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Thread: Catamaran Skin-On-Frame hobie cat style? Has it been done?

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    Default Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Newbie here. Sorry if this has been adressed before. I've been searching online and in the forums and haven't seen if anybody has done this. I've built a stitch-and-glue CLC kit kayak and recently a skin-on-frame canoe. I'm sold on skin-on-frame but am wondering if the reason it hasn't been done is because of the stress on each hull when you start to fly. I figured I'd double the number of ribs and add some extra stringers to beef it up. If there is a thread on this I would love to read it. I'm itching for my next project and this idea, or a sailing canoe with outriggers, is where I'm headed. I'm thinking of a 15'5" made of cypress (I can get clear 16' lengths around here New Orleans, LA) with laminated cross beams. Thoughts, ideas?

    proudfoot
    Last edited by proudfoot; 06-22-2011 at 11:56 PM.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Can't answer your question, bur I was wondering if the Wharram Hitia 14 would be a candidate:

    "Smooth seas do not make skillful sailors". African Proverb

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    If ur interested in anything with outriggers, check out the outfitted thread.

    As far as sof goes, i too am sold on it for most kinds of small boats. Except sailing multihulls. The long narrow hulls of a multi have to constantly fight flex and twist, and as such are always built as stiff as possible. The whole point of sof is to be flexible, so it is not an ideal medium for sailing multis imho. It has been done however, a sof outfitted sailing canoe was built and posted on by... his name escapes me, but he's a terrific sof kayak builder with his own site and lots of great stories on that site... someone will chip in here im sure... but the point is, he has a story of how he launched and sailed the boat. But i have never seen another report of it online. So it can be done, but may not be a great platform. My 2 cents.
    “The difference between an adventurer and anybody else is that the youthful embrace of discovery, of self or of the world, is not muted by the responsibilities or the safety-catches of maturity.” Jonathan Borgais

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    I remember now... google cape falcon kayak
    “The difference between an adventurer and anybody else is that the youthful embrace of discovery, of self or of the world, is not muted by the responsibilities or the safety-catches of maturity.” Jonathan Borgais

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Quote Originally Posted by peterchech View Post
    I remember now... google cape falcon kayak
    I think that boat might have worked well if it weren't for the requirement of surf launches through Oregon surf. If you had calmer conditions for launch, it might have been a good candidate. I think the Yost style SOF might also be a good possibility.

    I don't think catamarans would be as good a candidate though as platform rigidity is important to it's success.

    Dan

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    You have crossbars that hold the whole thing together. The crossbars have to be securely and rigidly attached to your hulls. I doubt you could find enough meat on an SOF hull to have a mechanically adequate attachment.
    There is a plan for a small wood catamaran on this site
    http://www.svensons.com/boat/
    Check out how involved the crossbar attachments are.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Thanks for the feedback. It seems from the comments that the loading on the frames are the issue, as I suspected. Perhaps a hybrid system, with multiple bulkheads and longitudinal rails running through and linking the bulkheads together might work. Or X's running between the bulkheads at angles. A plywood deck perhaps? hhhmmmmm.... it's starting to get complicated, but I like the idea. It seems like meat can be added to the frames easily, it's just a tradeoff as to whether the weight gains from SOF are maintained compared to Stitch-and-glue. I have really been enjoying building SOF without the hassle of epoxy and fiberglass. Thanks for the comments!

    proudfoot

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Inflatable sailing catamarans have done well, at least the small ones, so why not SOF? You may also check out "Tim Anderson's Home Away from Home" webpage and click on the Guatemala cruise with a ~14 foot long SOF proa (V-hull shape). He built that on the beach from parts carried on airline-OK suitcases (i.e. no piece longer than 38 inches) and some local planks, covered it in some heat-weldable fabric he had scavenged int he States (welded with a laundry iron, I seem to recall), and cruised that coast for ~3 weeks. It went through some stern sailing (even brought his girlfriend along for a week), and the cruise ended in a rough surf landing that splintered the boat, but hell, it worked pretty well before that! That was a rough surf he came through (there's a photo). -- Wade

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Quote Originally Posted by peterchech View Post
    ...It has been done however, a sof outfitted sailing canoe was built and posted on by... his name escapes me, but he's a terrific sof kayak builder with his own site and lots of great stories on that site... someone will chip in here im sure... .
    --- Besides the Cape Falcon outrigger SOF, there was also Harvey Golden the traditional kayak expert, who built a SOF shunting crab-claw proa that mimicked traditional Pacific look (and even used a low-bouyancy ama, maybe a log ama). Nice looking boat! From a short distance it looked like dug-out Pacific canoe. I don't recall that he had problems with the SOF design as such, but learning to shunt a scaled-down proa in cold northern water was a very wet experience for him :-) -- Wade

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Tim Shaw has an interesting SOF outrigger canoe which he built that has a sail rig, or at least it will have when he gets it done. I shipped him a sail for it a couple months ago that was sort of a hybrid lug/settee sail that he and I brainstormed-out. I think the boat was featured on a thread here on the forum a while back.

    As for this one, the farther away you get from the Hobie Cat concept, the better in my opinion. My last Hobie was an old H-14 that I rebuilt and having sailed it in some high winds and big waves, the amount of stress that such a high-aspect rig can put on the hull is pretty crazy. There were times when the whole boat would shoot off the top of the wave and slam down, jerking the whole rig back and forth while I prayed that the shrouds wouldn't break. Worrying about the hulls folding up at the same time wouldn't be much fun, so I'd be careful about overloading the sailplan.

    I don't think this is the final version of the plan for Tim's boat, but it's pretty close to what we ended up with.
    http://webpages.charter.net/tbradsha...s/!SETTEES.PDF

    Tim's blog
    http://www.chineblog.com/chine-blogs...sof_outrigger/

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    If stiffness is lacking, check out Platt Monfort's system of stiffening up an SOF hull.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Ply decks would be necessary i think at the very least.

    I doubt there's a weight advantage. Tortured ply or even s&g can probably be made about the same weight as the sof would be so i dont see any advantage, except in cost and building time...
    “The difference between an adventurer and anybody else is that the youthful embrace of discovery, of self or of the world, is not muted by the responsibilities or the safety-catches of maturity.” Jonathan Borgais

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    Default Something like this ?

    Quote Originally Posted by proudfoot View Post
    Newbie here. Sorry if this has been adressed before. I've been searching online and in the forums and haven't seen if anybody has done this. I've built a stitch-and-glue CLC kit kayak and recently a skin-on-frame canoe. I'm sold on skin-on-frame but am wondering if the reason it hasn't been done is because of the stress on each hull when you start to fly. I figured I'd double the number of ribs and add some extra stringers to beef it up. If there is a thread on this I would love to read it. I'm itching for my next project and this idea, or a sailing canoe with outriggers, is where I'm headed. I'm thinking of a 15'5" made of cypress (I can get clear 16' lengths around here New Orleans, LA) with laminated cross beams. Thoughts, ideas?

    proudfoot
    Hi,

    Have a look at this.




    http://www.faltbootbasteln.de/scalare25.jpg

    http://www.faltbootbasteln.de/fbb-fa...n-scalare.html

    So it has been done. However, at 250 kg, the usual advantge of SOF seems to have been lost...

    Cheers,

    Viktor

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    MY German is way too rusty, but from what I gather, it's basically a "Hobie-Klepper" that folds up! Quite an engineering project.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    My two cents, of course, but I'd be much more inclined to build an inflatable cat that makes use of drop stitch fabric and build a pair of dory style hulls which, when inflated, will be rock hard and able to take a huge amount of loading while remaining stiff (air pressure is a bad ass force and can yield impressive power when the overall form is designed correctly. I'd still follow Todd's suggestion that you tone-down the rig, if only because of an easier beast to handle when assembling and doing the take-down. Big rigs do impart big loads and to get decent speed out of the little girl, you can get by with quite a bit less than one sees on the typical beach cat. Even with a smaller rig, you will still smoke the monohulls of equivalent use and size.... and you can roll it up and stuff it in the closet when you get home, well, minus the rig which will still require a mast to be considered, even when smaller (righting moment considerations)

    Most of all, have fun with whatever you do and do listen to those who have been there before you. They have lots of great ideas, as well as cautionary comments.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Hi Todd,

    It is indeed!
    They were built in the 1960s in Wismar, East-Germany, by a company called MTW.
    They seem to be exceedingly rare (the German website where I found it called it the "Blue Mauritius" of the folding boats).

    Here is a whole slide show of the one above, which is in excellent condition, but possibly the only one still in existence.

    http://picasaweb.google.com/Enno0505/FaltkatamaranSCALARE250#


    Viktor

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Quote Originally Posted by Chris Ostlind View Post
    My two cents, of course, but I'd be much more inclined to build an inflatable cat that makes use of drop stitch fabric and build a pair of dory style hulls which, when inflated, will be rock hard and able to take a huge amount of loading while remaining stiff (air pressure is a bad ass force and can yield impressive power when the overall form is designed correctly. I'd still follow Todd's suggestion that you tone-down the rig, if only because of an easier beast to handle when assembling and doing the take-down. Big rigs do impart big loads and to get decent speed out of the little girl, you can get by with quite a bit less than one sees on the typical beach cat. Even with a smaller rig, you will still smoke the monohulls of equivalent use and size.... and you can roll it up and stuff it in the closet when you get home, well, minus the rig which will still require a mast to be considered, even when smaller (righting moment considerations)

    Most of all, have fun with whatever you do and do listen to those who have been there before you. They have lots of great ideas, as well as cautionary comments.
    I agree very much with Chris's approach - some combination of stringers and inflated tubes will have a better chance of absorbing and disapating the considerable shock/repetitive flex loadings that will occur if/when you end up going fast in waves. Have a look at hybrid kayak hull construction Tom Yost used in his Sonnet hybrid inflatable kayak.

    I'd be inclined also to start by building a single hull and fitting it out as a trimaran/ double outrigger canoe with inflatable amas. It would get you on the water and give you a chance to resolve hull and rig issues before you consider going on to a catamaran. A good thing about SOF is you can often pull it apart and use most of the bits in a re-build.

    Ian

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Given the speed of a Hobie Cat and the fragility of lightweight skin-on-frame craft (Dave Gentry posted a thread on the destruction of one of his boats on hitting a rock), it seems like a bad combination. The fabric skin could be strengthened with layers of glass cloth and epoxy, but then you're just building a custom Hobie Cat with a wood frame.

    The problem with inflatable hulls is to get a decent shape. The cheap ones (Sea Eagle) are not very hydrodynamic. I had an obsession with the type a few years ago and found some very sporty looking sailcats from Russia and also some from Germany. There was a flat-out racing version being made in England.

    The common elements were rigid bows, some means to get an angular, rather than tubular cross-section, a rigid lightweight frame for the rudders and tensioned rigging, and inflatable components built for very high air pressure.

    Don't really care to repeat the search, but I'll see if I can find any of the websites.

    If you need custom inflatable cat tubes made in the US, I recommend an old friend: Jack Kloepfer, at Jack's Plastic Welding http://www.jpwinc.com/
    Last edited by Chip-skiff; 06-24-2011 at 07:17 PM.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    It's not just rocks either. If you are shooting for something along the lines of a beach cat, you should pretty well be able to literially stand and bounce, or jump up and down, on any part of the boat (or get thrown onto it at 15-20 knots) without it breaking. When a cat flips, you usually wind up about 8' above the water, but you often don't stay there long and where you land, or what you land on when you come down, is often out of your control. One of the things that has always made Hobies successful is that they're damned hard to break.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Quote Originally Posted by Chip-skiff View Post
    ...If you need custom inflatable cat tubes made in the US, I recommend an old friend: Jack Kloepfer, at Jack's Plastic Welding http://www.jpwinc.com/
    --- Jack's Plastic Welding made my two 16-foot inflatable amas for WaterTribe, Inc. with Steve Isaac's design input. They worked great for my little trimaran conversion and some rough stuff in the Everglades Challenge -- they were even a little underinflated -- so inflatables do get my vote. The only thing is, a SOF would have a more graceful failure-mode, I should think. My inflatables had two air chambers each for safety, but I didn't kid myself about how much fun it would be getting back to shore with a half-deflated ama. FWIW the guy called "Crazy Russian" in Watertribe sailed his old Russian inflatable catamaran for years in the EC and did well. -- Wade

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    I agree with your take on Jack. He's a great guy who also has a unique sense of humor that is very much appreciated.

    Another very interesting guy in the inflatable trade is Atilla Szilagyi, the owner of Custom Inflatables in West Virginia http://www.tseeker.com/index.html Atilla has built many dozens of pairs of inflatable tubes for kayakers and canoeists who were rigging their boats for sailing. His products and workmanship are first rate. Perhaps the best part of dealing with Atilla, is that he already has many of the shapes incorporated in his existing boats, so all you have to do is tell him which component of one of his boats you are looking for and he can break that out a singular product for you and affix lashing points, etc. wherever you want them. For instance, when I do a sailing canoe rig for a client, I spec the tubes from the boats in his ThrillKat line, http://www.tseeker.com/html/thrillkat_family.html for the stowable amas.

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    Wow! Thanks for all the design ideas! That german built cat is quite beautiful, but does look pretty bulky. I think I'm going to try something along those lines, but make it a little lighter. I'll not be doing anything crazy with it, but would like to see how it handles a small sail and move up from there. This boat will mainly be used in Lake Pontchartrain in New Orleans, and areas surrounding. It gets rough sometimes, but I'm not going to push my luck if it's too rough. Nice sandy beach launches. Still have to skin this other boat and design this one. My main goal with this next boat is to try and build it "by eye". The less I use a tape measure, the better. Thanks again for all the input. I'll update more when I get it going. So many ideas, so little time.

    proudfoot

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    Default Re: Catamaran Skin-On-Frame hobie cat style? Has it been done?

    That East German cat was a one way model. You built all the pieces and when the Stazi weren't looking assembled it and made a dash across the Baltic to Sweden. If I'm not mistaken one asylum seeker got out using a home made balloon. In fact he had to make two becouse the first one came down before it had passed over the border.
    Last edited by Cuyahoga Chuck; 06-25-2011 at 10:12 PM.

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