type of main sail question

Sep 16, 2007
48
Hunter 23.5 lighthouse landing
My wife and I managed to blow our mast during a race last fall on our H23-5. A 42 kt gust got us on a down wind run. We're getting things back together this winter. I need to replace the main sail. Does anyone here use a loose foot main? Several of the boats I sail with have them and l'm wondering about the advantages / disadvantages. ...

Psychotic Squirrel
KY Lake....
 
Aug 22, 2011
1,106
MacGregor Venture V224 Cheeseland
I'm pretty certain there is quite a bit of prior discussion on this subject on these forums.

I suggest trying the search function and read up and then ask more specifically.

BTW: Our next main will be a loose foot.
 
Dec 8, 2011
172
Hunter 23.5 New Orleans
I'll bet Tim C was really cooking before he lost the mast!

Kind regards

Hugh
 
Sep 16, 2007
48
Hunter 23.5 lighthouse landing
Yup "flyin with the barn door wide open" was one of the best descriptions I heard. 8.9 kts and accelerating was on the GPS a few seconds before failure. Thirteen boats went out that morning only 6 finished race. A Flyin Scott and a Mengles (sp?) finished and both flew spinakers! ?!?!?!!!! The other boats were 30+ footers one of which put his spreaders in the drink In the same gust that got us. It was a spicy race for this inland lake sailor.
 
Apr 27, 2010
1,157
Hunter 23 Lake Wallenpaupack
I would guess the Flying Scot and Melges are both planing hulls, so maybe their ability to accelerate in gusts may have helped them. I bet they were trucking. I used to have a Thistle, designed by the same guy who did the Scot, and it really moved. I wonder if a Hunter 23.5 could on occasion plane?
 
Dec 8, 2011
172
Hunter 23.5 New Orleans
I'm pretty sure my 23.5 was planing when I was reading 7+kts on my GPS. Happily, I didn't lose my stick.

Kind regards

Hugh
 
Aug 5, 2009
333
Hunter h23 Dallas Tx.
I purchased a loose footed main and love it. Pics of it in my profile
 

Sprega

.
Sep 12, 2012
115
O,day 27 Brownsville Marina
I just purchesed a new loose footed main for my O'27. I love it. Soooo much easier to adjust the out haul. The sail was made by Hyde and I bought it through Judy B Sail. All in all, a very satisfying expearance.
 

Attachments

Oct 3, 2006
999
Hunter 23 Philadelphia
I would expect a loose footed main to have at least one slug in the boom.
But more importantly, it's cut to fly this way. Nothing is stopping you from flying a bolt-rope foot loose, but the sail wasn't designed to carry the load in a "radial" fashion to the three corners and it will get old and baggy prematurely.
 

Clark

.
Jun 30, 2004
880
Hunter 280 Lake Guntersville, AL
My wife and I managed to blow our mast during a race last fall on our H23-5. A 42 kt gust got us on a down wind run. We're getting things back together this winter. I need to replace the main sail. Does anyone here use a loose foot main? Several of the boats I sail with have them and l'm wondering about the advantages / disadvantages. ...

Psychotic Squirrel
KY Lake....
I have two boats with loose-footed mains. I really like them because you can easily adjust the draft depth for wind speeds (light air vs heavy) or point-of-sail (beat vs run).
 
Sep 16, 2007
48
Hunter 23.5 lighthouse landing
Thank for the responses. Iv'e been working with north sails on replacement of my damaged sails. after sending the measurements of the main I was told they were off. Checked the measurement between marks on the mast and found out the main I was using was smaller than the design called for. Previous owner changed out more than I knew...
 
Jun 5, 2010
1,067
Hunter 25 Burlington NJ
Drawback of loose-footed mainsails

The big drawback to a loose-footed mainsail is the point-loading of the ends of the boom. The sail slugs (that so many people think are 'slow' or 'drag' or 'old-school') actually preserve both the boom and the sail by spreading the load of the sail's pull along the boom's whole length. (The Tides Marine track system is an even better solution than sail slides, much like the Schaefer Tuff Luff is for non-furling headsails.) Likewise the sail slugs along the hoist do the same for the main.

This is why, in really gnarly weather, you are better off with a mainsail (albeit deeply reefed) than a headsail, even one on a furler, in terms of preserving your rig. Headsails, being attached only at points (the head, the clew, the tack), point-load the spar. This puts a heck of a lot of strain on the shrouds (especially the lowers) and all the rigging-attachment points.

Believe it or not, aluminum spars are not meant to be under bending loads-- this is very bad for any aluminum extrusion. They are best in compression-- all the load transferred from top to bottom, in column (same as carbon-fiber ones), which is what sailboat spars are supposed to be designed to do. Improperly point-loaded, the middle of the spar will want to oscillate (bend sideways), which is a recipe for spar failure. Again, the sail slugs by comparison distribute the pull along the length of the sail, so the load at each point is less along the mast or boom and all those points work together.

A loose-footed mainsail is especially bad when you have mid-boom sheeting. The sheet at the midpoint of the boom is a load pulling down while the ends are trying to pull up, imposing a MAJOR bending moment on the poor boom. I have observed some late-model Beneteaus as the dealer next door with mid-boom sheeting located less than 50% aft from the mast and then a hydraulic vang forward of that. What is the point of the vang? --and what happens to the end of the boom? But this is the value some buyers place on the Bimini top! (Never thought I'd say it but this is one reason I favor 'radar arches' --best place for the traveler.)

Selden Spars have lately introduced a series of boom extrusions (which Beneteau and other mid-boom-sheeting boats are no doubt using) with a flat longitudinal blade inside the section to keep the boom from bending laterally (sideways) and thus to keep the tail end of the boom from falling off to leeward (or breaking. It can happen). The Selden design does not, however, minimize vertical (upward) bending as effectively. So, still, it's a problem with mid-boom sheeting.

Purely by design, the sheetline should always be led vertically downwards from the aftmost end of the boom, directly under the outhaul sheave or pin. When this is not practical, then it should be fitted as far aft towards those places as possible-- not forward. Let the vang do the work for the middle of the boom.

I know what many owners will say: 'The boat was designed like that; the designer is a professional; why should I listen to a loudmouth on Sailboat Owners?' I am a professional; and that designer was more likely tasked with making
dealers and advertising clients happy rather than with designing, engineering and building the world's most beautiful seaworthy sailing yachts as I have been since I was a teenager. And I would very strongly NOT recommend a loose-footed mainsail if you have mid-boom sheeting-- especially without major reengineering of the whole rig, unless you are prepared to replace the (older) boom when (not if) it fails.

Actually you would be better off flying the mainsail loose-footed without a boom at all-- though you would definitely be imposing major loads on the spinnaker turning blocks if that's where you'd be sheeting it. (I have long wanted to try this myself!)
 
Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
No disadvantages to the loose footed sail.

I respectfully disagree with any analysis that says switching from footed to loose-footed sails is highly likely to cause a boom to buckle (all other things being equal).

The forces on the boom aren't significantly different whether the sail is loose footed or not.

If a boom is strong enough to be used with a footed sail, it's strong enough for a loose footed sail. If it's strong enough for mid-boom sheeting with a footed sail, it will be strong enough for mid-boom sheeting with a loose footed sail.

(Please note that I did not claim that it is safe to change a boom from end-boom sheeting to mid-boom sheeting)

Image 1 Below: Orientation of the load bearing paths on a membrane mainsail:




First, the majority of the loading in a mainsail is from the clew to the head along the leach. That doesn't change whether the sail is loose footed or not.

Secondly, regarding the loads along the foot of a mainsail: the load path near the foot goes from the clew horizontally to the tack. There is virtually no vertical load on the sailcloth in the middle of the foot of the sail. The load at the very edge of the foot is 99% horizontal. To put it another way, any sailcloth in the foot which is attached to the middle of the boom is just going along for the ride in terms of vertical loads.

To make my point anecdotally : I'd like to point out that "more expensive" footed sails used to have a baggy foot shelf that is made made from very light cloth, sometimes even from nylon. People did it all the time and nobody every attributed failure of the boom to a shelf. Booms fail for lots of reasons, but not because a racer added a foot shelf to it.

When we design a membrane sail, we align the load bearing fibers in arcs pointing at the three corners, which means the fibers are horizontal at the foot. In like manner, when we design a tri-radial panelled sail, we align the panels with the load bearing fibers pointing at the three corners of the sail; the load bearing fibers are predominantly oriented horizonally at the edge of the foot.

Judy B
Hyde Sails Direct
www.HydeSailsDirect.com

Image 2: A membrane sail, showing the load bearing fibers (below)



Image 3: A tri-radial sail, showing the alignment of the panels to the load paths. The alignment of warp fibers is parallel to the loads in the sail and this is why tri-radial sails have more stable shapes than cross cut sails and also why they respond more predictably to subtle trim adjustments than crosscut sails.




Image 5: This video shows an overview of the computational finite element analysis and load modelling for the fiber layout of a membrane sail, compressed into about 60 seconds!!

 
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Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
I respectfully disagree with any analysis that says switching from footed to loose-footed sails highly likely to cause a boom to buckle (all other things being equal).

The forces on the boom aren't significantly different whether the sail is loose footed or not.
Absolutely , totally, 100% correct.

The loads are at the corners. Always have been.
 
Jan 25, 2015
9
Hunter H 26 San Diego
My last two boats have loose footed mains (Mac 25 and Hunter 26). I like how much easer it is to adjust the pocket to the changing wind conditions. I haven't had any problems with the boom. I got my latest sails from Judy B Sails and couldn't be happier.
 
Jun 8, 2004
8,881
-na -NA Anywhere USA
One issue is the boom itself. There are some booms not designed for a foot loose mainsail which can be disastourous. If the booms are strong enough for example on the Hunters, should not be a problem....
 
Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
One issue is the boom itself. There are some booms not designed for a foot loose mainsail which can be disastourous. ....
This simply isn't true. If you are counting on the sailcloth to keep your boom from buckling, the physics simply don't work that way. Booms break for lots of reasons, but loose footed sails aren't one of them. Read the top part of this thread for a discussion of the forces on the sail cloth.

Judy B,
Sailmaker
 
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