twin-fins-or-more-on-a-race-board/so it begins

[ukgm]

I understand your skepticism Kieran--I shared it, still share it, sort of. I'm skeptical of anything that works if I don't understand why it does. I don't like that.

The odd thing about the Larry multi fins is that they actually feel low drag. My fastest configuration so far is small twins with a ventral or fence between them. I'm pretty sure if I measured the area of those three fins they would be substantially bigger than one of my test single fins. and yet they are faster. I don't like them for downwind, I feel like I'm just a passenger, but upwind, crosswind or flat, they're faster. Not a little faster within the error band. I mean WTF just happened faster.

Maybe the reduction of the depth of the fins is creating less turbulent flow (even if the net surface area is the same).

[Larry Allison]

I understand your skepticism Kieran--I shared it, still share it, sort of. I'm skeptical of anything that works if I don't understand why it does. I don't like that.

The odd thing about the Larry multi fins is that they actually feel low drag. My fastest configuration so far is small twins with a ventral or fence between them. I'm pretty sure if I measured the area of those three fins they would be substantially bigger than one of my test single fins. and yet they are faster. I don't like them for downwind, I feel like I'm just a passenger, but upwind, crosswind or flat, they're faster. Not a little faster within the error band. I mean WTF just happened faster.

Maybe the reduction of the depth of the fins is creating less turbulent flow (even if the net surface area is the same).

Ukgm, Your are partly right, but Placement of Fins and Fin Foils with Cants are other factors.

[Larry Allison]

 ·

Had a Allstar 14ft by 25 " show up for Allison Probox Race Twins today. Also after my New York Paddling guest Yuval test rode this 14ft by 23" Bluefin Focus, got the email from the owner of Focus, Jacob this morning to retro fit the Bluefin for them to ride with Allison Probox Race Twins. Great to see more major Board companies trying Allison Probox Race Twins with Ventral assist. So it continues, more to come that will blow your mind Mahalo my friends for the support!

[Bean]

I understand your skepticism Kieran--I shared it, still share it, sort of. I'm skeptical of anything that works if I don't understand why it does. I don't like that.

The odd thing about the Larry multi fins is that they actually feel low drag. My fastest configuration so far is small twins with a ventral or fence between them. I'm pretty sure if I measured the area of those three fins they would be substantially bigger than one of my test single fins. and yet they are faster. I don't like them for downwind, I feel like I'm just a passenger, but upwind, crosswind or flat, they're faster. Not a little faster within the error band. I mean WTF just happened faster.

Maybe the reduction of the depth of the fins is creating less turbulent flow (even if the net surface area is the same).

Or, in part, as the board moves through the water, the water closest to the board is pulled along.  And, the shallower fins benefit from the water in motion while the deeper fins have to slice through stationary water.

[ukgm]

My board is now in to have the system installed by Supuk (with Larry advising from afar). I'm pretty excited about trying it out. All being well (and if the weather stays mild into October), I should be able to get some hard data and telemetry from field testing using my usual methods before things go cold and nasty and then I'll race it over the winter.

[ukgm]

Well, with the right conditions and weather, I can finally share the results of my testing of the Allison probox system + ventral assist in my 2017 Allstar. I used my standard (and published) testing protocol and used a market leader (and fastest fin I ever tested) as the baseline. I should add that the fins were donated but the install was paid for by me (and undertaken incidentally by SUPUK on here). The graphs shows the result. I'll have to be honest and say I was surprised as I still haven't got the set up to perform quite as I want to and it still felt draggy to me but the numbers don't lie. Larry has great intuition

[Luc Benac]

Nice results. Which LA setup did you use? i.e. which twins and kick.

[Area 10]

Could still be a placebo effect, I’m afraid.

As a minimum, you need to repeat the study using several paddlers who do not know which fin setup is being used to even get close to a firm scientific conclusion here.

With this study design you can’t counter the argument that all you are showing is that you have invested a lot of money and time and effort in the installation and so are unconsciously paddling better when that setup is in. These kinds of (genuinely) unconscious physical placebo effects can be huge. If you believe it works, it probably will.

[Larry Allison]

Could still be a placebo effect, I’m afraid.

As a minimum, you need to repeat the study using several paddlers who do not know which fin setup is being used to even get close to a firm scientific conclusion here.

With this study design you can’t counter the argument that all you are showing is that you have invested a lot of money and time and effort in the installation and so are unconsciously paddling better when that setup is in. These kinds of (genuinely) unconscious physical placebo effects can be huge. If you believe it works, it probably will.

Area -10 with all respect. I have been studying and doing this for over 45 years. Especially with this concept for 7 years of Race Twins. Now tests were done by a well respected guy on this forum who you have praised in the past now call it a Placebo effect, LOL! I bet you haven't even rode my setup but yet make comments about it, after thousands of people paid to have their boards converted from before to after with good results. So if any Placebo effect is going on here my friend it's listening to you!

[Larry Allison]

https://www.youtube.com/watch?v=v5uCogq9OqA

[Larry Allison]

https://www.youtube.com/watch?v=qiV3cqZOlik

[Larry Allison]

https://www.youtube.com/watch?v=-_8doBgClOU

[ukgm]

Could still be a placebo effect, I’m afraid.

As a minimum, you need to repeat the study using several paddlers who do not know which fin setup is being used to even get close to a firm scientific conclusion here.

With this study design you can’t counter the argument that all you are showing is that you have invested a lot of money and time and effort in the installation and so are unconsciously paddling better when that setup is in. These kinds of (genuinely) unconscious physical placebo effects can be huge. If you believe it works, it probably will.

That's a fair point but I knew you'd say that and I have accounted for that (and there is no way you could blind test this technology reliably anyway). As a result, I also performed some coast down tests of both set ups using some other sensors which will show the differences in raw drag. As no paddling takes place (and you're putting Sir Isaac Newton in the driving seat), placebo can't be a factor. I haven't shown that data yet as:

a) It samples at 100Hz so will take some time to process.
b) I want to publish the test as part of a larger study so won't detail it publicly.
3) It's complimentary to this one and if I see that one is more beneficial on one test and not on the other, I need to think about what that means.

I may put the basic results up of this shortly though. However, using a large sample of paddlers won't work as that only demonstrates if a concept is beneficial generally and that's not actionable intelligence for me as I know the specific set up of any fin is very board and paddler specific.

One last thing - whilst it doesn't contend with placebo directly, note that I'm gettings CV's of 2-3% from my trials of both fin set ups (data variability for those not into their stats). For sports science stuff, that's lab quality repeatability so my controls of my field tests are likely to be pretty decent. If there is placebo, its extremely stable as an effect.

[Area 10]

That sounds interesting. But here’s a couple of extra points:

1. Of course it would be possible to do the test with the paddlers blind to the fin setup. I’ve done experiments with much harder manipulations than that!

2. The principle you are trying to establish, surely, is whether the LA system is better than a single fin? This principle requires that it is true of most people, not just of you. So you do need a variety of paddlers. Not least of course this is because the system maybe be sensitive to things like paddle style or weight etc. We learn little from only knowing how *you* are with these fin setups. You may be atypical (in fact, we know you are).

3. With fins, what aids you in one situation can hinder you in another. So just because a setup is faster in windless flat water when you are paddling alone does not mean it will be faster in real race conditions, or in the sea, etc. So ideally you’d test the setups with a variety of paddlers in a variety of conditions.

It is tough to test fins scientifically in such a way that the results are more than just marketing. But some basic drag-type tests might at least remove the human factor, even if it might not actually translate to faster speeds in real-world racing. For instance, a board might be better perhaps in a slow-down test if it is tracking more truly (under some conditions at least). Yet more tracking of this type might well impede speed when downwinding.

[ukgm]

That sounds interesting. But here’s a couple of extra points:

1. Of course it would be possible to do the test with the paddlers blind to the fin setup. I’ve done experiments with much harder manipulations than that!

2. The principle you are trying to establish, surely, is whether the LA system is better than a single fin? This principle requires that it is true of most people, not just of you. So you do need a variety of paddlers. Not least of course this is because the system maybe be sensitive to things like paddle style or weight etc. We learn little from only knowing how *you* are with these fin setups. You may be atypical (in fact, we know you are).

3. With fins, what aids you in one situation can hinder you in another. So just because a setup is faster in windless flat water when you are paddling alone does not mean it will be faster in real race conditions, or in the sea, etc. So ideally you’d test the setups with a variety of paddlers in a variety of conditions.

4. It is tough to test fins scientifically in such a way that the results are more than just marketing. But some basic drag-type tests might at least remove the human factor, even if it might not actually translate to faster speeds in real-world racing. For instance, a board might be better perhaps in a slow-down test if it is tracking more truly (under some conditions at least). Yet more tracking of this type might well impede speed when downwinding.

1. It wouldn't. Not only could you not keep the change visibly covert but both systems feel different when you paddle. Not only that, you need to test at an appropriate velocity (I went for a racing specific 9kph). I don't think such tests could find a sample to do this reliably. Plus, as I say, even if you did, the answer needs to be specific to a paddler, not a sample. The latter is relevant for a manufacturers claims but the former more relevant for a paddlers performance needs.

2. No, it's to see whether its better for me and me alone. The benefits to a broader cross section aren't my concern and I don't need the benefits of penalties to be averaged out across a sample. That's not what I set out to prove. It's the same with my cycling set up for example - it's tailored to me and other riders may well go slower with it. Its the difference between commercial needs and competitive sports engineering.

3. Agreed and I have not claimed otherwise. I change my tyre pressures if my race road surface is different or i may wear a different skinsuit based on air speed. This is no different.

4. Yep, agreed. I'm still trying to work my way through that data now but as I know you'd know, sometimes a bit of reflection and headscratching is needed before banners get waved. For example, a boards slow down is non-linear so I'm trying to work out how to normalise all the runs against each other as the starting velocity and final velocity won't always be the same in each run. I need to be able to get them comparable.

The bottom line is would I use the Allison set up in my races, yes, some. Would I for all of them ? - no but gaining the objective understanding to make this decision is what I'm doing here. Having been asked to read and comment on both Starboards and Fanatics 2019 catalogues recently, I just can't bear any more pseudo science bullcrap.