Efficiency between kevlar & plastic?

I’m curious how much actual (not perceived) difference in efficiency there is, really, between a composite kayak and a plastic kayak of the same make and model. Is it 2%, 5%, 10%?

Hull flex is not an issue in a loaded plastic kayak, IMHO, and some composite hulls flex, too.

Perhaps a weight difference between the two, although a loaded kayak is going to paddle pretty much the same whether it’s 10 or 20 pounds lighter, I think.

Perhaps some loss to friction with a fuzzy plastic hull?

Perhaps a sharper bow of a composite cuts the water better?

But, is all this quantifiable?

It’s mental. Shiny, hard boats go faster

Here is what I have been told
Steve Scherrer (sp.), (Steve comment on this) told me through PNet (I think) that with the WS Tempest, the difference was 2% between plastic and fiberglass.

Ted Warren (Warren Lightcraft) believes the difference is 15% in real world paddling conditions due to the flexing of plastic vs. the stiffness of carbon/glass/kevlar (I am assuming kevlar kayaks have similiar stiffness to carbon).

Hope this helps. Just what I have been told.

Bill G.

Mt. Pleasant, SC

WS Tempest 170 (plastic)

“Bill, if you ever get a fast kayak, we will never see you.” Recent compliment to me from a friend that is a testiment to everyone who has helped me improve my paddling skills over the last 18 months.

did I say that?
must be right then!


on NEW hulls,especially the plastic one, there is little difference. scratches and wows and all bets are off.


I average 3 mph for 8 hours = 24 miles
which is true for most of my flatwater and saltwater trips, and there is a 2% drop in efficiency then a Tempest 170 composite will go .48 miles further in a day than a plastic T170. That’s appreciable, and it may make the difference between catching the tide right or finding a could campsite, but is it worth the extra $1500?

In a 10 day trip I would go 4.8 miles farther, which means I’d get there about 1.5 hours earlier, after 10 days.

Circumnavigating the Delmarva Penninsula would take 20.4 days versus 20.8 days. So I’d shave about 3 hours off a 3 week trip.

Is it worth the extra $1500? Well, yes, no and maybe, since there are other reasons to buy a composite than speed alone.

For an equal number of cloth layers,
of cloth with about equal weight, a carbon boat would be a good deal stiffer than a Kevlar boat. Kevlar is not a “stiff” material. It is a “tough” material best used for the inside layers where it makes catastrophic propagation of breakage less likely. Carbon makes a very stiff hull, but by itself can be brittle. Some glass, polyester, or Kevlar used in the right places can make a carbon boat tougher.

when saying “the same hull”

– Last Updated: Feb-22-09 10:25 PM EST –

The major advantage of designing a composite hull is that you can use more complex, finer shapes than you can get in a plastic mold making for a better engeneered hull shape.
To make a composite hull the same shape as you could mold it in plastic you will see very little gain (along the lines of 2-3 percent). If you refine the shape something along the line of 10-15 percent becomes possible.
Look at boats that are offered in composite and plastic layups for the same model and the shapes are most often quite a bit different between them, especially the entry line at the bow.

Ted Warren
doesnt make plastic kayaks.

Ted Warren is a lier. He said that to get you to buy one of his little wings. 15%?? BS!!

Shape and condition

– Last Updated: Feb-24-09 8:52 AM EST –

I agree w/ YetiM, that subtle shaping and a stiff hull can be significant, But skin area and condition is the big kick for frictional resistance; drag below wave making speed.

Winter's, the Shape of the Canoe, pg 21,22 lays it out for us. He claims 3.2 mils of ruffness increases frictional resistance.

Some numbers from John are 1 mill for new gel, 2 mils for smooth paint, and 40 mils for a badly scratched hulls.

When new, the difference between a shiny plastic, like Liq Logic's and a composite hull is primarily due to shape and flex. But both accumulate gouges and plastic shows upraised area.

The gel on the composites outer can be sanded back to new condition. The Plastic cannot be, so, over time, a composite hull can be maintained at 1or 2 mils surface condition. Plastic hulls tend to arrive at 40 mils ruffness, a 4X drag increase.

Winter's has an interesting graph indicating a 4X increase in frictional resistance as grain size increases.

my 2 % worth
hi …although i cannot vouch for the actual % differences between poly and composite boats …i can vouch for the composites being much easier to paddle, physical effort wise, than a comparable poly boat. I don’t whether its the weight diff that makes composite boats easier to paddle or the slicker finish to the hull that makes it easier, but I’ll take a composite any day …I had a poly boat and then bought a fiberglass boat that was 2 ft longer than the poly boat…i’ll use the F/G boat any day over the poly. the F/G boat,IMHO, has to be ,easily, 50% easier to paddle thru the water than my comparable poly boat was.

Experience and observation tells me that the 2% gain in efficiency of a composite boat to a plastic boat is probably about right – in terms of skin friction in the water alone, however.

In my experience, weight has a much bigger influence on boat efficiency. I’m guessing that a difference of 10 pounds might make a difference of more than 5% – if you are comparing speed of two medium weight paddlers (150 - 180 pounds)and two unloaded boats. Once you add gear, the efficiency gain of the lighter hull would be diminished somewhat.

Excellent point, Eric
"You can drag the plastic up and down the beach, might save you 10 minutes a day loading and unloading, pretty much balancing the time lost on the water."

I agree 100%. I’ve treated my poly boats so bad I’m ashamed of myself and they still look good. I don’t worry about surf landings on rocky beaches or even ramming into shoreline rocks and brush. Finding a place to go ashore is easier since I can pick the best spot for my camp versus the best spot for a soft landing.

Plastic vs Composite

– Last Updated: Feb-23-09 10:27 AM EST –

Put a mediocre paddler in a composite boat.
Put an excellent paddler in the plastic version of the same boat.
See if the mediocre paddler can match move for move the excellent paddler in the plastic version. See if the mediocre paddler can keep up with the excellent paddler in the plastic version?

The composite will be shinier, it would certainly be lighter to carry, and it will most certainly cost more. Will the composite be more efficient? Probably. Will the percentage of increase in efficiency be worth the extra cost? Maybe. Will the composite boat make the mediocre paddler a better paddler.
Probably not.

I think some paddlers fool themselves into believing that the reason that they bought the more expensive boat was that the more expensive boat would somehow make them more efficient, and it would somehow make them a better paddler.

Sometimes what we want is not necessarily what we need & vice versa. Which is not to say that we shouldn't have what we want. BUT knowing the difference is beneficial.


with a lighter
Composite boat you don’t need to drag it around like a troglodite life partner. You also aren’t as likely to need rediculous contraptions to load it on the vehicle.

But that’s all another subject.

The real differences
Plastic is much faster wherever I paddle, because it slips right over rocks and oyster beds. Composite boats scrape and grind over obstacles slowly. Plastic requires much less maintenance (just let the scratches accumulate). Plastic boats are much much tougher. Plastic boats cost a lot less and are easy to recycle.

Composite boats can be much lighter. They can be a repaired and maintained to last more than a lifetime. Plastic boats eventually wear out and cannot be repaired.

I think the real difference is the weight difference and racers always make a big deal about having the lightest weight gear.

For anyone who is not racing get a plastic boat if you can lift it or a composite boat if you cannot.

Frank, I haven’t noticed such a big
difference between my plastic and composite boats. My “glass” boats make louder sounds over abrasive trash, but the amount of force needed to hunch over the abrasives is about the same. The amount of nasty, scrunching noise also isn’t a real guide to the amount of damage, because poly boats do lose considerable material over oyster beds, limestone river beds, etc. It just doesn’t sound as bad.

So what about flex?
I think the flex (stiffness) has been discounted here. I would think all kayaks are flexing like crazy in waves. The kayak acting like a spring storing some energy and releasing it. If it release it forward – awesome! But backwards or sideways – not so good.

I used to race motorcycles and frame flex would do some wild things but usually consistent in certain turns at certain racetracks. So in theory, I could see that a less stiff kayak, regardless of material, might require more overall energy to get from point A to B.

And on the weight thing: SlimFast + plastic kayak costs a lot less than carbon kayak.

It doesn’t matter…
…whether Warren makes plastic boats or not. You can test other people’s boats or mock-ups to determine the conditions. In the real world, he may be pretty close to the mark, since plastic boats change shape over time and their skins get much rougher than composite boats. There may not be much difference in brand-new boats, especially with the better-made plastics, but the gap will widen as the boats get used and abused.

You have to paddle a really light, stiff
boat to appreciate what a difference it makes. Next best is a stiff, heavy boat, and worst is a light, floppy boat.

Weight has a minimal effect at best
Weight really only affects acceleration. Once in motion, a heavier boat will have more inertia and may even be more efficient than a lighter boat.