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Foilboard building tips

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rhorton1
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Foilboard building tips

Postby rhorton1 » Tue Mar 17, 2015 6:53 am

Hi all,

I've been making good progress on my homebuilt foil, and now I'm getting down to planning my foilboard build. I have a 5'8 2lb EPS blank, which is stringerless. I am planning on a finished board of about 5'4" length and 23" width.

Can anyone suggest an ideal thickness? I haven't been able to find much info on this. My blank is 4" thick.... but I was thinking of a final thickness of about 3".

Also, does anyone have suggestions on the glassing schedule? I want to do a layer of carbon on both the top and bottom. I was thinking 6oz glass with one later of carbon for the bottom, with an additional 2 layers of glass reinforcement around the hydrofoil mast attachment. For the top I am thinking the same, with an additional 2 layers of 6oz glass under the standing area. As of right now, I'd like to avoid doing any wood veneer under the standing area... unless I hear here on kiteforum that its absolutely necessary.

Lastly, I have some questions about inserts.... I will be using 2 10" windsurfing mast boxes wrapped in Divinycell for mounting the hydrofoil, and I plan on installing this into the blank before glassing the board. I figure that with vacuum bagging, I will be able to see and cut out the slots for the foil after the epoxy has cured with my Dremel. Now, for the foot strap inserts... should I also install these before glassing the board? I'm worried that I won't be able to find the holes for the screws under the carbon fiber. Any suggestions to help me along with the build would be greatly appreciated!!!!!

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Re: Foilboard building tips

Postby ozchrisb » Tue Mar 17, 2015 4:47 pm

Don't use a stringer, they don't do anything useful. Use carbon everywhere you though needed reinforcing, especially around the mast tracks. Carbon is so much stronger than glass, and the extra cost is marginal if you're wrapping the whole board in carbon. You'll have a lot of off cuts that will be useful reinforcements. If you run your finder down the mast tracks before you bag it you'll easily see them, a trim router with a straight bit that has a bearing on the bottom is the best for cutting the carbon out. Dremel's don't have an equivalent tool but you could use a hacksaw blade to cut out the bulk and then sand the edge with a block. Just try not to squeeze resin in there. You could do the inserts afterwards but what a pain, and you're better off having that nice skin or carbon without the cuts. Either make a template so you can find the holes again, or wiggle a tooth pick or something into them before you bag the board so you can see at least one of them.
The best site I've ever seen for this stuff is here (someone posted the link in an earlier thread, thanks!):
http://www.boardlady.com/extrainserts1.htm
Especially
http://www.boardlady.com/stringers.htm
"Picture the fiberglass skin (the steel cable): it is immensely strong (approx 25,000psi) and will not stretch appreciably (elongation approx 1%).
Let our stringer (the rubber band) be made of Cedar, with a tensile strength of around 450psi (and that’s being charitable), and an elongation of approx 5%, i.e. about 5 times stretchy-er than fiberglass.
As a load is applied, the fiberglass skin will remain virtually unchanged, until finally, as its yield strength is approached, it will stretch a minute bit, and then snap. The Cedar stringer will initially not see any load whatever, because it is happily bending along, not even close to its elastic limit. By the time the fiberglass gives out at its 25,000psi tensile strength, and all the load is transferred to the Cedar stringer, it – with its puny tensile strength of 450psi – is hopelessly outclassed and will fall over dead immediately."
Say no to stringers! Sorry, I know you said your blank didn't have one, but it's a thing of mine to campaign against them.

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darippah
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Re: Foilboard building tips

Postby darippah » Tue Mar 17, 2015 5:12 pm

I didnt read your post but i think these days it makes more sense to buy a great used foil instead of building one that may or may not be good

Arcsrule
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Re: Foilboard building tips

Postby Arcsrule » Tue Mar 17, 2015 6:17 pm

darippah wrote:I didnt read your post but i think these days it makes more sense to buy a great used foil instead of building one that may or may not be good

good idea! except, great used foils do not exist for the most part...it's usually a five minute window from FOR SALE to SOLD :)

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Re: Foilboard building tips

Postby rhorton1 » Wed Mar 18, 2015 3:37 am

Thanks for the good tips. Can anyone comment on my proposed glassing schedule? I will plan on using 2 extra layers of carbon around the mast attachment area for extra stiffness.

And a used board would be great... but I've already bought the materials! I'm past the point of no return now!

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Re: Foilboard building tips

Postby Arcsrule » Wed Mar 18, 2015 10:20 am

i used two layers of uni carbon on each side of the mast and one layer of bi--no twist, no flex. i used sandbags and clamps and plates for pressure until i built my vacuum pump.

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Re: Foilboard building tips

Postby Tone » Wed Mar 18, 2015 2:14 pm

I built a foil which I haven't used yet.

It was great fun to learn how to use carbon, resin, core products etc. I have already started to fix peoples boards when they have damaged them. I say go for it through bear in mind it is a lot expensive than you think it would be.

I spend £2000 on tools and materials and in the end spend another £1400 on a Zeeko foil to learn how to ride so that I can see if my own board/foil combo actually works.

good luck

Tony

Arcsrule
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Re: Foilboard building tips

Postby Arcsrule » Wed Mar 18, 2015 6:35 pm

i'm under $450 so far, including the pump.

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davesails7
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Re: Foilboard building tips

Postby davesails7 » Thu Mar 19, 2015 2:40 am

Arcsrule wrote:
darippah wrote:I didnt read your post but i think these days it makes more sense to buy a great used foil instead of building one that may or may not be good

good idea! except, great used foils do not exist for the most part...it's usually a five minute window from FOR SALE to SOLD :)
With the US Dollar being so strong, you might want to check out used foils for sale in Australia. I did a quick check of seabreeze and they have several complete KFA Mk 1 foils with boards for sale at $1600 AUD which would come out to about $1240 USD before you negotiate. Not sure how much shipping would be, but I've heard if you do air freight and pick it up at your local airport it's not too bad. I just got a great deal on a chrono from Australia and shipping was only about $120, got it in under a week.

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Re: Foilboard building tips

Postby Arcsrule » Thu Mar 19, 2015 7:27 pm

i learned my lesson buying from outside US, sight unseen.


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