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JimC View Drop Down
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Posts: 6660 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Topic: RS300 transom
    Posted: 21 Sep 07 at 2:21pm
Its more complicated... polyester on epoxy is a no no, because the styrene in the unreacted polyester attacks the epoxy surface and you don't get much of a bond. Epoxy on the other hand will grip polyester very well - probably better than more polyester does, but you do have to consider the difference in the other properties.

The moral of the story really is don't buy polyester boats... Cheap knockabout boats are best in thermoplastic, performance boats are best in epoxy.
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Isis View Drop Down
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Posts: 2753 		Post Options Post Options   Quote Isis Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 07 at 1:53pm
Idealy yes no5... though vinylester isnt too far from epoxy in terms of properties
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No. 5 View Drop Down
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Posts: 115 		Post Options Post Options   Quote No. 5 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 07 at 1:41pm

Thanks Paramedic.

I assume the same is also true for vinylester built boats?
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Rob.e View Drop Down
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Posts: 545 		Post Options Post Options   Quote Rob.e Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 07 at 1:20pm
The 300 is Epoxy. Don't think this is the boat that had the accident on the way to the nationals, this used to belong to one of the class stalwarts, and it's driving me mad trying to remember his name! It originally had pro-grip all over the inside. Think it was the guy who did the website....I had to do turns at the windward mark at the Lee nationals after touching this boat
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craiggo View Drop Down
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Posts: 1810 		Post Options Post Options   Quote craiggo Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 07 at 7:21am
I though 300s were epoxy not polyester.

Most of the temporary repairs that have taken place at Nationals by LDC have needed re-doing in epoxy following the event.

Polyester is I believe easier to work in a short period of time but as has been said can come away from the surrounding area in time due to the different expansion and elastic properties between it and epoxy.

Paul
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Paramedic View Drop Down
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Posts: 929 		Post Options Post Options   Quote Paramedic Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 07 at 7:38pm
Originally posted by No. 5

Originally posted by Paramedic

Don't use epoxy on a polyester built boat.

Why not?

Because the two resins have differant properties. If the repair is in an unstressed area you might get away with it, but if it's a loaded area and you use epoxy on a polyester boat the epoxy is harder and less flexible then the rest of the boat. This means that if the boat does flex ( as it always will under load) it comes to an abrupt halt at the repair and what usually happens is that the repair starts to come away from the surrounding material.

I thought 300s were polyester? It's been a while since i've seen one though!
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ratface View Drop Down
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Posts: 686 		Post Options Post Options   Quote ratface Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 07 at 6:54pm
nope i cant access the indside of the hull at the back... even if i was to put a hatch there it wouldn't really take one
BLYM
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JimC View Drop Down
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Posts: 6660 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 07 at 4:07pm
If I did it I wouldn't expect it to break again unless I hit something very solid. But it would take me quite some time - at least a couple of hundred quid at pro boat builders rates.

I should have said - do you have good access to the interior of the boat? I can't remember quite how the 300 is laid out. If I could get tools in to seriously sand down the inside of the transom (if you can't significantly abrade the current surface this isn't worth doing because the new laminate won't stick well enough) I'd put a patch of a couple of layers of carbon about 200 * 150mm over the whole of the fitting area and overlapping onto the bottom of the shell which, together with the outside repair, would end up stronger than new, if a few dozen grammes heavier.
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ratface View Drop Down
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Posts: 686 		Post Options Post Options   Quote ratface Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 07 at 3:39pm
i have had this happen before(but only up to the point in the 1st pic) and had it done by a local boat builder(who shall not be mentioned).

i would say since then its had 2 weeks? worth of sailing in it in a variety of wind strengths and has become what it is now...

will this always happen after everytime it gets repaired? or  would  JimC's method  make it strong enough to last
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No. 5 View Drop Down
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Posts: 115 		Post Options Post Options   Quote No. 5 Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 07 at 1:31pm
Originally posted by Paramedic

Don't use epoxy on a polyester built boat.

Why not?
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