Graham,
Agreed. All builders would be well advised to watch the mix consistency
carefully so as to prevent differing moduli of elasticity and (possible)
future problems during any lamination process. However, the step currently
under discussion is non-structural and really only about fairing reasonably
small areas. Filler depth should be quite thin (1/8" or less) so, while
sanding a catalyst-rich filler mix may be a bit more time consuming, it
really shouldn't be too bad. If the areas requiring filler are large or
deep, other considerations may apply.
For all lamination processes it would be prudent to:
1.) Use a standard pump system to manage resin to catalyst ratio.
2.) Mix the two thoroughly before adding fillers.
3.) Measure any additives carefully.
4.) Thoroughly mix the additives into the resin matrix.
5.) Conduct all resin application operations within temperature and humidity
conditions specified by the resin manufacturer.
Assuming those steps are followed, the fairing layers should be nearly
identical in hardness. The only time I ever saw hardness become a factor
was when the mixing process did not adhere to the proper ratio between resin
and catalyst or if the additive was sloppily blended into resin matrix.
Regards,
Jack
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Graham
Singleton
Sent: Monday, November 20, 2006 10:41 AM
Subject: Re: Europa-List: To Those That Have Sanded Before Me... :)
<grahamsingleton@btinternet.com>
Jack
This does work but it is vital to be certain that the resin/microballoon
mix is identical otherwise you will get hard and soft stripes, I got
that tea shirt once! It would be good with Superfil.
Graham
Jack Hilditch wrote:
> Composite racing sailboat builders use a technique that produces a
> fair surface, without bumps or valleys, while minimizing weight or
> extra filler. They screed the filler/resin mix onto the surface using
> a small-toothed, serrated plastic trowel (the same kind used to apply
> ceramic tile cement to walls). After it cures they use a 'long board'
> to sand it down. The 'long board' is not a fixed size. It can be 2" x
> 24" , 4" x 48" or any other size, depending on the surface area to be
> sanded. Most of them are made up in the shop using a piece of planking
> with a couple of hand made handles screwed to it and the sand paper
> glued or clamped to that. The long board rasps off the high areas, but
> leaves the valleys clearly identified by the serrated 'stripes' of
> resin/filler. On the next pass you only need apply the mix to areas
> that remain 'striped'. It saves work because the actual surface area
> to be sanded is reduced to the high points or 'lands' left by the
> serrated trowel rather than a raised patch left by a smooth trowel. It
> also saves on expensive resin. You get an additional bonus using the
> technique in that the serrations also leave a greater surface area,
> and irregular surface, for the next coat to bind with or key to. Hope
> this helps. I spent plenty of time working on racing sailboats in the
> US and UK so I know the technique works with resins from both sides of
> 'the pond'. Hope this helps.
>
> Regards,
>
> Jack Hilditch
>
>*
>*
>
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9:20 PM
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