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Hydrofoil board layup

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Rufusz
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Hydrofoil board layup

Postby Rufusz » Sun Oct 30, 2016 8:25 pm

I managed to break my HF board due to XPS delamination and planning to make a new one with EPS core as it bonds better with epoxy.

I want the rails to be bulletproof as I tend to hit it with my harness hook before waterstarts. Should I use UD carbon fibre or kevlar tape?

The layup would be 2x160g glass (or 200g) top and bottom and a few layers of UD carbon tape under the foil for additional support (4 bolt foil mount).

Is it Ok to mix glass and carbon under the foil for more stiffness or should I stick with glass reinforcements only? The carbon is way less flexible then the glass so at extreme load the carbon could break before the glass?

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Re: Hydrofoil board layup

Postby plummet » Sun Oct 30, 2016 9:05 pm

If you want impact resistance on the rails go kevlar. Its way better for impact and abrassion than carbon. But its a shit to work with.

Feel free to mix carbon with glass. There's no problems there. Carbon will not break before the glass. It will stiffen the whole structure and make it stronger than a glass only construction. Take note on the stress risers you can potentially create transitioning from the carbon reinforced area back to glass. The load may be transfered to that point and make the glass/carbon transition the new failure point.

My call, rather than having square cut carbon reinforcements. Taper and round out the carbon section both in layers and shape. That will disperse the stress and you wont have a focal point for failure.

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Re: Hydrofoil board layup

Postby Rufusz » Sun Oct 30, 2016 11:15 pm

Why is kevlar hard to work with? I know cutting it is a pain in the @ss but is it also more rigid or what? Never used it before.

Thx for the carbon patch tip will keep that in mind. Will 2 extra layers of 120g CF patches be enough around the foil mount?

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Re: Hydrofoil board layup

Postby plummet » Mon Oct 31, 2016 12:53 am

Kelvar is a prick to sand and cut after layed up. it goes all furry and horrible. Its heaps easier if you use it for internal layers that you wont be sanding later on.

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Re: Hydrofoil board layup

Postby downunder » Mon Oct 31, 2016 4:48 am

Rufusz wrote: .
.

I want the rails to be bulletproof as I tend to hit it with my harness hook before waterstarts. Should I use UD carbon fibre or kevlar tape?
.
.
Nope. If you want it rock solid, use a PU. Polyurethane rails >=1cm thick, wide as you need it all around the board. You'll need to mold a PU, I would strongly suggest making it pre-made before a board layup.

The "bulletproof" kevlar comes with a price, we talking 15 layers at least :) One layer of kevlar tape is nothing. It will break on a first hit, letting the moisture in.
We talking epoxy elongation break here, not the CF/FG. The PU elongation break is way more higher than epoxy. Ask yourself why the snowboard rails are all PU?

D.

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Re: Hydrofoil board layup

Postby plummet » Mon Oct 31, 2016 6:34 am

downunder wrote:
Rufusz wrote: .
.

I want the rails to be bulletproof as I tend to hit it with my harness hook before waterstarts. Should I use UD carbon fibre or kevlar tape?
.
.
Nope. If you want it rock solid, use a PU. Polyurethane rails >=1cm thick, wide as you need it all around the board. You'll need to mold a PU, I would strongly suggest making it pre-made before a board layup.

The "bulletproof" kevlar comes with a price, we talking 15 layers at least :) One layer of kevlar tape is nothing. It will break on a first hit, letting the moisture in.
We talking epoxy elongation break here, not the CF/FG. The PU elongation break is way more higher than epoxy. Ask yourself why the snowboard rails are all PU?

D.
I could be wrong but isn't this board an Sb type construction?
If so 1cm pu rails would be incredibly heavy.

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Re: Hydrofoil board layup

Postby faklord » Mon Oct 31, 2016 8:52 am

You may want to re-consider your core material. A closed cell pvc foam should virtually eliminate water uptake even if you do ding the skin. Useful for both rails and also the bolt through for the foil mount.
To toughen up the rails you can just add a few layers of fiberglass tape. Either just plain tape or there a plenty of hybrid tapes sold specifically for this purpose ( Google fiberglass rail tape).

Also there are various options for removing your damaging hook (eg sliding setup). Further protection can be added to the ends of you spreader bar (eg neoprene sleeves ...possibly cut off arms/legs from an old kiddies wetsuit?)

Why UD patch for foil attachment? I would go with something with fibers running in both directions.

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downunder
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Re: Hydrofoil board layup

Postby downunder » Mon Oct 31, 2016 8:54 am

plummet wrote:
downunder wrote:
Rufusz wrote: .
.

I want the rails to be bulletproof as I tend to hit it with my harness hook before waterstarts. Should I use UD carbon fibre or kevlar tape?
.
.
Nope. If you want it rock solid, use a PU. Polyurethane rails >=1cm thick, wide as you need it all around the board. You'll need to mold a PU, I would strongly suggest making it pre-made before a board layup.

The "bulletproof" kevlar comes with a price, we talking 15 layers at least :) One layer of kevlar tape is nothing. It will break on a first hit, letting the moisture in.
We talking epoxy elongation break here, not the CF/FG. The PU elongation break is way more higher than epoxy. Ask yourself why the snowboard rails are all PU?

D.
I could be wrong but isn't this board an Sb type construction?
If so 1cm pu rails would be incredibly heavy.

The PU will not add much since EPS core. The rails 6mm by 6mm are incredibly light, hence the 10mm by ie 30-40mm would be little in added weight. No clue how would one or two CF/KV layers protect the core of hook impact...Wood rails?

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Re: Hydrofoil board layup

Postby zob » Mon Oct 31, 2016 10:38 am

Full wood core board?

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Rufusz
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Re: Hydrofoil board layup

Postby Rufusz » Wed Dec 28, 2016 12:15 pm

I was busy lately so still haven't build the board now I have time but all the suppliers are closed until January.... so I am starting to overcomplicate the board build :)

I had some scrap material laying around and made some samples... now I prefer EPS over XPS as its really hard to achieve a good bond between the XPS and epoxy.

I am also thinking of a cork veneer sandwich construction but not sure about the flex properties or if it worth the extra effort and weight. Roughly a 2mm cork veneer will add 340g plus the resin it takes in. Thats a full top and bottom veneer I guess I can get away with the top only covering the rails as well.
Anyone tried this method? I've used cork roll as a deckpad and it seemed pretty durable and know that some guys use it as veneer for SBs.

I will be using vacuum.

Layup from top:
160g glass
2mm cork
160g (or 220g) glass
EPS core
160g (or 220g) glass
160g glass

For the foil mount there will be 4x 20mm CF tubes to prevent the foam from crushing.

Still not sure if a few CF stripes and patches (foil mount, rails, 'stringer') will make any difference or should I use glass?
Some hands on experience sharing would be much appreciated :)


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