Understanding the relationship between CLP and CE in sailboat design.

[Caldera Boats]

I have a few questions about CB location that I need to learn more about.
Can anyone recommend a good book or reading on this subject?

Is there a good standard theory for finding centerboard location?

Normally, the sail plan C.E. is located ahead of the hull's CLP by a percentage of the boat's waterline length.

What percentage for gaff verses other types of rigs?

What others factors need to be taken into consideration?

How can I ensure some (but not too much) wether helm?

I understand that formulas will only get me close and the final tuning will need to done during the testing stage.

Thank you for your input...

R.M.Domico

I think you can find a lot of info under the "sailboats" section of the forum. There is an active thread now on Center of Lateral Resistance and since the subject comes up frequently if you search you'll find more threads..

[RHough]

I have a few questions about CB location that I need to learn more about.
Can anyone recommend a good book or reading on this subject?

Is there a good standard theory for finding centerboard location?

These are "The Rules"
http://home.clara.net/gmatkin/therules.htm

What percentage for gaff verses other types of rigs?

Lead (CE forward of CLR)*
From various designers:
Shallow hulls with fins: 12-14% LWL
Deep hulls: 10%
Classic Cruiser: 8%
Scow: 5-15%
Centre Board Yacht: 7-11%
Normal: 6%
Schooner: 7-12%
Ketch: 11-14%
Yawl: 12-15%
Sloop: 13-17%
Flat Bottom: 0%
Sloop: 7%

Doesn't help much does it?

I've been looking at this for the last month or so. I'm getting close to a solution.

*One of the problems is in the definitions.
CE= GEOMETRIC center of sail area
CLP, CLR, CLA?
It seems that what most use as Centre of Lateral Pressure is the geometric centre of area below the water line. Sometimes noted as CLR or most correctly CLAh (Centre Lateral Area hull)

The first phase of my research is to compute the centre of forces and compare that to the centre of area.

If they are the same (I do not believe they can be), I'll be done and no better off than the list above.

If (as I suspect) they are different, I will also look for a similar relationship between the Centre Lateral Area sail (CLAs or CE) and the true CLPs.

Once the true centres of pressures are defined the effect of lead can be quantified and "correct" lead can be computed rather than guessed at.

The range of 0-17% of LWL is too broad to use as a design tool IMHO.

I hope to have some thoughts to put up for comment before Christmas.

The working tiltle for the work is "Leeway for Dummies" thanks to one of our forum members, SuperPiper.

[Caldera Boats]

Thanks,

Nice research, Rhough!

I think I may have a few more questions than answers at this point and it sounds like I'm not the only one.

Cheers........

I will move this topic over to the Saiboat forum.

R.M.Domico

[Stephen Ditmore]

Have a look at my post #4 at http://boatdesign.net/forums/showthr...highlight=lead

[atahawaii]

This topic covered in Dave Gerr's book "Nature of Boats," and Arthur Edmunds "Designing Power and Sail" and in numerous other books.