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Small tough directional build

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foam-n-fibre
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Small tough directional build

Postby foam-n-fibre » Fri Aug 15, 2014 9:54 pm

Hey guys, i'm looking at building a small directional which will have a strapped option. Maybe 5'8" or so by 18.5" I built an EPS epoxy and bamboo veneer board last year for riding strapless, but want something smaller and with a strapped option for higher wind and more bumpy days. It'll only ever get used in onshore great lakes conditions and maybe Hatteras oceanside, so not peeling perfect waves like we see in some places, but it's not for mowing the lawn at home in the flats either. Mostly onshore type beach breaks.

The ESP I have is about 1.7 lb/ft, and the blank will have no stringer, or at least that is the current plan. I have built full sandwich windsurfers before with corecell top and bottom, but don't plan to go that far. I'll have corecell in the heaviest loaded parts of the deck for sure, but am not sure if I should have it cover almost the whole deck. Also on the bottom, I'm wondering if I should add some HD foam. I'm considering a strip of HD foam laid into the bottom, maybe a few inches wide, to help with buckling stiffness rather than the whole bottom, and then doing the thin bamboo veneer over the whole bottom for extra strength and bling. I would probably do at minimum a similar strip on the top under the top bamboo.

Has anyone done a board like I'm describing? Any suggestions on the layup? It'll be probably 2 inches thick at max. I might do carbon rails since I have some carbon, but won't do a full layer, and don't expect doing just the rails adds a whole lot of extra strength or stiffness. I'd probably have 2 layers of 6 oz with all the other stuff I'm describing, but do have 4oz kicking around also which could be added or swapped in. There would be a bit more around the straps I expect.

Ideas?? What is the usual failure more on a board like this? Originating from a heel dent? Tension or compression on top or bottom?

edit: I'm about 160 lbs, FWIW

Thx,
Peter

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Re: Small tough directional build

Postby robertovillate » Fri Aug 15, 2014 11:27 pm

Sounds like a cool project and sounds like you have the right experience to make something really nice.

I am also 160# and one of my favorite boards is my strapless 5/8 Lost RNF, which is an Aviso construction (hollow carbon fiber). I have been riding this board hard (and travelling with it on planes, trains, and automobiles) for the last 7 years and NO heel dents, no dings.

This shape is great for the Great Lakes waves ( I live/ride in West MI quite a bit) but I have also ridden this board in head high to double overhead ocean waves, such as in Ireland.

I would say the RNF is definitely better suited for head high or less where you don't need the speed, but the board carves and snaps beautifully, and is a lot of fun even on little ankle slappers..

By comparison, my 5/10 Firewire Taj is not nearly as tough and has it's fair share of dings. This board has more rocker an so needs a lot more power and likes a steeper faster wave. Also the deck on the Firewire is rather narrow as it is a low volume (24 l) board so footwork must be solid, whereas the Lost RNF has a bit more volume and a wider deck making footwork really easy.

I put some good fins on both these boards which makes a difference too (FPS K2.1 Sonny Garcia's ...?

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Re: Small tough directional build

Postby BWD » Sat Aug 16, 2014 12:58 am

Failure:
Fast from snapping under front foot, always starts with deck buckling.
Slow failure possible at tail from stress concentrated at fins and foot strap inserts.
Not as likely tho.

Have loved my Paipo style wood strip board 5'7"x18.25" ridden for a year tough as a TT.
Also built a super skinny 6'3"x14" board for speed in chop/waves.
Neither has appreciable volume but the paipo works fine at low speed because of width/square tail. The needle needs full power to go upwind, holds awesomely in fast turns, sinks if you slow down.
If you stick with that light foam core maybe it's worth a stringer after all or full corecell deck...?

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Re: Small tough directional build

Postby foam-n-fibre » Sat Aug 16, 2014 12:55 pm

Thanks for the info guys. It'm not too worried about the slow failure over time because sadly I don't get to the right conditions often enough.

Does anyone know, on other boards with sandwich construction are they using stringers or higher density EPS? I know that when not sandwiched foam with over 2 lb density is used, but I thought they were usually lighter when sandwiched.

Peter

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Re: Small tough directional build

Postby tkettlepoint » Sat Aug 16, 2014 2:18 pm

my fav board for the high wind stuff is my super man board I call it. ( just because of the colours I painted it) and jim calls it the scrape board. ( all left over pieces from the shop)

It is eps core. corecell top and bottom. with a wood inlay in it. carbon full bottom with 4 oz over it. and 2 layers of 4 on top. it is alittle heavier but I am ok with that for the big winds.. it does come off and hit me in the shins off the waves. small and fast but needs to have power to ride it . I ride it strapless but it has had straps on it for someone else.

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Re: Small tough directional build

Postby Bigdog » Sat Aug 16, 2014 3:25 pm

Hey Pete

A friend of mine from Sarnia built a directional using only corecell. I thinks it's 3/4 or maybe 1inch. Super tough and really flys in high wind. You could do something lie that and even add a little more rail thickness. I think flysurfer made something like that before. I don't see why volume is of much use anyway and eps eventually sucks ;)

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Re: Small tough directional build

Postby tkettlepoint » Sat Aug 16, 2014 7:31 pm

stan skywalker man on too called the D Wave .. it was 3/8" thick. They built them something like BRO boards does with I beam construction. I had one and loved it too . one of those boards that got away from me... I have only sold 3 personal boards in 15 years all the rest I have kept. and if I could get them back I would most likely do it.

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Re: Small tough directional build

Postby foam-n-fibre » Sat Aug 16, 2014 10:33 pm

Hey Stan the only issue I see with thickening the rails is that if it flexes there it a lot of load at the thickened rails, since they are so much further from the neutral axis, and with the neutral axis moved upward, it means there is less stress taken by the top skin, and more at the top of the thicker rail. I know some guys like the Underground Kipuna which is like that, but I've seen some pics of broken ones and of course the rails let go. That's not to say they all break or anything, I have no idea.

Maybe one option is to build a fairly thick board with only corecell, and if you want a round surfy rail and also a bit of flex, add more on top with EVA foam, which does nothing structural. BUT, I have enough materials including leftover foam from a race SUP build that I'm all set with everything I need if I use EPS, but I have no thick corecell.

Speaking of a SUP build, just to hijack my own thread, I built a couple SUP carbon paddles too, including making the shaft. Very cool. You can read about some of that on the standupzone.com forum.

Peter

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Re: Small tough directional build

Postby foam-n-fibre » Sat Aug 16, 2014 10:35 pm

BTW Terrie, what is the length and width on that board? Looks Nice!

Peter

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Re: Small tough directional build

Postby Johnny Rotten » Sun Aug 17, 2014 3:28 am

Random comments some may or may not be useful....

I like to make my boards LIGHT....
A board with low inertia is the tits. Require less wind to stay on your feet, less effort to turn and physics says it'll stick to your feet better than others over the bumps and such....I guess your making one with straps though......still low inertia is the best.

I dislike carbon unless very carefully located as it has poor impact properties and adds stiffness which most builds that are tough enough to take a landing don't need at all. the rails isn't a horrible place for it and won't add a lot of additional stiffness still it doesn't really gain anything much beyond the sexy bling and you lose toughness. It might give you some good "spring back" but it's unlikely the board will have enough flex or a natural frequency where the spring back will be useful and still be able to take a good landing.

I've found if you get the rail too thin the board starts to bury it's edges a little too deeply on heavy carves. Sinking the entire front of your board on a deep carve ends your flow on the wave but increases your flow in the air pretty fast :-?

the more layers of anything often times the more wasted epoxy you have just gluing shit together. Foams and most other things tend to suck up a rather offensive amount of resin or resin and micro when you glue em together.

right now I'm using 1lb EPS in my builds with a heavily glassed corecell sandwhich and can slam out a 5-6 lb finished board.
I'm still determined to do better especially on the flex front.
I'm not hitting the flex I want without getting excessively low on rail volume.

I'll know a lot more in the upcoming months as I've build some shit to do some more rigorous testing.

As to stringers they were originally added to PU/PE boards with a 2 x 4oz top and 4 oz bottom on 3lb foam to get some additional stiffness spring back and strength to a tissue paper lamination On most boards that can take a landing you want to decrease stiffness....I don't see much purpose to the stringer on most kiteable constructions.

EVA foam (foot pads) haves a massive impact on toughness as they can absorb and disperse energy better than a composite fiber that is loaded off axis. (jumped on)

Also important the % elongation of your resin exceeds that of your fiber in order to make the most out of the structure in off axis impacts


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