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Hull Construction?

The United Kingdom Local Chapter

Hull Construction?

Postby PotatoHead » Tue Apr 03, 2007 10:21 am

Hello All

This is the first time I have posted a question and built a sub. So please forgive me for the peculiar questions.

I have noticed that the guys in the USA use the right materials for the job and easily pick them up from any builders merchant. But I have noticed that it isn’t as straight forward as that over here.

Regardless of using unsuitable materials I have soldered on. I am now at the point where I can consider putting resin on my frame or plug.

I have previously used resin with the fibreglass mess, but noticed that it tends to clump together whichever way I brush.

Is there another technique I can use? And where can get the materials from?
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Postby Himszy » Tue Apr 03, 2007 10:48 am

First of all, if your looking for the blue/pink foam the yanks use, you can buy it from Sheffield Insulation. Styrofoam 250 is the version you want IIRC. Failing that polyurethane foam works just as well and can resist polyester resin (Styrofoam can't) and is much easier to get hold of.

RE, the fibreglass - You should never brush on fibreglass resin - you need to use a stippling action, that way as you said the fibres don't bunch up.

You can order materials online from I tend to get mine from Polyfibre but that's only 'cos I'm on their doorstep.

Andy, was this the book you got and highly recommended?: ... 76-2273517

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Postby PotatoHead » Tue Apr 03, 2007 12:26 pm

Ok Thanks,

Before I run away and slap resin all over the sub, are there any considerations I should make at this stage before I find myself in a predicament later on down the line?

e.g. where I slip the hull or the finer details.

What troubles have you guys had in the past that might help me?
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Postby Sub culture » Tue Apr 03, 2007 12:27 pm

That's the book. Excellent tome giving you all the information you require to make your first GRP model.

BTW, practice on something small first, that way you won't mess a lot of hard work up.

I lay-up using the following methods.

PVA and wax the mould. If you're using the lost foam method, ignore this part and the next

Brush in a thin(ish) coat of Gelcoat, wait until this has set and is tacky- an hour or so in good temperatures.

Prepare my chopped strand matt (CSM) by cutting out appropriate shapes.

I use 400 gram CSM, and I use two layers for small lay-ups, with a few extra bits of extra in areas of stress, or where the boat is likely to take a whack at some point.

Mix and brush in a coat of lay-up resin, then lay my CSM over the resin, and stipple the matt in place with a stumpy brush, add a little more resin here and there to ensure the matt is fully wetted out.

Then finally I consolidate the CSM with the resin by using a washer roller. The last part is often overlooked, but is important IMO.

Using the lost foam method, I would put a layer of fibreglass tissue over the CSM, before consolidating with the roller. Then when this has all cured, I would key up the resin and brush on a thick coat of Topcoat. Topcoat is Gelcoat with a wax inhibitor added.

'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in-
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Postby Davy » Wed Apr 04, 2007 7:40 am

Just doing this at the moment (good fibreglassing weather!) so I thought I would chip in.

When handling CSM it is worth knowing that the fibres are bonded with some emulsion. So the CSM is quite stiff and hard to handle when dry but once it is wetted with resin the emulsion dissolves. The CSM is much easier to handle then and you can stipple it with your brush and work it into corners etc.

And at that point the phone rings! :)


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