Tuesday, August 17, 2010

Whale inspired fins

Just such a work of art .Inspired by nature ...


Tim Stafford is always experimenting with different things and loves his Bonzer boards.He was making these fins and so I asked him to share how this all came about and what the outcomes have been.

" Hi Grant glad you’re enjoying the fins... pic attached. I started on this route because I made a board I called The Porpoise and wanted something truly inspired by nature for the fins... so I started looking into whales and came across the tubercle principles. This all came out of scientific studies of humpback whales and how they could manoeuvre such a large body at such low speeds in such tight arcs to surround the krill with a curtain of bubbles before diving up the middle for a quick feast. The answer turned out to be the tubercles (lumps/bumps) on the leading edge of their fins... these channel the water and provide both lift and lower resistance. The idea was quickly transferred to wind turbines where they found that the blades could rotate and harness energy at much lower speeds when they applied tubercles to the leading edges. (5mph lowest operating wind speed dropped to 2-3mph making a dramatic increase in viability in low wind areas). Obviously manufacturing costs are a limitation of the concept’s success... I can appreciate that as each pair takes me a full day to foil...

So how do they work, well in terms of manoeuvrability they are unbelievable allowing dramatic changes of direction combined with drive and stability. They seem to get up and go really nicely as long as the wave has a little steepness. In slower waves they performed less well due to placing the bonzer EVO3 side fins too close to the tubercles, this caused excess drag. To test this theory I sanded off the tubercle fins and tested the same board with both a single fin (standard bonzer EVO3) and with quad rear set (EVO4) and the result is better entry speed and slow wave planning, but reduced stability and less manoeuvrability... in essence it lost the magic. It was an important test though as it allowed me to isolate the board itself from the performance characteristics of the fins. The next iteration will be to do it as a twin fin with tubercles... maybe even as a woody!

For me it’s all about applying proven science to surfboard design. Each new idea takes me different places on the wave and that’s what keeps me surfing."

To more understand the science behind the Tubercles check out :

http://www.appliedfluids.com/UUST01.pdf

To keep an eye on what Tim is up to : www.justbonzers.blogspot.com

Thanks Tim for sharing your experience and craft.

2 comments:

Tomas Oberst Kadgien said...

We are in the wale season (ballena franca) here in Mar del Plata, Argentina, and their fins are equal to those !!!
That´s inspiring stuff ...

Congratulations !

Tomas O.K.

olosurfer.com said...

The two tubercules closest to the tip need to be foiled correctly, the others are ok.

http://olosurfer-woodensurfboardsatpipeline.blogspot.com/2010/05/leading-edge-tubercules-for-7-8-jets.html