Poly Boats in Hot weather

-- Last Updated: Jul-06-12 10:49 PM EST --

Just bought a Zephyr 160 a few weeks ago and have had it out and on my j rack on my truck at least a dozen times, plus a three day trip, and no problems with the plastic indenting or anything.

Today, I put it on my j cradle/rack on my truck, get to the lake, and the hull had a big depression in it. I might add that it was really hot out, around 30 and humid. The kayak did not feel warm, but there was a depression where part of one of the cradles touched the hull. I use two nylons straps, one for each cradle and a tie down front and back....I do not put a lot of tension.....my wife has a composite boat and my other boat is thermoform, so im used to not overtensioning.

Is this a normal occurance for poly boats and something you have to live with and constantly fix? or is my plastic thin on the zephyr ? I was able to push the hull back out most of the way by applying alot of pressure, but when i put it on to go home, it did it again....is this now a weak spot? I was able to push most of the indent back out again when i got home

My composite and thermoform never lose their shape or indent like that so this is all new to me...

Plastic wwill do that on hot days but
it should pop out when you get the pressure off and it cools.

30 degrees isn’t hot
It’s below freezing!

That happened when I brought my
Necky kayak home from the benefit auction where I bought it. This kayak has a bulkhead behind the cockpit, but none in the bow. Bulheads supply some resistance to denting from racks and rack hardware.

So, I cut a short removable vertical wall from some Ethafoam I had lying around. It was cut to push the dent back where it belongs, and to support the hull against denting when on the rack. I take it out when paddling, and the hull holds form like it should.

The only time when a dent becomes permanent is when a kayak is dragged over dock edges (seal launching) or over river ledges, so that the plastic not only gets pushed in, but gets stretched, mostly in the longitudinal direction. Dents from sitting on a rack are less serious, because the plastic isn’t stretched much out of its intended shape.

unless you are in Canada…

My Zephyr got a dent
from sitting on the garage floor for a couple of weeks on its bottom. It went away. I think its par for the course. I did start transporting with the kayak on foam blocks upside down resting on its decks and that has eliminating any problems while transporting. I now hang it in my garage either upside down or on edge and I’ve had no problems. But it is an issue with poly boats - generally not a big deal.

We see it less with poly ww kayaks,
perhaps because plastic may be heavier, and ww kayaks are often more tightly rounded, rockered, and have features like chines that tend to inhibit denting.

When poly ww kayaks acquire dents, it is usually under the seat, and is caused by the plastic getting stretched as the boat is seal-launched from rocks or pulled over the edges of ledges, with the weight of the kayaker bearing down. I never had a persistent dent in a ww kayak from just tying the boat down on racks in a hot day. But, I guess it could happen…

J-cradle pressure points
When I had Thule J’s and carried a plastic sea kayak on it, eventually there was a very slight flat spot where the rear cradle pressed against the hull. Barely noticeable, but it obviously happened at the exact place where the contact was. Later when I put a glass kayak on it, the same contact area showed the beginnings of abraded gel coat. Merely a dullness where there had been sheen.

I immediately stopped using those cradles for any kayaks and switched to Malone J cradles, which have flexible composite backs. Unfortunately, I can’t recommend the Malones, either, because one of them broke and I’ve heard this is not uncommon with them.

I was starting to think I got such a good deal on it because it had had previous problems. I got another dent today, but like you say, it eventually pops out. It just freaked me out at first. I think ill replace my j rack aslo, im afraid that sitting in the same spot each time will cause a permanent dent over time.

Heat does make it more likely

– Last Updated: Jul-07-12 10:23 PM EST –

...to dent.

I've noticed that, after sitting in the sun even a short time, dark plastic feels hugely hotter to touch than light-colored plastic. Wouldn't surprise me if the darks also are more dent-prone.

WW kayaks weigh less, too
I have seen them dented in ways that look like they were strapped onto crossbars too tightly. Not everybody uses stackers or J’s for them.

I suspect that is 30 deg C.
That is hot.

Look up the definition of ‘plastic’.
I don’t think it will permanently deform.

guess when I said 30, I should have said 30 degrees, eh?

yes in Canada…it was 36 the day before

It can deform permanently
My first sea kayak did, after being rooftopped (with cradles and all) on a long trip in the summer. The pronounced dents never went away.

Maybe if you catch them in time and do something about it, they at least partly go back to normal. I had shallow dents beginning to form on another boat (also from transporting in very hot weather on a long road trip). But those did go away after the trip.

Yup, you’re stuck with it

Carry the kayak w/deck facing J-cradles
If you carry the kayak with the deck against the long sides of the cradles, you won’t see as much deformation. The hull is a long expanse of unsupported, unstructured plastic. In contrast, the deck tends to have more structure, thus more rigidity, and is much more resistant to denting.

With plastic boats, the cockpit coaming and hatch rims tend to be molded into the structure, so you don’t have to worry about putting pressure on them the way you do with composite boats, where the coaming & hatch rims are separate structures glued in.

Air temp is not the same as hull temp
Yes unfortunately poly deforms.

I have a big heavy tsunami 175 and I found the only way to minimize the oil canning was to load the kayak sideways on the j-bars so that the part of the hull which touches the water has no weight on it…its almost on its side. I alternate sides on which the boat rests.

You can try fix a dent which does not go away with very hot water, a heat lamp, or hot air gun. The hot air gun is the trickiest and most likely to damage the boat.