1 down 99 to go!
We await your results
Tiny bubbles and the direction of sanding: In one of the America’s Cup races Dennis Conner’s syndicate played around with an adhesive film that was supposed to duplicate the skin of a shark. Apparently a shark’s skin has very small grooves running lengthwise along it’s body. Can’t remember if it was used on the boat used in the actual races - I think it was when he challenged and won the Cup back in Australia.
Good stuff from George there Dale
George’s boards generally stay in deep contact with the water at all times. Though planing, like a surfboard, they don’t leave the water nearly as often as a surfboard does.
One thing we need to consider in this whole discussion, is how much predictable and regular contact the contemporary surfboard has with the water.
If we are consistently breaking that contact, then many of the ideas and theories regarding attached laminar flow, that are appropriate for many hydrodynamic applications, may not apply properly on a contemporary surfboard. Of if they do they may only apply to a fairly small part of the board near the back that is experiencing a somewhat greater amount of regular or predictable flow that we can then design an ideal surface finish for.
It the board, including the whole bottom including fins, is regularly breaking contact with the water we may find a finish type that breaks contact or releases the water the easiest, to be something to pursue.
This finish might be Hydrophobic and like a good car wax, repel the water. Allowing it to break away at a split second so that no more wetted surface is dragging along with the board.
Or it might be Hydrophilic such that it allows a thin wetted film to stay with the board, but due to the high surface tension of the film and ocean water, allows the ocean water to break off easily from the wetted film once it hits a certain stress point.
To visualize this, have you ever been glossing a board when you run a puddle of resin up over the existing gloss resin that is attached to the board? If you have done it, you will know what I mean. The puddle or chunks of it will fly off of the board like they were shot out of a gun! They are gliding on the surface tension of the underlying gloss resin, the puddle parts, skate over the top of the existing glossing resin like they were being levitated as they rocket off the board. The release is extreme and the acceleration and lubrication effect would be wondrous to harness in a finish coating that worked that way in conjunction with the ocean’s surface and the boards finish.
More importantly, this freedom of the ocean from attachment to the board, would allow the board to be moved in any direction with much less resistance, such that it would make the board feel lighter and able to be flicked around at will in any direction without having to… ever so slowly… nurse the attached water flow in a new direction and give it plenty of time to know where it is going next. In contemporary surfing that is way too late as the surfer or wave will be requiring another change before the first one is even finished.
Of course, at this point in surfing, some degree of attachment or drag is necessary to retain control. So dual finishes on different parts of the board might be exactly what the doctor ordered. Or at least till we learned to handle more speed and freedom and less control and drag.
Aloha Ted
I am aware of this material. It is used among other things on the inside of pipelines to keep the fluid moving in a linear fashion near the pipe walls to reduce turbulence and therefore drag.
It has been used on surfboards and Yachts. It hasn’t, to my knowledge, proved successful.
Bill, I’ve been wondering if anyone was going to bring up the clean water to foamy water and back, over and over again, reply. This is not a shallow subject once you get down to the finer points.
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1 down 99 to go!
We await your results
Uhhhhhh, can we get more takers before I gloss my board? Hehe…
Hahaha. My results are on record from the start. Obviously they are wrong, are just not too popular. Number 98?
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It the board, including the whole bottom including fins, is regularly breaking contact with the water we may find a finish type that breaks contact or releases the water the easiest, to be something to pursue.
This finish might be Hydrophobic and like a good car wax, repel the water. Allowing it to break away at a split second so that no more wetted surface is dragging along with the board.
I’m hoping that you are also including the radical changing angles of attack that high-performance surfboards normally go through.
A very interesting discussion. Here’s my take on the subject. Most of the sanded bottom thinking is about sanding in a certain direction, in line with the stringer, inline with toe-in, cross hatch this way or that way. I personally like sanded finishes on the bottom for a lot of the reasons listed above, but here’s what I do with no thought or theory behind it but just because it seemed right. The bottom of my boards are hand sanded wet with 600 grit in a swirl or circular pattern. The reason this now makes sense to me is from reading this discussion. It seems that most sanding methods are perceived in a linear thought frame, whereas it doesn’t appear to me that at any given time is the bottom of the board and the surface of the water going in a straight line except maybe for paddling. And my brains might be full of seaweed, but that’s I see it.
Ride on, Tom
Good point. Just so I can understand fully what you are talking about, are you talking about a hand sanded swirl pattern (big circles), or a machine swirl pattern like the DA I use with finer grits (smaller circles), or maybe tiny circles that would come from a vibrating orbital type sander? I don’t even know if it would matter. Just curious.
ozzy,
Medium hand swirls, 3"-5" diameter approx.
Ride on, Tom
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Tiny bubbles and the direction of sanding: In one of the America’s Cup races Dennis Conner’s syndicate played around with an adhesive film that was supposed to duplicate the skin of a shark. Apparently a shark’s skin has very small grooves running lengthwise along it’s body. Can’t remember if it was used on the boat used in the actual races - I think it was when he challenged and won the Cup back in Australia.
I think you’re on to something there. I remember the media hype about that race many years ago. Do you remember what year that was?
Aloha CMPHawaii
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Bill,Did you ever glass any of the Willis Bros boards?
Yes I think we did some at ProGlass. It is not commonly known but Michael Willis was one of my ghost shaper for my boards to Japan, as were a few other “well known” shapers.
If I recall correctly, the Phazer idea came from an engineering friend of theirs who also developed the little machine tool to easily shape them into the board.
SNIP
isn’t the sanded finish pretty much standard for the majority of boards these days? Has anyone ordered a polished glossed bottom for hydrodynamic reasons??
True the sanded finish is pretty standard these days but I don’t think many people order a sanded finish for hyrodynamic reasons anymore. And very few board makers do sanded finishes for hydrodynamic reasons. They might give lip service to it being a “faster finish” but everyone knows it is done because it is cheaper, lighter and faster to produce. The claims of improved performance were simply added on after the fact, to excuse the huge drop in quality and cosmetic appeal that the boards were going to take being being produced with sanded finishes.
We all know the struggle to get the sanded finish to look cosmetically acceptable. No one likes the streaks and no one has a good solution for getting a consistently blended matte finish without getting streaks.
Consequently, most have went back up to 320 grit just so that they can hide the swirls and edges of the sanding pads passes. These are purely production choices with very little concern for actual performance. Other efforts to eliminate the visual tracks all begin to add back so much trouble and cost that it would be nearly as easy to just gloss and polish the boards.
SNIP
Talked to a hyrodynamic engineer one time who told me that until you reach 35 MPH the percentage difference in different bottom finishes are incrimental. Having done a bit of sailboat racing myself the difference between first and second in many races is just seconds over a course that can be an hour long. That would mean that the incremental difference would matter. Tested some of these things on sailboards … same thing. If I could get a boat length extra on my buddy over a ten minute leg I was stoked. But percentage wise that’s NOTHING…001%. On a surfboard you’d never feel it. Having said that, I have tried numerous finishes on boards over many years and my conclusion was the same as GG. Always 400 wet and dry “feels” the best to me and it didn’t seem to matter the pattern. Some of the rougher “speed sprays” I liked too. Gloss is awful.
Greg, would the fact that the surfboard is more of a flat planing craft with sudden bursts of acceleration (instead of a deep V hull) make any difference, or a mulitplying effect of any kind? Or does it not matter?
Surfboards are probably the slowest planing hulls there are. That does make them unique. Acceleration in comparison to other planing hulls is probably pretty minimal unless you look at in terms of percentage. The biggest thing IMHO is that surfboards aren’t quantified. Everything is subjective which many times leads to personal and sometimes wrong conclusions. Again what I was told was that until 35 MPH it matters much less than 1% which is nothing really. My comment on feeling that 400 wet and dry “felt” the best is totally subjective and isn’t quantified in any way. This whole thread pretty much makes that point. It’s all just feel which would have innumerable variables as to ones final opinion. I’ve made my opinion on personal scientific method testing (trial and error) and my results may not relate to anyone else on earth. I will say though that without thorough scientific method testing, opinions are total BS.
Ok, makes sense. But maybe all of our opinions and personal rudimentary testing put together may add up to something. Maybe not. I don’t know. But it sure is fun hearing all the different points of view.
Personally, I like sealing a board with a lightly textured finish. But as Bill was saying, that is more for construction reasons, e.g. – for appearance and to help hide small sander swirlies and stuff, because I’m not that hot of a finish sander. But I am also wide open to trying new things and being ‘swayed’. Pun intended. haha
how come this was never settled ? hmmm
I read somewhere That a few engineering students and Physics students that also happen to surf are doing some real scientific studies on the hydrodynamics of Surfboards. Lets be honest most of our knowledge about surfboards is subjective. How a boat under sail moves thru water or how a power boats gets up to hull speed in different then how a surfboard operates in the water.
Even if science came up with a scientifically perfect surfboard the one factor that will always be there is the very imperfect surfer.