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

[Larry Allison]

Here's some more Data from another guy Wayne Limm from South Bay who called me one day for a ProBox Twin Install. Wayne was also one of the test riders in the group that tested the M&M Boardwork Twins.

I will come back and answer some of your comments in a few my friend. Thanks for asking questions, Mahalo


Wayne Comment:

Wayne Limm In the past couple of yrs I've progressed through the Ninja, several Gladiators, & the Bat Wing on a 12'6" Surftech Competitor and the green Big Joe (14 ft) in the pic. They all improved tracking on flat water. What I really wanted to do though, is paddling in the open ocean & not worry about losing my balance & getting wet. Larry's pro box twins and ventral are rock solid stable in allowing me to go just about anywhere in the ocean. I love being able to tinker with the fin set up for different conditions.

[Henrik F]

My Fanatic Fly Race Carbon 14' Flatwater and my Surftech Bark Competitor is going to have the AVS and TWINS installed. In a month or so I will have them tested

Henrik F

[pdxmike]

  Lastly, we’re not even close to design, fins, placement, etc. This is just the beginning, just be open minded. Remember the book “Green eggs and Ham”. Well next Larry will be cooking “Green Eggs and Spam” with teriyaki sauce and he doesn’t even know it.

It's always interesting to me (and a good lesson) to see that the people who know the most about something are the first to say how much more there is to know. 

I'm excited about the experimentation and the idea that fins could become much more prominent in regard to how boards perform.  It's pretty wild to see people focused on fin shape, then out of the blue (to me) people are questioning the number of fins--esp. when the standard idea is that you'd be crazy to put more than one fin on a race board.  It does seem like there's been some growth in appreciation of fins' importance even in just the last couple years--hope that continues.  All we need now is for race rule makers to stay out of the way, so the rules don't lock in today's practices. 

[Larry Allison]

Underwater shot of Probox Twins in motion.


https://www.facebook.com/photo.php?v=10203015944466134&comment_id=7357138&offset=0&total_comments=2&notif_t=mentions_comment

[Larry Allison]

This Indigo Board in the pic is owned by Conrad Garcia from Florida. Conrad Garcia shares here his experience using ProBox Twins and Ventral combo.


Conrad Garcia comments:


Conrad Garcia Great article Larry W. Allison and Casey Gotcher. And great comment by Reid Inouye. The carbon Indigo with twin Allison fins and dual ventral in the article is my rec class 12'2" x 31" board. It is faster with just twins and ventral front. The center ventral in back actually helps with tracking in rough ocean conditions but adds drag. I do not surf, so I'm interested in going straight, fast, and staying on my board.....the twins and ventral really make up for my lack of ability and keep the barge going straight and balanced in the worse South Florida washing machine conditions.

My previous rec class board was also 12'2 x 31" 225ltr and was we'll balanced with a single fin. The new board is 255ltr and faster with the twins. My mistake on the new board is that it should have been 29" wide, and the twins with 2 ventrals or single ventral would have given me the same stability as my previous single fin board, but more speed. 31" wide board with quad fins was definitely overkill, but the set up works very well in any size board.

I guess it's time to start a new twins with ventral fin project on another 12'2" or 14' board.

[BroDog]

Hi this is Wayne.  My first post!  When I got the twin & ventral installed, I immediately noticed the board was faster than with just a single fin.  Larry attributed this to straighter tracking (i.e. less alternating paddle on each side) and better glide.  
From that point to now I've been able to paddle to places that were previously too challenging or difficult for my skill level. Really enjoying the ride

[Larry Allison]

The Pics below are from Joel Yang out of Washington on this Starboard.


Joel Yang comments on his use of ProBox Twins and Ventral:


This is my Starboard Coast Runner 14'. It is now part of our quiver as the Village of Stoke Tandem board that Coli and I use for paddling locally and at the races here. It as taken quite a bit of morphing over the last year of ownership starting with it taking flight from the roof of a car - getting brought back to life by an amazing friend - Sean Thomas from Echo Composites, who has proven to be quite the board repair guy/customboardmaker/awesomeguyonthewater in our neck of the woods, to taking on some mods with Larry W. Allison's ProBox Finsystems and Ventral fin installation. This board ever since is perhaps the most versatile board in our quiver that I use for everything from Training, Racing, Downwinding, and Tandem paddling with the Stoke-o-nut. I now have the ability to switch up how this board feels according to the type of paddling I do..(imagine being able to switch out the tires on your vehicle according to the road and weather conditions on a dime)... Imagine this: a 200lb guy that has ZERO grace and looks like a Bulldozer when paddling with medium balance and a child that has very limited athletic ability and is nowhere close to as Ninja as the both of us would like to be on a board that is 14 x 28" - - - this setup has allowed us to move forward from the 11'6x32 board that we were using in the past (which I'm extremely thankful for!) I cannot even imagine having a board without this setup from this point onwards.

[Larry Allison]

Here's pic and review on the Infinity 12/6 Cutthroat with Billy Kho:

Billy Kho says:
December 8, 2013 at 8:23 pm
Billy Kho I’ve been experimenting with the twin/ ventral combination on my Infinity 12’6. Prior to Larry setting me up with the twins and front ventral I was paddling my board with a Gladiator hybrid for stability since my board was a little tippy at 25 inches wide and a lot less volume than what I was used too. In flat water to mild wind conditions the board paddled fine, but in moderate chop and race conditions while being in the mix with all the wash from other boards it proved to be pretty tippy. The addition of the twins along with the proper size ventral provided a much more stable feel . My first feedback is that it’s not necessarily faster than a single fin set up, but it is not slower either. I can’t wait to try it on a board more suitable to my size and weight, which Steve Boehne just shaped me. I’m very optimistic with the direction Larry is going with the twinnes, we are in the initial R and D phase playing with how the fins react with different covcaves, rocker, bottom contours and fin sizes. This has been fun for me, keeping things fresh and exciting!

[55NSup]

I need some guidance on toe-in angle on Twins for a 16-5 build. And if you Think ventral is neccessary on a board that Long.

[mik911]

Larry--good to hear of all the developments in twin fins since I last talked to you down at your factory a few months ago.
What are the latest thoughts of the need for a ventral fin (in front)?  Would twins + fin box ventral fin provide adequate tracking without a ventral fin in front?  A ventral in front wouldn't work for me, as I surf the 12'6" quite a bit.

BroDog--I recognize your mug/board from the pics above.  Sup4Fun and I met you at the Adler Paddler Race earlier in the summer in Long Beach. See you around the South Bay!

[Larry Allison]

Here is a review by Allison Race Team Ambassador Chip Bock: One of the strongest supporter of Twins beside Chris Hill of North Carolina would started the Race Twin movement with me almost 2 years back after the Surf Twin movement on the Phoenix Boards 3 years back. Enjoy the Ride my friends.

Release the Twins!!
Part I of II

Ok, NOT what you were thinking…
I am talking about Twin Fins on SUP Race Boards.
Now I know many of you are saying “Aw come on, I saw people do that a couple of years ago and it didn’t work…”

Well, you are right. It didn’t.

The bigger question is WHY?  

It didn’t work because shapers and riders did what we usually do…take what we know and apply it…well…to EVERYTHING.
Twin fins didn’t work previously because traditional SURFBOARD dimensions and fins were applied to SUP race shapes.

You see the interesting thing about SUP’s is that they are...SUP’s.

Especially unique are Race SUP’s.

They are not canoes, or kayaks or outriggers or sailboats or powerboats or windsurfers.
The physics occurring when paddling a SUP of any kind, due to the weight being centered in a very small area (even compared to a Kayak or Canoe), the angle of leverage being so much higher above the boards water line and the fact that we are only going 6-7mph (and that’s at the Elite fast end in flat water) is something that many of us seem to overlook.


So back to Twin Fins; How and Why do they work now?

It's because SUP Race Twin Fins need specialized fins and a more in depth analysis of what a SUP race board is doing Under and On Top of the water (and not forgetting to factor in environmental forces like Current, Wind and Surface Chop).

Enter Larry Allison of Allison Race Fins and Fibre Glas Fin Co.

More about Larry - see video below:
- Larry Allison

I have worked with Larry quite a bit over the last couple of years on different fin designs (the Ventral Fin box and advent of the Mini-Ventral are some of my forays with Larry).
So when Larry said “Let’s put a pair of Pro-Boxes in your carbon 14ft race board” (and he explained why) I said “Let’s do it!” (Special thanks to George at www.surfguyssurf.com who does all of the fin box modifications on my race/surf boards - top shelf work)

Flash forward to a few fin size and shape alterations later and I again say Release the Twins!

So what will Twin Fins in your SUP Race board do for you?? (THE HOW)

1.      Increased stability – not just to the boards’ general shape, but also in chop, side wind, heavy seas, while paddling, etc.

2.      Increased projection - in adverse side wind and chop (at the 2013 Key West Classic this year I was able to accelerate, pass and point higher than other paddlers on the back side of the island cutting across the large bay with a 25 mph cross wind; I attribute that to the Twin Fins and Ventral Fin combo I was running – especially compared to the previous year with a single fin on the same board)

3.      Off the line top speed – From a standing start, Twin fins allow you to accelerate up to the boards top speed much quicker than a single fin.

4.      Low Drag, Low Drag, Low Drag – a pair of twin fins are only 4-5 inches deep. Depth is drag. (At this year’s Carolina Cup I was able to cut across very shallow sections of the Intracoastal; keeping me out of the very heavy on coming current we paddled in for almost 8 miles and again afforded me to catch and pass 5-6 racers or more on the back side of the course.)
For THE WHY, I need to break this up into two posts.

In my next post I will explain why Twin Fins work in more detail (The Method behind the Madness)
NOTE: Do not run out and throw a set of surf fin boxes in your race boards and snap in a set of 4 inch surf fins - remember this didn’t work the first time around.

[Larry Allison]

Release the Twins - Part II

So now for the “Why” twins work so well in SUP Racing compared to traditional single fin set up’s…

Single fins Vs. Twin fins in SUP Race boards when trying to go straight and fast:

1.      Projection

a.      Because Single Fins are in a center fixed position in the tail; fin outline shape, flex, cord length and depth can all dramatically effect projection – projection effects speed in both flat water and catching bumps down wind

b.      Twin Fins are able to “push off” from two separate parallel planes, allowing for one fin to compensate for lateral forces (side chop, turbulence from other paddlers, etc.) and provide more consistent projection (with far less drag due to reduced depth)



2.      Drag

a.      Single fins tend to be longer (or deeper) because with only a single plane to work off of; single fins need to do the multiple tasks of projection, yaw (tracking) and lateral stability – this does not allow for the fins to go much shallower than 6-7” (and be affective)

b.      A pair of Twin Fins can accommodate the same surface area as a larger single fin with much less depth; as little as 4” – my current favorite for most race conditions are 4” deep with a 10” base in an “Elliptical” shape – Depth equals drag, so if you can run shallower fins, you have less drag.



3.      Stability

a.      Single Fins again have a single plane to counteract lateral forces like side chop and sub-surface turbulence (from boats, and other paddlers), rebound from shore lines, jettys, docks etc. The plane also being at the tail, makes it even harder for this single point to stabilize efficiently (similar concept as to what is more stable in rough water; a dual hull/keel vessel or a single hull/keel vessel)

b.      Twin Fins again have the advantage of dual planes; this allows for greater lateral resistance (as water pushes and pulls from both sides, allowing one fin to compensate for the other and visa versa) – increased lateral resistance equals greater stability – in order for a Single Fin to increase lateral resistance, it has to be made longer – BUT if you make it longer (deeper) what happens? – Increased Depth equals Increased Drag

4.      Tracking (Yaw)

a.      Single Fin SUP race boards suffer from excessive Yaw – early Single Fin SUP surf boards had tremendous Yaw for example; this is one of the reason’s displacement shapes for race Sup’s came into use; to compensate for the Yaw created by paddling a single blade paddle on one side and then the other – if you create displacement in the nose, the hull aids in compensating for the Yaw and allows the board to go straighter (more strokes per side) and helps the boards “track” and “point” in side chop and windy conditions


b.      Twin Fin race boards do not need as much nose displacement – the two planes of the Twin Fins work off of each other, creating better tracking and pointing. When added to a Ventral fin (a single fin located 20” forward of center balance point) – the three fins work in concert, allowing the paddler to point a board (displacement hull or not) wherever they want to go (regardless of side wind and surface chop). How to use this efficiently requires an understanding of the various environmental forces that a SUP race board can encounter in what I like to call “Mixed Media Races” – race courses that traverse both open ocean, intra-coastal waterways, tidal currents, cross/head/tail winds, etc. ALL in a single race. Twin Fins together with a Ventral fin, exchange “jobs” when set up properly throughout a single race; producing more efficient hydro dynamics for the paddler.



5.      Venturi Effect (added bonus)

a.      If you view a Single Fin underwater when paddling a Race Sup board, you will see turbulence (as bubbles and wash) coming off the fin as it alternates pressures being placed on it from side to side with each stroke of the paddle blade.

b.      If you view a Twin Fin set up underwater when paddling, you will see zero turbulence. The water is releasing cleanly and with greater efficiency than the Single Fin. An added bonus I discovered with the Twin Fin set up is a “Venturi Effect” that is generated by the parallel fins. The Twin fins from Larry Allison combined with Pro Box Fin Systems are placed in reverse to how they are positioned on a Twin Fin Surf Board – the “Flat” side of the fin is on the outside of the fin towards each rail – the convex sides are on the inside facing each other – this channels the water between the fins and creates a “Venturi Jet Effect” off the tail.


In summary, Twin Fins in Race SUP boards:

·        Reduce drag (shallower Fins)

·        Increase stability (increased lateral resistance while maintaining reduced drag)

·        Increased projection

·        Enhanced tracking (without increased hull displacement required, allowing for more “planning shapes” in Race SUP boards)

·        Venturi Effect (channeling water, increasing speed – especially time from standing start to top speed is reduced)

If in Florida or Southeast – contact George at www.surfguyssurf.com to get your Sup Race board retrofitted to Twin Fins and feel the difference!

**NOTE: Not all Sup Race Boards have flat bottoms – Twin Fins need to be set at Zero Degrees (meaning vertical to the bottom) – Pro Box Fins Systems by Larry Allison are the only retro-fit fin boxes that allow for different “Cant” inserts – this allows for Zero Degree alignment regardless of the contours of your Race Sup bottom – we tested various Cants with Twin Fins for this application and Zero Degree positioning of the Fins is CRUCIAL. – I have a Morelli and Melvin 14’ Race Sup being retrofitted now and will post more detail on “Cant”; using this board shape to illustrate. 

So let’s see those Twins and see YOU in the water – Aloha!

The Pic below:

(Blue/Green Board to far right) - Twin Fin Standing Start example - within first few yards the board is at top speed (notice the small "jet" effect off tail - that's the Venturi Effect)

[bretrwarner]

For what its worth I have twin fins on the Kaholo that I built earlier this year, and I have been very happy with them. After reading all these posts though I feel like I may want to add the ventral fin I kept seeing on the pictures. Where should I place that thing on a 14 ft board, and what are the typical dimensions on it?

[Larry Allison]

For what its worth I have twin fins on the Kaholo that I built earlier this year, and I have been very happy with them. After reading all these posts though I feel like I may want to add the ventral fin I kept seeing on the pictures. Where should I place that thing on a 14 ft board, and what are the typical dimensions on it?

Alright bretrwarner, nice to see you jump in my friend. Posts some pics of your board! On any board the formula for the Ventral is 20" forward of the balance point of the board to the back of the 10" fin box(Hi Surf Box Produced by Larry Allison). Not to get the balance point confused with the middle of the board, because the middle of the board is not the balance point most of the time.

Ventral fins come in 3 sizes, 2 1/2" by 8 1/2" is the small. 2 3/4" by 11" is the Medium. 3" by 12" is the large Ventral. Ventral fins are all Screwless (Click In) for ease of changing to the conditions or stacking on top of your car when loading boards. 

[bretrwarner]

Here are some pics of my boards fins. It was my first time ever glassing anything, hence the bumps. Fun board though, and faster than I thought it would be.