Delta rig

Is any one interested to this type of project ?

There is no name yet to define this type of Rig, Gary Hoyt called Delta Rig, Phil Bolger Staysail, other called simply Cat. The problem is that the mast is positioned at the end of the Hull close to the Stern.
Only one single sail acting as a big jib. No main and no mast disturbing the air flows to the main !

Little history :
The first boat with this type of rig was constructed in 1992 by Nicolas Montgomery in Florida. Was an expensive prototype because of the technology limitations, it was difficult to build a mast capable to maintain a very stiff forestay. The boat structure presented some difficulties to. In spite of that proved to be very fast and easy to sail.
In the Phil Bolger book “Boat with an Open Mind” retrace the full story.

Later in 1984 the CorSair 24 was developed. Was also easy to sail and very fast under strong winds.
In 1994, Gary Hoyt wrote an article on Sailing World dedicate to the Cyclone of Mr. Simmons from California.
So far I knows one of the most active Yards designing Delta Rigs is : of Brian Eiland.

More about various project :

Some pictures here below of real boat using the Delta Rig configuration :

In 2003 I was attracted by the Staysail design proposed by Ph. Bolger in his book mentioned above, and I decided to develop a sailing model called CD-CAT based upon a simple class M hull. The results obtained were very good, very fast model, no nose down observed, fast reaction and very good accelerations. One defect observed, the jib is behaving as a wing and as such is sensitive to the wind incidence, outside certain limits the stalling condition occurs. The range for better performances is reduced to 5°-6°. Not easy to control when the boat is 150 meters far away. Good training is needed.


my first project made in 2003 was the CD-CAT . At that time I tested a couple of sails materials.
Some pictures here with a Blue nylon cloths generally used for kite.
The general idea was to use the same sail surface of a Class M to manufacture the Jib. The surface was 7200 cm²
The hull construction limited to the use of balsa sheets of 3mm and than covered with a couple of 80g/m² glass/epoxy.
Most important point was to decide the mast Tllt in order to postion the sail CE against the CLR .


Some weeks later a new material was used for the sail and the jib was attached to a swing boom.
This solution proved to be good when running because the CE was maintained close to the boat.
Was very good until the boom started to bend and finally one hour later broken. I managed to make a new boom, but never tested also beacause suddently called up to design a new Class M : the Studio3 the last of a design serie.

Today I wish to come back to this design using a spare hull of my CD65 project an RG65 Class.

I will continue this tread only if some one manifest some interest and after the ETNZ IACC 120 will shows up a completed boat ready to sail.



Claudio, thanks for starting this post, count me in as interested.

I like to experiment and would like to learn more from your experiences with this rig. I notice that in your drawings you sgow a bipod mast - what if the bases of the bipod legs were in the hulls of a catamaran - just thinking out loud.


Hi Ray,
I think it exist already, try the Brian Eiland site …

Hi Claudio,

I have the mould of my ETNZ AC 120 sitting in my workshop (3 mm balsa) and I have already put 2 layers of 80 gsm FBG over the hull and stripped out the shadows with the idea of using it as the basis for wingsail experiment later.

This project sounds more interesting & challenging, so I too am very interested in trying this concept, once I have finished my AC 120 build.

In the mean time I will study the concept further in preperation for you to lead the way.

Cheers Alan

Great ! Alan,

first I would like to respect the excellent work you are doing for the ETNZ, therefore before deviating the attention to other subjects, I let you and others to finish up before continuing in this new project.

Tanks for the interest expressed, I appreciate


lets go smaller. what about on a footy… could the jib provide vertical lift IE to help keep the footy from buring its nose on the down wind runs?

Maybe I’ll work on my 507 thats not getting much sea time right now…

a “wishbone” mast out of small carbon tubes to a forestay /pivot point…

you’d only have one sail to “tune”

time to go to the hobby store for some carbon…

YES Marc,
because the wind resultant force is orthogonal to the stay, or at least is what i suppose.
Pratically I observed the real test performances on my old design.


It looks like being able to change the mast angle allows you to move the CE instead of guessing and making more holes in the deck.

Hi TomoHawk,

It is correct in order to cope with the wind forces, you like this simple idea ?


Yes, I like it. Thinking for just a minute, I don’t think I could mount the mast in the stern without adding much weight for bracing, unless someone has an idea for that.

Thanks for sharing.


I drilled two holes in the deck of the 507 one on each corner I’m letting it set up over night and then I’ll pull the tops of the mast together (wishbone) and see if it holds. I was trying to do it with out having to cut into the deck of the 507…or use any stays or shrouds…

when I get home tonight I’llt ake a few pics…if it works…

Sounds like a good idea with the double spar, but you’re gonna need a ply doubler under the deck probably. Could you pre-bend the spars any?

this was the simplified exploded view of my first CD-CAT if may help !


I’ll probably end up having to add some supports to the 507 deck(thin plastic) and transom(plastic) to handle the 1/8" carbon tubes on each side I did not add any supports in my first try so when I get home we’ll see how it looks. the deck is already in place and glued down so I don’t have any access to the transom any more unless I cut teh deck, and I’m not ready to do that since the deck also supports the rudder tube…

I glued the tubes such that they are V shaped and wider than the hull at the top. so when I pull the tubes together they will be under tension. so no need for shrouds.

first attempt. I don’t like it. too much tension in the rig…I doubt it would sail well in light air…

I doubt me to!
You should advance the bipod some cm and then keep the tension with backstays to counteract the tension of the forestay. Obviously the compression loads will supprted by the hull sides.

I like having the mast bases at the transom more structure to glue to… the CF tubes are light enough have enough bend that the back stay shouldn’t be needed. At least on the footy scale…

so tonight I’ll pull em out and make them more upright IE only about as wide as the hull at the top more “U” shaped than “V” shape.

Why did you use tubes instead of rods?