Racing Canoe

[coreym]

So I'm building a 20' long canoe. I've downloaded Delftship and have already designed what seems like a pretty good hull. However, I need some good software for analyzing the canoe's stability and ability to turn? I don't believe my free version of Delftship will do that. I would prefer freeware because it's a student organization and we certainly don't have much money!

[Rick Willoughby]

Delftship will give you stability. You want a KM of about 450mm for comfortable stability if you sit on the keel. You will get this number from the hydrostatic information.

The things that improve stability are more beam, more rocker in the keel and "V" in the bottom.

Turning ability is a function of rudder (if you have one), hull rocker, weight distribution and shape of chine in a canoe. You can work out the rudder power if it is under the hull using JavaFoil. The rate of turn is therefore complex. If you are only using paddles then the rate of turn will be a function of skill as well.

My observation of inexperienced canoeists is that tracking ability is more important than turning ability.

Rick W.

[Martijn_vE]

John Winters has developed a fairly simple method that will give a good indication of the tracking capability. I believe it's called "cantrac"

I have his PDF book called "the shape of the canoe" which deals with all kinds of design aspect and is certainly worth reading. It also comes with a CD that has the Cantrac method implemented in Excel.

[coreym]

Alright Rick, I found the KM value you spoke of after migrating over to Freeship. For my design load (2 people @ 170 lbs each and 1 concrete canoe @ 170 lbs) I attained a KMt value of approximately .90 ft. What are the implications of this?

[coreym]

Originally Posted by Martijn_vE

John Winters has developed a fairly simple method that will give a good indication of the tracking capability. I believe it's called "cantrac"

I have his PDF book called "the shape of the canoe" which deals with all kinds of design aspect and is certainly worth reading. It also comes with a CD that has the Cantrac method implemented in Excel.

Ooh! I'm totaly a John Winters fan! Is that PDF book e-mailable??? I've read parts 1-3 dealing with frictional and residual resistance, what more is there to a canoe! Kidding

[Rick Willoughby]

Originally Posted by coreym

Alright Rick, I found the KM value you spoke of after migrating over to Freeship. For my design load (2 people @ 170 lbs each and 1 concrete canoe @ 170 lbs) I attained a KMt value of approximately .90 ft. What are the implications of this?

If it was a lightweight canoe you would need good technique to keep it stable. Being 170lb, with a lot of weight down low in the concrete on the bottom of the hull, might make it stable enough to actually operate. I would be looking for KMt more like 1.5ft to make it practical if it was a more normal weight.

You want to have your Centre of Gravity lower than the KMt to be stable. When I sit flat on the floor in a recumbent position my CoG is 11" above the floor. I designed the boat in the attached video to have a KMt of 13". It has a WL beam of 17" and a maximum beam of 20". It is OK once seated but I have to have it stabilised to get on board. You will see racing kayaks mounted when grounded and push off from the beach with the paddle. They rely on the paddle for stability. Very twitchy and a lot of skill involved.

So you need to work out where your CoG will end up to determine if it stable. I have not made a concrete boat but I gueess one advantage is having a lot of the hull weight low down.

If you like I can tell you what sort of performance you can get from the boat if you post the model.

Rick W.

[coreym]

Feel free to grace me with whatever knowledge you may have as I've only been using this software for about a day now. Keep in mind that this canoe is not allowed to have a rudder and must be capable of competing in races such as 2 and 4 person long distance (there back there back tight 180 degree turns), 2 and 4 person slalom (tight >90 degree turns), and sprint. Pretty much it needs to be great at everything, turning, tracking, stability, speed. I know, they all fight each other. I managed to increase the KM a tad by creating sharper chines and pulling them out wider, but I don't think I can pull them out any more. And my L/B ratio is about as low as I want it to be. Has anybody attempted to dimple the front end of a canoe to reduce frictional resistance?

[Rick Willoughby]

Corey
I cannot open that file. I have FreeShip 2.6. Also tried with Delftship. Are you able to open in Delftship and post that version.

Rick W.

[coreym]

I have freeship 2.77. I can't seem to convert the file so that it's compatible with Delftship. I'll keep working on it.

[Martijn_vE]

Originally Posted by coreym

Ooh! I'm totaly a John Winters fan! Is that PDF book e-mailable??? I've read parts 1-3 dealing with frictional and residual resistance, what more is there to a canoe! Kidding

It's not really emailable (approx 20 mB). Besides, it wouldn't be really fair to John, especially if you're such a big fan of him . I'm not sure whether he sells the book, but if he does it's good value. I suggest you just drop him an email, and maybe he'll even give you some advice too.

If you're designing a racing canoe there's a great deal more to it than just the resistance. He managed to write 78 pages on the subject!

[Rick Willoughby]

Corey
I found 2.77 and opened your file.

I checked the performance of your hull and compared it with a Godzilla hull having a length and stability constraint optimised for 6kts. The attached chart shows the comparison.

The power requirement is based on 65% efficiency. This is possible with good paddlers. If you take a couple of reasonably fit young adult males you would expect them to sustain 200W each for say 1/2 an hour. Your hull will hold around 5.5kts with this power. The Godzilla hull will get to about 6.3kts for the same power.

The KMt for the Godzilla hull is almost 1.5ft. So this would be acceptable. I think the 1ft you have would be borderline.

Rick W.

[Chris Ostlind]

Corey,

Here's a starting point for you with all the basic parameters for a fast, 20' canoe that will have good stability, track like a train with very good speed under paddle by two, let's say... Intermediate, paddlers and it will turn on a relative dime (for a 20 footer) The turning can be enhanced with a slight heel so that you bring the hulls curvature into play to assist the process.

There could be a faster boat for straight line speed, but it will give away stability and turning to get the speed. Obviously, a boat of that type would favor very experienced paddlers to get the most from the design. Since you didn't indicate your level of experience, I opted for a milder version of a fast boat and got all around handling and forgiveness instead. If you can't stay upright, you can't win most races.

This is a multichine design from which you can extrapolate curves to produce a smooth hulled variant.

The .fbm file as well as the hydro file is attached

[coreym]

Thanks Chris,
I apologize for taking so long to reply, I was out of town this weekend. I modified your hull so that it conformed to requirements, made a couple other minor changes, and then made a comparison between it and my design. Right now my problem is that I can't get Freeship to display my resistance when I use the KAPER method. It draws the graphs and displays the x values along the x axis, but no y values. I've posted the spreadsheet comparing the important factors of the hulls (I've actually made some changes to my own design and also done a couple transforms just to see the effects). Let me know what you think.

[Chris Ostlind]

I hope it can help you, Corey. I pulled it together from a series of other canoes I have done in the past which had characteristics that I found positive for what you had described for your event. Please, just use it as a jumping off point, as you have indicated... something that has a set of parameters which will, perhaps, get you where you want to go with your own design.

I tend to like asymmetrical hulls in canoes with enhanced rocker at both ends for turning response, but more so up front. The turn of the bilge will be important as to the stability manners of the hull when paddled. I like a little bit of flare forward to deflect any wave patterns and keep them from reaching up and over the gunnels amidships. The entry is slender and gradual with the overall Cp balanced at the .53 -.54 point for efficient low speed capability. I wouldn't take it higher for a boat that weighs this much as it will kill you to hold the speed there for any distance.

I'll get a chance to look at your attachment later this evening as I'm in the middle of banging-out a plan set right now and have to stick with it.

Chris

[coreym]

Migrated back from Freeship 2.77 or whatever it is I'm using back to 2.6 - my resistance calcs now work and I've included that in the spreadsheet. I should mention that none of the races in this competition are too long, maybe 5 or 10 minutes in duration. How does one go about building the power vs. speed graph that Rick put together? About how much power per person could I expect for let's say 10 minutes for an intermediate paddler?