Well it looks like I will be off the water for another month or so 
and being inspired by lookielookie and shep I throught I might start building a 14'6" downwinder.
Plan at this stage is to build it in either hollow timber or vac bag timber venneer over foam. I have a soft spot for woodies, or maybe that is a hardspot for woodies
So as I havent even seen a 14 footer I was hoping some of you might be able to help with suggestions on rocker, width, widepoint position, planing nose or displacement. Rail shape, Tail design etc.
Board will be used in WA waters downwinders mainly and some flatwater with 110kgs hopefully standing on it
So I am thinking 14'6" long 29" wide 5" thick with wide point fwd centre by 6", 10" nose 15" to 16" tail and keeping 3. Dont know anything about rocker so what about keeping it flatish in the middle and ~7-8" in nose and 3.5" tail for a planing shape and less if displacment.
Approx estimates on weighst are 16kgs for the Hollow and about 11kgs for the timber veneer. I put something together on aps3600 and post up here for comments.
Thanks
For a start, make it 14'0". That way you can qualify for any races with a 14' division.
Just copy a 14' Glide and make it slightly wider and give it a rounded pintail like the 17' Glide... easy..
DJ
Here's the loose dimensions to a Naish 14, as a reference point.
Dimensions are measured rail to rail (gives you the rail lines on the water), not overall width.
Additional comments describe the rail.
0 is 0 feet at the nose, and 14 is 14 feet at the tail, followed by width (mm).
Board is pretty much bang on 14 foot along the rocker line.
0 - 0
1 - 180 - rails are pretty much round
2 - 340
3 - 450
4 - 540
5 - 600 - rails start to soften, with up to 1 inch of rail tuck
6 - 640
7 - 660
8 - 660
9 - 640/645
10 - 605 - still virtually no rail tuck
11 - 550
12 - 475
13 - 350 - no rail tuck / vertical rails, at the rail
14 - 230 wide square tail
Very slight V in the tail, and rolled V up near the nose, but more or less dead flat bottom through the middle.
So overall wide point is pretty central, but rail wide point is perhaps just backwards of central.
You've probably seen the board, or can access posts with good photos. ??
(I'll edit later for rocker)
Red thumbs may follow.... people don't like Naish, or me, or passing on info, etc.... But Shunter, I'm sure you want a starting point or a reference point, so you can create your own individual board !!
Good luck !
and being inspired by lookielookie and shep I throught I might start building a 14'6" downwinder. 
www.clcboats.com/modules/catalog/boat.php?category_qn=surf_boats&subcat_qn=paddleboards&code=kaholo-stand-up-paddleboard
Check this out
Depending on how much roll is in the bottom of the board (displacement vs planning) you could probably lose an inch off the width. I ride a 14' displacement style DC which is 28" wide and while it's a bit unstable in cross chop it's nothing that a bit of time on the board won't fix. Narrower boards should be quicker - if you can stay on them!
I'm 110kg and 6'5"
Hey Shunter
This is one I was thinking about a while back - still not sure on the best way to build.
14X28.5x4.5 Strong V through the nose, transitioning to pretty flat V through the mid section and a bit more through the tail.
can email you the design if you want to play with it
seriously
awesome work simondo... I put that into aku shaper and see what she comes out like against my 1st pass.
Heres my first pass on outline and rocker still need to clean up the curves and nose rail profile but close to what I think I will build. I would like input in to rocker if anyones got suggestions. Probably go with planning shape nose/bottom as its easier to build with timber. Thanks for the input so far
Make sure the way in which the rocker "curves" matches a windsurfer.
I've shaped 6 downwind boards.
With my first shape, I copied an F2 windsurfer. It would fly, hitting very fast planing speeds.
Later, I tried another board using the AKU default surfboard style "curve" to my rocker, while keeping the same total rocker lift I had with that first board copied from the F2 windsurfer. This board could not reach the same high speeds of the one copied from the windsurfer.
Many shapes later I was able to get my hands on a Naish Glide and set it on my rocker table and compare to my F2 windsurf derived rocker. My original rocker was a near perfect match to the Glide. Only 1.5mm different in one spot.
I'd also recommend a wide tail. It makes a huge difference in stability.
Translation, flat rocker in the middle with increasing curve toward the tail is a SLOW rocker for a planing board.
The second dimension is the overall width (mm), and the first dimension is the width at the bottom / waterline.
Couldn't find my good tape measure with feet and inches !
0 - 0
1 - 180 - 255 - rails are pretty much round
2 - 340 - 410
3 - 450 - 520
4 - 540 - 590
5 - 600 - 645 - rails start to soften, with up to 1 inch of rail tuck
6 - 640 - 675/680
7 - 660 - 695
8 - 660 - 685
9 - 640/645 - 660
10 - 605 - 615 - still virtually no rail tuck
11 - 550 - 555
12 - 475 - less than 480
13 - 350 - 350 - no rail tuck / vertical rails, at the rail
14 - 230 - 230 - wide square tail
And yes, you probably want at least 5 inches thick in the middle, maybe 5"1/2. Naish 14 is 5"3/4 plus a 1/4 of deck grip, and is at least 4 inches thick down at the tail too, giving good volume to get the bum of the board lifted on the runners.
I'll rip the fin out, and try and measure the rocker later. But the Naish 14 is very straight out the back. Not much final tail rocker.
I need this device, which actually measures rocker ! But it's in Hanalei Bay, Kauai.
I put that into aku shaper and see what she comes out like against my 1st pass.
Rocker;
0 - about 275mm, and 235mm of lift 100mm in from nose (275 is about 10"3/4, and 235 is about 9"1/4)
1 - 172 (about 6"3/4)
2 - 110
3 - 65
4 - 32/33
5 - 13
6 - 3
7 - 0
8 - 0
9 - 1
10 - 7
11 - 16
12 - 30
13 - 43
14 - 58 (about 2"1/4)
Edit, with pics now;
I agree with Canuk. You could probably lose an inch or two of width. These longer boards have more rail in the water so it helps with stability even though they're narrower.
I'd be sharpening up the rails too, especially in the back third.
The C4 Vortice has more rail tuck than the Naish, and Phill and I were discussing it on Sunday. From memory the Vortice is about 26"1/2 wide, but it has 1"1/2 rail tuck on each side, so the rail width on the water line is about 23"1/2. But the Naish 14 Rail Width on the waterline is about 26" and overall is 27"1/4.
The Naish 14 is more stable, and wider. But the Vortice is probably ever so slightly quicker.
thanks everyone awesome response and input. Thanks simondo for getting the rocker measurements.
I am 6'2" and 110-115kgs so went for slightly wider and thicker than normal
Hey simondo when you say width at water line i assume you mean width where the bottom starts to roll up?
cheers
