Mainsail Luff Line?

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Aug 4, 2009
204
Oday 25 Olympia
Your "Sail Trim Users Guide" talks about bending the mast to depower the main.
My O'Day 25 ('76) mast is as stiff as a board with no way to bend it.
What are your thoughts on installing a curved sleeve attached to the main's luff area containing a no-stretch line between the headboard and the Cunningham cringle? Tension on the Cunningham (6:1 tackle) should then gather the sail's luff curve up to the mast for the same effect as bending the mast. I'm looking for a quick way to blade out the main just before the short duration squall hits.
By the way, excellent presentation of the subject matter in your book.

Thanks, George
 
Feb 26, 2004
22,015
Catalina 34 224 Maple Bay, BC, Canada
George, before Don can get to his reply, you may recall that this subject has been discussed many times during sail trim discussions. If you have a "non-bendy" mast, then you simply can't bend it, we call 'em "telephone poles" with good reason.:):):) Only fractional rigs usually apply to that concept, and then not for all boat spars.

Therefore, that doesn't apply. We "telephone pole" skippers employ adjustable backstays to tighten the luff of the jib (forestay tension) and that's about all we can get from that feature.

If it was my boat, I wouldn't bother with your suggestion.

Oh, and we had a Catalina 25 for 12+ years, same issue you described. Wouldn't have done it to that boat either. :dance:
 

Joe

.
Jun 1, 2004
7,505
Catalina 27 Mission Bay, San Diego
kind of like a "shelf luff"? ........like a shelf foot, where an extra section of lighter weight cloth is sewn into edge of the sail so that it folds in on itself when tensioned?

It may take some of the fullness out of the sail but it might nullify the Cunningham or halyard's effect on draft position.

Unless you have a sail design program for your computer you would have to mock up the idea and do some testing.... or... you could go to a sail maker for his opinion and a possible alternative solution to your problem.

Interesting idea though, wonder why it's not been used by sail makers.... that I'm aware of anyway.
 
Aug 4, 2009
204
Oday 25 Olympia
Thanks for your replies, Stu and Joe. I was also thinking of safety for a short handed boat caught out in some weather. I'll renew my search of the archives. Could you suggest some search words? I tried "Main sail luff lines" but the answers came out for each individual word and didn't help much. When I tried to combine the words the result was negative.
 
Feb 26, 2004
22,015
Catalina 34 224 Maple Bay, BC, Canada
I'm looking for a quick way to blade out the main just before the short duration squall hits.
George,

Two things: the traveler or reefing. If your idea had merit (conceptually it might have) I think sailmakers would have been doing it. What you want in gusty or squall conditions is a FLAT sail (which your cunningham provides by TIGHTENING the luff), and it appears that this idea would create bagginess, just the opposite of what you want.
 
Aug 4, 2009
204
Oday 25 Olympia
George,

Two things: the traveler or reefing. If your idea had merit (conceptually it might have) I think sailmakers would have been doing it. What you want in gusty or squall conditions is a FLAT sail (which your cunningham provides by TIGHTENING the luff), and it appears that this idea would create bagginess, just the opposite of what you want.
Thanks for the reply Stu. I have to agree that the idea must have been discussed (and tested?) by sailmakers looking for a market nitch. I must confess also that I've not taken advantage of the traveler as I should. My new main is loose footed with which I haven't had much experience, so perhaps just dropping the traveler may be the most efficient solution.
Oh why do I get so involved with theory, thanks again for bringing my feet back to the ground.
George
 

Joe

.
Jun 1, 2004
7,505
Catalina 27 Mission Bay, San Diego
Thanks for the reply Stu. I have to agree that the idea must have been discussed (and tested?) by sailmakers looking for a market nitch. I must confess also that I've not taken advantage of the traveler as I should. My new main is loose footed with which I haven't had much experience, so perhaps just dropping the traveler may be the most efficient solution.
Oh why do I get so involved with theory, thanks again for bringing my feet back to the ground.
George
George, with a masthead rig, especially one with a stiff mast, the outhaul is the primary DRAFT DEPTHcontrol.... a loose foot mainsail will allow you to easily see the changes made in the lower third of the sail. The halyard and Cunningham will control DRAFT POSITION
it does not necessarily make the sail flatter... but rather positions the deepest point of the draft
along the horizontal line between luff and leech.

In his book, Don spends a lot of time discussing the difference between draft position and draft depth.

Dropping the traveler isn't going to affect sail shape... but the outhaul and mainsheet will.... as will the cunningham and halyard and perhaps the vang in certain situations. Batten tension can be used also, but rarely in a day sailing scenario.

So... don't waste time mixing apples and oranges here.... ask the guys here for masthead rig trimming tips and you'll get lots and lots of input. Look around for some older trim guides that were written in the seventies and eighties..... Don's guide is wonderful, but it helps to get other authors' perspectives. If you can find a copy of Tom Whidden's "The Art and Science of Sails" you will learn a lot about your generation of boat.
 
May 17, 2004
2,039
Other Catalina 30 Tucson, AZ
George: Joe and Stu have spelled it out for you. With the "telephone pole mast" obviously you can't BEND it -- you can only RAKE it and that presents a few problems if you rake too far because the boat thinks you picked up the mast and moved it aft and weatherhelm is the result.

For mates with a bendy mast, here's what's happening. Point your index finger straight. Now bend it. See where you knuckle is -- what you've done is pull the fullness out of the middle of the sail thus flatening and de-powering it.

My book, The Sail Trim Users Guide, is like the material you first use in ground school on your way to becoming a pilot -- it doesn't make you a pilot or a expert sailor. It's designed for beginners and provides you with a solid foundation to build on. If you don't have a solid understanding of draft depth, draft position, twist and angle of attack sail trim will never make any sense to you. Next you need to know which sail trim controls for the main and jib are used to adjust those four elements and how each control works. After that, you need to know the settings for each sail trim control for each point of wind and point of sail. That's as far as I can take you. After that, you need guys like Joe, RichH, Stu J and other on this forum to "fine tune" your knowledge and take you to the next level. Without my stuff, you wouldn't know what they were talking about.

My book is designed differently that most books on sail trim -- every item has its own section. Other books have stuff all over the place -- check their index to see what I mean. Draft depth or the traveler is on pages 5, 28, 51 and 222 plus there's stuff about fibreglass and sail construction all of which I could care less about. I don't want to build the boat, I just want to know how to sail it!!

Unfortunately, when I was learning to sail the SAIL TRIM FORUM didn't exist. I wish it had as it would have save me a lot of learning frustration. You get more straight scoop on sail trim here than anywhere I know. In fact, there is nothing like it on the web and that's thanks to Bly & Phil at sailboatowners.com. Ask yourself what has West Marine or BoatsUS done for you lately?? As a way to thank Phil & Bly, please remember them when you're XMAS shopping for your Xmas boat stuff.
 
Aug 4, 2009
204
Oday 25 Olympia
George, with a masthead rig, especially one with a stiff mast, the outhaul is the primary DRAFT DEPTHcontrol.... a loose foot mainsail will allow you to easily see the changes made in the lower third of the sail. The halyard and Cunningham will control DRAFT POSITION
it does not necessarily make the sail flatter... but rather positions the deepest point of the draft
along the horizontal line between luff and leech.

In his book, Don spends a lot of time discussing the difference between draft position and draft depth.

Dropping the traveler isn't going to affect sail shape... but the outhaul and mainsheet will.... as will the cunningham and halyard and perhaps the vang in certain situations. Batten tension can be used also, but rarely in a day sailing scenario.

So... don't waste time mixing apples and oranges here.... ask the guys here for masthead rig trimming tips and you'll get lots and lots of input. Look around for some older trim guides that were written in the seventies and eighties..... Don's guide is wonderful, but it helps to get other authors' perspectives. If you can find a copy of Tom Whidden's "The Art and Science of Sails" you will learn a lot about your generation of boat.
Thanks Joe, you and Stu have been most helpful.
George
 
Aug 4, 2009
204
Oday 25 Olympia
Don: Thanks for your reply. It's most appreciated. An engineering background helps me understand the sail trim control theory. My difficulty is that in the upper part of the main, the effect of the various trim controls seem much less than expected. Perhaps the full upper battens have an attenuating effect or I just can't detect the change. I'll try adding a draft stripe and see if that helps.
Thanks again, George
 
May 17, 2004
2,039
Other Catalina 30 Tucson, AZ
This afternoon, I'm in the process of smoking a test turkey in preparation for the "real deal" (it's tougher cooking for guests than competition BBQ) on Thanksgiving on a professional smoker (www.langbbqsmokers.com) but I always have time for a phone sail trim question, especially from a AZ sailor. He wanted me to clarify what I ment concerning understanding "sail trim terminology". I referred him to the topic and the terms Joe from San Diego and Stu used. I asked if he know what a cunningham was, which he didn't and it was down hill from there. What element does the traveler adjust -- it's angle of attack. Explain the difference between draft position and draft depth -- if you can't, you have no idea what Joe and Stu are talking about.

All ends well -- his check, he claims, for my book and chart will be in the mail tomorrow. He sounded like a nice lad so we'll see!!
 
Aug 4, 2009
204
Oday 25 Olympia
This afternoon, I'm in the process of smoking a test turkey in preparation for the "real deal" (it's tougher cooking for guests than competition BBQ) on Thanksgiving on a professional smoker (www.langbbqsmokers.com) but I always have time for a phone sail trim question, especially from a AZ sailor. He wanted me to clarify what I ment concerning understanding "sail trim terminology". I referred him to the topic and the terms Joe from San Diego and Stu used. I asked if he know what a cunningham was, which he didn't and it was down hill from there. What element does the traveler adjust -- it's angle of attack. Explain the difference between draft position and draft depth -- if you can't, you have no idea what Joe and Stu are talking about.

All ends well -- his check, he claims, for my book and chart will be in the mail tomorrow. He sounded like a nice lad so we'll see!!
Don: Be sure to save and boil the carcass to make the best soup/gravy broth ever! The smoked bird makes it even better.
George
 
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