Hi Stewart

I agree with you…the building materials/method of construction is twenty years old…yet they market it as something new and improved…you will notice in my earlier post I said some of the new boats/classes are marketed as High Tech/High Performance…I didn’t say whether they “were” actually High Tech/High Performance…:) that remains to be seen...and when a 20 + year old boardless beach cat design comes out of mothballs with a new sail plan and sails that well against current racing cats it calls a lot of things into question beyond just the PN of the ARC 17...

Bob

This thread was originally a question about planing hull cats vs. displacement hull cats with spinakkers, but was quickly hijacked to become an advert for Bill`s new boat, while at the same time gave Bill an opportunity to discredit designers of other boats :Quote from Bill Roberts, after hijacking this thread to turn it into an advert for his products :'"All boats that fly spinnakers have lee helm". Only boat designs that place the daggerboard in the classical position, approximately at the shroud chainplate, have lee helm with the spinnaker up. This is a system design that has ignored the spinnaker during the design phase of the boat development and the designer/manufacturer expects the sailing public to put up with it. There is a sail/boat design system that does take this CE migration into account. The design system is called "shared lift" and it is incorporated into ARC products. It has to do with shifting the board location forward so that the CE with spin up cannot get in front of the board. Then down sizing the board and up sizing the rudder so that the shared lift between the board and rudder is in the correct effective location for sailing the boat as sloop.'
That`s wonderful news. He then goes on to tell us how any beach cat that was designed by anyone else has terrible tendencies to kill, maim & frighten the hell out of anyone, while his boats are built with only SAFETY in mind. I hope he has good legal counsel, from what I understand you can get sued in the US for looking at someone funny, never mind calling them an irresponsible yacht designer : "I see nothing but praise for the H16 on this forum. In West Palm Beach, Florida two sailors have lost their lives because of the unsafe characteristics, easy pitchpole tendency, of the H16 design. It is the same for everyone sailing a H16 so, what the heck." Bill, I suggest you write to some US sailing magazines & ask them if they`ll publish that for you, then wait for Hobie`s lawyers to start calling you. It must have been a HUGE pitchpole, if that was the official cause of death. Personally I`d rather be caught out on a H16 in a storm than a 17ft boat with more sail area than it can cope with.

Yes, there are more than one way to make a cat fast - one method is to improve on construction methods to make the boat stronger & lighter, and put on a reasonable sailplan that is manageable in up to 25knots of wind, probably the upper design limit for most beach cats (oh, except for the SC range of course). The other method is to use cheap construction methods, overbuild them to make sure they`re strong, don`t worry about the weight too much, you can always load up the sail area & widen the boat to compensate.
Just don`t ask me for help dragging it up the beach.

I still can`t figure out how some people believe that a 17ft boat with more sail area than a F18 can be regarded as a beginner`s boat. I`m really impressed with the idea that someone actually built the thing, it seems horribly overpowered to me. The only SC boat I`ve seen is a Supercat 20, took the guys 2 days to rig it, was heavy as a speedboat, and once capsized it had a complicated stay-lengthening device to help right it.It took so long to manipulate that they went turtle, and needed a rescue boat`s assistance. It never beat a Tornado over the line at our club, old Tornado with old rig, one trapeze and heavy by today`s standards. Perhaps the owners never read the manual.
I also understand that the "new" 17ft design is not a re-hash of the old SC17 hull shape, but is in fact a new design, which is what lead me to ask why design something new which doesn`t fit into any of the formula classes - If this was done it would go a long way to getting more growth in the formula classes in the US, which would benefit everyone. I`m absolutely amazed that anyone would buy a NEW boat that doesn`t offer the ability of inclusion in one of the Formula classes. I know that the Formula classes are not huge in the US, but then if the US designers are purposefully avoiding them it`s no wonder.
I believe that Wouter has made the only sensible comments on the original question in this thread, and summed things up quite nicely with this :
The whole point comes down to the fact wether the ARC products are fast because of efficiency or because of the huge rigs they feature. The problem here is that without having a really comparable design using the "normal setup", it's hard (if not impossible?) to tell wether any speed increase is the result of superior efficiency or just the result of having a bigger engine.

I`ts good that Bill designs boats that are different, challenge the "norm" and don`t conform to formula rules. As he says, they aren`t intended for racing, except against themselves. Sounds like his ideals are not so different from those he criticizes the most.

Cheers
Steve

BRAVO!

Hi Eric,
All it takes is money. The tooling that Aquarius has was built back in the 1980s and that is all there is. You guys stand around and say "build a new boat of this or that size and the world will beat a path to your door". Been there and done that and it doesn't work. The telescoping SC20 won the OAK Regatta in 1981 by a wide margin over all the California hot dogs. The SC20 had a demonstrated and substantiated PN of 62 and the Tornado had a PN of 64 in the early and mid 1980s. The tall rig 20 was 60.I gave the sailing public what they "said" they wanted (a boat faster than the Tornado) and I built it and then they didn't want it afterall. A couple of hunderd boats were sold over ten years; not enough to keep a boat company in business. I lost a nice retirement building the SC product line. The SC 17 is the only boat I designed that made any money/profit. I have some sensitive scar tissue, Eric. Understand now why there is an ARC17 effort?
Good Sailing,
Bill
Good Sailing,
Bill

Hi Jake,
All of the SC design work and tooling building was done back in the late 1970s and early 1980s. This is long before there were any box rule design design classes.
When I was doing my bech cat design work, the contest was about speed not efficiency.
But speaking of efficiency: The RC30 has a PN of 54, same as a Formula 40. The RC30 is 30ft long vs 40ft for the F40. A new carbon RC30 with trailer, beach wheels, an extra siut of sails, spare battens, outboard motor, life jackets, trapeze belts, gloves, tool box and hand tools, anchor and line, lights and navigation charts, everything one could possibly need for the boat costs less than $100,000. A new F40 costs over a million dollars. Now, how's that for efficiency, Jake?
Bill
PS You Applaud the M20. I do too. The unique thing about the M20 is its weight, 150 pounds less than a Tornado or 200 pounds less than an I20 or N6.0 and you do not mention that. Why not? Do you have any idea what it would cost to take 200 pounds off the weight of an I20 or N6.0?

Hi Wouter,
I appreciate your compliments and good wishes. This is quite a change. I can't help but think you have had something special to eat or drink just before you wrote the above letter. Your mom must have fixed you your favorite dinner.
Good luck with the F16 class.
Bill

I understand, Bill. I just wonder, as others do, why you have not focused your efforts and resources to build a boat to compete against a more popular design. Using the same box or "formula" would for sure highlight your design innovations. Don't get me wrong, I think the ARC 17 is an excellent design, innovative in design of the controls and now I have seen that is very fast in moderate winds.There is just no boat to compare to to ferret out the strenghts and weaknesses. If I had the cash I would look at the Arc 21 0r 22 in a heartbeat, again, great innovations and simplicity.
I appreciate the fact that you have devoted your time, talent and treasure in the pursuit of your interests, not many people can say they had the balls to do it.
NOTE: Another poster threw down the gauntlet, I just stirred the pot.

Ahh Bill,

Not much has changed. I'm really not hung up on the ARC-17. I expect it to be a great boat and would love to see more of them on the water. I'm still comfortable with you as well; next time I see any of the SC in NL again I will again take their picture and send it to you (like I did a Texel) and convey the regards of their crews.

The thing that got me going was the "story" around the ARC-17 design and its quite implied dissing of several other designers and related designs.

Really you are not the only designer who has experimented on cats or taken measurements. Nor are you the only one confronted with the issues around a spinnaker. You solved it in your way the others in their way. The real life results are different from what was stated as undeniable truth. Therefor the theoretical model you used was not describing the reality accurately. It is by all means a "feels right" model but inaccurate none the less.

Without hard proof the views expressed become dogmatic. Hence the gauntlet thing.

Now on my my part I haven't quite worked out why it behaves differently but that is mostly because of lack of effort. When something is not a problem than I'm less willing to explain why it is not a problem. I tend to accept it and move on.

Factors that may result in the different behaviour :

-1- Spi is fitted asymmetrically to the boat. The normal rig pushed the boat along almost along the centreline. The Spinaker is to the lee of this and thus its lift factor will induce a weatherhelm effect as well.

-2- The conponent of the total lift force that lies along the centreline may be several times greater than the component perpendicular to the centreline. It may be that

Leehelm component - weather helm component = lever 1 * force perpendicular to centreline - lever 2 * force along centreline = close to 0 or very small.

To give another example. Yachts without a spi have greater weatherhelm on deep downwind sailing legs than on upwind legs. With spinnaker they balance out again. A different setup I agree but it shows that there is more to the system than the simplied model that was used in this thread.

This is my last post in this thread.

Now, indeed Fair winds to you and I'm looking forward to more race results. If anything it helps to improve on the understanding we both have on the subject.

Wouter

Hi Wout -Bill -John and all ,-great thread ,-just sat back and read others on this one though very interested ,
like John P posts and Bill,s as active designers of existing cats in the marketplace .

Wout your perspective is from a main objective and goal of building a Formula class {worthy endeavor } but in discussions it often makes you {talk past another} as they say .

An interesting project > I have a SC 15 that I,d like to modify w spin {experimented a little already with one on the sc } and have it comply with F-16 rules for future racing ,--I,m not sure if I,ll add boards or a smaller molded in skeg or just use more rake and load up the large rudders more on this non boarded design .

I may add a little foam expoxy v shaped {for rudder movement} fairing plate off the stern to make it a full 16 ft .

The problem earlier on migrating CE forward with the spin up is the problem I,ll face in adding the spin .

In looking at a side view diagram of any cat -
http://www.parlier.org/site02/images/vue-face.jpg

The CLR -{area of underwater profile inc boards & rudders}
has been designed in older non spin cats without consideration of the spin area which when raised moves the CE way forward .
Most racing sailors have found that when you rake the mast aft more under spin the better your speed and handling characteristics. In effect moving the total CE back -
but how much ?
The spin pole is a certain distance from the bows per rules ,-the mast base in located the same ,-an extreme amount of added or extreme mast rake may be a meter or little more ,--thats all .
Draw this out on a particular design with accurate sail area mast height and general specifications in the normal position {without spin} and with extreme mast rake and spin area in calculation of CE to CLR .
Spin are av equal to or larger than the main &jib area
spin tacked out forward on the spin pole.

The CE evan with extreme rake is still way ahead of the CLR , tHIS NECCESITATES the moving of the board forward ,near or at front crossbeam location as noted , for spin boats .

One other interesting option would be an evan more forward located smaller angled lifting foil or skeg to change the CLR to CE .
for other readers -
CLR is Center of Lateral Resistance =side view underwater profile under sail and center of area inc boards foils and rudders .
C E is the Center of Effort = center of areas of the sail plan -main -main jib -or main jib spin combinations .

Generally the CLR leads the CE by a small percent ,-allowing for mast effects and wanting some weather helm designed in or nearly nuetral helm .

The forward lifting canted foil nearer the bow to balance the spin CE would create added drag , offset by its ability to lift at higher speed and balance the helm under spin.
In upwind mode this would load the rudders evan more ,
requiring a smaller aft board as well ,-this type of for and aft board configuration is very versitile under many different sail combinations ,--thinking of larger cats -reefing jibs and mains ,-stormjibsails,-and cats with adjustable rigs ,- etc .

An ideal cat design would have an ajustable mast rake ability under sail ,-forward position in normal windstrengths upwind ,--then raked back to an extreme downwind .
The 60 tris have adjustable rigs ,-the first I saw it on beach cats was the 87 Worrell 1000 ,-It was Reg Whites son on a 12 beam Hurricane that had attached a 3 to one block system and cleat at the base of all stays with about 6 ft of adjustment ,-it could be raked back ,--and also to windward a little if desired .

Small inward canted forward lifting foils particularly for 16 ft cats that counteract forward forces -used on the 60 tris so well to carry their huge sail plans ,may be the ideal development for them allowing them to be pressed much harder in high wind speed conditions .

fun to theoretically go through design options and potential variation to explore .
good winds

Seeker San,
So what do your kids hold on to on the 17? Shroud, or hiking straps? Most people think a begginner boat would be like a hobie wave or something with a lip that you can grab on to.
There really aren't any cats that don't dive the bows when pushed hard enough. I just think supercats sail bow down when powered up. Many factors contribute to this. Even if they are hard to pictchpole it still isn't very fast to have the whole hull under water. In the picture that i posted before, the supercat is working very hard to keep the bows up while we are leaning forward. We started at the same time as i recall and we are on the same downwind leg of the race. pretty shure that is Bill at the helm of the SC.
I personally like to sail a boat bows up or flat, not bows down. Wouldn't feel comfortable at high speed reaching with the bows down to get shared lift. Also i take offense will Bill's comment that v in the tail is improper design. So what if it makes a boat harder to tack. Even Tornados only make 1 tack to the A mark if possible. V in the tail and bows up are good in the waves.
In answer to your question about me sailing a SC17, actually, i worked at Boston Whaler SuperCat untill i was fired for not working on Saturday in spite of the fact that they had paid my expenses to race in Miami that weekend. Corp. b.s. -one hand didn't know what the other was doing. 1980 or 81...
Bill's best design was the captive mast step-cudos there, the boats themselves don't do it for me. The round top just funnels the spray into your face and isn't worth it.
The big Trimaran guys seem to use a similar hull for the ammas though.
In any case it's a good thing that you get your kids out there cat sailing in the ocean.
PS. there could be some errors here because the 80's were a while ago.

Hi Eric,
The reason the SC17 was revisited/reinvented/put back into production is because it sold well once and it took no big bucks, no new tooling to bring it out again. The SC17 was designed 25 years ago. All that was done last year was to put new sails on the same rigging and spar and add a spinnaker as an option. This brought the 17 up to the same technology level as the other ARC products.
You asked about something to compare the ARC 17 to, Eric; here are some thoughts.
So, what is the correct PN for the new ARC17? Let's go to the Tradewinds Race results, 2004, and see what we can learn. I suggest we use the last four heats because in the first four heats boats were going around the wrong race course and the 17 used the spinnaker in three out of the first four so things are sort of scrambled. The last four heats are cleaner data and the 17 did not use the spinnaker.
Fifth heat analysis: Using a PN of 70.1 and not using the spinnaker, the ARC 17 finished second on corrected tine. That is 44 seconds behind the D18 and 2min and 27 seconds
in front of the T4.9.
Sixth heat: The ARC17 finished first on corrected time but only by a whisker. The 17 was 22 seconds ahead of the D18 and 1 min and 14 seconds ahead of the H20.
Seventh heat: The ARC 17 finished first again on corrected time. This time it was 50 seconds ahead of the D18 and 1 minute and 55 seconds ahead of the H20.
Eighth race: The ARC17 finished second on corrected time. This time it was 14 seconds behind the T4.9 and 30 seconds ahead of the D18. Tight race!
We could also use the fourth heat: Here the ARC17 finished second on corrected time in between the two T4.9s. The 17 finished 6 seconds behind the first T4.9 and 8 seconds in front of the second T4.9. Tight race again.
Summary: Assuming this crowd of sailors sailed their boats to their respective PNs, it looks to me like a PN of 70 for the ARC17 without spinnaker is a better number than 70.1 with spinnaker. This would make the PN for the ARC17 with spinnaker equal to 67.2.
Here is some more interesting information comparing PNs of boardless beach cats of similiar size.

H16, actual length 16ft and 6ins. PN = 76.1
P16, 16ft PN = 77.5
P18, 18ft PN = 74.5
SC17, 1980 intro. 17ft PN = 73.0
ARC17, 2004 intro. 17ft PN* = 70.0 sloop, new
sail plan
ARC17, 2004 intro. 17ft PN* = 67.2 with spinnaker

The 2004 ARC17 is the same boat as the 1980 SC17 with new sails and spinnaker.
Conclusion: The SC17 always has been outstandingly fast beach cat for its size. History tells us that. The new ARC 17 appears to be even faster.
* PNs calculated based on one,(1), regatta and subject to change as more data is accumulated.
Good Sailing, Eric
Bill
PS In the future, Eric, I am going to respond to questions on Aquarius products on the owners.aquarius-sail.com web site. When I talk about these products here, I get pounded with questions via e-mail from individual SC/ARC owners and I end up answering the same question at least 10 times. It is wearing me out.

Hi Carl,
I want to help you out a little with this SC15. The 15 plug was made from the 17 plug. Two feet was cut off the back end of the 17 plug and then the keel rocker in the aft end was increased, rolled up to a new transom at 15ft to add displacement in the aft end of the hull. The important thing for this discussion is that the front end of the hull was not changed. This means that the 15 like the 17 has the hull lifting surface, deep vee hull shape, in the front 6ft or so of the hull. The middle 5ft is transition shape from deep vee to round and the aft 4ft is a round hull bottom shape, therefore no lift here. Same 2x size rudder is on 15 and 17. This was all done in 1979/1980 to produce a boardless beach cat that would TACK. The aft end of any hull has to be free to slide sideways for a boat to tack quickly and easily. The no lift aft hull end automatically puts the lift burden on the rudder which is a high aspect ratio foil, therefore low induced drag. The rudder is like a steering daggerboard. This boat design is another example of shared lift done in 1979/1980 to make a boardless beach cat tack well.
Now here we are in 2004 and we want to put a spinnaker on this boat. Well how about that; aren't we lucky. This boat already has the hull CLR well forward, like 3 to 4ft back from the bow so adding the spin is "no problem". This boat will exhibit no lee helm with spin up because the sail plan CE will always be behind the hull CLR.
The motto of the best SC15 an 17 sailors is "drive those bows". By that they mean trim the boat out with the waterline halfway up the stem. Always keep the waterline tape underwater at the bow.
This hull design scheme has also led to an increased boat speed hull shape sailing to windward for boardless beach cats. The normal boardless beach hull shape has its lifting hull shape for the full length of the hull. The underwater aspect ratio for this hull shape is the average depth divided by the waterline length. These are numbers like .75ft deep by 16ft long. The induced drag due to generating lift is inversely proportional to this number. This number in this example has a value of 21.3 and it is a multiplier in the induced hull drag calculation. In the case of the SC15 and 17 this multiplier is made up of two parts. One is the hull induced drag and the other part is the rudder induced drag with each lifting body carrying half the total lift force. For the SC15 and 17 the hull induced drag aspect ratio is something like .75ft deep by 7ft long which leeds to a induced drag multiplier like 9.3. The rudder aspect ratio is like 2ft deep by .75 ft wide which leads to an induced drag multiplier like 0.375 acting on 50% of the lift force. So the induced drag coefficient for the hull plus rudder generating lift on a SC15 or 17 is equal to 0.5 x 9.3 plus 0.5 x 0.375 or a total of 4.84. This compares to 21.3 for a normal beach cat hull design. Needless to say, the hull drag on the SC15 and 17 is significantly less than the other beach cats. This shows up when comparing PNs between boats of similiar size. The SC17, which has a PN base, its PN is 4 to 5% lower than other beach cats of similiar size. The hull induced drag makes the difference.
I want you to understand what you have got, Carl, and why it sails like it does.
Good Sailing,
Bill