SailNet Community - View Single Post - Mast Rake for Cape Dory 30
View Single Post
post #3 of Old 07-30-2001
Join Date: Jul 2001
Posts: 96
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 16
Mast Rake for Cape Dory 30

Ahoy, Bob Ohler. Regarding your 7-13 on mast
rake, may I comment. Kevin is right about your mast rake. If your mast is raked aft and
you still have lee helm, you do have a problem.
Visualize with me a moment. Think of your
boat as a wind vane. The point on your hull where you could push your boat and it would move straight side ways with out falling off at either the bow or stern is the center of
lateral resistance of your hull. Let me call
it the pivot point for sake of visualization.
Now, take a piece of paper and a pencil and draw two triangles representing the foresail and main. Draw a straight line from the point of the clew to the midpoint of the
luff and from the point of the tack to the midpoint of the leach. Do that in both triangles. Where those lines cross is the geometric center of the sail. Now connect the
point in the jib to the point in the main with a straight line. Finally, assume for reference sake that the fore sail is 60% of the total sail area and the main is 40%. Start at the center point in the jib and move
toward the center point in the main 60% of that line connecting the two. Put a point there. That point is the center of effort of
your sails (it is the geometric center of your total sail area).
If now that point is directly over the pivot point, your boat is in balance and will
not fall off by either the bow or stern.
Now visualize that you rake your mast forward. You move more sail onto the jib side of the point that was your center of effort, creating a new center of effort in front of the pivot point and your boat will now weathervane by the bow, spinning around the pivot point. You will then have to put your tiller down to compensate, thus lee helm. Though it isn''t the kosher way to do it, you can relieve lee helm by raking your mast aft, and relieve weather helm by raking it forward.
I suspect, though, with Kevin, that it is
your sails. You have too much canvas in your
foretriange. Masts on cutters, as you know, are stepped in the center or very near the center of the boat so there will be more room
forward to carry two sails.
I suggest you try this. With your mast straight up, get sailing with your full suit of sails. Now drop the staysail and check your helm. Then hoist your staysail and drop your jib and check your helm. That will show
you the amount of shift in your balance with
different sail configurations and should point to the culprit if it is in fact your foresails
I suspect, though, that it is your main.
I would say call the manufacturer and ask them for the measurements Kevin was talking about, the I.P.E. of all three sails as they were designed to be. Measure your sails and
compare to the designed measurements. You probably do not have the suit of sails that boat was designed to carry.
Finally, I''m a purist and a traditionalist
where boats are concerned. Possibly because I
am a bit of a romantic. I love gaffers and cutters. And, too, maybe it is because I use to sail with a buddy who had a cutter and we spent so much time short tacking up rivers.
Didn''t mean to insult your intelligence or
to take so long. It''s easier when you can draw pictures. Drawing them with words is tough sometimes. A sailing boat is just a resolution of forces. Track the bad guy down.
Good luck.
dhartdallas is offline  
Quote Share with Facebook
For the best viewing experience please update your browser to Google Chrome