Internal Fins / Finless Control System.

General Discussion
1

With respect to Herbs work.

  My eldest son and I have been making vents thru boards to create lateral control, theyre not designed to draw air down but to redirect water up from under the board.

Similar to Herbs work but mine are longer and asymmetrical and provide control specifically to replicate the feel of a standard finned board.

In a week or so I will have pics of them in boards but for now I have a few pics of the construction and prototypes.

 I didnt shape a board and then shape a hole in it. I shaped the 'void' or vent and used it as a molding plug to laminate the walls of the vent.

This is the size of the original mold showing the hull or induction opening, the straight edge goes towards the rail.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/August2010008.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/August2010010.jpg[/IMG]

Some of the shape and size variations for the hull vents.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010024.jpg[/IMG]

Finished vent plug.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010003.jpg[/IMG]

Carbon fibre layup, it looks thick, but its got a lip around the edge.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010010.jpg[/IMG]

Off the mold and you can see how the water flows from the hull thru to the deck.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010011.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010012.jpg[/IMG]

 In testing the effect of this design proved to be too strong and some of the internal wall angles werent right. But we found out that it can be smaller and still comparably effective as a standard side fin.

This is a much better and compact version. Because boards arent very thick near the tail the tube itself only needs to be about 1.5 in high.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010017.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010015.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/September2010019.jpg[/IMG]

 It has the deck and hull vent overlapping so the flow is quicker and the whole unit is smaller.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/SeptemberB2010006.jpg[/IMG]

Better version of the plug mold.....

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/SeptemberB2010005.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/SeptemberB2010004.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/SeptemberB2010007.jpg[/IMG]

 The vent/tube/port creates control in the same place that standard fins are placed.

  We're only focussing on making something that could be put into a standard glassed board instead of fins.

More pics if you want.

Anybody else following Herbs lead ?

 

2

I think the Great Stuff is a U.S. thing. I’ve used it to make a flex tail. Once glassed, it’s not too bad. 

3

facinating! can you describe how they feel to ride and turn? what sort of boards are you trying them in?

 

are you using a standard middle fin with these vents instead of side fins? or are these boards practically finless apart from the vents?

4

They feel the same to paddle but as you turn theres a positive grip in the tail,the deeper the turn the greater the grip because the grip comes from the water crossing the edge of the vent..the greater the speed and angle of the flow, the greater the grip.

The boards done feel stiff because you only get grip when you turn, not before.

 We've put them first in an xps test board,

and then in a board with a vent on one side and a standard fin on the other side to test the difference or sameness at the same time.

and then retrofitted them into a 6'2" and a 9'1".

The 9'1" LB has side vents and a thruster-style middle fin and the shortboard only has 2 vents, no fins at all, so its like a twin fin.  These few boards have had a beating with installing vents and ripping them out but I can post pics of them when I get home tomorrow.

 Ideally.... boards with this style of control system would have no fins at all,

 no plugs,

 no sharp edges,

 nothing to snap off when travelling,

 just a lightweight blank purely shaped for the wave and the vents would be made from a flexible silicone/rubber so they would flex with the board.

5

I would be very keen to see the pics of the 6’2" twin vent :slight_smile:

What do you think is the effect on drive compared to traditional fins? I understand that fins cause quite a bit of drag, however I’m also assuming that these vents work by using drag to make the tail “stick”. How much is the waterflow impeded during the travel through the vents?

Great idea by the way!

6

In the "Induction (vented / ported / slotted)"  thread thats current at the moment, on page 3 Blakestah has the best description of how it works. I could explain more myself but I wouldnt make it any clearer.

 The flow of water thru the vents is smooth and frothy, its not a jet-effect, the length of the tube is less than 2 inches and the area of the holes are large enough to take a lot of flow. One of the first things we noticed is that the shape of the port /hole on the bottom was more important than the area of the hole, so the holes are changing with each version.

XPS test board.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010005a.jpg[/IMG]

Fitting 1st cf tube for test run.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010009a.jpg[/IMG]

 A longer thinner 'slot' style of port on the underside works best, that we can find so far.

 Potentially a quad set of 'slots' no bigger in size than Futures boxes could work just as well as quad fins.

 I cant claim it as my idea, Morey and Herb did it long before me.

7

Very interesting Surfoils, looking forward to future ride reports and developments. Thanks.

8

Thanks tblank, I hope I can interest a few people with some pics.

When the tube is installed its flush with the hull, so theres zero added drag.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010A005a.jpg[/IMG]

But as the water would contact the hull as it rises up the wave at an angle, the vent 'opens' up.

(water flow in this picture is from the bottom up)

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010A006a.jpg[/IMG]

Two of the 3 sides have overhanging walls (black) so that they dont draw water up.(red lines) But the  'active' edge / side is sharp and water is sheered off the surface and up the tube when the flow is from the correct side.( blue lines). Overall it means either vent doesnt create any drag unless the water is from the correct side so only the inside / waveside vent has control. Turn left, and the left side has control and the other side has no drag.

 

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010A007a.jpg[/IMG][IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010A007aa.jpg[/IMG]

This pic below just shows the different angles  where the passive sides in blue have an obtuse angle ( purple spot) but the active side has an acute angle at the edge where it joins the hull.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010A00123a.jpg[/IMG]

 The first tubes were installed with the long axis parrallel to the stringer but we've found they work better with a bit of toe-in like a standard fin.

9

Have you the ability to shoot video while in action? I follow the theory and so far it makes sense. Of course this means you would have a right and left handed board.

10

I’ve been waiting for this stuff to expand beyond the teaser thread that went underground after BT took HS on in a license agreement or whatever.  

 

The one thing that gives me pause is the utility of outside fin and rearward fins’ tip drag.  But whatever – I’m super-interested in the topic and development – I hope it ends up being as awesome as this but more so

 

11

I was thinking about trying out the same thing, except I was going to try pvc pipe at an angle through the board and it would be a whole lot more rudimentary. This is great. I want to see more. Post more pics. Have you experimented with jutting the sharper edges out of the bottom of the board; in order to increase drag?

12

I’m thinking of vents roughly the size and shape of a Lokbox fin box

–> filled with waterproof silicone or some such easily workable substance – easy to take out and re-fill

–> gives you ability to knock out an existing setup to customize / change out vent tubes, slots, reset the number and angle etc and re-fill the silicone …

 

 

 

((((*** ow shit the word “venturi” just came to mind… i’m seeing stars *** Perish the thought of this word appearing on Sways again (with claims of ever-increasing rocket speed power etc ad naus))))

13

Tblank, I have got a waterproof camera that does about 15 secs of video and I'll try to get some clear shots for you.

Monkstar1, "Have you experimented with jutting the sharper edge out of the board..."

 SPOILER ALERT! How'd you guess that !??

Thats exactly what we did once but we were trying to keep it totally 'finless', my son didnt want anything except for a smooth hull to keep it "pure", but I believe that as we go further with refinement, that the little crescent runner we used will eventually be best. I found that the little fin pulled a lot more water into the vent and then we had to redesign a smaller vent overall but we havent followed that variation all the way, yet...

Honestly,how the hell did you guess that variation ?

 

Janklow, yes an easier manufacturing process would be better like you suggested, and because the unit is a part of the inside of the board it doesnt need to be strong or heavy in any way, just waterproof.

Most of the vents are LHS so that we can put them on a board with a standard RHS fin on the other side to compare how the board turns left and right. I can say that the vents give enough grip that you dont have to squat when you turn like in some of the finless vids.  its almost the same as having fins, and thats where we want to get it before we show it fully.

14

[quote="$1"]

but we were trying to keep it totally 'finless', my son didnt want anything except for a smooth hull to keep it "pure", but I believe that as we go further with refinement, that the little crescent runner we used will eventually be best. I found that the little fin pulled a lot more water into the vent and then we had to redesign a smaller vent overall but we havent followed that variation all the way, yet...

[/quote]

surffoils, interesting stuff as usual from you...

have you looked at the Peregrine Falcon's nostril? i've heard that they used that design when making some jet engines to help pull more air into the intake... a quick google search pulled up some stuff. i'm sure there's more info about it out there...

http://www.asknature.org/strategy/11c8b6909e80305d1418f1ff64c9fdb5

http://biodiversitylibrary.blogspot.com/2010/09/book-of-week-peregrine-and-modern.html

http://photo.net/photodb/photo?photo_id=6215272

it might be an option for pulling more water into the opening without having anything protruding below the hull of the board.

15

Fascinating that once again science could be shown the answer in what nature has already created to work.

16

I understand that you’re using the vents to create hold and control from redirecting water flow. How might you also combine that with elements to produce lift, planing and reducing the wetted area? Is that where other bottom contours come in to play? (e.g. concaves, etc.). To me it sounds like this board may need to “sit” in the water a little to show its full potential?

17

radical - this stuff is WAY over my head!  Love the pics, 'tho, keep 'em coming!

18

Heres a few pics of the deck port, its of a later smaller version, so the deck has a hole for the larger vent we started with.

 Its on a prone board holding the camera in front looking back, so the water is coming up from the bottom of the pic, from left to right.

Its a left vent on a left wave.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010B011B.jpg[/IMG]

 It doesnt show it but the boards going at about 3 metres a sec in a straight line along a walled up wave.

 [IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010B008B.jpg[/IMG]

Theres a solid amount of water constantly coming thru but it has a frothy look about it. This vent was way too big because the effect was really strong.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010B005B.jpg[/IMG]

 The next gen are a lot smaller and the wall angles are a lot different.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/June2010B013B.jpg[/IMG]

Eventually theyd probably look something like this in a shop.... :)

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/InfernalPrototype.jpg[/IMG]

19

I’ve been thinking this up in my head for a while now, that’s why I was thinking about protruding edges. Also, have you experimented with the angle of the flow through the board? If I was starting I would place it at 45 degrees (just as a base model) and then tweak from there. I’m also very curious as to how you came up with the opening shape. One more thing (my head is exploding), have you tweaked the general size of the opening and exit port at all? If yes to any of these questions, could you post your results?

 

I’d like to thank you for posting what you have so far. You are an example of what Sways is about. As a long time lurker here I appreciate the posts you guys put up.

20

Look into the principals of a naca duct for aerodynamics. The aspect that makes this difficult is that there is the boundary between air and water (air on top, water on bottom). If I understand what you are working towards, it’s splitting a layer of water off and up through the board, correct? A naca duct splits and draws in air by creating a low pressure area in the front of the duct which then draws the air in. It’s the dip and the widening of the duct that creates the low pressure area. Since air always wants to flow from high to low, when placed in a high pressure area, the effect is a nice flow without the need for a drag inducing splitter or redirector.