Thanks, guys.
- Doug
-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Frank Pittelli
Sent: Thursday, July 09, 2009 8:49 AM
To: [email protected]
Subject: [TANKS] Re: fiberglass molding questions
Doug Conn wrote:
> I finished my turret mold, but I had some problems. I could NOT get the
> plug out of the mold. I tried everything before I finally got it out.
Lesson 1: Always use more wax and mold release than you think is
necessary. The larger the part, the more time you should spend putting
on mold release.
> First, there are some rough spots where I gouged the mold trying to
> release the plug. These aren't too deep and I think I can just sand them
> down.
No real problem. Gouges in the mold will be "raised" areas on the
molded part, which are easily sanded off. So, after you have prepared
the mold to make a part (e.g., wax, wax, wax, wax, wax, wax, mold
release, mold release), simply squeeze some modeling clay into the
gouges and wipe smooth with your finger.
> Second, I drilled a couple of holes in the top of the turret so I could
> press the plug out using a medieval torture looking apparatus I built.
> My plan is to turn down a couple of UHMW plugs to fill the holes when I
> make my parts. Then, I should just be able to pop the plugs out and use
> the hole to push the part of the mold. Does that sound reasonable ? Any
> better ideas ?
Sounds reasonable, provided that you put plenty of wax and mold release
on the plugs. Also, be sure to use some clay around the plug joint so
that resin doesn't creep into the crevice and make them a permanent part
of the mold.
> Third, there are a few places where the fiberglass has split or been
> damaged. See the red rectangles, below. Can I just reapply some resin to
> fix those spots ? Is there a solvent I should try on them ?
It's best to strengthen those spots from the outside of the mold, so
that you don't ruin the inside surface. In that case, sand hard with
heavy grit and use epoxy and fiber to make the external patch. On the
inside, use clay to smooth out the inner surface before molding.
> I'm racking the whole mold making encounter up to a "learning
> experience". I know some things I'll do differently next time.
You can read all the books you want, but until you've gotten your hands
dirty trying various building techniques you can't really learn the real
lessons. Besides, who wants to be perfect at one thing, when you can be
half-proficient at lots of things :-)
Frank P.
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