Thermoformed kayak - impact resistance

We all “know” that thermoformed plastic boats aren’t really suited for shallow rocky rivers since they aren’t as impact resistant as rotomolded boats. After hearing that from me and a salesman, my kayak-shopping friend asked the salesman how many repair kits he’d sold for thermoformed boats; the salesman looked a bit sheepish and said, “None.” My friend asked me if I had ever actually heard about a thermoformed boat getting cracked or fractured and I had to admit that I haven’t.

So, while I’m reasonably sure that thermoformed plastic is more likely to get cracked or fractured than rotomolded plastic, has anyone here actually seen (or heard from a reliable source) a thermoformed kayak that has cracked or fractured?


I have an ancient Prijon Invader whitewater boat that is thermoformed. It’s had plenty of encounters with rocks. No cracks.

Just to note that Royalex is a sandwich
in which the “bread” is thermoformed ABS. Wonderful stuff, but the ABS layers may crack under big hits.

The Kevlar in S-glass/Kevlar or carbon/Kevlar boats is there to resist cracks or tears, and to minimise propagation of such cracks if they occur. “Kevlar” boats may take surface cracks in the outer S-glass or Carbon layers, but usually the inner Kevlar layers prevent a leaking crack or worse.

I believe one of the sea kayak companies has been backing an outer ABS layer with inner Kevlar. But I may well be wrong.

Again, I think thermoformed ABS is a great material for boats. Stiff, light, sturdy, repairable. Of course it’s not the only logical choice for river or ocean punishment.

ABS has been tried by several companies as a replacement for gelcoat on a composite boats. Not sure it would be a great idea on a paddle craft as it’s pretty heavy. Not a heck of alot of point in paying for the lightness of Kevlar then adding a heavy ABS coating to it.

Bill H.

Just throwing this out there…

My only relationship to Delta Kayaks is that I am a happy owner of their 17 foot model.


While this video is somewhat
impressive, I don’t recall the last time I paddled into a storm of hammers while upside down. A loaded boat dropped on a rock would be a more accurate test, and even more accurate in low temperatures. Thermal formed boats are very tough, tough enough for the vast majority of paddlers. For the record, my skin boat with simple 12 oz nylon and varnish would handle that hammer just as well. It would also handle the end of a screw driver too. If you dropped the boat loaded into a screw driver I can assure you the results would be very different, at least on the skin boat for sure. Bill

thermoform durabilty
The wind took a current designs tcs kestrel of the roof while loading and it hit pavement hard. It cracked at the seam a few inches. Repaired with glass and resin.

Thermoform carolinas in the instructional fleet have held up quite well for 5 or so years. No repairs needed.

I did not know that CD and Carolinas
were made from Thermal Formed Sheets of hybrid plastic. Are you sure you don’t mean Thermal Formed as opposed to Roto or Blow moulded? Bill

CD has stopped their thermo production and Perception halted thermo designs of the Carolinas years ago. CD called it TCS and Perception calls it Airalite. In fact Perception still does a few of their Essence 17 and Tributes in Airalite. Nice stuff.

The Eddyline ones are tough
I had my Fathom over my head. Twisted my ankle and threw the boat. It hit my truck extender, bounced huge and hit the sharp landing ramp concrete ties, then continued bouncing and rolling down a rock pile and eventually splashed into the water. You had to look in just the right light to even see the scratches. The whole incident would be like dropping your kayak at least 20 times onto a rock pile.

Also, was practicing for racing. Going full tilt. I somehow managed not to see this rock protruding from the surface. With much current pushing me and paddling full bore I crashed into what was essentially and solid rock island. The boat ground to a halt completely on top of the rock which was about a foot above the water surface, with my 220 ample pounds and other equipment on board. I was horrified it would not float. Upon inspection, there were some gouges at the keel line where the bottom of the V hull took most of the abuse. Again, the gouges were extremely slight considering the brute force of the impact. Easily repaired, filled in, with some special epoxy recommended on the Eddyline pages. If I had to do the repair again, I would have just used the Acrylic clear paint recommended and drizzled it into the scratches. I spent way too much time and some money overdoing what was actually just a slight gouge. Still, the repair was fast and easy. It could have been faster and easier and cheaper. Nothing cracked. Nothing broke through. If I would have done that with the poly boat, there would have been some impressive grooves. The Fathom is smooth as glass again.

I got the Perception Sonoma in Airalite

– Last Updated: Aug-18-10 10:50 AM EST –

and, knock on wood, it has been quite sturdy so far.

For about 2 years now I've been using it 80% on class 2-3 white water (average once a week or so, year round, with some ice flows a few times). And once or twice a year in ocean surf.

In the white water I always hit a rock or two every time. Just yesterday I was trying to attain a rapid I've never attempted before. That's the little 30 feet wide rapid above Fish Ladder on the Potomac leading to the bottom O-Deck. There's a lot more to this rapid below that narrow section - nice surfing standing waves that I've been playing in before that. Bbut the attainable section is short and narrow with very fast current and a little drop on one side, so you have to cross it just right or you wash down. Looks doable but you can't miss a single stroke as the current is fast and the eddy on the other side is small. Failing in my attempt, I slid down with the swift current (probably 10-12 mph) over a hidden pourover rock for a reasonably hard bang, then tried it a couple more times to the same effect - nothing happened to the boat so it takes relatively hard bumps in normal use just fine...

Granted, I don't tend to slam into them full speed with the bow, but I often hit the sides or bow or stern or bottom quite hard when going over rocks I did not see or when eddying-out in restricted spaces. And as the Fathom owner - I occasionally stall on top of hidden underwater rocks - just scratches, not even deep gauges...

She's gotten quite a few scratches but no cracks yet. There are differences in construction too - this one in patricular has a sort of a double/channel kind of a seal b/w the deck and the hull so they are not just simply overlapped. At only 13.5 feet being shorter than a 17-18 foot "monster" helps too I guess.

The material flexes and absorbs bumps quite well but I'm sure it will crack if I land hard on something sharp...

The Alaw's etc. are supposed to be tougher with thicker material. They will be sturdier for sure. Don't know about the weight though. It seems most of this thermoform stufff is to lower the production cost for the manufacturer rather than pass the savings on to the consumer... It is, I think also a lot cleaner process - no nasty fumes, scrap is recyclable, less waiting for glues to cure, no huge ovens like for the rotomolded boats...

These boats should be CHEAPER IMO - afterall, they stamp the hulls out like plastic plates from a press, then just glue the lids, err... the decks to the hull and they're done aren't they -;)...

no simple answer
there seems to be a fairly broad array of manufacturers, designs and proprietary materials all making up ‘thermoform’. the inherent flex seems to help, and the hardness of the outer skin is hard to gouge. it’s the quality of the seam construction that seems to indicate where they will likely fail, and then the repair seems relatively easy. the downside is that it can’t be sanded and faired in like a glass composite boat, but they seem very tough to me.

It is nice to hear some positive comment
about the toughness of thermalformed. First hand non-affiliated remarks are what we need to make decisions when we lack the experience ourselves. I have cracked an Eddyline and so has my friend, I would buy another one tomorrow for the right price. Then again, I would probably buy anything tomorrow for the right price.:slight_smile:


Personal Experience
There are cracks that go right through my thermoformed kayak that it picked up by sliding over rocks while paddling in Class I whitewater.

Thermoformed hulls are not all created equal, but personally I would favor polyethylene for any boat that will be paddled amongst the rocks.