20 foot Freighter Canoe

[TimothyM]

the 20ft plywood hull would take about 8 sheets of 12mm and 3 sheets of 18mm marine ply plus glass cloth and maybe 5 gals. of epoxy. It would be a little quicker to build, but not cheaper or easier than a strip version. The strip version can be built with 1/2" strips right off the table saw.

[TimothyM]

Originally Posted by Easy Rider

Timothy,
I'd LOVE a 26' version of that plywood boat. What is (in inches) the rocker in your 18' boat?

26 feet! wow! go big or go home
are you asking about the rocker on the plywood boat or my original 18' freighter?

[Easy Rider]

Timothy,
The 18' stripper for the rocker. Most canoes don't have hollow ends and are dependent on rocker for maneuverability and pitch control at various speeds. In my opinion the rocker and cross sectional shape of the bottom determine 95% of what a canoe will do in the water. Very small changes in rocker can make big changes in how a canoe will perform in various ways. I think you sell plans and one could scale up or down in size quite easily.

[Hussong]

Originally Posted by Easy Rider

The 18' stripper for the rocker. Most canoes don't have hollow ends and are dependent on rocker for maneuverability and pitch control at various speeds.

From what I have seen, most canoes do have very narrow ends, even if they are not extreme in design with exaggerated hollow forms. As a result, an amount of pitch stability is inherent, even without a generous rocker present, such as one sees in modern tripping canoes. Pitch control can be achieved by any of a number of potentials beyond rocker design, with load trim being the most powerful.

Originally Posted by Easy Rider

In my opinion the rocker and cross sectional shape of the bottom determine 95% of what a canoe will do in the water. Very small changes in rocker can make big changes in how a canoe will perform in various ways.

Rocker and cross sectional shape contribute to the potential of a canoe, to be sure, but they are not the only elements of a successful design that have an impact. Asymmetrical, or symmetrical, shapes fore and aft also contribute heavily to the performance of a canoe, depending on design criteria that is connected to the use of the boat.

Originally Posted by Easy Rider

I think you sell plans and one could scale up or down in size quite easily.

Not necessarily. For example, extrapolating rocker profiles to a much bigger hull by percentages, may be an acceptable place to start an exploration of a larger boat with similar characteristics, but it's not the whole story. Unfortunately, canoe design, while having been ushered, successfully, into the modern realm by naval architect, John Winters, some years ago, is still a place where some of the black art of "feel" still remains. This means that many boats on a given theme might be necessary to hit the magic point where it does all that it is supposed to provide.

I encourage you to experiment until you find that special place for yourself.

[TimothyM]

The original 18 foot stripper has a rocker of about 1.5" That boat handles great in river current and can still be paddled like a canoe. I also have designed 18,20 and 22 foot models with a wider transon and a straighter run aft. The 20 footer in this thread is of the wide transom design.

[Easy Rider]

Hussong,
Hollow was expressed as a relative thing and Kayaks are very hollow compared to canoes. Perhaps I exaggerated when I used the number (95%). I'm looking at building a big Atkin skiff or a huge freight canoe but I'm beginning to think it's hopeless as I need to use a 60hp Suzuki OB and it's too heavy and powerful for all except a 27' Atkin inboard used as an OB. It's Marcia if you'd care to comment. I think I know most of the pitfalls converting an inboard to OB and I think Marcia will go there gracefully. I want to replace an 18' FG deep V and use the 60hp engine.

[Easy Rider]

Timothy,
How do you fasten one strip to another or is the overlays enough to keep it all together? I'm think'in perhaps I could work on a boat in rather cold weather as time in the summer is rather dear here. How much of your canoes could I build under shelter (just a big roof) at 40 degrees and fairly high humidity?

[TimothyM]

the strips are just edge glued, so you would need to find a glue that works a 40 degrees and high humidity

[Hussong]

Originally Posted by Easy Rider

Hollow was expressed as a relative thing and Kayaks are very hollow compared to canoes.

Except that kayaks are completely different forms when compared to canoes, so why offer a term that does not fit the boat being discussed?

Originally Posted by Easy Rider

Perhaps I exaggerated when I used the number (95%).

Yes

Originally Posted by Easy Rider

I'm looking at building a big Atkin skiff or a huge freight canoe but I'm beginning to think it's hopeless as I need to use a 60hp Suzuki OB and it's too heavy and powerful for all except a 27' Atkin inboard used as an OB. It's Marcia if you'd care to comment. I think I know most of the pitfalls converting an inboard to OB and I think Marcia will go there gracefully. I want to replace an 18' FG deep V and use the 60hp engine.

That is way too much engine for an easily driven canoe form such as you suggest. Drop the engine size, enjoy the increased vessel efficiency, as well as the lack of overall displacement robbing weight and have yourself a dandy boat that is able in a wide spectrum of conditions.

[TimothyM]

the beauty of the freighter canoe is that you can push them with less horse power and use very little gas

[Easy Rider]

Hussong,
The concept of hollow ends can be applied to any hull.
Too much engine .....not for the Atkin Marcia. She is spec'ed for about 70hp. I paid well over $5000 for that Suzuki and I'm a bit reluctant to dump it. Only have about 30 hrs time on it so I need a boat that will run about 15 knots with 30-35hp. The Atkin "Tang" would be another good boat if the inbd to OB conversion went well as I think it will. Any other boats anyone can recommend? Keep in mind I want 15 knots w a bit less than 40hp. When I sell the FG 18' boat I may sell the engine w it ...and trailer.

[Hussong]

For your stated needs with that engine, I'm seeing a slender hull form of 28', with a displacement of something around 4000 pounds. Wide hulls would require more power for the indicated speed needs.

[Hussong]

The concept of hollow ends can be applied to any hull, as you say, but in the case of a canoe hull form, they are typically not. Sea kayaks, yes, but not your typical, recreational canoe.

Canoes have all sorts of different design needs when compared to sea kayaks. Not the least of which is that the paddler is centrally located in virtually all kayaks (yes, even doubles when the weight placement is averaged) But, in canoes, the paddler is out at the ends of the boat, forcing fuller ends to compensate for the flotation requirements and to combat pitching effects when unladen.

Solo canoes can follow more in the design motif of the everyday sea kayak, but they usually have quite a bit more max beam, which turns the comparison on its nose. Look at the prismatic coefficient of the two styles of human paddled craft and you will see a bit of what is going on in the design.

Racing boats from these types take a totally different approach, so stay away from that comparison.