Pointing higher?

shemandr

shemandr

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Jan 1, 2006
7,076
Slickcraft 26 Sailfish
One thing you should factor in is that an airplane wing is let's say 50' and the airplane is traveling at over 100 mph. A sailboat, maybe 6 knots. The wing is what? A few square feet. So as Jackdaw says, and he would know better than me, not much lift. When we speak of lift of the keel, we mean lift to windward. The foil creates a vector component towards the wind. We don't mean lift as in lifting the boat out of the water. I'm not sure that would be a plus either since displacement boats speed increases with a longer waterline.
Yes the wings get weight of the keel low but so does a bulb and it has less drag.
If you try to delve too deeply into the physics of sailing you go from Newtonian to Quantum Physics in a, well, quantum leap. There is a book - The Physics of Sailing which you might find helpful and which is not too math heavy.
 
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justsomeguy

justsomeguy

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Feb 20, 2011
7,993
Island Packet 35 Tucson, AZ/San Carlos, MX
About the only real difference between aerodynamics and hydrodynamics is that the sailboat's medium, water, is over 800 times as dense. This tends to make a relatively small and slow keel (compared to a larger aircraft wing) somewhat "equal" in lift generation.

But I'm not gonna do the math. :yikes:
 
Jackdaw

Jackdaw

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Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
shemandr said:
One thing you should factor in is that an airplane wing is let's say 50' and the airplane is traveling at over 100 mph. A sailboat, maybe 6 knots. The wing is what? A few square feet. So as Jackdaw says, and he would know better than me, not much lift. When we speak of lift of the keel, we mean lift to windward. The foil creates a vector component towards the wind. We don't mean lift as in lifting the boat out of the water.
Click to expand
That.
 
SG

SG

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Feb 11, 2017
1,670
J/Boat J/160 Annapolis
Actually...If you're interested...

It's not just the keel, but the rudder...

 
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LakeShark

LakeShark

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Sep 15, 2016
799
Catalina 22 Minnesota
You guys are great. I was thinking of the lift just in terms of the wing portion and not the horizontal part of the keel and the rudder. While I cant say I have mastered this I do believe I now understand better how lift helps me point and how to keep better speed through a tack. Thanks @SG for the video as it really helped me visualise all the forces involved.
 
Jackdaw

Jackdaw

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Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
One other thing about rudder lift.

Boat that do not point super well (like the cat22) are MUCH more susceptible to weather-helm caused drag on the rudder.

All boats slide slip when going to weather. Some more than others/

So as the natural side-lip angle of the boat going to windward goes over say 4-5 degrees, you have to factor in (always) rudder action that ADDS to that, and at some point (10 degrees?) the rudder will begin to stall and slow the boat.


Boats with less slip can handle more rudder angle before stalling. Really watch your weather helm and reduce it with sail trim.
 
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Ben Jammin

Ben Jammin

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Aug 23, 2016
34
Hunter 30 Chula Vista
When I've crewed with other racers, I notice I really have to crank down on the genoa sheet when going upwind. Have you tried handing over the helm to a crew member so you can put some extra muscle on the winch? And regarding weather helm, if you have the main trimmed as tight as possible but can't point that high because of the genoa, the main could be overtrimmed and pushing the aft end of the boat leeward (and you should feel it in the tiller). If you haven't already, try easing the main almost until it luffs once you're pointed as high as the genoa will let you. This probably won't get you pointed higher, but could help keep speed up. Someone mentioned crewing with other racers, I think that's a great way to learn the tricks to getting a little more speed, although serious racers may not want the young ones on board.

Someone referred me to a place in PA that reconditions old sails, called Sail Care. I haven't tried them yet, but maybe they could get your sails in better shape with less investment.
http://sailcare.com/index.shtml

I think it's great to get your kids involved at that age. I practically have to pay my 16 year old to sail with me now, and then he lays in the cabin using his phone. Enjoy it while they aren't teenagers! And hopefully they'll grow to love it and keep doing it even then (I had a Hobie 16 as a teen and loved it, and of course it was a better chick magnet than any car!).
 
C

Cayennita

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Nov 28, 2009
495
Catalina 30 St. Croix
Heeling eliminates some side slip because if the wing. If the wing is horizontal your draft is less. Heeling increases some what. Look at the Americas cup monohull. Long wings to increase draft that the increases lift.
 
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