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View Full Version : Sockets, lashings & crossbows



BrianCunningham
12-21-2000, 04:31 AM
I been thinking about using "saddle mounts" with lashings ala Wharram, instead of the pocket mounts CLC uses to secure it's crossbeams to the floats and kayak of my trimaran.

I originally directing the crossbeam into a socket would be the best way to go. But now that seems more of a stress riser. The crossbeam always trying to "force" it's way through the mount and out the side of the float's hull. The crossbeam would not be tied directly into the shear clamps. The pocket would also collect water. Where I'm not to worried about airing out a daysailer like SWIFTWOOD, this would be a problem on a bigger sister. There would have to be some sort of drain hole. On the other hand any upward force would serve to hold the joint together. Mechanical fasteners are really only necessary on the windward side to keep that hull from falling off, since its up in the air.

Let's look at the saddle mount. The first thing that can be done is to run simple beams straight across all three hulls, then make the appropriate saddles to keep the height and orientation, keeping the floats angled out. This would eliminate the need for a hole in the top of the hull. One could even kill the bulkheads. Four are required in each hull since one has to box in each of the holes. This would make the hull a single compartment. Is this a good thing? Well, you could inspect the entire float with one inspection port.
But as far as stress is concerned, should at least on bulkhead be placed under each of the saddles?

If this is to be the route how are the saddles to be constructed? The simplest method is to make them out laminated plywood and bolt them to the shearclamps. These mounts would be kind of low in the water, a problem more for the floats which regularly run up ( and sometimes past ) them. You could streamline them as CLC does by bolting an angled piece of metal to the shearclamp which swings the saddle to the top of the deck. But why not just fasten them to the shearclamp through the deck?

The saddles could also be changed out. So variations on mounts and crossbeams can be tried out, which appeals to me. I'd like to see what difference straight verses curved beams make. The curve at the saddles would serve a different purpose than socket plugs. The ends could be bowed like that of a crossbow, and the loads would be quite different. Experiments with soft, sprung crossbeams could be taken.

But I diverse...
Thoughts?

Charlie J
12-21-2000, 09:00 AM
Brian - here's a site you might find interesting- http://www.watertribe.com/
Scroll down to the article called "Wango Tango Aka lashing" He has done some mods to a CLC sailing rig along the lines of what you are thinking

BrianCunningham
12-23-2000, 06:42 PM
That's along the lines of what I wanted.

http://www.watertribe.com/Magazine/October2000/IsaacLRAkaMount_small.jpg

Though I might go straight to the deck in order to keep the mounts out of the water.

I'd have to make sure it's tied into the sheerclamp though.

Here's my current setup
http://homepages.go.com/~briancunningham/maststep/img35.jpg