What's faster?

General Discussion
61

“obviously no one equated down the line choppy point break with the mat”

**Discussion/photos of choppy point waves have been included in past threads and photos.

“lets take two craft, a mat and a hard boogie board of similar size , so they both have the same surface area”

**Unlike a hard boogie board, a surf mat’s surface area is adaptable, i.e. an 18" wide mat can become 24"… all dimensions (even length) are subject to change by wave

and/or rider.

“if one is flat and the other has rocker, flat will be faster with no rider effort, so there design plays a role”

**There’s a third option… a bottom and rails that are shaped by the wave, formed by it’s actual curves and textures, is more efficient than imposed flat or rockered.

Flat may sometimes be faster, but (the third option) will offer more control.

“lets say they both have the same bottom curve and area, then given the same wave and power they should do about the same speed, having equal amounts of viscous drag working against them”

**The boogie board’s basic bottom and rail shape cannot change, while the mat is constantly adapting itself to present the least drag and inefficient design in active contact areas. Plus, the bottom surface of a mat retains a thin sheet of water in contrast to that of a boogie board.

“a mat will not transfer the full force of the chop right thru the craft to the rider, so by absorbing impact it also weakens the negative vector forces working to slow us down”

**A surf mat can often be seen passing over bumps, with the bumps passing under and out the back, nearly undisturbed.

“everyone always trys to tell me that a light board doesnt work in big waves with chop… then people say if you go too light a board it doesnt work in any waves… [but it’s all about] transfering needed or useful energy and absorbing or not transfering negative energy”

Yes! Beautiful words, Bert!

"i know for a fact greg knows exactly what im talking

about… hard decks flexible bottoms… look past the obvious"

**A surfboard’s “hard deck” is the rough equivalent of a

mat surfer’s body.

62

Benny1…

I used DuPont Hypalon and catalytic adhesives (as well as other materials, i.e. rubber, neoprene, PVC, etc.) over 25 years ago. Average weight of my early mats was about 5 to 6 pounds. Current average weight is 18 to 20 ounces.

My thermal welding involves high strength-to-weight ratio mil-spec 400, 200 and 70 deniers, non-permeable polyurethane coated nylons. I work with these materials between about 350 and 950 degrees.

I use no glues. My thermal welding replaced resins and adhesives beginning in 1982. From the 1970’s to 1982, all my mats’ seams/internal structures were joined with industrial grade contact adhesives, nylon monofilament and/or flexible resins.

Yes, I custom make all my own valves. They’re hand-poured epoxy, formed in polyvinylsiloxane molds, then machined.

63

Very, very cool. I was a pro rafter from 87-96. Did some prototype testing for SOTAR out of Grants’ Pass and then Hyside out of Kernville. Took mini SOTARS down some pretty tight first decents. Breathed enough MEKP working with hypalon to never want to use anything but epoxy on surfboards. Saw the light when we started heat welding PVC in about 89. Sounds like we should have paid you a visit. :slight_smile: I worked with McGuinness / Cassidy / the Carlsons / the Grants for the most part, if you’ve ever done freshwater time. I’d love to try a mat one of these days, I’ll eventually have to scrape together the $ and just do it. Anyone using them in rivers? The carlson board is pretty flexible, but a mat might be even better. I used to boogie the Kern on a Morey with a helmet & kneepads & a cup at low water, so I’m happy with my face down & head front…:slight_smile:

64
Quote:

No doubt the penny will eventually drop and people will actually start to measure speed via gps. Statements like “I know that no one can go faster than this guy at my local beach” would be so much more interesting if we had mph figures to go with them.

Here’s over 40 GPS measurements of speed (over the bottom), but I don’t know how anyone can draw any meaningful comparisons from the list since a lot depends on the wave size, break, swell direction, tide, board, and rider. For example, the person/board combinations at the top of the list also appear near the bottom of the list.

What one needs is a controlled environment–e.g. waves that break nearly identically from wave-to-wave, and with measurements made as “simultaneously” as possible (i.e. on sequential waves, or at least multiple rides before the conditions change very much).

Rank Date Spd(mph) Type

1 1/25/05 26.9 shortboard (Surf approx. 2X)

2 3/16/05 25.5 kneeboard

3 1/25/05 24.4 shortboard

4 3/12/05 24.0 kneeboard

5 12/18/0 23.4 shortboard

6 3/12/05 23.3 kneeboard

7 12/19/0 22.9 shortboard

8 3/7/05 22.6 kneeboard

9 2/1/05 21.7 kneeboard

10 12/10/0 21.3 kneeboard

11 1/28/05 21.3 kneeboard

12 10/21/0 21.2 kneeboard

13 10/28/0 20.8 kneeboard

14 3/15/05 20.6 bodyboard

15 1/21/05 20.6 kneeboard

16 1/30/05 20.3 kneeboard

17 11/12/0 20.2 longboard

18 3/1/05 19.9 kneeboard

19 2/2/05 19.7 kneeboard

20 1/20/05 19.6 kneeboard

21 1/28/05 19.6 shortboard

22 12/11/0 19.5 kneeboard

23 3/3/05 19.4 kneeboard

24 1/31/05 19.4 kneeboard

25 11/5/04 19.1 kneeboard

26 9/22/04 18.9 bodyboard

27 8/29/04 18.7 bodyboard

28 8/18/04 18.4 bodyboard

29 9/20/04 17.9 bodyboard

30 8/17/04 17.9 bodyboard

31 8/27/04 17.8 shortboard

32 12/25/0 17.6 NA

33 9/28/04 17.4 shortboard

34 12/15/0 17.4 NA

35 12/12/0 17.3 kneeboard

36 9/5/04 17.2 bodyboard

37 10/31/0 16.9 NA

38 9/6/04 16.9 bodyboard

39 12/15/0 16.8 shortboard

40 10/1/04 16.6 bodyboard

41 9/25/04 16.5 bodyboard

42 9/25/04 16.3 shortboard

43 11/1/04 16.3 NA

44 3/15/05 16.1 kneeboard

45 9/29/04 15.2 shortboard (Surf approx. thigh to waist high)

Meidian 19.5

 Mean   19.6

Std. Dev. 2.7

65

Hello MTB, thanks for those measurements. It looks like 26.9 mph is what we are currently aiming to go past.

66
Quote:

Hello MTB, thanks for those measurements. It looks like 26.9 mph is what we are currently aiming to go past.

I don’t consider that to be a very meaningful number other than an indication of the speed that might be achieved on an approximately double overhead wave. If the surf conditions were identical to those existing during the session when that number was recorded, I think it would be improbable if the same rider and board would record anything close to the same speed (e.g. being able to defensibly differentiate between the two highest speeds in this data set, for example).

By way of an example, one kneeboarder recorded a (max) speed of 21 mph on a wave early in his session. All his subsequent rides–until almost the end of the session–produced equal or slower maximum speeds (i.e. the max recorded speed was not increased). Then on one wave just before the end of his session he recorded a max speed of 24 mph. Hence if he had stopped just a couple of waves sooner, his max speed would have been logged 3 mph slower than it was.

This is a basic problem with measuring “extreme” (e.g. low probability) events such as the maximum speed achieved during a session. What would probably provide a more meaningful value is to record and save the max speed achieved on each wave ridden during the session, then use a more robust statistic such as the mean (or median) speed of the data set as the measure of the speed potential of the rider/board combination. However, it is difficult to get riders to do this since it requires some additional (data handling) effort on their part (vs just strapping on the GPS before they go out, then removing it when they come back in), and it is not presently clear how many waves would have to be ridden to yield an acceptable uncertainty in the accuracy/representiveness of this statistic.

The data set in my previous post also includes accompanying information on the: break location, wave data (sig. ht., period, heading–from nearshore buoys and direct observation), tidal stage during the session, specific rider/board combination, etc.–but for legibility and simplicity this was not included in the post. The only general conclusion that could be inferred from the data was that–as might be expected–larger waves tended to be associated with higher speeds. But the scatter around that relationship–even forthe same rider/board combination–was very large. One of the factors that was observed to potentially affect the speeds achieved, but could not be quantified, was the effect of crowds in the line-up. Hence defensible comparisons between board/rider combinations would seem to be rather unlikely with this approach.

My view is that the primary value of this data set is that it provides an approximation to the typical range of maximum speeds experienced by a competent rider on a decent board in the conditions present at some of the better breaks in the San Diego north county area over the course of a year (although admittedly the measurements only encompass an 8 mo period). Hence one may be able to use this information in estimating the corresponding range of speeds and other hydrodynamic factors (e.g. Reynolds numbers) when examining/assessing the hydrodynamic characteristics of a surfboard and/or its associated appendages in these conditions.

mtb

67

There’s been a bit of talk about flex vs stiff, but I think there is also another angle.

The common surf craft generates vertical lift by re-directing water down (planing forces) and by water displacement. I’m going to ignore horizontal foils (in MTB’s kneeboards and Roy’s long wooden surfboards) which re-direct water down with a different drag/lift relation from planing craft. Consider the mat vs bodyboard or paipo. Both ridden prone.

The stiff board is going to preserve an angle of attack throughout its length, and generate a lot more lift through planing forces than through displacement.

Now, planing forces necessarily transfer more forward momentum to the water than displacement forces. The reactive moment with the water will move water down, but it will also move water forward. So, working towards minimizing the lift from planing will work towards drag reduction as well (ceteris paribus).

So it is entirely possible the mat is so dern fast because it allows the rider to assume a posture with minimal planing forces, and maximal forces from displacement.

68

thanks for taking the time to answer, I can definitely understand where you’re coming from and respect your thoughts/trip!

Just FYI, I have never seen a photo or footage that has captured anywhere near the potential or feel of a mat or flexspoon on a good wave- and I’m a babe in the woods at surfing either!

But yeah I love TSJ and am on my second 2 yr subscrip!

As for not signing my real name- it’s just my personality I guess. I’m weird like that!-never signed my name or put a logo on any of my boards/dont have surf stickers on my truck etc. I’m not selling anything/don’t care about a reputation (nothing against the craftsman who do as I have learned heaps from you all)

Its amazing all our differences- you have ambrose the poet and mtb the statistician- and they both love surfing on insane levels!

Good waves to you and thanks again for the positive reply.

69

Hi MTB, Roy asked me if I would post this for him so I said yes, I hope no one minds.

"Hi MTB. Without a strictly controlled environment, it will help to record speed more often and thus have more readings. A higher than average (for a given session) speed will occur regularly . . some sessions the highest speed will be closer to the average and during other sessions the highest speed will be further way from the average.

It depends upon what one is trying to do with the information. Some goals which are well served by readings of highest speed without a controlled environment would be:

  1. A personal highest recorded speed (irrespective of wave type or board ridden)

  2. The highest speed during a particular ‘heat’ in competition.

  3. The highest speed achieved on a particular board.

  4. The highest speed achieved at a particular break.

There are countless other possibilities for meaningful speed goals. Strictly controlled environments are not necessary.

In surfing competition , there are already statistics which are treated as meaningful even though they are not recorded in a strictly controlled environment. When someone scores a 10 in a heat, it is taken to mean something, and in the same way, if a highest speed is recorded during a heat then it can be taken to mean something too, even if it just means who the winner on the day is!

There are always going to be ifs buts and maybes, and that’s cool. By recording speed often and regularly, meaningful and entertaining information will be the result"

70

It is also possible that the mat is able to generate lift from planing at a better lift/drag ratio than a rigid hull is able to, rather than because it avoids planing lift in favour of displacement lift.

Emma Stewart ( In collaboration with the Power Surfboards staff)

71

“The common surf craft generates vertical lift by re-directing water down (planing forces) and by water displacement. I’m going to ignore horizontal foils (in MTB’s kneeboards and Roy’s long wooden surfboards) which re-direct water down with a different drag/lift relation from planing craft” (Blakestah)

Why are you ignoring horizontal foil area? If you do that you are not just ignoring MTB’s and Roy’s craft. You are also ignoring such ‘common’ surfboards as the three fin thruster and the bonzer, both of which gain substantial lift from horizontal foil area. Emma Stewart

72

hoiw mush does a mat cost high quality that is. i want one now more that ever, i have one of the old ones from th3e 60’s in my beach house attic . the only way to test is with wond tunnel typre stuff be my geust to invest and invite me over for the testing.

73

Benny1,

Many thanks for sharing! I’m always fascinated by the diverse backgrounds of Swaylocks members!

You are right about working with materials such as Hypalon. Exposure to their associated solvents and adhesives can be very hazardous, especially over the long term.

When working with PVC inflatables, do you use (RF) dielectric sealing, ultrasonic welding, direct thermal sealing, or induction welding?

Thank you

74
Quote:

Why are you ignoring horizontal foil area? If you do that you are not just ignoring MTB’s and Roy’s craft. You are also ignoring such ‘common’ surfboards as the three fin thruster and the bonzer, both of which gain substantial lift from horizontal foil area. Emma Stewart

Roy, I wanted to draw a direct comparison between boards comparable in size. Mats have no fins, the most direct comparision is to a similar size, stiffer, board that also lacks fins.

The use of horizontal foils is something far more complex, and MTB and you know far more about it than I do.

“Better to keep your mouth shut and be thought a fool than open it and remove all doubt.”

75

Whenever I’m “diametrically opposed” I use a good laxative.

76

Hi Blakestah, actually it was me, Emma, but I understand your mistake. I am a surfboard design nut also!

Did you give any thought to the other possibility regarding mat speed (that it is possible that a mat can generate planing lift at a better lift/drag ratio than a hard bottom)?

Horizontal fin area is a strange one if you think about it long enough. For example, even a fixed single fin will have horizontal fin area whenever the board is rolled onto the rail.

All boards with fins will thus use some horizontal fin area for lift at times.

So really it’s happening all the time, it’s just not formally recognised.

77

Hey Emma

I just noticed you are a Jouneyman, shouldn’t that be Journeyperson/woman.

Hicksy

78

When I get to be Barnaclewoman then you owe me 6 beers (delivered)

Don’t forget.

Emma

79

I had to reread most of the last half of the thread to get on track with the "horizontal lift " ,most confusing {oximoron} ? … , then as I was reaching the end I realized that the mat application wasn’t exclusive of this "horizontal lift "

how is this you might ask but the articulation of the trailing fins on the feet forcibly pressed to the wave suface make for this lift effect,although I am tempted to call it veertical,

…Am I clarifying the dynamic you are talking about or confounding it,are you distinguishing lateral and vertical or is this horizontal a third lift dimension?

at what point on the changing wave face might we identify the change from the vertical to the horizontal?

  • the trough the lower face the mid face th upper face the underlip the lip and the lip lid are areas of wave currently frequented by many wave riding forms which of these is the domain of verticality and then again where does the elusive horizontal appear? is this a static term refering only to the relationship of the resistance foil-lifter to the board/craft riding surface? the art of clarifying terms is the key to communication of Ideas.To obscure the information into codified jargon would serve to accelerate the obscurity…

…ambrose…She had been go mo fas when no mo da fin afta had broke …good fun…

80

THIS IS KINDA WHAT I WAS DRIVING AT…

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