I got some great help from XSWind on kiteforum re pre-cure topsheets. Here's the link
http://www.kiteforum.com/viewtopic.php?f=107&t=2374292
... and here's the guts of it.
The purpose is to obtain a thin skin which is resin as that is the only way to obtain a full and deep gloss/sheen.
The topsheet is wetted out on just a sheet of normal glazing glass and then vac bagged flat, there is a or two trick here but I will leave you to discover them to make it perfect.
yes I vac bag mine.
The objective is to make a cured and finished thin laminate.
Thickness is up to you but I normally do a 2oz or thinner scrim layer with decals next followed by a layer of 4oz. Leave to sure then bond
If done right you end up with a completely finished fully glossy outter surface to your board.
Once the topsheet is cured leave thay Maylar if you like sheet attached, dont remove it.
skuff the top sheets bonding side with 40 grit and clean the dust off. Now simply go to your rocker table lay up the normal structural layers and put the pre-cured top sheet on and after the normal vag bagging process has been done, you can remove that film layer to reveal the goodness.
Another tip is "a simple addition to the pile before bagging"
Ah, geez i tell you what.
ReplyDeleteGood stuff.
You know what ? It's been in front of our noses all along.
This video i posted at the very start of my blog about how i had figured out what vac bagging was shows this exact proceedure with carbon.
http://www.youtube.com/watch?v=p_4a-KLS1AM
All you would need to do is find a medium that would not stick to the resin once taken off as a backing, maybe a couple of pieces of 4mm coreflute sign board.
Hey Peter,
ReplyDeleteYes, I noticed that video on your blog and a couple of pennies dropped.
In the slightly mysterious response from XSWind on Kiteforum he mentions 2 things 'Think the otherway around' and 'a simple addition to the pile'. From your video, I think the first means put resin down first to avoid air air bubbles trapped on the underside of the cloth and the second I'm thinking might refer to placing peel ply over the top so you get the rougher surface on the back of the glass to aid bonding to the structural plies.
I'm thinking that I'd use builders plastic stretched over the perspex rocker table surface as the protective surface and leave it on during the layup of the board.
One variation I'm thinking about is to use cotton instead of fibreglass over the decals so that I can have an opaque background. The carbon straps I used on the most recent board are very unsightly and I want to cover them. It also seems that untreated nylon material will chemically react with epoxy (still a bit unsure about this one) and so maybe kite material (ripstop nylon) could be used. The pattern in the cloth is pretty cool.
Cheers