Largest Piece Or Smallest Piece First When Laying Fibergla..

>
> dog wrote:
>> This is rather bad advice. In almost all cases, you WANT THE RESIN AND
>> PATCH TO BOND TO THE CORE. Putting plastic between the core and the
>> resin leaves a void too, just not one filled with gasses. Most cores
>> DO NOT react to Epoxy by dissolving and gassing off... especially if
>> the core is a good end-grain balsa, which it is on the better boats.
>
> Not tostart an argument, but there are many foams to choose from and
> some are lighter & stronger than balsa.
>
>> ... If the core is not bonded to the repaired area, you have
>> effectively created a section that is pre-delaminated.
>
> Yeah, that was kind of what I thought too. But you have to keep in
> mind, everybody wants something different.
>
> DSK

Yes, there are many foams to choose from, but few have the same
characteristics that make end-grain balsa such a good core material.
Few of the foams bond and wick epoxy resin as well as end-grain balsa.
Few of the foams have the compressive and sheer strength and resistance
that end-grain balsa has. Few of the foams have the high temperature
resistance to softening and deforming that balsa has. To date, nothing
that I have seen is better than a good end-grain balsa for most
applications. There are a few high-tech honeycomb materials that are
almost as good, but they're generally far more expensive and difficult
to work with than end-grain balsa.
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dog wrote:
> Yes, there are many foams to choose from, but few have the same
> characteristics that make end-grain balsa such a good core material.
> Few of the foams bond and wick epoxy resin as well as end-grain balsa.

Are you looking for bond strength / peel resistance? Some
foams are better in this regard.


> Few of the foams have the compressive and sheer strength and resistance
> that end-grain balsa has.

Now that's just plain wrong, it is very easy to find foam
that is better in these characteristics. The question is,
can you find better foam that is still lighter, and also
doesn't cost a lot more?

Look into the specs on foam in the 20# and up range.


> ... Few of the foams have the high temperature
> resistance to softening and deforming that balsa has.

Considering the temp characteristics of epoxy, I don't think
this makes much difference. OTOH it is possible to use
fire-retardant foams... balsa is wood after all, and will burn.


> ... To date, nothing
> that I have seen is better than a good end-grain balsa for most
> applications.

That statement leads me to wonder how far you've looked.

> ... There are a few high-tech honeycomb materials that are
> almost as good, but they're generally far more expensive and difficult
> to work with than end-grain balsa.

It's true that balsa is relatively inexpensive and easy to
work with. I like it... but for my ownpersonal super boat
project, I picked a type of foam that a friend used in
airplane kits. Has some drawbacks, but I have no doubt that
it will be lighter and stronger than balsa... and it won't
ever ever ever rot.

Fresh Breezes- Doug King
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Brian D wrote:
> You mean like using a boat as a male form and the shrink wrap plastic as a
> mold release? Boats have been used as male forms before, but I can't say
> that I've seen anybody using plastic as a mold release.

Done it myself. Works like a champ as long as the hull
doesn't have any re-curve that locks the new la-up to the
old hull.

> .... Generally, the
> lay-up needs to be flexible or in more than one part however, else you may
> not get it off the form. Mold release or not.

Bingo!

> ... Be sure to take pix!
>

And post links to them here. It always makes the day a
little better to see what other people are up to.

DSK
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Jim Conlin wrote:
> What Lew said.
>

What I like is the tactful way he says it

DSK
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