Author Topic: Fence fin with Larry Allison multi fin setup.  (Read 9421 times)

Luc Benac

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #15 on: May 27, 2017, 06:08:04 PM »
  So is this basically running a ventral in the back in place of a normal center fin, or is a "fence" supposed to be something different?

I think that the difference is that a ventral is foiled and has some thickness versus the PonoFence that is very thin and flat.
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ukgm

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #16 on: May 28, 2017, 01:25:06 AM »
So that didn't work--AT ALL. All the fussing I did to make the first versions really straight and true are probably important.

I paddled at a pace that I'd expect to hold in a long race and got 5.3 to 5.5mph with just two fins. then I stuck in the fence and got 4.9-5.1. Not what I was looking for. Put in a ventral fin and got 5.3 to 5.5 -- inconclusive. Moved the fence around in the slot, but never got better than 5.1 and that was cheating. Put the stock fin in the middle and got 4.9 to 5.0, then sprinted it and got 6.0 but only briefly. I think my arms were tired from this morning's OC-6 practice. I went hard for the entire run. Long story why, but I really pushed and worked on my Puakea stroke.

The version of the fence before this one gave me 5.7 to 5.9 in similar conditions. I went backwards, but I learned a bit. Nice to know the twin fins by themselves work well in really placid water. Less stable, but fast. I could feel how well the tail released.

I'm still baffled by this whole thing.

To bring me upto speed, what is the basic concept intended to do here - to increase flatwater speed or something else ?

PonoBill

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #17 on: May 28, 2017, 06:09:05 PM »
Increase flatwater speed--but don't ask me how. When I first got my Blackfish I experimented with its three-fin setup. Nothing I'd heard about it made sense, but Dave Boehne is a smart guy and Larry knows fins in and out, and they claimed it worked. I tried it and found it to be slightly faster with the center fin in than just the two side fins. Conditions weren't ideal for testing, but the difference was consistent. Then I tried a small ventral fin in place of the stock, fairly large center fin and found it MUCH faster.

I couldn't come up with any good reason why a somewhat draggy center fin would be faster than just the two side fins, since I felt no indication of yaw under any configuration. I thought it might not be acting as a fin, but rather as a fence, preventing destructive interference between the fins. Fence one worked better than the ventral fin, but was secured weakly and is now on the bottom of Canyon Lake. Fence two was substantially slower than fence one for some obvious flaws (not straight). Fence four worked well but I gave it away to another blackfish owner. Fence five looked like it should have been the best so far, but it was very slow.

Mystery continues. Recent conditions are very flat, but there may be current issues, even in the dead-ended Nichols Basin. If current is the difference, then it affects the fenced fin set much worse than just two fins.
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Rideordie

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #18 on: May 28, 2017, 09:52:14 PM »
This fence fin experiment is really fascinating to me. It is all rather counterintuitive. I applaud Bill and Luc for their experiments that are yielding some unexpected results. I sense that there is some kind of breakthrough learning in process. I also applaud Larry for his revolutionary set up and Dave for putting it into production.  I was very skeptical about this fin set up initially, but I have come around completely in my thinking now. Please keep the experiments and posts going!!
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Larry Allison

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #19 on: May 29, 2017, 11:15:59 PM »
This fence fin experiment is really fascinating to me. It is all rather counterintuitive. I applaud Bill and Luc for their experiments that are yielding some unexpected results. I sense that there is some kind of breakthrough learning in process. I also applaud Larry for his revolutionary set up and Dave for putting it into production.  I was very skeptical about this fin set up initially, but I have come around completely in my thinking now. Please keep the experiments and posts going!!

Thanks Ponobill and Luc for pushing the boundaries. Thanks Rideordie for your Confidence and doing your homework and getting rid of the koolaid others feed the market. Mahalo, Larry
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PonoBill

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #20 on: May 30, 2017, 06:50:05 AM »
One thing for sure--it's going to be very hard to draft any multi-fin board. The wake is a wide burble with no definable energy pattern. Could be that they can be drafted to the side, but not directly behind. That might be a big enough benefit for racers to adopt them.
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XLR8

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #21 on: May 30, 2017, 07:05:56 AM »
Are you also using the ventral fin up front under the standing area in these set ups?  Or just the three fins in the rear?  Must one always use the ventral fin in combination with the three fin set up, or, could a person just run the three in back with no ventral?

I guess I am confused of the role the forward ventral fin plays in this arrangement.

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PonoBill

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #22 on: May 30, 2017, 07:20:06 AM »
I rarely use the ventral fin, it adds drag, and I find the benefit (straight tracking) to be easily achievable with better stroke technique and rail control. With my geezer strength levels, I can't afford drag. Guys like Rob Rohas will never notice it, but I do. It also makes for challenging buoy turns, you have to unerringly get the nose out of the water enough to clear the fin located relatively close to the middle of the board. Geezer balance precludes that.

My experiments are all aimed at keeping me in the hunt at mid pack.
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burchas

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #23 on: May 30, 2017, 08:15:02 AM »
I rarely use the ventral fin, it adds drag, and I find the benefit (straight tracking) to be easily achievable with better stroke technique and rail control.

I'm wondering how much testing did you put into the ventral? This fin never leaves my board.
From my testing with it VS a single fin I found that average speed was higher with the ventral.

I noticed that top speed was consistently higher with only the center fin with an 0.2MPh average
difference in top speed but overall average speed with ventral was up by an average of 0.3mph.
Looking at the graph showed that the board with the ventral keeps its forward momentum
better and does not decelerate as much between strokes.
in progress...

PonoBill

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #24 on: May 30, 2017, 08:59:58 AM »
I'll try it again, but I suspect you're working with a different engine room.
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XLR8

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #25 on: May 30, 2017, 09:34:12 AM »
I rarely use the ventral fin, it adds drag, and I find the benefit (straight tracking) to be easily achievable with better stroke technique and rail control. With my geezer strength levels, I can't afford drag. Guys like Rob Rohas will never notice it, but I do. It also makes for challenging buoy turns, you have to unerringly get the nose out of the water enough to clear the fin located relatively close to the middle of the board. Geezer balance precludes that.

My experiments are all aimed at keeping me in the hunt at mid pack.

Thank you.  Those are my impressions with the ventral as well.  But I've had guys tell me the three fins in the back are pointless without the ventral.  But I have the exact same impression as your response.  Thanks!
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ukgm

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #26 on: August 19, 2017, 11:39:17 AM »
I'll try it again, but I suspect you're working with a different engine room.

What's the latest on the fence experiments guys ?

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #27 on: August 19, 2017, 03:06:51 PM »
  I use the ventral almost all the time. It's very noticeable in acceleration and does a very good job of quieting the nose of the board in rough water. It'll track going downwind but if you're going up/down like I always have to it's worth it. The two weak points of the ventral are draft trains, it tracks heavily and the board will dart to and fro, and relatively flat water with a sidewind. Turning the nose of the board into the wind is hard enough, having to also fight a fin makes it worse and you will not be able to same side steer it. From now on I'll not run it in those two scenarios but otherwise it will stay on. This is on a whiplash, more all water type shapes may be different.

Luc Benac

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #28 on: August 19, 2017, 05:28:53 PM »
I'll try it again, but I suspect you're working with a different engine room.

What's the latest on the fence experiments guys ?

It is downwind season here. Flat water and tests have been set aside until the wind goes away along with the sunny days....
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PonoBill

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Re: Fence fin with Larry Allison multi fin setup.
« Reply #29 on: August 19, 2017, 09:28:53 PM »
Pretty much as Luc says. I've been on my SIC Bullet 17 two runs a day, every day it blows. Between that and OC6 practice I don't have much left for flatwater fiddling.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

 


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