| Re: [GMCnet] Why not just build new ones? [message #154391] |
Sun, 25 December 2011 23:54  |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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I believe that fiberglass casts evolve over time with gravity/curing/shrinking as voc's leave the resin and their shape will take a set in whatever static rest they end up in after leaving the mold. Also, making a mold of a finished part will yield a slightly smaller finished part than the part used to make the mold due to shrinkage during the curing process. I think that is part of the reason most early after market auto body parts were such poor fit. Ever throw an after market fiberglass hood on a car? D.F.F.S. Molds made from existing finished parts might work but the tube it fits to will need adjust ability for good fit or mold will need to be sized to compensate for shrink I think.
Sully
77 royale
------Original Message------
From: Russell Mehlenbacher
Sender: gmclist-bounces@temp.gmcnet.org
To: gmclist@temp.gmcnet.org
ReplyTo: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Why not just build new ones?
Sent: Dec 25, 2011 8:19 PM
Shortly after we bought our "74, we took a ride out to Cinnabar in
Sandusky. They have, on the shelf, a front end mold. They have used it, but
the comment from the shop staff was that it took an incredible amount of
labor to fit to a coach. Maybe they didn't know how to fill the mold,
but I got the impression they weren't doing it again.
Russ
Russ & Linda Mehlenbacher
Rochester Hills, MI
'74 X-Sequoia
'76 Eleganza
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Why not just build new ones? [message #154427 is a reply to message #154391] |
Mon, 26 December 2011 14:08  |
Greg and April
Messages: 263
Registered: December 2011
Karma: 0
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Senior Member |
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This is more of an issue with FRP's based on older polyester and vinylester
resin formulas, because some drying of the resin occurs, as it cures.
Epoxy based resins are the most stable, and once they finish curing (
especially those that are based on elevated heat or UV based curing ) there
is nothing to off gas.
Early aftermarket parts, often used the lowest cost resins, that would be
subject to deformation, due to heat and/or internal support. Another
problem was the excessive use of low labor cost chopper guns and not enough
use of glass roving and glass cloth lay-ups, which improve overall
directional strength, leading to deformation just from it's own weight
and/or the weight of other parts stacked on top.
Greg H.
"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."
Doctor Zhivago
----- Original Message -----
From: <sgltrac@gmail.com>
To: <gmclist@temp.gmcnet.org>
Sent: Sunday, December 25, 2011 22:54
Subject: Re: [GMCnet] Why not just build new ones?
>I believe that fiberglass casts evolve over time with
>gravity/curing/shrinking as voc's leave the resin and their shape will
>take a set in whatever static rest they end up in after leaving the mold.
>Also, making a mold of a finished part will yield a slightly smaller
>finished part than the part used to make the mold due to shrinkage during
>the curing process. I think that is part of the reason most early after
>market auto body parts were such poor fit. Ever throw an after market
>fiberglass hood on a car? D.F.F.S. Molds made from existing finished parts
>might work but the tube it fits to will need adjust ability for good fit or
>mold will need to be sized to compensate for shrink I think.
>
> Sully
> 77 royale
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