I am playing around with sail designs and am wondering if roach is considered when determining a sail's center of effort. If it is, then how does one go about figuring both the area of the curve and its centroid? Thanks.
3 replies to this topic
#2
Hirilonde
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Posted 20 June 2011 - 09:49 AM
I am playing around with sail designs and am wondering if roach is considered when determining a sail's center of effort. If it is, then how does one go about figuring both the area of the curve and its centroid? Thanks.
You absolutely need to consider the whole sail, roach and all. If you are designing the sail then you alone know the dimensions, if the curve of the roach is a constant radius, etc.. Without this information I don't see how anyone can help you. Are you using a design program in your playing around?
Dave Finnegan
http://charlestownboatworks.com
1967 Pearson Renegade "Hirilondë"
Spindrift 9N #521 - many KudzuCraft SoF kayaks
#3
PAR
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Posted 20 June 2011 - 10:36 AM
Actually, you don't need to include roach in the sail plan unless you have a ridiculous amount, like in square topped sails.
If you have a square top, then calculate as a quadrilateral.
Typically, the fore triangle area (half the length of "I" times "J") and the main (half the length of "P" times "E") are used for sail area, again unless you're doing something "special". If you are doing something special, a better grasp of the fundamentals would be in order.
If you have a square top, then calculate as a quadrilateral.
Typically, the fore triangle area (half the length of "I" times "J") and the main (half the length of "P" times "E") are used for sail area, again unless you're doing something "special". If you are doing something special, a better grasp of the fundamentals would be in order.
#4
W. Micawber
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Posted 20 June 2011 - 11:49 AM
PAR and Dave, thank you for your responses. The sail is a standing lug of about 154 sq ft w/o the roach. I did not post dimensions because I was looking for a formula for figuring roach area so that I could account for it in finding the true center of effort. I am scribbling this on paper and not using a computer.
The dimensions of the sail are:
Luff 8'6"
Head 12'4"
Foot 13'6"
Leech 17'10"
Sail area is roughly 154 sq ft. I want to put in a 12 inch roach in to give me an idea about how much more sail area it gives and to maybe whittle that back until I have about 160-165 sq ft of sail. When I drew the leech, I just plotted points and struck an arc from clew to peak. This may not be the way to do it, but I cannot say that I know anything more than what my scribbling has produced.
The dimensions of the sail are:
Luff 8'6"
Head 12'4"
Foot 13'6"
Leech 17'10"
Sail area is roughly 154 sq ft. I want to put in a 12 inch roach in to give me an idea about how much more sail area it gives and to maybe whittle that back until I have about 160-165 sq ft of sail. When I drew the leech, I just plotted points and struck an arc from clew to peak. This may not be the way to do it, but I cannot say that I know anything more than what my scribbling has produced.
