10 Rater Design Parameters

[:-pirate]The 10 Rater class is IMHO the Formula One of the model yacht world.[:-turtle]
With a very open class rule which encourages development and experimentation.
Some of those decisions made as to waterline length and consequently sail area are influenced by your own sailing conditions.
Personally living in Wellington, New Zealand, which is rated the second windiest capital city in the world, where most days it blows over 10 knots, I would go for a longer waterline and less sail area.
Model yacht maximum speed is directly related to LWL (load waterline length)
Longer equals faster. Provided you can get up to maximum hull speed.
If there is insufficent sail area (SA) to provide power to reach hull speed then you simply have to wait for more wind.
I will not even broach the subject of planing as that is another can of worms.
I have more to come but as my typing is so slow I will have to come back later.[:-weepn]

Do it NOW before it`s too late.

<font size=“3”>Part Two</font id=“size3”>[:-idea]
We have chosen our LWL/SA ratio so now comes the RIG design.
Conventional or Una (one sail)?
A round tapered carbon mast or balsa and foam cored vac bagged wing mast.
With how many shrouds, or perhaps shroudless, maybe a swing rig would allow quick changes.
How many channels for control?
Just two or go the whole hog and use six channels and be able to tweek everything.
Foils, how many, what shape, what length.
Hull shape, now here`s a big question, skinny and fast or fat and stable, perhaps somewere in between, but favouring which end of the extreme.
As you can understand a development class has the ability to make the most amazing leaps forward and to create the biggest flops in design you could imagine.
My best advise would be to choose an established design build and sail it for as long as it takes to become good at sailing and tuning before any attempt is made to solve the puzzle that is the 10 Rater class. [:-jester]

Do it NOW before it`s too late.

Giddaye Ian

I’ve recently finished building a 10 Rater. I’ve sailed IOM’s for years and the buzz you get out of the 10 Rater is fantastic. The current boat is mark 3. The previous 2 very unsuccessful. The first boat I built in balsa and glass to my own design and miscalculated the displacement so consequently had to long a waterline. The second ,I used the first hull as a plug. I bulked up the bilges and carried the rocker out to the ends more to up the displacement. It worked but I stuffed up by attemting to build the hull in light glass layup. the hull was to soft. The 3rd one is in carbon and is great.
I note you are considering hull shapes. I have found there can be light years of performance gains in the foils. I recently fitted a Jeff Byrley keel to my boat and the performance gains were like ‘night and day’.

One of the guys at the my club has just built a IOMA off the AMYA web site and its a pretty good boat out of the box. You might want to consider this. It has quite a heavy weight keel, something around 4 kgs. If you want light airs performance you could reduce the weight to around 3.2 kgs and have more sail area.

Here is an unusual 10R design decision: my 10R sails were made by Bob Sterne, who also manufactured the Viper Marblehead hull. In his wisdom, Bob did not elect to use the maximum sail area that was available to him under the 10R formula. The sails measure to about 1250 square inches, maybe a couple of hundred square inches shy of the max for a Marble-Rater.

Perhaps he reasoned that these boats are so wildly overpowered anyway, why add sail area if you are just going to end up spilling wind or rigging down to keep the boat under control.

In any event, it was an excellent design decision. The boat is easy and fast and you don’t have to add technical features (servo vang, for example) to spill wind or de-power the rig.

Maybe the lesson is, the 10R is an optimization problem, not a maximization problem. The surprisingly successful design solutions may be over on the conservative side.

On the other hand, a Carbon 10! Wow, congratulations TF!

We used to sail 10Rs for years until we ran into the problem that is inherent in the class rules.

Simply put, the rule rewards condition specific boats–if you sail in light air you build a minimum lenght, maximum sail area boat and you win. If you sail in heavy air, you build a long, stable boat with less sail area and you win.

Building to condtions works if you stay in a single location with one predominant wind. But the minute you travel to another site, the problems begin. Take a “long” boat to a light air race and its virtually impossible to get out of the back of the fleet. Take a light boat to someplace where the wind “howls” all the time and you’ll struggle to get around the course. Some people have even tried short waterline boats with long overhangs to try to get around the problem, in the end however no one has been able to master the design problem to make such boats perfom up to their theoritical potential.

In the end the 10R class drives you to realize that to be successful all around you need three boats, one each for light, medium and heavy air.

The theoretical potential you mention is what makes the 10 rater so exciting. That is the challenge, not available in any other class of rc yacht. You say you need to have three boats for all conditions, what a load of codswollop. Haven’t you heard of different size rigs. To try to design a 10 rater or any yacht to perform to its full potential in all wind conditions with one rig would be a disaster as far as I’m concerned.

As to the original post,I beleive that a hull with long overhangs is acheivable, and is a far better option than trying the short 10 raters that seem to be popular in the US and England. My boat has 1.140 waterline with an overall hull length of 1.500 metres. This is a reasonably short waterline-large sail area scenario but when the wind kicks in, all that happens is a smaller rig is fitted.

1996 was the last year we scheduled races for 10-raters in Central Park. We raced 10 Raters every other Saturday. Two of these boats were ?real tens? with long waterlines (Andy Buday and Noel McIntosh).

The rest of the field, which was a large one, consisted of converted Marbleheads. The conversion step was very easy because the M-boats were, with a single exception, swing rigged. You could just unplug the M swing rig and plug-in the 10R swing rig.

In that last season the swing-rigged 10 Raters were sailed by Elmahleh, Langbord, Estavez, Goodrich, Richard Shapiro, maybe Tucker. Okinow. Maybe David (forgot his last name, he was the chef at the Astoria, and he drove a Pinter). There were probably some others. It was a big field.

All of the swing-rigged Tens were defeated in that season. They were occasionally defeated by Jon Elmahleh, sailing his M ? as an M, with an M rig ? in the 10R races.

The 10R champion for that year was Bill Priest, who was sailing Herman Rau?s Rover, an early Kevlar M-hull from California. The Rover was designed with a curious flat spot on the bottom, not quite a chine hull. The Rover was conventionally rigged, with a beautifully engineered backstay servo control to de-power the rig. It was the single conventionally rigged Marble Rater. It was essentially an antique. And it won.

So what was the take home lesson?

Swing rigs shift a lot of sail area up high, and the top of the sail is, in effect, buttressed against spilling wind by the radical curve of the mast. IMHO this is why swing rigs are superior to conventional rigs in light air racing. They put substantial sail area up where the wind is, and they support it.

But when you construct a swing-rigged 10R, that helpful extra sail area on high becomes too much of a good thing. Marbleheads with swing rigs are notorious for their nosedives in wind higher than 7 or 8 mph. When you add 50 percent more sail area, to create a swing-rigged 10R, you?ve got yourself a submarine.

Watching those races in the spring and fall of 1996, when the wind was up, was like watching a family of ducks at supper. When a gust would hit, voila, complete and utter chaos, nosediving, rudders-up, lots of yelling and screaming.

Except of course for the winner, the conventionally rigged Rover. Smiling through. I think he won it because he was able to keep going ? which is to say, keep his rudder in the water – in all conditions.

Right now, there are a lot high tech Marblehead hulls sitting on mantles and in basements and garages. They are deeply undervalued assets ? fast and very fast hulls, just sitting. And for sale cheap. It is a bizarre situation.

If you set out to experiment with 10R designs, it would be a huge shortcut to pick up an M-boat hull, some of which weigh less than a pound, and rig it as a 10R. It is easier to build a rig and a bulb than whole boat.

But my point is, if you choose to experiment in this direction, use a conventional rig. I think what we learned from racing 10Rs in the 1990s was that swing-rigged Tens are unmanageable monstrosities. Analogous to V-8 engines installed in baby carriages.


ok this is coming from a IOM sailor. been that way for the last 20 years . and yes i am that old
I saw a couple of 10r on the pond and liked what i saw. but like roy said. they were different. and each acted different. but you saw nobody arguing . about the weather. maybe it is because we are canadian. but it got me thinking( bad idea) i might like to have one. now I think what we have here is a very good comparision between model boats and the real thing. look at the americas cup boats. they are design for a certian wind conditions. yet noboy is complaining there. they sail though it. using thier skill. anybody can sail a fast boat. but the good sailors can sail a brick fast

what is the most important factor i should consider if i decided to design my own 10r. i sail in puffy air and a little chop. I also am not afriad to put my boats into lake ontario. so I would assume a longer waterline?
is there any where i can get a set a drawing to look at ? maybe online?

long live the cup and cris dickson

Roy nailed it… the wording could have been a little different to “soften the blow” but his facts are spot on. The thing that makes the 10R fun is the thing that makes it NOT fun.

TF, if you think is not the case, well… time will tell. I have 2 10r’s one of which was the British National Champ 20+ years ago, and a Bantock Marblehead with a swing-rig “A” and conventional “B”, so I can testify to what Michael was saying. (I almost blew Dr Pepper all over the key board at the “Ducks at Dinner” analogy… most excellent…) I have seen my M go down to periscope depth more than once (the hull completely submerged with on the the mast and the faithful antenna still above… and I PASSED a Victoria while submerged as it was STILL hauling ass)

I would restate what Roy was saying in that… if you are out of the envelope on the boat of choice for the conditions, it makes for a very long day. I beat 10R’s with EC-12’s and J boats (which are SO much faster than they look) in very light air… and you can hear their skippers teeth nashing 50’ away as they offer ANYTHING to the wind gods for only one decent puff. In heavy air, AC-15’s run off and leave the medium boats, the light air boats have already gone home, and the long hull high aspect ratio 10R’s are at their best… STILL lose because the AC-15 is about 11.5 on the same rating.

It is truly a “King for a Day” boat… when you are in the right place at the right time you can run the table, and when you are not… well… there is nothing much you can do about it…

The idea of changing rigs is great… except that you can’t change the hull length to go along with it. You can go from not having a chance, to just getting beaten everytime, but if the conditions don’t change, neither will your finishes. An overpowered M is just as useless as an underpowered 10R. We have a Bantock 10R here and it is exactly in the middle of the length/sail envelope. Consequently it is always good, but never great, except for the exact wind conditions that are in the middle as well, then it is exactly where it needs to be.

Roy said 3 boats, and I totally agree. Goofy as it sounds, why not make a telescoping hull… heheheh it could be done. I have never seen a rule that said it was illegal to adjust your hull length by R/C.[}}:-|>>]


If nothing else I have inspired comment.

Yep, you guys are all correct, the 10 rater can be a bitch of a thing at times, however I say again they are the greatest buzz I have had in rc sailing. When they are in the groove they are great!

The comments ln swing rigs are spot on. While never sailing with one I would suggest that most of the hotshot “M” sailors in Australia have discarded swing for conventional rigs.

Download Attachment: [ RAYS10RA.JPG](http://www.rcsailing.net/forum1/data/Larry Ludwig/20056602825_RAYS10RA.JPG)

TF… here you go man… enjoy… this was taken about 8 hours ago.


freakin heh. now that boat is just moving . wow and looks good too. hopefully my iacc20 boat will look that way. what design is your 10 r. . it looks balanced in a good breeze. making me jealous. wish the americas cup boats would look like that

long live the cup and cris dickson

Hi, I have read the last few postings with intrest, I have been playing with a 10R for some time and after a few slow boats finally found a boat that will go. My boat has the long overhangs and the slik appearance of most 10,s. To be able to gain the most from the rule I found that I had to use carbon fibre and be very light in the bulid up, so measure everything. This gave me a strong boat that dos,nt leak at all and weights in at 5.2kg ready to sail. I can beat the marbelheads in all conditions !!! including a Waliki with a 10R rig. The boat has stay less rigs, five different rig combinations and four keels and rudders that have been optimised for the prevailing conditions.I have found that those who have come from the IOM or marbelhaed sailing seem to think within the box, to get a 10R to go the answer is out side the box, very much like the New Zealand cup ( America,s Cup ).Sorry I hav,nt posted a picture, but will as soon as I have one .

The 10R belongs to Ray Seta here in SAT, my 10R is up in the rafters… maybe I can get it down one of these days, but it sounds to be more akin to what coorong is describing. Ray’s boat is a Bantock built boat (yes by the man himself) and has virtually no overhang what so ever. Mine has quite a bit of it and is susbsequently much longer than the Bantock, but it would get murdered in light air. [:-banghead]


Hi, I sailed my 10r at the weekend in less than 4 knots, glass conditions , the marbelhead in the fleet used a swing rig, it was only my missing the bits of breeze that allowed him to get away, in the end I won 6 of the 8 races. I guess my point is, I think you need to look a why, how and then act for those conditions.I use very light sails, a light boat and soft hands on the controls. I am not an expert but, I don,t accept that I will get beaten in those conditions so I have looked at every aspect of the boat so as to perform.
I like the America,s cup thought…if you consider the time and effort that goes into those boats maybe we should as well, if we so desire.

Was the M carrying 800 sq in for its class? If so you were just racing a M. That is just about half of the sail area allowed a boat that short (1500 sq in) I don’t doubt for a moment that you beat that boat every time.

I have never seen a 1500 sq in swing rig for a M before, that would be impressive.

I know that I only have to put on about 1200 sq in on my Bantock Strad, and in < 6kts of breeze no one will even put a 10R on the water it would be so unfair.

My EC-12’s walk off and hide from a 10R in wind that light, and the J boats will lap them on a single course.


Hi, I agree with some of what you say,we have treid alot of things with swing rigs and different ways of making the boats go, not all race rule legal,but, I would still think that the 10R needs the same effort put into it as the RM. I think the class has alot of uptaped potential. I have never seen a J in the flesh but have always admired the boats in picures…maybe the next project…any advice on what to look at?

No, sort of like picking an ice cream flavor, they are almost all good.

Ranger, Rainbow, Endeavour (I&II) are the long hulls around 101", Shamrock V, Enterprise, Whirlwind are the shorter boats. (around 90")

Whirlwind is the stepchild because it was built on a different scale. All the others are 1/16th. I have never seen a 1/16th Whirlwind. Weetamoe is another unusual boat that you won’t hardly find examples… although there are a few.

Those are the most common, they are cumbersome to move around, but when you sail one you are the boat that everyone watches. I will tell you that they will spoil you, and soon you will compare everything else you sail to that boat.

I sail almost every class of boat out there, and if there were only one, I would take the J boat for sheer enjoyment.

They are deceptively fast, in that most people become accustomed to watching smaller boats and your eye becomes trained by the motion. When you see a J boat on the water they just don’t appear to be moving that fast… and it is because of the size… much the same way a large aircraft appears to be much slower than all the others when it is most certainly going every bit as fast.

Most definitely light air boats, above 10 kts of wind, they are more than a handful, and you will need to start going to smaller set of sails soon. They sail just the same as a real keel boat does… you have to be much sharper on accelerating the boat after a tack and gaining hull speed before you can do anything else.

A Marblehead can tack 2 times in the time it takes a J to tack once. They are the masters of light air though… when that same marblehead is bobbing like a cork, the J will have a nice wake and just cruise right past it.

I took a friend out with me a month ago when it was only about 5 kts of wind and I was sailing a Shamrock. He thought I was nuts for putting it in the water… there isn’t enough wind for that 85 lb boat to move. He was thinking only of the weight and not of the 4000 sq in of sail.

He had a Victoria and the wake from Shamrock almost swamped him. [:-batman]

They are also more prone to mechanical breakdown than other boats… but I think this is true because they don’t get sailed as often. It is something of an event to get them out. I have to move mine around with a trailer. So most of the time when I do get a break to go sail… it is so much easier to grab something small like a Santa Barbara or an EC-12 and just throw it in the back and go. If I had a club where I could keep my boat at the water, or lived on a pond it would be different… but it takes at least two people to get them in and out of the water and you don’t always have someone else handy. Leaning over with that much weight to launch off of a dock is not an easy thing to do either. Boat ramps and a dolly will help you live longer.

Expensive, hard to move around, launch and recover… but worth all of the trouble.


Hi, Thanks for the info, the romantic in me is inspired but the realist suggests I hold off. I have an intrest in 10R,s and RM boats. Mainly as these are the international racing classes and in my veiw are the boats that produce some amazing performances when sailing.
My project at present is to get my 10R up to speed for our state championships and if happy with that go to the nationals with it.
I have a couple of RM sailors that are more than happy to help with this as it helps them to tune up as well, we often match race or use a second start at the back of the main bunch to do this.
I would be intrested to hear how others had tuned up their 10R,s.Has anyone re looked at the wing mast idea?

Mr. Francis, a retired aerospace engineer (Seattle Area), wrote an article in “Model Builder Magazine” in the early 90’s about his experience in building a wingsail for a remote controlled model sailboat. That was in the 50’s when techies dominated. I met him and he allowed me to photocopy his works documenting the design, building, wind tunnel testing and competition notes. He is the most organized man I ever met (Visited his house and workshop by a lake (Snohomish?) in Redmond, WA, where none of his models (aircraft, boats, construction crane) is from a kit). I will dig up my materials (they may not be of much value in today’s high-tech sails and “low-Reynolds number” airfoils) and hopefully send you a copy. Best contact, that I know of, is Mr. Rod Carr of Carr Sails.

I came across a related article in Marine Modeling Magazine in the late 90’s/early 2000.

I will follow your 10R development. While, I believe 10R is an elegant boat, the challenges seem frustrating to the very many. Good luck to you.

Del Perena