Hi Builders, I need some tips.
I'm looking to build a kiteboard, which I know is a bit off topic, but the diy kiteboarders aren't up to using laminate like skaters do. (its more like two sheets of marine ply stuck together!)
Because the board is larger (140*41cm) I need to go to full sheets of laminate, which I can only get in 0.6mm (Briggs - they do skate packs of rock maple too). Construction will be several layers of laminate, foam core under the feet, glass top and bottom.
My question is: How many layers of veneer do I need? It will be fairly stiff in the middle due to the foam, but needs a fair bit of flex at the tips - like a dervish or apex, or more flex. I'm guessing 9 layers will do it.
My other big concern is trapped air - do you do anything to remove it or does vac-bagging sort that.
Hey Ben - yep, vacuum bagging will eliminate the air... I guess you are going to shape the foam in the middle and taper it down so that at some point towards the ends (and edges) it's just laminate with no foam between the layers. For foam, I'm also guessing it will be expanded (not extruded) polystyrene? If that's the case, then there will be some compression of the foam.
You could try something like 1.5mm hoop pine ply - it's used regularly in AUS for home made longboards due to the scarcity of good veneer, particularly in the dimensions you're looking for. the 1.5mm 3-ply comes in 2400x1200 sheets but seems to have gotten a little pricey of late - somewhere in the vicinity of $90 per sheet from what I've found.
Sounds like an interesting project - happy to offer any verbal assistance if you need it.
Yes, the foam need to be feathered down at the edges. I was planning on divinicell but I can't get small quantities so i'm thinking paulowina instead.
I'm not so keen on using ply as there's some sharp contours - a channel on the bottom of the board, and its not any cheaper at that price. $18m2 for the rock maple - its just a lot of layers to get the required thickness.
Are you just using a standard vacuum cleaner?
not a problem - the standard vacuum cleaner only pulls so much in the way of pressure and the rest is done with the hand pump that comes with the Roarockit kit (I have a 70" x 20" Roarockit bag). I know FGI (also known as Nuplex) do Divinycell but I've never enquired about sheet size as I haven't built any fully composite decks - I can find out if they do a smaller sheet if you're interested (I'm in Melbourne but they have a Sydney store as well) http://www.nuplexcomposites.com/australia/?q=node/38
How sharp a contour are you looking for? I've managed to bend the 1.5mm ply pretty severely with a 2" drop deck before
OK - I see - a vacuum bag will struggle to get that sort of short, sharp bend - I'd reckon only something like a hydraulic press could do that... Veneer maybe, particularly at 0.6mm but then it may snap - I've heard of sprays that help to soften the veneer and don't affect the glue/epoxy layup and adhesion but complexity is mounting!
What does the "tunnel" that having this sort of contour do for the board? Is it a handling/performance feature?
The channel is there to help keep an edge -stops the board hopping out of the water without oversize fins. I fugure they must use a vac bag because of the complexity of the layers. It would take far too long to perfect a press to get the contours between the cored sections and tip shapes. Maybe its time to simplify.
yeah... BTW, I had never heard of paulownia timber before - looks like cool stuff. Maybe you could shape it such that you are then veneering the 0.6mm over it? Bagging is incredibly powerful, I've just never tried a bend quite that short and steep. The channel doesn't run the length of the board by the look of it - so many possibilities and it would be a great project (if I knew how to kite board!) Sorry I don't think I've been of much assistance...