This is an idea I’ve had for a while but haven’t had time to fool with.It is an idea that should create a relatively quick 100% self righting catamaran model.
The idea could be applied to any size cat but probably would not be competitive with a well designed “normal” multihull(not competitive with a properly designed foiler at all) but could potentially be a trainer as well as a lot of fun.
The rig would be a single offset pivoting main(see pix of the micromoth rig on this section of the website under “MicroMoth” posted by Chad) This allows a MUCH smaller servo to be used for the mainsheet than normal–a 3003would do it(s148 replacement) converted to 180 degrees(for a one meter multi). Radio South does this kind of conversion inexpensively.
Visualize two hulls with a single carbon tube(5/8" dia. approx. for a one meter 1" for an F48) cross arm-overall beam about 68% of length. In the middle of this cross arm is mounted a module that extends about 2.5" aft of the cross arm having a squared off back end and going about 3-4 " forward of the cross arm tapering to a point more or less.
Coming out of the squared off back end of the module is a carbon tube about a half inch in diameter extending maybe 6 " aft.
A thin carbon keel(ideal but not the only solution) is made with a carbon tube integral to it across the top of the keel. The keel is then slid onto the 6" tube sticking out the back of the module and a stop attached to prevent the keel from sliding off.
You may be able to visualize that the keel so attached will swing sideways until it hits the hulls on either side and should be long enough that the bulb on the keel is outboard the beam of the boat say about as far as half the length of the boat.
The module in the center of the boat could have a little hatch to allow access to the radio equipment inside. The boat needs: 1) one Guyatt 280 that will be hooked to the keel just above the waterline(or to an extension of the keel above the pivot point) so that as the winch is engaged the keel pivots to either side untill it almost touches the hull(s).
2) a quick 50-70 in oz servo to attach to the keel to slide it fore and aft.
3) mainsheet winch as already described
4) rudder servo attached by various means to the twin rudders on the stern of the boat.
The boat could be three or four channel : if you wanted the simplest set up the servo that moves the keel fore and aft would be connected by Y connecter to the mainshet channel such that as you ease the sail out the keel moves aft. Or you could independently control the fore and aft movement of the keel. Mainsheet woud be on the left stick as would be control of the sideways movement of the keel.
One other thing: the boat would have no daggerboards or centerboards since the keel would provide lateral resistance. The keel bulb would have small wings on it(like the full size BondiTram) that would develop lateral resitance when the keel is out to the maximum on one side.
The beauty of this is that the boat is relatively simple yet has a fully effective movable ballast system that can also double as a righting system after a capsize or pitchpole.
The simple unstayed rig could be reefable so that one rig is all that would be needed.This boat could be built for under $500 including the radio I’m guessing… If anybody is interested in trying this I can send a sketch and might even contribute something toward a prototype…
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing