Standup Zone Forum

General Category => The Shape Shack => Topic started by: Henrik F on January 11, 2013, 02:48:20 PM

Title: What tail?
Post by: Henrik F on January 11, 2013, 02:48:20 PM
Hello!
I am going to build a board for flatwater and whitecap waves. I haven't yet decided if it is going to be 12'6" or 14' but I need som thoughts of the boards tail. Can anyone please explain the pros and cons of a pintail or a "squaretail" in those conditions? Please help me out. I don't want to start off the wrong way.

Thanks

Henrik F
Title: Re: What tail?
Post by: DavidJohn on January 11, 2013, 03:18:55 PM
Put a square tail on it and it's almost like having a 15' board that's only 14' long.. or a 14' board that's only 12'6" long.

IMO its really that simple.. Paddle a board without looking back and you could not tell what shape tail it is.. Pin, round, diamond or swallow tail.. It's not like a suring board so you might as well keep it simple and just go with what almost everyone else does now.. a square tail.

DJ
Title: Re: What tail?
Post by: DurhamSUP on January 11, 2013, 04:28:47 PM
Yup, I would go with square as well. The benefits of the stability out way the reduced drag of the pin tail. I have found that the pin does release the water cleaner with less turbulence, so if you were only ever paddling in pure glassy conditions, the pin would be better.  ...and stability wouldn't be an issue.
In normal conditions, the square tail is the way to go.
I do remember seeing a video of Joe Bark talking about a pin tail dominator that he no longer (or rarely) makes any more. I think the rationale was that everyone preferred the square.

Just be sure to make the edges at the tail as sharp as possible for clean release.
Title: Re: What tail?
Post by: Henrik F on January 11, 2013, 10:29:08 PM
Ok thanks. Squaretail it will be then  :)

Henrik F
Title: Re: What tail?
Post by: Jethrow on January 12, 2013, 02:51:34 PM
As a follow up question, does a square or diamond tail increase stability over a pin tail?

Here's why...
I built a 16' pin tail flat water board and I am having stability issues. I haven't fallen off in normal flat water conditions but I do this running on the spot thing (alternating weight rail to rail quite fast) every now and then to try and stay on and this can't be fast. Any sort of side wave from a power boat or such would definitely see me in the water.

If I cut the board down to 14' with a square or diamond tail will this increase or decrease the stability? I'm just shy of 100Kg's and the board is 70cm wide with a rounded bottom shape (probably too much round).

I've spent the weekend cutting foot wells into the deck to get my center of buoyancy lower but haven't tried out the results yet.

Thanks
Jethrow
Title: Re: What tail?
Post by: DavidJohn on January 12, 2013, 03:49:49 PM
As a follow up question, does a square or diamond tail increase stability over a pin tail?

Here's why...
I built a 16' pin tail flat water board and I am having stability issues.

If I cut the board down to 14' with a square or diamond tail will this increase or decrease the stability?


No change IMO... Maybe even slightly worse.

DJ
Title: Re: What tail?
Post by: Jethrow on January 12, 2013, 04:03:13 PM
Yeah DJ, that's what I thought deep down :'(
Title: Re: What tail?
Post by: pdxmike on January 12, 2013, 04:20:58 PM
Think of it this way--if you started with a 14' board with a square tail--which is what you have "buried" within your 16' board, then added 2' at the back in any shape--pintail or whatever--could it possibly make the board less stable?  It seems like at worst, it would have no effect on stability.  So going the other way, starting at 16 and cutting down, you'd either break even or get worse like DJ said. 
Title: Re: What tail?
Post by: Jethrow on January 12, 2013, 11:52:05 PM
I was thinking more along the lines of the sharp corners of the square tail pushing through the water and making an impact rather than the board pivoting on the pin tail but I'm clutching at straws. Hopefully the foot wells make a difference. I guess if it doesn't work then at least I have an excuse for doing another board.  :D
Title: Re: What tail?
Post by: DurhamSUP on January 13, 2013, 05:01:56 AM
Like pdxmike said, the area of the square tail is still in your 2' of pin tail. That area is already helping float the board, plus the added float from the pin tail area. Since the surface area of the pin is close to the centerline of board it adds very little stability, but it can't reduce stability. At least at the speed that a board is paddled. I'm not sure what happens at really high speed.
 It would suck to do all that work to the board and not change the stability and possibly slow it down just a bit.
If you want to cut into the board, you could add some foam and make a 16' square tail.
I like the idea of new board build.     ;D
...keep us posted.
Title: Re: What tail?
Post by: SUPpaddler on January 13, 2013, 12:58:36 PM
On a flatwater board, what does "clean release" mean, and why would sharp rail edges be more efficient?  I thought those concepts were for planing conditions.  Since the rails stay submerged in flatwater, wouldn't rounded sufaces do better since they have less surface area to create drag?
Title: Re: What tail?
Post by: DurhamSUP on January 13, 2013, 02:34:33 PM
If the rails are round at the tail, the water will want to follow the curve of the rail and create more drag and turbulence. With a hard rail the water will leave the tail and not be able to follow the radius of the sharp edge.
The rear edge of tail can even go farther and have a chisel shape to the rail to be sure there almost no chance of the water following that angle.
Normally with a flat water board the tail will be just at the surface of the water, so the edge will not be submerged.
Title: Re: What tail?
Post by: DavidJohn on January 13, 2013, 10:36:57 PM
IMO the rails don't need to be super sharp but the edge along the back of the board does.

DJ
Title: Re: What tail?
Post by: SUPpaddler on January 14, 2013, 02:57:58 AM
Glad this topic came up since I was finalizing a flatwater design and wondering about the tail.  I was going to curve up the last inch of the tail so that in case I had miscalculated the waterline height, it would still curve up to meet the water surface.  But based on what you guys are saying, perhaps it should have a clean edge, and maybe the last few inches of the side rails should also be sharp.  That seems to be the conventional wisdom.
Title: Re: What tail?
Post by: Henrik F on January 14, 2013, 06:47:02 AM
What happens if we take the side rails sharp even further forward?

Henrik F
Title: Re: What tail?
Post by: Dwight (DW) on January 14, 2013, 06:55:18 AM
What happens if we take the side rails sharp even further forward?

Henrik F
The board gets clumsy. More fun when softened.
Title: Re: What tail?
Post by: Henrik F on January 14, 2013, 07:00:12 AM
What happens if we take the side rails sharp even further forward?

Henrik F
The board gets clumsy. More fun when softened.

Ok!

Title: Re: What tail?
Post by: TWsup on January 15, 2013, 02:42:31 PM
IMO the rails don't need to be super sharp but the edge along the back of the board does.

DJ

check. this is what I believe is correct in regards to efficiency.
Title: Re: What tail?
Post by: TWsup on January 15, 2013, 02:52:59 PM
Henrik,

take a close look at photos of the new Fanatic Falcons. they have rounded rails all the way back and only a sharp release at the rear edge on the tail. supports DJs statement.
this is how a displacement hull is designed.
adding tighter/edge rails to last meter of so ( like Bark competitor et al ) allows board to plane on waves easier, and I suspect easier to tail turn. The larger surface area as a result of harder rails planes easier.

I'm sure there are multiple interdependent design factors like rocker, bottom shape in cross section width and outline ( plan form) that effect this too.

in theory, absolutely best displacement shape is near cylindrical  cross section with pointy ends. but you can't stand on it...
Title: Re: What tail?
Post by: Henrik F on January 16, 2013, 01:51:01 PM
Henrik,

take a close look at photos of the new Fanatic Falcons. they have rounded rails all the way back and only a sharp release at the rear edge on the tail. supports DJs statement.
this is how a displacement hull is designed.
adding tighter/edge rails to last meter of so ( like Bark competitor et al ) allows board to plane on waves easier, and I suspect easier to tail turn. The larger surface area as a result of harder rails planes easier.

I'm sure there are multiple interdependent design factors like rocker, bottom shape in cross section width and outline ( plan form) that effect this too.

in theory, absolutely best displacement shape is near cylindrical  cross section with pointy ends. but you can't stand on it...

Hello. Cannot find any photos and the rails but I see what you mean. Like an old Div II windsurfingboard. Sort of. But I don't understand why their new 14' is almost a pintail?

Henrik F
Title: Re: What tail?
Post by: DavidJohn on January 16, 2013, 02:52:19 PM
Check out my pictures of the tail of last years Fanatic.. Here.. http://www.standupzone.com/forum/index.php?topic=10610.0 (http://www.standupzone.com/forum/index.php?topic=10610.0)

Compared with my latest pictures of the tail of this years Fanatics.. Here.. http://www.standupzone.com/forum/index.php?action=profile;u=229;sa=showPosts;start=210 (http://www.standupzone.com/forum/index.php?action=profile;u=229;sa=showPosts;start=210)

See how very different they are..

I'm guessing that because the board gets tipped from side to side often when paddling if you have sharp rails in the tail area you get a lot of resistance resulting in drag and slowing you down.

With the very soft rails (not just soft but actually rounded) the board can be tipped from side to side without disturbing the water so much (even though it might be more tippier) there should be less drag.

Maybe there's more to it.

DJ
Title: Re: What tail?
Post by: DurhamSUP on January 17, 2013, 06:21:43 AM
This is interesting.Looks like there is a lot of belly in the board too.
I always did hard rails on the last 12-18" of the board, depending on the outline. I'll give the round rails a try on my next flat water board. I sure do hate glassing hard rails anyway.
Title: Re: What tail?
Post by: Henrik F on January 17, 2013, 12:54:09 PM
Hmm. I have to sit down and talk all these things through with the shaper I am going to work with  ???

Thanks!

Henrik F
Title: Re: What tail?
Post by: TWsup on January 20, 2013, 12:27:21 PM
at this point, I'm pretty convinced DJ is right. My boat design study from 30 years ago is coming back...
board will be less stable but heel angle changes don't effect efficiency as much.

those hard rails will be best when planing on DW rides.

when I start on my 16 footer it will have these kinda rails.

back to having square tail. having square tail will add buoyancy to tail allowing it to raise when swells overtake you from the rear. a pin tail will be better in total flat, but may make board yaw and broach in following seas.

wish I had my sketch books from 1982. I remember clearly drawing ideas for displacement windsurf boards that looked like these Fanatics. never built one tho- didn't have the facilities.
Title: Re: What tail?
Post by: supuk on January 20, 2013, 12:45:57 PM
the problem is theres a line between a board being very efficient but tippy and being able to efficiently paddle a board. i paddled the  falcon at the bop which has the rounded rails and found it a right handful in chop having to take nearly every other stroke to catch myself were as the 2012 board was stable as a rock in any condition far worse than that of the bop. The thing is finding a compromise between everything for the conditions you intend to use a board in.
Title: Re: What tail?
Post by: Henrik F on January 20, 2013, 01:12:24 PM
the problem is theres a line between a board being very efficient but tippy and being able to efficiently paddle a board. i paddled the  falcon at the bop which has the rounded rails and found it a right handful in chop having to take nearly every other stroke to catch myself were as the 2012 board was stable as a rock in any condition far worse than that of the bop. The thing is finding a compromise between everything for the conditions you intend to use a board in.

"The thing is finding a compromise between everything for the conditions you intend to use a board in." It is just that...  :-\

Henrik F