Concerns replacing a combing-hung seat with a hull-attached seat

Hello all, I’ve appreciated past counsel from this discussion board, and have another question for folks. I’m currently refurbishing a Northwest Seascape Expedition . . . the thing is a beauty in the water but a beast on land. At 6’8", I’d have a much better fit (and rudder usage if needed) if I detached the combing-hung seat and replaced it with a carved minicell seat a couple inches farther back. I have other kayaks with hull-attached seats, and I don’t think there are major hull layup differences, so am assuming this wouldn’t be an issue from a hull strength perspective (I weigh about 285 pounds (130 kg)). Appreciate any thoughts. - Stephen

pictures? Combing legs go to the bottom of the hull or you’re saying seat is part of structure between deck and hull bottom?

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The seat “hangs” down as a U from the combing, and doesn’t come into direct contact anywhere with the hull. However, three pieces of minicelll covering about 1/3rd of the butt area are positioned under each butt cheek and along the back. Hopefully that makes sense.

on Current Designs boats the combing has legs say 4" wide on each side which are formed when the make the combing. Legs are part of the combing all one piece. ABS seat is pop riveted to legs and seat bottom contacts hull. Seat bottom is sitting in a blob of silicone with a wedge if minicell in front.

So combing legs and ABS seat do support combing and deck around it.

The minicell your seat is on may be bonded to seat and hull. What is seat made of now?

So at worst you could add legs from hull bottom to underside of combing. You can make fiberglass legs if need be to support combing. With your weight and height you probably need some support. I wouldn’t want to sit on my combing without supports. Legs are easy to make if need be.

I have put wide base seat option CD offers on most of my kayaks and moved them backwards an inch. The wide base seat is 17" wide. Standard seat is 16" wide. Even though cockpit combing is 16" wide on some just below the combing / deck it flares out wider. More comfortable for me and lets my hip have movement easier.

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My guess is that seat structure does support the combing, since any weight applied onto the edge of the combing will be channeled down to the seat pan and onto the hull through those minicell pads. I’d be concerned about cracking the combing or deck if you press down on it (you’re a heavy guy) unless you add combing legs as paddledog52 described.


I have bought and re-sold almost 3 Dz used kayaks in the last few years and on several I have had to make small repairs but I have never had to replace a seat with a totally different kind. So if I were doing that for someone the 1st thing I’d do is call the company that makes the kayak and give them the details of what you want to do and why, and see if there is any good tips they’d give you before you commit to the project. Such a swap probably cannot be reversed, so you need to be totally sure it is going to work and not make a larger problem then the one you have now.

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My only experience with this question is with a thermoformed hull, so it may not be relevant. I removed the seat from where it was hung, placed a piece of 1/4" closed cell foam in the bottom of the hull, and placed the original seat on top of that. I added foam on the sides to prevent the seat from sliding back and forth too much. (I actually like it to slide a bit to change my position.)

One thing to consider with this is what the bottom of the kayak is supposed to do if you run over something. Is it supposed to flex upward to prevent cracking? In my case, I ran over a submerged tree stump and cracked the bottom right under the seat. My theory is that my weight in the seat prevented the bottom from flexing upward, plus I discovered a protruding plastic screw on the bottom of the seat. I don’t actually know the cause of the crack, but I think it’s possible it might not have happened if I had left the seat on its hanger. Just something to think about.

I’ve removed the seats from three kayaks and placed them on a sheet of foam and pushed them all the way back to gain length and depth in the cockpit. Made a big difference in comfort and ease of entry and exit. You do need some sort of support under your thighs/knees if you do this, but that’s not hard to do.

company is probably not going to tell you anything for a change due to liability reasons. also I doubt they could care less unless selling you a part.

I have a hung seat on a racing boat, a Westside wave.

That seat is not built up enough to be structural. The flex in it will do nothing to stop any hull flexing.

It looks like the object of a hung seat is relieve strain on that section of the bottom. It will spread that load further away, so as to lessen damage by hitting some structure.

If you replace it use a seat that also keeps the load dispersed. Some seats are built to fit your boat from freeboard to freeboard, use one of those.

Seats are, however, put in a certain place for a reason. That is the center of gravity. I don’t know your particular boat, but a couple of inches could cause the bow to ride higher and/or the stern to squat. If you use the boat for intense play, then try it before gluing anything into place, it might not handle the same.

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Agree. Especially check for pressure points. Minicell foam sounds like a safe choice, but 285 lbs could be a concern. Also depends on the material of the hull. I consider thermoformed plastic risky but not impossible. What about fiberglass?

It is so hard to say about fibreglass boats. There are so many ways and types of materials that have been used over the years.

If it is chopped glass, the free boards are often weaker and if they were made with polyester resin they would not be entirely waterproof on the inside. Vinyl ester is more waterproof, but has on;y been used for 20 or so years.

Better made boats are made with fibreglass cloth which will be the same strength throughout. This too is fairly recent and restoring an old and heavy boat usually means it was chopped glass with polyester.

It would probably be best to see if you could re-hang the seat a little further back.

I’ve never seen a comb with legs, but all of my kayaks have coamings around their cockpits. :stuck_out_tongue_winking_eye:

I’ve removed hung fiberglass seats from several boats and replaced them with foam seats glued to the hull. Despite lots of landing on stone-filled beaches and playing in rock gardens, we’ve never had any problems with hull cracks. The foam pads under hung seats are primarily there to keep the seat from flexing side-to-side, not so much to support the hull. The thing most likely to encourage hull cracking is fiberglass bulkheads, which create stiff spots in an otherwise flexible hull. I’ve seen a few boats with fiberglass or plastic bulkheads that have an inch or so of foam at the bottom to mitigate the problem. Full foam bulkheads are obviously less of an issue.

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all my CD boats have legs which are formed when the make the combing piece. It is then glassed to the hull at the bottom of the leg.

Google Photos

goes down on sides of seat.

Eddyline has similar construction.

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Useful information, thank you. So am I right to think that the bottom needs to flex when riding over an obstacle, and that a heavy person sitting directly on the bottom could prevent flexing?

A person who repairs fiberglass kayaks once suggested that I could add a layer of fiberglass in the bottom of the cockpit area for reinforcement. (Still referring to thermoformed kayak.) I’ve also been told that the pressure of the water against the bottom of the kayak provides the necessary stiffness for a thin ABS hull. True? Even Eddylines have surprisingly thin bottoms.

I cut out the hung seat from a Nigel Dennis Explorer and installed a mini cell seat to gain some room. I didn’t notice any change in rigidity.

  • Mike

I think Eddyline’s hard chines give more stiffness than a rounded thermoform hull of the same thickness.
No data, just an intuitive thought.

I guess it would depend on pressure point.

Most hardchined boats have a defined V of a keel. That would concentrate any pressure from a structure hit to the apex of that V.

Round hulls spreads that impact a bit.

It still takes a lot of bad luck to damage a kayak hull on the water.

I’ve read exactly that. But the stiffness is along the sides. If you turn an Eddyline over you will be surprised at how soft the bottom is, compared to other materials.

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The pressure of the water does not add stiffness to a hull. False.

In the canoe world some hulls are designed to flex when going over something like a submerged stump. The royalex or tformex composites are happy to flex. So is my carbon/kevlar Bell with no foam core. I also had a Souris River with a “flexible rib system” where the kevlar skin with epoxy resin could flex a lot. But my lightweight carbon Rapidfire would just crack and my canoes with foam cores get dents in the cores from submerged stuff. I’d expect a thermoformed boat to be pretty happy to flex going over a stump.