why canting keel?

wow... getting hot?

I am glad to hear from you. thanks.

what I am wondering is this.
In my rough calculation, the canting keel shows maximum 33% improvement of righting moment than fixed keel (both has same VCG position), not fixed keel+water ballast.
This means the sail area can be increased 33% than fixed keel and somehow,
this is beneficial to increase the driving force of boat.

But my wonder is why all the canting keeler were defeated in recent vendee globe (Riou used fixed keel), even canting keeler has better performance? This would be absolutely depends on the apparent wind direction where canting keeler has no benefiecial aspect. something like runnig.

I geuss there would be some limitations when employ this canting sys.
something like boat's course, sea state,wind strength, ballast ratio, sailing distance, etc.
Do you have any informations about this? which factors affect the performance of canting keeler?

Am I too naive?

 

Limitations

Under some race rules the effectiveness of a canting keel can be somewhat limited and use of the various canting systems have to be analyzed carefully in those applications.
Some examples that come to mind are the Open 60 and Open 6.5 rules(and probably the (Open 40's and 50's) which are limited to a 10° static heel with the canting keel at max cant(hence the wide beam). The Sydney-Hobart Race has the same limits on participants. The Volvo race boats are limited to 40° cant angle.
Compare that with some high performance canting keel systems like CBTF that function best with max cant angles of 50-55°.
And then there is Julian Bethwaites new 26' canting keel sportboat: max cant angle 60°!
One thing for sure is that a canting keel design must be done very carefully to integrate the extra lateral resistance required without too great a penalty especially under some of the restrictive rules.

 

thanks doug,

Yes, I think so.

In my rough calculation, the heel angle is 25 degree and canting angle is 55 degree. (somewhat extreme condition, I think.. and I want to drag out more general formulae for that!)And the additional GZ value by canting is somewhat combination of sine and cosine with regard heel angle and canting angle.

I felt that there are numerous factors which affect the canting keel performance including the laterial resistance, you mentioned.
Even I felt that the waterballast system would be the worst one since it makes GZ value lower i.e. VCG is getting away from the bulb.
There would be some limitations when the canting is employed, absolutely depends on the environment she sails.
This is what I want to verify that what is the environment that restrict the cantiing keel employment?

Cheers

FJL

 

recent seahorse - June

Recent seahorse magazines deal this matter - May and June.
Systematic investigation has done by wolfson unit at Southampton,UK.

This is, I think, a summary of canting keel system. This was exactly something that I wanted to do.
Anyway, there are still so many works left behind us to solve.
Even we know the performance of the canting keel system, still the canting keel is heavily depends on the VCG and VCB.
This would need something optimisation work to go.
Something like how do we optimise the VCG and/or VCB to maximise the stability? Even really many works still remained to go.

Cheers,

FJL