The Black Swan Project
I like your idea a lot, Othmar. And yes, I’d worry about slamming the pram bow in big seas, but it might make a very cool lake racer. Very clear illustrations, also. BTW, is that a yacht design 3D program you are using, and if so, which one?
Curiously, the laws of planing are almost the opposite of the laws for fast displacement hulls. Given the same planing surface area, the short and wide planing hull will have less resistance than the long and narrow hull. They are more like airplane wings than hulls. This is one reason floatplane floats are stepped. The downside of stepped hulls is that they are terrible off plane, so not really applicable to a cruising sharpie.
You can always attach a lifting foil to the rudder. If nothing else it makes for a really cool bow ornament when the rudder is up. :D
Hey, check it! SA has an awesome pic of Red Herring on their home page today! Picture that with an outrigger…
What a cool looking boat! the 55’ ketch Red Herring at the start of the Ida Lewis Yacht Club Distance Race in Newport, RI from our friend mstrsail.
Due to the fact that in Black Swan Project “all is allowed” I get a special idea. Why ‘fat’ performant dinghies and monohulls have a chance of planning? They have a slim bow for less wave resistance and a wide stern as ‘counter surface’, otherwise the stern sinks and slow down the boat. A proa has two bows, as we know. To make it wider for a chance of planning, the wave resistance rises. What’s to do?
My crazy idea was to combine a wave piercer with a sharpie. When speed rises up, the bow lifts (if the rig helps), and the stern goes down ... until my sharpie overhang reaches the water, and works like a wide stern. I know it’s a daring statment, but who knows ... perhaps it works?
Othmar
Here in Oregon there’s a famous power design known as the Calkins Bartender. It’s a double ended V hull with planing strakes at the rear. The Coast guard actually has used the design for a life boat. It’s know for being able to keep going at speed comfortably when traditional planing hulls are slamming the crews teeth out.
http://www.bartenderboats.com/index.html
Also, Malcom Tennant designs high speed power displacement catamarans with a pointed stern under the water line and then a step to keep it from squatting at higher speed. don’t have the link handy for that.
When I look at doing my “box keel” proa, i’m always wondering how close to bring the step to the waterline, and If I could possibly get some dynamic lift off of the step.
Fun train of thought.
Tom
You can always attach a lifting foil to the rudder. If nothing else it makes for a really cool bow ornament when the rudder is up. :D
Similar idea are realized at ‘Catri’ trimarans. In the beginning of 2000 I had a chance to go with such a boat for a short trip. Basically the ‘foils’ working well.
When I look at doing my “box keel” proa, i’m always wondering how close to bring the step to the waterline, and If I could possibly get some dynamic lift off of the step.
Tom
See picture of foldaway flaps below 😊
Very clear illustrations, also. BTW, is that a yacht design 3D program you are using, and if so, which one?
The program I used for my 3-D sketches is DelftShip. Basic version download for free.
I think the easiest way of achieving planing both directions without the excessive slaming from a scow-bow would be to have a large trim-tab that is lowered on the end thats becoming the new stern when shunting and the forward one would be lifted out of the water to clear most of the spray and waves.. The wide trim-tab could also hold the rudder. It could be slightly V-shaped, with an angle on each side of the hull..
I have been sketching on something like this for my surfboard-inspired planing proa.
Johannes.
For planing, you just need to make sure you have a sharp edge/chine at the stern to promote clean flow separation. I think a double ended sharpie style hull will ahcieve this fairly well without resorting to complicated flap arangements. It will be necessary, though, to ensure that the boat will trim down by the stern at planing speeds and I think that this is where the pantographing ama will come in handy. The lower CE schooner rig will also help.
A fine bow is not necessary for planing. The fine bows on todays high performance monohulls are to improve the performance in conditions other than planing conditions, and to improve upwind performance in waves. In light conditions the crew weight is moved forward to immerse the fine bow and lift the large surface areas of the stern sections out of the water. In planing conditions the crew moves well aft to lift the bow clear of the water so the the hull sits on the wide stern sections to provide a more efficient (higher aspect ratio) lifting surface. Neither the fine bow, nor the wide stern are absolutely necessary for a planing hull, but they do improve the overall efficiency if used correctly. With a double ended hull it is not possible optimise the bow and stern for their specific tasks (without moving parts) so a compromise is necessary.
Black Swan Progress Update
Here are some pics of the new model, hot off the press. He’s sailing the basement carpet at the moment, soon to be kissing the wild blue yonder. Seattle has a nice model test basin at the Center for Wooden Boats, it’s populated by R-class Pirate models, (Arrrr! class) I’m hoping to show them up.
You can see the slight curve of the bottom, a surfboard, really. I’m not relying on the hull for lateral resistance, though in the case of extreme shallows it would probably do. The point of the experiment is to provide an easily adjusted CLR and CG, that will 1) align the forces of wind and water and 2) permit planing, which equals 3) bat outa hell performance.
The ama is left open in places to allow for ballast, and I decided to cut a channel into the hull for the same reason, so it can be laden with “cargo” and see the result.
My next step is the rig. I’m going to go for a single sail on the model, the schooner rig is not necessary. If anyone has some insight or links into fabricating a proper model lug sail, I’m all ears!
LOA: 24"rectangular section hull
Hull beam: 3”
BOA: 14”
Ama Length: 16” with an equilateral triangle section
It looks really neat, Michael 😊
Dependent on size you could make a simple luggsail out of paper. I used spinnaker-cloth
Michael,
The model looks good. How long is it (I’m guessing about 800mm)?
I use drafting film for my model sails (mylar). For corner reinforcement patches I often just use duct tape. For most of the fittings I use stainless steel wire if I can get it (fishing tackle suppliers), but copper wire will do. I use either nylon fishing line or nylon builders line for sheets and other adjustable lines.
A neat way of making cleats is to bend the end of a piece of wire back on itself and squeeze it tight at the bend but spread it out a bit away from the bend. The length of bit you bend back is, say, 10mm. This forms a vee notch which you can jamb the sheet in.
The model is 24” long. I know, I know, it’s supposed to be as big as possible but the pond it sails in is pretty small, and if this one shows some promise I’ll build a larger one. Thanks for the velum idea for sails - I think I have some of that lying around.
Black Swan Progress Update
My next step is the rig. I’m going to go for a single sail on the model, the schooner rig is not necessary. If anyone has some insight or links into fabricating a proper model lug sail, I’m all ears!
Hello Michael,
here ist a link to a site for making sails. It’s made for making IOM sails, but works for every sail. Visit your local sailmaker and get some leftover spinaker cloth and some double sidet sticky tape for glueing the whole thing together. Small pieces of spinnaker repair tape makes the reinforcements for the corners and the luff. Secure the edges with a little melting with the lighter. The trailing edge has no extra reinforcement, make the holes for the lines with a hot nail or a soldering iron.
Get the rest from the manual
http://www.rcsails.com/sailmaking.html
Cheers, Michel
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