Dory Hulled Catamarans

[michaeljames]

[img]smile.gif[/img] I have been researching dory hulled catamarans and would like some feedback from anyone with experience along these lines. I want an extreme shoal draft (18” or less boards up) so I can set up on the mud if I choose, no thru-hulls, 24-30 ft +-, build with ply/epoxy, minimum rig and built for function, with some character that doesn’t look like it’s setting in a Detroit Auto Showroom. I had thought of building a St Pierre Dory after a sailing version I saw in NC couple years ago, tender but was a stand-out in the harbor where it was moored. Still I have been trying to get away from mono hulls and rocks in my boat, and I like the deck space, even a modest cat can give me, and a good dive platform. I was working from drawings of the Hawaiian style cats. I have had the Wharram cat design catalog for years, some aspects I like, others not.
I have found a couple of web sites with dory shape hulls, both hulls are truncated, eliminating the “deep V”. One site, www.catamarandesigns.com has two designs similar to what I was drawing up, they, however have failed to respond to any of my email, so I have given up on them, but I like the simplicity of the design.
I’m going to send off a fax to Bolger & Friends on Monday and see what they have in stock along these lines.
Other sites: Woods Designs at www.sailingcatamarans.com.
Selway Fisher Designs. www.selway-fisher.com/yachtcats.htm

MJ

[Gary Dierking]

Dory shaped catamaran hulls will perform well as long as you don't have the flared sides usually seen in dories. Keep the sides more vertical for good performance in a seaway. A Bolger box shape is better than a flared side dory.
It's all about how you enter an oncoming wave. The flared hull will rise and pitch causing a reduction in drive from the rig. A slab sided hull will penetrate the wave face and keep the rig steadier to develop the power you need for good windward performance.

[AngWood]

Have you looked at www.jonesboats.com ? Not sure if you're looking for something like this (I gather you're seeking flat-bottomed hulls?), but it's worth a look.

[JimConlin]

You might also find James Wharram's designs appealing.

[bainbridgeisland]

How much performance are you willing to give up for the simplicity of a dory hull?

Multihulls are very sensitive to added wetted surface. Therefore, dory hulled catamarans are generally poor sailors in comparison to a multichine or round bottom hull of the same sail area and proportion. Since most of the effort building a boat is NOT in the hull, the extra time spent making a slippery hull is a minor added effort in comparison to the whole project.

There are some fast ways to build plywood catamaran hulls that are round bottom. Look for compound curved plywood hulls (like a Tornado cat), Constant Camber hulls (like John Marples work) or Cylinder Molded hulls (like Kurt Hughes designs). All of these methods have limitations but can produce fine boats when designed correctly.

While in High School, 35 years ago, I designed and built a flat bottom wall sided catamaran. It was 16' long and was light, about 160 pounds, with a hull beam 1/20 of length. Even with this light weight narrow hull boat, performance was very disapointing. It was especially slow in light to moderate air. This was a classic example of too much wetted surface. I would have been better off with a sharpie monohull in light to moderate winds.

[chill]

Look at woods catamarans

www.sailingcatamarans.com

I am building a 28 foot dory hulled catamaran of
his design (Gypsy)

[michaeljames]

Okay, thanks for all the info/insight folks.

It actually snowed here last night. I guess I didn't go far enough South for the winter!

Michael

[Nick C]

While the dory shape on a catamaran is not going to be the best for performance, it would have an advantage if you are going to be packing big loads on occasion.