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So during the cold winter weeks we've been having I've had a bit of a fiddle with drawing a new Div II hull. My current method of building techniques is tortured ply construction so I've tried to design the board with this in mind. Tortured ply design isn't straight forward and there's a bit of uncertainty as to what you will end up with but that's part of the fun of it! Anyway, here's what I have so far...
I had a post up in the standup paddle section of a paddle board I built using this method but I can't find it now.
Edit:- Here it is!
www.seabreeze.com.au/forums/Stand-Up-Paddle/Review/The-How-I-built-the-Jethrow-480-thread/#1066715
Sweet Jethrow! I see an interesting and inspiring build coming!
No commentary on your lines above but some design thoughts regarding my experiences with the DB2 and the a390:
- For Pittwater chop and stronger winds the extra rocker in the a390 is a great improvement over the flatter DB2. You would think that this might compromise the light wind performance of the a390 but I don't find this to be the case. Actually the greater rocker allows the transom to ride higher in the very light winds where the DB2 would always be dragging a bit of turbulent water behind.
- The a390 has a heap of volume just ahead of the mast and it tapers in width and buoyancy from there aft. I think it is this which gives a slightly bow up trim as the board rails. By contrast the DB2 would go slightly bow down when on the rail, this would shift the CLR forward and require the rig to be brought more upright, further exacerbating the issue. I dealt with this by progressively raking the centreboard back as the wind came up, not so much for control as to get the bow up. No such issue on the a390, I do sometimes rake the board a little bit upwind, but only in far more wind.
I have a freeship file for the a390 lines if you want it for comparison. It came from the documents list on the Open Division 2 Facebook page.
Cheers, Mikey.
Does anyone still build/manufacture D2s?
Or are all the boards out there 20 or so yrs old?
They are big in Europe but where did all the boards come from.
Mikey, whether this actually gets built is a whole other story, at the moment it's a "design exercise". 
The design spiral with tortured ply is a constant compromise. Ply will bend in either direction but very hard to bend in two directions, this is where the torturing comes in. You can get bending in two directions but it takes a lot of stressing of the skins. It means you often have to play off bend in one direction against bend in the other. This is what I came up against with the stern taper. I tried to pull the stern in more like the Lechner but this seemed to indicate that I would have to straighten the rocker more that I wanted. I decided to go with the more rocker, straighter outline route.
The bigger issue with this construction method will be the bow. I'm pretty confident I can get the back 95% to work OK but the bulbous bow is really pushing the envelope. I guess you could put in a foam block and shape it but that defeats the purpose. Unfortunately this isn't a problem that can be solved on the computer screen. You actually have to build the thing and just try to bend it!
Anyway, for now it's just a virtual board.
BSN, as far as I know even the Euro's stopped making Div II boards in the early to mid 90's. Exocet did a Raceboard with some D2 features recently but it's not a pure D2. It seems that a lot of people have held onto these boards over the years but it's hard to get them to part with them.
Virtual boards are fun too!!
Perhaps introducing a shallow 'v' at the back, or even throughout the entire length, will open up the possibilities.
Jethro, I had a look at your stand-up build posting - excellent work.
In regard to the tortured D2: How about a vertical stem - which lengthens the waterline? Could you still get sufficient volume in the nose? And then cut 10cm off the tail so that it might fit within Raceboard rules? Yes similarish to the Exocet 'D2' - but I think it's problem was possibly too much width in the back half and too much wetted surface. ??
Interesting! Hard chine Div II. Why not.
I like it.
I'd love a ride report copied over to this thread if and when one comes available. Are there any other photo's?
Lot's of footstraps.
Nice video Mr. Foils (or do you prefer Nelson?)
It's interesting with the vee running the whole length of the board basically. I like it!
What is the actual Facebook page it's associated with? Is it a business or a personal site?
AyreForce, Unfortunately the pointy bow isn't an option because it narrows the bow too much at the deck line. If I was to do a pointy bow it would be longer and look more like the Jim French "Darts" from back in the days. Maybe a bit of reverse bow like my paddle board, just to be trendy. Cutting the Div II length down to fit the Raceboard rules is also not really on because Raceboards have to be production so I'd rather keep the length and maybe go a bit narrower to get it nice and slippery! 
Jethrow
Indeed, nice video. Thanks.
It's good to see that the 'vee' and flat surfaces are a choice not dictated by build method or ability. (This I presume from the lovely curves on the deck and the general smartness and complete professionalism of the board as a whole.)
The board is certainly throwing it's share of spray off the bow.
www.facebook.com/groups/OpenDiv2/1533859999964838/?comment_id=1596522733698564¬if_t=like¬if_id=1469770715382189
closed group of DivII addicts , loads of information
Nice job "made in France" !
teamtregor.wordpress.com/2013/11/18/fabrication-du-moule/
Hard Chines will definitely help stability in keeping it pointed upwind and because it is flat it will most probably get up on the plane faster in meduim strong winds. Diminished wetted surface when sailed on the chine vs round displacement board will only be valid in moderate breeze and it will be interesting to see which one generates less drag and is therefore faster ? My bet the round bottomed ones.
One thing is for sure though. Getting a straight V to go about or gybe at speed is not going to be easy as it will ust want to carry straight on... Lots of push and grunt in foresight.
In very light winds I'm positive a round bottomed D2 displacement board will be faster, so apart from the apparent superior stability of the board I'm certain this is not a breakthrough design.
Been testing and racing for many years and this ressembles the first double concave V in short boards to get them planing sooner. Its the only thing this design will be good at. Getting on the plane earlier in the same strength of wind.
Oh well, if pumping is unrestricted that means I'll just go sail my cat instead. I want to be able to sail, not sit there pumping endlessly for hours on end.
In Australia the Windsurfer One Designs ban upwind pumping in course racing but allow it in the marathon, slalom and downwind legs. We've had no significant problems with people trying to sneakily pump upwind. I can't see how it's any more difficult to monitor pumping in boards than it is to monitor kinetics in Lasers. In Lasers there are juries on course at the worlds but not at national and state titles and yet no one pumps or rocks illegally to any significant extent.
Whether triangles are "effective" is a matter of opinion. Plenty of people still like reaching - it's a nice chance to just go fast. Sure, it's not as tactical as windward/leeward racing but not everything is about tactics.
Just confirming that I'm not a starter. Apologies.
Chris I'm pretty sure Eric cleared up the pumping thing earlier in this thread saying 'No Pumping' . No doubt he'll reconfirm though.
Hello Guys,
I'm just back from Brest (yesterday), where I was participating to 2016 European DII and RCB. 5 days of nice racing.
We were 2 sailors using type B sails (max 7.5) so we've been deeply diluted in type C division (up to 9.5) and therefore raced from the behind :).
But no problem. I was not there to make a result but mainly for helping organization and IWA to relaunch D2s.
I hear your comments above about pumping and different types of course. We are working on it and we will need your contribution also.
We will be few D2 sailors in Brisbane so I believe then we can easily discuss it together.
I can tell you that pumping was seriously discussed between sailors in Brest and they finally went through a kind of compromise for a couple of races.
So no worries. Goal is to fill starting line with as much as possible D2s and not discourage anyone to participate.
Ah!...before I forget..I'll need someone to lend me some equipment, whatever it is...:)
Again, for me, more important is to be there and to participate.
I'm about to pay Event fees and buy flight ticket...But remember, we must be 6 sailors at least....So Go guys, Go, chase for D2 sailors and
register to attract others :)
Let me know if you have any questions.
See you soon
Cheers
Eric
Hi All
The ski season has finished and the sun has started to shine and thoughts have moved to sailing.
Unfortunately my best intentions of doing some winter practice failed miserably but I have located my board in the garage ceiling and think I know where I stashed my sail. The board looks as unstable as ever and a 7.5 sailbag appears biggers than the old soft sail.....
Good news though I did formally enter the event and the cheque is in the post. I think that makes two of us and despite a current guaranteed podium position we still need some more entries to have an event.... I hope meet some fellow D2 :tragics in Qld. Cheers Geof******avidson D2.
I completely missed out on my winter practise too, but I'm hoping to get the A390 out soon.
I'm a bit puzzled about Eric's post and the mention of 9.5s. I thought the D2s were only going to use 7.5s? And do we know what sort of compromise about pumping we're talking about?
Not that I'm able to be there, however....
Don't know regarding Brissy but the recent D2 inclusion into the NSW Raceboards is listed as 'C type' ie: 9.5's.
Not keen.
Hi Guys,
You can use 3 types of sails
Type A, typical triangular 6.5 3 short battens sail
Type B, such as Mistral IMCO,Velazur 7.5 or Neil Pryde Lechner purple Olympic full battened 7.3 sail
and
Type C , which opens to larger surfaces...we allowed 8.5 for light weights and ladies and 9.5 for heavy weights (starting 78 kg and above)
Type A are still very popular in Central, Eastern Europe while it seems that Type C have out passed Type B is western Europe (France,UK, Esp, Swe...)
What is prevalent in Australia?
There won't be D2 legionS sailing at Brisbane (I would be surprised) so I anticipate it will be hard to make divisions by sail surfaces or even by weight.
Can we align between us and agree on sail surface to use?
for ex: We could decide surfaces by weight (use Kona system? )
It is up to you...
Hi Chris
I think he was talking about the event in Brest he recently attended where the majority of the fleet used 9.5s.
The QLD event sail size is 7.5 as I understand. There are apparently three sail sizes listed in the International D2 rules.
I may get to Canberra for a practice sail once I have dusted off the cobwebs.
Also he and a Spanish guy are looking for gear to compete with in Nov. Any ideas?
Cheers Geoff.
Thanks guys.
I'll try to contact someone I know who has a D2 that he may not be using. It's a Lechner.
I can bring up a board of unknown type if someone is desperate. It's got a mast track and fully retracting CB.
