Calculating CE when you have multiple sails/masts

[Yeadon]

I've been able to calculate the lead between my sprit sail's center of effort when compared to the center of lateral resistance of my boat ... but I'm curious, what is the formula to calculate the CE of multiple sails?

In this case, I'm considering adding a mizzen to my sprit-rigged boat ... in turn becoming a cat-yawl. I'd like to begin working out the square-foot size of the mizzen, and the location of the rear step.

Anybody either have this formula, or could point me to a good reference book?

[Steve Lansdowne]

Todd Bradshaw's book (p.85) tells how to do this, and I seem to recall a posting on the subject also. Try the search function. Todd says to calculate the CE for each sail, then draw a line between the two, and set down a perpendicular from each sail's CE; make the lengths of these perpendicular lines "reflect the size of the opposing sail in come convenient unit of measurement. The tips of the perpendiculars are connected with a line, and the point where that line crosses the line connecting the centers is the total CE for the sail plan." Get the book for the diagrams so this makes the most sense.

[Thorne]

It should be in a lot of books, as this is often encountered for sloops. I think it is in Bolger's 103 sailing rigs, but am not sure...

[Todd Bradshaw]

Damn...pretty soon I'll have a pdf for everything and won't need to post any more, with the exception of an occasional rant....

http://webpages.charter.net/tbradshaw/C.E..pdf

[Yeadon]

Thanks Todd. That's a great pdf you have there. I'm printing it right now.

You have a book? I'll take a look for that.

This is going to be a fun project.

[Steve Lansdowne]

You won't believe how enjoyable and instructional his book is! Canoe Rig: The essence and the art.

[kc8pql]

It's here: http://www.woodenboatstore.com/prodinfo.asp?number=325-110

[john welsford]

Skenes Elements of Yacht Design, Yacht Designing and Planning ( Chapelle) Ted Brewers book on yacht design, pretty much any of the standard texts will do.

JohnW
I've been able to calculate the lead between my sprit sail's center of effort when compared to the center of lateral resistance of my boat ... but I'm curious, what is the formula to calculate the CE of multiple sails?

In this case, I'm considering adding a mizzen to my sprit-rigged boat ... in turn becoming a cat-yawl. I'd like to begin working out the square-foot size of the mizzen, and the location of the rear step.

Anybody either have this formula, or could point me to a good reference book?

[jerry bark]

any introductory calculus text will have it as well. look for the section covering centroids and center of mass. in the case of CE you substitute sail area for mass and compute the x-component of the centroid of the sail system. viola!

cheers
jerry
wood boat owner, math nerd

[dm_scott]

Dave Gerr in the Nature of Boats spells it out pretty plainly also.

[Carlsboats]

One more source: John Gardner's Classic Small Craft You Can Build, pub. by Mystic Seaport, shows a simple way of doing this graphicaly.

[Hwyl]

Damn...pretty soon I'll have a pdf for everything and won't need to post any more, with the exception of an occasional rant....



This post made my day, I hope Todd feels appreciated.

[Todd Bradshaw]

I'm preparing a rant about that subject.....:)

[Jay Greer]

Besides being a good read, L. Francis Herreshoff's "Common Sense of Yacht Design" spells it out in simple terms.
Jay