Are canoe thwarts loaded in compression?

Can an added center seat act as a thwart? Can I remove the stern thwart after adding the center seat. This is a 16" Old Town camper model

Thwarts etc

– Last Updated: Jun-30-12 11:15 AM EST –

Thwarts are compression loaded, witnessed by the spreader bar we place in the boat to fit them.

Wood, aluminum and vinyl rails come out of the box straight. Aluminum can be preformed to the hull's shape but usually isn't, wood and vinyl cannot. All three want to return to their previous, straight, shape when the spreader bar is removed. So thwarts are generally in compression. The newish, integral, composite rails tend to hold the laminate to the mold's top edge shape, hence the thwarts can install without load, if the mold didn't warp.

Seats are usually much less useful because the seat drop acts as a hinge. In lightweight hulls we often place a thwart close behind bow seats to reduce the tendency of the seat to "close/ collapse" the rails,

While a Camper is an unlikely conversion to solo, a center seat should be mounted ~ 6" aft of center to trim the hull, I'd leave the third thwart in place to resist the compression occasioned by loading the l

Shade Tree Canoe Engineering
The added center will be the third seat. Will making the horizontal members of the added seat long enough to be in contact with the skin of the boat below the gunwhale help with compression or just place potentially damaging forces on the skin? Also, will slightly increasing the center width/beam of the boat increase the rocker? Thanks for answering dumb questions,I would rather ask them here than trash the family boat.


– Last Updated: Jun-28-12 5:32 AM EST –

The center thwart in the Camper is close to neutral, loading in tension when the ends are lifted and compresion when the center is lifted. Removing that thwart will not result in a great change of hull shape. But it will make the hull a little less stiff.
I think you could replace the thwart with a center seat without any negative consequences. I'd put the seat 6" behind the thwart location in case you do solo from it. And I'd make the center thwart removable. The Camper is a lot easier to carry with the center thwart.

Don’t do that

– Last Updated: Jun-29-12 11:26 AM EST –

You very much do not want the thwart ends contacting the hull. This leads to fracture in composite hulls and compression in RX hulls, which don't matter much anyway.

How does one engage a smiley face? I'm trying to be humorous?

The perfect solution is to thumbnail the thwarts so they are always stressed in both compression and when spread but never reach the hull. Funny, no Mfgs do that, except those who plexus their thwarts to Integral rails. As I remember, Lotus and BlackHawk thumbnailed their thwarts; both long gone, but surely not for that reason.

Very serious that any solo center seat needs be 4.5 " aft of longitudinal, waterline, center, which usually placed the bore holes 6" aft of same. To do otherwise pitched the hull bow down, resulting in a horrid paddling experience.

A better choice for tandems, particularly wide tandems like Camper is to put that third seat where the third thwart is located. The hull is narrower at the solo paddling station, all good, and the center carry yoke is retained for carries, or On portage, as NY and Minnesota divide the same chore up.

Thanks for all your help
I will add the third/center seat 6" aft of center and possibly add an additional thwart behind the bow seat if I perceive any flex.

What OT does…
…for the center seat in the Osprey is they truss the seat cross-members with a metal angle-brace. It seems this might minimize the hull flexing for lack of a thwart fixed to the gun’l.

Bird’s-eye photo shows the angled strap locations - although the 2d aspect doesn’t give you a lot of detail.

I have no idea if this reduces the flex enough for your needs (or mine either, FTM), but it’s worth considering. I agree with Charlie that the camper isn’t much of a choice for a tandem to be soloed - if that’s what you have in mind. I also know that three adults in an OT Camper is pushing the limits for reasonable handling.

I’m not arguing with Charlie,I know boats fresh out of the mould are spread to install thwarts and seat,BUT I have replaced seats,thwarts,lenghtened thwarts and shortened thwarts on duzzens of used boats. Some moved in when thwarts and seat were removed,some moved out and some just sat there and said “you talkin’ to me?”. Royelex and composite hulls.


I’ve switched out a few aluminum ones
for wooden replacements, and had only 1 that had maybe an inch of compression. Maybe they had more when new.

I’d suggest trying a reverse mode by paddling from the bow seat, and putting some weight in the stern(now the bow) to trim.

Changing the standard seat to a cane contour model will drop the center of gravity a little bit, and that will help overall. You would also be further from the wide center of the Camper, and have better paddling access to the water. This is less drastic than a new center seat, and easier, and maybe better, depending on what you want to do.

Good luck!

This is an extended family boat…
and the center seat is for a third paddler. However I will end up paddling alone at some point. I realize this boat is a dog for solo. We typically paddle on a small lake or a slow, flat but very twisty meandering river. Whoever is in the bow needs to know how to do a draw or we are nose in to the willows.

Next Question:

The boat oilcans on the bottom in the middle. Is this just the nature of a fat Royalex recreational canoe? How does it affect performance? Is there anything that I can do about it?

Oilcanning can be a problem.
It is inherent to some composition and design models.

It affects performance negatively, especially if you are in a race. It does not inspire confidence.

Get used to it, or get rid of the paddling craft.

Another center seat option:

Happy paddlin!

Center seat and thwart
My first real canoe, a Royalex Mad River Explorer, had a center thwart. To paddle solo and have a third seat for my kids, I added a wide cane seat about six inches behind center. Of course, that was too close to the center thwart, so I shortened the center thwart and moved it forward about a foot.

The combination of the center seat and somewhat moved thwart is still going good after almost 35 years. I think it actually strengthened the center of the canoe.

For portaging, I made a clamp on portage thwart to put in the center position.

Camper oil-canning…
Nature of the beast. Ignore it and realize that it excels in extremely shallow rivers that are flat and meandering. If and when you move up to a more performance-oriented canoe, you will see less or no oil-canning.

My experience has been exactly the same.