BEST PLASTIC SEA KAYAKS

don’t forget repairability
For me one of the reasons to buy composite boats is because they can be repaired more easily. Also, they don’t abrade as easily as plastic, so for some uses they’re a lot more durable than rotomolded.

Respectfully disagree Griffin
I can’t recall one Valley boat cracking at the bulkhead weld. Could be wrong, but just haven’t seen or heard of such. Your reply sounds like a competitive marketing line Vs a valid engineering point. Having been an R&D guy in the business I will share my opinion, for what it’s worth?: The welding process is very tough when done correctly but involves a special meash wire screen that gets charged electrically so as to melt the poly together. Too much juice and burn-out, too little = poor bond. Done right = great bulkhead! Most manufacturers favor foam because it’s easy, fast, works well, and is cost effective = more margin and simplified manufacturing = smart. This does not mean that Valley’s approach is weaker. Having messed with all approaches, I’d personally opt for welded bulkheads such as Valley’s. If I built and sold 50,000 poly kayaks a year I’d use foam…



Having said that, I’d buy whatever kayak fit me the best and I enjoyed paddling the most and I’d live with whatever system they employed. Really doesn’t matter much, except for internet forums.

It is not snake oil. Of this I am sure.
It is also not about pushing on the deck of a roto boat to see how it moves. Take my carbon/kevlar Nordkapp and pick it up at both ends with two people and jerk it up and down. Now do the same thing with a roto Nordkapp. That flex over the length of the boat is what is robbing you of speed on the waves. If the water is calm, there is likely to be no real difference provided the coefficient of friction is the same. The movement lost in flex is lost in forward travel and it also changes the profile of the wetted surface. You will also see a more noticeable difference in acceleration. During my windsurfing days, the change from plastic hulls to carbon was like night and day in terms of acceleration and speed. The Eddyline made thermal formed boats are highly rigid and thus do not suffer from this issue. If these things matter to you, test the difference, if not, ignore it. Either way it is real.

Bill

Makes some sense, but…
I’m not sure waggling a boat from both ends on land is the same as loading it on water. Do plastic boats really go banana shaped in the water with the weight of the paddler? I’d like to see some vigorous testing of the claim that plastic boats are less rigid, particularly in respect to the newer plastics. Composite hulls do flex some: that is what all the popular hammer tests show.



I think the real difference is in weight, which affects acceleration and speed over the long haul.

not 17 feet but darned sea worthy
http://kayakcamping.amongstit.com/2011/01/18/ted-keys-video-of-the-inuit-being-paddled-through-lava-falls/



check out this video to see a Native Inuit 14.5 and see for yourself if it’s tough enough. Plenty of room for 2-3 day trips although these guys did over a week. Gotta wait a minute before you’ll see the Inuit run Lava Falls.

What do you think two waves do when
they pick up a boat? I don’t think “vigorous testing” is needed to understand that hull flex is detrimental to a hulls efficiency. Again, I suggested that if someone is concerned about this, they need only test a hull that is offered in roto and composite. My Nordkapp example is exactly what I did. I also said that the Eddyline thermal formed boats are highly rigid, thus stating that there are rigid hull alternatives in plastic. Bill

Fair enough…
I guess I would just be curious to know how much deflection? At what weight? Over what hull length? For a total loss of efficiency of what percent?



We measure everything else with our kayaks.

re test
Are you quite sure that the hulls are identical?



Plastic shrinks as it cools, making a mold to produce a hull identical to composite layup is non trivial. Going the other way - making a mold based on plastic kayak to produce composite boat - is much easier, but I am quite sure only Jackson has done it (maybe) for their playboat.



I hope Salty chimes in.

I would do it, but I am too lazy.
I just go by my life experiences with this sort of stuff. The windsurfing one in particular really reinforced this notion. The flex of roto is not really the big issue for me, it is the weight. The Eddyline is both lighter and stiffer. The only thing it lacks versus roto is impact resistance, and for me this is not a deal breaker as I don’t white water paddle, or rock garden. I know that I can feel the flex in my Aquanaut LV RM in certain wave conditions. I would buy this boat again a hundred times over as it does so much else so well. It is not huge issue, but it is an issue. Bill

I am quite sure they are not identical,
but I don’t think this has much bearing on the issue in general, not specifics. They are close enough in design that gauging the level of flex is still relevant. Flex robs efficiency. Bill

add to that:
The weight of a loaded poly kayak. I’d think this would increase deflection.

Of course, if we’re not convinced, I know I could always use another excuse for a boat purchase!

Really doesn’t matter much…

– Last Updated: Jan-21-11 1:31 PM EST –

except if one greatly prefers bracing off the bulkhead rather than foot pegs - which some of us do. This would be less of an issue if sea kayak manufacturers emulated ww boats which often have a sliding foot rests the size of a bulkhead.

bulkheads
The problem with the hard edges of bulkheads really only show up if you just happen to catch one at exactly the right spot at the wrong time. It’s not a problem otherwise. Seeing it show up on a forum in a couple years of production would be rare, specially for a boat built as well as Valley does. Having a problem show up in 10 years might happen, has on certain fiberglass boats.



With new boats if it were a problem the manufacturer’s warranty would cover it and you’d never hear about it here or on the other forums, takes years.



Still if I were in the market for a grossly heavy poly boat, which I’m not, I’d buy the design I liked and wouldn’t give it a thought either way what the bulkheads were.



Bill H.

kayaks
Btw, I don’t buy kayaks, not in years and years. I build kayaks. Not paying anyone thousands of dollars for one, sorry.



Bill H.

If they’re poly boats, then they are not
using epoxy. Even West G-flex is too stiff, and requires expensive labor to prepare the inside of the hull by flaming. A urethane glue, maybe.

Flex

– Last Updated: Jan-24-11 2:20 PM EST –

You find that "flex robs efficiency" and this seems reasonable, but boy would it be hard to prove. I'm not doubting your experience, just wondering what the mechanism might be. If the energy to flex the hull comes from the waves - what's the penalty? Maybe the boundary layer on a flexing hull transitions to the turbulent state earlier, or perhaps drag is increased due to some vortex-shedding mode stimulated by the hull oscillations.

As a side note, it has been theorized by some (notably George Dyson) that the built-in flexibility in a Baidarka is an aid to paddling, and helps it deal with waves more efficiently. This would be equally hard to prove, I imagine.

Valley has been welding
bulkheads for at least a dozen years Griffin. Very early versions had some issues but those were resolved. I used the product in rentals, and guiding with zero issues. Again, no offense, but it’s an example of internet “expert” opinion without any real supporting data. Sounds like you have very little or no experience with said product?

I wish I had science to offer you, but I
only have experience and theory to give. Let me try this. Why are downhill racing skis stiff? Why are are racing sailboats and racing offshore boats so stiff? I think it is because they are faster when they are stiffer. I think they are faster because they are more efficient. “I think” that when you apply stroke energy to the boat that causes it to flex, the energy lost in flexing could have been applied to forward motion, in that all of your input goes into forward movment and not whatever movement the flex is doing. “I think” your paddling energy is going into the boat for transmission into forward movement. If the hull is flexing from your energy input, it is not using that input to move forward. It may slso be that some part of the flex downward (a axis) from a wave could have been used to move forward (b axis). This is my feeble attempt to theorize what I know from experience. Bill

Prijon Barracuda
or Valley Nordkapp

Priority of your considerations?
Does speed rank higher than stability, is maneuverability in there anywhere? Are there any boats you’ve paddled that are sure no gos for you?



May help refine some answers.