enclosed concaves???????

I have a fish outside that i made last year sometime that didn’t come out so great, is a bit chunky in the tail etc, but was the first one i tried to shape so i wasn’t too cut up about it. I never surf it though so i have been thinking about what i’ll do with it. This led me into another surfboard thought tangent in work today and i was wondering has anyone ever considered/experimented in putting in concaves that are enclosed or more realistically partially enclosed i.e they create a slight overhang along the side of the concave. i appreciate that such concaves would need to be much deeper than the norm but how would this effect the boards ride? This seems to make sense to me as it would trap the water better and you could force it through a douple concave out the back producing better drive, this is a general statement though, adding the dynamics of a wave into the equation would create some uncertaintiy as to how it would preform. i suppose you could have extremely more rounded rails at the back of the board as the rail line wouldn’t be holding the board in the wave anymore.

Anyway before i go and strip the glass off the board outside i thought i’d sow this seed in yer wise ol heads and see what happens.

so any thoughts…

Pete

I’ve played with this for a while. Rather than “enclosing” the concave, I was

looking at it as “ducts” in the bottom to give some of the hold of a fin w/o

all the drag of a fin. In Florida we’re always looking for ways to go faster, and

getting rid of fin area is a good way to accomplish that.

Nobody in the industry wants to try to build anything like this, however. It’s

just too much of a production nightmare. Enter Swaylock’s, and it’s a different story…

Mike

An enclosed concave sounds like a tunnel to me, is that what you mean ?

i wasn’t thinking quite as extreme as complete tunnels. imagine your concaves as channels, which they are essentially. you have one major channel (single concave) that breaks into two channels out the back (double concave). now try and make them deep enough so that you can start to undercut the outer edges of the “channels”. the resulting overhang (which i suppose would be the inverse shape of a rail) is what i’m talking about when i talk of them being enclosed. This would require much thicker rails but in terms of surfboard thickness it could be much the same.

another thought if you could complete such a design, what would be the effect of putting tunnels coming out the side of these “overhangs” towards the back giving different releases for the water and how these would act when the board is turning i.e on different rails?

but lets walk before we can run!

I’m curious.

Do you have a crude sketch or diagram?

kc

This bit was added in the edit…

I don’t expect that you have followed my nonsense in the past, nevertheless I’m incline to see the flow from the wave as the source of propulsion in surfing. (The flow impacting the bottom surface at an high angle – upwards and forward.) Given that to be the case, than I’m led to believe that a surfboard gets ‘one shot’ at the flow, and after the transfer of momentum the flow is what you might call ‘spent’ flow, so getting rid of it, or removing it as fast as possible seems interesting.

A flat surface will cause a lot of interaction with the new fresh flow, the spent flow being pushed out of the way – energy which might be better used, if only marginally so. The lip you propose might provide a avenue for some of the spent flow to move off without interacting too much with the fresh flow. The bottom surface of the lip, offering a area for flow interaction –i.e. a contribution to propulsion. Then again, the whole setup might wind up being just a ‘catcher’s mitt’ for momentum and wind up ‘dragging’ the board to a halt.

The next step would be to bring the lip right across the rear of the concave – that would be interesting too.

I don’t see the exhausted flow as a direct source of propulsion itself, but one more of ‘waste’ management.

Admittedly, its all likely to amount to just a tweak, but it is an interesting notion. Even if we disagree on what it might do, or how it might do it.

kc

If I could post photos (first I’d have to take the photos, then figure out

how to post them) I could show some of my stuff along these lines. Maybe

I can take a camera to work tommorow… Wes Laine has one in his office

in Virginia Beach but he’s down here now. Blake Jones has one in his garage

but he’s in California.

David Balczerack has been shaping related/similar designs since the 70’s.

He’s tried almost every imaginable bottom/rail/wing combo. Go to Puerto

Rico and check out his arsenal.

Mike

i’m merely hazarding guess, which is why i thought i’d put it out there as i don’t know what would happen. it is just interesting to see what people think. to be honest i have no idea what will happen (just thinking out load here). i’ve only been shaping boards as a hobbie for about a year and a half in which i’ve only shaped 13 boards so i don’t really have any great knowledge bar my basic understanding and what makes sense to me.

The only way to really find out what will happen is just to do it!

this is an extremely rough idea of what i was thinking

is obviously upside down but you get the idea

attached is something i played with a few years ago

along the lines of your edited bit (kcasey) was interesting to surf, was a pain to paddle as so much drag. once up did seem to pick up speed compared to the board tested alongside it with no modification, but then turning was affected also.

That’s what I thought you had in mind.

Though I was curious to see if you planned to taper the region in a way that would have resulted in the kind of funnelling of flow, as would be the case with Pauluk’s construction, see Pauluk’s picture - which would be a drag under just about any circumstances, aside from installing a water-jet engine. I was hoping that you were considering taking in the opposite direction, expansion or outwards, as opposed to inwards or towards confinement of flow.

And, yeah, in the end - trying it, is the only way.

kc

That’s curious. I do envy your commitment to an idea. I’ve ‘wasted’ a few boards myself (that’s not to imply anything you’ve done is a waste) and hopefully I’ll waste a few more.

See my post to Outhouse.

Thanks, that is one curious board.

kc

After seeing your sketch, I will try to get some photos up tomorrow.

What I actually built was quite similar. Me trying to get photos up should be

quite entertaining. Pleae excuse the delay.

Mike

i was just planning on letting the rail line do the funneling. the natural curve fo the board. just keep the concave a certain distance from the rail the whole way down.

Hey mike can’t seem to find anything on David Balczerack. anywhere on the net where i might get a look at some pics?

``````        Cheers

Pete
``````

those look like a much more extreme version of what is on my original MR twin fin, I think they might be called fluted rails, supposedly one of the fishes in Sprout that dave rastovish rides has really fluted rails. I liked them on the twin they gave a good bite when laying into the turns

*not that the wings on the template were fluted not the whole rail line.

DCB is seriously underground, so it doesn’t surprise me you can’t find him on the net.

That’s a shame, 'cause the guy was one of the best surfers in Florida in the mid-late

'70’s and rode everything from 5’6" Up-wing/Down-sting(one of his versions of what we’re

discussing here) to 10’ noseriders, when 10’ noseriders were very unfashionable.

He’s been in PR for a long time. When I brought one of my (supposedly original) "tunnel

rail" designs to Surf Expo a few years ago, about ten of the people who looked at it

said, “that looks like a DCB”. I kinda went “Oh yeah…”, and remembered some of those

crazy things of his that I saw 25 years before. It really hadn’t occured to me and I

thought I had come up with my version independently. I hadn’t seen any of his boards

in a long time. But I guess they were still floatin’ around in what’s left of my brain.

I’m still going to try to get some photos of one of mine up later today, but it’s going to

be after work,etc.

Mike

would be great to get a look at those pics if you get them up, cheers mike. Does anyone know if mike eaton is a swaylockian? looking at his zingers/bonzers. similar to what i was thinking. would be great to get his input.

http://www.eatonsurf.com/Bonzer.htm

``````Pete
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oh man, the memories, I had a ton of DCB during my youth back in PR…that was the first time I saw a battail. the man was inventive and quite creative at the same time. He had one design I dont know what to call it but it was like a battail with the center point extending out another 3 to 4 inches…is there such a thing as pterodactyl tail? His wings were more like the teeth on a circular saw…it was total style back on those days.

There we go!!! Thanks for posting that up, Alberto.

I bet there’s more DCB images out there, these are definitely the kind

of boards you’d take pictures of and remember… DCB may not want the

attention, but he sure as hell deserves the credit!

Mike

enclosed concaves?