Thoughts on Surfboard Volume, Rider Weight, and Paddling Speed (part 2)
As a continuation to my last article I went and conducted a follow-up experiment on the paddling speed of various surfboards. My primary goal was to compare different shortboards of the same length but different volumes to see if the boards with increased volume offered increased paddling speed to match.
Here are the boards I tested
Doug Haut noserider. Dimensions are 9'6"x3 1/4"x24". This wasn't the sort of board I was primarily trying to test, but I thought it'd be interesting as a comparison.
5'10" Stretch Fish (the green board). This board's dimensions are 5'10"x2 1/2" x 21". This was intended to be the shortboard with the highest volume (more on the different volumes in a minute).
5'10" Tyler Karaszewski shortboard (the white board). This is a board I built. It's dimensions are 5'10" x 2 9/16" x 20 1/4". It has a volume of 33.5 liters. This is the only board I actually have a decent volume measurement for, as most board builders don't provide them. I'll estimate the volume of the other boards later in this article.
5'10" Ward Coffey shortboard (the orange board). Dimensions are 5'10" x 2 7/16" x 19 1/4". This board is the smallest I had available. I would have liked to have an even smaller one, like one of the Channel Islands signature pro model boards. Something in the neighborhood of 5'10"x18 1/4"x2 1/8". This would have filled the role of the "potato chip" pro board quite well, but I didn't have any boards like that to use.
Myself. 5'11" 29 year-old. Decent swimmer. Yeah, I swam the same course I paddled, just for comparison.
I used the Santa Cruz Wharf at Cowell's beach as my test track. I measured the distance between two sets of pilings under the wharf at 16', so I could use that as a reference point (note: I couldn't do this for the portion of the wharf that's actually above the water, but it seems that the pilings are all evenly spaced for the length of the wharf). I chose an section of the wharf spanning nine sets of pilings, and therefore containing eight 16' sections between them. This gave me a test course 128 feet long. I figured this was a good approximation of the distance one might paddle trying to catch a wave, even a bit on the high side. I was more interested in testing boards in a sprint to catch a wave rather than in a long-distance sustained paddling situation.
I tested each board in order. I chose the order of boards so that I'd test the most buoyant boards first, which would hopefully keep me from getting too tired at the beginning. Also, I hoped that any fatigue developing during the test would serve to accentuate any differences between paddling performance of the board, rather than making them all seem to paddle at closer to the same rate.
Because I knew that I'd get tired during the tests, I decided I'd do two runs with each board, and I'd do the second set in the opposite order as the first run. The order in which I did the tests was:
Haut, Stretch, Karaszewski, Coffey, Swim, Coffey, Karaszewski, Stretch, Haut, Swim.
You'll notice that I didn't stick to the reverse ordering for the swim test, instead doing one swim test after each group of boards. I decided to do this after the first swim test, because I realized it was by far the most tiring test, and I thought that doing two swim tests in a row might affect my performance for the remaining tests more than I'd like. Since I was more interested in the surfboard tests than the swim tests anyway, I decided to sacrifice swim test accuracy for more accuracy in the surfboard tests.
Each test consisted of two legs. A 128ft paddle sprint out away from shore, a short break, and a 128 foot paddle sprint back to shore. I started the beginning of each test a distance away from the actual shore to try to minimize the impact of any wave action on the tests (the waves today were very small to begin with). I started each leg from a stop, with my eyes lined up down a row of pilings, laying on my board. I'd press start on my watch and sprint to the 9th row of pilings, when I'd stop the watch. All results were truncated to the nearest second.
For each board switch, I got a break of two-three minutes, but these breaks weren't timed. I aslo got a longer break after the first swim test, during which I conducted a floatation test to attempt to determine the volume difference between the different shortboards (more on this later).
Paddle Test Results
The following two tables show each test result in the order the tests were carried out.
Set one. All values are in seconds, rounded down to the nearest second.
|Board||Outbound Leg||Inbound Leg|
Set Two. All values are in seconds, rounded down to the nearest second.
|Board||Outbound Leg||Inbound Leg|
This Table shows the average time and speed for each board over all tests.
|Board||Average Time(seconds)||Average speed (mph)|
Note that all three shortboards came in at almost the exact same speed. There was more difference between individual runs for each board than there was between the average for each board. None of the shortboards are clearly faster or slower than the others.
The longboard was noticeably faster than the shortboards, as was expected. It was 24%, or 0.92mph faster. This was significant, but maybe not so much as many people would have expected.
The shortboards were also significantly faster than swimming: 13% or 0.44mph. One interesting thing to note here is that paddling a shortboard is closer in speed to swimming than it is to paddling a longboard (but not nearly so tiring).
Volume Determination Tests
Because I don't have any actual volume measurements for any of the boards except the one I built myself, I attempted to estimate the volume of the other two shortboards based on the height at which they floated me in the water. I measured the level at which I floated in the water on each of the three boards. It must be noted that these measurements are quite inaccurate, due to constant motion of the surface of the water, and so they're simply gross estimates. I found the board I built floated me highest, about 1/2" higher in the water than the Stretch, which was counter to what I'd expected. I also found that the Coffey floated approximately 4" lower in the water than the Karaszewski board (or about 3.5" lower than the Stretch).
If I measure myself with a tape measure just below the sternum, where the water level was while performing this test, I find I have a circumference (assuming I'm circular) of 33.5". This means I have an area of 89.3 sq. in. Assuming that my density is equal to that of water (which is close to true), then each inch higher I float in the water, implies 89.3" cubic inches of extra surfboard volume under me. 89.3 cubic inches works out to 1.46 liters.
The Karaszewski board has a known 33.5 liters of volume, the Stretch board has approximately 32.8 liters of volume based on this method, and the Coffey has approximately 27.7 liters of volume.
I could not use this method with the longboard, as it floats too high in the water to be comparable. Instead, I used surfboard design software to design a roughly similar board, and calculated a volume of 80.4 liters, which is the best estimate I have for the volume of the longboard.
Thoughts and Conclusions
The difference in volume between a "high" and "low" volume shortboard made almost no difference in paddling speed, which is not what I had expected. Additionally, the speed advantage of a longboard over a shortboard is less than I would have expected based on a "gut feeling" from paddling around, where it seems the longboard is probably 50% faster or more. Also, the difference between swimming speed and shortboard paddling speed is surprisingly small.
This leads me to wonder if the main advantage of a longboard over a shortboard for wave catching isn't paddling speed, but rather a lower speed threshold for when a board begins planing. The speed required to keep a hull planing over the water is proportional to the weight of the vehicle (board + rider) divided by the surface area of the bottom of the board on the water. Since a longboard with rider weighs only very slightly more than a shordboard with the same rider, but has about twice the area, it should be able to get up and plane at a much lower speed. Since the speed at which a surfboard moves (above the approximately 4.75mph that it can be paddled) is gained by "falling" down the face of the wave, a longboard can hit it's planing speed on a much flatter wave than a shortboard, this means that it can catch waves much longer before they're ready to break. Also, the 25% advantage in paddling speed comes into play in giving the rider more flexibility to adjust his position to best catch a wave, but I believe that might be secondary to the planing effect. Maybe this will be a subject for a future experiment.