KiteSURFboard- too much rocker - fin placement compensation?

[zimboflyman]

Hi all,

I've just finished a hollow wood shortboard from balsa and I think the final shape has just a little too much rocker and was wondering what I can do with the fin placement to compensate?

it's a 6ft shortboard designed for kitesurfing, so basically it's very simmilar in shape to a modern shortboard but maybe the rails near the back have a little more edge for release.I've copied another working board and was simply gonna copy the fin placement too, but my build has just a little too much tail rocker and probably a bit too much entry rocker too.

dimensions are 6ft x 17 1/2 x 2 1/4. i'm very nervous about the tail rocker especially.

should I move my fins a little forward from the copy board so they get too work before the tail rocker kicks in too much,

or...

do I go a bit back with my fins so there is not too much tail flip behind them...



It's my first build and in all the info about fin placememt - i can find very little to with my problem



any advice will be much apreciated...

Cheers

[haynman]

In my experience, I would probably leave the fin placement where it's at or move the fins just a touch forward.

Also, I'd probably make it a five fin placement for various conditions. And I'd use the new FCS fusion boxes for superior strength.

Your board looks really good considering a homebuilt.

??? Why such a narrow board?

[richswing]

Hey Zimbo,

Nice construction, I like the tail and nose detail. Did you make a skeleton and then skin it or did you use solid bits and hollow them out.

If you have a bit of meat on the bottom you could increase the single concave rocker entry (make it more concave) which will flatter out the rocker but still have good rocker on the rail.

Share your construction details, nice job.

Cheers
Rich

[zimboflyman]

howzit guy's,
thanks for the advice!

it's a frame build with skins.
here's some info...
http://www.grainsurf.com/forum/viewtopi ... 71&start=0

the board is already glassed, I put in as much concave as possible (not much), but the skins are pretty thin so next time I will build some concave into the frame. also means staying with the thruster set up as there are strengtheners for only 3 fins built in.

so I'm left only with the option of moving the fins slightly forward or backward and my feeling is to agree with haynman and try a little bit forward.

any other advice out there?

for my next build I think I will definitely look at 5 fin option!!

just re-measured and it's 18'' wide not 17.5 - is that still too narrow maybe?
I'm hoping that the increased buoyancy from the hollow wood build will compensate for any narrow width.
Im 65 kg so don't need anything too big
it's my first build so I've got a lot to learn about design and shape - hopefully if I can get to ride this soon, I will have some ideas on what is working and what needs changing...

[bokie]

Awsome job ZFM!
My suggestion...ride the board you copied if you can. I wouldn't start changing things especially
if You have not tried it out the way it was designed. I'm betting you'll be able to get it dialled in either way by changing your fins out if it's not quite right.
How many hours do you think You've got into this build?

[zimboflyman]

Cheers bokie...

the reason I'm looking for fin placement advice is, my board ended up with a bit more rocker than the board I copied so I'm not sure the same placement will be right?
mine board looks a bit more potato chip like!!!
Kevin Slater recomended less toe in to compensate for the increased drag of the extra rocker (as far I understand?) so I'm gonna use 4 way fin system as you can easliy adjust toe in and can't angle after installation...

Ric here's the build link again as the previous one didn't work.

http://www.grainsurf.com/forum/viewtopi ... 71&start=0

[zimboflyman]

Wow

So i finally got my board in the water and i'm blown away!!!

Took most of the advice offered here and on sway locks and from Kevin Slater,
''Put the fins in the std position ie, measuring from the tail >>>rear of rear fin = 80>100mm, and to rear of side fins = 280mm . Make sure your side fins are only toed in 5mm from the back of the fin to the front of the fin measured @ right angle to the center line. ( Most std surfboards are at 7>8 mm )

so basically a tiny bit forward than normal and a little less toe in..
and man the board rocks!!!
the extra rocker didn't really adversly affect her.

she turns on a dime but with plenty of bite. very very stable when putting weight on the front foot - maybe casue of the narrow tail but quite wide middle? so she's got this awesome combination of being very loose when on the back foor and very stable on the front foot.

The feeling of hollow wood is just so alive and vibey!!!

and the flex is spot on.

wasnt much in the way of waves but the few i caught - she seemed to just lock in.

so --- needs more testing - but I'm super stocked!!!

thanks again for the advice...