Water Movement From Behind (pic)

General Discussion
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By playing devil’s advocate on wrap theory you are making us think which is good. Although I am a wrap believer I don’t know if the bulge is from wrap or displacement or both. However wrap theory fits just about every aspect of modern rails - edges, down rails, thich rails, pinched rails, boxy rails. So thats why I believe that some wrap is going on as well as other things. I am open minded as to whether it is responsible for the bulge.

I remember in school I asked the physics teacher how they knew that electrons orbited the nucleus of an atom because no one had actually photographed the electrons doing that. The teacher said that experiments and measurements indicated thats whats going on.

Rider feedback and many years of boards being built a certain way isn’t quite as solid as physics atom theory, but its enough to make me believe wrap theory.

 

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Thanks for the extra pic MrJ, it reveals a bit more.

 I cant categorically say that theres no Wrap but like your physics teacher I see lots of evidence that  show theres no wrap in this pic.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/me2tmsBMP.jpg[/IMG]

 1. The board ,a hull, is in the wave. Any wrap would be occurring underwater.If it was skimming and there was clearly a spray angled backwards, up or around, that would show wrapping.

 With any object moving thru the water and breaking the surface, the water is going to build up on either side.

 2. With the water building up on either side and with the board angled, displaced water escapes from the outside rail as spray released above the surface. However on the inside rail, the displaced water is pushed down and to the side into the face and forms a buildup on the inside rail. As seen above.

 3. Looking at the bump, the bump appears smooth indicating no redirection of flow but does indicate a higher pressure and compression whereas wrap would show spray and release.

4. The bump appears to instantly occur at the foremost contact point with the inside rail and water, so theres no angled wrap.  Unless wrap occurs instantly and redirects gallons of water up and over with zero spray.

 The bump appears to be of a massive volume and up to 12"  away from the rail. Is it all attributed to wrap ? That'd be amazing if it is !

5. The board is not only angled but turning to the right, so as the board moves forward its also rotating into the wave from left to right.

So (relative to the board) the water under the board is actually travelling the opposite direction (from right to left) under the board,  so theres higher pressure on the inside rail because the board is turning into the wave.

 How can water wrap around a rail its being forced against ? In MrJs' pics the wrap is seen as it exits off a rail not as it enters.

 Try spraying water ON to a rail,  instead of OFF a rail.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/p1010046_previewspray.jpg[/IMG]

 You cant claim wrap on any rail if the water flow is from the same side.

 If anyone can disprove my theory, Im keen to learn why.

 

 

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they couldn’t print it if it wasn’t true.  (that was a joke, but the pic is not.)

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Surffoils, I don’t see any point in spraying water on to the rail, I think flow is from under the board going outwards, not inwards. Centrifugal force is causing the board to be scraped over the surface to the left. UPSurfboards says it looks just like skimming a paddle behind a boat - water moves from under the paddle outwards, not inwards.

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duplicate post

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I don’t see a theory, what is it?

67

this experiment also inspired by Craftee’s original streamer demonstration. Performed today in good waves. I didn’t have a water camera so just looked down at the rail when surfing. Pics below are dry land demonstrations of what I saw. The ribbon position pics are looking down on the deck. At no time did I see the ribbon disappear underneath the board, but I wasn’t looking all the time. The ribbon was always stretched straight when I saw it.

I encourage others to try it. The shiny purple colour is easy to see, although I won’t take responsibility if anyone gets their rail bitten by predators.

[img_assist|nid=1050929|title=curly ribbon taped at hull rail tuck|desc=|link=none|align=left|width=100|height=75]

 

 

[img_assist|nid=1050932|title=ribbon position during trim and cutbacks|desc=|link=none|align=left|width=100|height=75]

 

 

 

[img_assist|nid=1050933|title=ribbon position during tight bottom turn|desc=|link=none|align=left|width=100|height=75]

 

[img_assist|nid=1050931|title=a few inches aft of centre, starboard rail on right point break|desc=|link=none|align=left|width=100|height=75]

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What do you conclude from this?  How do you think water was released (not released ) off the bottom?

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Greg, whenever I looked the ribbon was pulled straight - its natural state is curly. Because I could always see it this illustrates what many of us believe - water comes from under the board outwards. It also exits diagonally as the diagonal ribbon position showed. There was a good discussion by Blakestah, Bill Barnfield et al which discussed what they called the “plough effect” of a board at positive pitch displacing water and sending it out past the rails and they based much of their discussion on that.

The other notable thing was that during a tight bottom turn the ribbon diagonally wrapped the rail - it was taped on the hull and wrapped over the deck. This illustrates what many of us believe - that water wraps rails - there are some who don’t believe this.

Another observation was that a lower radius bottom turn had the ribbon wrapping less and angling more behind.

So as a result of this I continue to be a believer in wrap theory. The amount of wrap is a very dynamic thing dependent on what the surfer is doing on the board, so sometimes there is a lot of wrap and sometimes not much, but there is some wrap. The article you posted of a boat transom indicates that the wrap can even be responsible for the bulge of water.

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Wonder what the ribbon would show on a real hard rail like at the tail? Probably little to no wrap at all…no?

Depending on amount of full rail immersion, if the tail is buried, it will wrap.

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Tblank, from what I’ve seen so far, yes I think what you described would occur. One of difficulites with this test is that with the ribbon just a few inches aft of centre I had to look down and behind me, which is distracting and spoils the HP surfing experience. So after a few waves I just forgot about looking at the ribbon except at the end section of a wave. The ribbon doesn’t seem to affect performance. The board was my super Diverse ex-team board 5’ 11" HPSB.

What we need is a camera such as the Go-Pro monitoring it, but I don’t have one.

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I’m not a camera guy either, but sure would be nice to see a deck mounted video. Regardless of all the theories,it would make an interesting and fun video to watch. The head mounted cams…“point of view” are always neat to watch.

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Thx, MrJ.  I think I agree with what you think you think, ie water wraps.  Or will not wrap, if the tuck is hard edged.  My Griffin seems to bear this out, but as we have all said: lots of room for inturpretation.

Good experiment, too.  I think you could get similar data by sticking your head out of a sunroof with a smaller board.  You could study it.  Get a girl to drive, since they know how to put on makeup while driving with their knees and looking at the mirror. She could take pics.

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Reverse shot from nose of the board.

 

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Check out 0:42!  Just as Kalani unweights from his bottom turn out on the face, there is that same little hump on the inside rail as Ryan’s pictures. 

If you are centered on the board, especially on a steep face, or in a trim on a steep face, there is no wrap.  As soon as you get on the slopey part of the wave or weight a rail, there appears to be water going over the rail apex and onto the deck.  It’s still all about the water going from the inside rail to the outside rail and those old planing diagrams showing root spray and wake.  Remember that when you are looking at this, the root spray is on the bottom and outside rail and the wake is on the inside rail.  The wrap occurs when the planing becomes inefficient and the wake catches up with the planing “platform”.  It happens when the board slows or when weight is placed on the rail.  Imagine a ski boat planing along at 25 knots.  As soon as you slow down the wake catches up with the transom.  Or if you place a whole bunch of weight on the poop deck, the back sinks and the boat slows, the wake gets big and catches up with the transom.  The timing of the wrap/no wrap is affected by the rail shape to a degree.

Oh well, its clear as a bell to me.  The observations support the theory (for me anyhow).

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I think that you did a great experiment with the ribbon, I hadnt seen that before.

  The ribbon might wrap but its only an indication of whats occurring against the rail and not about water flow more than 1/4 from the rail.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/waterwrap.jpg[/IMG]