I love watching skimboarders catch waves, I also love watching them surf once they’ve caught one. Skimboards are about as close as you could get to a surfboard without rails, heck without fins too. Skimboard surfers seem to do it all with one surface, and aside from a little flip in the nose (I’ve seen a few with a little flip in the tail?) its basically just a flat one. I suspect their weight flexes the skimboard a little once on the wave, but I doubt if thats a really desirable thing, actually I wouldn’t know, I’ve never successively caught a wave using a skim board, I can barely skimboard. Still, skimboarders have taken it to a really pure level… they start with just a single control surface, and unlike surfboards, add nothing. Usually, at least the fellows I’ve watched (video too) don’t hang around long on the face (for obvious reasons?) But still, I suspect there are a few things they’d have trouble doing… like trimming. They can take full advantage of gravity, sort of a sled ride down, and then use the wave to get back to the top, but staying in one line, neither up or down, doesn’t seem to be something they do a lot; they always tend to be falling (they might appear to be trimming momentarily, but my guess is that its a controlled fall of sorts.) Surfboards, or surfers can park themselves in a given position and adjust accordingly to maintain it. Skimboarders seem to constantly be on the move. Actually, maybe I’m giving too much of an interpretation to the style of skimboarders when surfing, after all they’ve usually only got about 3 or 4 seconds before they eat a whole lot of sand. The point of this rant is that, they (skimboarders) do it all without rails, and fins, and a lot more. So what do rails do anyway?
I love watching skimboarders catch waves, I also love watching them surf > once they’ve caught one.>>> Skimboards are about as close as you could get to a surfboard without > rails, heck without fins too. Skimboard surfers seem to do it all with one > surface, and aside from a little flip in the nose (I’ve seen a few with a > little flip in the tail?) its basically just a flat one.>>> I suspect their weight flexes the skimboard a little once on the wave, but > I doubt if thats a really desirable thing, actually I wouldn’t know, I’ve > never successively caught a wave using a skim board, I can barely > skimboard. Still, skimboarders have taken it to a really pure level… > they start with just a single control surface, and unlike surfboards, add > nothing.>>> Usually, at least the fellows I’ve watched (video too) don’t hang around > long on the face (for obvious reasons?) But still, I suspect there are a > few things they’d have trouble doing… like trimming.>>> They can take full advantage of gravity, sort of a sled ride down, and > then use the wave to get back to the top, but staying in one line, neither > up or down, doesn’t seem to be something they do a lot; they always tend > to be falling (they might appear to be trimming momentarily, but my guess > is that its a controlled fall of sorts.) Surfboards, or surfers can park > themselves in a given position and adjust accordingly to maintain it. > Skimboarders seem to constantly be on the move. Actually, maybe I’m giving > too much of an interpretation to the style of skimboarders when surfing, > after all they’ve usually only got about 3 or 4 seconds before they eat a > whole lot of sand.>>> The point of this rant is that, they (skimboarders) do it all without > rails, and fins, and a lot more. So what do rails do anyway? Kevin, For many skimboarders, the template and rails/edges of their boards are used extensively once deeper water is reached. As a side-note, properly tuned, flexible fiberglass skimboards work very well, too. Beginning in the mid-1960`s, my personal boards incorporated outlines that were pulled much longer than their width, a slight 50/50 rail contour in the front, transitioning to a thin-edged panel vee in the tail… both for ease of turning and also because the subtle pull from the vee in the back helps hold the tail in place once the skimboard has been thrown… and as you have observed, a lot happens in less than 4 or 5 seconds.
Dale/Kevin You guys triggered a fond memory…in the mid 60’s my dad made paipo boards out of 1/2 inch plywood. They were about 3 to 3.5 feet long and around 20 inches wide, round nose, parallel outline with a round or pin tail and no rocker. We would sand the edges just enough to keep from splintering, varnish them and head out with our flippers. They were finicky buggahs. They just flew if you set them on the right track and set the edge at just the right angle. If you were off just a little, you spun. Once they were in a track, they didn’t want to change, so you just hung on and went where they wanted to go (at Seal Beach, CA that usually meant over the falls followed by a serious sand grinding). If you could center your stomach over the middle of the board and hold your arms and legs up in an arch with 1/2 an inch of plywood 2 feet long holding you in, you were the King for a Day…
I love watching skimboarders catch waves, I also love watching them surf > once they’ve caught one.>>> Skimboards are about as close as you could get to a surfboard without > rails, heck without fins too. Skimboard surfers seem to do it all with one > surface, and aside from a little flip in the nose (I’ve seen a few with a > little flip in the tail?) its basically just a flat one. Tex Haines of Victoria Skimboards actually puts a little fin box in his personal skimboard for those occasional “beyond skimming” days…giving him in essence a short, round, 1" thick surfboard. Nels
Tex Haines of Victoria Skimboards actually puts a little fin box in his > personal skimboard for those occasional “beyond skimming” > days…giving him in essence a short, round, 1" thick surfboard.>>> Nels Hey Nels (…or anybody else who has got an interest in rails) Here are two diagrams which will hopefully get me closer to offering an interpretation of what might be happening at the rail of a surfboard. At the moment, I’m inclined to view rails as ‘tails’, or at least, its the interaction between wake and rail that matters under most conditions. (Note: I don’t claim ownership of this treatment. If anybody knows of anybody who has taken a similar tact please let me know.) In order to make the point clearly, I’ve composed some diagrams (see below, and next post.) The important bit is that the flow of water is clear from the diagrams. In Diagram 1, the view is looking down at the surfboard from above, the blue line being where the surfboard intersects the face of the wave. The purpose of the next two diagrams is to show the similarity with the flow and trailing edge, in this case, the rail, with what most people might view as what is going on at the tail of the board. The point being that under most circumstances the whole rail (adjacent to the face of the wave) is for all practical purposes a ‘tail’, or at least is subject to wake interaction. Next post…
Diagram 4, which changes the view, now along the plane of the board. Looks at two common rails forms, and suggests a greater interaction might be expected for one form than for the other. It is my understanding that hulls can interact either in a positive or negative way with their wakes. The positive way perhaps being no real interaction at all, as in the case of hard edged rail. Flow does matter, in particular at greater flow rates, one might expect that, in the case of the more rounded rail, at some given flow rate, there would be significantly less interaction. (The hull pulling away sufficiently fast enough so as to avoid interaction.) But we sort of know that maybe rails aren’t that critical given Skimboard surfing, so why not make the whole rail hard and hope for as little interaction as possible? I’m actually begining to believe there are benefits to suffering a little interaction, in particular drag. Maybe somebody can jump in here and straighten me out. (I’m also starting to wonder if this might be why I dislike hydro hulls so much, or at least offer some hint as to why they never managed to perform as was suggested by the theory.) 
Kevin,>>> But we sort of know that maybe rails aren’t that critical given Skimboard > surfing, so why not make the whole rail hard and hope for as little > interaction as possible? From a practical standpoint, efficient planing isn’t always good surfing. For reasons that are probably not related to this excellent model, the hard rail tends to track at speed. That is, once the board is going in a direction, it is very difficult to change. At slower speeds (read; mushy conditions) the hard rail gets the board planing quicker and is a valuable design characteristic. At speed, planing becomes more of a problem than an advantage, yeah, the board is moving fast, but you have difficulty turning.>>> I’m actually begining to believe there are benefits to suffering a little > interaction, in particular drag. Maybe somebody can jump in here and > straighten me out. (I’m also starting to wonder if this might be why I > dislike hydro hulls so much, or at least offer some hint as to why they > never managed to perform as was suggested by the theory.) Drag means control and is the Second Law of surfing. The First Law: flat is fast. The Second Law: curve for control. You just have to take care placing the flats and the curves. Or, with flex, design the amount and location. Newbs