You can build a phantom from sheet ply, I know that there are glass boats with "wells" to give less than appalling downwind ergonomics, so that arrangement could be replicated in ply. Is there any reason why you wouldn't want a phant?

If for whatever reason thats not cool and you don't want something completely custom, have a look at the woods designs stealth or zest:

http://boatplans.cc/woods-designs/stealth/
https://www.sailingcatamarans.com/index.php/designs-2/46-beach-cats-and-dinghies/436-zest

Richard Woods is the daddy at ply kit designs albeit generally on larger multihulls

For those that like something more radical than the OK, he does some other cool boats too  http://www.leechboats.com/sail" rel="nofollow - http://www.leechboats.com/sail

BTW - well worth getting a try in the OK class demo boat. Lots of sailors (inc me) over 6ft and 100+kg in them. Think the rig might be further forward and more upright than you maybe tried before.

 

Get hold of the demo boat for a try - there's nothing to lose trying and if you like it get a Leech kitboat

Almost certainly 'compound curves' - the Phant had a lot of freedom to allow self builders to stay within the rules building in their garages  - later this was 'used' to build in compound curves into the later composite hulls... and the plywood boats started to struggle ...  I would assume the OK has a much tigher measurement policy.

Hi Mike

The Phantom mould was taken from a fast wooden boat so no need for a slow hull shape.

Building the hull of ply it was a problem to keep it within weight John Claridge did build some fast lovely  double bottom boats and knowing John down to weight.

I think the woodies in the fleet are using either tin or early carbon rigs not the current rigs of choice.

Think that makes a big difference as well. 

With laser cutting a Kit would be an option, I wonder what the cost of good marine ply would be in comparison with a hull from Ovington.

Plus the painting of course.

* The basic principle is much the same as a box girder bridge, admittedly the Phantom has it's double bottom to add rigidity but it is never going to be as stiff as the full height box sections of the OK.

Not sure about 60hrs, watched the video, lots more than 60hrs 

So Woodie Phantoms are heavier, less torsionally stiff, may not have compound curves, are using older rig and not double bottomed so may carry water.

Given the success of the OK plwood format could these problems be designed out if class rules were relaxed in some areas for wood boats?

If you have a class that already has compound curves available via the composite route it still does not matter how tight you then set the measurement rules .. whatever the rules or wording you simply cannot make ply bend to match the compound curves that are very straightforward in an optimised FRP composite.

'Modern' phantoms will always be faster as they are simply better shaped than can ever be achieved via bending and twisting 8x4 ply sheets.  You cannot copy the compound curved shaping.   Look at all the other traditional, originally plywood and chine, classes that made the transition down the years (with the possibly partial exception of the OK granted) - the ply build has died on its knees as a competitive or worthwhile build route. 

Cirrus

as per ,y previous post all epoxy Phantoms hulls come from a mould taken of a wooden boat. so don't se where the comment about compound curves come in. 

Hasn't a Magnum moth hull got compound curves? They were built from ply.

3mm ply.......

With regards to why a wooden OK can still be competitive and a wooden Phantom not, I would suggest that a wooden OK, given the size, mass and panel sizes, can be made "very" stiff.  Probably stiff enough, if not as stiff as a composite one.  A wooden Phantom at minimum allowed mass has large panels with minimal support, so it is easy to see why it cannot be anywhere near as stiff as a well-engineered epoxy sandwich boat. Having said that, it is not immediately obvious why a less stiff boat should necessarily be that much slower.  It is not as if you are trying to control jib luff sag with rig tension.

Jim it is indeed the case that wood boats are as fast as foam sandwich ones in the OK. It is probably for all the reasons above but it is encouraging to see that this is a possible route again now we are all supposed to be more careful about sustainability etc. The table below is from the last Worlds in early 2019 taken from ( https://www.yachtsandyachting.com/news/215612/Individualistic-choice-of-OK-Dinghy-Equipment" rel="nofollow - https://www.yachtsandyachting.com/news/215612/Individualistic-choice-of-OK-Dinghy-Equipment ).  

The article also sys that only four of the top ten were production boats, the rest being either home built, or built using Dan Leech's CNC kitset plans by professional builders and the third placed boat in Auckland was 35-years old Icebreaker. 

Er Contender?

Not sure what the contender reference is intended to mean, but the wooden boats are cold moulded, aren't they - not ply. AFAIK Signore Bonezzi(?) in Italy still builds beautiful hulls but I bet they are eye-wateringly expensive.

+1 from me on that sentiment 

Wooden Bonezzis’ were plywood, still very sought after, as quick/quicker than the FRPs’.

most of the reason why the PY plummetted was down to the epoxy boats being up to 14 kgs lighter than the GRP and even more on some wooden boats. The carbon spars did not make that much difference in the earlier days other than perhaps the helms not being knocked so much.

Not from the mouth of one of the 'developers' of the Phantom epoxy hulls I have spoken with on the subject !  .... besides don't believe me just put a rigid steel rule across a epoxy modern hull and see for yourself.... They did not all come from a mythical single ancestor without some subtle but still significant  ... eer  'tweaking' along the way !!   Why would you not tweak the plug and tooling to real competitive advantage when the set tolerence rules allowed a medium sized bus to be driven through them and you were changing materials anyway (and therefore also changing the limitations imposed by the materials involved).  

You can bend ply and you can also twist it  but if you effectively get into cold moulding it, as has already been said, it is not really regular plywood anymore and that really is the only way to get a compound curve into a multi-layer wood  shape ...  And frankly if it was even practical in a formal production sense it would still be more efficient to build in foam and epoxy imo if allowed  - so why do it ?

And as goes with the Phantom you can add many other classes to the same list of  those suitable to be 'tweaked' when a switch to moulding went through - Solo, Fireball, Enterprise etc spring immediately to mind  and you will think of others I'm sure (though lets agree maybe not as completely with the OK maybe !)

All very hypothetical as development cost would out weigh  the number of people prepared to take the risk and  spend the time actually building the resulting boat.  

All a UK perspective though, lively home built  Proa scene in Poland because it the most boat you get from the least materials. 

Well I never knew that. Always thought they were built from summat  exotic. I stand corrected.

I think that is an anomaly. My cold moulded IC was no comparison to the epoxy carbon foam sandwich one that replaced it. 

Well, isn't the Contender known to be quite heavy?  So if the weight limit is high, it makes sense that wood can be reasonably competitive, witness Contender and OK.  Whereas if the limit is low, as with the Phantom, wood cannot really compete. 

+1 that’s the death of ply boats in a nut shell. Newer boats designed with a  10kg lower weight for questionably small increase  in  performance but enough to make GRP boat building profitable and obsolete lots of great wooden boats. 

but in the Phantom's case the boat was already designed to be 61kgs but it was rare that any wooden boats actually got near it (Claridges apart). The GRP boats didn't on the whole either but they enabled owners to have relatively maintenence free sailing.

As for Jim's comment about the frp/grp boats etc, well all of the early epoxy boats came from the same mould as the polyester boats so the performance gain must have come from the weight or stiffness gains (assuming there were some).  I certainly know that when I moved from a poly boat to an epoxy one it was like a different class, so much more responsive, in fact too much and I fell in backwards on a reach. My epoxy boat had 1.5kgs cof correctors too so a massive overall difference to the old boat. I was still using a tin rig at the time and it didn't slow me down overall.

Bonezzi Contenders are cold moulded in wood using epoxy resin infusion techniques. I suspect if you told Mr Bonezzi his boats were made from plywood he would be quite upset  

It's plywood, Jim, but not as we know it!

I’d agree with that, that the conservative weight limit of the Contender and OK allow wooden construction to remain competitive, also as mentioned earlier, the shape of the OK being quite boxy promotes quite a stiff structure.

I still think that going up to the bloke with the shiny new Bonezzi Contender and saying "how are you liking your plywood boat?" is asking for a knuckle sandwich 

Unfortunately for this argument the OED says "A type of strong thin wooden board consisting of two or more layers glued and pressed together with the direction of the grain alternating." which is slightly less definitive thou "a type of strong thin wooden board" does imply that the material starts out as flat.

thats easy, F****** Really Pricey