The bow seat in my Nova Craft Prospector 16 broke on the back strip of wood yesterday. See pix:
http://community.webshots.com/album/564801888rDTsec
My bow paddler is a large person, about 250 lbs. We were sitting quietly in the shallows when it happened, not even moving.
I'm guessing the bow paddler's weight probably caused this.
Getting a replacement seat is not an issue; a new seat is about $34 plus S&H from the factory, and that seems entirely reasonable to me. Also, I am not the original owner, so it is not under warranty anymore.
Here's my question: once I replace the seat (it's a laced seat), will this happen again with a heavy bow paddler? (I'm kind of assuming it will.)
If I wanted to have a heavy bow paddler in this boat, would I have to replace the seats with something like webbed seats (with no little lacing holes in the wood to weaken it)?
Suggestions? My bow paddler felt pretty badly about this. She is so enthusiastic about learning to tandem with me, and this was a great reason to get her outdoors and active.
Handling has to be a problem with
the weight up front. Teach her how to paddle in the rear seat.
That’s an option - how about kevlar
but switching spots as paddlers was not what I'm looking for.
How about reinforcing with kevlar?
Does anyone know if kevlar tape were to be epoxied to the bottom of the seat along the strip of wood, if that would help?
What kind of surface prep would be needed for good adherence?
seat options
http://www.edscanoe.com/canoeseats.html
Maybe this one in web:
http://www.edscanoe.com/exduse.html
yea , that’s what I was thinking …
… the stronger seat …
I bought
the extra heavy seat or the center seat I am installing in my tandem. It is VERY strong…
Another option, put a piece of aluminum bar stock under a regular seat to support the wood.
If you examine the seat that broke, you
will almost certainly find a swirl or irregularity in the grain of the ash. If the ash crosspiece in a seat has straight grain running linearly from side to side, it is not going to break.
Occasionally a seat will break where the screw goes through to the gunwale. This is usually because the hole was drilled too close to the end, but even properly drilled holes are always closer than would be desirable. With ash, it usually is not a problem, but with lighter woods, like the spruce thwarts I make for my boats to shave off a pound or so, it is a good idea to use epoxy to place some fiberglass slips over the end of the crosspiece and across the top and bottom where the screw hole will go.
Don’t think about Kevlar for that type of reinforcement. Ordinary E-glass is easier to work with and more compatible with the overall flexibility of the wood. But again, ash with good grain should NOT break.
don’t ya
love guys who know their stuff…
Good point. I weigh 230 and
my cane seats don’t break.
First the damage,
then the event.
I would bet $100 “someone” put a knee or foot on that seat when climbing over. They may not have even heard the little crunch. Damage was done. Just a matter of time until everything splits up. Have seen many of these trashed. Knee through the middle works great too.
Get at least a heavy nylon webbed seat. That other crap is for nostalgia buffs.
Just replace the seat with
another Nova Craft seat Ness.
As for the "nostalga crap", the NC seats are strong, comfortable, and great looking. I think that you should have matching seats in a tandem.
I agree with the assessments that suggest either a defect in the wood or having previously stressed in a small area. The damage could have been lurking for years. And the greater width of the bow seat means more flexing than the stern.
Epoxying a "splint" to the bottom of the new seat is an option. More wood = more beef = less flexing.
Using a piece of aluminum bar stock is another good idea. Even a 1/8" x 3/4" piece should do the trick. If carefully installed it should be unobtrusive.
I'll bet N.T. can come up with an even better solution.
Jim
Suggestion
What I did that seems to be working good for the same type seat.
Put a piece of high density gray foam under the wood portion in the center of it.
We used a piece about four inches square and wedged it under to try it, and then when we found that it was going to work, we glued it to the under side of the wood. We didn’t glue it to the bottom of the canoe just in case we wanted to take it out some time.
We just put ours under the front piece of wood, but you could put a longer piece and support both the front and rear.
Cheers,
JackL
Just glue it.
I would just glue the break with thickened epoxy and be done with it. It probably won’t break there again.
Repair with Elmers
Elmers wood glue creates a stronger bond than original wood.
Then loose some dang wieght for rice cakes. There are clinics for that.
“Zen” that wasn’t very nice
Ness can’t very well tell her friend to lose weight so she can paddle. Some people might be able to say that, but not ness. She’s too nice. She’ll just fix her boat and figure out how to make the seat stronger for her friend. That’s what this thread is about.
Sorry, ness, I should have looked at
the picture before responding. All those drilled holes would weaken even ash. They should have left a broader wood flange outboard of where the lines of holes were drilled. I would condsider replacing the seat with an undrilled ash frame seat having polypropylene webbing. (Nylon is not much used for webbing because it absorbs water and temporarily stretches, relaxes.)
Another possible problem with drilling ash, or cherry, or any wood for seat lacing is that rot may occur under the lacing where water tends to persist. But, just looking at your picture, I think the seat builder was “pushing it” by not leaving enough wood around the lines of drill holes.
g2d
Your analysis is the same as mine. I was there when the break occurred and I looked at it closely.
I also suggested a webbed seat rather than lace. But, there is the asthetics issue. That's why I mentioned the possibility of Kevlar tape epoxied to the underside.
I'm no great laminate engineer. I see you suggested fiberglass instead. Do you think it would add enough extra strength to a new laced seat? If so, is any surface prep required beyond sanding off the finish? And, how many layers? Or maybe a cloth tape epoxied to the underside isn't really a good idea.
Jackl mentioned a minicell pillar. But, there is a penalty to be paid there when transitioning back and forth between sitting and kneeling.
Under-seat bracing
Kevlar should work. The initial downward (bending) force would put the Kevlar under tension, where it excells.
Carbon fiber might work too, as it would add stiffness to the ash, reducing the flexing/bending.
E-glass would work because it is stiffer than Kevlar, and not too bad in tension (but not as good as Kevlar).
I still think a discreetly-sized piece of 6061 aluminum bowed and bolted to the drops will solve any future problems.
And yes, nylon lace does stretch, but Nova Craft uses a LOT of lace which minimizes the stretch effect. Their seats are aestetically pleasing and comfortable (for their type - don't get me started).
Jim
BTW: When I built my "hammock" seat for teh Magic I laminated three layers of 1/4 oak, all 1-1/2" wide. I was concerned about my weight (substantially greater than Ness' friend) and the weakening effect of holes. So far, so good.)
Didn’t know they were using Nylon.
With my old eyes, it could have been rawhide.
I would go with glass rather than Kevlar, partly because the “stiffness” parameters of glass are more similar to those of the wood they’re trying to reinforce. Note that, after some failed trials, Kevlar is almost never used to reinforce wood core paddles like those of Mitchell. Glass or carbon are used, but not Kevlar, even though it is perhaps a bit lighter. I present that observation as a suggestion that Kevlar is not the best for reinforcing a wood beam member.
I think you’re probably right Jim
A piece of aluminum bolted to the drops should accomplish the necessary increase in strength. That is also something Dave could readily do without any messing about with cloth and resin.