Loosefoot main and vang

[Tony G]

Ebb,

Here it is. Fresh out of the box and in need of some grinding, filing and polishing. What else is there to do here all winter long?

[ebb]

Hey Tony, you forgot the weakest link!

[Tony G]

Boy do I feel stupid! Thanks for pointing that out Ebb. This is how it was supposed to be assembled as per the drawings.

[ebb]

still don't see no stinkun weakest link

[John]

I am a part time.....make that a sometime, racer so I look for correction on this from the experienced ones. My view of the the traveler and mainsheet are that main angle (to the wind) is controlled not with the sheet but with the traveler, when you are sailing to windward. Sail tension/flatness are set with the mainsheet. Except in light winds where you want some fullness in the main, or in really hard winds where you want to flatten the main beyond what you can do with a cunningham or the downhaul I have, you want almost no vang tension or lift. Only after the sheeting angle puts the boom outside of the traveler, do things change. At that point, sheeting angle is set with the main sheet, and sail set/tension is set with the vang.

I have a standard main, so the following is conjecture. The only real loss with a loose footed main is the ability to add tension under high wind conditions when sailing off the wind. This makes your outhaul and downhaul/controls all the more important. In light winds, you still can support the weight of the boom to keep fullness in the sail, and I believe that the use of traveler, sheet, and vang remain the same. Also if you try to flatten a loose footed main with the vang, as has been stated, it really puts a lot of force on the gooseneck and the boom itself. So that's my story

Happy Thanksgiving to all.

[Theis]

I'll add my two cents for whatever it they are worth. When I had my loose footed main built, I was told by the sailmaker - Quantum Sails in Texas - that the benefit of a loose footed sail is that it spills wind at the foot, and the foot keeps its wing shape at the foot. A loose footed sail therefore is faster. The non-loose footed sails were developed because of racing rules, I was told, which required that the foot be attached to the boom throughout its length. Those rules have now been changed. - That is why everyone today is going loose-footed (allegedly 95% according to the sailmaker).

In the non-loosefooted sails (which I used to have), the sails could not have a wing shape at the boom but had to be "tucked in" to conform with the straight line of the boom. In other words, the wing shape had to be terminated above the foot in favor of a straight line. That meant the shape of the sail was lost approaching the foot. Pulling the foot tight with a vang in such a case would wreck the sail shape further up the sail, in addition to bending the boom. The outhaul and downhaul/cunningham and the sheet/traveler are the only running rigging adjustments to the foot and luff.

The vang/preventer should not used for sail shape, other than in a down wind run to keep the boom/outhaul from lifting when the sheet/traveler can be of no help, and decreasing the effective sail area. And to help prevent a flying jibe.

[ebb]

MORE
M O R E
M O R E !

[Theis]

As for me, I only offered two cents worth as I mentioned. The next bit of wisdom, or lack thereof, goes up exponentially. I can afford a two cent investment, but I don't have $500 cash investment (the next increment for an additional pearl of wisdom) on the table at this moment.

Hope you had a good Thanksgiving dreaming of the blue waters, the warm days, and the fresh winds.

[John]

Ok...I don't know if this is worth $500 but here goes.


The shape issue has been solved with out being loose (if you will excuse the expression)...Here is an example on something just slightly larger than our beloved A/C's.

http://www.offshorespars.com/websitenews_aug04.pdf

The Park Ave Boom terminates the foil fairly well. There have also been sails built with a zipper foot, allowing the draft to be carried way down towards in the sail. There are also terminated foil sections on keels with these keel plates/wings. So that solution has also been examined.

If you have draft stripes or ribbons on your main, then you use either the sheet on the wind or the vang off the wind to adjust sail twist just to the point when the flow almost stalls. Generally this will align your top batten with the boom. I don't see how you have this control off the wind with a loose footed main. But I have no experience with a loose footed main.

[ebb]

John,
At the bottom of the page of giants there is a Hoek 75 ketch. Maybe there is enough suggestion of a shadow in the main to think the sail maker built in chord shape down to the boom. You can almost see the shape of a shadow just above the boom as you scroll up past the 125 footer. They are dramatically photgraphed on a flatout reach with the sails in as hard and tight as the wings on a jet. These sails seem to have full chord clear to the boom without flattening and without a filler piece on the bottom of the sail. Can't see, have to assume that.

You are pointing out, aren't you, that sail shape clear to the boom can be acheived by the sail maker. For this point of sail anyhow. Of course with the boom out and the sail more full you would loose it where the sail flattens to the boom. I have no idea. On these points of sail does the foil matter as much as when beating to windward?

It seems to me you are therefor saying a rigid vang is more useful to a slug footed main in arranging the shape you want in windy conditions or in a larger variety of conditions? Your first salvo is beyond my tech condition. I have sailed but I'm sadly not an experienced sailor, but I do want the remodeled rig planned for 338 to teach me the good things. In other words, traditional sail control, boom and line control, safety are prime concerns. Need to make correct decisions in fog of ignorance.

Just from the amatuer standpoint now, the sail connected to the boom along the foot provides support for the boom and advantages in dialing in the best sail shape for the conditions and point of sail. I've just read that 95% of all mains built now are loose foot.
(I'm romantically inclined to them also as I had a gaff rigged cutter with a loose foot main that was cut with an obvious chord below the boom. Why not? A roach on the loose foot of the main.)
Designers create fashion. Is that what we have here? Is the loosefoot main a 'what goes around comes around' kind of thing? Big time racers have kept the boom attached across the foot. They are into big time control.

I wondering if the attached foot (with the Garhauer) is the way to go for a cruising 338? All unreasonable opinions from seasoned skippers greatly admired.

[Theis]

This is a one dollar addition. There are ways to SORT OF get around this problem, like the zipper foot. When you have a much larger boom, or a boom where there are other large forces, the sail may be necessary for structural reasons.

One of the reasons for the loose footed main is to spill the wind under the sail. You don't want backpressure at the foot for ultimate performance, and spilling the wind underneath, as I understand the theory, is one way of doing that. A zipper sail does not do that.

But there is a reason for a sail being in a slot or track, particularly for much larger vessels. With a loose footed main, there is a tremendous compressive force on the boom, without any support to keep the boom from bending. With a much larger boat, this compressive force could be very significant, particularly if there are mid-boom mounted bending elements. (I was originally concerned about this with the Ariel, but have not encountered noticeable problems). The boom is in unsupported compression between the outhaul and the gooseneck. If the boom remains straight, then there is no problem. It can withstand the compression. But if something, such as a vang or a mid boom mounted traveler, puts a modest bend in the boom, that compression, once the bowing of the boom has started, will bow the boom further. There is no sail to put a limit on an ever increasing bowing of the boom until ....... Stay tuned for what happens when a boom exceeds its structural bending limit but hints would include the words "buckle", "replace" "serious problem" and "Oh _ _ _ _ !"

[John]

Ebb,

Exactly....This is not from direct experience but talking to racers (somewhat casually) and from what I read. The sailmakers now have the capability to build a sail with the foil that they or the owner wants. The really high end racing sails are molded laminate structures. Once they are mounted, the job is to keep them adjusted so that the air flow over the foil is maintained. Shape has already been built in. Part of the job is to set the controls so the built in shape is present, and in many caes you can mark controls to maintain the set. An all out racing boat has controls and tweaks way beyond what what we have on our boats. They say on any point of sail, short of dead down wind, the sheet tenders job is to find and maintain that angle to the wind (apparent nt true) that does the job. They also have instrumentation on the sail and mast to tell them where they are. And they are watching the speed increases or decreases, not absolute speed.

I am not for or against loose footed mains. If fact, the other foil is generally loose footed (the jib). Sail twist in the jib is generally maintained by vertical sheeting angle. That is why we have those long runs of jenny track on our decks. But think of the forces we apply to the clew of the jib to shape it.
The same forces are now needed to shape the main if it is loose footed. So instead of a vang ( and you will still need one to prevent boom lift off the wind) you will need an adjustable car and very good/strong outhaul control to do the shaping for you.

I can be convinced that a loose footed main can carry shape lower in the sail than modifications to the boom or strange shelf construction in the sail itself. The price is added complexity in sail control. I don't believe that having a loose footed main changes the way to think about sail controls as I described in my first submission. And that is, that sheet on the wind, and the vang or clew control off the wind, control shape. On the wind sail position is a function of the traveler and off the wind it is a function of the sheet. So you put the boom where you want it and then dial in sail shape. Not that there is not interaction between the controls, but we are driving a boat, not a train.

BTW, I couln't find a picture, but the first Park Ave Boom on the J Boat Enterprise, was about 4 ft wide. The main was set on a series of tracks perpendicular to the boom. Think about adjusting those.

[John]

Talk about cross posting....It's a shame we can't see each other Theis, with a mug of coffee, comtemplating all this on a nice clear day with great boat underneath us.

Wallace Ross,the author of Sail Power, and Doyle the sailmaker both advocate for the vang as a shape controller. I do wholeheartedly agree with your point that loose footed mains may require re-engineering of the boom section and gooseneck, for all the reasons you stated so well.

The mid-boom traveler, was an accomodation to people who were tired of tripping over the traveler. And it also has made it less effective. Most of the controls we have been discussing are best applied at the clew.

Hope you had a great Thanksgiving. At least here in Massachusetts we had a one day repreive but it is again 35 deg out side.

[Ed Ekers]

I would like to offer just a couple of thoughts to the whole picture. I guess my first thought is somewhat directed to capn.ebb. Are the questions you raise about a the need for a vang or are your comments more to the point of a rigid vang. My opinion is a boat rigged with a vang is able to adjust to different conditions a little easier. Does not matter if it is rigid or soft. Just one more tool at your disposal.

In terms of performance sailing, if this is your game, my opinion is the more you learn about sail trim the better your results will be. With that said I think the vang methods described by others is what most of us would admit to. If you spend a lot of time on many different racing yachts you will find a host of ways to trim sails and maybe expand your methods.

I would like to throw in one more concept that the vang can be used for. The term is vang sheeting. Rather than go in to great detail on what this means I would just offer an article....
http://www.boomvang.net/vang.htm

If you do a google search you will find a number of different writers who have covered this subject.

On Pathfinder we have been vang sheeting for years. For the local sailors in SF Bay this method is almost a must in our ebb current chop. Vang sheeting allows you to maintain main sail power while saying high on the wind and in the favorable current while you are racing.

No preaching here just an observation. And in terms of loose foot or attached we sail a loose foot. But I guess that is somewhat like saying I like GM cars over Fords........ed

[John]

Ed,

Interesting comments. We all need to understand the controls we have to make the boat do what we want, and vang sheeting is one of those controls. With the wind you normally have, you tend to learn quicker, I think. And we never are going to be able to move the mast around like they do on the One Designs or even boats like the J's But here is an interesting note I found on the West Coast J29 site:

NOTE: It is recommended that you "sleeve" the long J/29 boom internally 3’ aft and 2’ forward of the vang bale as this will help prevent bending or possible breakage.

I do think we have a longer boom than is generally called for today, and so heavy vang use can call some modification.

As far as loose footed mains, you pays your money and takes your choice. I found another comment from a sailmaker that makes sense. And that is that loose footed mains are the product of better sail materials, and these materials don't need the support at the foot that older materials did, to maintain shape in the sail. He also pointed out that the outhaul becomes a more important tool for all the reasons cited earlier.

This has been great and I hope to see some more comments from others. It has gotten me to think, for sure.