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Canoe Seat Advice

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Installing the seats in my canoe, and looking for advice. This canoe is Gil Gilpatricks Wabnaki design. I've made the traditional flat canoe seats out of black walnut, 7/8 thick by 1 3/4 frame, I think this is sturdy enough for my 215# rear end. I weaved them with plastic artificial cane. I've got them at a height of 9+ inches underneath. According to Canoe Craft by Ted Moores 9.5 to 10.5 is a good height for feet placement for kneeling. I don't expect to kneeling in this, but ya never know and my feet are a little large 13EW. Yes Bigfoot exists in East Tennessee. The seats look to high to me, but that may be due to the canoe design. I'm going to have recut the back seat hangers, which they are roughed in anyhow.

Am I ok with this seat height as far as comfort, and stability is concerned? I wanted to leave the seats level so when I go solo I can sit in the bow seat facing the stern.

Just lots on my mind concerning comfort, stability and if I'm going to brake my seats or gunnels or who knows.

Any advice on any of this is greatly welcome and appreciated.
 

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Well First I'm a fan of Ash, for seats and trim. If you are using Cherry ? I've seen more Cherry seats give way than Ash.
Cherry looks cool, but I don't believe has the same structural integrity.

Start low, you raise a seat easier than lower it.

To me Stability is #1.
If it is too high ? It isn't Stable. I paddle something else, that is.

Lastly ? Leg comfort. A Sharp edge on the seat will bite you ! A pad might work, but it will also raise seat height at a loss of Stability.

The good thing is it is all fixable, make another seat or change the height, you can do it !

Just my thoughts !

Jim
 
Agree with Jim on all counts.

A radius edge on the front of the seat frame helps with comfort, whether sitting or kneeling.

Ash, or laminated seats, will be stronger then cherry. The other place I’ve seen seats break is at the frame joint(s). How did you join them?

EDIT: Oops, black walnut I see.
 
Roy,

As you know, I also paddle a homemade Wabnaki (and also have plastic caned seats). I have them hung pretty much at 9" and level. I weigh exactly the same amount as you but I'm only 5'10" or so. I do, sometimes, kneel but usually sit.

Here's what I can tell you: the Wabnaki is a very stable canoe for me when sitting, paddling solo or tandem, loaded or empty. Unless you are much taller than me and your weight is correspondingly higher in the canoe when you sit, I don't think you will have a problem with stability with the seat height at 9" in this canoe. In some narrow, round bottom canoe, yeah. But not this canoe.

That said, don't make the drops that hide that seat bolts (and provide lateral stability) yet. Take it somewhere local and flat and give it a try. You can always lower it. When you have the height you want, make the drops. I paddled mine for three seasons without making the drops.

Best,

Al
 
I don't worry too much about seats hung from hangers. Leave them where they are, finish the boat, and paddle it. If it feels good then you're good. If it feels too tippy make another set of hangers and drop the seat. Or just add spacers to the current hangers.

Alan
 
Thanks for advice you all. Seat hangers not to much of an issue, but the seats may be a problem. What if I glue a different wood on the underside of the seats. Simple to sand finish on underside and epoxy a sturdier wood to it. That would be considered a laminate and increase the structural integrity, and maybe not add to much weight, to the seat with out completely rebuilding them. How thick and what kind of wood? I did a mortise and tenon joint with chopped strands of fiberglass mixed in the epoxy.
 

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Thanks for advice you all. Seat hangers not to much of an issue, but the seats may be a problem. What if I glue a different wood on the underside of the seats. Simple to sand finish on underside and epoxy a sturdier wood to it. That would be considered a laminate and increase the structural integrity, and maybe not add to much weight, to the seat with out completely rebuilding them. How thick and what kind of wood? I did a mortise and tenon joint with chopped strands of fiberglass mixed in the epoxy.

I think 7/8" thick walnut should be fine to support your weight. Maybe don't jump up and down on the seats with one leg.
 
I think 7/8" thick walnut should be fine to support your weight. Maybe don't jump up and down on the seats with one leg.

Not only that but the frame pieces appear to only be slightly rounded over rather than heavily rounded over and carved like some seat designs. I'd say as long as there are no knots the seat should be plenty strong.

Alan
 
If you're concerned about seat strength, you can always strip the artificial cane out, add a layer or two of glass on the bottom, and relace the seats.
The glass on the bottom will go a long way to reduce the deflections and be almost undetectable from most viewpoints.
 
One way to find out if something is strong enough is to test a sample piece and find out how much stress it will take before it fails... so in the case of the seat crossmembers possibly breaking, making another exact duplicate and then gradually putting some weight on it could be revealing. Maybe support the sample piece between two concrete blocks the right distance apart and then add weight gradually by standing on it more and more heavily. If you hear ominous cracking sounds well before half your weight is on it, it probably needs to be stronger. If it supports your entire weight, it's strong enough.

I had some similar concerns when adding pine inwales to a stripper... would the bolts running through the inwale holding the seat, break through the pine under my seated weight? Pine isn't known to be strong, it can be brittle actually, but it is light and I could save a pound or two. Anyway, just to keep the story short, a one-bolt test piece showed that one bolt supported by pine inwale could hold my entire weight... so four bolts holding my weight in the canoe should be overbuilt enough to last. I haven't had anything break in it yet but the soft pine sure does dent and gouge easily.

Engineers IIRC overbuild critical structural members to hold six times the planned carrying capacity, but that's probably going too far.

PS... I just read Stripperguy's comments on glassing the undersides... agree 100%...
 
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Lots to chew on. Looking at the Wood Data Base site, what is or are the key factors that a person needs to understand when engineering something made from wood?, such as canoe seats. Trial and error is lots of time and work. I think I'll try them out, and if they break I will build new and better. Weaving them is very time consuming. If and when they break I'll let you know.

Your all's advice and knowledge is valuable to us rookies. Thank you.
 
Looking at engineering properties, the single most important characteristic is E, the modulus of elasticity.
Knowing that and the dimensions of your beams and means of support, you can calculate the deflections for a given load and determine if the resulting stresses exceed the ultimate strength of the material.
Even without the beam calculation you can compare E for various materials and make a comparative pick.
Your seat frames would be considered simply supported should you want to look for the deflection equations.

EDIT:
To more simply characterize the beam deflections (seat frame members):
The deflections (and associated stresses) are an inverse function of the length squared (span between supports), linear function of the beam width, and a function of the height cubed.
In other words, double the span and you'll increase deflections by a factor of 4. Double the width and you'll reduce deflections by the same factor. Double the height and you'll decrease deflections by a factor of 8.And all of these relationships are linear with the modulus...

So rather than trying to find stiffer wood frame materials, you get more bang for your buck by adding some height or adding some extremely high (by comparison) modulus materials like fiberglass.
 
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7/8 of an inch thick should be plenty. When I replaced a seat on a Bell solo canoe with a seat from Ed's the Bell was 5/8 thick and the Ed's is 7/8 and the difference in stiffness is dramatic. According to stripperguy's input (which I'm too lazy to doublecheck) the extra 1/4 inch thickness makes the seat almost 3 times stiffer (275%). The height sounds good (normal) too. I usually take my shoes off (even with my petite size 11's) since you gain so much foot clearance for kneeling.
 
That's alot of math stripperguy, but I did ask. I might take a dive at trying to figure it out some day. I made a set for my Mad River, a few years ago, out of cherry. 3/4 thick by 1.5 wide. So far so good, but I do wonder if and or when they will break. Fixen to start applying poly on the inside, gunnels and thwart, so I have time to decide on the seats.

Thank you all.
 
That's alot of math stripperguy, but I did ask. I might take a dive at trying to figure it out some day. I made a set for my Mad River, a few years ago, out of cherry. 3/4 thick by 1.5 wide. So far so good, but I do wonder if and or when they will break. Fixen to start applying poly on the inside, gunnels and thwart, so I have time to decide on the seats.

Thank you all.

See, if you made your frames half as wide and twice as thick (just reorienting the parts) you would lose half the strength from the reduced width, but gain 8 times due to the increased height.
Thats a net gain of 4 times the strength for the same volume and weight of wood!!
Same materials, increased strength by 4 times, just by doing a tiny bit of math first.
 
Eh. I like what Grumpus and alsg said better, but you are right stripperguy. I've pondered on it to much, and have taken drastic measures to ensure that my, or my wife's, butt don't hit the floor. I'm going to see how this works before saying anymore. I will not be defeated, or deseated.
 
So here's a pic from 1985... I was on a lightweight kick, I had just finished a 17 ft tandem that weighed 37 lbs. Didn't even have the seats laced, finished lacing them around the campfire on the maiden voyage. I definitely went too far, MDB was all of 115 lbs back then.

ACtC-3fVv15Pm7qdCQORiDZtIcKJ10xQBTxMFTQlEoRduQBai2j4KlG_6XzAjD2qQovpLl-Esd6CbjFCGBANmMeyiCpHMYbmXneykBdwbFharqegf2RQHF8_wuyfBxvyE39KcZAPVV77jhywolIwniCbmPj7pg=w603-h882-no?authuser=0.jpg
 
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