One question. Do thermoform kayak hulls suffer distortion if the kayak is not stored properly?
thermomolded hulls
Plastic thermomolded hulls can suffer deformation if stored on narrow bars, especially in warm conditions. They frequently suffer some damage if strapped tightly down on racks in hot sun.
I tend to hang kayaks from 2 inch nylon tubular webbing loops which conform to the boat, and usually store them deck down. A small amount of deck deformation won’t affect the performance of the hull.
Hull distortion
YES
No
Own a Hurricane Tampico 135S in Trylon and it has been stored outside for almost 3 years.
SE Michigan temps range from highs in the 90s in summer to lows of 20 degrees below in the winter.
There is absolutely no deformation whether racked on my car or stored on the two foam J hangers on an outside wall. FWIW there is no color fade at all. (my boat is yellow over white, and I do use a UV resisting fiberglass polish on the deck 2x a year.)
ThermoFORMED plastic is not rotoMOULDED plastic. Two completely different materials. Not to disparage anyone’s response, but there may be some honest confusion here.
Trylon is, btw, a proprietary version of the wider class of ABS plastics. Trylon is used by Hurricane AquaSports which is different from the thermoformed plastics used by other makers.
Wilderness Systems new Ultralite is made in the same factory in South Carolina, but is a different formulation called ACA plastic which performs similiarly.
So there is plastic and then there is plastic 
eddyline
After three years, my eddyline is straight and true, but I store it properly and indoors. I believe in the thermoform product.
I bought mine from Rusted Moon outfitters in Indy and they had a piece of red thermoform that they put on the roof of their store in elements and sun for a year. At the demo day they were showing how the color was a spot on match to a new red boat. If it had faded it wasn’t immediately evident.
thermoformed plastic
I did confuse thermoformed construction with rotomolded construction. However, Royalex canoes consist of ABS which is thermoformed in a mold, a construction process which sounds very similar. Royalex conoes will deform a bit with improper storage, so I wonder if the same wouldn’t apply to themoformed ABS kayaks.
different kinds of t-formed plastic
– Last Updated: May-21-09 10:56 PM EST –
we refer to it as consumers would, as a broad category. Actually there are different formulations, some of them proprietary. Out in the marketing world it all gets under the same tent.
I just googled royalex and found this info in the Paddler's Dictionary, which states that
Royalex is often mistakenly called ABS:
Royalex A laminate made of at least five layers of plastic used primarily for open canoe hulls. (Often incorrectly referred to as ABS.) An inner core of ABS foam is sandwiched between two or more layers of solid ABS sheeting and coated with outside layers of vinyl. It is very rugged and very heavy. Lighter weight versions are available that sacrifice some durability. The outer vinyl layer makes the hull slide well over rocks, but it is not very abrasion resistant, and a little of the surface peels of each time it glides over a rock. Also, fastening outfitting to the slippery hull is tricky.
end of quotation
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the Hurricane kayaks are sheet molded of Trylon w. no intervening cores and no vinyl.
your timing on this discussion was GREAT
My husband, who is building me a boat storage building just walked by.
I’ve been trying to explain to him that his idea was good, but hull distortion can be a factor.
Since he knows a lot of stuff, but not everything, he’d been arguing the point with me.
I made him read this thread - now he will do it how I want it : )
good 
shouldn’t he be doing that anyway '-)
Actually I researched the hell out of Trylon and its properties before I bought my Hurricane kayak. That’s how I came across this stuff. Can’t claim to know all about it - chemistry was not my major
Royalex
– Last Updated: May-22-09 10:00 AM EST –
The vinyl coating on the outside of Royalex is for cosmetic purposes and for protecting the ABS substrate from UV degradation. The vinyl lining on the inside of Royalex hulls is to facilitate bonding D rings and such to the hull, and again, to protect the ABS substrate from UV degradation. In both cases, the vinyl layers contribute nothing to strength and would not influence whether or not the hull was susceptible to deformation.
The rest of the Royalex sheet is ABS. It is not solid ABS but it is ABS nonetheless. The foam ABS core is generated during the thermoforming process of constructing the sheet.