question on reducing skin friction drag on surfboards

I was reading about use of riblets found on shark skin and most recently how dophins reduce drag by shedding their skin every couple of hours. 3M produced some kind Riblet of tape for use on the Stars and Stripes hull but it appears it may be proprietary. Seems like we should be able to learn from natures animals as much as we can. I am a surfer and mainly just curious if any surfboard manufacturers have investigated technology for skin friction reduction techniques during the glassing and finishing process.

-wbart

that seems like something very irrevelant to surfboards because the effects would be so minimal. Its more in the surfer. just like the whole “gloss coat slows your board down” thing. A lot of that stuff is in your head and once you learn to forget about it you surf faster then ever, gloss coat or not. you as a rider learn to compromise what your board has and doesnt have and use it to your advantage regardless.

Friction reducing skins might have ‘some’ positive effect. I know professional swimmers have had some success with these new suits, but then again, we’re talking a fraction of a second over 50 meters. Fine for competitive swiming at the olympic level, but that translates into centemeters at most. Bring this onto the surfing platform, and I’d say that any gains you made could easily be lost by a less than perfect setup and takeoff. Plus, when you’re up and planing not all that much of your board is in the water.

The whole “induced turbulence” through surface roughness has been covered here several times. Not many of us here believe it would help in any way.

That said, I fully support inovation, and would welcome it with open arms. Though, I would need to see results if it would require buying extra material, and having extra install procedures. In the mean time, I have enough to work on in my shaping/glassing that would probably have a much more significant impact on performance.

hmm interesting lunch time discussion…

anyway for what it’s worth, during my scholarly years when I was studing to be a physical oceanographer, I was intrigued about laminar flow and creating some type of “jet assist” bottom. Initially concaves where thought to be the answer as well as air injection. Tom Morey designed the original “fat penguin” when he was on Kauai in the late 60’s early 70’s to use substantial concaves to increase speed. I believe the article was published in surfer magazine back then. If you look at the picture of the windsurfer george greenough is holding on one of these recent posts, you’ll see a board that looks very similar to tom’s attempt at an air injected blaster. According to Morey it was too fast to ride… Brewer also mixed it up with concaves and air including a air injected board with a flap he built for Owl.

Although I didn’t try building one of Tom’s designs I did try his other suggestions…

The first was to apply an entire bottom of soap like was on the bottom center of your board to reduce the surface tension that soap does with water (sure made a mess). This has also been repeated recently with a product sold by Surfco that I believe was actually invented by Paul Strauch…

The second more bizarre suggestion was to crush bottles of Alkaseltzer tablets and apply it to the bottom of your board witgh a thinned out hot coat and then sand the board either just before entry or after paddling out.

Both these crazy ideas definitely got me the mad scientist rep and although they did some stuff it was anything by a factor of 10 or anything like that.

I did study that dolphin skin dissertation and find it revalent but it’s really a combination of alot of things other than just the spongelike skin. First of all is the efficient shape of the animal, combined with the fact that it’s one huge muscle armed with a major paddle in the tail. Most importantly though is that the entire unit(animal) flexes using muscle power to position it’s shape to the most efficient position it needs to be in to to maximise the power it can extarct from the water/bow waves.

Boards just don’t work this way, they are design to counter react negatively or you could say positively against the power source instead of trying to find the path of least resistance…

In Toms article he talked about soft boards (this is pre-boogie board days now) that would bend and flex with the waves power, even capture capture the enrgy and release it like how the flx fins do. Jeff Ho and folks experimented with this in their flex tail designs that are still being done today in pavel/madala fishes.

I think a combination of what Jim Richardson is doing with his Surfflex technology, combined with some new type of skinning material that works like these new swimsuits or even the willis golfball concept would mimic what Tom was talking about way back then. Better yet some form of air injection design.

If someone was real smart they realize what laird them are doing as far as finding a way for the baord to reduce it’s over all surface area exposed to the water as their hydrofoils do… Even better yet maybe some “unobtanium” einstein out there will develop a material that is significantly magnetically unattracted to water that could be applied to the bottom of a board to build a tension free area. You know like the skateboard in back to the future part2.

Anyway to make a boring story short, it’s going to have to be a combination of flex, store and reused energy, and some thing significantly unattractive to water to create a frictionless yet rideable experience. Currently Hydrofoiling and Kite surfing are the only two current comparable experiences.

I got to go now… got a migraine remembering all this stuff. Go find the mag if you’re interested.

Another way of looking at this issue is by means of the rider. oneula, you mentioned George Greenough, who over the course of many years has pragmatically evolved from standing, to kneeling, to prone. Low profile. From one long fin to none.

Due to changes in riding stance, as well as thoughtful decreases in overall area and weight of his equipment, George has been able to achieve significant increases in balanced, wide range control and speed.

But in order for gains in speed to be functional, they must be balanced by corresponding increases in control. To that end, a little give in an otherwise firm design is often a good thing… and a tuned, responsive rocker, flexing with powerful memory, is even better. Less wasted energy equates to more available horsepower.

Incorporate a smooth, wetted bottom and rail surface which intimately conforms to a wave`s curves and surface textures, a design which naturally follows the invisible paths of least resistance.

Create something that effortlessly glides across most any wave, at times both relaxed and tense… like a skimming aquatic muscle.

Then you`ll really have an exciting wave tool with which to go exploring.

Sophisticated simplicity… less is more.

http://photothru.com/photo_filedb1/A5/E7/E4/A5E7E4/viewable/A5E7E4_131CBB0841B_1.jpg

http://www.swaylocks.com/cgi-bin/classifieds/classifieds.cgi?session_key=&search_and_display_db_button=on&db_id=515&query=retrieval

I think there might be something to the riblets. Whales have them too.

Back in the late 70’s / early eighties, I think, some guys from San Diego were experimenting with riblets. At first they cut them into the resin, and it took them forever to do. Then they discovered an easier way. They used pinline tape and then glossed over it. They had them configured so they started about mid-point and extended to the tail, but the riblets got shorter and shorter as they were added towards the rail.

I wonder if it had an effect. A lot of experimental ideas get left behind because they are too difficult or time consuming to make. Does anyone else remember these boards?

Yeah Dale,

I’ll have to agree you guys have got something going there.

Scrolling through the photos on the surfermag forum I believe I even saw a stand up version of what you guys are using. Definitely you folks have got the advantage concerning speed and control and even better how about bodysurfing with one of those full body swimsuits and fins with similar skins using a hand paddle to reduce over surface volume at speed (up at ehukai frosty would know)… That would be dolphin emulation… Bottomline though it’s not the same experience than standup surfing… maybe its better I don’t know… Been there did that too…

Funny B.C. (before leashes) I bet we all were alot better body surfers that are today (At least I was).

Anyway I’ll definite check out your prone and this other stand up solution as a travel option as it’s the best compact surf option out there except for the shark action you’re exposed to in the south pacific.

As far as skins though… as my long term memory returns every now and then, I do remember a guy in the 70’s who sold these mini channel rubber sheets that you applied to the bottom of your board… Again been there did that too. Don’t remember it being anything great. Still think that a fat penguin/gemini (concaves) shape in your blow up material design might be an answer… Jim Richardson’s material in his surfflex boards maybe using “Q” new swizzle design might be another option.

Gotta go

well i got something here …its without a doubt the fastest thing you could possibly ride…i even got an old photo in action…this board still exists in a panelbeaters around the corner …im gonna pull it out and take a close up of it so you can see exactly what im talking about…

this board has holes through it …the holes are covered on the bottom with just a fine slit allowing air onto the bottom of the board …as the water rushes under the bottom it sucks the air through the holes ,at a certain speed (just a little faster than paddling speed , just before you take off) the whole board rises and rides on a cushion of air …

unbelievably fast…

only drama was the air introduced onto the bottom of your board , meant the fins just didnt work when you tried to turn to hard …i was thinking of cav plates at the base of the fins to keep the air trapped against the board …

but the whole process just got to complicated …

im not sure if this photo is clear enought to see the holes…

it was pvc conduit through the board , a slight depression in the bottom with a fine cover over the hole , leaving a slit between the cover and the edge of the depression…

when i find this old board and take a pic it will be real clear…

regards

BERT

oneula,

Well, there are no standup or kneeling versions. You probably saw photos of the ULI (ultra light inflatable) surfboard over in the Surfermag forum.

The surf mats to which I made reference are completely different. They usually weigh about 18 ounces and are laughably supple, yet have a high strength to weight ratio,

designed to operate with very low air pressure, deflated to about 75% (or less) of capacity.

Mats appear wrinkled and baggy until placed in the water and supporting the riders weight. In fact, one means of estimating initial buoyancy is to adjust air until the mat easily folds over 90 degrees on center. Unlike solid prone craft, a mat surfers upper body functions as a support structure.

Once in motion across a wave, mats are under tension, the rocker bending and twisting from pressure above and below, from the wave and riders weight. All contact surfaces begin to flatten and adapt to the waters curves and textures… naturally seeking the paths lines of least resistance.

Top and bottom materials respond independently. Thickness profile also changes, the rear 1/3 tapering down to a thin, flexible foil.

These subtle effects are also influenced by the rider alternately gripping and releasing the mat`s forward edges and corners. This causes instant changes to the internal pressure, altering its shape and flex, having a direct influence on speed and control.

Modern surf mats are unlike any other wavecraft, an active air interface between rider and wave:

"… they have no idea of the hand crafted pieces of art these things are. you almost cry when you unpackage

them… it is art, so light weight they drift in the air like a balloon, not a water sogging canvas slug. no they don’t have sharp lines or rails, they are faster because they are inflated constructs above the water, not on or in. it is NOT an easy medium to master. you flow with the wave’s dynamics, you don’t rip and tear against the flow. also… i love being out of the masses radar…"

Greg Deets

http://photothru.com/photo_filedb1/A5/E7/E4/A5E7E4/viewable/A5E7E4_131CBB01FE5B_1.jpg

Hello Dale, do you know where we can find a video of modern surf mats in action? It would be very interesting for me.

Yesterday i was reading a Surfer Magazine from the 70’s and there was a picture of “Dale Solomonson” on a surfboard advertisement, it was you?

Thanks to you and everyone else here sharing your knowledge.

Does anybody remember the old Morey bodyboards with all the dimples on the bottom skin? Supposedly, the dimples created some sort of air bubbles that increased the speed of the board. Also, think about golf balls; I don’t know the physics involved but everybody uses dimpled balls for some reason. What do you all think?

Dale’s mats are a series of ribs that flex with the wave face respond to it. The mat gets all it’s holding power and directional stability from them without have anything hanging down in the water.

For those of us that what to ride a surfboard Riblets work.

Have a look at my Michel Junod with the Whitside single on it that’s ribbed. Fast and very positive even all the way forward in the fin box as pictured.

How about sanding a board out and then taking 80 grit wet-dry and doing a final sanding of the board with full lenght strokes, leaving the grooves in the board and then sealing it up with an acrylic or resin type auto paint finish. That’s what’s on Trace #1.

Repoorts to follow.

Gone Surfin’, Rich

An easy way to make riblets is to lay a fine mesh net over the surface and apply resin.Then remove net.

I did it to a fin years ago,but didn’t notice alot of difference in slow waves.Maybe in good surf.The

principle is from longline fisherman who wrap a net around their large poly floats to reduce friction in the water so they don’t snap gear in rough sea/current.

Hi Coque,

Brian Taylor is nearing completion of a documentary that will include some of George Greenough`s mat surfing from recent seasons:

http://www.stateofs.com/

http://www.stateofs.com/trailers.html

As for me being in Surfer… I dont recall the example you mentioned, but I have been in there a few times... in Tom Moreys early Boogie ads, a full page of my artwork shown in a section called “Our Mother Ocean”, etc. I havent seen any of that in many years. I wish Id kept all of my old issues!

I remember Sunset Surfboards shaper Nick (?) McMann had a thing called “micro grooves”. Sounds a lot like what you’re talking about.

There were some hawian guys making boards called phasers???. they had dimples like a golf ball but only 6 or eight I think (saucer size). theyv were supposed to work .

Rich,

The basic holding power of my surf mats comes from curve in the bottom and rails. Primary directional stability comes from nearly straight lines over the length, with several rounded contours across the width. All are variable, continually sculpted by the wave`s face and its surface texture. Mats operate best when minimal effort is applied.

But heres the catch: unlike photos of solid boards, display pics of fully inflated surf mats are not at all representative of how they appear in motion across a wave. Theyre two completely different things.

This type of surf mat is designed to function with very low air pressure, actually looking laughably baggy (thus the fond nickname, “Trashbag”) until the rider lays on the deck. In fact, one way to properly estimate air volume prior to surfing is to inflate until the mat can be easily folded on center to 90 degrees.

When surfing, a mat`s exaggerated bottom curves softly flatten, width increases, rails tend to become thinner, taking on the angle of the wave face, become more egg- shaped, and the thickness profile (esp. on the inside back 1/3) tapers down toward the tail.

Edge control can be maintained at increasing speeds (even over chop) because surf mats maintain a substantial contact area with the water, even when banked over in hard turns. Sort of like a radial tire flexing through fast corners.

The bottom material and internal structures are quite supple, offering little resistance to exterior pressures… unless the rider so desires. Instant changes to internal pressure are achieved by simple exterior pressure, freehand squeezing and/or releasing of the mat`s front edges and corners. These actions result in modified flexibility, template, rocker, thickness profile and rail contours…

all directly influencing a balance of speed and control.

Plus, after a period of use, my surf mat’s bottom material readily takes on a thin, slippery coating of water… just like a smooth, wet stone.

Hope that helps…

I saw one of these golf ball divot boards. Except they were about the size of baseballs. Only maybe 1/2" or so deep with about 8 or so on it. The first I saw it I was like WTF is that. I figured it was some far out idea. There as some young grom riding it so I don’t think he had it custom made…probably a second hand board.

we used to see those when I was a kid, early 80’s, along with all sorts of channel configs, and a “cross channel” setup, where soft round edge channels parallel with each rail in the rear third of the board crossed in the middle, creating some sort of ripple pattern…

Here’s an experiment…

get an old beater,

ride it to get familiar,

place towel on bottom,

take back end of screwdriver and carefully push even round pressure dings into bottom,

hot coat to seal cracks,

voila! golf ball bottom!

test, etc.

wells

I saw Tom Morey’s air-bottom board in person, must have been in the late 60’s/early 70s, in Kona. As I recall it was about mid-seven feet long, not an unusual diamond tail shape for the time, with a stepped bottom feature about 3-1/2 feet from the tail. The tail section was “higher” viewed from the side, and there were two large air vents there, and corresponding holes in the deck. I’d guess in theory it worked, but did anyone ever see another one?

Yes I did, a six-footer with a concave full length bottom, with a series of small steps and multiple airholes at each step. Some hippie had it, he may have made it himself or gotten it from another backyard builder. He said it worked, but again, his credibility was variable and again, did we ever see another?

Hell, there’s another one: last week I stripped an assymetrical-template, old windsurfer hull which had a concave bottom with two one-inch diameter air vents. It was given to me a decade or better ago, I never knew who rode it. I recently ran into the girl who gave it to me, but she didn’t remember the hull. Only thing to say for it is that it was strongly glassed, and I’m making a 7-0 from it, will hot coat it tonight.

Golf ball dimples work on the principle that induced turbulence allows separation to happen sooner, leading to less drag. This is fine for a golf ball traveling at high velocity (air viscosity compared to golfball size), but I don’t think much of the idea for surfboards. Study up on the uses of Reynolds number, Froude number, dynamic similarity for more info on this in any college level fluid dynamics class. For me that was CE 320, taken in, oh, 1974 or so.

Hobie cat racers were at one time advised to rough sand the forward 1/3 of their wetted hulls for the same reason. Generally the photos of America’s Cup boats, on which more money is wasted than any surfboard, seem to have smooth, mirror-finish hulls but this may change. Again, a minor reduction means a long lead in a race that’s miles long, but surfboards seldom ride far enough to make a difference. Who’s going to appreciate that your board can get from takeoff to pullout one second faster?

I’ve see the dimple-bottom boards and diss them. It takes energy to change the direction of water flow - the fastest board should be the one which least disturbs the water at operating speed. “Operating speed” is a critical concept here, though a fast/easy paddling board is nice too.

All in all, I think surfboards commonly used are going as fast as they ever will, give or take a little bit, and only a major change is going to produce more speed. The hydrofoil boards show promise for speed, (Hobie cats have done this too) but no one’s turning them much, and look what the “takeoff” power requirements are…