400km 5 Day Ultra Marathon - Plastic boat potential?

Hi people,

I’m new to paddling, but not new to ultra marathon events (cycling, Ironman, running).

I’ve read a fair bit of plastic vs fiberglass conversation and it seems clear that plastic is the slowest material to compete in for flat water. I haven’t however found any reading that has quantified how much slower plastic is. I have read posts on this forum suggesting that “plastic and fiberglass will see you complete 20 miles at the same speed but with different energy levels” (the physics of this notion doesn’t seem to add up… to sound like a cyclist for a second, If you put 200w through the paddles of both materials, one will surely be faster??). What I’ve tried to find on the internet is a study that suggests, “in a controlled environment, a carbon boat can maintain this speed with this much power supplied, a glass boat can… and a plastic boat can… etc”. But I haven’t had a whole lot of luck.

Anyway, I’m sure some of you guys can help! This community seems to be the standout authority on kayaking globally.

My situation…I’m undertaking a five day 404 kilometer river marathon in November (the river current speed is probably modest, not fast). The kayak I plan to use is a Riot Brittany 16.5 (5 meter, 30 kilogram touring sea kayak). It’s a battle axe no doubt, but assuming I’ve done my preparation, will I have a chance of completing this event? Or more clearly articulated, will this boat be 10% harder to ride in than a fiberglass craft of the same length… or 20%, 30% etc?

Any advice is VERY welcome.

Thanks, Brad.

Materials matter only if both are unscratched. John Winters has stated you lose 10 percent of speed potential with significantly scratched bottoms that impede water flow. And most plastic hulls are already a little bumpy from manufacture.

But I don’t think this is important in your case. You are new to paddling and river reading skill can help you out; faster current on the outside of the bend of a river potentially a reverse eddy on the inside no matter how still the river looks

And you need to refine your technique to use your core muscles not your arms as the engine. Pick your paddle carefully. Too heavy a swing weight is going to be more tiring. I would guess the paddle and you are the two most important components. Some paddles are designed for acceleration and others for cruising ( don’t get to speed as fast but keep it there after at speed)

Keep the skeg down on straights and up on curves. Learn to edge the boat away from a turn so it carves rather than skids. Study forward stroke videos to avoid yaw( common if you carry the stroke too far back)

Sure you will have a chance of finishing! Perhaps quite respectably. And the most fun ought to be from competing! PS your kayak is decent design… Might not be the fastest hull design but no dog either


I’ll assume that by ‘plastic’ you mean rotomolded polyethylene, and its biggest drawback is weight. Using the bicycle analogy, imagine racing on a 50-pound cruiser vs a 20-pound road-racing machine. Accelerating extra mass requires extra power expenditure from your body, and a heavier boat will cost more, not just to get it moving but also to turn it.

If this river course requires a lot of maneuvering in turns and around obstacles, you might think of getting a boat that’s not only lighter but shorter and more nimble. If the course is mostly long straight stretches, stay with the longer boat; it will track and glide better.

If there’s a chance you’ll be hitting rocks, poly’s strong point is its toughness; it withstands bumps and scrapes better than many other materials.

In any case, read all you can find about reading currents, and get out and practice your paddle strokes and maneuvering techniques on moving water.

Good luck!

I think the bigger reason on fiberglass verse plastic speed wise as there are designs in glass boats not available inn plastic. Take a look at the design of the Epic 18X kayak made for speed. There is a plastic boat that looks good for speed BUT I have never paddle one its the P&H Valklyrie https://www.phseakayaks.com/us/kayaks.php?model=valkyrie

The difference between poly and composite (including woodstrip) is in rigidity.

The more rigid a kayak the smoother it will travel through the water. This is mainly because of the flex in less rigid boats. That flex wastes energy and makes the boat less efficient. That means more work for you.

Can you do a 400K ultra marathon in a plastic boat? Yes. Is it the best choice? No.

I used to own a Cobra Eliminator. Cobra uses one of the densest plastics around and has little flex. The boat still could barely break 5 MPH. An Olympic trainer in fiberglass with almost the same configuration is capable of 6.5 MPH.

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Thanks people - this is very helpful information!


Great tips on working with the river and the boat! Thanks.

What is the event and where?

It’s the Massive Murray Paddle in Victoria Australia.

Here’s the official website: