Bullet Fins

'... were invented in the 2005 by Ron Pettibone to increase surfboard hull planing and rail-to-rail transition speed. The patent-pending fins are based on 50 years of hydrodynamic research on the bulbous bow hull design. Just as with the bow of a ship, the traditional surfboard fin creates a wave as it displaces the water in its path. The resulting turbulence places drag on the surfboard.

The bulb of the Bullet Fin reduces this drag by creating a new (primary) fin wave in front of the original (secondary) wave. This new bulb wave is designed to be nearly 180 degrees out of phase with the original fin wave to subtract its turbulence thus reducing fin drag'

Interesting design characteristics. Anyone tried these out or heard from someone who has?

cool

I'd eat my fin if this works.

The 50 years of research backing up this design relates to the hydrodynamics of large ships. I don't see any similarities between tankers and surfboard fins. Without getting into the science i think the fact that racing yachts don't have bulbs where the keel meets the hull should be enough evidence that this doesn't work.

Mind you there's only one way to find out............

(By the way, some yacht keels do have bulbs on the end but this is simply a lead weight to stabilise the boat.)

While we're on the subject of drag. I spent ages getting the bottom of my board smooth and getting my trailing edges nice and sharp, but because the base of the fin doesn't fill the 10' box there's a big gap. This gap will cause some degree of turbulence and drag.

anyone know anyway to fill this gap, cork or something? does anyone bother filling this gap? does it matter?

would cutting down on my kebab intake have a bigger effect on drag?

Yeah, I'm not convinced. Looks like they would create drag.

it doesnt matter, the amount it produces is not really noticable

The concept is to basically clean up the water at the base of the fin, which is the widest part of the fin and so contributes to the most drag and potential for stall at the critical point in a turn. In theory the turns should be faster and smoother.

There are about 4 ways that this has been approached for surfboard fins.

One way is to have mini fins slightly in front of the main single fin(inline-single)

http://www.truenorthsurf.com/BiFin.html

, or in front and beside the side fins(Superchargers)


Another way is to have a couple of mini tuna like fins in front of the single or center fin. (Multi Vortex Generators MVG)
http://www.swaylocks.com/forum/gforum.cgi?...;guest=11995894

The other thing to do is to reduce the length of the base of the fins. (Mental Template fins)
http://www.swaylocks.com/forum/gforum.cgi?...ostatt_id=1062;

I have tries a few of them, they all work to some extent. My favourite is the MVG, just peel off the backing and stick them on. They are in not production at the moment, I was lucky to be sent a couple by the designer. They make the botton half of the top turn( The part I usually fall off in!) much smoother and faster.

I'm definitely a convert.

It seems to me that you should be able to make a little bulb to fit to the base of an existing fin maybe from balsa and attach to the fin with some epoxy adhesive to test the concept.

i used to windsurf quite a bit.

some of the new boards i had came with a plastic channel section which you cut to length and used to fill the gap. (there was a little stickie out bit which located into the groove where the fin bolt goes to hold it in place.) you might be able to pick up some of this?

i used to fit it religiously. it would then come out and i'd never notice the difference.

Then you just werent doing right

I always wondered about the holes left if you dont use the side biters