12mR scale 1:12

I’m currently building a 12mR Columbia, Americas Cup winner from 1958. When producing the plug, I altered the stern slightly, making the hull an additional 4 cm longer compared to the original.
The original boat can still be built, by cutting the stern back to the original negative version.
I’m posting some pictures to show the progress. 13.8kg, 30.4 pounds of lead, 178cm or 70 inches long. Mast hight will be 210cm.
/Lars from Sweden

Very nice Lars, keep the pictures coming.


Walked in the rain today to test float the boat with the new keel I just poured.
I still have some trimming to do on the lead. The boat sits a bit front heavy in the water.
It is a good thing to have a prototype hull and lead to work with. I can fine tune and then hopefully get it right on the “real” boat.

Well, One more trip to the Swan pond today for “tank” testing.
I think I now got the lead shaped the way I want it. 14.2kg of lead and the hull floats very nicely.

Thin plaster cast submerged in dry sand in home made box. Works perfectly for casting lead keels.

The build is progressing. I will post new pictures later today. Been on a business trip this week, therefore not much progress on the build during the week.

Sickness, business trips and vacation has put the project on hold for the past month and a half. Rudders are in the works, and some other interior parts have been made. I will build more during Christmas break.

The 12mR build is progressing

Test rigging the new carbon fiber mast. 210cm tall.

Nice job Lars,did you make the mast yourself?If so could you post some pictures?Go on with your nice work. Gilles

Hi Lars,

what a beautifull hull!

Please keep this thread up. I am just collecting for a friend some drawings for a smaller mR boat. may be 5mR or 6mR. The swedish veteranbatsarkivet has a lot drawings…



I bought a round carbon fiber tube this time. The jumper spreader and all the other fittings, are home made. I can post some pictures later.

Columbia’s coming on really well, you’re doing a great job. What sort of diameter carbon tube have you selected for the mast and is it ‘high modulus’ or just ‘what they had on the shelf’? Also, what sail area will your ‘Columbia’ be setting?

Be great if you could post some pictures of the mast & fittings - I’ve started to think about the mast and mast material for my ‘Enterprise’ build.



Thanks guys,
The carbon fiber tube is 12mm dia. I ordered it from a company north of Gothenburg here in Sweden. The tube is 2meters long, I added a 100mm extension at the base. This is made out of aircraft aluminum. I had two ball bearing goose neck and vang fittings, I had machined years ago (my own design). This was the last two…

I forgot to answer your sail area question… I have moved the mast back a little bit, from the original drawing. Two reasons. I think it looks better, and I think the boat will be easier to sail with a slightly smaller main and larger jib.
I’m working on the sail plan right now. I hope to finish tonight and order sails from Rod Carr.

Finally! Sails are designed and ordered and paid! Rod Carr is making a suit of dacron sails. Now I can’t wait for them to show up here in Sweden!

You’ll be sailing her within a month! She really does look fantastic.

Looking at the pictures in post #14, is the standing rigging (shrouds) coated wire or a dyneema type material? Also, for your sail designs did you use a computer program or something far more traditional like a pen & pencil?!
Last question (for now!), what sort of sail winch servo will you be using?

Keep up the excellent work,



are the quotations marked on the sails correct ?

Hello Row,

No problem. Please keep asking questions. The winch I’m using is a SmartWinch from Australia, the 380ES model. I will also have a smart switch mounted in the deck. The rigg wire is from the fishing store. 20kg plastic coated stainless steel wire.
The sails were designed with Solidworks CAD software. I only used the sketch module and took a photo with my smartphone. The rudder servo is a Hitec ball bearing with more torque than a standard servo. I don’t know if it is needed, but I had it laying around.
The Radio transmitter and receiver is Futaba 2.4GHz. My goal now is to finish the rig. I’m waiting for a vang and two rig screws I ordered from New Zealand. They have yet to show up. I hope they arrive today. Tomorrow night I plan to paint the hull and deck with one more layer of Polyurethane paint. After this, it is just a matter of when the sails show up. Rod Carr is usually pretty fast.

Hello CladioD.

The dimensions are in Inches. Did you notice a mistake?