US1M "C" rig

Does anyone have the measurements for a US1M “C” rig? Is there such a thing? I found the “A” and “B” in the construction files but no “C”.

Don , I have the us one meter spar and rig plan from sailsect, and it has a c rig dimentions, but it is a fractional rig.

have ypu asked at the us one meter site:

I would think that a fractional rig would be for an IOM not a US1M, but I’ve been wrong before(many times).
I have been waiting close to six months to be accepted as a member so I can post on the US1M site. No luck

Hi DOn,

I have just posted your question on the US1M site on your behalf. Will bring back any replies.

Don’t know whay you have not beed accepted as a member. Perhaps try again from scratch. Let me know of any problems and I can post an alert to the moderator.


Hi again Don,

I was just reading the US1M rule and there is no specified size for a C rig, or a B rig for that matter. There is no limit on number of suits of sails or complete rigs. (There may be a practice to limit rigs at a regatta - but it is not documented)

The rule states a max measured sail area and a max luff length for the main.

In the construction guide, the A rig is a max height rig thta measures 600 sq ins. The B rig is a lower aspect (shorter luff - wider boom) to also give 600 sq inches.

So my reading is that you can make a C rig of any size as long as it is less than the max specified measurements, such as head and roach limitations.

As I said earlier, I’ll bring over any replies.

Don , it is from sailect( sold through GBMY) , but it is a AMYA US one meter sail/ rig plan. Midwest model yachts now sell it by itself or with a us one meter rig kit.

Fractional rigs have been used on us one meters , though I dont think they are very popular.

If I had known it was for a fractional rig I would not have bought it.

Don I knew I had read some info on fractional vs masthead rigs on the us one meter site.

The opinion is that a fractional rig is good ( easy to tune) with a deck stepped mast, and a masthead rig is good( easy to tune) with a keel stepped mast.

Ah…guys, if we’re talking US1M…

There is no official rig designations, the class is truly a development class. You can call the rigs whatever you want. We’re not talking IOMs, which are limited development with strict one design rigs. There you know what an A, B and C are…in the US1M world, it is whatever you call it. You can build as close to max luff height mainsail or as small as you want.

Now as far as masthead versus fractional…it’s personal preference. There’s no class rule controlling this choice. I’d think most people would go with the fractional if you can get it, for the additional control over the top of the mast…but many have sailed with masthead rigs. I think it depends on what you intend to use as a mast too. I’ve had both on my boat, and no one has ever called it slow.

The Bantock rig design for a US1M is a fractional rig using a carbon tube mast. If you bought sails from Bob Sterne with one of his custom masts, I’d chose his masthead sails. It’s all about what you have and how it’s put together.

Saying you wouldn’t have bought a boat because of the rig is like throwing the baby out with the bathwater.

While we’re on the topic…Alec at Blackmagick sails makes great stuff. I recommend cutting out the middle man and e-mailing him direct. Postage is cheap, even from NZL.


This is the only reply so far on teh US1M forum on Yahoo.

Posted by: “Brad Blackton” [ ](wlmailhtml:{CB0875B1-94C9-4680-9FED-19DB2D361DC3}mid://00000085/! Re%3A%20C%20rig%20for%20US1M%3F) badmanners25

Thu Jun 19, 2008 9:05 pm (PDT)

I sail a 52"luff mainsail cut very flat with about 54% on the main. I believe it is trispi 50 with trispi40 on the luff of the jib. This is the only rig I sail at the moment as I haven’t come up with an A rig configuration I like. I consider this between a B-C rig. Brad Blackton BS sails.

Thanks Guys
So winning a US1M race is kind of the luck of the draw? The guy whose sails most match the wind will win? The only reason I was wondering is that there are 3 of us here that sail US1M and we wanted a heavy wind rig. To keep it fair we thought they should be the same size and I thought I would ask what others use. Sure beats packing 20 rigs and spending the day changing back and forth.


The fact that the class is such an open development class means the boat tuned to the conditions will win…because my boat might be overpowered at 5.75 lbs, with a B rig while someone sailing at 7lbs might still have what might be considered an A rig.

I’ve seen IOM’s with US1M A rigs on them do extremely well when the wind is up. Think about it, it’s a little smaller than an IOM A rig, and it’s such a huge jump down to an IOM B rig.

Anyway, three rigs is the max you should need to cover a wide variety of conditions.

Good luck with your fleet!

Hi Don,

Here is another reply from the US1m forum. . . .

We sail very light boats in heavy air with a small mainsail and jib. As far as
I am concerned it is important to be able to limit flogging sails through tacks and so you will need to be able to be able to aggressively flatten your jib. It is very helpful to be able to vary the jib club attachment/swivel to deck so that there is lots of load pulling the jib
clew down. In other words you should have enough jib club ahead of the attachment point to balance the amount of backstay you are using. It helps to have enough shape built into your mainsail so that the sail can be aggressively loaded with the vang without inverting the top of the

When a light US1M is tacking in heavy air luffing sails are the biggest
factor stopping a boat, putting it into irons. Obviously boat balance is important; tune out weather and lee helm. It helps to have a boat that exhibits low form instability; (when it heels over it shouldn’t try to head up a lot.) Aka: narrow skinny boat

All US1M are different so don’t be thinking that what works for them might work for you; however that being said it helps to be in the ball park.

We sail at 4.5 lbs pretty much all the time. 50-52 inch mainsail 250 -270 sq inches with max roach and a fractional jib around 209 sq inches max roach. Difference between B and C rig is jib. We can fly up to 300 sq jib on the same B/C rig mast to extend the low range.

After many hours I have never felt I needed a smaller mainsail. The center of effort for the 50 inch rig is low enough for seriously heavy air. We also configure our masts with two hounds so that we can rig as a frac or masthead rig.

Recommend using “sailcut” free design software to design your sails. We started using it last fall and the improvement over our old sails was dramatic because the computer cuts are really good at matching luff curves to masts so you will get the most range of tuning from full to flat out of your rig. Sailcut is a shape smoothing software and it really works!!

Trispi 25 works for all sails if you reenforce it with fiber packing tape and
orient the material correctly. Beginners might try building sails out of news print to get close or check inputs before you go ahead and cut up your trispi. Ciao

Richard Saltonstall, Tuesday Night Boat Club— In,