Wingsail Monohull

A wingsail, on a hydro foiling monohull Moth - you’ve got to be mad? …well looks like it’s helps :cool:

Who will be world first … RC monohull with a wingsail ?

They had to revise the NOR for the Moth Worlds (later this month) in Australia, because several entries showed up with wing sails.

It’s already happened. The 1954 US DX Class Championship was won by an X-Class model named CD-min. A 1000 sq in wingsail with flap, was fitted by Francis Reynolds of Redmond, WA to a modern “Clockwork Orange” style of hull and took a convincing win from several A-Class boats in the fleet that were sporting upwards of 1,500 square inches. Fin and bulb hull, radio controlled rudder with wind vane assist for trimming. Boat is still in existence and eventually bound to Mystic Seaport Museum’s model yachting collection. Rod Carr

Hi Hew, yes I saw that, I’m following the Zhik moths worlds in Australia to see how they fare.

Rod, …blew my socks off with 1950 ! have been searching the web and can’t find anything on DX Class or the boat CD-min, is it possible when the boat arrives at The Mystic Seaport Museum, that some can take some photo’s & post ?

Cheers Alan


“wind vane assist for trimming”

I remember reading an article - I think it was on the Vintage site - about a boat that had the wind vane hooked up to the sail winch so the sail was always perfectly trimmed versus the always shifting apparent wind (direction). I cannot find the article online and I am glad I made a paper copy, which I stumble on from time to time. I remember the article said the concept was outlawed and that the boat was much quicker than all others that it raced against.

I do not think it said that the boat had a wingsail, but I can imagine that this sort of setup would be very beneficial on a wingsail rc boat.

Here’s the article in question.



What an amazing gold nugget of history, Earl thank you, it one of the most riveting articles I have every read on RC sailing and Francis Reynolds is a true pioneer.

His mono-hull CD-min with the wing sail would rate at the top of sailing technology tree in my eyes some 60 years after it was conceived, his quote of “Progress is constant except when it is forced to go backwards” is so close to the truth, I’m imagining what would have happened if the Americas Cup had adopted this technology for mono-hulls ?? …hmm

First Question: Are there any technical or design information available on Francis wing sail ? that can be used by modern model builder that will keep mono-hulls at the forefront of RC sailing technology ?

For a more modern discussion and description of automatic sheeting systems, have a look at an article in the Spring 1990 issue of U.S. Boat and Ship Modeller titled “Automatic Sail Trimming.” That article, complete with photos, describes the hasty automatic system that Rod Car and I cobbled up for one of his boats four decades after their use in MYRAA DX-class racing

Second Question: Is this 1990 article available from anywhere ?

Cheers Alan

P.S Francis Reynolds … Welcome back to the future !!!

Tks Earl for an enjoyable read. it made me wonder whether my mini Riptide would be RG65 class legal with automatic sheeting, :wink:

That would trigger a real bout of sea lawyering :slight_smile: When I was editing Francis’ article I wondered what would happen if somebody put a PIC-based automatic sheet system on an IOM and showed up at the Worlds with it. :slight_smile: :slight_smile:



Amazing read, thanks.


As far as I can judge from the rules, D.2.4 (a) (3) “One sheet control unit.”, it would appear to be allowed. If one built it as a unit containing 2 independant servo outputs, it would also seem to allow jib adjustment. But, as you say, the sea lawering would be likely to drag on. Wing sails seem to be a no no, “The construction shall be: soft sail, single ply sail.” as well as the mandatory general rig specifications.

If I read correctly the 2010 RG65 rules do not require soft sails. Could be interesting.

Before everyone gets too excited, I need to report on some actual sailing experience concerning automatic sail trimming. Back in the late 1980’s, a very clever skipper named William Whitten adapted Francis Reynolds system to an EC-12. The transmitter stick could be used to override the vane that was monitoring the wind, but left to its own devices, the vane did a pretty good job of keeping the boat always sailing at a constant angle to the apparent wind at any moment. Unfortunately, to be of value on the race course, the system had to be set with very narrow limits between which the vane would signal the winch servo to adjust the sheets, and even on a boat as steady as the 25 pound East Coast 12 it was found that the small changes in course caused by waves, and’or by the skipper fiddling with the rudder combined to make the sail winch run almost constantly either in or out as the vane tried to maintain its setting. The result was that a 1600 mah winch battery was used up in much less than an hour, and larger batteries would have been extra weight for a racing boat to carry. So now try to shrink the system down to an IOM? Probably not easy to do. The IOM has much more lively motion in both pitch and yaw, will keep the winch running all the time, and doesn’t have the weight allowance for bigger batteries. However, there are those who will want to experiment, and that is certainly OK, but don’t expect it to win you the World Championships…at least not this year. :slight_smile: Rod Carr

Hi Earl.

When I read this, I thought ‘no problem - it should not take a sea lawyer’. However looking through the rules, it is not straight forward.

First, would it be legal in a full sized boat to have a mechanism auto adjust the sails for the point of sail and apparent wind? An auto helm as used in long distance short handed races is usually included in the NOR/SI as an explicit allowance. Auto sail in unusual.

The RRS speaks of the crew trimming the sails, but in a context to do with propulsion/kinetics (R 42)

R 52 speaks to the use of manual power (not motors) but this is deleted in Appendix E for RC sailing.

In the ERS, c.5.2 The crew operates the boat.

In the IOM class, which is a closed rule, you can only do what is expressly allowed. So the fittings for a wind direction actuator that is connected to a sail control unit is not expressly allowed and so would be illegal, even though a wind indicator is allowed.

The IOM class rules require that the sheet control unit be RC as it is in that section.
C.5.3. Remote Control Equipment b) sheet control unit shall control…

In D.2.4 again the sail control is under the section Radio Control equipment.

While a wind indicator is optional, it is only allowed if attached to the mast. F3.3.b.1 and it is an indicator. To me an indicator shows the direction of the wind, but cannot do anything else. So a wind indicator is different from a wind operated actuator.

There is a competition for autonomous model sail boats. Install a gps and computer to set and sail the course and figure how to sail to weather and tack/gybe on shifts and headers. Connect a wind operated actuator to control and adjust the sails and you have an interesting project.


The “sheet control unit” allowed in the rules does not specify its design or mode of working. Therefore, if a vane is intrinsic to its functioning, then in my view it must be allowed, in the same way that a winch or lever arm are currently allowed although not specifically mentioned in the rules. I think we are proving Earl’s point.:wink:

It could be possible so far the dedicated servo is removed ! the question is : OK for close hauled, but what about running ?

Nice post on Italian forum

babelfish makes it more interesting


the rigid sail will non work for a monohull model, simply because the sail need a lot of speed to express his capacity that a monohull cannot offer as a multihull, without the bulb, that is generally equivalent to 55/60% of the total weight.

First thing is we have two interesting topics:

  1. Wingsail Mono Hull
  2. Automatic Sail Trimming

Dick or Earl as moderators in this section, before we go any further is it possible to start second threat “Automatic Sail Trimming” in this technology discussion section and transfer the relevant posts across … before we all get our sheets in a twist here :stuck_out_tongue:

Cheers Alan

Claudio thanks.
Was just looking good

Is Ok with me

Cheers Damjan