Thermoformed deformation

Does thermoformed plastic deform from bow to stern if a kayak is suspended from the security bars (loops at each end, located about a foot from the end)?

Over the winter I hang the kayak with straps around the kayak close to the cockpit, but during the recent hurricane I temporarily hung it from the security bars (to get it off the floor) and that made me wonder whether thermoform deforms if hung like that over a period of three or four months.

I don’t expect it to deform, unless the
boat is very light and thin. That material really sets dimensionally with the heat of factory production. It isn’t creepy like polyethylene.

Need better definitions

– Last Updated: Aug-30-11 12:22 AM EST –

I would attempt to support a hanging kayak in places
closer to the mid-front and mid-rear than at the ends.

Polyethylene is the least expensive material used to build kayaks today.
There are 2 -types of polyethylene:

-Linear Kayaks: (least expensive)
are made using a process called roto-molding. Plastic pellets are added to a two piece mold, the mold is sealed, heated and to melt the pellets to liquid, then rotated rapidly. When complete the mold is cracked to remove the kayak. Although a slight seam will appear on the outside of the kayak, the interior seam or stress point is all but eliminated.

-Cross-linked Kayaks: (slightly more expensive)
are made from a patented "sandwich approach". A thick foam core is sandwiched between an outer and inner layer of polyethylene to provide additional stiffness. Cross-link kayaks are stronger and stiffer than roto-molded kayaks but they are also much heavier and moderately more costly.

Thermoformed Kayaks:
A relatively new process, which uses plastic sheets of compatible hybrid plastic materials to form a kayak over a mold like a blanket, rather than inside one like fibreglass or roto-molded kayaks. Most of us have seen the Saturn Cars (TM) commerical where the shopping cart bounces off the car with no damage done... that's thermoform! Most modern automobile bumpers are also made with thermoform. The Outer surface is harder than other plastics and provides better abrasion resistance... which means they don't gouge like softer polyethylene kayaks. Thermoforming produces a product similar to fibreglass in appearance and performance. Thermoformed kayaks may be slightly heavier than composite kayaks but normally cost about $500 to $1000 less. While fibreglass & Kevlar kayaks remain the Holy Grail, thermoform kayaks offer a new alternative to the much heavier, less attractive roto-molded & cross linked plastic kayaks!

Note: Thermoform comes in vastly different grades. Pelican & BIC Sport Kayaks use lower grades of thermoform, while Delta Kayaks, Perception Kayaks Essence Series & Seaward Kayaks Infiniti Series are examples of high-end thermoforming technology.

YES it will.
G2D , The "setting’ you speak of is when its fully suported in the mold. Hang it by the ends in in the summer heat and its gonna move. Measure it and let it sit( hang ) … then measure again.


Any kayak

– Last Updated: Aug-30-11 12:16 PM EST –

Regardless of manufacturer - avoid the carry straps for prolonged storage.
Many us support kayaks under front and rear bulkheads.

I believe Eddyline didn't make many Roto-molded Polyethylene kayaks.
Seemed like they've had thermoplastic "Carbonlite" for a while now.

Typical kayak old school production method

I could use some more rocker

I will patiently await data, because
I don’t have a thermoformed boat to test.

You could try it with one canoe : )
Let it hang from the ends about 8’ up in the garage.

If you don’t want to measure the rocker, measure the width change.

Very cool video
Thanks for posting!

In the same spirit, here’s a great video showing how Prijon produces their High-performance ThermoPlast (HTP):

German engineering…

You can probably get away with it for a short time, but if stored that way, it will deform.

I have seen this happen to three kayaks.

Don’t use it to increase rocker, since the rocker may not be where you want it. Storing it overhead works nicely, but the kayak must be supported properly.

I’ve hung composite boats by their
ends, and they don’t droop or distort. Not ever. Never.

Only two of the above replies seem to be referring specifically to thermoformed. For those who are knowledgeable about thermoformed plastic: It is said to be much more resistant to warping than rotomolded. But it’s still plastic. Is it less resistant to longitudinal warping than fiberglass, for example?

I’m not planning on storing my kayak like this. I’m just curious about the properties of the material.

same here
My granite kayak always hangs from the ceiling and it still has a straight keel.

do you know another way to increase


Had an Eddyline Kayak and called the factory to ask the same question. I was told the Chrome loops which support the grab handles were “NOT” designed to hang the kayak for storage and not to do it. They recommended two straps under the hull located at the bulkhead locations if the kayak was to be stored hanging. That may have changed but they are only a phone call away.

Was about to say the same thing
About contacting Eddyline. When I’ve written, they always reply very quickly. A friend of mine also contacted them and they wrote right back. They’re very good at customer relations.

Remember, we’re talking about
permanent or long-lasting change, not the emporary distortion that occurs while the boat is hanging.

Anyway, in talking about “thermoformed” I believe we’re restricting ourselves to Lexan type plastic. No one would expect a composite kayak or canoe, full of carbon fiber or glass fiber, to distort permanently from being hung by its ends.

What happens when you put a big fat kayaker in the cockpit and place the boat in the ocean? Is the boat going to distort permanently?

What happens is G2D is displacement
The water is supporting the boat and weight of the paddler over the entire wetted surface.

Apple and oranges comparison.

something I just thought of
My composite kayak sat on it’s side on a concrete floor for half the winter. I just looked and there is no (visible) flat spot.