Steve Killing’s Canoe Stability Factors

[Sweetfancymoses]

I can't quite picture the process of determining the factor by the verbal description without a drawing. I gather the factor cannot be determined by just crunching some numbers but is experimental. I understand that there can be a lot a lot of subjectivity involved in judging the primary and secondary stability of a craft. Is anyone familiar with this and do you think there is some value in it when deciding between different designs?


Method: Load the canoe to 400# (tandem) or 250# (solo) and then heel it to 15 degrees. Once in this attitude the stability is related to the distance from the center of gravity (which I set at the waterline for all canoes as a base point) and the metacenter. The metacenter is the point (usually about 12" above the waterline) where the vertical line through the center of buoyancy intersects the centerline. Once the metacenter at 15 degrees has been determined, the stability factor is simply the metacentric height in inches divided by 12.24 times 100.

Ratings:
110+ is comfortable for all novices
100 is comfortable for most paddlers
98 will be initially tender to some novices, then will become quite comfortable
92* is not comfortable to most novices.
88 is a challenging boat for some people to paddle
40-50 is the low end, a K1 racing kayak would be somewhere in that range.

Examples: [TABLE="border: 0, cellpadding: 0, width: 265"]
[TR]
[TD]Marathon 18/6[/TD]
[TD] 49[/TD]
[/TR]
[TR]
[TD]Rob Roy 13[/TD]
[TD] 71[/TD]
[/TR]
[TR]
[TD]J.G. Brown 16[/TD]
[TD] 74 [/TD]
[/TR]
[TR]
[TD]Canadienne 16[/TD]
[TD] 86 [/TD]
[/TR]
[TR]
[TD]Hiawatha 15[/TD]
[TD] 88[/TD]
[/TR]
[TR]
[TD]Huron Cruiser 15/9[/TD]
[TD] 92[/TD]
[/TR]
[TR]
[TD]Champlain 16[/TD]
[TD] 92[/TD]
[/TR]
[TR]
[TD]Solo Day-Tripper 17[/TD]
[TD] 92[/TD]
[/TR]
[TR]
[TD]Red Bird 17/6[/TD]
[TD] 92[/TD]
[/TR]
[TR]
[TD]Freedom 15/3 & 16/2[/TD]
[TD] 95[/TD]
[/TR]
[TR]
[TD]Cottage Cruising 15/6[/TD]
[TD] 97[/TD]
[/TR]
[TR]
[TD]Freedom 17[/TD]
[TD] 98[/TD]
[/TR]
[TR]
[TD]Bobs Special 15 [/TD]
[TD]100[/TD]
[/TR]
[TR]
[TD]Nomad 17 [/TD]
[TD]102[/TD]
[/TR]
[TR]
[TD]Prospector 16 [/TD]
[TD]103[/TD]
[/TR]
[TR]
[TD]Freedom 15 [/TD]
[TD]104[/TD]
[/TR]
[TR]
[TD]Ranger 15 [/TD]
[TD]104[/TD]
[/TR]
[TR]
[TD]Chaa Creek 19/9 [/TD]
[TD]105[/TD]
[/TR]
[TR]
[TD]Freedom 17/9 [/TD]
[TD]111[/TD]
[/TR]
[/TABLE]

 

[Jim Dodd]

Those are all Bear Mountain designs.

There are a lot more things to consider than dead weight in the bottom of a canoe !

A Paddlers stature needs to be figured in, and seat height makes a tremendous difference !

I'd consider that a"Ball Park Chart !"

Jim

 

[memaquay]

Too true Jim, I have found the twitchiest of hulls gets pretty solid with a lower seat or a kneeling position.

 

[gumpus]

I don't understand it but the numbers seem a little strange to me as an engineer. So 100 is a Bob which had a universally friendly reputation but drop to 98 and it makes a big difference and you have a sensitive boat. But then there are designs that are 10-20 points lower that can still be paddled by humans? It's not intuitive.

I owned a Tripper 17 and it's a hot boat. It has a narrow waterline width and the shallow vee means you really feel it when the dog shifts their weight. Tripper 17 is at least twice as sensitive to dog movement as a Bell Northstar in my experience. The description for the 17 sounds right (feels tender initially but then you get used to it) but the score seems too close to a Bob. I know a canoe dealer that had a 17/9 and called it a fine family boat so that also passes a sanity test. But then something with a score in the 80's or even 70's would seem to be like a dugout telephone pole. I don't understand the sensitivity of the ratings.

 

[Alan Gage]

When I started designing some of my own boats this stuff drove me crazy until I'd actually built and paddled a couple for reference. You can calculate all these wonderful numbers about hull performance but how do they translate into real life? I'm afraid I don't have any great words of wisdom other than paddle lots of different boats.

Alan

 

[memaquay]

Alan, where would you rate J. Winter's Barracuda? I found that fairly twitchy till I lowered the seat down pretty low.

 

[Guest]

Seat height absolutely makes a difference, even an additional inch up or down is very noticeable. Beyond seat height I have a personal two-part stability test for solo canoe preference.

Can I turn my head and torso to look 180 degrees behind me without feeling overly twitchy?

Can I reach behind the seat, retrieve a day bag or small cooler and swing it one-handed out beyond the gunwales to set on the floor in front of me without nearly swimming?

Neither of those actions is conducive to laying on quick brace.

 

[gumpus]

When I started designing some of my own boats this stuff drove me crazy until I'd actually built and paddled a couple for reference. You can calculate all these wonderful numbers about hull performance but how do they translate into real life? I'm afraid I don't have any great words of wisdom other than paddle lots of different boats.

Alan

I was lucky to trade a couple of emails with John Winters a couple of years ago when I had a couple of questions that he was kind enough to answer. He mentioned that he once designed a canoe that should have been very hot but when built it did not perform as the numbers predicted. Maybe we're lucky that there is still knowledge to be gained so still room for variety and experimentation in canoe design. In the automotive world there was a landmark technical paper that determined that the ideal cylinder size (considering emissions, heat loss, flame travel, friction and all kinds of good stuff) is 500cc with specific bore and stroke dimensions so now we get 2.0l 4- cylinder engines, 3.0l V6's and 4.0l V8's in many German engines. Efficient and effective but kind of boring.

 

[Alan Gage]

Alan, where would you rate J. Winter's Barracuda? I found that fairly twitchy till I lowered the seat down pretty low.

I was surprised at how stable the Barracuda is, not what I was expecting. My seat is about 6" off the floor if I remember right. I find it to be a very enjoyable day tripping boat with the dog (30 pounds).

I'd rate it a little under a Bell Magic in terms of stability. And I'd rate the Magic a little under the Kite/Osprey. And I'd rate all of those boats leagues above a USCA C1. My AGX is somewhere in the middle. http://www.canoetripping.net/forums/forum/general-paddling-discussions/diy/19929-x-canoe-build

Alan