Bic 293

Question
QUESTION: Hi Windlover!
I will be taking out soon ( weather permitting) my brand new Bic 293 D, which comes with a standard 38 cm fin. The board is 205 lts,  80 cm wide. I have replaced the standard 38 cm fin with a 50 cm fin  because  I抎 be using my board only in light winds and large sails ( 7.5 and 8.5).
1. I was thinking that the more a board  floats on the water, the less it sinks, even marginally, under the sailor抯 weight ( in my case, 83 kg), therefore it would be ?readier?to rise off and above the water for planing. Am I right? Does a higher floatability of the board in terms of volume really facilitate planing, everything being equal?
2.Does  the fin lift come into play ( and literally lift the board) only when planing, or does it work also in subplaning, by  perhaps facilitating the movement of the board through the water or increasing its speed in light winds, even when it does not plane ?
What should I expect?

Thank you

ANSWER: Hey Franco,

1. Higher floatation does not mean faster planning. Quicker to plane is all about hull/fin design and weight of the sailor and rig.

2. The fin will create little or no lift when sub-planning. Lift starts happening when the board speed gets really close to the planning speed. Fin lift requires a certain amount of board speed combined with lateral pressure against the fin.

Hope this helps,
Keep on sailing,
Windlover

---------- FOLLOW-UP ----------

QUESTION: Thank you!

Understood!Higher floatation, then, does not necessarily mean earlier or faster planing.

Regarding the necessary pressure on the fin to obtain lift, how  is it  to be exerted? I seem to have understood from my readings on foil water-dynamics that you have to push away on the fin while at the same time banking  on the leeward rail in order to raise the windward rail. This  will  in turn  tilt the fin laterally towards the windward side, thus creating an angle of attack. This angle of attack of the fin will be such   that the water pressure on the  windward side of the fin  will be higher than on the leeward side and this will create lift,( barring, naturally, an excessive angle of attack, which will create the dreaded spin-out). This procedure seems to be in line with the basic principles of physics in foil aerodynamics,as I understand them,  but other sailors simply speak of pushing DOWN and AWAY  on the fin, without necessarily banking on the leeward side. What is your take on this?

Thank you

Franco

Answer
Hey Franco,

I don't try to analyze things quite so much. I just push on the board to get planning and cruise. But much of what I do is just natural habit from years of sailing. It's hard to put into words what is causing all the fun I'm having. So, I've found a couple of good articles written about fins by windsurfers. Lots of good information about size, styles, lift, etc.

The third link includes some great information from one of the best instructors out there, Peter Hart. He has good videos and written articles regarding all aspects of windsurfing.


http://www.rikswindsurfing.com/support/access/fins/index.html

http://www.windsport.com/gear_article?news_id=3

http://sites.google.com/site/learnersguidetowindsurfing/peter-hart

Hope this helps.
Keep on sailing,
Windlover