Help Identifying

I bought a hull from a guy and neither he nor I know what it might be. It came without a keel which makes it even more difficult. It still has the flash from the mold but no identifying label inside.

It is 1.2m long and has a 10.5" beam.

My guess it is an American Cup racer from the 70s or 80s.

Help identifying this rig would be appreciated as I then can get started building it. Of course I’ll need to ‘beat the bushes’ (so to speak) for the plans and sail layout.

1.2 Meters is very close to 50 Inches.

Is it 50 Inches long? If so it is a Marblehead 50/800… and one of thousands upon thousands in existance (there are nearly four thousand Ms registered in the USA alone.)

it might be an infinity 54… the stern looks about right . as well as the length. you could look at some of the pics for it good luck

The underwater parts don’t look like anything like an Infinity 54, which is a one-design class.
See this photo:
Yes, I know, the I54 in the photo has a keel on it. I’m referring to the hull shape, without the keel.

The i54 is also 54" long, which would also be roughly 1.4 meters and bigger than his original length description.

Do you have a ruler that you can measure the length?
Metric or Imerial is fine, Take an accurate measurement in CM and convert that to inches.

Is it 50" Long?

It looks like a US12
or Canterbury J

The length is right but the beam does not match either.


It definitely is not… nor does it look like either of those.

Hard to judge age - but could this be something originally made by Vortex ?

It can’t be a Marblehead as the length is not correct. Rules call for a hull 50.20" to 50.75".
The Infinity 54 has a much different bow on it and is longer.
The US12 has a nicely curved bow and a keel that is much larger than the mounting pad on my boat. It calls for an OAL of 46" and a beam of 9".
The Canterbury J has a max beam of 8.66" and the bow, keel and transom are all different.

My boat measures 47" or 1194mm. The beam is anywhere from 10.5" to 11" 267mm-279mm
Starting at the nose, the bow is at approximately a 45 degree angle for 45mm and then it angles downward but is straight all the way to the keel mounting pad. The pad depth is about 170mm from the deck line. Aft of the pad it has a raised rib about 10mm high that runs for 277mm. It abruptly stops and there is 260mm of smooth hull to the transom (both side radi converging to a slight form in the middle).
The hull has some resemblance to KC-2 or the KA-15 or even US-26
This boat has an odd shape that makes it look as if it were pregnant with that large bulge in the middle (maybe even twins).
I need to start somewhere so the keel size and weight are first. Mast location and then the sail plan.
Any help in figuring these out would be appreciated.


Oh well. You gave an original measurement of 1.2 Meters. which was close to the 50"… But now that there’s a more accurate measurement it’s clear it’s not an M.

At 47" I haven’t a clue what your boat could be. Could be just a one-off of something that was made.
You shouldn’t have any trouble building it though… Don’t need plans just concepts.

Good Luck

Walt … you got me thinking.
could this boat be one of the models they had floating around the new york yacth club back in 83???
if it is one of them… IT is not KC 2… that stern is not canada 1… but was looking at it… could it be a model of liberty? or even freedom?
I cant see it being one of the challengers… most had a ranked stern. like kc1 had that rounded transome, aussie 2 has the sharp stern… this could be the boat… but as to who made the model… no clue

As others have alluded to, she certainly has a scale 12M look about her. I guess in terms of identification you really need to ascertain whether or not it is/was a commercially available hull - is the material an ABS type plastic or GRP? If the former I’d hazard a guess that it is/was commercially available (higher tooling costs) if GRP then she could easily be a ‘one off’.

Either way, as previously stated, she certainly has the 12M look and in terms of completion I’d be inclined to research that type - there’s plenty of info available. If you’re inclined to accept the hull as just that, a hull for fitting out, then the minutiae of the design detail doesn’t really matter - you’ll end up with an attractive hull form that certainly has the potential to sail well.


Edit: To assist in your design process check out this thread started by Claudio -

Although it won’t specifically identify it’ll at least give some ideas as to the keel & rudder configurations and sail plans and may also assist in pinpointing which era your hull may be from.

Edit again!! My initial response was from looking at the pics on my phone (small screen, lacking detail) so having viewed again she’s obviously GRP & thus more likely to be a one-off…

profile kinda looks like Australia 2

Stars and Stripes maybe

It probably is a one-off hull. I’ll build it as best I can and use the scale mast location (maybe make multiple mounting points for it).
Does anyone have a drawing of the winged keel that I could use to make a mold from?
Also, is there a ratio or constant that can be used for the optimal location of the waterline?
I know these are rookie questions but I’m sure I’ll learn as I go along.

I would figure maybe an inch or less behind the bow knuckle and maybe an inch forward of the transom…but that is a full on spit in the wind type of guess…if that hull was sitting that waterline I think it would look nice…

winged keel…good luck on that…would look realy nice, but nothing I can do in that department.

fill up the hull with ballast and see how much you need to hit the desired LWL… and that start working backwards… rig, electronics, deck, ect… maybe you’d get someone to draw something up for ya…

while the boat is not the proper length… you should be able to buy an empty keel shell and work on modifying or building it up to the proper size…

or maybe victor would be willing to make a one-off for ya…


the hull looks like either Intrepid Courageous, or Freedom to my eye, but not a perfect scale rendition:

Also, if it is 48 inches long, it should probably be only about 9 inches or less wide.

You can probably find the waterline at the stern by guessing on a reasonable chord for the rudder, probably about 1.5 inches, and the waterline should be near the trailing edge of the rudder.

The bow should have at least 1.2 times the freeboard of the middle of the boat.

IMO, none of the J Class/12Metres from 1980 to 1986 as per the ‘bible’ has similar transom, typical of S/S design. None has small profile from keel to rudder and none a rounded bow with a long keel.

With the possible short keel as in the picture, it may be possible to search in the 8Metres or even in the 6Metres designs


This is what I found on the web under 6Metres :


I think you ‘hit the nail right on the head’. It seems to have all the characteristics of a 6 meter model.
I guess I’ll have to order up the full size paper plans unless someone has a PDF file of the boat. I searched the net but couldn’t even find the dimensional requirements to make the boat race legal.
Thanks to all

probably you miss this description :

This MYA national class is a scaled down version of its full sized counterpart and offers a traditionally graceful appearance with steady performance and handling. Boats are typically about one metre on the waterline with long overhangs. The draught is restricted to around 230 mm (9 ins) with the displacement typically 12 kg (26 Ibs) and the sail area relatively large at about .7 square metres (1100 sq.ins).“Un Quote”

Therefore I assume a total length of about 145cm