[shopkins]

Could someone please explain to me the finer points of sail trim--and the aerodynamics involved--of motorsailing? Am I correct in saying that motoring creates apparent wind which, as it flows past the main, establishes low pressure on the windward side of the sail so it is helping to pull you forward? If you have no wind other than apparent wind dead on the nose, how do you establish what is "windward," and how do you trim the sail?

thanks all

Susan

 

[Jeff_H]

Most people that you see ''motorsailing'', in light air or going to windward, are not really getting much drive from the mainsail. Instead the mainsail is acting to steady the boat and dampen uncomfortable motion. In order to actually obtain drive when you are ''motorsailing'' you need to have a pretty good amount of wind (on most boats something well over 5 knots) and the true wind needs to be well aft of a beat. In those conditions, when you look at your masthead fly it will look like you are beating or close reaching with the masthead fly clearly on one tack. It should be noted that in really light air, your mainsail offers more drag than propulsion and the slatting that can occur in a light air chop can age a sail far worse than a heavy air sailing day. I generally avoid ''motorsailing'' because if there is enough wind to get more drive than drag there is usually enough wind to sail. And if there is not enough wind to produce more drive than drag I strike my sails to preserve their lifespan.

Good sailing,
Jeff

 

[BigRed56]

Ahoy shopkins, If a boat hook falls in the water and nobody hears it did it really make a splash? The answer is yes you are creating apparent wind by motoring and the direction is exactly the course you are steering with the engine (why?) . If as you said there is no wind (other than that created my the engines foward progress ) then you should trim the sail to the point that its shape is full (no backwinding ). Any heel you get helps with motion as Jeff said. IF your profile heeled produces less drag then you might gain some speed. I have a design for an uphill siphon I like to sell you. Big Red 56

 

[shopkins]

And I''ve got some ocean-front property in Arizona. Well, thank goodness I''m not crazy. In my original writing I was going to end with "this just doesn''t make sense to me," but I deleted it because I assume that because I see people doing it, it must be a valid concept. Saw 6 boats in a pack around Bloody Point Light last summer motorsailing DOWNwind in light air, mains luffing, and just could not figure out what they were accomplishing. Wouldn''t you go ahead and swing that boom out there to take advantage of the slight breeze aft?! Duh. Who wants the engine on anyway. But I''ll still experiment and see what happens in different conditions.

"Steadying the motion" does interest me, however, and leads to another question: what is the most comfortable way and best strategy to deal with a 2-foot (or more) Bay chop? Here''s a situation where motorsailing won''t work for me even if I wanted to. My prop comes out of the water when the stern is hanging over the "chop trough" on starboard tack. (I guess if I only run the engine on port tack and make those tacks the longest, I''ll make really good time!)

 

[Jeff_H]

The best way to deal with the Bay''s chop is to stay under sail if there is enough wind. Don''t go straignt into under motor and don''t take it on the aft quarter under power. Otherwise narrow beam and long waterline length helps a lot! 8^)
Regards
Jeff