Modifying plastic kayak

-- Last Updated: Jun-02-08 3:48 PM EST --

After a lot of searching of a boat that would be streamlined enough yet offer enough foot room for my size 15 feet, I'm starting to play with the idea to just get a second hand Tempest 170 in plastic and modify the area above the foot pegs for more room.

Basically, if it can be stretched with heat about an inch up or if a piece can be cut out and replaced with a "hump"...

So, what are your thoughts about modyfing a plastic boat this way? Does the plastic in the Tempests respond to heat well enough to change its shape enough without losing much strength?

If not, then I'll have to cut and glue back something in its place, so what kinds of adhesives would work best? I read a post here about and I think there is a similar if not the same "flexible" epoxy for sale at my local hardware store. This stuff should work I think. Or should I "melt" some similar plastic and just pour it aroung the edges of the new shape?

How do the manufacturers make these boats in the first place - it seems that the hull and deck are somehow manufactured separately and then molded together. How do they do it and is this a DIY task for a smal larea of about 20x 20" or so?

Other ideas welcome of course, but I seem to come back to the fit and other features of the plastic Tmepest 170, including the price, that seem to be just right for me...

EDIT: I found some guidance from Wilderness Systems themselves:

Does not look too encourageable, but it seems that the material responds well to heat and with enough care can a raised patch be melted together with the hull...

Foot bumps
Adding foot bumps was more common among whitewater folks with some of the “slicey” playboats a few years ago. From what I remeber reading, it can be done with a heat gun and an appropriately shaped form, but it’s easy to overdo and melt the plastic or get it too thin.

I’ve seen and heard…

…of all sorts of things. filling the boat up with

boiling water and driving over it to reshape the hull,

filling it up with boiling water and stuffing basketballs

in it for the reason you mentioned.

Don’t do it. If you’re lucky, you’ll only screw up

the plastic. Those guys got their boats for free.

Give an open canoe a look-see.

The basic process
is heat the deck and apply pressure from inside the kayak. The kayak has to cool completely before you remove the pressure device. The pressure device can be lots of things but needs to be adjustable. Two car jacks will work with a properly shaped object on top of each. Heating with a torch is possible but very tricky. Depending on the plastic a hot air source can also work (e.g., a high wattage hair dryer). Apply heat and gradually raise the jacks. Light several prayer candles and have several prayer wheels going.

That’s not bad -:wink:
I’ll get a supply of prayer candles and may be use some of them to heat the deck -:wink:

I think you may be up to something with the floor jacks. I have two that would work for this with something on top of them. I really need only 1/2" to 1" of “stretch” in a very specific area, so that might work. If not, I’ll have to add two more hatch covers to the holes I’ll create for easy on the water foot-scratching access -;(

Get rid of the foot pegs …
You can make removable minicell foam foot blocks and anchor them with velcro or just glue them in place. If your foot fits barefoot with pegs, when you move to blocks you should be able to make your feet comfortable in footwear that will work for whitewater/rocks. I’ve never heard of anyone using something like Jackson Happy feet in a seakayak but it will work too.

I’ve had success with a 500w
work light, the trick is to be patient and crank a scissor-jack little at a time, you’ll also have to make a plywood and 2x4 crib nearly the exact shape of the bottom and long enough to spread the load, use your imagination. It might be easier on a bench in the cellar where you can use props to the floor joist to help form the top, ya it sounds like a Frankenstein trip, but you asked for it. do pre measure the hull in spots and check as you go and good luck. ed

seat adjustment ?
Probably a stupid question, but is the seat adjustable? Is it back as far as it will go? If it will move back, it may also move your feet back to a taller clearance.

Or, remove the front bulkhead, slide the seat forward, and let your toes stick out of the bow storage hatch. :slight_smile:

Moving the seat
In my Tsunami 145 I actually am currently experimenting with the seat. I moved it last week about 2 inches back. It has more room behind it still, but I do not want to go farther as I can’t lay on the back deck anymore.

So far the only advantage really is that I can much more easily enter and exit the kayak. On the other hand, the center of gravity moved back and I think it now surfs harder than before. I think I will move the seat back forward after a few more tries to be sure…

In the Tempest, the way the seat is positioned is good relative to the reat deck for laying back for rolls. It is a bit too close to the front than I would like, but one leg at a time I still get in and out OK. The length of foot pegs is just about right at the farthest point, but the height of the deck is too low.

If all else fails, I will consider to “…remove the front bulkhead, slide the seat forward, and let your toes stick out of the bow storage hatch. :-)”

I don’t have the feet you have but I do have a Tempest 170RM. I’ve had it since '02 and have moved the seat back twice and was happy each time. The first time I just moved it back as far as I could without drilling new holes in the boat, just the seat. That was about 1.5 to 2 inches I guess. That change made the boat MUCH more comfortable and improved its handling in wind due to the further aft CG. This spring I broke my back-band and while I was repairing that I moved the seat back another 2 inches by drilling one more hole in the boat on each side. Now the boat is PERFECT for ME. My comfort in the cockpit has gone up A LOT and the trim of the boat is now perfect. Previously the trim was not right without loading up the rear compartment. I wonder sometimes if the seat might have been installed in the wrong position in the first place? Regardless, Now I love the boat that I’ve always liked.


But moving the seat that far back, wouldn’t it interfere with your ability to lay back for a roll? On the Tsunami, I figured anythying more than 2 inches or so will push my back against the rear edge of the cockpit when leaning back. The Tempest has a lower rear deck than the Tsunami, so that might not be an issue. Got to take a look at the store specifically for this (by just relaxing the back band and seating further back as if the seat was there)…

I do contact the coaming with my back sooner but I can still lay all the way back. I can find nothing but positive things about the modification I made to an already fine boat. So much more comfortable and much better trim without adding extra weight to the rear hatch.


Thanks - I’ll keep that in mind
The extra leg room would be welcome as well for entry/exit more than anything else…