The Gaff Saddle

Ganymede's Gaff Saddle needs some redesign.

Gaff Saddle attempt 1: saddle insisted on riding on it’s upper edge, doing violence both to paint and leather. Turns out the peak was outhauled too tight, and there was no bridle from saddle sides to halyard block.

It was a matter of much mental debate, while designing Ganymede’s rig, whether to have gaff jaws or a saddle.  What can be said for jaws is that they’re pretty foolproof, with no moving parts (unless you have a “chip”—not necessary on smaller boats), and very easy to design.  In favor of a saddle is easier load spreading and less binding on the mast from twist, with nothing sticking out past the mast forrard of it, like the legs of a jaws must do.  Those little sticky-out legs tend to catch all sorts of lines—topping lift falls, stray halyards, anything, and bind up good and clustered.  The solution is constant vigilance, but a well-designed gaff saddle negates that to a certain extent.

Sketch of gaff and saddle arrangement--side view

Ganymede’s gaff saddle as it now exists: note the bridle to keep the saddle from tilting up and riding on it’s upper edge, and the dyneema extender on the gaff so that the bridle and halyard attachment are at the optimal relationship to each other

Though it seems a simple thing, the saddle is harder to design than I first imagined.  First off, the business end of it tends to try and capsize as you hoist or strike the sail, like a truck that jacknifes of the highway.  This is made worse if the leather gets a little sticky, like in damp weather, and won’t slide on the mast as nicely as one could wish.  After a few struggles on the shakedown—moving the halyard attachment from the saddle to the gaff itself, putting a temporary downhaul on the forward end of the saddle, I hit upon a bridle of sorts, rove from the parrel bead attachment points to the halyard attachment.  Works like a charm most of the time, though if in a real hurry the saddle can still get unruly.

Sketch of gaff and saddle arrangement--top view

Bird’s eye view of gaff saddle and the tweaking that occurs when the gaff rotates. This can be quite violent when the boat tacks or gybes.

Another engineering surprise was how much twisting force the gaff puts on the saddle “ears”—the bits of aluminum bar stock that join the saddle to the gaff.  As the gaff is eased out, it tends try and rotate between the pull of the halyard and the leech of the sail.  The saddle, of course, does not twist, so the ears take all that strain.  This is worst during a violent gybe, or when flogging in heavy, swelly calms.  Ganymede’s got tweaked back and forth quite a lot, doing violence both to the ears and to the hinge-pin-hole in the gaff, until I had a Mexican welder fit some bar stock between them to stiffen them up, and sleeve the gaff extrusion at the pin-hole.  Of course he didn’t fit them perfectly straight, so they’re forever slightly tweaked, but everything has been tighter and better since.

The further the gaff can swing outboard, the better downwind sailing will be

A gaff saddle will allow the gaff to swing further outboard before hitting the lower shrouds than will a wooden jaws. Even a little bit of play inboard translates to a huge amount out at the peak.

One of the reasons to prefer a saddle over jaws is that jaws are traditionally wood, and have to be made thick, for strength, just where they ought to be thin for clearance.  When eased out, the jaws usually chafe against the lower shrouds, putting unecessary force on them, and doing slow damage to both.  The saddle, however, has plenty of clearance to allow the gaff out further.  The solution might just be to make jaws of carbon fiber, which would be lighter, stronger, and far lower-profile than wood, without the mechanical complications of a saddle.  Now that I’ve spent a winter working in a high-end composites shop and understand carbon and all such things a little better, I’m determined to give it a whirl—maybe not soon: my list of other more pressing concerns is long, but hopefully before the end of summer I’ll have a prototype aloft on Ganymede for a test.

Not necessarily pretty, but rugged and functional after some fine-tuning.

Ganymede’s gaff saddle getting some overdue attention. Note the aluminum stiffeners welded crudely across the tangs–Mexican Welding at it’s finest! It did the trick, though and the tangs never tried to tweak again.

In the meantime, her old saddle is getting a new coat of primer and some other attentions, and will continue sufficient for it’s task for another season, at least.