how big a fin for powerbox

[Ville Levänen]

Been thinkin about a bigger sail, around 9 sqm. The problem is that my
biggest fin is 41 cm, which I've been using with a 8 sqm sail. The bigger
sail would most probably need a bigger fin. Something like 45 cm. Right?

The question is if a powerbox will take such a big fin???

Many here seem to be using even bigger sails... How big fin do you use?
And what finbox?

Thanks in anvance for any clarification!

Ville L,
Finland

[Michael Pankau]

Villie,
I sail a Maxx w/o centerboard with a VMax 9.1m2 and a Curtis CR12 48cm
powerbox and the combo has been working quite well. Good Sailing
Mike P
Idaho

[DTran]

I sail Gaastra GTX 9.3m2 on the Hifly Free 282 (widestyle) using Curtis
CR-12 55cm. I believe that Hifly reinforces this board's powerbox for
larger fins. Once I'm fully powered on this sail, I downsize to a 48cm
fin. I only weigh 165 lbs, thus I don't put as much stress on the box as
heavier sailors.

Dan

[Bill Kline]

The two replies are accurate. We provide up to 55cm.
Bill Kline
Gorge Sport USA
Curtis Performance Fins, Orca Fins
Hood River, OR USA
bil...@gsport.com www.gsport.com
ph/541 387 2649 fax/541 386 1715

[Bill Kline]

You do have a point about perils of powerbox fin failure. We use a smaller
barrel nut and put it deeper in our molded G-10 and CG-10 Curtis (and Orca)
fins.

As the first company to develop deep fins, I would have told you five years ago
when the first Curtis and Orca Fins came out that there would be a large number
of powerbox fin losses. Losses have been a fraction of what I had though they
would be.

Loss can happen.The person who designed the powerbox would claim these are not
failures, but the fins breaking out to protect the board if the fin hits
something hard. What I suggest is that you remove the fin and examine the base
anytime you hit something. It may be possible to repair cracks in the base.

Tektonics is an excellent company with an international following. As far as I
can tell, all the aftermarket companies are doing the best possible to minimize
problems.

[Tom - Chicago]

How the h*ll can a $200.00 fin come without a brass barrel nut for the screw?? I
sure wouldn't use one.

(Using Curtis CR12 48 on my Bee 289 w/Retro 9.5. Go down to 42 cm fin when fully
powered.)

Tom - Chicago

RMoore 41 wrote:

> >Was the following also correct?

> >>> I believe that Hifly reinforces this board's
> >>> powerbox for larger fins.
> >

> >If so, are there different recommendations for maximum fin size depending on
> >board?
> >Which would be the max size for my Vision 150 and Equipe (1994)? 55 cm?
>
> The weak link is the single bolt attachment and having to trust the 1/4"+-
> fiberglas just above the barrel nut on the fin. bigger the fin, the more stress
> on this area, more prone to failure. Last year I "HAD" a bueatiful Tectonic fin
> in a powerbox. They don't even use a barrel nut, just thread the filler in the
> base. Second time out "boom" fin failed at the threads. $200.00 gone. No
> warantee, fin can't be sent back as it is at the bottom of the ocean. In
> retrospect I should have drilled out the threads and installed a barrel nut
> down nice and deep. That fin was a spitfire in 40cm. I wouldn't use a fin any
> bigger than a 46cm in any powerbox. I also wouldn't use any molded fin. Solid
> G-10 or laminated polyester is the way to go. Molded fins breakout just above
> the barrel nut or fail at the fin/base junction. Both leading to a long swim.

[Wolfgang Soergel]

Ville Levänen wrote:
>
> Been thinkin about a bigger sail, around 9 sqm. The problem is that my
> biggest fin is 41 cm, which I've been using with a 8 sqm sail. The bigger
> sail would most probably need a bigger fin. Something like 45 cm. Right?
>
> The question is if a powerbox will take such a big fin???

45 cm shouldn't be a problem for a reasonably new board, built with
bigger fins in mind. I'd not recommend a fin with an adapter base over
36-40 cm though but rather one with a molded or milled base.

Generally, it's most often not the power box as such which will make
problems but the material the box is made of (carbon vs. some kind of
mold injected plastic) and, most important, how the box is installed
into the board. Proper installation through the deck, using enough
reinforcements and the right material (e.g. Herex PVC foam) will make
the box plenty strong for any use up to say 50 cm fins, longer for
recreational use. Btw., use imho does not include frequent bottoming out
or hitting objects at warp speed, at least examine the fin base and the
box after any hit!

> Many here seem to be using even bigger sails... How big fin do you use?
> And what finbox?

For really big fins, (deep) Tuttle boxes are the best solution around.

--
Wolfgang