Trimaran - Pontoon Design

I'm playing with the idea of designing a trimaran hull with the suspensioned pontoons through a 4 bar linkage system that would dampen the forces seen by the pontoons and allow for the angle between the boat and the pontoons to change.

The orginal purpose of making it a trimaran hull with the suspension sytem was so I could put two engines on the boat, with the c.g. centered in the main hull and have the ability of pivot turning (putting one engine in reverse the other in forward) while still keeping the boat managable so it's trailerable.

My main concern is this: Is it worth the time/effort/resources to have a highly manueverable design like this, or should I redirect my efforts else where?

 

1-Anything is worth the effort if it is a labour of love
2-It might be a fun exercise
3-You can pivot turn suprisingly well without doing that (unless she's say larger than 35 feet long)
4-what are you using it for?

 

TSITL,
You could achieve the same feeling (less "bounce") by putting the amas (pontoons) closer to the centre hull. As far as pivot steering, you can do that in a monohull with two engines.
But, as Thunderhead says, anything is worth it if it is a labour of love.

Steve

 

I've just gotten tired of the terrible turning in my boat and I want to make one that turns much better. Since I mostly do deisng work with tracked vehicles, I thought I'd use the same idea there and apply it to a boat.

True, the pivot steering is dependent on the twin engines, not the amas. The idea of having the amas was to put the engines in them and take up less space in the main hull.

As much fun as a labour of love would be, I still want to concentrate on a feasible design that I'll be able to accomplish.

 

Well--I lived aboard a forty two foot trimaran for four years and used a single Yanmar . Diesel. If you want to avoid the necessary rigidity of trimaran beams and hull connections-build a Wharram cat instead. Trimarans need to have massively strong beams. Making them flexible will work only for the really tiny ones such as are used by some islanders in the Pacific rim, and only then if the proper flexible material is handy. If you can not get your hands on the heavy and very strong coconut outer trunk--you are going to have to laminate them somehow out of expensive selected timbers, or craft them from fibres laid into an epoxy or polyester resin. Trimaran beams are the main source of concern as regards the seaworthiness of any trimaran. The stronger and better fixed they are, with stresses distributed into the main hull and amas over as wide an area as possible, and firmly bonded to the hull structural members, the better I like them.

 

If you want the boat to turn well then get the ends up out of the water or nearly so. You will have a displacement boat that is not fast, but it will go very well with small power and be economical to operate. Such a boat can do 360s within very little more than its own length if you get the design right. Certain small sailboat owners brag that their boat "turns on ball bearings".

 

Why not install a bow thruster?

 

Bow thrusters are heavy, expensive and costly to maintain. I have thought about the trimaran problem of three hulls and one rudder aft of the screw many times over the years--and so far all I have come up with as a possible solution (in the case of my Piver) is outboard legs fitted aft of the amas. These would be hydraulic and lifted clear of the water under sail. They would not need to be too powerful--5 horsepower each would do it as long as I still used the main engine screw for motor sailing. If I eliminated that main engine screw and used a hydraulic system entirely--I would need at least 10 horsepower equivalent legs on each ama and extensive mods to the hulls and beams to transfer the loadings safely into the trimaran structure. It is still a work in progress--but to this end I am fitting an extra crossbeam right aft linking the main hull to the amas right where the outboard leg fixing system would be located.

 

I think your solution is pretty complex ....

I don't think bow thrusters are perfect. But, they lack complexity. Not more expensive, while delivering better control.

IMHO.

 

Trimaran

At the end, do you want something like this cruising trimaran?

 

Hi Mike,

Just wondering how you found the motion of your Tri at sea?
I was looking at a this power tri, and the round bilge seems to be very flat at the stern. Do you get slamming at higher speeds?
http://www.multihulldesigns.com/designs_stock/38tri.html

The fuel estimates seems to be extraordinarily good.....