[Public-list] Kevlar

[Roger L. Kingsland]

Thanks Jay, great stuff; just what I needed.  I have used alot of the West 
System and will stick with that (no pun intended).

Roger

----- Original Message ----- 
From: "J Bergquist" <jbergqui at gmail.com>
To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
Sent: Wednesday, November 01, 2006 2:57 PM
Subject: Re: [Public-list] Kevlar


> Roger-
>
> It depends more on the resin than on the cloth. Kevlar is usually 
> laminated
> with either vinylester or epoxy because polyester does not work very well
> with Kevlar. Epoxy is the best of the three in terms of material 
> properties
> (waterproofness, elasticity modulus, and stickiness or 'quality of bond').
> It's also the most expensive. Vinylester is in-between, and polyester is 
> the
> low end.
>
> Epoxy will stick to any of the other resins, if the surface is properly
> prepared.
>
> Not everything will stick to epoxy, though.
>
> Therefore, your safest bet is to use epoxy. The advantage is that you can 
> be
> pretty sure it will work just fine. It also is 100% solids so does not
> shrink, whereas styrenated resins (polyester and vinylester) will shrink
> because they give up styrene to the atmosphere. This can be an issue when
> you are using polyester as a resin when adding on to a pre-existing part
> (the new resin shrinks while the old part won't). This is a bigger issue 
> in
> bigger parts so for a small part like you are talking probably not too 
> much
> of a problem.
>
> The downside of epoxy is that it's more expensive and more difficult to 
> use
> than either polyester or vinylester. You have to mix it in very careful
> proportions but with modern systems this is not as much an issue as it 
> used
> to be because they are pretty idiotproof, using pumps to dispense precise
> quantities.
>
> I like to use West System, but it is more expensive than MAS, Barrier, or
> System3, which are other brands. I have never had a batch of west system 
> not
> cure on me. I have had problems with Barrier. I have little or no 
> experience
> with MAS or System3. There are lots of other brands too. I feel that you 
> get
> what you pay for. If it doesn't kick, it's a gooey mess that is a pain to
> clean up and a waste of time, so I feel that, particularly for a small 
> job,
> get the good stuff is good economy.
>
> Material properties are probably not really an issue for your application
> and I guess cost probably is not really that big a deal either because you
> are not going to use much of the stuff.
>
> One thing to be concerned about when preparing a kevlar surface is that it
> does not sand well. Kevlar is a very 'tough' fiber and basically if you 
> try
> to sand it all you do is make it fuzzy. It does not sand like glass at 
> all.
> So be aware of that and don't sand through the resin if you can avoid it.
>
> Also, you can probably make your flotation tanks out of glass. It's 
> cheaper,
> easier to work with, and for this application stiffness is probably not an
> issue. You just want watertight integrity. You probably will not save very
> much weight using Kevlar over using glass.
>
> Good Luck,
>
> J Bergquist
>
> On 11/1/06, Roger L. Kingsland <r.kingsland at ksba.com> wrote:
>>
>> This is a non-Alberg 30 question but I figure someone in this a gust 
>> group
>> must know the answer.  I recently bought a 16 foot "polling boat" made of
>> Kevlar.  I would like to expand the built-in flotation compartments at 
>> each
>> end and don't know if standard fiberglass tape and epoxy will stick to
>> Kevlar or if I need some other stuff.  Any thoughts?
>>
>> Thanks, Roger
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