Internal Fins / Finless Control System.

General Discussion
101

Just a thought, and also trying to get my head around (or into) it all…

 

I understand that the fin-like grip comes from redirecting the water flow much like a fin does, but have there been some elements of the ports incorporated to allow the fastest exhaustion of that redirected water possible? I wonder if exhausting the water as fast as possible could allow the ports to have more drive (and less drag) than a fin? With a fin the water hits it and gets deflected by the whole fin, and when trimming there is tip and form drag of course, but maybe the ports would have far less than these drags if there is the smallest manipuation of the water flow possible? The least energy lost in the exchage…

 

Maybe something extremely diagonal in nature to make the nose-to-tail water flow redirected as little as possible, but the lateral water flow more significant due to the lateral hold needed…

 

Or it has already been thought of and incorporated…haha you tell me! Just swimming in my own head a little and looking for things to grab onto that look useful…

102

[quote="$1"]

EDIT.... but have there been some elements of the ports incorporated to allow the fastest exhaustion of that redirected water possible? I wonder if exhausting the water as fast as possible could allow the ports to have more drive (and less drag) than a fin?....the ports would have far less than these drags if there is the smallest manipuation of the water flow possible? The least energy lost in the exchange...

 

Maybe something extremely diagonal in nature to make the nose-to-tail water flow redirected as little as possible, but the lateral water flow more significant due to the lateral hold needed...

 

Or it has already been thought of and incorporated...

[/quote]

Thats exactly what Ive found after lots of attempts. I dont know what the other guys are trying  but by keeping the hull and deck ports out of alignment it makes the rear internal wall angle low /diagonal and allows the  water to flow thru easily. Maybe try a curved rear wall(red) to reduce the angle further...( see end pic)

 

 But the diagonal exhaust will make it to a commercial product because it works better.

  I started out trying to make the water do what I wanted it to do, but now its clear that its best to just let it go thru smoothly. You need the flow to make it work so trying to reduce the flow isnt helping.

You know as much as I do now.More or less.

I got a call about a guy showing up at a Flo-Rider with a vented board....?

 Funny how so many people are doing something similar...

103

A couple more testers in Innegra. The rear angle is 35*.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/Z030.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/Z031.jpg[/IMG]

Sanding Innegra doesnt make you itchy.Thats a plus.

 

 

 

104

tblank, yeah theres progress. The vents are where they should be, out on the rails like a quad, theres more grip out there than in a central position, however a Thrailkill Double Single might work as well....

  Getting grip isnt a problem, for me its about getting the flow in and out smoothly, with the bigger vents its was chaos with water spraying everywhere. Make the flow smooth and its more responsive to control. Just like a fin, if the water flowing under a board was confused froth you wouldnt get much control.

 Horsemouth just posted this pic from a Brazilizn guy called Homero Naldinho, and his Internal Fins...

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

How similar does that look to the earlier ones I was doing ??

 A couple of things Ive noticed from the pic, if the finbox is 1" wide then his 4 vents are 2" wide X 5 " long.

 Thats pretty huge in my book, he'd be getting buckets of water flow coming thru and with the larger vents they take away from the planing area of the hull.

If youve got 4 vents, 2"X 5" youre losing about 32 sq in of planing area. My guess is that the board would ride differently because of that.

 Its amazing how many people are doing the same thing...

 

105

Just back from a test surf with 2 types of vents.

 This one is an oval, 20 mm wide X 100 mm long.

Im trying to make it 'ZERO drag' in a straight line so it doesnt have any negative impact on speed,and this design is almost perfect.

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

 And even at slow speeds ( ~1m/sec) the water just sheers off the almost square (85) trailing edge at the front and shoots up the rear ramp in a smooth flow. Its not like the older vents where the water was a flurry of foam and slop shooting eveywhere, this is a smooth, controlled flow. Like the boundary layer is extending in a smooth sheet. Sorry theres no action pix.

 Id gve it a 9/10 for zero drag but the only area for improvement would be the 35 deg edge at the rear.. it seems to make just a little touch of drag compared to a flat test board. Maybe take the angle down to 20 degrees... But Im worried that a lower angle will start to sheer water up off the boundary layer but I think its

 The other vent was this one with an extended shelf inside to direct some of the flow back under the board. The overall design is old but I was testing the effect of a low angle shelf and how it would/could reduce drag at the rear of the vent.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/CS003.jpg[/IMG]

  Massively wide at 60mm, the shelf seems to reduce any grab at the back angle of the vent, this one has an angle of  25 deg, but it could also do with a test at about 10 degrees. Even tho its a lot wider than the first vent and it lets in a bucketload of water , it doesnt have drag thats hugely greater than the slim one....?

 So in summary and so far........

 What works is...

a front angle of almost 90 deg ,

 keeping the vent slim and long,

 and low angles at the rear work.

 Its not a problem getting sufficient flow into the vent.

 I think Ive got the basics worked out, or at least a better understanding of what wont work. I also keep an eye on ease of manufacture, installation and aesthetics.

 Now to get down to the real specifics of reducing drag and then on to getting that lateral grip.

 Any comments or guidance is most welcome guys.

106

Great progress Surffoils, Sounds like you are getting it dialed in. How much “grab” do the side vents have in turns? Also how does the center vent engage in turns? Sounds like you have forward progress worked out there. Just wondering, is the center vent vital to have?

107

How is the “FEEL” compared to finned boards?

108

I think the feel is similar to what you get on a snowboard or skis where theres more riding of the rails.

Heres some pix of what Ive whipped up this evening...L 130 X W 20 X H 40 mm

 Photobuckets screwed so theyre attached.

 This is the plug. Ive kept the swept back exhaust but added a forward facing Low Incisal edge at 10 degrees hoping it will take away the last bit of drag in a straight line.

 Ive made the sides at the back parrallel rather than pulled in like I had with the oval to reduce squeezing the flow in the rear of the vent. 

 Its all worth a try !





109

I suppose Ive got to go in all directions to see what works best but this one has too many angles and returns to come off the mold easily.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/Y002-1.jpg[/IMG]

 

 

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/X011.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/X010.jpg[/IMG]

 

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/X012.jpg[/IMG]

 

 

I had to cut the front of the layup and pull the mold out of the front. 

 Ive installed it in a board this evening and test it on Mon.

 I think I'll go back to simpler versions.

110

 

The crux of the problem right there.  “Like a fin does.”  There’s a LOT of lift happening with a regular fin, a lot of lift … AKA “drive” … in trim or a turn or pumping.  Which an internal system won’t be able to replicate – you can do HOLD, but not DRIVE.  For drive, you need lift/control planes that extend out of the hull into the main stream.  My theory is those can be much lower profile longer based fins perhaps working in tandem with much smaller vents than Brett is working on right now.  But it couldnt hurt to look hard at wakeboards for hull/rail contours as well as the smaller fins. 

 

 

 

111

This is the one with the trailing wall angled forward.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/Y027.jpg[/IMG]

Semi-installed,

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/V003.jpg[/IMG]

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/V002.jpg[/IMG]

After testing there doesnt feel to be any diff between the drag from this one or the previous one with the rear wall thats sloping back.

 I think it might have something to do with some of the boundary layer peeling off ,with little effect, while the bulk of the water shoots under the vent and on its way.

 With this new one theres very little water that comes up when in trim as opposed to this earlier one..

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/PB150222.jpg[/IMG]

where water constantly shoots up thru the deck vent all the time.

 Were going forward with a few overall changes.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/W007.jpg[/IMG]

 Because the water only comes out the back of the deck port weve made the deck port smaller and moved it to the rear.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/V005-1.jpg[/IMG]

We found that having an Active and a Passive side wasnt making a great difference so we made the whole port shape symmetrical (Left and Right ) and its all been good.

 Because boards are different thicknesses at the tail weve concentrated all the design under a 2 cm line and just extended a column up for thicker boards.

[IMG]http://i153.photobucket.com/albums/s225/SURFFOILS/SURFFOILS%202010/V008.jpg[/IMG]

 Still a lot to do.

112

I just had a thought…what about a quad fin board that has two fins in the front position for general “control”, and two back interal fins for hold depending on the dynamics… ? :slight_smile:

113

This is a good and worthy project. Thanks for all the updates. Hope there is a video in the future.

114

Thanks for the comments guys, I think Janklows right about the Grip VS Drive.

Theres still lots of things that could happen, maybe put these vents side by side in sets of 2 (see pic), or like Cpt Caveman said with a hybrid version mixing current fins with the Internals.

Or probably just design a board to give more drive. Something specially shaped for more drive..

 

115

Great thread!

I’ve been thinking about this type of thing for a while and stumbled onto this thread and it’s a great read and resource.

I have a few thoughts about this to share that may be food for further thought.

First a loaded question, do boards really turn off the fins or do fins just aid to bury the rail and then just add a bit of lateral stabilty?

Anyway, I have just built a wide tailed single finned board (based on an astron zot) that doesn’t wont to bury the rail in bottom turns, my thoughts were if I could get the rail in it would turn and this led me to thinking of reducing the pressure (surface area) to the underside of the board by putting ‘holes’ in the board near the rails to let enough water through to let the rail bury. (I’m also guessing that this is why a lot of the early single fins had skinny tails, to help get the board over onto the rail)

The work you have done surffoils is awesome and has now got me motivated to give this a go, thank you for sharing your results and theories. I’m not after a totally finless board, I’m happy with a single fin but if the internal fin design has comparable or less drag than a toed in fin with nearly as much hold I think this could be a great alternative.

I note this thread hasn’t been active for a while, have you or anyone else done any more work on this design? I’d be interested in your progress/thoughts.

Cheers,

Mick.

 

116

the induction has to be tapered.

w/o the taper it won't work.

the taper creates a vaccum = control.

that's part of it...........anywho.

keep thinking..........you'll get there............and beyond .

 

herb

117

Thanks Herb, the pic’s fo your board look great too!

The best thing about building your own board is it really makes you think about what’s going on as opposed to taking what you have (a design by others for instance) for granted.

While not directly related this is what had me thinking about this topic, I started with quite a large fin in the middle of the box and my first bottom turns were stepping out, especially if I pumped it like a thruster (I’ve since learned this is not the correct style for a single fin :slight_smile: ). Next surf I moved it right to the back, this made it worse! Next surf I put it right forward which made it better but still not ‘rideable’ enough for anyone to have a go.

Coming from an engineering background (I work in a structural/mechanical engineering office as a designer) it got me thinking about leverage and the mechanics of the fin against the water so I figured that the leverage created by the larger fin was stopping me turn onto the rail so I put in a smaller fin and bingo, it gets on rail a lot easier and turns. Still needs some work but the results were pleasing.

So, from this my thinking about fins are not so much for turning but are more useful as a lateral stabiliser to pivot on, perhaps I need a smaller fin with a much longer base or more rake??

My point from all this is that holes/vents strategically placed will/should aid in getting the board on rail to turn, if they provide some sideways stabilty all the better to lever off as well. I’m not sure about compressing or de-compressing (for want of a better term) the water through the vents is as important as just getting the water through the board as smoothly as possible(??).

I have a few design ideas which I’ll model/draw up later when I get a chance and post them up for discussion.

Cheers,

Mick.

118

[quote="$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 ?

 

[/quote]

my ports primarily draw water up,not air down.the board is ported in the nose and tail for board spin control or for flipping the board into a 180 and having the same set-up to ride. in other words the board has no nose or tail..........just ends.

herb

119

i'm thinking about finning/boxing my original proto.

i have always wondered how fins would make it ride????

i have a new finless induction version in the oven.

a design a bit easier to build.

herb

120

Great work so far, any updates surffoils?