Another Biplane (Simpson)

  • 28 Jun 2020 08:46
    Reply # 9065258 on 9057743
    Anonymous wrote:

    Here's a lengthy write up of Dragon Wings/Puff, one of the earliest biplane cats, I think.

    There's plenty about China Moon  in Newsletters 36, 40 and 43 and maybe others.

    I remember seeing a biplane cat 35+ years ago down in the Algarve, first time I'd seen one, totally baffled as I couldn't work out how it worked!
  • 27 Jun 2020 16:05
    Reply # 9064046 on 9057515

    David:

        It's been awhile since I read the article on Dragon Wings over at Duckworks, so I reread it the other day.  I always tend to pick up more details on a later reread.     What is striking is how similar his design parameters and priorities are to what mine would be.  Performance low on the list compared to livability, functionality, low upkeep cost, ease of sailing single handed, and payload.  I differ mainly in scale.... I have no interest in accommodating 4 people, probably rarely more than two, and often single handed.   He also places a high value on the large expanse of open deck... which is fine in daytime good weather, but to me good enclosed shelter with all around view and ease of access to the cockpit with sheets and halyards and steering gear, and the ability to access at least one hull (galley & head) internally, has a higher priority.  Having spent many years in the PNW, where it rains incessantly, and the storms march down the coast from the gulf of A, one after another, protection  is important to me.... Odd since he's from Port Angeles. 

           He decreased the length to beam ratio to achieve more load capacity and better liveabillity / space.   I agree with this.... keep the package as small or rather compact as possible.  The other alternative is to do what Pete did with Oryx, and add a generous chine at deck level, and or push the deck cabins space out onto the deck for counter space, and add some LWL length.  Adding footage need not add a lot of additional cost except that everybody wants to scale everything else up to go along.  A 30' cat built on hulls stretched to say 36', if you scale nothing else up probably makes the most sense as the increased LWL adds flotation, improves ride, and increases hull speed.   But it does add 20% more hull and deck to maintain and paint, where making it fatter adds almost nothing.

         These are the trade offs designers make, and their priorities differ from mine, so their designs never quite match what I want. 


          His inboard daggerboards are similar to the drawings of Kohler's that I included in my previous post... in concept at least, and would allow daggers to be easily added far enough aft to place the masts aft of where they would be in a typical junk rig conversion.   This would have several advantages. 

          Talk is cheap.......... I've concluded that I won't be building another boat, much less designing and building.

                                                               H.W.

  • 26 Jun 2020 22:39
    Reply # 9063011 on 9059665
    Anonymous wrote:

    David:

         I wonder realistically how much more a junk rig weighs than a Bermuda rig with all the standing rigging, winches, heavier sails, etc.   The taller mast of a typical Bermuda rig will put at least part of the sail into a better wind gradient, but it all adds up to considerable weight if you look beyond the mast itself.     There is no doubt that a biplane rig with two shorter masts will be heavier for the amount of drive it is able to achieve, though shorter masts can be lighter than taller ones.  It looks to me like the mast weight itself is the main consideration, and the fact that is further forward.... 


    I worked out by some fairly quick and rough calculations that the weight of a bi-plane junk rig on my little cat would be at least 3 times the weight of the rig I have ended up doing. Of course on such a small simple boat there are no winches and other associated hardware. All my standing rigging will be Dyneema and everything else is going to me minimised, simplified, and always going for the light weight options. 

    Having said that there are not many bi- plane rigged catamarans around I was completely ignoring the fact that the designer of my own boat, Bernd Kohler, has a number of Bi- plane rig designs, and of course my own inspiration came from the little voyaging catamaran, Miss Cindy, which had a lugsail bi- plane rig. I did not realise until after purchasing the plans for my boat that the design was not particularly suited to a bi- plane rig. Never mind, I am very happy with the boat I have ended up with and I am looking forward to learning how to use the new high aspect gaff main rig.

  • 25 Jun 2020 17:27
    Reply # 9059821 on 9057515

    Howard,

    Dragon Wings was designed by the owner / builder particularly for a biplane junk.  

    I have lifted Orxy masts, it is actually quite light .

    Thomas Firth Jones last cat started with a biplane rig, though he did not stick with it.

    There are surprisingly more biplane cats out there than you would expect, though still not many...ie enough.  Here is one, ok not JR, looks quite quick

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  • 25 Jun 2020 16:21
    Reply # 9059665 on 9057515

    David:

         I wonder realistically how much more a junk rig weighs than a Bermuda rig with all the standing rigging, winches, heavier sails, etc.   The taller mast of a typical Bermuda rig will put at least part of the sail into a better wind gradient, but it all adds up to considerable weight if you look beyond the mast itself.     There is no doubt that a biplane rig with two shorter masts will be heavier for the amount of drive it is able to achieve, though shorter masts can be lighter than taller ones.  It looks to me like the mast weight itself is the main consideration, and the fact that is further forward.... which itself is not insignificant.  


         Several articles I've encountered suggest that the further aft the rig is on a catamaran the better.  This suggests that a cat designed specifically for a junk rig from the keel up is what is really needed, but almost no boats are designed ... North Atlantic 29 is the only one that comes to mind at the moment. 

         logically a standard catamaran with a bridge deck cabin could be built to have the masts set at the forward end of the main hull cabins or the aft end of the cabin forward of that.   The mast could be offset a foot or so inboard rather than hull stepped to allow access forward, and utilize the bridge deck cabin top as part of it's supporting structure.  The keel or daggerboard would be changed to move the CLR aft.  The rig would be designed for the maximum practical forward balance, which it would seem would limit your choices to a split rig or maybe a soft wingsail... I don't know what the balance limits are.   If the boat were designed as a fractional rig, the masts could be aligned according to the original location, otherwise underwater "compensation" would be needed.

         That compensation in CLR could take the form of a different location for the daggerboard, a change in the keel, or even the addition of a board.   I'm thinking of what Bernd Kohler calls "luff boards", which are foils.. like a daggerboard mounted to the inboard side of the hulls on a pivot that fold back like a centerboard.   Drawings below from his web site.  These were designed with the KD 860 in mind.

         The huge problem with multihulls is weight...... light weight is desirable, and it's a balancing act between bridge deck clearance and windage.... it's all driven by the obsession people have with speed.  You want to carry load, you need displacement which equals drag, which means a larger rig and a larger boat.  When  you look at multihull designs, they tend in two directions.  One is light weight minimalist speedsters, and the other is heavy condomaran pigs.  The design that most appeals to me has inadequate payload due to the desire for performance.  Payload is sufficient for typical use, but not for serious voyaging.  People never seem to include everything they should in payload... they "cheat" a lot.  The numbers sound "generous", but when you start counting galley equipment, ground tackle, safety equipment, spares, tools, food, fuel, water, clothing bedding, electronics, dinghy, watermaker, batteries, charging system, scuba bottles propane bottles, etc.... that .9 ton gets gobbled up very rapidly.......... I said most people "cheat".... really they conveniently overlook things.  A ton sounds like a lot... but I'm here to tell you it isn't!

         When I was looking at building.... and I'm not anymore because of time and cost, and the simple fact that buying something someone else has built makes far more economic sense and time sense... though you have to settle for something less than "ideal", I was looking at the lightest possible construction methods... infused foam sandwich. Money spent up front to build light pays dividends for the life of the boat.... It means a smaller, less expensive boat to own and maintain.   A win win situation.   "pay forward" they say.




                                                                              H.W.





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  • 24 Jun 2020 20:41
    Reply # 9057747 on 9057515
    Anonymous wrote:

    My interest is in multihulls, and it seems that there are very few junk rigged voyaging  type multihulls... Oryx, a few Wharrams, Bunny Smith's Dragonfly.  James Wharram had some negative things to say about junk rigs on cats after they'd put a few on Wharrams.... I don't remember the exact issue, and can't find the quote.  

    Here are photos of a Simpson  40, that is biplane rigged.  First I've seen of this boat names Seadragon and based in Brisbane.  Very nice looking boat.   From a for sale listing 9 years ago.   There seem to be no other photos of this boat....


        It would be nice if owners of boats like these would do write ups... they all seem to be too busy sailing........... Imagine that  ;-)


                                                             H.W.

    There seems to be really not that many bi-plane rigged catamarans out there. I have some friends who have a very successful, ocean proven bi-plane rig on a 15 m catamaran. This consists of a wing mast in each hull with a fully batten mainsail only on each mast. I have seen several junk rig bi-plane cats. Orxy for example, plus a local junk rig Tiki 38 Wharram. There is no reason at all why a junk bi-plane rig will not be successful and easy to control. But as I have learned with my own little catamaran project, now nearing completion, the weight of the spars required for a free standing junk rig on a small catamaran especially can be a difficult work around. If I was going to build again I would aim for a catamaran of about 7 to 8 meters, with plenty of buoyancy forward, and aim to put on a David Tyler Weaverbird type rig in each hull. I think that would make for a successful catamaran bi-plane junk rig.
    Last modified: 24 Jun 2020 20:42 | Anonymous member
  • 24 Jun 2020 20:40
    Reply # 9057743 on 9057515

    Here's a lengthy write up of Dragon Wings/Puff, one of the earliest biplane cats, I think.

    There's plenty about China Moon  in Newsletters 36, 40 and 43 and maybe others.

  • 24 Jun 2020 19:04
    Message # 9057515

    My interest is in multihulls, and it seems that there are very few junk rigged voyaging  type multihulls... Oryx, a few Wharrams, Bunny Smith's Dragonfly.  James Wharram had some negative things to say about junk rigs on cats after they'd put a few on Wharrams.... I don't remember the exact issue, and can't find the quote.  

    Here are photos of a Simpson  40, that is biplane rigged.  First I've seen of this boat names Seadragon and based in Brisbane.  Very nice looking boat.   From a for sale listing 9 years ago.   There seem to be no other photos of this boat....


        It would be nice if owners of boats like these would do write ups... they all seem to be too busy sailing........... Imagine that  ;-)


                                                             H.W.

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