How pirogue/canoe weight affects glide

[jdupre']

Everyone wants a light boat. They are easy to handle and quick to maneuver. But for long distance paddling at a comfortable speed, wouldn't a little extra weight help with the glide between strokes because of the extra momentum?

For instance, if you made two quarter scale models of a pirogue, one out of wood and the other out of Styrofoam, and gave them a equal push through the water, wouldn't the wooden one glide farther?

I worked in a sugar mill loading and moving rail cars around. When the small dummy engine would push the cars out on the spur and unhook while moving, those cars would go a long way before stopping even though they were only moving 1 or 2 miles an hour. A car pushed 2 mph will stop rolling much sooner. :idea:


Joey

 

[Kayak Jack]

How much wetted surface did those rail cars have?

Your answer is yes and no, but mainly no. Yes, a little more mass for more momentum helps. But it's more like pushing a heavy rock uphill and a light one uphill. A guy pushing a heavy rock doesn't appreciate the uphill momentum very much.

More weight (along with boat design) gives more wetted surface. Friction between boat and water will slow it down more than the extra momentum will sustain it. Besides, it takes more energy to get it up to speed (acceleration).

Go light.

 

[Jimmy W]

I agree with Jack. A heavier boat will sit deeper and give more drag and you will have to push more water out of the way as you paddle. A heavier boat will have more momentum, but there is also more inertia to overcome to get it up to speed.
A rail car with steel wheels on steel rails has less rolling resistance than a car with flexible rubber tires, but a heavier boat has more resistance than a light one.

 

[seedtick]

All that theory sounds good and may even be correct but let's do a reality check here.

Time we put in a cooler of beer, a handful of turkey necks, anything else we may need, then roll our studly body into the pirogue, we.ve got a total package that weighs well over 200 lbs. Check out that wetted surface and I'll buy anybody lunch if they can tell the difference paddling in a 40 lb pirogue vs. a 60 lb one.

Within reasonable limits, design is more important than weight.

 

[hairymick]

I agree completely with Seedtick.

Canoes, pirogues and kayaks, generally speaking, are displacement hulls. The weight of the boat will have very little effect on its glide capability. By displacement, I mean the weight of water that the loaded boat has to push aside before it will float.

Boat speed and glide are controlled in a displacement hull by how effeciently the boat manages to push that weight of water aside as it moves through it. ie . a pirogue and a kayak may well be of the same hull weight and displace the same weight of water but the kayak will glide much further through the water than a pirogue. It will also require less effort to make it go forward. This is entirely due to the boats shape.


Good glide is created when the boat shape allows it to pass cleanly through the water with as little resistance as possible. There is a mathematical rule of thumb for establishing a boats designed displacement speed. That is when a displacement hull will achieve its designed hull speed for the most effecient us of power pushing it.

 

[Jimmy W]

I'll admit that design is very important, but the original question seemed to be dealing with two pirogues of the same design. If you take the two models and give them an equal push as stated, the lightest one will gain more speed and I believe it should glide farther. Adding a cooler of beer might make the paddling more enjoyable, but will not make it easier to paddle.

 

[jdupre']

The way I look at it, a light boat is obviously easier to get moving because there is less mass. But between strokes, when the light boat is decreasing in speed due to water resistance, the heavier boat is not decreasing as fast because of it's momentum. I would guess in a day's worth of paddling, there is more "between" than actual stroking.

Ever try to stop a heavy boat when it's gliding in to the dock? Not easy.

Most of this water resistance theory has to do with maximum hull speed. Unless you are a glutton for punishment, you would not be paddling a pirogue for very long at maximum speed. At a leisurely 3-4 mph, a hull acts very differently. In fact, if maximum speed enters your mind, a pirogue is probably not the boat for you.

I'm not saying my theory is correct, it's just an idea that I wanted us to throw around.

Joey

 

[hairymick]

G'day Joey,

Most of this water resistance theory has to do with maximum hull speed.

Not really mate.

As I understood the question, it was about glide between strokes.

The point I was trying to make is that glide, comes from hull efficiency through the water. The less friction that water imparts on a hull, the further it will glide and the less effort to make it go forward is required on the paddlers part. This is why I like skinny boats.

I believe total weight will play a part in glide but it is only a small part compared the the ease with which a hull will slip through the water.

If the question was aimed soley at pirogues, I think the same principal applies.

If two pirogues 15 feet long were propelled with the same power in the same conditions and with identical rocker on each boat, but one was say 100 pounds heavier, the heavier one would probably glide a little further.

Now take those two pirogues, with all things being the same except bottom width. The skinny one will glide much further because it attracts less friction from the water it is passing through.

 

[jdupre']

G'day Mick. I like 'em skinny also- as skinny as I can stand and stay upright.

 

[oldsparkey]

Didn't some guy a long time ago say that the greater the mass the greater the inertia of that mass. Or in plain language the heaver a item weighs the longer it will take it to stop. "O" and also to get it moving.

Chuck.

 

[a Bald Cypress]

glide

Y'all have got to go back to school and re-learn some things.

Two boats, both made to exacting specs. One weighing 100 lbs more than the other will glide at the same speed as the water is flowing.

If ya has ta paddle to move the boat, y'all are going in the wrong direction.

 

[Kayak Jack]

OK, let's step back a moment here. Take one boat, and one boat only. Say it is a flat bottomed pirogue. Empty, let's say that it weighs 50 pounds.

For measurement purposes (no cracker barrel philosophy here) we will take it to a facility that can generate water flows at various speeds. Let's say that we set the speeds at 3 mph, 4 mph, and 5 mph. We will attach a spring scale to the boat and measure resistance to flow as we hold the boat steady in one location, as the water flows past it.

What ever the scale reads at 3 mph, it will read about double that at 5 mph. The 4mph reading will be closer to the 3 mph one that to the 5 mph reading. IE: as a boat speeds up, resistance builds almost geometrically, not in a straight line as may be expected.

Now, add a 20 pound weight to the boat at the center of gravity so the boat's trim is not affected; it just settles a bit lower into the water. ALL THREE SCALE READINGS WILL INCREASE. PERIOD.

Would a paddler be able to tell that? As Keith suggests, no. Would he be able to tell it at the end of a day of paddling? You bet. But, Keith, I wouldn't paddle all the way back just for a lunch. Would have to be something better than that, say scotch.

Increased resistance will more than overcome any benefit of added momentum in the glide. Our results, by the way, would be exactly the same with a canoe or a kayak. Just with different numbers.

 

[jdupre']

Jack, I agree that the resistance will be greater with the boat sitting lower in the water- more wetted surface. I just figured that the increase momentum would allow the boat to maintain more of it's speed between paddle strokes. If, between strokes, the heavier boat slows from 3mph to say 2.8 mph , whereas the lighter boat slows from 3 mph to 2.6 mph- the paddler would not have to make up as much speed on the next stroke. But, the next stroke would be pulling a heavier boat forward. Result- no advantage to extra weight.

But, it still intrigues me that a super ocean tanker, from full speed takes several MILES to stop.

Joey

 

[oldsparkey]

For what it is worth .........

I don't know if this will help but it is something I found interesting about the weight or items a person has in a boat.

One of my trips down in the Everglades we had to take all of our water with us. That was 12 gallons , one gallon for everyday.
Mine was in two 6 gallon containers in the boat , a canoe.

As the trip progressed and the water decreased the remaing water in the containers would slosh with every paddle stroke , it would actually help move the boat forward when the forward movement from the paddle was between strokes ,out of the water. Plus it wanted to resist the forward motion of the canoe when I would take a stroke with the paddle.

Now on a larger scale , you have a super tanker with tons and tons of liquid on there , they want to stop or slow down , they have the ship to slow down and they have the cargo (weight) to slow down. You have to remember they are going faster then we paddle so all that weight is use to moving at that speed and it does not have any breaks , the vessel does , it doesn't.

Again ... The old adage , A body put into motion tends to stay in motion.

chuck.

 

[Kayak Jack]

... As the trip progressed and the water decreased the remaining water in the containers would slosh with every paddle stroke , it would actually help move the boat forward when the forward movement from the paddle was between strokes ...

Now THERE'S an interesting phenomenon. If your timing was correct - paddle at the same frequency as the slosh - it would help. What happened, Chuck, if you paddled a bit slower or faster? I'll bet when it got out of synchronization it was a bear!

Joey, an ocean liner has not only more mass is the ass, it has a much leaner profile than one of our boats - particularly if that boat is a pirogue. Aspect ratio (ratio of length to width) is way ahead on one of those boats. Large ore boats on the Great Lakes are a quarter of a mile long! And those boats (ore and liner) have nearly a million horsepower driving them up to hull speed.

If we could devise a way to accurately measure the force we apply with a paddle - other than how loud we grunt or fart - we could use GPS to establish speed and glide. Wind, however, will affect glide distance more than weight or design. Both for good and bad.

I turned thumbs down on a boat that weight about 14-48 pounds. It had a Mylar skin over 1/4" balsa wood network frame. You can get too light. I vetoed aluminum canoes just as quickly - grossly overweight tubs (that are loud and cold). (Yes, I know, they can take a helluva beating. So can an anvil.)

Within bounds of strength and reason, go as light as you can. You can be happy once buying a bargain, and kick yourself in the rear every time you use it. Or, you can feel regretful once buying a quality item, and smilingly pat yourself on the back every time you use it. We have choices.

 

[jdupre']

I was doing a little research in boat design when I came across this interesting article. Sounds very plausible to me.
http://www.roguepaddler.com/weight2.htm

I did notice that my pirogue seemed to paddle "easier" overall with my wife along as a non-paddling passenger. She's about 100 lbs. with her PFD on. We also had an extra seat, lunch, ice chest, water,etc.

Joey