Author Topic: Heavier Boards Faster?  (Read 23216 times)

LaPerouseBay

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Re: Heavier Boards Faster?
« Reply #30 on: November 04, 2010, 12:09:43 AM »
I did a quick calculation on the increase of wetted surface area from a fiberglass to a plastic SUP. Let's assume it's a 14' x 30" SUP, and that the glass board weighs 25lbs and the plastic board weighs 50 lbs. The extra weight causes a 1% increase in wetted surface area (~0.35 square feet increase). Since drag is linearly proportional to wetted surface area, the increase in drag is 1%. Seriously folks... how many people would notice that?

As others have suggested, this is very easy to test.  

Tape some weights to your board.  Ten pounds will be plenty.

Use a GPS if you have one,  but it really isn't necessary.  

In my opinion, this subject is too complex for math.    

Reduce the variables by using the same board, conditions, paddler and percieved effort.

Paddle hard, paddle easy - it matters not - average speed will be lower.  

Seat of the pants testing will convice you.  I'm sure of it.
« Last Edit: November 04, 2010, 12:44:35 AM by LaPerouseBay »
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LaPerouseBay

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Re: Heavier Boards Faster?
« Reply #31 on: November 04, 2010, 12:38:56 AM »
Continuing with the cycling analogy, it is well accepted that the combined weight of bike and rider are really what matters when determining power to weight ratios...  In other words, a light bike will make climbing easier, but taking 10 pounds off your bodyweight (while maintaining the same power output) will have approximately the same effect as losing 10 pounds from the bike (and probably a lot cheaper!).  The point is that you have to consider total moving weight.  Same thing with SUP.  Do you really feel that you would be faster if you strapped a 30 lb weight to the center of your board?  I sure as heck don't.

Excellent points ref.  My ass-o-meter tells me that climbing and paddling are very similar - countless little accelerations.

Back to your climbing analogy.  As you are aware, (but failed to mention probably for brevity) racers modify their bikes for climbing stages.  They use fragile, light weight wheels and add more weight to the frame (16# limit).  

Wheels move more than the frame does.  Removing weight from the outer edge of a wheel is 4X as efficient as removing weight from the frame.  Reducing the wheels' angular momentum is the key to those countless little accelerations.  Wheels and  boards - the most dynamic part of the puzzle  
« Last Edit: November 04, 2010, 01:15:23 AM by LaPerouseBay »
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blueplanetsurf

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Re: Heavier Boards Faster?
« Reply #32 on: November 04, 2010, 12:45:12 AM »
Putting weight on top of the board will not feel the same as having the weight distributed evenly inside the board and will also make it more unstable.
I agree that using a lighter board is noticeably faster, which is why I don't use that heavy Bark anymore.
Robert Stehlik
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Mitchell

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Re: Heavier Boards Faster?
« Reply #33 on: November 04, 2010, 08:38:11 AM »
For some reason i still feel that there is "to light" of a board and there must be that perfect weight.

I understand now that the more weight is more wetted area and that buoyancy is relative to mass and weight is also relative to mass so yeah my bad LOL.

And adding 10 lb thing to your board does not "feel" the same as using a 10 lb heavier board.

I just wanna make it clear that im not disagreeing necessarily that lighter is faster but i think there is a point where lighter becomes not as effective.   

robon

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Re: Heavier Boards Faster?
« Reply #34 on: November 04, 2010, 09:39:12 AM »
This turned into a really informative thread. The "wetted" area comparison makes sense as does friction. I have noticed a couple of analogies that I don't really agree with. Putting a ten pound weight on a board or whatever is not the best analogy as it doesn't represent the weight of a heavier SUP being distributed throughout the entire board, and not just in one spot. I have 10 pounds of gear with me on almost every paddle and when I don't, the difference isn't noticeable. What about buoyancy?

I noticed one example stating that a lighter SUP decelerates faster, which makes sense to me. This could bolster the momentum argument once a board is up to speed. Not completely sold on this though. There is a good reason it takes a loaded semi truck much longer to slow down than an unloaded one, or a typical passenger vehicle. The larger, heavier truck carries it's momentum longer than lighter vehicles. I'm not saying this carries right over into the SUP discussion but some of the variables make sense.

I have also read more than once now that a heavier SUP handles better on rough water and wind, thus making it easier to keep tracking straight. Flat water will be a little bit slower to get to speed, and a bit slower overall.

It really seems that unless your a racer, the biggest draw back is just getting the heavier board to the water from your vehicle. In the future I hope to have a range of boards including heavier plastic roto moulded designs and traditional designs. I am wondering how boards that are significantly heavier feel in both traditional and plastic designs. Is that walking on water feeling still there, or does it seem you are paddling a boat?



« Last Edit: November 04, 2010, 09:45:57 AM by robon »

refthimos

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Re: Heavier Boards Faster?
« Reply #35 on: November 04, 2010, 09:46:49 AM »
What i am trying to see is if newtons law applies to aid us in the fact that "something in motion wants to stay in motion" and over time saves us more energy than having to deal with "something at rest wants to stay at rest" if that makes sense...

I will defer to the physicists in the crowd here, but I think there is this "fallacy of momentum" that in moving an object on level ground (in this case, water), heavier is better.  As someone else stated, we see in just about every other sporting discipline out there (running, cycling, skiiing) that absent going downhill, lighter is faster.

If this "momentum advantage" were really true, wouldn't we see, all things being equal, heavier cars getting better freeway MPG?  Put this another way:  drive your favorite "wide-open" 100 mile route by yourself, then drive it with three passengers and a trunk full of luggage.  If there were really a momentum advantage, wouldn't you find yourself faster over that same route with your car weighed down?  You won't.  There will be an increase in rolling resistance (the SUP is similarly affected by more hydro resistance), but more importantly, it takes more work to move more weight over time.  Same as a wheelbarrow.  Is it easier to push when empty or when loaded up with 100 pounds of bricks?  That "momentum advantage" isn't doing you much good there.  More weight, more work.

robon

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Re: Heavier Boards Faster?
« Reply #36 on: November 04, 2010, 10:14:15 AM »
I'm not seeing momentum so much as an advantage, but rather the ease of keeping at a good cruising speed once you get the heavier SUP going from a stand still.  Does momentum help with punching through the chop and pushing through a headwind? Some of these examples are getting a little extreme now. Putting a weight right in the middle of the board, which doesn't accurately reflect weight distribution at all. A filled wheel barrow? Momentum in the terms we are referencing is in regards to once the SUP is moving and slowing down. A loaded car doesn't reflect this well at all imo until it is slowing down, which you would see the loaded car take longer to stop than the same model that is unloaded. I realize that a loaded car takes more work to move, but it is still an example with unbalanced weight distribution. An SUP is long and narrow. A car is short, compact,  with a weight bias in the engine and then a huge amount of weight from several occupants distributed over a very small area. An SUP's weight is distributed through out it's length and it is much more streamlined.

How much work does it take to move a heavier SUP over time? Is it like moving a filled wheel barrow vs an unloaded one, or is it more akin to burning an extra 25 calories over a few hours of paddling? I don't think there is much of an argument here regarding a heavier SUP being less efficient over the long haul. It's how much less that is interesting to me and it seems pretty small. The momentum argument is interesting though and it seems that most who have paddled significantly heavier SUPs, state that once up to speed, the energy expenditure is not huge.


« Last Edit: November 04, 2010, 10:34:39 AM by robon »

sailsport1

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Re: Heavier Boards Faster?
« Reply #37 on: November 04, 2010, 10:46:50 AM »
Interesting. I do think the car example is a good one. It is well proven that a lighter car gets better milage.

For plastic boards you also need to consider the stiffness. Touring kayaks are an example. A stiff board (or kayak or boat) will glide through the water much better. The flex is using up energy. If you could make a rotomolded boat that was as stiff as glass and not too hard to load onto a roof rack, then you would have something.
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pdxmike

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Re: Heavier Boards Faster?
« Reply #38 on: November 04, 2010, 11:00:24 AM »
The roto-molded boards could help answer this whole question.  You could test one, then fill it with sand or water and test it again.  That would take away the argument that putting weights on top isn't convincing because the weight isn't distributed evenly.  The board would also be exactly the same otherwise, except for the weight, so the other variables would be gone, too. 

Another idea along those same lines would be to take an extremely light F18, ride it to become familiar with it, then smear layer after layer of fiberglass over it until you had doubled or tripled its weight, then see how it felt then compared to before.  Not that anyone would ever do that. 

kwhilden

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Re: Heavier Boards Faster?
« Reply #39 on: November 04, 2010, 02:49:07 PM »
With that said, I have no way to verify your calculation that adding 25 lbs of weight increases drag only 1%, but it just "feels" like that is not accurate.  If I go from my current weight of 195 to 220, and am unable to increase paddling strength, it just "feels" like I am not going to go only 1% slower.  Similarly, if I stick a 50 lb weight on my board, am I really going to be slowed only 2%?  100 lbs, 4%?  OK at some point we are going to sink this board! Haha.

In the interest of being clear... I calculate that DRAG increases by 1% with a 25 lb increase in weight at non-racing speeds, because wetted-surface area increases by 1% for a standard 14' SUP shape.

All else being equal, more drag equals slower board. But in the real-world, a heavier board has a minor negative effect on speed for the average person, and may actually be beneficial in rough water conditions.

Regarding the car/bike analogy given here. I can easily think of a situation where a heavier vehicle is faster than a lighter one. Instead of a smooth surface, put big bumps on the road, and make the heavier car due to the addition of larger wheels and bigger shocks. :)

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blueplanetsurf

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Re: Heavier Boards Faster?
« Reply #40 on: November 08, 2010, 11:27:12 PM »

As others have suggested, this is very easy to test.  

Tape some weights to your board.  Ten pounds will be plenty.

Use a GPS if you have one,  but it really isn't necessary.  

In my opinion, this subject is too complex for math.    

Reduce the variables by using the same board, conditions, paddler and percieved effort.

Paddle hard, paddle easy - it matters not - average speed will be lower.  

Seat of the pants testing will convice you.  I'm sure of it.
[/quote]

LaPerouse,
I have been thinking about this subject a bunch and will do the real world experiment you proposed tomorrow morning but not seat of the pants, more like a science project.  I know putting weights on top is different but it should result in something to work with.
I'm attaching a a picture of the setup:

12'6 Amundson board- I chose this one because it is stable enough to handle 30 extra pounds.  It weighs about 30 lbs, so adding 30 lbs will double the weight and should make a measurable difference in speed.  GPS and Go Pro cam taped to board:  I'm planning to record the speed on the GPS with the camera to see how the weight affects acceleration/ deceleration and top speed.

I will post the results here shortly and am planning to write a more detailed review on my blog.

The plan is to paddle the board first without, then with weights on a timed half mile course and a 400 ft sprint (flat water with light wind predicted for the morning)
I figure the difference will be more noticeable on the sprint as fast acceleration is key and plays a bigger role.  On the half mile course slower acceleration will play a smaller role.

If results are inconclusive, I will do several rounds of testing over several days.

Any suggestions or predictions?
Place your bets:
How much slower do you think the board is with 30 pounds dead weight on top? (in percent- sprint vs. half mile)
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
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pdxmike

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Re: Heavier Boards Faster?
« Reply #41 on: November 08, 2010, 11:43:16 PM »
blueplanetsurf--wow, that's initiative!  My first thought was that you're going to eliminate all the fun of arguing about this topic, but then I figured we'll all argue over what the results mean and whether they're valid anyway. 

I say 15% slower for the distance, and 20% slower for the sprint.

Next you can do an experiment to answer the question of the balance bracelet, and after that the "what's the best thing to eat or drink for performance" question.  Then the 14' vs. 12'-6" question, then the long vs. short paddle question, then the Kialoa vs. Quickblade, then the Surftech Bark vs. custom Bark, then the this fin vs. that fin...
   


blueplanetsurf

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Re: Heavier Boards Faster?
« Reply #42 on: November 08, 2010, 11:48:55 PM »
pdxmike, wow that was fast.
All good ideas but one thing at a time    :)
Robert Stehlik
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blueplanetsurf

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Re: Heavier Boards Faster?
« Reply #43 on: November 09, 2010, 12:04:05 AM »
I did a video test,  the speed on the GPS should be easy to read.
Board weight/ speed test setup video test

Anyone other predictions?
Robert Stehlik
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PonoBill

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Re: Heavier Boards Faster?
« Reply #44 on: November 09, 2010, 07:59:36 AM »
Good test. I'd start with the weight at the center of balance and then check it in the water to make sure it's not affecting trim. If it's tilting the board front or back, slide it until it doesn't. Shouldn't take much. the center of balance is not necessarily the same location as the center of buoyancy
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