Bill
When will we see these boats? I am looking a F18 and would like more US built boats to chose from. How about an F20 to compete against the I20. You seem to like this boat for having flat decks. It's time to built one and show them on the water.
LF

Larry,
The SC20 came out in 1978. This was a 20ft by 12ft by 276ftft of sail. It had a DPN of 62 back in the early 80s. Add a spinnaker and it is 59.5.
Today there are new boats with the same sail area that are 8.5ft wide and require two big guys to hold'em down when the wind blows over 12 knots. The SC20 with its 12ft beam made it possible for two average size sailors, a guy and his girl friend, to sail competitively in 15 to 20 knots of wind. It takes a given amount of righting moment to drive 270 to 290ftft of sail area efficiently. You can get this torque with two big people on a short lever arm or with two average size people and a long lever arm. The choice is yours.
There was a light air version of this boat called the SC20TR, tall rig. It had about 325ftft of sail area with a 38ft tall mast. This boat developed a DPN of 60 without spin. Add a spin and you get a DPN of 57.5. Today the ARC22 has a DPN of 57.3. So, Larry, what's new??? Where's the new technology? Where are the breakthroughs? All I can see is that boats are lighter weight today because of improved materials properties. That is not improved boat design. Spinnakers have been added. Spinnakers have been around for 50 to 75 years or more. That is nothing new. Boats with unirigs and spinnakers are sailboats/sailplans tailored to the windward leeward race course. Go back to the triangle race course and the sloop rig with spinnaker is faster. Larry, I'm having a hard time finding any real, true, pure improved boat design. What do you want to see????

As far as an 18 footer goes: Take a SC19 and move the transom forward 1ft. This was done with much success years ago in the 18 sq class.The boat had a higher top speed than other 18sqs and it was much harder to pitchpole. If you want it, it was there 18 years ago. Where were you?
Good Sailing,
Bill

There seems to be quite a bit of nostalgia surrounding the Bill Roberts designs as of late. Are these folks looking back because nothing really astounding has come forward in the past year or two? The entire F18HT landslide of hype has resulted in some great boats, but no revolution. I-20s, N-6.0NAs, and P-19s have been around for quite a while and have proven to be fast and fun-but where is the quantum leap we have become addicted to? Have we reached the paragon or close to it without going to wingsails and asemetric hull layouts that only can go on one tack? What I am reading in these posts is sailors are looking for a challenging experience and have minds that are not going to rest when it comes to asking "what if?" If we can't beat them with computer design and carbon fiber, we will beat them with an Aqua Cat 12 and a jet engine.

The question should be...when is ARC going to reintroduce the SC 17, 19 and 20...and the answer probably is when sailors start looking for a rugged all a round performance boat that is just as at home in the ocean with the family on it as it is on a flat water lake/river/bay race course.

Now it seems many cats are bought because they are the flavor of the week, or everyone else has one, so if you want to race one design, you have to get one too.

If the catamaran comunity ever expands again to include those people that just want to have fun, then we will not need the competitive aspect driving every design decision.
At that time, designers like Bill will be recognized for designing the best boats without worrying that its a foot or two too long or too wide according to some arbitrary rule book.

The SC 17 I use to have brought me more pleasure than any boat I ever owned..the Humvee of the sea...Too bad Tom stoped building them...may be some day, some one could/would buy the molds and put them back into production...Thanks Bill! for designing awesome boats for the real world...

Bob

Well now Bill, you ask :

"So, Larry, what's new??? Where's the new technology? Where are the breakthroughs?"

Two give three examples :

Squaretop mainssails
a 20 footer weighting in a 115 kg = 254 lbs (m20)
reproductivety of hulls within 400 grams (1 lbs) or less when using prepreg materials.

May not be breakthroughs in the purest sense of the word but significant advancements just the same. You yourself just quoted the development in the Tornado class in a recent class where a wobbly boat of 450 lbs was transformed into a very stuff 375 lbs boat with a long competitive life.

That is all new and one couldn't do these tricks 20 years ago simply because the technics either didn't exist back then or were still far to expensive to be used in anything other than space flight.

Than we have the introduction of the Flyer hullshape (the original shape, not the copies) which pretty much took the A-cat class by storm. In the late 80's early 90's the a-cats went down from 100 kg's to 50 kg's overall weight. Now the min weight is fixed at 75 kg but they can be build lighter.

I can't remember but when was the prebend rig developped in the tornado class which is improved the control of the mainsail and increase the area in which the mainsail could be trimmed to it's optimal shape. I think it was done in the 80's and perfected later.

I've heard people say that ARC designs can be summarized by "stack more sailarea on it than others do and go faster". What have we seen in the last 20 years ? We've seen smaller boats with limits on sailarea go faster and faster and equalling the ARC design but innovation and advancements in catamaran design. To get more out of less is called progress, just like how modern race car are faster than their banned 80's turbo charged predecessors despite the fact they don't use turbo's anymore.

Then you indicate that :"Spinnakers have been around for 50 to 75 years or more"

Yes, but the asymmetric spis on cats are cut complete different from the symmetric spinnakers of 50 years ago. Your statement is analogue to saying that nothing new was devellopped over the last 3000 years as catamarans still use soft sails to propel them forward. In that respect a ARC is nothing more than a pre christianity polynesian proa made out of fibre glass.

I for one would like to see someone cut the transom of a SC19, put a rig of 21,15 sq. mtr. with a 80's cut (pin head) on it together with a spi that is cut like the ones of 50-75 years ago and do well against modern F18's in the F18 world cup.

I think we all know where this boat will end up and that proofs that there really has been improvements, developments and innovations over time. The may have been spread ou over a longer period of time and therefor can't be really described as breakthroughs but a modern cat is certainly not more of the same old 80's technology.

Maybe extending the transom of a SC17 to 18 foot would be a better comparison to todays F18's ; Weight and rigarea's are far more alike.

Wouter

Wouter,
These lighter weight boats are not a technical breakthrough for beach cats. Prepreg construction and the autoclave were used to make spaceship parts and airplane parts and race car parts long before they were used to make beach cat parts. As a matter of fact I have been told that Marstrom built glider parts long before he built beach cat parts. The use of prepreg materials and the autoclave in beach cat construction is not an invention. You cannot get a patent on it. It is a construction method improvement but it is not a technology breakthrough.
Square top mainsails: Nothing new! If you look in an aerodynamics text book, Aero 101, you will find a section that deals with wing spanwise efficiency. There will be a curve of wing span efficiency or effectiveness vs wing taper ratio. You will see that the wing shape that looses the most span effectiveness is the wing that comes to a point at the outboard end. As the wing tip chord approaches about 25% of the root chord, the wing spanwise effectiveness rises rapidly into the low 90% effectiveness
range and then the curve levels off with further increases in tip chord to root chord ratio. When the tip chord to root chord reaches a value of 1.0, the spanwise effectiveness begins to fall off again because of the large tip vortex caused by the wide wing tip chord. I had a mainsail on my SC20 with a 2ft wide tip chord in 1978. My first RC27 in 1983 had a square top mainsail. When was the first time you saw a square top mainsail? Did you notice that today even the Americas Cup boats are using square top mainsails? These so called "hi tech" boats are following the lead of the beach cats with higher fineness ratio hulls and high aspect ratio sailplans and keels. Today these boats require 20ft of water to keep from dragging their keels on the bottom.
Prebent Rig: Again this was a standard item on the early RC27s. As soon as I began experimenting spinnakers, 1983, I ran into the mast inverting problem. Sweeeping the spreaders aft of the mast 4 to 5 inches created two tall slendar triangles of fore and aft mast support which pushed forward on the central height of the mast and prevented mast inversion. The first spinnakers I put up showed NO improvement in boatspeed and no change in downwind sailing angle. The spinnaker filled and the mainsail became totally ineffective; no net change. It wasn't until the late 1980s that spinnakers began to work to advantage on the RC boats and that was after the purchase of several spinnakers from several different sailmakers.
On the ARC boats you and others have missed the whole point. To go faster a sailboat must have a higher sail area to weight ratio. There are two ways to get there. One is add more sail area. This is inexpensive. The other way is to reduce weight. The Tornado is an example of this. An Olympic Tornado costs almost twice as much as any other 20ft beach cat. Which way do you think the sailing public would rather go? The other very important point that goes untalked about is boat width. To be faster than other boats a superior design must have a higher righting moment to sail area ratio also. Without this parameter being superior to other designs, the higher sail area to weight ratio cannot be taken advantage of. Also the narrow boats with high sail to weight ratio area drive the competitive sailors weight to larger people. The SC and ARC products are unique here. These designs offer the 12ft beam which lets leverage do the work of generating more righting moment rather than requiring a larger weight person. Why do you think the Tornado is 10ft wide and always has been? It is not just because the designer thought it looked pretty. It has a very functional purpose. Nobody is going to build a boat faster than the Tornado until it has a higher sail area to weight ratio and a higher righting moment to sail area ratio!!!
Bill

Bill, why don't wings serve the same purpose as making the boat wider? Is it because they add too much weight?

I will take a stab at that.

Wings do and do not make the boat effectively wider. The crew weight out like on a wider boat but the weight of the hull and rigging is not. Plus you have the effect of the weight of leeward wing working against you. You also do not have the stability of a wider boat. Wings are more like, having a 2 foot taller crew than a wider boat

Don't get me wrong, I like wing boats. I think their advantage is getting your weight out in a safer and more secure way than trapping. For example, with the skipper planted securely on a wing, an 18 magnum will handle wave conditions nothing else will. A Wave with wings and that long promised Hooter would be fun too.

plus, chicks dig wings :P

(My girlfriend, once again, says that she'd find it very uncomfortable to sail on a cat with no wings)

I've been trying to calculate how high off the water I am when I'm trapping on my wing, and at a decent angle of heel. I've wanted to see how hard it would be to sail by boat without its wings, but I'm to much of a pansy to try it.

I didn't say :"lighter weight boats are a technical breakthrough for beach cats"

And how does "Prepreg construction and the autoclave were used to make spaceship parts and airplane parts and race car parts long before they were used to make beach cat parts" conflict with my statement of "simply because the technics either didn't exist back then or were still far to expensive to be used in anything other than space flight."

The fact that they can be applied now in cat design is progress and advancement.

You keep yepping on about breakthroughs, I didn't as I wrote "They may have been spread out over a longer period of time and therefor can't be really described as breakthroughs but a modern cat is certainly not more of the same old 80's technology"

Then you throw in "The use of prepreg materials and the autoclave in beach cat construction is not an invention" after I called te use of this in cat design an INNOVATION. There is a big difference between invention and innovation, Bill.

And as for "Square top mainsails: Nothing new! If you look in an aerodynamics text book" Both Arvel and Bethwaite have completely debunked the use of aircraft earodynamics to sails. It turns out that soft cloth sails behave totally different from aircraft wings and squaretops are used for different reasons than tip vortexes. And if you really want to now any aerodynamics book will name and eliptical wingtip as the perferred wingdesign when looking at vortexes alone.

This use of aircraft aerodynamics is so 80's, since the beginning of the 90's most advances in catamaran saildesign has come from low speed model gliders competition and the (renewed) study of pre- and underpowered flight experiments. These experiments focus on the seperation bubbles and reattachment zones that are simply NOT found in powered fixed wing airraft studies.

"On the ARC boats you and others have missed the whole point" Did I ? As far as I know ARC boats have not opted for the "expensive low weight tornado" route and just stacked up more sailarea and increased width and are still more expensive than common production boats like the I-20 which, as you know, gives the Tornado a good hurry up around the course. Clearly there are other things at play here too. Besides which boat do you want to trailor behind your care a 12 foot wide one or an 8 foot one ?

And "To be faster than other boats a superior design must have a higher righting moment to sail area ratio also. Without this parameter being superior to other designs, the higher sail area to weight ratio cannot be taken advantage of" is just nonsense Bill. Answer this to me.

What happens when for a given design the ratio between righting moment to sail area DECREASES LESS than the ratio for weight to overall sail area ?

Yes power is decrease by virtue of the first ration but when drag decreases even more than the given design will become faster.

How else can modern A-cats be faster than those of 10 years ago when they had shorter mast and about 25 kg's heavier platform ?

How else can a Taipan 4.9 outperform a H16 IN ALL CONDITIONS when afterall the H16 total sailarea is actually slightly more than that of the Taipan and both are of equal width ? And the Taipan has a taller mast at that. According to your reasoning the Taipan should be held back by her rig that has a worse ratio of righting to sail are than the H16.

I know why the tornado has a 10 ft wide beam and I also know that it is possible to design a faster craft WITHOUT :"a higher sail area to weight ratio and a higher righting moment to sail area ratio!!!"

Eventually it all comes down to improving the power to drag ratio and a designer can ALSO do that by making sure that the ratio of righting moment to sail area reduced less rapidly than the ratio for weight to sail area. And the logical way to do this is to reduce platform weight. Platform weight hardly contributes to the righting moment but does fully contribute to drag.

Example

-1- 150 kg crew on a 2,5 mtr, wide 150 kg's platform weights 300 kg overall and has a righting moment of 150 * 2,5 *0,5 + 150 * (2,5 + 1) = 187,5 + 525 = 712,5 where the distribution is 26 % to 74 %

-2- 150 kg crew on a 2,5 mtr, wide 100 kg's platform weights 250 kg overall and has a righting moment of 100 * 2,5 *0,5 + 150 * (2,5 + 1) = 125 + 525 = 650 where the distribution is 19 % to 81 % %


Boat two has 91 % of the righting moment of boat 2 and can therefor only carry 91 % of the sailarea with only 91 % of the power BUT is also has only 83 % of the weight of boat 1 which is directly translated in reduced drag of alot more than the 9 % of the power reduction. Ergo reduction in power coincides with an even bigger reduction in drag and thus higher speeds are achieved.

There is the counterexample of your "Nobody is going to build a boat faster than the .... (fill any boat that you want) until it has a higher sail area to weight ratio and a higher righting moment to sail area ratio!!!" statement.


Simple not ?

And how does your own statement of "It wasn't until the late 1980s that spinnakers began to work to advantage on the RC boats and that was after the purchase of several spinnakers from several different sailmakers" mix with your earlier statement of "That is not improved boat design. Spinnakers have been added. Spinnakers have been around for 50 to 75 years or more. That is nothing new"

Going by your own statements of your latest post something DID change between your first own experiments with spi in 1983 that failed to produce results and your retries of the late 80's and early 90's. Now I can tell you a whole lot changed between the early 90's worrell like spi's and the newer generation high aspect spi's of late 90 early naughties.

Now I DO share your skeptisme with respect to certain "improved designs" and indeed it is more difficult to design a faster boat than one thinks. Most designers do it wrong. As like with the M20, there the designer reduced overall weight, increased righting moment by having a much taller mast AND decreased the width from 10 to 8,5 ft. at the same time. Mastrom shouldn't have done all three things at the same time. You can do two of these and expect to have at least the same performance or better but doing the third pretty assures that you will do worse under certain conditions.

But I stand with my counter argument to your first post. There has been significant innovation and improvements in catamaran design over the last 20 years and as a result the boats have become faster. Due to the gradual improvements I don't think "breakthroughs" is the right describtion for the advancements. This does not mean however that we're witnessing more of the same 80's stuff.

it is either this or accepting that the only true breakthroughs made in multihull design were made 3000 years ago by polynesian boat builders who discovered the advantages of form stabilized designs over weight stabilized designs and discovered the vastly superior performance of Crab sails in all conditions but pure upwind sailing. After that the introduction of bermuda rigs was only a specialization to race courses that featured a dominant upwind leg.

Because in all honesty what did change since then. We still have have two floater connect together by beams, a mast with a sail made of cloth, a peice of rope to trim the sail and a rudder that is hanging from the stern to steer with.

Regards,

Wouter

Hi Mary,
Wings do add to a boats righting moment to sail area ratio as long as the sailors trapeze off the edge of the wing. Wings that sailors sit on are comfort things only. Wings make boats faster in medium and strong winds when they move the sailor's weight further outboard and away from the leeward hull which is the sailing system's fulcrum point. Higher righting moment to sail area is a powerful go fast device when the wind blows.
Who knows of a 20ft beach cat built in Florida with prepreg materials, a superlight boat, unirig with spinnaker, everyone thought it was going to be a rocketship. It was very fast in light winds, 5 knots. When the winds got up to 10 to 12 knots, other 20ft boats pulled even with it. When the winds got up in the 15 to 20 knot range, the superboat fell behind. What is wrong with this design? What was the mistake, the error, the oversight in this boat's design?
Bill

I haven't seen this much bull since the Democaratic presidential candidates.

1. The original question has been totally ignored by Bill Roberts.
Supercat, SC, ARC, Aquarius Sail has ALWAYS avoided building boats which could be raced against "normal" boats.
They use the "ultimate speed" excuse when asked why they refuse to build A Class or C Class or IF18 or IF20.
They build boats for people who want to BUY "first to finish".

2.Barjack: I don't know what "quantum leaps" you are referring to.
We reached several "Limits" many years ago. Mostly the 8.5' trailer limit.

3.Seeker: There are plenty of boats which meet your requirements from well establish companies with dealer networks and racing programs.
What is so awsome about taking an average design (Supercat 19 -dPN 69.0) and making it wider so it goes faster?
Bill constantly states that the key to "ultimate speed" is the width of the boat.
How fast would an M20 be if it were 12 feet wide?

4.Bill: "Wings do add to a boats righting moment to sail area ratio as long as the sailors trapeze off the edge of the wing. Wings that sailors sit on are comfort things only." NO DUH!! ALL wings are design to be trapped off.
Guess what else? TRAPEZES do add to a boats righting moment to sail area ratio as long as the sailors trapeze off the edge of the HULL.
TRAPEZES that sailors sit IN are comfort things only. Your boats come with trapezes don't they?
Was that comment of yours supposed to be a technical rebuttal?
Why won't you answer the man's question?
Why won't Bill Roberts design and Aquarius build a boat (IF18, F18HT, IF20) that would compete against other makers on even terms?
Why won't you prove your design?

Hello Sam-

You said:" They build boats for people who want to BUY "first to finish".

I was wondering how many ARC/SC22 owners you had personally interviewed/surveyed about why they bought their boat? I personally don't recall speaking to you. As far as racing I could care less about competing against any cat other than a 22' cat. If that means only Roberts designed ARC built boats presently that's fine with me. If you think its worth the $33k I have invested in my ARC22 to beat a slower boat, you over-estimate your importantance!

As far as why doesn't Roberts or Haberman build a particular boat; why don't you go out and buy what's available like the rest of us? Or better yet why don't you and Larry go out and design and build your own boat? Put your own time & money up as well and take the risk that what you end up with will be competitive or not as well as saleable or not to the "New"catamaran buying public.

I heard your whining scenario in the late 1960s/early 1970s when the Tornado was created and was made an Olympic class.

You say "Why won't you prove your design?" I think the question is why won't anyone else build a 22' cat to compete with the SC/ARC22? It was there before either the F18 or F20 I believe. Its been over ten years I believe. Its not like the boat hasn't been seen or heard of.

If you decide to take the risk; keep us advised as to your progress on building a proven designed boat. Include pics as well. Thats if you have the talent, genius, money and guts to do it.

thommerrill
FMS SC20 57
ARC22 2234
F25c 009

I think the "scientific" talk should be left at home. I don't think anyone has designed working airplanes, much less a widely used sailboat or rig. Until that happens, your various theories don't hold a whole lot of clout.

First of all, if you have ever sailed a boat with wings you should know that wings do help. I am not going to argue how efficently they help, but they do help control.

Second, major break throughs will not happen anymore with "beachcats". People like them simple. The vast majority of sailors will not buy new & possibly complex technology just to get a extra 2-3mph. Until you can land a tri-foiler on a beach, the majority of beachcat owners will stay with what works. Look at the H16. It isn't even that fast, but it sure is popular.

Simple + fun = sales
Complex + new = less sales
Complex + new + over $12K = almost no sales

If there were a market for "new breakthroughs" then someone would come up with something.

Mary,

Maybe I can give you a simpler (but incomplete) explanation:

The added weight of the wings is more or less offset by the reinforcements to the beam that will be necessary to widen the boat, so the wing's weight is not the big issue.

The main diference between increasing a given boat's width and adding wings to achieve the same total width lies in the contribution to righting moment from the leeward hull.

When you add wings, this contribution remains unchanged, but it grows when you increase the distance between the hulls.

The other main contribution to righting moment - crew weight times distance to centerline - remains the same in both cases.

As a consequence, the "wide" boat will have greater lateral stability then the "winged" boat - it will stay upright with more sail area or with more wind using the same sailplan.

Diagonal stability is also different, but this is another story.

Cheers,

Sam,
I'll tell you exactly why. It comes down to dollars. Would you spend $50,000 on tooling to sell 10 boats per year and make $1,000 profit on each boat. At that rate it would take 5 years just to break even. That is not smart business. All of the ARC tooling was built 20 to 25 years ago, long before there was a N6.0 or an I20 or an F18 or any of the other new boats. No effort was made to dodge todays 'normal' boats. The ARC22 came about because the SC20TR needed more pitchpole resistance. An old SC20 hull was given a nose job that stretched the front end 2ft and a quickie mold was made back in about 1990. All SC20 hardware, beams tramp,boards,rudders, mast, rigging, sails, etc fit the ARC22. This was a low cost project initially done in someone's garage. Production tooling cost big bucks. Right now the beachcat business is changing fast. What's in today is out next year. Its like the stock market; I think I'll stay out for now.
I have never heard or used the 'ultimate speed' comment. ARC products are not ultimate speed machines. The ARC 27/30 are the best family/daysailing boats going.
Barjack: When I was designing my first beach cats, the trailering width limit was 8.0ft. My first boat was 12ft wide. I talked to alot of sailors about what they wanted in a new boat in 1976 and all of the average size people were tired of being beaten every time the wind blew hard. The 8.5ft width limit came along in the mid to late 80s, about P19 time.
Seeker: Wider boats are faster as you know and weight sensitivity is less on wide boats. The average size person or team is competitive over a wider range of wind speeds on a wide boat rather than on a narrow boat.
The M20 would be awesome in a breeze at 12 to 13ft wide.
Evidently the Hobie sailors here in S Fla don't know how to use wings. I see them sitting on them all the time; never using them to trapeze from.
I have 5ft wings for my RC30.
I don't know what rebuttal you are talking about.
Here's a breakthrough for you. Ten years ago an F40 cost 1 mil+$. That boat has a demonstrated PN of 54. An RC30 has a demonstrated PN of 53.8 in 2003 and costs 1/15th of a mil and is only 75% as long. How's that for advancing "the state of the art"? An RC30 hull weighs 175 pounds rigged and painted; scale that down to 20ft and you get 52 pounds; scale it on down to 18ft and you get 38 pounds. Now, what company has the advanced technology? What company produces the lowest PN production beach catamarans in the world?

Thank you, Luiz. That makes sense. I am now visualizing a whole new concept. If we need to stick with the 8.5' width, what we need is a boat that has the capability of moving the entire mast toward the windward side of the boat and a hiking or trapezing wing or rack on the windward side, as well. And when you change tacks, you slide the mast to the other side and move or slide the wing or rack to the other side.

What do you think? And don't forget that you heard it here first.

You are asking a great development designer to bound his creations by "rules" in order to prove that he is better then other designers within those limits.

Whenever there are "rules" limiting what can be done, the design work is greatly simplified. If there is a max L.O.A., max beam and max sail area, every designer will start with those figures and a square bow and transom. You will never see a sloped bow like that of the ARC 21, for example, wich is not "rule efficient".

The final result is that artificial limits level designers of different skill level (to a certain extent).

Since this is perceived by the best designers as an unfair situation, it is only natural that some of them refrain from entering this kind of competition.

Creative designers are not challenged by working within artificial limits - they like the natural ones and set ambicious goals for themselves.

Cheers,

Mary,
What you described is a proa, so maybe I saw it somewhere else before...

Luiz,
I know it is the same basic concept as a proa, but I didn't know a proa moved the whole mast. I thought they just moved the rudder to the other end of the boat or something like that when they want to change directions.

But, of course, every time I come up with an invention, it turns out somebody has already invented it.