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Old Apr 10, 2015, 07:04 PM
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Well unfortunately I think the Scratcho wing moulds are ruined so I probably can't sell them. They've always fitted absolutely flush and flat, until I removed them from the post-cure of the last wing (post-cured to about 70 deg C for 12 hrs to see if it prevented the expanding epoxy from sinking back ... which I don't think it did).

Anyway when I opened the moulds they had warped into banana shapes. They were well and truly cooled, so I was pretty worried but I clamped them up again hoping they'd "settle". They've been sitting for 3 weeks, and I unclamped them this morning again to check and the bend is just as bad as before. It takes quite a lot of pressure to spring them back together.

Obviously a good reason not to use the ply backings on the Corian, I'd say (unless you never intend to post-cure).

Another point is that there's a repair on one of these moulds where I had an "oh sh#t" moment with the CNC cutting a trench into the mould when it had lost its Z position. I repaired it by filling it with gelcoat and sanding and polishing it back, which gives a great result. However after the post-cure the gelcoat has sunk back a bit, leaving a corresponding mark on the wing. Also worth noting that the stone texture of the Corian is visible in the paint on the wing, which didn't happen without post-curing. Anyway I have to say that many of my disappointments in the past have been related to using the Rengel SW10 gelcoat. Yes, it can be repaired and polishes up beautifully, but my experience is that it doesn't handle heat at all. The old Scratcho moulds and the Angry Bird moulds have had blemishes and dints appear in the mould after post-curing, where bits of hardware etc have created pressure spots ... or even quite marked cloth print which I've had to sand out.
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Last edited by AvB; Apr 10, 2015 at 07:12 PM.
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Old Apr 10, 2015, 08:38 PM
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Hey Andrew Ive had thos issues with ply backed moulds before too. I reckon you could save them by cutting slots (just with a wood saw or something) in the ply down to the corian layer at 90degrees to the bend. They wont be as stiff anymore but I would think they would straighten up again.
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Old Apr 10, 2015, 08:45 PM
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Nice tip Josh. Using a router doing some slots and I would suggest another slots longitudinal and then glue with epoxy some L Iron. And keep them clumped until cured.



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Last edited by chrispaiva; Apr 10, 2015 at 09:23 PM.
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Old Apr 10, 2015, 08:52 PM
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I think the problem is mixing wood and composites then heating it To a temp that it not suppose to. Different expand rates will react dif and bend?
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Last edited by decones; Apr 11, 2015 at 09:04 PM.
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Old Apr 11, 2015, 04:08 AM
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Yeah that is the problem, but it can be fixed. I doubt I or AvB would do it this way again, but I reckon this set of moulds can be rescued.
Cheers
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Old Apr 12, 2015, 04:23 AM
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Where is the inspiration
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Andrew.

Just leave them in the shed.
The wood will absorb some moisture again and go back.
Also its not a bad idea to lay up a very light skin (So as not to waist too much) maybe with some foam cores and close it up. Just to see if it has a twist. If no twist it will be ok because the shape will be 99% when the moulds are closed.

For the moment I am thinking of machined DIY corian moulds. So cut a plug undersized from MDF, seal, and fill with DIY Corian to your required depth. At this stabe you may want to machine the back flat first, and remove some excess material. Then turn around, remove plug then run a semi finish and a finish cut. The thing that may catch us out is the bubbles (Porosity) If they dont all surface and you run into some it could be disastrous.
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