loose footed mainsail is it safe?or to much stress at one point?

trouville

trouville

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I helped a friend to move a boat from Vada to Via Reggio.

The boat was an old heavy fisher.It dident have any sails but we had an old sail with a tear we cut off the first reef the glued and sewed the foot with a powerful "elna" sewing machine that has had a toothed drive belt fitted.

For the sheet we took an old bronze claw bent on the sails and were ready we set off winding through the shallows on a dead carm morning the winter sun bright we set the main as a stay sail.

As the morning progressed the breeze picked up we set the jib and mororsailed by lunch we dident realy need the engin as we were in plenty of time, by now there was a big swell running as it dose on this shore, crashing into the white cliffs(honesty its not dover)

We went on, watching the swell whoosh under us on the beam the old girl makeing a slow twist as it past we were close hauled manageing about 4 knots on the GPS.As the swell increesed we notived the boom flexing!!i lashed a line around the center of the boom and secuered it almost before id done that the boom broke and the lashing took the strain

We stated the engin lashed the the main to the rest of the boom and went on (we needed a stay sail) we arrived safly in good weather without further breakages

Dose this meen a loose footed main puts huge compression stresses on the boom?Ive only seen one yacht (not dingy) with a loose footed main and that came from the USA

How should loose footed mains be set up?Where are the stress points? Are they different to a self tacking jib? (with a small boom to sweep the crew off the foredeck!!)I havent used one of those either.

Advice on loose footed mains please!! /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif
 
stress will depend upon how much you have put into the kicking strap/vang, and where the main sheets are attached. With a loose footed main, IMHO it is essental that the main sheets attach the the back of the boom, where the loose footed sail also attaches.
 
Thats where it was! and we dident have a kicking strap.

What im getting at slowly is my real question! That US boat had fitter a roller reefing system as his main sail system!To reef he just rolled it in,he said he had never had a problem and she sailed as well as with the old main.

The boom had a slide and the sheets were attached to the end of the boom and fixed therefor the sail could be attached to any point up to the mast with changeing stresses!

As out boom "bowed" i took that as compression stress??
 
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That US boat had fitter a roller reefing system as his main sail system!To reef he just rolled it in,he said he had never had a problem and she sailed as well as with the old main.



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well i suspect he's exadurating there, unless his old main was of a very poor quality.

Loose footed mains are now very common on this side of the pond as well, and for good reason. They are much more adjustable and allow for a more powerful shape in light winds. As to the load points I don't think it will actually vary too much. If you feel the foot of a "captive" main you will see that there is really very little force at all holding the main to the boom, the vast majority of the force will still go through the reinforced eye at the clew.
When you have the position of the clew on the boom changing significantly (as in roller reefing) then a heavier section will be required to support the force as it's now effectively on a lever from the sheet.
 
Your description is identical to the set-up on my boat. I do watch the kicking strap tension very carefully when down wind, as it can impose a lot of strain on the boom. Sounds like your boom was never designed for the strains imposed in real sailing!
 
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Your description is identical to the set-up on my boat. I do watch the kicking strap tension very carefully when down wind, as it can impose a lot of strain on the boom. Sounds like your boom was never designed for the strains imposed in real sailing!

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Hi Talbot,

I am about to use a Loose Footed Main for the first time. I am sorry if this sounds like a daft question, but do you haul your kicking strap tighter down wind, than you would with a foot in boom jobbie?
 
When you put a slab reef in a main you then have a loose footed main. I dont believe the slides or the foot groove on a conventional main contribute greatly to spreading the load. I think the fault was in the boom!
 
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I am about to use a Loose Footed Main for the first time. I am sorry if this sounds like a daft question, but do you haul your kicking strap tighter down wind, than you would with a foot in boom jobbie?

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No, the reverse, cause my boom is old and thus, I tend to tighten until I have tension, but minimal bend.

I also found it essential with in-mast reefing, to have the kicking strap adjustable from the cockpit.

These days there are only 4 reasons to go foward of the cockpit:

Drop the anchor
prepare/recover the fenders for alongside
Set the spinnaker
make use of the acres of space for sunbathing /forums/images/graemlins/laugh.gif
 
Yes I had already decided that my kicking strap will be better adjusted from the cockpit. I am still working on the rest of the layout. thanks for the info.
 
When I purchased the behind mast system, I was assured that I would be able to control the in and outhaul by hand. I was very dubious, and decided that I would demount the little winch from the mast which used to be used for slab reefing, and mount it for use with the in and outhaul. Good decision - not to powerful to damage the sail, but great to allow tweaking.
 
The boom was old had never been looked after at least not for a while the wood was cracked and bear.Even so there was perhaps an inch of deformation as it bowed!Hence my lashing!I was amazed it held up for so long!It took me at least 60 seconds to get a line and tie it on.

Do modern loose footed mains still have a boom?Or is that an option? Whats the benifit when close hauled in a strong breeze over a main with slides or rope bolt foot fixed in boom??

I still have another question!!but one by one-
 
Surely even with a bolt rope the stress on the boom is only taken in two places, where the main sheet and kicking strap are fixed.
The difference with a loose footed main is that there is only one stress point for the sail rather than distributed along the entire foot.
 
There will be many different interpretations of advantages/disadvantages.

For me, it enables me to get better sail shape in lighter conditions (especially with full vertical battens)
 
Can you use your existing mainsail?Or must it be recut? Assuming its not recut when you roll it in haw dose the sail perform?

To reef do you just roll in untill you feel you have the right amount of sail for the conitions?

In theroy then i could do what the American did and put my main on a roller reefing and mount it on the mast?
 
IMHO vital that you have a new sail. old baggy, badly shaped is much more likely to jam.

I use the vertical battens as my reefing points, that makes it easier to get consistent balance with genoa.
 
Obviously you still have to have a boom else what are you going to use to get the outhaul out there? /forums/images/graemlins/confused.gif

As said in other posts, when one looks at a main that has a foot bolt rope, generally even under full power there is little tension on the boom anywhere along the sail and it only really comes on at the end of the boom.

My take on the pressures is:

The outhaul places compressive stress inwards towards the mast.

The kicker or any other vang will introduce a bend moment into the game.

The main sheet, even if on the end of the boom, will place pressure of some sort on the boom and if the mainsheet runs inwards towards the mast, that is, if the traveller is forward of the end of the boom, the compressive stress exerted by the outhaul will be exacerbated.

If the bend moment introduced by the kicker, vang, whatever, reaches "critical mass" and bends the boom past a point where it retains compressive strength, the pressure on the outhaul will cause it to uncontrollably bend and it will break.

To see the practical effect of this, take a 4-inch piece of drinking straw and press the ends together between your thumb and middle finger. If you keep the straw straight it'll take considerable pressure. Now press another finger sideways against the middle of the straw and it will quickly and catastrophically bend at that point.

I hope this all makes sense. And to summarise, the loose footed main I don't believe has any different effects on the ability of the boom to resist breaking. Better believe that if the was a risk of that, America's Cup syndicates wouldn't be using them.
 
I find it rather amazing all this discussions on loose footed mains. They really are very little different from a captive foot. I transitioned from captive to loose some years back without a second thought.

On a captive main the slides etc hold the foot close to the boom even when there is a lot of camber and so theoretically can reduce air flow over the bottom. ie the boom is like a winged keel. However this effect is really to be ignored especially as when the wind comes up you haul on the outhaul and the foot aligns with the boom.
So on both types of main the load is taken at the clew and tack. (just like a slab reefed main should be) ie attachments in the middle are neither here nor there.

Now there is such a mainsail as one without a boom. It may also be called loose footed but is vastly different. It uses a mainsheet which is attached well aft in the boat and the angle from the attachment to the clew is critical to get the correct amount of pull in toward the middle of the boat and pul aft (and down) to get the whole sail working. It is in fact just like setting a genoa sheeting point and in exactly the same way it can be set pretty well for windward work but off the wind as the sheet is loosened that sail goes dreadfully shaped.(unless the sheeting point can be moved) The advantages are no boom. It is a method often used for storm trisails.

So a jib on a boom has the same advantages as a mainsail on a boom in that you can adjust the sail shape both close hauled and off the wind and it can be self tacking. The disadvantage is that the foot must be short to fit entirely in the fore triangle. ie no overlap. That is the main reason we don't see them. Often seen on cutter rig for the inner jib.

As for breaking the boom. Clearly it was not up to the job and I don't think your modifications to the mainsail making it loose footed had any bearing on the failure. Yes a sheeting point at the aft end of the boom should give less stress to the boom leaving, as you identified only end compression which can be a lot if the boom has a bend induced by a vang or kicker. Perhaps under the conditions you should have had a deeper reef.

Lets not have this talk of roller reefing (around the boom) that is just an abomination unto a sailor. You can't get the outhaul tension you need for a good sail shape and the boom is likely to droop as the varying thickness of sail in the roll determines the depth of reef and is different front to back. olewill
 
Good point?

which has to be answered by a question: "Where is the main sheet attachment to the boom".

In fact it's the bending, not the compression, force which causes the problem.

If the mainsheet attachment is at the end of the boom, a loose footed main probably is exerting less eccentric load than a bolt-rope main.

However if it's in the centre the load is exaggerated and the boom section needs to be a lot deeper.

Nearly all in-mast furlers have, IMHO, totally inadequate sections for their booms, but that can be countered by the observation that the load centre moves closer to the boom as you reef.

My impression is that, fortunately, the owners of boats fitted with in-mast furling tend to avoid heavy weather.
 
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