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I am not an engineer,  but I have some experience. I used to optimize
racing sailboats (throw away all non-essentials, drill huge holes, spend
tons of $, save a gram everywhere, spend more$...you get the picture) .
For your consideration:   Bagging, while very labor intensive, was found
to be worthwhile under some circumstances. Mr. Herminghaus is correct
when he points out the weight savings from vacuum bagging techniques.
Additionally, the minimization of air entrapment, dry voids, and
avoiding excessively rich epoxy/glass ratios all speak to the benefits
of this technique.

The stiffness of the substrate is very important when bonding subsequent
layers of glass using bagging technique. The vacuum can "bend"
unsupported underlayments and allow the new layer being applies to
"modify" the substrate post cure.  This is usually only a problem with
very thin substrates.  Please use care to fully support all tooling.
High quality bleed cloth is a necessity to ensure a minimum of
swearing.  Increased stiffness without embrittlement, less weight, less
voids (both wet and dry), and very consistent part to part
characteristics are gained.  The consistency issue bears consideration
as the weakest link theory holds true for all stressed components.

As many of you are aware, racing ANYTHING brings out the most wild ideas
and construction techniques.  Speed costs time and money....how fast can
you afford to go? Other techniques include the use of vacuum with
elevated curing temps, autoclave, etc.

Vacuum techniques.     http://www.gougeon.com/

Also of merit is the SCRIMP technique being used to mold racing
sailboats, railroad car bodies, etc.    http://www.scrimp.com/
and     http://www.tpicomp.com/TPITechnology.html

While the SCRIMP process is proprietary,  it can be useful to the "one
off" builder for "informational" purposes.  The TPI people in Warren RI
build a line of racing sailboats called  J/24's that use the SCRIMP
process.  They are very free in offering factory tours to interested
individuals.  If any builder is in the area, that tour is well worth the
effort, and very educational.

My regards to all,   build and fly safely.

Jeffrey B. Chipetine

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Please send your photos and drawings to marvkaye@olsusa.com.
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