Physics of Keel Sucking

Yesterday I paddled on the local lake. My friend was paddling my loaner boat and we were getting a workout back to the put in. I got on his wheel… I mean keel, and tried a little drafting. He was up to about 5.7 mph according to the GPS and pushing a lot of water out of the way. I put my bow a few inches off his stern and I swear I was only putting out a 3 mph effort to stay on. I have never gotten such a good ‘draft’ in my kayak. My questions: Does a heavier paddler provide a better draft/surf? Does a faster boat provide better also? Those are the two variables that came to mind.

are you a biker?
the guy in front is cutting thru the resistance and the followers coast into the draft. taking turns is considered polite. a team can go faster than a loner

it’s just like biking … yet different.
when you draft on a bike, the guy in front is cutting the wind resistance. in a kayak, the guy in front is cutting the water resistance. as for the physics … dunno. it works though, as any biker can tell you.

Couldn’t tell you about the physics
other than the fact that the front boat was eliminating your bow wake and leaving you with only a stern wake, giving you in escence a little wave to surf “down hill”. I’m not sure if there is a real advantage between longer and shorter crafts, but I have some idea. I’ve played with drafting a bit with Coffee and Northman whom both have less than 10’ boats, and they seemed to have an easier time drafting my 14’ than I them. It seems logical that the bigger the draftee, the more pull drafter would would recieve. I seem to recall Lindabaron saying she once rode a ferry wake effortlessly for a very long time.


Hey there Wheel sucker…
just like the train behind that Burley tandem!

Lots of fun and fast!

I have on several occassions down in some of those spring rivers in Florida got on the wake of those tourist pontoon boats, and have stayed at around 7 MPH without much work for a half a mile or so.

On one occasion on the Chassahowitzka River after the captain saw me he started easing the throttle up a little until he dropped me, and the gang of people on the boat were all yelling for me to paddle faster.

Lots of fun!


Hey Jack
This guy I was following was about 210 pounds and pretty dang strong. Burley tandem is right!

Seems like someone posted that you could surf off another kayaker by paddling behind and to one side… in the wake. Is that true? I couldn’t find that sweet spot yesterday.

As longshadow
said. Bigger boat in front will make a smaller boat draft well. same principle as ducks,geese,biking or race cars. It was much easier drafting a big boat ya gotta get close and stay tight to draft off the boat I was follwing.

I’m sure it’s the same

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for kayaks as it is for my canoe experiences. You can wake ride the stern wash (in canoe races you'll get splashed deliberately and heavily) or wake ride the bow wave of the other boat off to one side. It was harder to stay on the bow wave. It's really more surfing than drafting. And, like your refence to bike racing, you're expected to take your turn in front for a spell. I would expect a higher displacement boat to be easier to wake ride due to more volume in the wake. I wouldn't think boat speed capabilties would make much of a difference, other than the displacement factor. Faster designs would create less wake, so I guess it would be easier waking an OT Disco as opposed to a J boat, but they ride those speedsters' tails or bows all the time.

Check out for some
drafting tips… pretty cool…

The following boat still has a bow wake… drafting is not good enough to change laws of nature. Then no one would lead.

Dang it guys, stop sounding like big box sales people … it’s Cycling. Bikers ride those noisy, obnoxious, pig-like two wheelers that only go straight…

Lead, follow or get out of the fast lane.

Greg Barton…
teaches a four boat diamond draft, rotating positions…

Now all I need are three more boats… GH

Im in with one…
does that include airfare for me & freight fo the boat?

here’s a theory…
i don’t think it is “draft” … water is sticky - and following a kayak (as in this example) disrupts the surface tension of the water - making it actually easier to paddle through.

Just ask a water stider!

Those guys REALLY suck…!

Only out there they do definitely NOT

Paddle on!

-Frank in Miami

Water has mass, hence it has inertia when it is moving.

Water also has viscosity (stickyness).

As the lead boat moves through the water there is friction between the hull and the water (this is drag). The drag resists the forward motion of the kayak. If you recall Mr. Newton’s laws about “equal and opposite forces”, this means that the boat causes some of the water around it to move in the same direction that the boat is moving.

The trailing boat is moving forward in the water that is already moving forward. Its the same as paddling with the current.

Also, I think that the wake created by the lead boat will be smaller when there is a trailing boat than if the lead boat is alone.

This is because the trailing boat will “absorb” some of the energy that would otherwise cause the wake to form. I think this will only happen if you are in the right spot (the “surfable” side of the wake). The extra energy gained by the trailing boat will also reduce the paddler’s effort required.

I would suggest that Bernoulli’s thoery

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applies here. That is the same theory that explains why a sail boat sails, a plane flys, a curve ball curves, and for Magoo, how a snow fence works.

The front boat is pushing the water away in the front and creating a difference in pressure between the water in the front of the boat (air in front of a bike or car). There is an area of lower pressure in the back. Therefore, the effort required to overcome the pressure is reduced.

That's my story and I'm sticking to it.

Thanks was very helpful. The arthur doesn’t spel too good, but he seems knowledgeable about tactics.

I do it all the time behind John Boats, if you can catch the Wake/wave its like surfing down hill, and it works great, but get on the back side of the wave and its OVER! BTW boat control gets real squirmy when you are surfing a power boat wake/wave. as the wave kind of piles up into a point, when you start hitting that point its like balancing on a needle, then you slid off the back or side and usually loose the wave. Think of a Triangle coming off the back of the boat with one point to the rear and up about 15 degrees, the other two points are at the left and right power boat stern. I would think BIG Fat boats would be easyer to “draft” behind, just like a Big Fat truck is on a Bicycle. Only on a boat you are riding the displacement wave.

When I used to Water Ski
We always preferred to fall inside of the wake. Outside the wake felt hard and really stung, while inside it was like falling on a pillow. Somehow the water that’s been churned up is easier to cut through.


More surfing than drafting
Your are riding on the longitudinal wave train, so it is surfing - on low and often barely visible waves. They are 90 degrees to the keel and run in the same direction as the boat. Transverse waves (wakes) can also give a ride.

To really work either, a rudder really helps (and that’s coming from a skeg boat driver). Another big reason racing kayaks have rudders.

The wavelength created by a kayak is longer at higher speeds. Place to catch it depends on lead boats speed and following boats LWL. At hull speed, wavelength = LWL so an equal length boat would have to follow pretty close, almost touching or even a bit forward and off to the side. The more overhang - the more overlap - the harder to get in close and work the wave in that speed range. Another reason for plumb bows in racing.

The lead boat is in trough #1 of their wave train, and if you are right on their stern you are in trough #2 (assuming speed close to hull speed) and getting a push from the crest behind you (your own waves can’t push you since you are pushing them). Easier for short to draft long in that situation, as a shorter boat could back off a little. At lower speeds you may be getting the push from 2 or 3 crests back. At higher, it stretches out and the sweet spot backs off.

The diamond draft formation allows boats to move up and back at various speeds and stay on the waves. Also give room to maneuver. This positioning works with 2 boats or more.

Heavier displacements should mean more energy to catch. Behind larger powerboats, in the flattened area astern between the transverse waves heading out to the sides off the bow, you can sometimes see the rolling longitudinal wave train. On these, ride a few troughs back! You can get a push off the transverse waves out to the sides too, but a it harder to stay with unless you turn with them.

On rivers here I’ve drafted the longitudinal wave (and taken advantage of the loose water astern) behind slow moving powerboats, then cut inside on turns and get over their wake to get another bit of push off it (the transverse waves), then cut back in behind for the free ride aft again on the other side. Pass them using their own wake, and then fall back behind every turn. Good fun.

And when CBs were in vogue and we were foolish high schoolers, we used to get “permission” from truckers to draft on the freeway. Had to get very close but the effect was very noticeable.

Do not try this in your car.