For a paddler sitting on a simple rectangular frame cane or webbed seat with legs extended forward, where would you judge their body mass to be centered relative to the seat?
I realize that this might very with body composition and leg length, but is there a rule of thumb? I am thinking the weight center would be an inch or so in front of the front seat frame cross member.
Seen those side-by side ATVs? That’s
the solution for friendly paddling pairs.
For what it is worth
We have several tandems, and trying to visualize where most of my body mass is, I am guessing it would be not that far forward, but more over the front of the seat.
Jack L
my “guess” would be …
… where the pressure on your butt is the greatest is about the CG for a body’s mass … just a guess though .
There are many other weight items often placed in a tandem canoe that contribute to the the canoe’s overall trim ballance . How these items are located in the canoe have effect on the canoe’s trim also . These weight items most likely will change from one outing to the next as well (more stuff , less stuff) .
Are you trying to determine “only” where the paddlers CG is on the seat . I’m pretty sure you know about the factors that affect canoe trim and the things I said you already know about . Are you attempting to refine it to the inch as if nothing will ever change from there after ??
Just curious about your question and why you ask it . Why are you asking that question and referencing seat placement ??
Seriously, I think the mass center
when sitting with legs out will be somewhat ahead of the front of the seat. Obviously for those with long legs and big feet, like me, the mass center will be farther forward. In kayaks, I often have to move the seat back to get them trimmed right.
Our tandem is now set up so that it rides a little bow light when we are kneeling, and about level when we are sitting.
I am going to set up a large solo
to be paddled as a light tandem. I anticipate that the heaviest cargo it will carry as a tandem will probably be a couple of water bottles.
Front seat placement will be dictated by comfort for the bow paddler. Since the boat was designed as a solo, it will be a little tight in front, but probably no worse than a Wenonah Minnesota III in that regard. I will place the front seat so that someone of my size (5’ 11", 170 lbs) can stretch their legs out and use the front float tank as a impromptu foot brace.
The question is then where to position the rear seat. I would like to trim it neutral for a bow paddler of my size. I doubt that the boat would be very seaworthy with a load much greater than 340-350 lbs. I may be paddling it with a kid in the bow now and again, and it would be OK to be a bit bow light in those instances
I am thinking that for the average seated paddler, sitting with knees bent and centered comfortably on a rectangular web seat, the body center of gravity is probably close to the front edge of the seat frame. For a paddler sitting with legs extended forward on a foot brace, for example, the body mass center might be an inch or so forward of that, but that is just a guess.
be careful
"front float tank as a impromptu foot brace"
We have had some canoes in Wabakimi all summer. They cant be flown out till the end of the season for repairs.
Someone put their foot through the float tank using it as a foot brace.
But as you will be day paddling not repairs not likely a problem.
How about sliding seats?
Thanks
for the warning. This canoe is a Mad River and it appears to have a big, fairly solid foam block for flotation, walled off with Kevlar, so I am probably OK there.
I thought about a sliding seat but decided against it to save weight and for the sake of simplicity. I will probably mount a kneeling thwart near amidships so that the boat can still be used as a solo.
Got two bathroom scales?
Sit on one and put your feet on the other. A little simple math will tell you exactly.
With youngsters…
– Last Updated: Sep-18-10 2:53 PM EST –
We (daughter and I) have spent an entire season working on ways to make this work well, and for us, with a SMALL bow paddler (youngster), what you're doing works WAY better than going with a dedicated tandem. The narrow paddling station is just great... and by getting the stern station just aft of the normal solo position, you retain most of the advantages of soloing (including reasonable control of the bows).
I don't see any advantage to an adjustable bow station: you don't want to get the weight any further forward with a youngster, as you've generally NOT got the volume near the bows (or the bow sheer) to ride over waves with weight a long way forward... and trimming the hull would then mean you moving further aft than is ideal in a solo hull (although in an swede form hull, that might be slightly less critical).
Our Flashfire is symetrical, so we can paddle it reversed with a saddle under each thwart... which means I retain the option of paddling it from the factory seat on the few occasions I get to paddle alone. In your situation (asymetrical hull) I'd be inclined to remove the stock seat completely and fit a saddle / pedestal in a manner that allows it to be positioned forward or aft as trim requires.
FWIW, Northwater offer an adjustable saddle that might give you some ideas: see http://www.northwater.com/html/products/canoeing/Canoe%20subdirectory/Adjustable-Saddle.html
Seat Placement
Pretty simple to figure the math of a teeter totter. weight times distance to center for each paddler, making sure the largest paddler is always in the stern.
I’ve used 4" in front of the seat edge for kneelers, at the seat edge for sitters in symmetrical hulls. It has worked pretty well for Bell. If folks choose to, shamefully, sit in the hulls the stern gets skegged a little.
It gets difficult with asymmetrical hulls;, use the widest point, generally 6-12 in aft of center, as “working center.
It gets more difficult with differential rocker, because even when the center is adjusted to compensate for Swede-form the hull will equalize volume for and aft, so seats need be moved aft a little more to preserve the rocker difference.
I’m currently trying to figure where to put the seats in my new Pb Ohneka; radically delta shaped with 3” bow, 1.5" stern rocker. The short answer is further aft than I thought.
Eric_Nyre’s method?
– Last Updated: Sep-18-10 3:05 PM EST –
Re: complicated hull shapes (like the Ohneka)...
1. Is the idea still to get the hull trimmed flat at normal cruising pace?
2. Is there any reason why Eric_Nyre's method (above: quart of water in the bottom) wouldn't work?
Just wondering :)
Good question
With asymmetrical hulls I have not been sure that the deepest part of the bilge will necessarily be at the center of the boat when the boat is optimally trimmed.
I don’t often have a tandem partner but I volunteer for trips in which there is sometimes an even and sometimes an odd number of participants. It helps to have a canoe that can be paddled either tandem or solo in these instances.
Of course, one never knows what the size of one’s partner will be in these instances. For this boat they would probably generally be smaller than me but I would like to be able to paddle it with someone up to my size in the bow.
That 2# water
– Last Updated: Sep-19-10 8:03 AM EST –
In a radically differentially rockered hull just where should that quart if water pool? Certainly not at center. Yost claims C of volume is 8" aft center for Ohneka but that the seats need be further aft to retain intended rocker.
I'll be buying salt bags to represent Beth, and we'll use a quart of water too, but it's a conundrum.
OK that fits
And Marc Ornstein says he places the front seat edge 4" abaft of center on his solo canoes. Of course, he favors kneeling as well.
I may compromise and consider the weight center to be 2" forward of the seat front edge.