Earthrace Design?

[Matt.D]

I know eathrace has been discussed before and a few diff variations there of but has there been any designs incorparating that style of hull in a catamran format?
Any reason why a displacment hull of that shape wouldnt work in a cat?

[Jarrod]

Hi Matt,

Earthrace has definitely attracted a lot of attention over the years.

Do you mean a wave piercing catamaran?

[Matt.D]

Hi Jarrod , the thing is a when u look at wave piercing cats they look completely different to the ERace hulls.
Im thinking of a set of hulls in the shape of the ERace hulls but twice the hight of standard cat hulls to allow for any wing deck slapping due to the hull piercing the wave rather then ridding up over it.
Any thoughts???

[Jarrod]

Hi Matt, What length catamaran do you have in mind? Speed?

[Matt.D]

20 mtr and cruise at 12 knts would be good with as little fuel useage as possiable, any input on motors would be appricated too. Matt

[HJS]

Matt D

A catamaran will always need more power than a trimaran if the payloads and over all weight is the same. The only situation where the cat can be superior is when you need high stability.

The cat has more wetted area than the tri with the same displacement. To that comes the added drag of the interference of the two hulls bow wave in the tunnel. In planing cats this is avoided by choosing a flat tunnel side.

On a tri the bow wave from the main hull can interact with the sponsor hulls in a positive manner if the position of the sponsor hulls are in the optimum place.

With the same living volume I would prefer a slightly longer trimaran than a beamier cat. A longer boat is always more capable to meet waves. The air drag would also be lower.

Depending on the weight 20 meters and 12 knots is just a little to fast, according to my experience, but that is depending on the total weight and length. It needs more input than present figures. If proper designed the drag to weight figure can be around 0,03 in this case.

See more on www.zeroemissionboats.com and www.sassdesign.net


js

[Matt.D]

Hi Js thanks for ur input,
I think aprox build weight will be around 30t.
What sort of speed do u think would be more realestic?
and why would 12kts would be too fast?
Questions Questions Questions!!!
Do u happen to know the formula for calculating displacment in salt water? I had it in a book some where but god only knows where it is
Got any ideas if u can successfully build a scale model in High Dens foam?
I have sean a few working models on u tube but they realy dont look like they interact to scale, Last question promise....Is the scalope out of the bow (looking side profile) of a ferry type wave piercing cat just to conserve weight or does it serve another purpose? Thanks mate!!!