Solo Canoe - Length Verses Hull Speed

[AlanP]

With sailboats, the longer the wetted hull, the faster the boat. Does this equate with canoes? That is, if two canoes both with the same weight but one is 12 inches longer and 1 inch wider, would the longer slightly wider boat be faster with a given (but old) paddler? Would you need to be strong enough paddler to realize this?

 

[ppine]

Yes it equates. When change the beam or hull shape you may mess up the relationship. Look at racing canoes, they are all long and narrow.

 

[AlanP]

The manufacturer for both canoes is the same that being Dave Curtis (Kestrel and Peregrine).

 

[Guest]

I know I can go faster in a Kestrel because I don't have the horsepower to drive a bigger boat with more skin friction to hull speed.
Turtle

 

[AlanP]

Thanks Turtle, that's what I thought. My only concern is if (and I said if) I ever going solo tripping, my total weight (154 + stuff) would be near the high end of the capacity efficiency range of the Kestrel.

 

[memaquay]

John Winters has formulas (formuli?) for all that stuff. I'm not a math guy, or even all that smart, but I think the long and the short of it was that after 18 feet, the benefit of length for most paddlers starts to drop off.

 

[madmike]

http://www.greenval.com/shape_part1.html

 

[tump_lion]

totally anecdotal evidence, but a 17' prospector goes noticeably faster than the same brand, nova-craft, in 16' when loaded with similar loads...catches more wind too...

 

[Alan Gage]

I personally don't think the difference amounts to a hill of beans for 95% of paddlers.

I've done a lot of paddling with a GPS and heart rate monitor to try and get an idea of the speed and efficiency of many different boats I've owned. I've also been tinkering around with hull design and using Winters' Kaper software that plots speed vs. resistance. Yes, in general, making a boat longer makes it a bit faster on the top end. And, in general, taking off 6" to 1' of length gives less resistance at low/medium speeds. But these differences, in my opinion, are slight.

The speed advantages of a long hull don't really come into play until you get above power levels most paddlers don't want to maintain for more than a couple minutes. And the efficiency advantages at low speeds offered by a shorter hull are somewhat negated by the fact that it takes such little effort to maintain those speeds anyway.

The padder is what really makes the difference when it comes to speed although it's an unpopular answer and one I try to ignore myself, always searching for the elusive magic canoe.

More important, IMO, is how the hull shape fits with your paddling style. A long straight keeled hull might feel slow to a single sided paddler when it doesn't want to respond effortlessly to correction strokes and a shorter, more maneuverable hull, might feel slow to a hit and switch paddler when it constantly wants to yaw back and forth requiring correction strokes.

Alan

 

[Alan Gage]

Been thinking about this some more and I can see where my experiences may be different than others. The original poster asked about a boat that was a little longer and a little wider. The boats I usually paddle either stay the same width or get skinnier as they get longer. Perhaps this keeps the low speed efficiency on par with the short fat hulls and is why I don't see much of a difference.

But I think it also underscores how little speed is actually gained by adding a little length, especially if beam is increased at the same time. A longer boat will give you more potential speed but it doesn't come free, you have to work for it. But it's a nice reward. Better than working your tail off just to make a bigger wake.

Alan

 

[yellowcanoe]

1.55 x the square root of the waterline length is theoretical hull speed. Note absence of width. So is not that big a difference between Peregrine and Kestrel. Peregrine is right about 15 feet LWL. It's got a lot of stem overhang which doesn't count

I still prefer P over K even though with my reach Kestrel allows for a more vertical stroke and the increased skin friction is not helping me. I like the increased freeboard in rough conditions

 

[Glenn MacGrady]

A theoretical top speed difference would be one of the least important factors to me in evaluating the difference between a Hemlock Kestrel and Peregrine, or any two other similarly sized canoes. Much more important is how both feel to me -- glide, initial stability, secondary stability, turning, tracking -- paddled empty and with my usual tripping load. Weight would be more important to me than top speed.

I certainly think a 154 lb. person could trip in a Kestrel. Well, unless you carry splitting mauls, machine guns, tables, satellite dishes, and coolers full of Sapporo Space Barley beer. (You know . . . unless you're Canadian.)

 

[daveo4]

As Kim states the POTENTIAL hull speed of a displacement hull is a function of the square root of the waterline length. For general canoe lengths that isn't a lot. The wetted surface area (drag)( goes up for a longer canoe if all other dimensions are the same and that takes more horsepower ( you and your paddle) to reach that potential. I sell kayaks and canoes. I get customers who come in looking for a longer craft because they are having trouble keeping up with their friends and think that longer boats are faster. I try to explain all the parameters that go into all of this but they get longer boat. A month later most are back with the observation (complaint) that they STILL can't keep up. I can be pretty blunt when I tell them it's not the boat it's the engine! That's why racing canoes and kayaks are long AND skinny: the "long" for more potential hull and the "skinny" to bleed off wetted surface (drag). I built a racing kayak for a 105 lb woman a few years ago that was 18 feet long and 18 inches at it's maximum beam. She was fairly successful with it because it didn't have a lot of drag. Once you toss in chop or waves it really gets complicated as shorter boats will pitch (hobby horse) in early waves with shorter lengths while a longer boat has an easier motion and can maintain a higher speed. The horsepower requirement as a hull goes faster is an exponential curve which for humans is impossible to attain. An example from my past: I was senior watch officer on a 3000 ton, 378' ship. It had diesels and gas turbines. With 6000 HP (diesels) we could get 15 knots (17.25 MPH or 27.6 KPH). To double that speed we needed 36,000 HP ( two gas turbine engines). The fuel consumption was 10 times greater to get that speed.
For human powered craft, you may be able to get close to a potential hull speed but maintaining it for any length of time can be grueling.
Just my 2c.
Regards,
Capt. Dave

 

[Guest]

I owned a wonderful Kestrel for several years. I weigh 180 and take 35# of gear on trips. It worked fine. I think I was at the limit though.
Turtle

 

[Jim Dodd]

To me, calculated hull speed is insignificant, compared to what's above the waterline !
Tumblehome, rocker, hull flare, and even seat location (fore and aft, up and down) carry more importance.

But it is fun to work out the calculations.

The real test is answered with a paddle in hand !

My 2 cents worth.

Jim

 

[AlanP]

I'd like to thank you all for your guidance. I have paddled both the Kestrel and Peregrine and found the Kestrel to be for me: definitely quicker, faster, but a little 'twitchyer' which will go with experience with the canoe. I finely received the roof rack and planning to pick up my Kestrel week after next. Hope to see you all on the water.
alan