Dimple in hull... help !

I have been busy doing work on the house so the kayak has been covered outside all summer.

I have just moved it and there is a depression in the hull… this has given me a depression as well.

It is a SOT (Cobra Expedition) and has been covered with thin ply all summer. I left if face down with the hull uppermost.

I am guessing that the sun got too hot for it and the bit where it has dimpled has melted and sagged a bit - the dimple is the size of a sheet of A3.

What do I do ? (apart from buy a non-plastic yak :slight_smile: ). Any advice REALLY gratefully received… the house is coming to an end and I am thinking of kayaking again soon. (And finishing a new greenland paddle).



The boat and place it out in the hot sun, if there is any hot sun left around your parts…if not, take some boiling hot water and pour it over the depression in the hull.

Both will usually heat up the area enough for the original hull shape to pop back out…usually hulls “remember” their shape before deformation.

With the application of the boiling water, it may need a little help by pushing or manipulating the hull with your hand from the inside of the boat.

I wouldn’t worry about it, many poly boats see this or “oil canning” from time to time.


Did it really melt? We had 115 degree temps and over 100 every day for weeks and although my poly yaks oil canned, they did not melt. It sounds like maybe something else happened to it?

if plastic boat…
check out this article:


Don’t worry
I bought a plastic boat from a major sporting goods store, they stored it on a rack that created dents in the hull. After getting a nice discount, the dents popped out in the sun.

I"ll give the above heat treatments a go…

Yes it is plastic (Cobra Expedition - 18 foot 21 inch beam and a good SOT for sea use).

Seems strange as it is quite localised.

I"ll go for the towel and kettle approach.

I welded up a little trolley at the start of the summer and noticed that there is quite alot of bounce at the other end if I place it on the trolley and waggle one end - the other end bounces up and down more than I would imagine.

I guess in the water the kayak moves around alot too losing energy, for a stiffer hull would you have to go for a fibre hull (glass–carbon–kevlar)… apart from surfskis there dont seem to be may fibre or non-plastic SOTs.

What is oil-canning ?



RE: What is oil-canning ?
Oil-canning is a term that causes endless debate. My definition is different than what was referred to above.

IMO, you have a dent in your boat. It did not oil-can, it dented. The dent will stay there until you fix it by heating until it pops back out.

Oil-canning refers to the bounce you noticed in the hull when pushing on one end. Basically, the plastic hull is not as stiff as a grp boat and will flex a small amount in and out as you paddle. This is oil-canning - the water pushing your hull up and then back down as you paddle - like an old fashioned oil can where you push on the bottom and it pops back into place on it’s own.

The term is almost used generically now to refer to dents as well as hull flex, but the origin in boating comes from the first Royalex canoe hulls which flexed a lot while being paddled.



The dents that my yaks had from being out in the hot southwestern sun would pop and move with pressure. The yaks hadn’t been moved in months and the dents were in the hulls. I flipped them around and they were gone in three days. I can’t imagine the sun in a more Northern latitude actually melting a kayak.

If one gets a dent in their car fender it’s a DENT.

They wouldn’t say “my fender is oilcanning”.

It may be hopeless though…

I think…
… that I get it now.

The depression that I have is a dent, it is not from oil canning. I think a strap was too tight and maybe a really hot cat sat in the same location for the last month:) No idea really but at least I will give it a go to fix.

I can just about get a stick to the right place and I think the hot water and towels and the stick should push it out a bit.

Perhaps it is time to upgrade and get a stiffer hull.

Originally I joined this forum about 2 years ago and got great advice that enabled me to make the choice to buy this kayak (Cobra Expedition - pink one - dont ask).

I"ve used it a fair amount but probably not as much as I should do… commitments with the house (building a roof this month :slight_smile: ). But I do like it, I originally bought it for snorkelling/freediving from in hard to reach places and have done that.

Through using it I discovered the sheer joy of paddling and would often use it just for paddling. Half day trips out from my local beach just tooling around chilling out.

I was after a sleek surfski originally and think that I’ll try and get one now. I think that the stiffer hull and more minimal set up will suit me for when you just want to go off for a blast. I like the Huki surfskis - seem crazy at around 25 to 35 pounds… more what I am looking at. Carrying a 55 pounder is not much fun and the trolley is not ideal (wheels too small).

Anyway - enough rambling - many thanks for all the info here and in the past - will be looking slowly to get a fibre surf ski (some combo of glass/carbon/kevlar maybe a Custom Mark-1 / Huki something or other / Fenn type thing)… hard to get here so I might even look at building one. I have no experience but a friend is a boat builder…

:slight_smile: NM

You might be able to…
…simply ignore it.

It probably bothers you more visually than the

boat performance wise, unless you are headed for

the olympics.

I am always heading…
… for the olympics :slight_smile: Nah… not really, but as it hasn’t happend to me before I was worried.

I tried the hot towel approach after lunch today and it worked really well.

I was amazed at how soft the plastic got. I used a piece of wood to push the hull back into shape after pouring boiling water from a kettle onto a towel and leaving it on the hull for a couple of minutes.

I had to hold it in place for a few minutes whiule the plastic hardened up again but in the end it is like new again :slight_smile: Many thanks one and all.