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Old 09-12-2011, 15:44   #31
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Re: Loose-Footed Main

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Originally Posted by Vasco View Post
How are they easier to reef? I don't see any difference from a sail with a boltrope on the foot unless you do not have reefing lines and lash a line through a cringle and around the boom.
You don't have to tie the reef lines around the boom. Better sail shape when reefed. Michael..
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Old 09-12-2011, 18:09   #32
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Re: Loose-Footed Main

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You don't have to tie the reef lines around the boom. Better sail shape when reefed. Michael..
Ditto! Which also helps to keep the eyelets from getting stressed. One can bunch up the sail foot fairly tight, creating a better air path w/o the sloppiness of puffs hanging out.
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Old 09-12-2011, 18:20   #33
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Originally Posted by jzk

They have little cords to deal with this both for the foot and the leech.
I thought about "footlines" but so far I haven't seen one on a loose foot main.

I am lucky that I get to sail other peoples boats a lot. It is valuable to compare what other guys do. I pick up ideas and tips all the time. Here are some observations I make to evaluate how "serious" the sailing is gonna be. Here are signs it won't be serious and I have seen them all and you probably have to.

Leech lines - secured really tightly in the jammer with a combination of square knots and hitches with the leech closed 15 degrees
Outhaul - foot stretched like a rubber band, outhaul tied off like the leech lines
Genny cars - move them and there is a sun stain/surface corrosion mark indicating the cars have never moved, the cars are on different holes port & starboard. Inboard track never used, in fact it doesn't even have cars on it.
Boom vang - always on full!

When the main is raised.

- there is a boom bag attached to the jacklines, but the jacklines are never slacked and the bag never stowed because its too much work.
- the topping lift is never slacked - this one I could not believe!
- the traveler is centered and never touched. I very gently asked a skipper about this and he said, "You center the traveller for close hauled pointing." I said, "don't you mean boom?". He looked at me quizically so I went downstairs and got a couple of beers.

I have also been on boats where the anchors, chain, cockpit benches and liferaft are removed for beer can races... Now that's a PITA!
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Old 09-12-2011, 18:33   #34
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Quote:
Originally Posted by delmarrey
I have a 443 sq. ft. loose footed main and love it. it's easy to shape and remove if need be (storms). But one drawback is the set up of the boom. If its sheets are at the end of the boom, it works best BUT if the boom is sheeted in a single spot in center with a loose foot, one has to worry about boom bending and/or braking.

For center sheeting with a loose foot, it's better to have a three point attachment system spread out over the middle 1/4 to 1/3 of the booms center, similar to this picture.
Hi Del - I always appreciate your experience and thoughts. Someone posted this earlier in the thread and as I do I started obsessing about it.

First - distributed sheeting for highly stressed booms = good idea. And if the boat has it I wouldn't change it.

However I can't visualize the "change" in boom loading when the sail foot is altered. Ulitmately the boom is pinned at the gooseneck and sheeting point. Lets stick with end boom sheeting for now. As the sheet is hauled force perpinducular to the lift is applied and carried through tack and clew, to gooseneck and sheeting point, forgetting about downhaul loading for now as well.

I can see mid-boom bending moment but I can't see the bending moment changing based on foot design. I can see point loading on the sail tack and clew being higher, meaning a loose footed sail must be designed for these loads, vs distributed loading along the foot for a captive foot.

Certainly there have been lively discussions about changing the boom sheeting point but that's not what we are talking about here.

Anyway nothing I have read about switching to loose foot talks about changing the boom or sheeting system.

What are your thoughts?
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Old 09-12-2011, 19:04   #35
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Re: Loose-Footed Main

I do have a foot line on mine up by the tack. If the sail is on a down wind run I can tighten the line and give it a bit of a belly, and then go totally slack for a close haul. Then tighten up the clew/outhaul. My sail foot has a bit of a foot-roach to create that belly. When not in use it looks like the sail is mis-cut a bit. You can see it a little in the picture. If I really tighten up on the clew it makes a wrinkle at the foot between the clew and tack.

As for the boom, when a sail has a foot-rope or slides in a boom, with the out haul tight, the sail helps supports the center of the boom. But when the boom is only supported on the ends with the traveller in the center of the boom, the boom is like a bow for shooting arrows.
If you were to get a heavy gust the sail balloons out pulling the ends inward, while the traveller is pulling back trying to stop the boom, causing the boom to bow at the traveller.

With a three point contact it distributes the pull-back over a larger area avoiding a single point shock. Like an accidental jibe hitting the shrouds, if you've ever seen that. You swear the boom is going to brake in half.
Hope that helps explain.
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Old 09-12-2011, 21:45   #36
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Re: Loose-Footed Main

No one seems to have mentioned one additional plus for a loose foot. Besides all the other ones, a loose foot should cost a good bit less than a "standard" foot. We switched about 8 years ago.
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Old 09-12-2011, 22:15   #37
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Re: Loose-Footed Main

I found a picture of the foot cunningham, if interested. The red line in the center left of the picture.

.
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Old 09-12-2011, 22:29   #38
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Not sure I agree with the boom load concerns. In theory it is correct that the bending moment would be higher. However, remember that every boom its designed for loads.from a reefed sail. Every reefed sail is loose footed.
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Old 09-12-2011, 23:04   #39
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Re: Loose-Footed Main

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Originally Posted by cwyckham View Post
Not sure I agree with the boom load concerns. In theory it is correct that the bending moment would be higher. However, remember that every boom its designed for loads.from a reefed sail. Every reefed sail is loose footed.
And less sail area w/more of it towards the mast.
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Old 09-12-2011, 23:43   #40
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Quote:
Originally Posted by delmarrey

And less sail area w/more of it towards the mast.
The whole reason you reef is the high forces. You can get just as high forces with a reef as without depending on wind.

First reef Cringle is about 6" closer to the mast on my main. Hardly going to make a difference.
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Old 10-12-2011, 05:32   #41
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When your sheet is attached halfway the boom and you reef, you move the clew towards the sheet attachment. This reduces stresses in the boom. Also, the boom vang plays a role. There are enough factors inolved that even engineers have trouble calculating required strength. Look at racers braking booms, followed by installing stronger booms. This is because they want to save weight and thus not over engineer it like on cruising designs, but they fail to make correct calculations and end up doing trial and error.

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Old 10-12-2011, 05:59   #42
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Quote:
Originally Posted by s/v Jedi
When your sheet is attached halfway the boom and you reef, you move the clew towards the sheet attachment. This reduces stresses in the boom. Also, the boom vang plays a role. There are enough factors inolved that even engineers have trouble calculating required strength. Look at racers braking booms, followed by installing stronger booms. This is because they want to save weight and thus not over engineer it like on cruising designs, but they fail to make correct calculations and end up doing trial and error.

cheers,
Nick.
Im currently with cwyckham on this. But don't get me wrong. I would sell him out for a twinkie ;-)

Hypothetically lets have a loose foot main and sheeting 3/4 out the boom.

The boat is sailing at 7 knots. That requires X sail pressure. The main load is perpendicular to the lift, hopefully forward of the beam so the boat is going forward not backwards.

The mainsheet counteracts this load. It should be obvious that 75% of the load is forward of the sheet and 25% is aft.

Aft of the sheet the boom is trying to break off downwind. Forward of the sheet it is too. But it is restrained at the tack. The load should be centered between sheet and tack trying to fail the boom in the middle.

After reefing the boat is still observed to be going 7 knots. X must still equal X. Higher windspeed is the reason. Therefore the load on tack and clew must still be X.

After reefing lets say the clew is now adjacent to the mainsheet for our test case.

100% of X is now carried between sheet and clew. Boom load forward is actually higher! Boom load aft is less except outhaul load which is probably constant.

Comparing race boats with carbon fiber spars and huge rig loads and need for lightness is probably not useful for us.
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Old 10-12-2011, 06:46   #43
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The mainsheet counteracts this load. It should be obvious that 75% of the load is forward of the sheet and 25% is aft.
We're talking loose foot right? Then the clew is aft on the boom and the tack is on the gooseneck fitting, making the clew the only point where force is put onto the boom. This force is countered by three other attachments: gooseneck fitting, vang fitting and sheet attachment. The brunt is taken by the gooseneck fitting because most of the load is compression forces (the sail tries to collaps the boom). The sail also tries to lift the boom in it's 2nd dimension want of collapsing. This is countered by the vang and that is the point of failure I've most often seen with broken booms. If the boom isn't ridiculously thick-walled, you need a reinforcement sleeve inside the boom around the vang attachment... like 4' long, to spread the load, with tapered ends etc. now the last attachment, the sheet. this counteracts the force that wants to swing the boom outwards. The failure most often seen here is that the fitting is pulled off the boom. That is why a rope around the boom attachment is better. If there is a single attachment point and it is at 1/3th from the end of he boom, the last 1/3rd is unsupported. This is more a problem with the clew attachment than with the sheet, but an often used solution to deal with it is two-fold:

- put a section of track on top the aft end of the boom and attach the clew to a car that trvels on that track. The outhaul also attaches to the car. This reinforces the boom and it distributes the force from the clew over a section instead of a point, just like the sleeve insert does for the vang.

- spread sheet attachment over wider area. There are two methods: using multiple blocks like the diagram posted earlier, or a single block attached with multiple webbings around the boom, or even a net or piece of sailcloth around the boom. I have multiple webbings with an aluminium spreader-plate which is somewhat dated

So, it's much more complicated than just force forward and aft of sheet. It is also more about spreading the load, while preventing ripped-off attachment point by wrapping around the boom. Don't forget the leech reefing lines that can also wrap around he boom with loose foot.

I find the piece of track on the end of the boom the best way to go when changing to loose footed.

cheers,
Nick.
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Old 10-12-2011, 07:01   #44
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Re: Loose-Footed Main

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My next main will be loose footed. Better for trimming the sail. The only drawback I have reead about is a potential to get foot flutter.

The only advantages of the contained foot is if you wanna collect rain off the sail and on a run my boy used to take a nap on the boom. He'd fall out of a loose foot main...
The foot will only flutter if it is cut the way some of the old loose footed racing sails used to be. Unlikely on a cruiser these days. The foot of the main in post 37 will never flutter even without the string.
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Old 10-12-2011, 07:07   #45
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Re: Loose-Footed Main

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They have little cords to deal with this both for the foot and the leech.
Leech lines are important . . . . foot lines are not necessary.
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