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Bomb proof board from XPs insulation foam

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juandesooka
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Re: Bomb proof board from XPs insulation foam

Postby juandesooka » Fri Jan 27, 2017 6:31 pm

Love the DIY attitude in this thread! I am pursuing a basement renovation, been gluing xps insulation onto concrete walls, and carving out chunks for the oddball sections. Looking at that scrap pile and reading these posts got me thinking ... maybe should try making a board for my foil! I have surfed for a long time and always considered making a surfboard too much ... moderately easy to make a crap board, probably beyond me to make a good one. But foiling is a little different, the board is mostly a platform to support mast, design-wise it needs to be water tight, float for water start, and able to handle touchdowns. A lot less hydrodynamics involved than a surfboard. Hmm.

Currently I am using an old surfboard. I just drilled holes and epoxied in some carbon inserts for the mast bolts, then use plastic plates on top and bottom to bind it together. Seems to be working ok, but the board is a little too long and little too narrow, tends to sink the nose on touch downs. Also, there's a pre existing flex in the mid section that will eventually be the end of it. So....a better board may be in order.

Anyways, a few questions about inserts -- the rectangle cut out for the mast is to replace with wood (or higher density foam), to give the mast something solid to bolt to. Is the fibreglass layers over top and bottom of this enough to hold it in place? Any risk of the wood pulling out of the hole, stripping off the fibreglass? Or does the sandwich of fibreglass/wood keep it in place?

I assume this is how it is done....just never really occurred to me there's wood inserts in these boards. I guess an alternative design is like the surfboard I am using ... the epoxy tubes keep the deck from compressing, the wood stringers keep it from pulling out of the board.

Do the inserts need any water proofing inside the wood holes, to avoid water getting into the wood or sneaking between fibreglass and wood into the foam? Or minimal enough to not worry about?

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Re: Bomb proof board from XPs insulation foam

Postby BWD » Fri Jan 27, 2017 7:49 pm

any insert block(s) to hold the foil attachment (or whatever else you want to strongly attach to a composite structure with a lightweight core) are held in mainly by the laminations of glass, carbon or whatever on top and bottom.
It needs to be more than the glass needed for a "normal" area of skin, and the area of extra lamination needs to extend beyond the attachment area, I would say a good 75-150mm side to side and behind, and probably 300+mm in front. Extending extra lamination out farther/thicker in front also stiffens the board, like you will see done on many modern stringerless surfboards that have strips of carbon or similar down the middle to control stiffness.
This will work about the same whether you are dealing with one huge insert to hold multiple bolts (or a cavity base), two parallel fin boxes to be adjustable, or separate inserted tubes or small blocks to pass bolts through.
If wood, it always needs to be sealed.
Best practice is usually considered to drill an oversize hole, fill it with mix of epoxy and a heavy duty filler (e.g. milled glass fibers & red phenolic microballoons -NOT white "glass bubble" ones for fairing), then redrill to the proper size so you end up with a hole through a strong donut of reinforced resin. Or just glue in the right size glass or g10 tubes, little g10 blocks etc., then drill.
Another good option could be to "roll yer own" fiberglass pipe and slice off what you need: having even 1.5-2mm of glass surrounded by an epoxy/filler column would be better to avoid cracks I think.
Easier if you can find the right diameter premade g10 or fg pipe though.

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Re: Bomb proof board from XPs insulation foam

Postby omg » Tue Jan 31, 2017 9:57 pm

Very good info on this thread. Especially TomW's and BWD's, thanks very much!

I am on the fence whether or not to start building foilboard. I have XPS 3cm blanks, but they are really soft stuff compared to real EPS etc. foams. Nevertheless, two quick questions I have been thinking abt:
1) my idea is to epoxy the two blanks so that I will get 6cm thickness. Would it be good idea to put a layer of glass in between the blanks? To my mind it will stiffen the board, which is needed, right? But, as I would like to make the board as light as possible, would 2 layers of glass and 1 carbon (all around 160g/m2) layer on both side be enough? Then perhaps a wide (40x70cm) strips of glass overlapping the area where the foil will be attached. I'd rather skip the wood layer if possible due to extra weight?
2) The board would be 6cm thick, do you think I'd need stringers or thicker foam to where the foil is attached or should I build a stringer setup for the holes? Or would four carbon rods installed in to the board be enough (and screws would go through them to the foil)?

Thanks!

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Re: Bomb proof board from XPs insulation foam

Postby TomW » Tue Jan 31, 2017 11:11 pm

Omg,
First, forget about making a lightweight board from soft xps. It's not the right starting point.
Putting glass between the foam is useless. You get stiffness from skins.
6cm is way too thick. A board 20-40 mm is better. Shape it down. I'd just use one 30mm.
The soft xps needs a higher density sandwich on deck. That can be wood or other HD foam you can buy. Glass under, then 3x glass over. 3x glass bottom.
Carbon is waste if money if you are building boards for first time.
In think you need stringers for and around foil attachment. or substantial blocks and fiber reinforcement as bwd says.

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downunder
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Re: Bomb proof board from XPs insulation foam

Postby downunder » Wed Feb 01, 2017 2:36 am

Tom

the standard in HF racing is way more than 3cm. I would say it's somewhere between 8 and 10cm . My fellow DIY builder is making carbon and foam boards for the racers (we have a lot), and using 2 or more stringers, full length. No CF rods, fully wrapped board in CF. Light as feather. He does not bother with a foils.

Here is a pic of winning Nico Parlier board: http://www.seabreeze.com.au/img/photos/ ... 427627.jpg
Interestingly, all racing boards are almost the same shape, or similar.

This is his jump after finish: http://www.seabreeze.com.au/img/photos/ ... 427625.jpg
showing angle of the mast.

Mike's design:
http://www.seabreeze.com.au/img/photos/ ... 427629.jpg

Omg

there is almost no weight adding 4mm thick Paulownia, full deck. It is that light. What it does it protects from dings from your harness hook, etc. Priceless.

No need to build a complete foil tho. I've paid $100 for production alu mast, which I will only use for mold. Build a wings first, this is very, very easy build which I can do in a few hours (since I have a mold)/ Look for my "Front wing" build.

Just my 2c (does 2c exist any more? Duno :)

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Re: Bomb proof board from XPs insulation foam

Postby DartBoard » Wed Feb 01, 2017 8:57 am

TomW wrote:Omg,
First, forget about making a lightweight board from soft xps. It's not the right starting point.
Putting glass between the foam is useless. You get stiffness from skins.
6cm is way too thick. A board 20-40 mm is better. Shape it down. I'd just use one 30mm.
The soft xps needs a higher density sandwich on deck. That can be wood or other HD foam you can buy. Glass under, then 3x glass over. 3x glass bottom.
Carbon is waste if money if you are building boards for first time.
In think you need stringers for and around foil attachment. or substantial blocks and fiber reinforcement as bwd says.

TomW, Are you referring to low compressive strength XPS when you say 'soft xps'?

I've read on some boat building forums about sandwich constructions using 400kpa compressive strength XPS foam (Bunning's Knauf Multi-purpose board is 300kpa) and one source I came across claimed they'd run the numbers and for 400kpa 25mm thick panel then with glass laminate thickness greater than 0.72 mm (c. 3 layers of 6 oz) the core will fail before the laminate because the shear strength of the XPS is poor (compared to PVC foams). Thicker panel makes the problem worse because the tension at the surface of the panel increases under flex as panel thickness increases.

On a practical note I've used 30mm xps foam for my 120 x 42cm board and there is more than enough volume to have it always floating (previous modified twin tip took a long time to resurface after a nose dive) so there might not be much to gain from a thicker board if your going with XPS.

I've got a new board planned and will probably use stringers again to support foil connection and footstrap inserts. Although I've never built one without stringers I just know from my previous board that hitting a sandbank at reason speed was enough to crack a 12mm paulownia, glassed twin-tip style board
at the mounts. If your only going to kite in deep water then maybe you don't need to built for the worst case but where I live the shifting ocean floor means that I still discover new submerged obstacles all the time so I build above and beyond rather than again and again.

Woodie Cookie in the Netherlands, an ex-raceboard champ, board designer and now foil designer, has made some hollow raceboards. Can anyone think of a good reason why hollow boards wouldn't work for foils?

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Re: Bomb proof board from XPs insulation foam

Postby RalfsB » Wed Feb 01, 2017 11:57 am

DartBoard wrote:Woodie Cookie in the Netherlands, an ex-raceboard champ, board designer and now foil designer, has made some hollow raceboards. Can anyone think of a good reason why hollow boards wouldn't work for foils?
Hollow boards do work for foils, I know that a local company Stradi Custom Boards built a batch of them.

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Re: Bomb proof board from XPs insulation foam

Postby TomW » Wed Feb 01, 2017 8:29 pm

Hej Dartboard,

Good information. I'm referring to the blue xps ground insulation I can get here in Sweden. It's super soft in compression, and has poor shear strength. ( bend it and it snaps).
I have no idea what the numbers are.

My modification to a surfboard ( own construction) may or may not hold up. I'll just have to try it.

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Re: Bomb proof board from XPs insulation foam

Postby borist » Thu Feb 02, 2017 1:42 am

Not so "bomb proof" creation. Made from 1 inch thick blue insulation foam, fiberglass and few patches of CF in critical areas. Basically what I had left over in my garage from previous built. 118 x 46 cm. Mounting holes reinforced with Garolite tubes. Chinook 2 hole footstrap inserts. no vacuum bag :(

Laying base layer of glass on the deck. Cuts to produce nose rocker visible.

Image

Final look. 1/8" thick G10 washers used on the top to spread some load from screws.
Total weight 2 kg (4.4 lbs) with pads and front straps. Now I need some wind to test it :angryfire:

Image

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Re: Bomb proof board from XPs insulation foam

Postby omg » Thu Feb 02, 2017 1:22 pm

borist, looks nice. How stiff is the board, I mean if you press down the nose of the board or more realistically the front foot strap, does it flex? How many layers of glass on top and bottom did you put? Any wood patches etc?


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