ARC-21 Rig

I think your question would be better answered by people familiar with the viper and not the mast.

I think you'ld be better off getting a skiff at that point, cause it's what your going to have.

I don't have the engineering experiance on catamarans to give a definate answer, but I'm sure Bill can. IMHO, you'ld pull the chainplates or shroud ends right out of the boat for starters. An ARC21 rig is pretty darn powerful !
I14 or 49er is in your future

Or if I were you, I'd sell the mono-slug and get a cat. Just having fun with you, I like leaners too.

Jeff

Typically a catamaran rig has no backstay because of the high roach sails used. The mast is held from going forward by swept back side stays. The mast itself is kept from breaking while flying a large spin by maintaining main sheet tension (in effect a backstay of sorts) This feature works very well in catamarans beacause they are able to generate significant apparent wind, and hence keep a large amount of mainsheet tension with correct sail shape while going down wind.

You may want to explore whether you can accomplish this with the semi-planing hull of your boat, or rig some kind of doubler back stay while running the spin. Busted spars are ususally no fun and very expensive.

Good luck

Matt

Hey Jeff,

Before you ask if it can be done….. Ask yourself if it should be done.

I’ve never sailed a Viper 640, but….. By the looks of your picture (if that’s your boat) – she looks like a beautiful machine. My point – If she were a basket case (a total shamble)… ok I could see trying something along the lines of what you are thinking. But she appears to be in great shape – why not keep her “stock” and build up (or buy) something else. I guess I’m a purest when it comes to stuff like that. If the boat were beyond any hope of becoming a “complete” boat again – I could see playing with modifications. You run the risk of taking the boat out of its class – making it un-marketable. Breaking the boat by over powering it. Or simply turning what would seem to be an inexpensive modification - in to a project that would cost more than a stock replacement.
Don’t mean to rag on you – it sounded like a cool idea! If you’re looking for more of a thrill, more power, and a quick way to impress the chicks….. Move to two hulls! Sounds like you’re a closet Cat Dude anyway!

Ballast

Hi Jeff,
The ARC21 mast is the same section and lenght as the old standard SC20. Carrying a mast head spinnaker will require a couple of 1/8th inch Vectran bachstays. Each backstay will require a little 6:1 mechanical advantage pulley system at its lower end so that the leeward backstay can be eased as necessary. With the chute up the main will likely be trimed down the center of the boat. This is proper trim on a chute carrying catamaran. A close reach is likely to be the point of sailing that requires the 'trim out' position for the mainsail.
What does the Viper weigh? It sounds like you are going to soup it up something like an Australian dinghy. Get yourself some agile and quick crew.
Good luck,
Bill

Hi Jeff,

Be careful with the vang loads. Catamarans have a wider traveler and do not use a vang. The mainsheet takes the twist out of the sail. Once you add a vang to the boom it will be loaded in bending, not just compression. There will also be a huge compression on the gooseneck.

What do you plan to do with the mast step?

Sounds like a fun project.

-colin

Go ahead and add some racks, and make it REAL fun.

Check out this Lake Monster we built...

Mike - Yee-Haw! That is too cool. I do think you need a bigger spinnaker though...

As for the 21 rig on the Viper - remember that the 21 rig also is a rotating mast. That would mean for the viper either not letting it rotate, or coming with a mount either on the deck or keel to let it rotate. If it is mounted on the keel as it appears is stock, the boom will be pretty low to the ****. Sounds interesting though! Good luck and keep us posted!

Hi Colin and jeff,
Hopefully the boat won't need a vang. If it will develope enough relative wind velocity, the vector will be far enough forward that a couple of feet of traveller track either side of center will be ample. Idealy this track will be located under the clew of the mainsail. If the boat turns out to be a fast sailing system, the mainsail will always be going to windward and trimmed on or near boat centerline.
Good Luck,
Bill

You are right, I am trying to make the Viper 640 an "old man's" skiff. It has a nice comfortable place for the skipper to sit, and the 185 lb keel gives it some stability.

I share your concern about pulling out the chainplates.

Thanks
Jeff

Unfortunately, the Viper 640 class is pretty much dead. It was somebody's "Boat of the Year" in 1997, but the builder went out of business 2 years ago. The molds were sold to a company in Europe, but little / no activity since then. Only about 80 boats were ever sold. There is only one active fleet in Marblehead MA.

So I figure there is no advantage to keeping the boat "class legal".

As far as a shambles goes, the mast is broken, mainsail/jib/spinnaker all were damaged and need repairs, and the mast step was torn loose.

So I figure I'd spend some extra money to make the boat more exciting.

Thanks for your thoughts, and I have the same concern ... lots of cost with the risk of a "hacked" result.

Bill -

I just realized that you must be the designer of the original Supercat boats. Thanks VERY MUCH for your thoughts !!!

The running backstays sound like a good idea. I wish I had put them on the Viper before I broke the mast. It was 20 knots downwind with the spinnaker when it broke, and we were easing the mainsail for control. Probably lost too much leech tension.

The Viper 640 is actually a fairly heavy boat. It is 725 lbs total, with a 185 lb bulb of lead at the bottom of the foil.

I'm actually worried if the ARC-21 rig is large enough. The original Viper mast was 28' vs the ARC-21's 33'. Sail area is 252 sq-ft vs 282 sq-ft on the ARC-21.

But the ARC-22's 38' mast and 380 sq-ft sailplan is probably way too big. So I thought I'd try the ARC-21 rig with a monster masthead spinnaker, and an 18 footer skiff style long spinnaker pole.

Thanks again ...
Jeff

Bill -

The mainsheet traveller idea sounds like a good one, but will be hard to install. I'll try to figure out how ...

Jeff

Mike - That is an awesome boat. Are you still glad that you put all the money and effort into it?

Keith - The rotating mast is definitely an issue. The Viper 640 deck is not strong enough to step the mast, so it has to go down on the keel. I am hoping to talk the ARC-21 folks into selling me a mast with an extra 2-3' of length on the bottom, so that the boom isn't too low.

Thanks for your thoughts ...
Jeff

When I added a spin to my Hobie-18, some advice I got about sailing it in a good blow was "cleat the main, toss the sheet onto the tramp, and take your pitch-pole like a man!" - The truth of it being never release the mainsheet unless the spinsheet has already been blown, or you'll be shopping for a mast...

Maintaining the rotating feature would be interesting.

Well, I'm shopping 😉 that's exactly what I did when I broke it ... ease the main with the spinnaker up in a blow. I liked Bill's suggestion about running backstays, although they are messy and extra crew-work.

I'm planning to keep the rotating feature. It will require cutting away a small amount of the deck around the notch where the old mast went through, to keep the deck out of the way. The mast step should not be a big problem if I attach a small stainless plate to the keel which can accept the bolt for the rotater ball.

Mike -

That is an awesome boat !!!
- How long is it?
- What class was the original hull? Keel?
- How did you attach the racks to the hull?
- It didn't look like there is any bracing on the spinnaker pole. True? I would think that big a kite would break anything that long.

Are you still glad you spent all the money and time? I'm facing alot of the same. My gut tells me its worth it though, cause I love messing around with boats, and I love going fast, but I'm a mono-slug at heart.

Jeff

Hi Jeff,
The max shroud tension is determined by max righting moment. If you don't change max righting moment, you won't change max shroud tension or max chainplate load. If you add trapeze, the extra righting moment goes directly from the trapeze belt/person to the mast/rig/sails and does not go through the standing rigging. That is part of the beauty of the trapeze. The trapeze adds extra compressive loads coming down the mast but it does not add to max shroud tension.
As far as stepping the mast on the deck goes: This is the way to do it. The ARC mast step ball holds the mast base while stepping and unstepping the mast as well as being the mast rotation bearing. Take a piece of your broken mast and make a short column from the old mast step to the underside of the deck at the new mast step. This way when you step the new mast on the deck, the boat won't know the difference and all the loads on the structural system will follow the same paths they always have; no difference.
I don't know exactly where the clew of the mainsail would come to relative to the transom of your boat, but if it is close to the transom, you could beef up/make new and stronger the cross beam that supports the upper rudder pintle and install a mainsail traveller track there.
One of the first things you need to do is make a good estimate of the price of all of these parts. I would estimate you are talking about you spending 10k on parts and sails with you doing all the work. If you are not handy with doing this type work, add another 5k. You know how boat costs are, things could run up to 20k with a few surprise problems.
Good Sailing,
Bill

Hi Keith,
Your problem is that your spinnaker pole is too short and your spinnaker is too vertical. The force vector from the spinnaker is too close to horrizontal and this makes any boat pitchpole. A proper length pole will lay the spinnaker back at the head so that so that the force vector from the spinaker lifts the bows as well as well as pulls the boat forward. A few more feet of pole length makes all the difference in the world in boat behavior with a spinnaker.
Bill

Bill,
Thanks for the input - I never actually pitched it while using the spin. The quote was just something somebody told me to reinforce that I should never, ever, release the main sheet when a gust hits - as in it's better to take other consequences than to break the mast (a fellow in our Fleet lost his Mystere 6.0 mast this way this past year). I actually found that the boat had less tendency to stuffing the bows when the spin was used.

The "stock" set up for the 18 used an 11.5 foot pole, the max people told me that would be trouble-free was 13.5, maybe 14. I set mine up so I could experiment, starting with 12.5 with the capability of moving fittings to get 13.5 if I wanted. I wanted longer length to move the spin forward and reduce the chance of closing off/backwinding the rest of the sail plan, but was worried about incurring lee helm. 12.5 seemed to work real well, no vices helm-wise. Unfortunately the boat got hit before trying out the 13.5 setup...

Keith,
Why do Hobie, Prindle, Nacra, etc owners have to "EXPERIMENT" and work all of this spinnaker related stuff out for themselves? I would call it poor product support.
Prior to the I20's use in the Worrell, I went over to the Holiday Inn at Jensen Beach and took a look at the boats. I had never seen so many Rube Goldberg, poorly thought out, spinnaker pole rigs before. Some of those boats needed alot of help. Now most new beach cats have gone to spinnakers and many of the older boats want to upgrade. Why do the factories not come out with well done spinnaker kits for their boats that did not come out with spinnakers in the first place? It would be a source of income. Our beach cat factories and the beach cat sailors would both benefit from well done programs.
As far as satisfactory working geometry goes relative to spinnakers there is a sweet spot fraction on the cantilevered part of the mast for the spinnaker halyard where mast breakage does not occurr. There is a sweet ratio between mast height and spinnaker pole length where the spinnaker tends to lift the bow more than make the boat pitchpole.
Good luck with your spinnaker and your spi pole is too short.
Bill

Spinnaker use on cats has only become widely popular and accepted in what? the last 10 years or so? This is due largely in part to the Worrell. Most of these manufacturers that you blame for 'poor product support' have already made a substantial number of boats and have established substantial classes since before the spinnaker really became popular on a cat. In the interest of not further diluting the classes already estabilished, these manufacturers choose instead to maintain the existing boat configurations to the benefit of strict one design racing. I think it's not poor product support but it's a carry over from the 70/80's marketing philosophy with an attempt to maintain the bigger picture: product placement in the market.

However, we're now seeing a transformation in the industry with the dilution of the classes to the point where one design and classes are becoming less important to the sailors to some degree. As a result of this, we are now beginning to see the manufacturers make more options to supply the widely varying desires of the sailors. The Hobie 16, 18, and 20 has a spinnaker option, Performance Cat's 6.0 now has a factory spin option, and we're seeing 17' boats from several manufacturers with sloop, uni, two up, one up, spin, and no spin all in one platform. The days of the manufacturer trying to maintain control over one design racing are fading.

As to the sailors with the Rube Goldberg designs, God love 'em. I'm probably one of them. It is through experimenting and refinement that new and easier ways to do things come about. Rube believed that there were two ways to do things: the simple way and the hard way, and that a surprisingly number of people preferred doing things the hard way. I believe that through sometimes doing things the hard way, I learn more, and an easier way becomes more obvious.

Jeff I have followed the posts and wanted to let you know I have a complete ARC 22 rig available for sale. I sail a 22 and thru a series of events acquired an aluminum mast completely rigged from the factory. In addition I have an oversized Calvert main, oversized Smyth jib and a stock Smyth chute that I can "package " together for you if interested in any or all. I have changed to a carbon mast and dont have any need for the extras mentioned above.Let me know if you have any interest.

Mike Kelley

I clocked one on our lake at 18 kts with the chute up in 18-20 true.
Why do you want to go faster?
That boat is already pretty darn hot, I think the other poster said it correctly. "Get yourself a cat man!!"

Dave Mosley
Team SEACATS!!

Mike -

Wow !!! Although I'm afraid the ARC-22 rig would be WAY too much for the Viper 640, I am intrigued.

Could we talk via Email? jeff-coe@houston.rr.com

Jeff

Perhaps. See pic. The boat sure felt right, and given that I had decided to not do the dolphin striker thing, this is as long as I felt comfortable going given the comments I had gotten from others who had added a spin to these boats.

Good point on why certain boat types owners have to experiment. In my case it was simply a matter of wanting to try something on the cheap. I new I wanted to trade up from the 18 to another boat, so a big expenditure for new kit didn't fit my plans. I'd rather spend that money on another boat! I wasn't looking for the perfect set-up, but I wanted to learn what was involved and experience sailing a spin cat without worrying about busting up a new boat. Hobie does sell kits for these boats, but I'm not confident they're "right" - witness the short pole.

Poor support - true, true. I'm currently trying to get some info on spin set-ups for my H-20. I've found more people that have done it to this design, but info again is from roundabout type sources. It would be great to simply get a guide form Hobie, and some kind of feel for how the boat works with what they are selling.

But more to the point for me - the tinkering was almost as much fun as sailing the boat afterward! Learned a bunch. It might have a junkyard dog look in some ways, oh well.

Inspiration for the whole 18 thing came when I came into the posession of a windsurfer mast. Sure looks like a spin pole to me...

Search for a sail turned up a Hobie-18 SX spinnaker in great shape. The hard part truly was trying to find ANY information on how a stock Hobie-18 spin should be rigged. Halyard height? Sheet location?

I deduced the measurements from a variety of hints and sources. I went with a longer pole than "stock" again with the option to try longer.

Anyway, the one thing I did know for sure (from sailing sailing and inspection) is that sheeting point needed to go forward a bit from the pole being longer.

But - Hobie does sell kits for their boats. It's just that there is no OD racing for them, so people will be just as tempted to experiment as to buy the kit. I decided to experiment...

Cheers,
Keith
Keith

I've found that most of the Rube Goldberg's I see have only opted for these homemade contraptions because they feel they can do something as good as (or better) than the manufacturer much cheaper. In some cases this holds true, but I would say that those instances are the exception rather than the norm.

Yes, there are plenty of examples where it would appear that the manufacturer is overpriced. Still, who put in the man-hours for design and construction? Only when economies of scale come in does the return on investment become positive and prices drop... but I'm not an economic's major, either!

Hi Waterbug,
My point is that it doesn't cost any more for the parts to do it right than it does to do it wrong. Some of those early Worrell spin rigs had so many struts, they looked like 1950's TV antennas. When they break, nothing costs more than doing it over again and you blew that leg of the race or that weekend.
That is why it is important for the factories to have a well engineered system and then sell kits.
Bill

Jeff,
What your trying to do is interesting. The issue is how automatic you will need the rig to be.

Speaking from skiff experience and zero knowledge of the ARC range.
Skiffs are much more tender than any cat. I suspect this will also be true of your sports boat. One sport boat (Boatspeed 23?) down here is a filled (the hull is extended to the end of the old rudder gantry) in 80s 18teen with short wings 3 on trap and a number 3 18teen rig).

Cats have a higher inertia and you may find you stagger rather than accelerate. (Im not putting ARC products down here).
I know there are some 18teens in california and perhaps they have "old" rigs available. Alternatively you can pick up rigs from the 18teen teams in Au cheaply. They are designed for mast heard kite forces without backstay. I believe the sticks are now being made by CST (composite spars and tube in Sydney amongst others). These rigs also flex under kite loads and thus automatic downwind as well.

What I would be inclind to do is get a rig designed for the boat. Wont be much more expensive than purchasing a new ARC rig. You will get better balance for the boat in the end. Measure everything the rig designer will need everything you can provide.
Which ever way you go expect recutting, thus get a sail maker who has interest in your specific project. If possible find one close who will come out and both crew/skipper and visit the boat.

Good luck

Stewart