cartop design suggestions

Dear Forum,
I am looking for suggestions for plans for a cartopping boat powered by motor and oars. As I am a novice boat builder with modest woodworking skills, I plan on using the stitch and glue method of construction. Besides having been interested in building a boat for some time, the prime motivation for this particular boat is to allow me to access barrier islands on the Gulf coast of Texas. The water that I need to navigate is shallow and protected from the open Gulf, but prone to chop and wind. I would like to be able to make the crossing in under an hour, so the boat needs to be capable of 8 mph, preferably 10, while loaded with 2 people plus camping gear (minimum people +gear 400 lbs). I would also like to able to row it although I recognize that these desires are somewhat in conflict. Finally it needs to be not prone to swamping or capsizing if the wind should come up. To cartop it, I need it to be no more than 100 pounds and have a maximum beam of about 50”. I have considered a motor canoe design, but as I understand it, the maximum speed of these displacement hulls is set by length and for common lengths should be about 6 mph. Any ideas / suggestions? Am I trying to square a circle? Input is very appreciated.

 

try http://bateau.com/

 

John Gardner designed a nice 11' cartop semi-dory, that was planked with lapstrake 1/4" plywood (if I remember right). The plans are in both The Dory Book and Building Classic Small Craft.

My copy of each seems to have wandered off to Oklahoma with my nephew when he moved back there this year, or I'd scan the plans and send them; I seriously doubt Gardner would disapprove if he were still around.

Building Classic Small Craft is still readily available for a reasonable amount of money, I think. But when I decided to replace my copy of The Dory Book instead of making my nephew return the old one, I discovered it's out of print. I just did a quick search, and found five copies online: three paperbacks and two hardbacks, ranging from $114.00 to something like $236.00. Ouch.

I would say it's worth hunting up a copy of Building Classic Small Craft; Gardner knew his stuff.

 

Just make sure the car top rack is well secured and even then don't depend on it to stay put. Lines fore and aft to car structures are vital. I knew one guy who tied his canoe to the roof and tied the lower end around his tailpipe. When the pipe got hot it melted through the rope and guess what happened next? Yep the boat became roadkill.

 

How about a very long square stern canoe, fitted with the amas for stability?

http://www.boatdesign.net/forums/boat-design/trimaran-motorboat-stabilized-monohull-29665-3.html

Porta

 

Sounds good.

 

Doesn't sound very practical for a cartopper.

 

If made so it can be easily assembled and disassembled, it can work very well, as one did for me nearly 40 years ago.

 

OK. Hard to argue with someone who's owned one, especially when I've never even played with one. I figured a rig like that would be a pain to put together and take apart, and that it would be a nuisance to stow or tie down multiple pieces. But I've never tried it....

How well would a setup like that handle the chop and wind he mentions? As I said, I've never had any experience with them. One reason I suggested Gardner's boat, aside from the fact that plywood lapstrake is relatively easy for amateurs, is that semi-dories are fairly seaworthy.

 

The one I had never had to deal with seas, only wakes. It was put together on the bank with large bolts and wing nuts/fender washers. Easy assembly/disassembly and tied to car on top of roof racks. Many hands make light work.

 

There was an article in Wooden Boat Mag #208 (May/June 2009) about a couple who refurbished an old 22 foot canoe. They put a transom on it to take a 25 hp outboard and reported getting over 20 mph. They were using it on northern rivers but encountered 6 ft chop in places and the odd rapid. It was a big canoe, 2+ tonne capacity, you could manage with less I expect.

Canoes and other narrow-hulled boats routinely exceed theoretical displacement hull speeds even under human power, planing isn't the only way to do that.