Volvo 70: 22 days!

Thats how much faster the new Volvo raceboat is expected to be than the 60’s of the last few round the world races.
Speed like this is made possible by one thing: a canting keel! These new boats are following the major trend in offshore monohulls: the use of canting keels replacing fixed keels and -for the most part-water ballast as the “stability system” of choice. Once again here is an example of the most sophisticated of modern technologies being applied to full size racing boats.(see maxZ86)
For offshore monohull racing the fixed keel is on the way out!
Can’t be too much longer before the same thing happens in rc sailing…
Power to the Keel!

Doug Lord
High Technology Sailing/Racing

Dick’s points are quite valid. The rush to get these boats may come when the R/C technology is proven reliable.


The one sure thing about new technology is that most people will adopt a wait and see attitude; perfectly natural. Few people have the wherewithal not to mention the personal courage to risk their leisure time on something perceived by the majority ,who don’t understand it, to be something that might not work. That is until some adventurous soul that does have whatever it takes comes up and hits them on the head with it. The most recent example of this in full size boats is the story of the 60’ Wild Oats whose phenomenal success against many other boats including 90 footers boat for boat caught the eye of Roy Disney, Neville Crichton, Bill Lee and many others. Canting keels are now legal in the Volvo 70 Class, the max Z86 class and the Open60,50,and 40 classes as well as in the mini 6.5 class.
While many in the fullsize sailing world have embraced the new technology with open arms investing MILLIONS another factor lurks in the nether reaches of model sailing: EVERY single AMYA development class and EVERY single Internationally recognized development class PROHIBITS movable ballast and, by extension, canting keels. EVERY ONE-NO EXCEPTIONS!!!
This has a chilling effect, to say the least, on many rc designers who design only in the recognized classes…It has been only recently that a new monohull development class has come along,the Formula 100, that allows movable ballast(and hydrofoils for that matter).This class has provided the opportunity for pioneers like Graham Bantock in the UK and John Beavis in New Zealand to design raceboats utilizing canting keel technology where NO opportunity exists within organized(recognized) model yachting.Compared to the open embrace of the new technology in full size sailing in model yachting new classes have to be formed outside the recognized classes just to compete–though there are more and more Open Class regatta’s around.
Companies like microSAIL! and Wind Warrior are investing huge amounts of time and effort-not to mention money -to develop boats utilizng this technology while there are many individuals, such as John, across the globe working on movable ballast models.
So modelers that want to race boats using this technology have to do it outside the regular worldwide organized development class structure for the time being; that slows down development a lot.
But one individual,one boat, one company at a time change is in the air…

Doug Lord
High Technology Sailing/Racing

Not everybody knows that a lot of the best rc designers will NOT design boats outside the recognized classes and the lack of such talented input in the development of new technology is unfortunate. It is not my point to try to convince existing classes to change but to explain the slow pace of the development of new technology in rc sailing.
With the Formula 100 Class the only development class monohull anywhere that allows movable ballast and very few of them around “embracing” the new technology is not easy for an rc sailor. Thanks to Graham Bantock , ,Grant with Wind Warrior, John Beavis and the other individuals and companies involved the use of movable ballast will become more and more prevalent.
One other thing: there are already a number of Open Class regatta’s around the country not necessarily affiliated with the AMYA Open Class that can serve as showplaces for some of the new boats
and I think Stan Abadie will be giving serious consideration to more venues for the Open Class in the months to come.

Doug Lord
High Technology Sailing/Racing

Hey Doug: I was looking at the ISAF-RSD web site a couple days ago. There’s a rules interpretation for the International A Class that talks about moveable appendages above the water line. I’m not that familiar with the class nor what appendages above the waterline are, but there’s a paragraph in the interpretation that says, “Restrictions regarding appendages are given in the “A” Class Rule 4.1.1. Number and shape of fixed appendages are not restricted. Only those which move fore and aft and retracting appendages are not permitted.”
The next paragraph describes the “A” Class (Rule 1.1.1) as an “open class where anything is permitted unless it is specifically prohibited”
This would seem to allow room for canting keels. I haven’t read all the A class rules. Have you found one that prohibits canting keels?
Here’s a link to the interpretation:
And the Class Rules:

Dick Carver

Hearwith images of the new VOLVO 70 class.
What about a 10th scale version with everthing
Doug has ever wanted. Makes a model 2.15m LWL
450mm draft, main luff 2.8m, unlimited channels,
crew of three for racing.Two radios one for the helmsman & mainsheet, second for keel & kite.
Third guy is tactition who is allowed to use binoculars.[:-batman]

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Download Attachment: design_2.jpg

Download Attachment: design_3.jpg

nerds of the wold untie

Dick, early model rulemakers were not the only ones with phobias about movable ballast: see Rule 51 of the Racing Rules of Sailing, page 19 of the 2001-2004 rule book. Also see Appendix E4.7 page 59 “a) ballast shall not be shifted,shipped or unshipped;”
Appendix E4.7 starts out: " unless modified by the class rules." So movable ballast in the A class is illegal since it is not specified as being legal by the class rules. Of course the class rules say something is legal unless specifically prohibited. So there may be the basis of an argument but you’d have to fight like hell more than likely since if it WAS legal in that class all current boats would be obsolete…
Ian,check out the maxZ86 class. A Volvo class would probably be too restrictive in the sailplan and you’d have to deal with Volvo to get permission; seems like it might be a lot of hassle(it is -I’ve done it before.)
One thing in your proposed dimensions: the draft for that size boat should probably be increased or you face the problem of having to have a short squat rig instead of a rig that captures the essence of the full size boat,ie-nearly scale. There are many scale or semi scale classes that made the choice(EC-12,J and others) that they would prefer to have a scale or nearly scale keel and a short rig. My point is that you only see the keel when the boat is out of the water so it seems to me that, while sailing, the boat should look as much like its namesake as possible; to do that requires a deeper keel…

Doug Lord
High Technology Sailing/Racing

Class rules prohibiting “moving ballast” do not necessarily prevent someone from using a canting keel concept. Hal robinson has built a US1M where he cants the mast and rudder instead of the keel (both allowed under the rules) to accomplish the same effect. By canting the Rig to windward, the boat will heel over more and effectively cause the keel to swing more to windward.

I myself have toyed with this idea a bit and am planning on building a similar beast with wings on the keel to react the lateral forces when the keel is no longer effective.

There is also a Marblehead class boat in Australia that has a canting mast. This one has actually sailed. The reports are of blazing speed and a steep learning curve in controlling it.

Based on this assessment, i wonder if using gyros to control the keel canting servo would be a wise move. That would get you back to 2 channels (one for each thumb) and might work just fine. I’ll probably start off with a third channel for the keel and then switch over to the Gyro once I have the bugs worked out…

  • Will

Will Gorgen

Will, I’ve looked at canting mast solutions recently for a client ;what I found is that compared to canting keels they leave a lot to be desired.
When you cant the mast so that the angle of the keel helps to develop righting moment the keel loses some of its ability to develop lateral resistence so you have a more or less vertical rig with an angled keel. Just like in the canting keel example some solution to providing the lost lateral resistence has to be found. If not then the canting mast system will not do well to windward or if the solution is to add more area to the keel fin then the boat won’t do well downwind(see the “New Canting Keel Solution” posting under Technology discussions on this site) There they utilize the wings you’ve talked to me about before but the disadvantage compared to a daggerboard system is that it still has the extra wetted surface going downwind.
The problem on a US ONE METER is that a daggerboard or other retractable foil is not possible-twin asymetrical daggerboards installed at an angle to vertical would work well with a canting mast upwind and be retractable downwind-esp. used with Hals rudder idea where the rudder angle to the vertical is controlled by the mast angle; same on a Marblehead . So while the canting mast can develop more power it can’t be used at high angles(up to 55 degrees) like canting keels because then the fixed keel loses its effectiveness. And because of class rules supplemental area(like a daggerboard) can’t be used. Twin foils like in CBTF can’t be used even if they were legal because they would heel like the keel does. Hal was on the right track with his rudder idea but that means the rudder is more effective as the boat heels as compared to the keel which would change the balance a lot(but in the right amount initially).
In my opinion, canting masts can help in combination with a canting keel , twin asymetrical daggerboards or at relatively low angles of mast cant with a fixed keel but as a substitute for a canting keel they don’t measure up.

Doug Lord
High Technology Sailing/Racing

I played around with the idea of automating the control of canting the keel of my F100 CKTF boat. I looking at using a pendulum mounted on a pot (sevro driver). This would keep the keel at optimin angle of cant for the max right moment. The problem was that the pendulum and the keel would hunt each other and flatten the batteries very fast, so some sort of l dampening system would be required,either dampening the pendulum in a light oil or dampening the signal and thats where I got to, with some help from Rob at RMG Winches.
There was going to be an overriding control from the shore.

As you “cant” a fin or a rig, the balance of the boat shifts. And when this happens you have a boat with overwhelming helm problems. Weight, placement and sizes of appendages and drag are critical. Also the systems and the operator have to be able to respond to model boat wind sized shifts and courses. Its why designing these kind of radical systems are very easy in theory and very difficult in practice. Results from actually sailing r/c boats will be very interesting when they appear.

As to Volvo type raceboats, someone in Central Park has built a beautiful replica of a current open 60 type boat with twin rudders and thin ballast strut etc. As a scale model it looks great, as an r/c raceboat its terrible. Too much drag from the hull and twin rudders. Remember the “real” boats are built for long distance ocean racing where you can stay on a single tack for days at a time.

In reality, a canting mast boat using twin asymetrical daggerboards and twin angled rudders(or Hal Robinson’s and others vertical rudder) or a canting keel boat using any number of solutions to makeup for the loss of lateral resistence can be designed with very little to no unwanted balance changes.
However, either boat WITHOUT some form of additional lateral resitence can have tremendous balance problems especially canting masts being used in classes that prohibit the use of daggerboards like the US One Meter and Marblehead.
As to canting keels working in the rc environment speed wise against fixed keel boats: the same computer technology that was used to predict the performance of the Volvo 70 has been used by Graham Bantock to show that his new Formula 100 One Meter is MUCH FASTER than either fixed keel F100’s or IOM’s around several different types of rc course.
Properly designed canting keel boats especially CBTF boats have ZERO balance problems. I’ve had the priveledge to have sailed my aeroSKIFF design for hours using a canting keel and daggerboard(with hydrofoils) and it was perfectly balanced : balance is a matter of design on canting keel and canting
mast boats just like it is on any boat. However, many rc class rules prevent designers from using some of the tools used in fullsize boats to optimize these systems :daggerboards and or twin fore and aft rudders.
More and more rc versions of boats using canting keels will be seen since one of the Worlds best high performance rc sailboat manufacturers Wind Warrior has introduced the Ultimate Warrior ,a canting keel/daggerboard raceboat and microSAIL! is awaiting the final plans to begin the Formula 100 CBTF One Meter racing machine from Graham Bantock.Additionally, there are individuals all over building their own versions of some of these systems…

Doug Lord
High Technology Sailing/Racing


Yes, you and I have chatted about the limitiations of a canting rig before. Canting keels are preferred but the “established classes” do not allow that. I was pointing out that there are ways to get some of the advantages of a canting keel system while working within those rules by using a canting mast instead.

Indeed, the additional loss associated with wetted surface area of the wings on the keel downwind would take away some of the advnatage of the extra righting moment upwind. A comprimise I think can be found with high aspect ratio cambered wings. With a cambered wing you get more lift for a given surface area. So you could minimize the extra surface area while maintaining a lot of lateral resistance upwind. The key would be in setting the angle of attack right to also minimize the induced drag downwind.

While this would still be sub-optimal compared to a proper CBTF system, I would certainly be an advatage compared to fixed rig US1Ms, IMHO.


Have you looked into gyros? some of the aircraft Gyros have some really sophisticated damping and rate properties that may get you out of the hunting problem. Also, you could set a “bucket” of say 10 or 20 degrees in the middle of the range where it would try to control the keel. If you heel outside of this range, then it forces the keel all the way to one side or the other. This would mean that for upwind work, the gyro would be commanding full keel deflection to one side or the other depending on which tack you were on and the gyro would not deviate from that commanded keel deflection unless the boat returned to neutral heel.

Just some thoughts. I would be interested to see how it worked anyway…


Yes, you are right that the balance equation is dramatically different when you are sailing with your rig upright versus at a heel. This needs to be accounted for in designing the boat.

boats normally want to head up more as they heel over. This is because the center of drive in the sails moves abeam (to leeward) of the center of drag resistance of the hull. This generates a moment that causes the boat to want to head up. This is why boats generate windward helm as they heel. In some boats, this can cause control problems in gusty winds as the boat will tend to snap to weather when blasted with a puff.

With a canting rig system, the equations get a little different. But if you have your rig fully canted (i.e. you are not adjusting the cant as you sail), then the response to a puff will be similar to a fixed rig boat. The difference is that the canting rig will remain more upright in the puff (because of the extra righting moment of the keel) and therefore need a more extreme puff to get to the “snap” weather helm point.

One of the problems as a designer of canting rig systems is that your mast canting system must support the rig (unstayed). Therefore, it needs to be pretty beefy and that usually menas that it need to be attached to a bulkhead. That limits the amount of adjustment you can make to the fore/aft position of the rig. (you cannot have 3 or 4 positions on the mast step). Therefore, care must be taken in selecting the position of that bulkhead so that you end up with a well balanced boat in all wind conditions.

For my prototype boat, I plan to build a set of blocks into each side of the boat with a set of threaded holes. My mast bulkhead will have a bracket that will allow me to screw the bulkhead into these blocks on either side. This will allow me to move the bulkhead fore and aft as I experiment with the correct position for the base of the mast to give me optimal balance.

If I design the system correctly, I may be able to also rake my rig fore and aft with forestay and backstay tension to fine tune my balance in the finished boat. The key is to place all critical attachment points (jib pivot, mast pivot, sheet fairleeds and backstay attachment point) along a single axis. That way the rig can cant from side to side about that axis without changing any of the tensions in the rig or the sheeting angles of the sails.

Bottom line is that I think the balance issues can be dealt with. You may just end up at a slightly different mast position to get to that optimal balance. I don’t see that the change in balance as the boat heels will be any worse than a standard boat, and may in fact be better.

  • Will

Will Gorgen

Will–E-mail my friend Dario at Carbonic Boats in Australia and ask him about his canting rig boat and the helm problems he had. His belief(as conveyed to me) was that in order to make the boat work you had to design a system to shift the rig both back and forth and side to side. Just shifting sideways caused the major helm problems I talked about.

As to bulb wings, my full size AC Cup friends tell me that the critical issue is the angle of the wings. If improperly set the wings will be nothing but drag. They also suggest, unfortunately, that in r/c boats the change in angle between benefit and drag is so small (and yet so critical) that they have trouble being able to model the design to even come up with a suggested proper wing angle. It might be why to date no one has found wings “fast” on a model r/c racing yacht.

Finally, as to the fact that balance shifts in canting keel boats can be dealt with by daggerboards and twin rudders, as I pointed out in my initial post here, those solutions make the weight of the boat, and the shape, drag and placement of the appendages and the operation of the systems critical. Its again why the proof is in the real world execution of a concept not claimed theoritical advantages or computer predictions.

Roy, ask your friend Dario how he made up for the loss of effectiveness of the keel fin as the mast canted; without some form of additional area(over that required for optimum upwind performance with a fixed rig) windward performance would have to suffer depending on the cant angle of the rig. Canting keels can allow a boat to sail relatively vertically(at an optimum angle of heel) while develoing righting moment with cant angles as high as 55 degrees each side…
------------------------------ The modern science of yacht design places much reliance on the validity of computer aided design programs and VPP’s such as the one created by the Wolfson unit. In fact millions of dollars are invested as a direct result of the findings of these design tools. I’m not investing that much in the F100 CBTF but when Graham Bantock with assistance from the Wolfson unit tells me that a Formula 100 CBTF boat will be faster around any model racing course than any other fixed keel One Meter then I believe him…
------------------------------ The wings discussed by Will are not an optimum solution to the problem of loss of lateral resistance due to the use of a canting keel or mast mainly because they are still there when you don’t need them.BUT they are the ONLY solution that is (apparently) legal in the US One Meter Class and certainly worth investigating. They are ENTIRELY different than the bulb wings used on IACC boats and are there for an completely(mostly) different purpose: to develop lateral resistence.
However, I agree that to make them work in such a way that they won’t hurt you too much when you don’t need them is a very difficult design job. One full size boat is using such wings for this specific purpose: see “New Canting Keel Solution” under “Technical Discussions” on this forum.

Doug Lord
High Technology Sailing/Racing

A canting keel allows a boat to sail at an OPTIMUM angle of heel; that angle could vary from design to design.Developing extra lateral resistance with a slab sided hull COULD happen and does on a Lightning, Windmill, Snipe and no doubt others but compared to a modern hull design probably is not a good idea since the lateral resistence could be much more eficiently developed with a high aspect board.And by using a different hull shape with a narrow low resistance hull -speed would be greater.
The design of the ML-5 singlehanded keel boat is utilizing a canting keel specifically to replace a person on a trapeze and the boat is being designed to plane in relatively light conditions
using a hull shape similar to a 505,Dutchman and Melges 24…

Doug Lord
High Technology Sailing/Racing

Well, I have not heard back from Dario yet. I have studied his design details listed on the carbonic website and I think the problems he is having relate to lack of lateral resistance. When the mast is canted to windward, the hull heels to an extreme angle. This swings the keel out to windward and accomplishes the goal of increasing the righting moment of the boat. When the keel is heeled over to this extreme angle it looses its ability to generate lateral resistance. Dario recognized this for the rudder and incorporated a canting system for his rudder to keep it relatively vertical as the boat heels over. However, there is no such relief for the keel.

The Marblehead class allows for a second rudder. So Phie (The name of Dario’s boat) should probably be designed with a seeond rudder or centerboard forward of the keel which cants in the same way as the aft rudder.

Another option (in my opinion) is to add wings to the keel. The angle of the wings would be set to a neutral angle for downwind. when the boat was heeled over, the wings would be close to vertical and would be able to generate lateral resistance. This is a fundamentally different function for the wings than what the IACC guys use wings for (and what the AC class guys tried to replicate).

On full sized, fixed keel boats, the wings function to reduce the induced drag. There is a fairly significant performance advantage to this because the aspect ratio of a full sized boat’s keel is quite low, so the induced drag is quite high. On model yachts, we sail with much higher aspect ratio keels (deeper and more slender) so the induced drag of RC keels is much less than on full sized boats. So the benefit of wings would be small and would easily be outweighed by the extra wetted surface area (RC boats sail at much lower Reynolds numbers so viscous drag is a much bigger concern).

However, My idea is not to use the wings to reduce induced drag, but rather to use the wings to generate lateral resistance when the keel is canted way off to the side. While I will pay a penalty in extra wetted surface area, I feel that this penalty is more than offset by being able to generate lateral resistance upwind.

The wings could be quite small and slender. At low wind speeds, the mast would be canted by only a small amount so the keel would be able to generate most of the lateral resistance without the wings. At higher wind speeds, the mast would be canted more resulting int he keel loosing its effectiveness. This would be the regime where the wings kick in. but since the boat would be generating a decent hull speed at this point, small and slender wings would be quite effective.

I’ve been told that there is a full sized boat in the works that incorporates wings on the keel to solve this same problem. I have not seen the design myself, but it was written up in some yacht design rag down under.

Just to bring this conversation full circle, it will be interesting to see what the VO 70s come up with for appendages. The new rule allows for a lot of options. The only restriction is that each appendage can either rotate or retrace, but not both. I would think that most of these guys will start off with a CBTF design, but will quickly begin to evaluate ofther options such as retractable asymmetric daggerboards, twin rudders, etc. It will be interesting to see if anyone decides that wings on the keel are a good way to balance lateral resistance with wetted surface.

BTW, Sailing World had a nice writeup on the VO 70 rule. They talked a lot about the ability of the boat to recover from braoches and capsizes. Most broaches the last time around were caused when the boat would bury the bow in a wave and head down uncontrollably. This would lead to an unplanned gybe and the mainsail would get pinned on the centerline by the running backstays. Then the boat would lay down on its side until it spun into the wind or someone released the runner. There is a great photo sequence here: (Note the mainsail pinned by the runner in picture #2). Imagine what a braoch like that would be like with even more sail area and the keel canted to the wrong side. Scary!!!

Will Gorgen

All this talking about canting keels got me thinking about the Idea of a shunting proa with keel instead of outrigger. The keel could swing between straight down, and only one of the two sides. You could have a rudder at each end , and a swing rig without a mainsail that would bring the center of effort over each “Rudder” on each tack. The advantage would be that the keel would only have to move half the number of degrees of that of a conventional canting keel, but with the same speed advantage. You could even make the keel permanently fixed to one side. No fancy mechanism!! just a wing mast which would keep its shape in light air when drooping to one side.

I’ve thought about the Idea for years . Maybe I should get around to trying it