Ventral Fin and fin tests

[Larry Allison]

Hello Larry/Bill,
Just trying to reconcile this with the size of the central/kick fin having increased over the past years from the original to the current 6" Stinger.
As far as I know the 6" Stinger is the de facto recommended kick fin for the Blackfish.
Does the center fin also provide projection like the ventral or should it be kept smaller as suggested by Bill.

Cheers,
Luc

The conditions even in multiple fin world plays out. If you are in calm,flat water where you have no interference with Mother Nature or running a low volume board that sets deeper in water and are light weight then smaller kick fin.

If Mother Nature plays a roll and conditions are pushing along with a high volume board that sets higher on water along witha strong paddle tongue from rider, then bigger kick. remember concave in the tail like Starboard and Infinity already gives for a larger fin because concave make the fin sit deeper from the water line.

[Luc Benac]

Got it.

[PonoBill]

Hello Larry/Bill,
Just trying to reconcile this with the size of the central/kick fin having increased over the past years from the original to the current 6" Stinger.
As far as I know the 6" Stinger is the de facto recommended kick fin for the Blackfish.
Does the center fin also provide projection like the ventral or should it be kept smaller as suggested by Bill.

Cheers,
Luc

I'm not in any position to give advice. I'm in the dazed and confused category.

[supbarton]

Ponobill,
Install looks good.  If you wanted to hide the patchwork on the black carbon boards you can get some Rustoleum black spray enamel and lightly paint it.  Wait a day and then wet sand.  It blends it right in.  I've done a lot of black carbon repairs.  Just finished a retro fit on a 2016 Blackish and had to move the ventral box for the owner back toward the balance point about 12".

The White boards make it very easy to hide the repairs and fin box installs.  This one I will paint once I test ride the board and make sure it worked for the owner.

[Larry Allison]

Hello Larry/Bill,
Just trying to reconcile this with the size of the central/kick fin having increased over the past years from the original to the current 6" Stinger.
As far as I know the 6" Stinger is the de facto recommended kick fin for the Blackfish.
Does the center fin also provide projection like the ventral or should it be kept smaller as suggested by Bill.

Cheers,
Luc

I'm not in any position to give advice. I'm in the dazed and confused category.

Bill I think you are the exact guy for advice, because you are feeling what I have been tryng to explain and more importantly by your comments you are speaking fin SUP language. There is alot going on but becomes simple when you understand the language my friend. 

[Larry Allison]

Ponobill,
Install looks good.  If you wanted to hide the patchwork on the black carbon boards you can get some Rustoleum black spray enamel and lightly paint it.  Wait a day and then wet sand.  It blends it right in.  I've done a lot of black carbon repairs.  Just finished a retro fit on a 2016 Blackish and had to move the ventral box for the owner back toward the balance point about 12".

The White boards make it very easy to hide the repairs and fin box installs.  This one I will paint once I test ride the board and make sure it worked for the owner.

Alright Barton is in the House. Nice work!

[ukgm]

UK, I suspect you're right about the refresh for SpeedCoach being triggered by stroke. Makes sense for what it's made for. I didn't think of tagging fin changes by distance. Duh.

I'm heading out to test another 4 fins in the morning while I still have something left of summer to play with.

(Trawling through the data I have so far, I'm pleased that on my second attempt of playing with test methodologies, not only have I managed to get great data repeatability, I also (and Area 10 will appreciate this) managed to obtain statistical significance between some fin performances too. I have completely misjudged fin potency and importance)

[PonoBill]

(Trawling through the data I have so far, I'm pleased that on my second attempt of playing with test methodologies, not only have I managed to get great data repeatability, I also (and Area 10 will appreciate this) managed to obtain statistical significance between some fin performances too. I have completely misjudged fin potency and importance)

Apparently I have too. Are you testing three-fin setups?

I found another monkeywrench yesterday, or rather, confirmed (sort of) another factor I found but kind of ignored. Paddle choice is a factor in fin performance. 84 Konihi vs. 90 Mana somewhat reverses results. With the Mana 90, the stock center fin is faster than the little ventral fin in the center position. With the 84 Konihi the little ventral fin is faster. About a two percent difference. 84 Konihi with ventral is a little faster than 90 Mana with stock fin, about a one percent difference. I did only one short run with each, so the numbers are approximate and suspect.

I'm very tempted to paint that pretty carbon fiber bottom a basic white. I don't dare leave the thing in the sun for ten seconds. I'm considering adding another center fin box ahead of the stock position. I think I might be able to make this thing steer on a downwinder if I do. One more modification and I'm just gonna paint the thing. It will look like a frankenboard anyway. What do you think of a forward fin position with your cutaway fin Larry?

[Luc Benac]

Hey Bill,
you almost need a table of definitions of the fins and an Excel spreadsheet with the combination and results.

So your latest results look like:
Larger surface blade => larger surface central/kick fin
Smaller surface blade => Smaller surface central/kick fin

My fins and boxes should be arriving hopefully this week and I should have the board retrofitted the first week of October. I can then test with both the Mana 82 and Mana 90 (same blade shape, different surface) but I will need to borrow a small kick fin from the friend I sold my previous board to. Curious to see if this also apply to a weaker and lighter paddler.

Cheers,

Luc

[Larry Allison]

(Trawling through the data I have so far, I'm pleased that on my second attempt of playing with test methodologies, not only have I managed to get great data repeatability, I also (and Area 10 will appreciate this) managed to obtain statistical significance between some fin performances too. I have completely misjudged fin potency and importance)

Apparently I have too. Are you testing three-fin setups?

I found another monkeywrench yesterday, or rather, confirmed (sort of) another factor I found but kind of ignored. Paddle choice is a factor in fin performance. 84 Konihi vs. 90 Mana somewhat reverses results. With the Mana 90, the stock center fin is faster than the little ventral fin in the center position. With the 84 Konihi the little ventral fin is faster. About a two percent difference. 84 Konihi with ventral is a little faster than 90 Mana with stock fin, about a one percent difference. I did only one short run with each, so the numbers are approximate and suspect.

I'm very tempted to paint that pretty carbon fiber bottom a basic white. I don't dare leave the thing in the sun for ten seconds. I'm considering adding another center fin box ahead of the stock position. I think I might be able to make this thing steer on a downwinder if I do. One more modification and I'm just gonna paint the thing. It will look like a frankenboard anyway. What do you think of a forward fin position with your cutaway fin Larry?

Bill, Try the Dolphin Single fin I sent you and the Cutaway, moved forward in your board  before adding a box. Or if you are not happy I will get you a Aercor for downwinding. Mahalo

[BroDog]

I raced this past Sunday in the Beyond the Shore Paddlefest inRedondo Beach. The 2 mile "Fun Race" started at 10:45am which meant the wind and swell was kicking up. The race was a simple one mile paddle straight out of King Harbor, a turn at the buoy, and one mile back into the harbor.  By late morning the swells were hitting us from both the north and south. In addition, there was swells bouncing back from the break wall behind us. The fun race turned out to be quite a work out.

I had the Allison 4 fin set up on my Blackfish, but chose to use a larger medium ventral fin for stability. My observation for this tread is that not only was stability good, but I was able to paddle in a relatively straight line (tracking) and not be pushed left and right by the ocean. Much of my energy was devoted to paddling rather than keeping my board straight. No need for excessive paddling on one side to keep my heading.

In reviewing my Gopro pics, I noticed paddlers behind me would consistently show up to my left and then to my right. Wasn't looking for this, but seems like a confirmation that I was tracking true. Overall, it was a very satisfying experience. By the way, I was the oldest paddler of 50 racers!

[Larry Allison]

I raced this past Sunday in the Beyond the Shore Paddlefest inRedondo Beach. The 2 mile "Fun Race" started at 10:45am which meant the wind and swell was kicking up. The race was a simple one mile paddle straight out of King Harbor, a turn at the buoy, and one mile back into the harbor.  By late morning the swells were hitting us from both the north and south. In addition, there was swells bouncing back from the break wall behind us. The fun race turned out to be quite a work out.

I had the Allison 4 fin set up on my Blackfish, but chose to use a larger medium ventral fin for stability. My observation for this tread is that not only was stability good, but I was able to paddle in a relatively straight line (tracking) and not be pushed left and right by the ocean. Much of my energy was devoted to paddling rather than keeping my board straight. No need for excessive paddling on one side to keep my heading.

In reviewing my Gopro pics, I noticed paddlers behind me would consistently show up to my left and then to my right. Wasn't looking for this, but seems like a confirmation that I was tracking true. Overall, it was a very satisfying experience. By the way, I was the oldest paddler of 50 racers!

Don't forget Brodog you took a first along with 17th over all against some pretty good paddlers half your age.Probably higher if the guy didnt ram you sideways at the turn throwing you in the water a mile out.

[BroDog]

Hahaha…Good times ProBox!!!

[mrbig]

BroDog, Old guys doin' stuff! Huge ups dawg!!

[PonoBill]

Hey Bill,
you almost need a table of definitions of the fins and an Excel spreadsheet with the combination and results.

So your latest results look like:
Larger surface blade => larger surface central/kick fin
Smaller surface blade => Smaller surface central/kick fin

My fins and boxes should be arriving hopefully this week and I should have the board retrofitted the first week of October. I can then test with both the Mana 82 and Mana 90 (same blade shape, different surface) but I will need to borrow a small kick fin from the friend I sold my previous board to. Curious to see if this also apply to a weaker and lighter paddler.

Cheers,

Luc

Actually I think it's more a matter of the catch differences in the Mana vs Konihi, though at this point any explanation will work for me. For me, the Mana catches big right away, and then softens up a little as I pull it. The Konihi catches softer, but pulls hard all the way to the end of the stroke. the Konihi also pulls straighter, no draws allowed, it just won't do it, and I have to push the Konihi deep--good for the Puakea stroke--or it gurgles.

If I was going to theorize, it would be that the Mana, catching way out front, is torquing the board more, and needs the bigger kick fin. The Konihi pulls steady and straight so it doesn't torques as much. At least that's my story for this afternoon. I think I'm learning a lot, I'm just not sure what.

Fortunately I just stumbled on a cache of two Larry Allison ventral fins that I have for my Speedboard. One bigger than the one I have, and one smaller. They aren't the click-in fins, they have a normal fin screw, but they'll be great for further testing. I'd go out now but the wind is up a bit.