loose footed gaff sail

[gaffer]

this is my 2nd year with a gaff cutter and last saturday we sailed her for 10 hoursin varied winds from 8 to 15 knots. as it got gusty heading upwind with the main loose footed (was usually laced) the forces on the boom were noticeable. I really like the set of the loosefoot but dont want to break the boom. can I make it stronger or go back to laceing it on. thanks

[Ed Nye]

That is a great question. I want to try it loose footed also, but have been worried about the extra forces on the boom. I have read that in a gaff sail the boom cannot be too heavy (the weight is good for the shape of the sail off the wind. I have also read that the boom for a loose footed sail must be stronger than if laced. Someone should know how much heavier the dimensions should be.
Ed

[ 04-30-2002, 09:27 PM: Message edited by: Ed Nye ]

[John B]

I won't reef my boom without tieing in the reef points because without the ties it's effectively become a loose footed sail. If the boom bends then it's too light for a loose foot. I've got nothing against loose footed sails , you understand, it's just that the boom needs to be stronger in construction/designed for it.
Can't have a boom too heavy ? I've heard that too Ed. I don't subscribe to it. It implies adding unnecessary weight is good. It doesn't account for shock loadings on the gooseneck in a sea or general wear and tear caused by the weight of the thing.

[Wooden Boat Fittings]

You know, don't you Gaffer, that JohnB sometimes gets a bit carried away with his weight-cutting theories? I swear Waione carries a hollow jack-staff to save weight.

As it happens, though, this is one of those rare occasions when I agree with him. (That surprised you John, didn't it?) But as he says, heavy booms do more than just tighten canvas, they add a lot of general wear and tear to various components of the vessel as well. Moreover, that bit about tightening the canvas comes from the days when sails were canvas -- heavier to start with -- that was then tanned, dressed, or otherwise treated against rot as well, adding even more weight. Today's sails are lighter affairs altogether.

So if you're concerned about your boom, I'd say either try running stiffening battens (maybe 1" thick) along, say, the middle half of each side to strengthen it, or go back to having a laced foot.

On the other hand, on his own admission John makes his boathooks out of broom-handles, so perhaps you could just ignore both of us,,,,

[mmd]

One way to stiffen a too-thin boom is to add a small plank on-edge on either side of the boom. They are usually 3/4" to 1-1/2" thick, depending on the size of the boom, and are about 1.5x to 2x the thickness in width. On larger ones it is common to scallop out the edge against the boom to make hand-holes, similar to a cabin-top handrail. They make a handy fastening point for awnings & other stuff when done this way, too. they should be about 3/4 of the length of the boom and centred along the length of the boom. I've seen them on the underside of the boom, too; but only rarely as the sheet and vang fittings usually get in the way.

[Todd Bradshaw]

Be advised that if your gaff main works equally well loose-footed or laced to the boom, there's probably something wrong with it. The foot panels and shape are often cut quite differently for the two applications.

[John B]

There's a good point about the sail.

Perhaps I could use that plank on edge idea to solve my gaff problem. I'll store that in order of easiest to hardest fix....

That broomhandle scarf extended boat hook? what a gem. 8ft long now. Just what you need with a skinny boat in a fat berth ( and short arms).

[Paul Jeffrey]

I have to agree with Todd the cut of a loose footed sails is quite different than the cut of a sail that will attached to a boom or club. As to the added loads on the boom there will be some. How much to beef up your boom is hard to tell here, don't know any of the sizes of the boom you have nor the sail area you have in the main. The gooseneck will take some additional compression so it should be checked.

But I have to say that about a year ago I read a report from a builder of a small gaffer that indicated improved performance with the main not laced to the boom. The sail he had was not cut for this but he said it worked. I found this interesting but never heard from the builder again so there was no follow up to the first report.

Loose footed mainsails work very nicely but should be cut that way and the clew needs to be well re-inforced on them.

[Smacksman]

You also need a powerful clew outhaul tackle adjustable from the deck on a run. Foot tension is one of the most important performance controls on a loose footed main.

Try also to get some of the mainsheet purchase directly below the clew cringle to triangulate the forces when on the wind.

and finally, bawleys not only have a loose foot but no boom at all. But then the sail is cut and rigged to suit. Check out http://www.alberta-ck318.freeserve.co.uk for loose foot with and without a boom.

Most things on a sailing boat are designed.
Few things are accidental.

[John Gearing]

Smacksman beat me to it with the suggestion to get the mainsheet purchase directly below the clew cringle. If you want to make the boom stiffer without adding weight and you weren't wedded to the idea of a trad, round boom, you could look into building a more more girder-like boom. The guys at Spirit Yachts use a T-section on some of their boats http://www.spirityachts.com/sy-gallery-18.htm
though their mains are not loose footed I don't think-- but still, something like that might work for you. Or you could try adding some hi-tech hi-tensile strength materials to the surface of our existing boom, or sink a rod or bar of that stuff just below the surface. Should provide more stiffness but whether it would provide enough or not I couldn't say. Perhaps something to think about however....

[Dwight]

Hi, folks. Let me start by saying that I don't know anything about gaff rigs - hope to change that in a year or two - but would like to comment on some points raised above.

Moving the sheet attachment to the back of the boom with a loose footed main will unload the bending moment on the boom, and you'll be left with (mostly) only compression loads. It is highly unlikely you'll need to strengthen the boom if you do this.

Wood will deflect quite a bit before a failure in bending - if you don't see much deflection with the mainsheet fastened to the middle of the boom in heavy winds, you likely don't have a problem.

Most booms are larger in the vertical plane than the horizontal because the bending is about the horizontal axis (mainsheet fastened in the middle, leech tension raising the end of the boom). To get more stiffness about the horizontal axis, you need more or stiffer material as far above and/or below the neutral axis (normally the centroid of the boom) as you can get it, hence the usual shape. As mentioned, one way to get this is by concealing stiffer/stronger material within the existing spar. I'd consider epoxying in carbon fiber strands. This is not an experimental technique, it is used commercially to strengthen concrete beams carrying real loads, of course they just epoxy the carbon fiber to the surface, in the case of a boom, you'd want to cut a groove and glue a strip of wood back over the stuff. In the case of the mainsheet fastened at the end of the boom, failure in compression will be buckling about the weakest axis of the boom (normally the vertical axis - boom would deflect horizontally). Insufficient stiffness about the vertical axis could also result in lateral torsional buckling. Stiffness (and strength) about the vertical axis can be increased as mentioned above by adding material to the sides of the boom, and since buckling or bending failure will occurr near the middle, the added material need not extend all the way to the ends, and may taper from the attachment point of the mainsheet. It is not likely you would need to do this.