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General Category => Gear Talk => Topic started by: Henrik F on January 03, 2013, 05:12:46 AM

Title: The ventral fin from Larry W. Allison
Post by: Henrik F on January 03, 2013, 05:12:46 AM
I've been out today trying the ventral fin from Sup Race Fins, Larry W. Allison. In a bit choppy conditions. First I paddled without the ventral and just a Ninja. Then with the ventral fin and the board was a lot more stable. Not tippy at all :)
Then I paddled into the more calm conditions in the marina. I like the Ninja because it allows me to take more strokes per side than the fin that comes with the board. But with the ventral fin attached... It felt like I could have gone on and on. This is a serious improvement. Probably to any board that you use in flatwater or chops, whitecaps... Brilliant!

Henrik F

Title: Re: The ventral fin from Larry W. Allison
Post by: raf on January 03, 2013, 05:36:47 AM
Sweet!  Looks organic.  There's a reason millions of years of evolution have put fins up there on fishes.  It must work good.
Title: Re: The ventral fin from Larry W. Allison
Post by: bbqSUPer on January 03, 2013, 01:32:51 PM
How did you come up with where to place it?
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on January 03, 2013, 02:00:49 PM
How did you come up with where to place it?

I spoke to Larry and had to do some measuring from where I usually stand on the board.

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: mik911 on January 03, 2013, 10:52:32 PM
So I assume you need to have a shop put in a finbox?
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on January 03, 2013, 11:09:16 PM
So I assume you need to have a shop put in a finbox?

In my case, ABSOLUTELY :) But I think that people who are more familiar with reparing boards and such could do it.

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: upwinder on January 04, 2013, 12:04:21 AM
Hey Henrik - nice work. Here's a couple of pics of my ventral/PCF setup* on my 2010 Naish 17'

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FNaish1_zps53c1f49d.jpg&hash=35e9a9f1e5e2fb83eaa7cc6de4640d6d)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FVent_3.jpg&hash=42634d1960b4031c8e39ee22f483829e)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FNaish2.jpg&hash=eb24019ce415db768d1263e51daa031f)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FCleanDeck-1.jpg&hash=f2194fbbbdb24992a51fae670342dcb9)

I've taken the steering mech off and in flat water I can comfortably stand well forward of the handle, giving me about 16' of waterline**. It changes the character of the board significantly...it's a much more viable distance cruiser/trainer now with several 15-20+ km runs completed this season. The ventral stabilises things very well in side chop and when I'm standing up forward. It improves tracking enormously, yet when I take a couple of steps back to turn it the ventral lifts out of the way enough not to interfere. I originally bought the ventral to put in the yellow 14' race board behind it but I sold that board and had the forward fin box fitted in the 17 instead, glad I did.  Colour me happy  ;D

(*the ventral box is fitted 20" forward of the board's balance point, per Larry's instructions...right where it should be)

(**for some reason my 17 is a good bit flatter in the rocker line than other Naish 17s I've seen...this is a bonus for my purposes, possibly limits its potential in big open water but I don't care about that)



Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on January 04, 2013, 02:41:15 AM
Hey Henrik - nice work. Here's a couple of pics of my ventral/PCF setup* on my 2010 Naish 17'

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FNaish1_zps53c1f49d.jpg&hash=35e9a9f1e5e2fb83eaa7cc6de4640d6d)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FVent_3.jpg&hash=42634d1960b4031c8e39ee22f483829e)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FNaish2.jpg&hash=eb24019ce415db768d1263e51daa031f)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FCleanDeck-1.jpg&hash=f2194fbbbdb24992a51fae670342dcb9)

I've taken the steering mech off and in flat water I can comfortably stand well forward of the handle, giving me about 16' of waterline**. It changes the character of the board significantly...it's a much more viable distance cruiser/trainer now with several 15-20+ km runs completed this season. The ventral stabilises things very well in side chop and when I'm standing up forward. It improves tracking enormously, yet when I take a couple of steps back to turn it the ventral lifts out of the way enough not to interfere. I originally bought the ventral to put in the yellow 14' race board behind it but I sold that board and had the forward fin box fitted in the 17 instead, glad I did.  Colour me happy  ;D

(*the ventral box is fitted 20" forward of the board's balance point, per Larry's instructions...right where it should be)

(**for some reason my 17 is a good bit flatter in the rocker line than other Naish 17s I've seen...this is a bonus for my purposes, possibly limits its potential in big open water but I don't care about that)





That is a beautiful job you've done there! And I went just under 20" too when I had the fin installed. I will have to wait for a bit more decent weather conditions before putting on kms. It is seriously cold here in Sweden now. The ice has been melting for a while but it will surely be back :(

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: upwinder on January 04, 2013, 06:00:03 AM

. I will have to wait for a bit more decent weather conditions before putting on kms. It is seriously cold here in Sweden now. The ice has been melting for a while but it will surely be back :(

Henrik F

Man, that looks cold. More power to you for getting out there

(If it helps warm you up some, a group of about 10 of us down here enjoyed an awesome downwinder this morning in 40C heat... No wetsuits today  ;D )
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on January 04, 2013, 06:13:30 AM

. I will have to wait for a bit more decent weather conditions before putting on kms. It is seriously cold here in Sweden now. The ice has been melting for a while but it will surely be back :(

Henrik F

Man, that looks cold. More power to you for getting out there

(If it helps warm you up some, a group of about 10 of us down here enjoyed an awesome downwinder this morning in 40C heat... No wetsuits today  ;D )

I got really warm now. Of envy  :D

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: surf monkey on January 04, 2013, 10:20:04 AM
I think the fin is a cool idea but how is it in a down winder? I understand the board is more stable but will it cause the board to start tracking when your at speed on the bumps or keep the board from releasing when trying to get the bump?

So with the forward fin in could you go with a smaller rear fin to reduce the drag? or would that make a difference?

Thanks
Title: Re: The ventral fin from Larry W. Allison
Post by: jd on January 04, 2013, 11:28:41 AM
I did one of the first ones of these with Larry.  I was one of his guinea pigs.   :P

This is from 2008.  How time flies.

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww2.swaylocks.com%2Ffiles%2F1030395_sup%2520001%2520%282%29.jpg&hash=b429e167cc9566c729de60456d5b3f18)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww2.swaylocks.com%2Ffiles%2F1030394_sup%2520004%2520%282%29.jpg&hash=653093a93d838f4ae6f3f758d379e99b)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww2.swaylocks.com%2Ffiles%2F1030396_sup%2520005%2520%282%29.jpg&hash=c9969f28511f69d9d85f711c4b0294dc)
Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on January 04, 2013, 01:09:33 PM
Looks like it's time to get in touch with Larry again. ;) I am considering adding this to my 14' M&M. Thanks for feedback Henrik!
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on January 04, 2013, 01:36:58 PM
Looks like it's time to get in touch with Larry again. ;) I am considering adding this to my 14' M&M. Thanks for feedback Henrik!

No problem!

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: corlot on January 04, 2013, 03:06:10 PM



     
   
"Re: The ventral fin from Larry W. Allison
« Reply #12 on: Today at 04:09:33 PM »   
Looks like it's time to get in touch with Larry again.  I am considering adding this to my 14' M&M. "

14 M&M?! When did that happen?
Title: Re: The ventral fin from Larry W. Allison
Post by: upwinder on January 04, 2013, 03:17:38 PM
I think the fin is a cool idea but how is it in a down winder? I understand the board is more stable but will it cause the board to start tracking when your at speed on the bumps or keep the board from releasing when trying to get the bump?

So with the forward fin in could you go with a smaller rear fin to reduce the drag? or would that make a difference?

Thanks


Good question, I may have something of an answer. I haven't used the 17 on a DW since fitting the fin (we typically have quite short-period swells here and rockered 14s just work better). Interestingly the 14' board I DW on came ex-factory with a ventral in box fitted (here's a pic or two) and I've experimented a little.

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FWoW2_zps3c77977a.jpg&hash=1273a21f6e22f5b94823ab4896cd5645)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fi168.photobucket.com%2Falbums%2Fu178%2Farmchair_spaceman%2FWoWVentral_zps11325f00.jpg&hash=bcf217599e1d1848a2092ef9cd3fdf5d)

The WoW ventral is about 1/3 the size of Larry's

Here it's rare that swell and wind line up perfectly and our waters can be quite chopped up and confused, especially on lighter (15-20knot) days. In these lighter wind, confused conditions I've found the combo of the bigger Larry ventral plus the red PCF fin (as seen in my earlier post) works better than the smaller fins because tracking through the slop to maintain a heading becomes a bit more important

On big days, above 25-30 knots like yesterday, the swell and wind tend to line up better, then I prefer the combo of the smaller WoW ventral and a 10-10.5" dolphin style fin because it feels a bit more surfy.

In both cases I reckon the ventral contributes to tracking between runners but doesn't seem to interfere with release/performance on a runner when my weight is back on the board.

BUT...when I tried the bigger Larry ventral with an upright, smaller base tail fin (the one pictured in the orange board, only has about 5" base compared to the 8" base of the Larry Ventral and it doesn't have much area in the tip) things turned to crap.  The ventral seemed to dominate the tail fin, the board wanted to pivot around the ventral and was very difficult to control. The smaller WoW ventral (base about 3 1/2" doesn't have that effect with the smaller tail fin and together they seem to work nicely in more orderly conditions when the swell and wind line up. The bigger Larry ventral works well with a bigger area/base/tip tail fin.

So it seems to me there's a size relationship between tail fin and ventral that one needs to be mindful of (maybe Larry could comment on that if he's watching).

I should maybe add the qualification that I'm a big clumsy guy (6'2, around 265) and  boards /fins do behave differently with big units like me on them so YMMV.
Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on January 05, 2013, 03:37:05 PM
14 M&M?! When did that happen?

Corey, got the 14' M&M a few weeks before Bjord the Fjord.
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 06, 2013, 10:47:44 PM
I did one of the first ones of these with Larry.  I was one of his guinea pigs.   :P

This is from 2008.  How time flies.

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww2.swaylocks.com%2Ffiles%2F1030395_sup%2520001%2520%282%29.jpg&hash=b429e167cc9566c729de60456d5b3f18)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww2.swaylocks.com%2Ffiles%2F1030394_sup%2520004%2520%282%29.jpg&hash=653093a93d838f4ae6f3f758d379e99b)

(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww2.swaylocks.com%2Ffiles%2F1030396_sup%2520005%2520%282%29.jpg&hash=c9969f28511f69d9d85f711c4b0294dc)


jd, See what you did! Just kidding. Thanks for pushing things my friend. Here's a pic of the transition of Allison Ventral Sup Fins from the large Ventral fin 6" of jd's 12'6" Ron House of 5 years ago to the Hi Performance Flex Ventral Fin 2" of today.
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 06, 2013, 11:02:48 PM
I think the fin is a cool idea but how is it in a down winder? I understand the board is more stable but will it cause the board to start tracking when your at speed on the bumps or keep the board from releasing when trying to get the bump?

So with the forward fin in could you go with a smaller rear fin to reduce the drag? or would that make a difference?

Thanks

Surf Monkey you are right, when added a Allison Ventral fin concept you can go down in rear fin size depending on conditions and boards. The middle board in the pic is a 12'6" board with a 2" Ventral Sup Fin and a 7" rear Stealth Fin.

Also because of the location of the Allison Ventral fin it won't interferance  with the performance aspect of catching a bump, like in the pic below with Brandon Sauls riding the 12'6" board in this last BOP at Dana Point coming in 3rd in his group.
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 06, 2013, 11:16:17 PM
I run a small 2" Red Flex Ventral with a Ninja on my 14' Bark in pic. In the open ocean I sometimes use the larger Black Ventral like seen in the pic Below. The pic below shows me flexing the smaller Ventral fin which is foiled in a "S" flex.
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 06, 2013, 11:36:47 PM
Looks like it's time to get in touch with Larry again. ;) I am considering adding this to my 14' M&M. Thanks for feedback Henrik!

Westbeach, Here's some pics of a 14' M&M with the Allison Ventral Sup Fin set up. Notice the M&M has 3 different fin setups using the 3 1/2" Ventral fin in all 3 pics. Along with 6 1/2" Dolphin Keel, 7" Stealth and 6 3/4" Gladiator for Rear fins in this M&M.
Title: Re: The ventral fin from Larry W. Allison
Post by: corlot on January 07, 2013, 08:46:52 AM
Awesome info Larry!! I think I need to contact you on putting one on my Starboard Ace Pro 25''. The narrow width and my weight of 188lbs can be a handful in choppy conditions.

Can anyone tell me an approximate level of stability it will increase with the smaller ventral fin? Really interested in this discussion.

Thanks again Larry for being so helpful!
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 07, 2013, 09:08:04 AM
Awesome info Larry!! I think I need to contact you on putting one on my Starboard Ace Pro 25''. The narrow width and my weight of 188lbs can be a handful in choppy conditions.

Can anyone tell me an approximate level of stability it will increase with the smaller ventral fin? Really interested in this discussion.

Thanks again Larry for being so helpful!

Remember corlot, The smaller Ventral fin still has a 8" core length. It as to do with flex along with placement in relation to paddle power and depth for drag. If you go to short of core length the Ventral Fin actually has a negative effect and is noticed in your paddling to give you the feel of a tugging on your board and start to yaw again pulling you side to side which is different then the feel of towing something when the Ventral Fin is oversized or I should say when the pair (Ventral and Rear are oversized). Don't forget balance of fins just like the center fin in the single world balance to the board and conditions. People will tend to focus on one elimente and forget the rule of Balance.
Title: Re: The ventral fin from Larry W. Allison
Post by: Area 10 on January 07, 2013, 09:57:41 AM
Guys, bear with me for being so pedantic, but, please, before this term takes irrevocable hold upon our community, can I please ask for a possible change in the term used?

The term "ventral" is not a good one to describe this type of fin. "Ventral"just means on the underside or belly. So all fins are "ventral". What you need is a word that describes the forward placement of the fin, which is the special thing about it, not the fact that it is pointing into the water. If you want to adopt a terms from anatomy (like "ventral") to do this, then probably the most accurate term to use would be "rostral". Rostral means "in the direction of the nose" of something, so would seem particularly appropriate for this situation. You could also call it an "anterior fin", perhaps.

Or maybe if you just want to use plain language, then "rear fin" (for the normal fin) and "front fin" would do just fine - although sound far less impressively scientific...
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 07, 2013, 11:23:52 AM
Guys, bear with me for being so pedantic, but, please, before this term takes irrevocable hold upon our community, can I please ask for a possible change in the term used?

The term "ventral" is not a good one to describe this type of fin. "Ventral"just means on the underside or belly. So all fins are "ventral". What you need is a word that describes the forward placement of the fin, which is the special thing about it, not the fact that it is pointing into the water. If you want to adopt a terms from anatomy (like "ventral") to do this, then probably the most accurate term to use would be "rostral". Rostral means "in the direction of the nose" of something, so would seem particularly appropriate for this situation. You could also call it an "anterior fin", perhaps.

Or maybe if you just want to use plain language, then "rear fin" (for the normal fin) and "front fin" would do just fine - although sound far less impressively scientific...

You are right Area 10, when I was using the term Dagger fin everyone starting comparing and putting the fin box in their boards like a Windsurfer which is wrong placement. So I thought Ventral like a fish #11 called a pelvic(Ventral) #12 called the Anal Fin and #13 called the Finlet, but Ventral is the rear fin at the bottom of a plane to control yaw or roll in simple terms. So yes I can see your concern my friend if Ventral is used in a Fish world it is the opposite of Dorsal. But in the Airplane world it's at the rear slightly forward. Let me think about it and I will come up with something. Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 07, 2013, 11:55:49 AM
Guys, bear with me for being so pedantic, but, please, before this term takes irrevocable hold upon our community, can I please ask for a possible change in the term used?

The term "ventral" is not a good one to describe this type of fin. "Ventral"just means on the underside or belly. So all fins are "ventral". What you need is a word that describes the forward placement of the fin, which is the special thing about it, not the fact that it is pointing into the water. If you want to adopt a terms from anatomy (like "ventral") to do this, then probably the most accurate term to use would be "rostral". Rostral means "in the direction of the nose" of something, so would seem particularly appropriate for this situation. You could also call it an "anterior fin", perhaps.

Or maybe if you just want to use plain language, then "rear fin" (for the normal fin) and "front fin" would do just fine - although sound far less impressively scientific...

You are right Area 10, when I was using the term Dagger fin everyone starting comparing and putting the fin box in their boards like a Windsurfer which is wrong placement. So I thought Ventral like a fish #11 called a pelvic(Ventral) #12 called the Anal Fin and #13 called the Finlet, but Ventral is the rear fin at the bottom of a plane to control yaw or roll in simple terms. So yes I can see your concern my friend if Ventral is used in a Fish world it is the opposite of Dorsal. But in the Airplane world it's at the rear slightly forward. Let me think about it and I will come up with something. Mahalo, Larry

Area 10, I gave it some thought and I like the flow of "Anterior Ventral Sup Fin" Thanks my friend. We just confirmed and set the pace for others to follow. Thanks for your guidance this comes together nicely after 5 years of playing with this concept. Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on January 07, 2013, 12:18:05 PM
I've been out today trying the ventral fin from Sup Race Fins, Larry W. Allison. In a bit choppy conditions. First I paddled without the ventral and just a Ninja. Then with the ventral fin and the board was a lot more stable. Not tippy at all :)
Then I paddled into the more calm conditions in the marina. I like the Ninja because it allows me to take more strokes per side than the fin that comes with the board. But with the ventral fin attached... It felt like I could have gone on and on. This is a serious improvement. Probably to any board that you use in flatwater or chops, whitecaps... Brilliant!

Henrik F



What I forgot to mention is that the Anterior ventral Sup fin also eliminated the very irritating backwash from the jetty. The board became so stable.

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 07, 2013, 04:34:35 PM
Thought I would share some more "Allison Anterior Ventral Sup Fin" set-ups from 12'6" to unlimited class. Enjoy the ride and Thanks for the support my friends. Mahalo,Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: Area 10 on January 07, 2013, 05:36:09 PM
Area 10, I gave it some thought and I like the flow of "Anterior Ventral Sup Fin" Thanks my friend. We just confirmed and set the pace for others to follow. Thanks for your guidance this comes together nicely after 5 years of playing with this concept. Mahalo, Larry

Yep, that works. Maybe we might find it easier to say e.g. "AVS fin" for day-to-day use?

I've got to get one of these fitted to my 17...
Title: Re: The ventral fin from Larry W. Allison
Post by: jdmotes on January 07, 2013, 05:46:22 PM
  Since I like to 'keep it simple' with the use of initials, I'm with A10 and calling it an AVS system  ;D...          Paddle on,     JD
Title: Re: The ventral fin from Larry W. Allison
Post by: corlot on January 07, 2013, 06:50:49 PM
Hi Larry,

Sending a pm.

Thanks,
Corey
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 07, 2013, 08:31:01 PM
Hi Larry,

Sending a pm.

Thanks,
Corey

Pm answered my friend. Mahalo
Title: Re: The ventral fin from Larry W. Allison
Post by: mtmilam on January 07, 2013, 10:15:41 PM
How Does one install a AVS fin to a board that doesn't have a box for it.....I've worked with epoxy and fiberglass foam building Airplanes and boats....I assume you cut out a box shape thru the skin and foam and Epoxy the box for the new fin in the space.......or something like that :D

There is no one that repairs boards in Louisiana....Is there a "how to " site somewhere that shows how to do it?? 

Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 07, 2013, 10:34:12 PM
How Does one install a AVS fin to a board that doesn't have a box for it.....I've worked with epoxy and fiberglass foam building Airplanes and boats....I assume you cut out a box shape thru the skin and foam and Epoxy the box for the new fin in the space.......or something like that :D

There is no one that repairs boards in Louisiana....Is there a "how to " site somewhere that shows how to do it?? 



Mt, It's not that hard especially with your back ground. Call me at the factory 310-530-1383. I will work thru it with you my friend. Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: upwinder on January 08, 2013, 03:37:03 AM

I've got to get one of these fitted to my 17...

You'll be glad you did  ;)
Title: Re: The ventral fin from Larry W. Allison
Post by: SEA on January 08, 2013, 05:48:08 AM
Hi Larry

is there a formula for deciding the placement of the AVS fin system? Do conditions of area paddling dictate how far forward or back towards the tail one would place the box ??

Mahalo Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: greatdane on January 08, 2013, 07:57:39 AM
The only way to fly a 19 footer (-:

Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on January 08, 2013, 10:09:55 AM
Aloha Larry,

Please check your pm! Stoked to be part of the LA movement!

Mahalo,
Neal
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 08, 2013, 02:03:58 PM
Hi Larry

is there a formula for deciding the placement of the AVS fin system? Do conditions of area paddling dictate how far forward or back towards the tail one would place the box ??

Mahalo Larry


Yes SEA I do have a formula for AVS fin box placement. There are 2 ways to reach the same result in placement.

1.) If you have a favorite board that you want to retro the AVS set up to then this is the step for that:

  Find the sweet spot of your board where you stand and mark 15 inches forward from your big toe to the back of the Hi Surf 10 1/2" box made by Larry Allison. This will put the AVS box set up in line to your paddle stroke length on that board.

2.) If you are getting a new board never riden by you then this is the measurement process for that:

  Find the BALANCE POINT of the board that you are going to install the AVS set up. Mark from the BALANCE POINT of the board forward 20 inches to the back of the 10 1/2" Hi Surf box made by Larry Allison. This will put you in the saftey Zone placement to adjust your AVS fin to fine tune the board to your liking.


When you use the 2nd install of the AVS Fin Box I already take in to account that 95% of us stand 3 to 5 inches forward of center point of that on any board, verses set up number one to a already know stance on the board being ridden. Important not to get confused and set the AVS Box to far back, because this will cause the AVS FIN to cause reaction with the rear fin.

Nice to see the movement take effect. Remember these comments from others: 1) We already did Front fins years ago like Eaton on prone boards. My answer is you don't get it that placement was further back on a Prone board. 2.) People then compare to Windsurfer Dagger box placement. My answer is that placement is a pivot point which inter fears with the rear fin causing you to go in circles increasing your yaw nightmare to be worse. I have ridden my 14' board with a center fin and reverse the setup like some companies like in the pic below. Makes your 14' turn easy but hard to keep straight even with a rear kick fin. Still playing with this idea but one thing I already know very limited to function just haven't figure out the exact limitations yet with a center box not to get confused with the AVS set up forward of center.

Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on January 11, 2013, 01:17:10 PM
Hi Larry,

Did you get my pm? Thank You.
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 11, 2013, 01:36:33 PM
Hi Larry,

Did you get my pm? Thank You.

Yes, Did you get my reply? Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on January 12, 2013, 12:16:26 AM
Hi Larry,

Sorry; nothing came in my pm box. I think it got lost in cybersurf!  :D Can you please send again!

Thank You
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on January 16, 2013, 09:31:04 PM
Hi Larry,

Sorry; nothing came in my pm box. I think it got lost in cybersurf!  :D Can you please send again!

Thank You

Westbeach, Hope ypu got my 2nd pm my friend. Mahalo
Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on January 17, 2013, 03:16:29 AM
Yes Larry, I did. Thank You. I have replied your pm. I will personally call you up upon my return. I will be out of town till the end of the month. Aloha!

Neal
Title: Re: The ventral fin from Larry W. Allison
Post by: Larry Allison on March 12, 2013, 10:33:12 AM
Looks like it's time to get in touch with Larry again. ;) I am considering adding this to my 14' M&M. Thanks for feedback Henrik!

Just wanted to say thanks for being patient my friends. I know some of you have AVS fins on ordr. Didn't forget you, they are being finished this week. Just a few tweaks to fine tune since these are new to the Allison collection. Want to make sure these work to my liking had to spend more water time first before finishing. Hope you Enjoy the ride my friends. Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on March 12, 2013, 02:06:00 PM
Very nice! I really look forward to recieving the new design.

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: westbeach on March 12, 2013, 05:42:29 PM
Larry, Looking sharp!! And Mahalo for keeping us in the loop as to what you have been up to. That is what is so great about L.A; He doesn't just put out a product for the masses without first proving his design and making sure it works well. <thumbs up!>

Looks like it's time to get in touch with Larry again. ;) I am considering adding this to my 14' M&M. Thanks for feedback Henrik!

Just wanted to say thanks for being patient my friends. I know some of you have AVS fins on ordr. Didn't forget you, they are being finished this week. Just a few tweaks to fine tune since these are new to the Allison collection. Want to make sure these work to my liking had to spend more water time first before finishing. Hope you Enjoy the ride my friends. Mahalo, Larry
Title: Re: The ventral fin from Larry W. Allison
Post by: Henrik F on July 03, 2015, 02:15:24 PM
Hello!
I have now, since early 2013, been paddling with AVS fins. Only touring and raceboards. I started doing so because I wanted a bit more tracking and being able to take some more strokes/side before changing.
What I have noticed that came along with the increased tracking was that the boards became MUCH more stabile. Approximately 2 inches more stabile. This meant that I was able to take on much more challenging conditions.
Some other advantages that appeared were that it is so much easier paddling either with the waves coming in from the side in upwind or downwind. Way easier to hold my intended course! I don't get pushed away from or off the waves as much as before. It also increases my ability to surf the raceboards in a, say, 20° angle on the wave. Footsteering doing a DW is also better and if I get up real speed I will stand so far back on the board that I am lifting the ventral fin out of the water which mean I can steer the board as a surfboard. The lifting goes for bouy turns aswell :)
In flatwater I downsize the ordinary centerfin so increased drag is next to nothing. But sometimes I don't because of the increased tracking so it doesn't really matter.
It might get some increased weight but that is nothing I notice on the water.
So far I've had them installed on a Bark Competitor 2012, Fanatic Fly Race flatwater 14' and a Starboard Allstar 12'6x26,5".

Henrik F
Title: Re: The ventral fin from Larry W. Allison
Post by: PaddleSpot on July 03, 2015, 10:55:29 PM
You are so right, Henrik F  :)

The real question is "Why don't they put a small centerboard on every touring SUP ?"  This is so obvious... Best tracking, increased stability, and a perfectly balanced board when paddling crosswind...



Check this little video : https://vimeo.com/89657512

Title: Re: The ventral fin from Larry W. Allison
Post by: deepmud on July 07, 2015, 09:34:16 PM
That's going to be tough on my Blue Planet isup....  8) maybe I can duct tape one on....
Title: Re: The ventral fin from Larry W. Allison
Post by: blackeye on July 08, 2015, 10:29:45 PM
That's going to be tough on my Blue Planet isup....  8) maybe I can duct tape one on....

Love the idea, but that's going to be tough on my chin or sternum or gut or the jewels at some point.
Title: Re: The ventral fin from Larry W. Allison
Post by: PaddleSpot on July 10, 2015, 01:14:09 AM
blackeye, it's only a prototype, to test the general concept. My daggerboard is generally either down, or strapped on the deck. But I'm really convinced that cruising SUPs should have a pivoting centerboard, like old woindsurfs. The ventral fin is only a first step in this direction.
Title: Re: The ventral fin from Larry W. Allison
Post by: deepmud on July 10, 2015, 09:18:18 AM
I think it's pretty cool - I note the placement is forward rather than in the middle - and WAY larger than Larry's fin. Reminds me of the one that Bart de Zwart came up with for his isup in the Arctic.
(https://www.standupzone.com/forum/proxy.php?request=http%3A%2F%2Fwww.star-board-sup.com%2Fblog%2Fwp-content%2Fuploads%2F2013%2F07%2Fphoto-5-1.jpg&hash=c3b4c752aef2e64ca2de69f27309bcdf)
Title: Re: The ventral fin from Larry W. Allison
Post by: PaddleSpot on July 10, 2015, 09:58:07 AM
The general idea is to counterbalance the effect of the rear fin.  So the closer to the nose the better. The forward position increases the lever, hence allows to reduce the size of the daggerboard. The limit depending on the rocker of the board. The board on the video is a 14' f-one, the one on the picture is a 14' prototype I built last summer, with a rounded hull inspired from canoes. The daggerboard really helps on this kind of shape.
Title: Re: The ventral fin from Larry W. Allison
Post by: photofr on July 10, 2015, 11:23:55 AM
PaddleSpot: I still love your idea…
I was able to try your ventral fin with a French paddler… it really works great !
Couple of things I noticed immediately when testing it out with huge amounts of crosswinds:
1. More stability, right off the bat.
2. Unnoticeable decrease in speed (Gregg Barton says fins provide less than 1% loss, based on his many tests with Epic Kayaks)
3. Using the ventral fin in conjunction with the rudder made the 18' board turn even faster (nice pivot point)
4. The removable aspect is a BIG PLUS
5. It weight nothing… made out of plywood.

Brilliant, just brilliant Olivier !
I'll have to put one on my new 14' x 25" Starboard Race
Title: Re: The ventral fin from Larry W. Allison
Post by: stoneaxe on July 10, 2015, 11:47:36 AM
We need to get Bill to finish the design of his remote control ventral with auto GPS.
Title: Re: The ventral fin from Larry W. Allison
Post by: lucabrasi on July 10, 2015, 11:50:26 AM
We need to get Bill to finish the design of his remote control ventral with auto GPS.
I just think gps minnkota with that for me.
Title: Re: The ventral fin from Larry W. Allison
Post by: BroDog on July 11, 2015, 05:07:39 PM
Saw these recent posts and got me fired up to do some ventral fin placement testing today. The board is an unlimited 17.5' I've been riding for the past 1.5 yrs.  It has 2 ventral boxes.  At the time of placing my order, the shaper was insistent the ventral box needed to be further forward than Larry Allison's recommended 20" forward of center.  In the picture, I'm pointing at a second ventral box that was installed later on at 20".  I usually have a small ventral in this box.

Things I noticed with the ventral fin in the front box (furthest forward, 5 ft from center):
1. Tracking is slightly better. Placing the ventral so far forward seems to only have one specific benefit - tracking.
2. Very difficult to turn.
3. More energy is needed to keep the board up to speed. The fin creates front drag or push. Less forward projection.
4. The board became more  susceptible or sensitive to small wakes pushing the nose around and affecting stability. This was in a harbor. Imagine the effect in the open ocean.

The 20" formula for ventral box placement seems like the best compromise placement for improved paddle efficiency.  20" forward of center is right where the paddle enters and begins a stroke, resulting in good push off the ventral fin along with great tracking and stability.

Happy paddling, Bro's!!!
Title: Re: The ventral fin from Larry W. Allison
Post by: blackeye on July 12, 2015, 09:50:07 PM
blackeye, it's only a prototype, to test the general concept. My daggerboard is generally either down, or strapped on the deck. But I'm really convinced that cruising SUPs should have a pivoting centerboard, like old woindsurfs. The ventral fin is only a first step in this direction.
My apologies, that came off a bit more snarky than I intended. I am very interested in what you have done. I agree, a centreboard is ultimately the way to go.
Title: Re: The ventral fin from Larry W. Allison
Post by: PaddleSpot on August 12, 2015, 11:51:48 AM
 No offense taken blackeye :D
Title: Re: The ventral fin from Larry W. Allison
Post by: blackeye on August 12, 2015, 08:24:56 PM
I'm Canadian so I'm mortified if someone were to take offense to what I say.

That knife you have strapped to the deck is totally badass by the way. Are you ex Marine Commando? :)