Bonzer Query

QUOTE (Burnsie @ January 08, 2008 07:32 am)

The official word is that the the fins along with the single to double concaves work on the venturi principle. forcing the water flow through a narrow opening creates speed.

Personally I don't buy into the theory, because the board creates the speed on a rail.

IMHO The speed comes from grabbing the wave energy from a big rail fin (with 18* of cant) then using the hold from the center fin to give the effect similar to a bar of wet soap being squished between your fingers, its projected forwards.

The reason for the 2 rail fins instead of one is simply that it makes it easier to turn while giving the same speed. (Same as a speed dialler Quad Vs Keel fish)

The deep concaves, which some bonzer designers say are unnecessary are there to allow the water pressure built up by the rail fins to release. What is also significant is the amount of V in the tail to loosen up the board. However this also limits the board to waves with a bit of push.

Again this is just my theory on Bonzers and not the official version.

What I recon is...The venturi effect needs a small bit of pressure build up before speed in the water is created. Therefore the wave needs to have more power/steepness/speed. The alternative to wave power, i guess, would be the larger sized surfer, in order to put pressure down and forward on the board. This would explain why these board work well in waves with a bit more 'power'.

The fins, on the other hand really interest me. The angle of cant is huge. I think the angle is so sharp because the boards work best in steep waves, so a more acute angle = more hold. Maybe they add to the venturi effect too. I havn't studied them in too much depth.

Also, the shape of the fins is really nice. The fact that they are so Hydrodynamic and the way the front blends so gradually to the board. i think all the properties combined, really make the board work. Varying some of the properties, i think changes the waves they are best suited too.

Also, I think, if the Venturi principle was applied to a really small board for a really light surfer. With the right design, I think this could work very well.

There's my two Cents.

I have to admit I don't buy into the venturi principle on bonzers for a number of reasons.

1. For Venturi to work the whole bottom of the board has to be fully engaged yet bonzers only turn on when put on a rail on the bottom turn.

2. Duncan converts many pro's standard shortboards into bonzers on the North shore with tiny concaves or deep singles.

3. AC Elliot have been developing bonzers for Eaton for the past 30 years has dispensed completely with concaves. (he goes roll to vee now)

What is hard to see in a bonzer is that there is a huge amount of Vee in the tail. This is very significant, and also why they suck in crappy waves.