New Monohull/Multihull Hybrid Sailboat

[tatria]

I am an Industrial Design student working on my thesis. My challenge was to create a sailboat about the size of a laser boat that could sail faster than a Laser 1. The price of it had to be about the same of a laser.

My design: I created an hybrid of a monohull and a multihull. At low speeds it will work as a displacement hull and a tunnel effect will be created under the sailboat to lift it from the water, reducing drag. Then it will start planing at higher speeds and will work as a catamaran providing enormous stability. It also has innovations in the keel and sail, but at this moment I`m interested in knowing your opinion about the hull.

Here are some renders:

http://auction4.comton.com/member/cl...rendertomy.jpg

http://auction4.comton.com/member/cl...rborrador2.jpg

http://auction4.comton.com/member/cl...erborrador.jpg


Thanks Tomás Atria

Santiago, Chile

[gonzo]

I've been experimenting with something similar. There is potential. The problem with the wedge shape is that it will be very unbalanced. Look at sandbagger designs. They are very developed and tried.

[tspeer]

Originally Posted by tatria

...My design: I created an hybrid of a monohull and a multihull. At low speeds it will work as a displacement hull and a tunnel effect will be created under the sailboat to lift it from the water, reducing drag. ...

The I-20 (formerly M-20) inland lakes scow has just such a hull. It has the traditional scow sections at bow and stern, but the belly humps up into a tunnel that reduces wetted area. Like all scows, the I-20 is designed to be sailed at 15 degrees heel, which gets half the bottom out of the water. The I-20 has two bilge boards and two rudders that are angled out so as to be vertical when heeled. The windward board is retracted and rudders are short enough that the windward rudder is out of the water at the design heel.




The scows plane very easily when sailed upright, and they have a semi-planing regime in which the stern wave is perched under the long gently-sloping run, allowing the boat to recover some of its wave drag. In effect, it is surfing its own stern wave. This makes for a very smooth transition from displacement sailing to planing with a significantly reduced drag hump. There's no wild leap onto the plane, as with some dinghies. Once planing, the twin low-aspect ratio rudders provide finger-tip control. At low speeds, the scow hull offers no resistance to turning, so the small rudders are adequate. Put both boards down, and the boat can spin practically in its own length.

There was a small scow called the Butterfly that is the size of a Laser, and is still actively raced in the US Midwest.



I highly recommend you consider a scow hull for your design. A tunnel-hulled version of the Butterfly would be a great choice.

Twin bilge boards really open up the cockpit, because the board trunks form the sides of the cockpit instead of being an obstacle. The side decks then become the structural support for the top of the board trunks. Scow boards are just thin sheets of aluminum with a bit of bevel on the trailing edge and rounded leading edges. The flat-plate section is fine for the high speeds they sail, and it makes for a narrow board slot.

The MC scow is a 16 foot single-hander with two boards and one rudder, while the M-16 is a double-hander with two boards and two rudders. Both use the exact same hull. So you could go with one rudder for simplicity and low cost, or two like the I-20 & M-16. It's very convenient to have a tiller sitting right beside you and only a short hiking stick is needed. The rudders are linked together by a connecting bar that has a toggle at each end. With two rudders, you could open the transom in the center, allowing very rapid emptying of the cockpit after a capsize. Although you could get the same effect with an open transom and a bar across the top to hold the upper gougeon. But twin boards or rudders may be too much for such a small boat. As you can see from the Butterfly, it's possible to locate the board forward of the cockpit, as with the Laser.

Cheers,

[tatria]

Thanks, is a good idea but I m planing to buy a broken laser boat and modify it's hull to reduce the cost of the prototype.

[Wardi]

Being a scow sailor, I agree with Tom!
You will end up with a big balance problem and heaps of helm. The scow design solves this completely, with almost perfect balance, enables you to heel to reduce wetted surface in the light and then gives an excellent stable planing surface for high speed sailing. The cat hull is only better if the "hulls" are parallel and the main hull lifts clear of the waves. This is quite difficult to achieve.

A Scow Moth is competitive with Laser and much faster in a breeze!

[tatria]

thanks for your help, I will reconsider the design, the scow design seems to be a good choice

[tspeer]

You could still use the damaged Laser, since you're building a new hull. Just add onto the deck to fill out the scow bow.

[scowsailor2004]

Most scows, also, have their bilge boards canted a degree or two to windward. It acts like a foil and helps reduce leeward slip. There are not many boats out there that can point higher than a scow.

[masrapido]

Y como anda este proyecto entonces? Si aun tienes las imagenes, me gustaria verlas. Saludos,

[cleblanc]

Please look at the Laser Vortex, it is a very interesting design that seems to be exactly what you have described.