by modelnutz »

FYI...urethane works real well with fiberglass....no polyester fumes to deal with.
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Johnnycrash
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Post by Johnnycrash »

Umi_Ryuzuki wrote:Here is a nice build up of a boat hull master and mold.
Very informative. Thanks. Some nice work going on there. He makes it look easy.

modelnutz wrote:FYI...urethane works real well with fiberglass....no polyester fumes to deal with.
Ah, yes, urethane over polyester. All the time if possible. I HATE polyester. Yucky nasty stuff that. Ugh!!


I am now thinking, after having looked at some of the links and thought about it more... The 2 30" disk parts may be best done as just cast foam. They will be mostly out of the elements, and non-structural. As long as they can be painted...
John Fleming
I know that's not what the instructions say, but the kit's wrong anyway.
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Johnnycrash
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Post by Johnnycrash »

Having now watched hours of YouTube videos... I know more than I did before. I'm not sure if that's good or not. I have done some fiberglassing before, but in limited sizes and applications.

Seeing that it's much easier than I was worried about (I mean, sure, it still takes skills and such, but not like I was fearing), it has given me ideas. Oh god, run for the hills. :shock: And I am having a major re-think on the whole project.

My engineering was based on construction mainly from plywood, skinned with multiple 1/8 sheets, and then a final cover of glass (the sea; it up and protect the wood). And only certain parts that I needed multiples of (that where big), I would mold and cast in fiberglass. Now, I am thinking that for repeatability, the ENTIRE thing could be molded and cast as panels. But now, that means the structural system has to be completely re-thought. Ugh!!

I want this to be a tactile experience, not just something you look at from 20 feet away. While the glass panel idea makes it easier to replicate, and lighter, it also makes it less structural in terms of people climbing on it. Ugh!!
John Fleming
I know that's not what the instructions say, but the kit's wrong anyway.
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