FrontierFolk.net

Jim Hart · Joined: 19 Jul 2010 Posts: 27 Location: Northern KY

Is there a proper place to put a leeboard in relation to
the mast?

The info I've found seems to expect a level of knowledge
or experience that is a little greater than I have at the
moment.

I've found this page and was going to base my leeboard
on info from there... but it doesn't say if there is a optimal
position that it should be mounted at.... ( unless I missed
that... re-reading it in a moment... )

http://www.enter.net/~skimmer/building/building.html
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Jim Hart

Medieval Re-enactor branching out.

If I look distracted the voices in my head are probably doing a stand-up comedy routine... give them a minute to finish the joke..

shortstarter · Posted: Fri Jul 23, 2010 9:57 am Post subject:

I need to move my lee board forward to get a better point. I C clamped some ruff cut boards and sailed one day to find the sweet spot.

I like the rig you posted and will try to make a similar rig for my boat.

Waterman · Joined: 02 Jan 2005 Posts: 55 Location: Tidewater, VA

Actually, the placement of the mast is related to the center of lateral resistance. Don't have my references available, will look tonight. That said, center of lateral resistance (leeboard down) should be slightly aft of the center of effort of the sail(s).

Cheers, Bill

Waterman · Joined: 02 Jan 2005 Posts: 55 Location: Tidewater, VA

According to Howard I. Chapelle,

"In centerboard hulls, the lead varies in general as the draft." "In shoal scows, sharpies, and V-bottom hulls having centerboards but little or no skeg or external keel, only the centerboard and 1/4 to 1/2 the rudder area are usually considered and the lead is usually .02 to .05."

This means that the center of effort should be about .02 - .05 of the length of the water line forward of the center of lateral resistance.

Cheers, Bill

Jim Hart · Joined: 19 Jul 2010 Posts: 27 Location: Northern KY

Waterman · Joined: 02 Jan 2005 Posts: 55 Location: Tidewater, VA

Jim,

You should try to decipher his instructions for booms and spars.

Bill

TomMacD · Joined: 30 Jan 2008 Posts: 100 Location: Harnett County, NC

Paul Daiute, please look away!
A boat designer named Jim Michalak posted a fairly simple explanation of sail center of effort and leeboard/centerboard position on his website. I found it through a link marked "Boards and Keels" on the left hand side of the homepage of the website www.PDRacer.com. Once you get to Mr. Michalak's website, scrool down to "Sail Area Math."
Perhaps this will help.
OK Paul, you can look now!
Tom
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