Hi all,
I haven't posted a design in a while. I have been working on one that is more involved than the others, I have done; particularly when it comes to drawing them. Anyway, there is a new directory, Raider, under "Gardner's layouts" in the file section.
To get through the basics, this is a design for the "raids" that are becoming popular here in the states. This will sleep 3, for short periods of time, and is designed to be easy to transport and launch. It can be shipped in a container, folded while on the water and trailered. Bare weight should run about 1000 lbs, but I have not calculated it out exactly yet.
Now to get on with the odder things about the design. I don't know how well I can explain these with just words, so you will probably have to refer to the drawings to make sense of them.
It has a new folding system, where he beams pivot around the masts (it is a 2 mast schooner rig). By having the masts support the beams, the lw hull can be truly minimal. As drawn, it can be made from a single 8' wide panel, 38' feet long. The beams come up the mast and there is a bearing so that they can pivot around the mast to let the boat stay upright while folding. The beams are each a single piece from the mast to under the bridgedeck area, so they should be easy to make strong. There is a second, half-length, lightweight beam with a pivot pin under the bridgedeck and another at the midpoint of the real crossbeam. This secondary beam only has to be strong enough to support the boat in calm water while folding.
The rudders are beam mounted. The are also asymmetrical, so they don't need to flip 180 degrees when shunting. Instead, the beam bearing is free to rotate +/- 20 degrees or so to let the rudders cant to bring the center of pressure "aft". I know this was tried before and found that the rudders will not cant on their own, due to the water pressure. So, I have added a mechanism that will pull the rudder into the correct position automatically.
The direction the rudder should cant is the same as the direction of movement of the boat. The wingmast and boom will always be trailing aft of the direction of boat movement, so I have added a bulge on each side of the mast, to act like a cam when the mast rotates. When the boom is brought around to the opposite direction during a shunt, the cam will move a lever, which is attached to a bungee, that will pull on the rudder assembly to make it rotate to the new position. As the boat stops at the midpoint of the shunt, there will be no water pressure on the rudder and the bungee with rotate the rudder assembly to the correct canted position.
The rudder assembly is constructed around a beam mounted drum, to allow the canting back and forth, and also has a breakaway "fuse" that allows full rotating in case of the rudder striking something in the water. There is an arm coming out from the bearing, which has a vertical pin, allowing the port/starboard rotation of the rudder for steering. The arm is positioned to act as a stop to prevent the rudder from oversteering to the point where there would be excessive stress. It is anticipated that a steering range of +/- 30 degrees should be adequate. The steering pin is attached to a daggerboard case, which secures the rudder blade, but also allows it to be raised and lowered. When fully raised, it can be above the level of the boom, because in the event that the boat is backwinded, the boom hitting the rudder blade will act like a grounding and break the fuse, allowing the rudder to rotate out of the way.
The rudders are mounted inside the beams, because the canting mechanism means that the rudder is lower in the water when the boat is travelling in one direction vs the other. With this rudder placement, the stern rudder will be deeper in the water that the forward rudder, moving the boat's center of lateral resistance aft.
I have put quite a number of ideas into this design that I have not seen drawn up this way before, so i am particulary interested in how it looks to the rest of the group. Please give me feedback.
- Gardner Pomper
Pasadena, MD
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