Slippery bottom shape for 14'

[PaddleSpot]

- Deep fins are slowest, so I'd follow Larry Allison's development path and go short multi-fin. Larry is doing a mid ship fin. It might be what a flat bottom needs to fly straight.

My feeling is that off the shelf fins are awfully thick, 10 to 12 mm (1/2 inch) , heavy and expensive. I build my own fins using 4mm plywood+one layer of carbon fiber,  thickness around 5mm (0.13⁄64in), super light, minimum drag.

[SUPflorida]

Thank you all so much...while experiences seem to cover the spectrum from one end to the other, there are good bits to gleam.

I've also been digging into a lot of video and interviews with board designers. I like Mark R. a lot (SIC). He seems like "what you see is what you get" kinda guy. He shares a lot of good info in his interviews....his approach...what he finds is most critical ...and something I really find valuable...what sounds really good, but doesn't prove out on the water. And while he is world renown as the King of Down Wind ...he's no "one trick pony"

You guy are really helping me focus in. I have come to several conclusions since starting this post.
1) I really like a lot of things about my current board and I have to agree with DW on the round bottom. I have yet to get wet on my 26"'wide 14' but I'm pretty confident I would not be able to say that if I rounded the chines to what Paddlespot has. My water very seldom looks as flat and wind free as his pictures.

2)DW I also like my wide tail for stability but now I'm thinking that is the reason for the need for more tail rocker in the last 18". I am seeing two approaches one is straighter centerline rocker with narrow (pintailish) tail or a realitively exaggerated tail rocker with wide tail. Both achieve a level of clean water release but by different methods.
Peter
My current boards tail sits approx 1-1/2" clear of the water at rest with no rider. Maybe 3" nose rocker (no rider). 
As I move forward to achieve better tail release, I start moving away from the wide point and the board gives up that rock solid stability it has when standing 10"-12" further back. I believe the overall rocker is almost dead on but needs to be re-distributed. Hence The reason I should lower the nose rocker equal to what I raise the tail rocker.
This would effect multiple things:
A) Lower the nose to bring the wave piecing effect sooner. The current nose cuts super clean with no rail wrap.
B) Give Cleaner tail release.
C) Allowing me to stand farther back on the board for better alignment with the wide point to enhance stability.
D) Which could allow me to drop another inch or two of overall width.

So now the question is to go to a double concave for tracking or not? Nothing crazy...say 1/4" per panel. Extremes always seem to work against you. Water likes gentle changes she moving at slow speeds. One thing I will do is start the concave all the way at the nose...the transition from flat to concave although a staple in surfboard design...doesn't seem to work all that great in flat water at least when one has to move forward to release the tail and use the full waterline length.
My hypothesis is this & the need to raise tail is where my resistance is originating.

My conclusion so far:
Refine & build on what I have now rather than heading in an entirely new direction and starting over from square one.
Redistribute current rocker, drop nose, raise tail.

DW
While I acknowledge the mid-ship fin is one answer to enhanced tracking... I still have doubts if it's the best solution when approaching a new build. I totally get it when trying to "fix" an issue with an existing board, but I would rather change a bottom contour and achieve the same thing if possible. But as you said that could be a simpler solution in the long run...save a lot of work trying to get all the concaves to blend right without causing wierd unpredictable turbulence. Have to give that more thought....

For those with double concave Naish Javelins...does the double concave have a noticeable effect on tracking? Or not?

[yugi]

...
- Deep fins are slowest
...

You mean it is more about depth than surface area?
Any idea why this is?

[DavidJohn]

Water density .. re deep fins being slower..

and re the Naish Jav's double concaves effecting tracking.. IMO it should but how would you know?.. There's so many things in a board shape that effect tracking.. They are also there for other reasons than just tracking..

[SUPflorida]

DJ said..."and re the Naish Jav's double concaves effecting tracking.. IMO it should but how would you know?.. There's so many things in a board shape that effect tracking.. They are also there for other reasons than just tracking."

I agree, but would you care to expand on that thought? My overall outline (granted just one small part of the equation) is very similar to a 26" x 14' Javelin.

As one who has owned or ridden pretty much every Naish race board in the last 5 years (?) I would be very interested to hear your impressions of the evolution of the various bottom/rail/rocker designs over the years compared to its current offerings.

When you think about it...many of the bottom designs under discussion have been tried on race boards by Naish. It seems to be a slow but constant move away from the more traditional rounded hull designs...at the same time user comments are made of steadily increasing stability with each itineration. all the while the boards overall width gets narrower, tails wider, rocker lowered, rails harder.

[DavidJohn]

DJ said..."and re the Naish Jav's double concaves effecting tracking.. IMO it should but how would you know?.. There's so many things in a board shape that effect tracking.. They are also there for other reasons than just tracking."

I agree, but would you care to expand on that thought? My overall outline (granted just one small part of the equation) is very similar to a 26" x 14' Javelin.

As one who has owned or ridden pretty much every Naish race board in the last 5 years (?) I would be very interested to hear your impressions of the evolution of the various bottom/rail/rocker designs over the years compared to its current offerings.

When you think about it...many of the bottom designs under discussion have been tried on race boards by Naish. It seems to be a slow but constant move away from the more traditional rounded hull designs...at the same time user comments are made of steadily increasing stability with each itineration. all the while the boards overall width gets narrower, tails wider, rocker lowered, rails harder.

IMO as far as Naish DW boards go I think the rails have actually got a bit softer.. and the noses have got a bit wider.. and the rocker is where the biggest changes are.. I much prefer concaves in the bottom rather than flat.. You can feel the air  they trap unsticking the board from the water.. I'm thinking the wider noses has more to do with the added stability in the newer boards.. But the is key.. You want the most suttle entry curve/rocker.. Both to stop pushing water and allow use of the total waterline.. and I'm thinking they have brought the start of the tail rocker slightly forward to allow you to get back to lift the nose when needed without needing to get too far back and bog the board down.. I'd like to see a bigger and deeper rail that goes further back like what the Allstars have.. I like the Maliko nose but I'm thinking something between the Maliko and normal Jav might be best because it's the volume that brings a nose back up after pearling rather than just the nose rocker.. I think if you're going with an Ace like nose you need a narrow tail like what Fanatic are doing.. Because when the nose goes up the tail needs to go down.. Personally I'd rather pierce than boof but boofing might end up being the way to go.. It's still early days in these boards.. Particularly DW boards.. I'm looking forward to see what Naish comes up with next.

[SUPflorida]

DJ
Thank you for posting all those pictures. I have watched many of your video reviews before on these boards but the stills give a much better perspective than the go pro.

What jump out at me is:
1) Rails are softer with more tuck than I originally thought.
2) There is not a crisp well defined centerline on the double concave the complete length of the board. Fairly crisp at nose but rounded considerably as you moved back...no close up tail shot...does it keep the subtle rounding? go back to a chrisper V? Or run out flat?
3) The concave under (what looks like) the standing area, while still technically a double concave....has the centerline deeper than the rail line forming essentially a single concave effect.

One of my windsurf slalom board designs has a double concave where the centerline was even with the rail line...it would accelerate and go up wind like nothing else...the down side was a decent top speed but it would only go so fast and hit a wall. That of course is not an issue for SUP as an SUP would never get to that speed in the first place. Might be a good application for lower speed craft.

I totally agree with your rocker comments, notice several of the latest and greatest with the rocker break positioned right behind the main standing area. Allows easy access to raising the nose without having to move as far back to execute. That's something I learned about building waveski's, with those you are planted in one place. Waveski's Rocker break is hypercritical as you can only shift weight by moving your upper body.

[Pierre]

Reading again initial post, I suggest another solutionof bottom shape with semi_rounded bottom and slight concave inside rail edge, and quite rounded rails, more rounded bottom section near to nose. i suggest abt 2 " nose rocker and progressive 2" tail rocker for a piering nose, this nose rocker to be increased to 3" in case of wide nose.(for more choppy condition, non piercing nose) Idea is to allow more lift under the rails, keeping advantage of a rounded bittom for clean water entry at nose. water exit to be slight V section.

[SUPflorida]

Pierre
Good stuff...Your description seems to line up with the Naish Maliko which seems to be doing very well. That's quite a step away from where I am right now which would be closer to a slightly less extreme nose profiled Javelin.
Can't imagine giving up the clean entry I have now for the broad nose Maliko or the boof style nose.

The more I picture the nose of my current board cutting through the water, the less I want to touch that part of the board...other than lowering the rocker in the front 18". Funny if I had kept with my original rocker hot wire template I would be right where I needed to be...or at least closer...but at the last minute I cut in about an 1" more rocker in the front 18". Even with the added 1" of rocker my rocker entry is very subtle.
My rails are just short of knife hard (1/8-3/16 radius) and there is zero turbulence, no bubbles, no splashing at all going on ...none of the sprinkler effect I see in videos of other boards...zero rail wrap...this part of the board is near perfect going through the water. Especially when the bottom tip of the nose is even with the water line. If I can get the rest of the board to that level of performance I would be a very happy camper.

As DJ was saying about the concaves trapping air...that's what I have experienced with them before on surfboards/sailboards/waveski's. Using rounded rails and bottom features to accomplish this seems a little counter intuitive to me, want the air to remain trapped under the board and exit the tail...hopefully supplying at least a minuscule amount of lift. I have always gone with much harder rails on all my surf/water craft than has been the norm...it just always worked better for me personally.

Something in my single concave bottom is just not tweaked right. There is some funky turbulence going on. I say that because when you look at how effortlessly the nose of the board parts/skims on the water you would think the whole board should feel as resistance free as an "air hockey puck". Also when going down breeze every so often the suction breaks loose and the board takes off so fast it wants to throw you right off the back. Don't get me wrong my current board is no dog but it is screaming to me that there is a lot of untapped potential very close to be captured.

As I said before, maybe the concave needs to start farther forward to inject more air under the board sooner? Maybe instead of transitioning to flat V panels in the tail it should maintain at least a subtle double concave all the way through the tail? Thoughts on how to alivate suction on concave bottoms? Already planning the obvious....more tail kick..I'm all ears on what you have experienced.

If the weather cooperates this weekend (not too likely as it is suppose to blow like stink) I want to find some really flat water and use my phone to video how the boards moves through the water at various standing positions. See how much of shift in rocker ( take away from nose/add to tail) I really need without swinging the pendulum too far in the other direction.

This discussion is really helping...in addition to all your great insights, there are  many things I experimented with years ago and have forgotten....you guys are reawakening them as well....I appreciate it all!!!!

[TN_SUP]

There is a really good explanation of the bottom shape of the 2016 AllStar in this video, they reveal the "secret sauce" of the board.
https://www.supboardermag.com/2016/01/18/sup-review-2016-starboard-all-star-all-round-race-sup/

[SUPflorida]

TN_SUP
Thanks for posting that 2016 SB Allstar Review.
That's certainly a unique amalgamation of approaches to achieve their goal. Beautiful board and appears to check all the boxes the designer was going for.

Interesting points on their application of concaves. Trying to think of a way to apply the design attributes of the Allstar highlighted in the video to my issues..

[Chilly]

That sprinkler effect at the nose of the board is not necessarily a bad thing. IMO at cursing speed it's good to have a piercing nose cutting through the water, but when you want to hammer it to reach maximum speed you want a nose that is designed to lift and break over what I think is the bow wake the board is creating. I may me wrong but that is what I feel is happening when the sprinklers turn on as my speed increases. My board has a piercing nose transitioning to a rounded bottom, to a double concave (2014 Allstar). Just want to add that you have to have good technique and be fit to take advantage of that design. Something I'm working on.

[SUPflorida]

Chilly
I get where your coming from ...correct me if I'm wrong....but here is my logic... that sprinkler effect is pushing water and wrapping it up the rails...that water doesn't move by itself...some of your paddling effort is being used to move that water. Whatever energy expended generating the sprinkler effect is not moving you forward. Any wasted effort, regardless of its source is keeping you from attaining your personal best speed for a given amount of effort.
That is one reason why I'm "married" to the idea of keeping my existing nose design.

It too can easily lift free is you have the strength/skill/endurance to push it hard enough. A quick video check of Kie sprinting on a 2015-16 Javelin will demonstrate how well a piercing nose can "plane up" if you have the horsepower and enough gas in the tank.
There are multiple approaches to accomplish the same thing, so whatever flavor that gives you the best experience is the one right for you. Thank you for your comments.

[Chilly]

I agree with your logic and I'm hesitant to comment on this subject because I know nothing about hydrodynamic. I'm just going by feel. My logic is that yes you're pushing water, but at the same time the board is lifting up off the water which causes less resistance. It's a tradeoff. If your nose design can easily lift than I wouldn't touch it. Personally I don't like pure displacement boards unless maybe on an unlimited because you have the advantage of board length (Hull Speed) and I would think it will take a massive effort to get it to semi plane.

[Dwight (DW)]

I just picked up the latest 2016 Antoine Albeau race board (windsurfer). He's won the world title the last 4 years on these boards.

Apparently flat bottoms still dominate racing in 2016, for windsurfers.