Beam Hinge...Q 4 Bill Roberts

Bill…as an aeronautical engineer could you please answer the question as to why someone has not been able to design a hinge that would allow the standard beach cat to fold up in the center? Wings on aircraft, carried aboard aircraft carriers, have had folded wings since at least WWII…I am assuming they are designed with a keen eye on weight…and if they can withstand the forces of supersonic flight they obviously can handle the loads involved with a catamaran such as the ARC 22. With your engineering background I would have thought that you would have tackled this problem if it were economically feasible. Why hasn’t it been done?

Bob

Dear Seeker,
If I may interject before Bill posts his answer…… (and the answer may just simply come down to weight). In WWII, the Japanese had a “Catamaran” that was launched from a Submarine. The Sub(s) (they built 3 of them with intentions of attack the Panama Canal very late in the war….) was one of the largest Subs ever built until the US built one larger in the late 1960’s during the Cold War. I say it was a Catamaran… But really it was a Sea Plane with two pontoons or floats…. There is your Catamaran that folds!

The interesting thing was the complexity of the winds, they were fully articulating. They didn’t just fold up….. They folded up and then folded back inline with the fuselage for storage. Very High Tech for 1945.

The question I have for Bill (or would like to add)….. Has anyone attempted to race, sail, and survive….. on an 8 ½ foot wide ARC22 or SC20TR. With all of these race organizers putting limits on beam width – Did you ever slim one down and try it out???

Marschassault…if you follow Bill’s posts on the subject he has given specific engineering data for why he has not limited his ARC 22 design to 8.5’ beam. He has given example after example of why 8.5’ catamarans are stuck in the doldrums of PN# of +- 60.

As far as an 8.5' ARC 22 or SC20...look on their web site and you will find the ARC 21...it is designed at 8.5' beam.

I am interested in methods of overcoming the land-based problem of transportation rather than compromising on the water. I understand the Shark does it with hinges, but there you are dealing with a hard deck…it seems to me that someone could design a hinge system that would work with the 4” or 4-1/2” round aluminum beams that are commonly used. Given that we have vastly superior technology (compared to WWII) the ability to design on CAD, and to cut it out with CNC without expensive tooling, it should be doable.

I just finished a course on Autodesk Inventor 7, a parametric modeling program...I would think that it, or something like it, would be up to the task...you can even animate it showing it in its extended (locked position) and folding up...

Bob

Hi guys -not bill either ,-

The Shark does fold up ,-it was an earlier predicessor in the B -Class to the Tornado ,-also w 10 ft. beam .

nice web site with pics of it folded on the trailer
http://sharkcatamaranclass.org/WHAT.HTML

also there is the Arc 21 w 8.5 beam ,--nice looking cat .
http://www.aquarius-sail.com/

This would be a great ocean racing cat for the Atlantic 1000 built in a 20 ft -8.5 beam version .

Tybee / Atlantic 1000 http://www.tybee500.com/

hope thats helpfull
Merry Christmas
Happy Holidays

About 8 years ago the people that build the Maine Cat 30 cruising catamaran made a 22 foot model -- Maine Cat 22. It had a folding beam. It was pretty much a (dry) day sailor with a hard deck. I'll try to attach a pic. Here's a website with the specs.
http://www.boats.com/content/default_detail.jsp?contentid=7850

Other than the Shark, the Viva 27 from back in the mid-80s also had a folding beam. That was a pretty heavy duty design though.

Marschassault…if you look at the PN for the ARC 21 with 8.5’ beam which is 61.5, and the ARC 22 with 12’ beam which is 57.3 I think you can deduce your answer…a 4.2 point rating difference is significant to say the least.

Bob

Hi Guys,
I went down this road in 1976. I knew that to build a faster catamaran the boat had to have more sail thrust, a bigger engine. To generate more sail thrust you have to have more righting moment than the other boats. THEREFORE THE BOAT MUST BE WIDER!!!
Then I considered all kinds of variable geometry beams,etc. to have a wider boat to sail and a narrow,8ft wide, boat to trailer. The simplest, least weight and cost impact method I found to accomplish this goal was telescoping beams. This mechanical arrangement added about $1000.00 to the cost of producing the beams/tramp/boat and about another $1000.00 to the trailer cost for telescoping cross beams/arms. These cross beams were rigged with cables so that the trailer winch could be used to telescope the boat out to 12ft or in to 8ft.
The manual trailer winch could even be replaced with an electric winch which made the telescoping operation 'push button'.
To telescope the boat either way added 15 minutes to set up or take down time. The beach cat sailing public turned the idea down; only a few hundred boats were sold in ten years. The NAMSA PN for the SC20 was 62 when the Tornado was 64.
Today the fixed beams and tramp can be installed on an ARC22 catamaran by two persons in 20 minutes. The mast and standing rigging takes another 20 minutes. Spinnaker pole requires 10 minutes. Rudders and steering requires 10 minutes to install. Sails up takes another 15 minutes. Load the spinnaker and rig spinnaker sheets takes another 10 minutes. So, all in all it takes about an hour and a half to take an ARC22 fron trailer to sails up. Hinged beams might reduce that time 5 minutes and add $1000.00 to the cost to produce the boat. The hinges and machining and precision pins are going to cost $500.00. Then comes the impact on the dolphin stricker system, the jib traveller track and the main traveller track on the rear beam. For 5 or 10 minutes savings and 5% to 10% more cost to the boat; I don't think it is worth it.
Bill

Thank you Bill for such a complete explanation…your logical approach to problem solving is such a refreshing change from the “more complicated the better mentality” that seems to be prevalent on all fronts.

Bob

I've seen a cat by the name of "Tyger Tyger" sailing in the Los Angeles region that has hinged beam for trailering. I think the boat is ~15-20 wide and about 25-30 ft long. It is not an ARC## or SC##...something totally different. The beams were hinged off centerline with tramp still basically attached to the hulls. I believe the owner's first name was Geoff Deutchmann. Wish I had more details on it...we raced against it in this years Newport to Ensenada run...we were on an F28R trimaran. He beat us.

Mike.

Doesn't the Hobie 21 have to ability to telescope the beams and trailer cross members?

Mike

Hello,
More history and theorizing.
I believe the B-lion by the Hubard Bros. folded in the middle and may have had aluminum beams. The hulls were canted too. Also the Shark is not a B class cat- too much sail area.
About the beam widths...the wider boats need to be built heavier, but can handle more sail area to windward. If you just put narrow beams on a wide boat it would be over built for the forces that would develope, and thus not be as fast as a boat designed specificly for a narrower width.
For example A cats are light, narrow, and fast.
For overall sailing in the long run, if you built a special tornado lighter, maybe a shorter mast, with 8.5' beams i wonder if there would really be that much different than a stocker? prolly depends on how light, and how often you sailed in really strong breezes.
happy holidays

The Deutchmann boat is a VIVA 27'. Geoff still owns the boat, and in fact there are several VIVAs in the area - one was recently sold to there from the Gulf Coast.

sea ya
tami

Wow, with a first name that long I would hate to try to write out the last name. But seriously his name is Geoff Deutschmann and his boat, Tyger Tyger, is a Viva 27 (28 footer) as Tami suggested.

Geoff's was the first of 4 or 5 built and appears on the front of the brochure.

Brad Gaian recenly brought the one from LA as Tami also mentioned. LA to L.A., what a strange trip!

Both are parked in my yard, just a few feet from Glenn's Tornado. They are 16' wide and hinged. The third one that I was aware of was owned by the builder and he had widened his to some 24' or so and added a front cross bar. I don't thing that customized one would fold.

I've raced on Tyger Tyger the first time Geoff took it to Ensenada, along with your friend and mine, Glenn.

I've sailed with Brad to Catalina Island (pic attached) and next year we may try for Channel Islands National Park.

GARY

I am not Bill either but I agree with him.

A folding beam boat will never be as light and stiff as the same boat with a fixed beam. Also (from experience) folding beam boats are never as easy to operate as they show in the brochure

A good tilt trailer with a hydraulic tilt adds maybe 5 mins to the assembly time.

If I were going to spend time, money, and boat weight on making a wide easier to trailer flat I would work on making it easer to assemble.

* A good index system for the main beam/hull. Some kind of tab that aligns the beam and hull perfectly every time.

* 1/4 turn fasteners for the beam bolts.

* quicker way to lace and tighten the tramp. (for example running the lacing line through micro blocks and using the mainsheet to tighten them.

You get the idea.

Sounds like some of the concepts used in the Dart 18. They have beam locating tabs with spring-loaded clips to secure them. They don't take any real loads, but just hold pins in place that secure the beams. Very quick.

Mike.

"Tyger Tyger" is the first Viva 27. She resides here in Marina Del Rey along with one of her sisters, "Avalon Darlin." About four or five Viva 27s were built.

Geoff has a beautiful new suit of Elliot Pattsison sails that includes a square top main.

Brad has taken Avalon Darlin down to San Felipe, Mexico on the trailer where he intends to shove off for Cabo San Lucas.


GARY

Gary,
Is the boat in the picture the one from LA? Do you have a full pic? I almost got to sail on one here in LA before Tilley sold it. (The race got rained out.) I would like to see a pic with a new suit of sails on her.

Clayton

Here is a screwy idea.
Make a huge subframe for the Front & Rear beam with the trampoline attached to side rails. Then have four quick release pins at each corner and a few for the side rails. Trailer the subframe vertically. So the question is what is the minimun Federal Bridge Clearance height. (smells like a H16 tramp on Sterods). The additional price(vs indus Std) to pay would the weight of the siderails, and indentation tooling to the inside shear.

Yes, and yes it is from L.A. also! It was moved from LA to L.A. (L.A., CA) last year. New name is "Avalon Darlin."
Viva Pictures; Tyger Tyer and Avalon Darlin Be sure to click on the folder named "Avalon Darlin."





Yah, and so would Brad! But the boat with the new sails is Geoff D.'s Tyger Tyger, not Brad's Avalon Darlin. I don't think I have any pictures of her with the new sails. Geoff's prepping her for new paint, right now.

GARY