> I bought a new 21" race fin for my early planing board.
OK, let's see, 21"= 53.3 cm, so I'm guessing it's a 54 cm fin, right?
Or did you purchase some fin that's measured in inches?
Interesting. Most race fins are sized in cm or mm. Only smaller weed and
wave fins are normally measured in inches.
> It got used for the first time last weekend. While putting my gear away after I got home, I noticed cracks had developed on both sides of the fin base. It's hard to
> describe. but imagine the fin being a certain thickness (layer A-fin).
> Then, imagine the added thickness necessary to build up each side of the
> base (layer B-left and B-right). The cracks are developing in between the
> layer A-fin and layer B-left, . cracks are symmetrical so the plane between
> A-fin and B-right is cracked as well. . get it.?
Sounds like you perhaps didn't fit your fin in the box, and either the
tapered or not thick enough, or the box is tapered and the fin is only
fitting down in the bottom of the finbox. I.E. the area of the fin root
the bottom of the board is not being supported by the fin box, due to an
fit between the 2.
Is this a standard depth Tuttle fin, Deep Tuttle, or something else. If
powerbox, that's an awful lot of fin span for a powerbox. If it's a trim
it should be OK, but it's getting near the too much span for the finbox
If this is a G-10 fin, with a molded on fin root (Tuttle/Dp. Tuttle/PB
then I would take it back where you bought it and see what they say.
But if the root was unsupported by the finbox, either due to the fin
or the finbox, that is something that you might consider checking
get a new fin. They have to fit tight, or they do not support each
> I've never broken a fin before. I only weight 150lbs and sailed one 5-15mph
> day with this fin. It should not have cracks as far as I am concerned.
I would agree, it everything fit correctly.
> Does anyone know how these large fins typically break with heavy usage?
I've never broken one. Can you tell me by personal email what brand of
it is, and what the material used to mold the fin root is?
> I believe my fin box should break out before my fin should break (not that I
> want this to happen or anything). Doesn't this sound like I got a
> defective fin?
Yes, but it could be an improper fit, which caused the fin root to
Are the cracks across the axis of the fin, or along the axis of the fin?
> Any thoughts on whether G10 is the right material for large fins?
It usually works extremely well, but it does not have the longevity of
a molded or CNC machined carbon fin. G-10 fatigues relatively quickly,
when compared to carbon layups, either molded or molded CNC.
I think I'd take it back and see what the shop has to say.