CE to CLR/mast position

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11 February 2008 at 19:37 #12451
androot
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@androot
Hello its me again. I’m still struggling to find the position of the mast even knowing the centre of effort. I found some info given by some guy but i cant get my head around that. He said: "….. Your method is simply finding the CLR (center of lateral resistance). This is not where the mast should go! This is in basic terms where your center of your keel should be. Your mast position would be related to your CE (center of effort) of your sails. All sailboats operate with a lead, usually described in a percentage of your water line to the relationship of the CLR to the CE. In a standard Bermuda rig, it is usually about 17% or more.
Setting your mast at the CLR will push the CE way too far back! To find the CE of your sails; draw a line from the tack to the center of the luff and another from the tack to the center of the leech. Where these two lines intersect is the center of effort for each sail. Draw a line that connects the two sails CE and the midpoint of that line should be close to the CE of the whole rig. Find your LWL and the percentage of lead and set your boat up that way….." How do i know the relatioship CLR to CE when i dont know where the mast sits….

I still dont know what is going on, can somebody explain me how to find the mast position or help me understand the stuff

PS I’m reading second book and still no hope.
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12 February 2008 at 17:29 #12453
Len Ochiltree
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@lenochiltree67043
Hi Andy,

I have never understood it either.

I have a Thames Barge and belong to AMBO (Association of model Barge Owners) try their web site.

http://www.modelbarge.info they have lots of well informed members.

hope they can help.

Len
12 February 2008 at 18:42 #12454
Bob Abell 2
Participant
@bobabell2
If I were you Andy……………I`d make the mast adjustable………and play with it!

Best of luck………Bob
12 February 2008 at 21:28 #12461
androot
Participant
@androot
Adjustable mast is not being taken into account. Just want ot make nice looking and offcourse sailing boat. I’m not going to compete. Because I’m a modelmaker i want ot make this boat look as real as possible. Maybe in the end I’ll just put the mast 10-20% (lengh of the hull) of the CLR towards fore, I read it somewhere….

Thank you

Andy
25 February 2008 at 22:25 #12629
Tony Bell 2
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@tonybell2
I am looking at the design specs for my first scratch boat the "Jolie Brise" I have not found out what is the correct "Lead" (leed) but I have found out how to calculate it. Displacement, Metacentric height, Centre of Bouyancy, Wind Speed/loading etc.

Goto http://www.joliebrisemodels.co.uk/french/specification.html
1 March 2008 at 18:40 #12695
Tony Bell 2
Participant
@tonybell2
It appears that the position of the mast is not the major point of concern. It simply holds the sails up.

The Centre of Lateral Resistance CLR is the point about which the boat turns. The Centre of Effort CE of the sails should be forward of the CLR to create weather helm to balance the boat. The difference between the CLR and CE is the Lead (pro Leed)

The following source give a Lead of 2.5 to 5% of Water line lenght.
1 March 2008 at 21:05 #12701
Tony Bell 2
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@tonybell2
Continuing on from last post

http://www.swcp.com/usvmyg/design/design.htm at end.

I found an article which said the CE should be behind.

Ted Brewer’s site is useful http://www.tedbrewer.com/yachtdesign.html

My own gaff boat has the mast at 40% CLR at 56% including the rudder. CE is 50% (lead +6%) with all 5 sails set. 53% (+3%) with Jib, Staysail, Main, 66% (-10%) with Staysail and Main.

Goto http://www.joliebrisemodels.co.uk/french/specification.html#coe to see calculations
9 January 2009 at 19:20 #1515
androot
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@androot
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