Open source 12-15m high performance/semi-cruising catamaran design

This is an open bridgedeck so the engineering is tough but the weight penalty is minor (maybe). Trying hard to minimize the complexity of control surfaces by raising the natural efficiency of the boat.
With enough computing power and active surfaces you could make a 4 m beam work but if things fail or wave heights exceed the design envelope then the design is going to work against you.
There must be some sweet spot where the basic boat is great and the active stuff provides the stability/comfort that allows you to keep driving.

 

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Have you considered using a centerboard mounted in a midship nacelle? It would fully retract clear of the water.You would only need one and they have been proven to work well.

 

What about a shallow scallop in the hull so the dagger sits flush on outside of hull, if you hit something it's a clean break from hull, kind of like some mfgs do their keeps, glued on,so they can break off without damage to hull

 

My thoughts

I like open source development -controlling IP is nearly impossible in this biz anyway -but I think that you need to do a much smaller proof of concept. The end goal can be the same but creation of a real boat that can be tested keeps the project focused. The development might be worthwhile, but just not appropriate for a large boat. Cruising cats are already very weight sensitive -this will be more so.

Why would you turn the lifting foils inward rather than outward?
The advantages to outward
1 Greater contribution to righting and greater damping of healing motion. Foils actually make thrust out of pitching as long as the AOA is less than ~14 deg.
2 Naturally deeper position on a healing boat -and your design has a problem getting the foil deep enough even before it gets major lift.
3 The housing, and deployment mechanisms of the vertical and horizontal foils pack close together and combine, rather than opposing and pinching off the narrow hull as you presently show.

My last thought is that the benefit of this concept is too subtle. The benefit is speed, reduced drag of reduced displacement vs increased induced drag and cost. My inclination is to make a design that can get the hull above the water and a hull that goes in and out of the water smoothly. A deep V instead of trying to minimize whetted surface area. If you are going to fly, then fly. If you are going to displace....

 

Good contributions skyak, thankyou.

I have considered outward rather than inward however once the boat is heeled- dont the foils then produce a component of lift to leeward rather than windward on inboard side? This was the main reason i initially opted for the inward position...

Also, the main reason for this is not just speed. Its equally important for the improved seakeeping characteristic which makes life at sea much more comfortable...

 

They most likely will have a small component to lee ~sine of the heel angle. Inward will also tilt with heel and in the same way your current dagger board has the same small component downward, increasing displacement. Bottom line, it is a small component and it is easy to calculate. So is the righting benefit from going outward vs inward

Are you aware that the lift of a horizontal foil falls off significantly around one cord length from the surface? If your hull is only a foot and a half deep and your foil is a foot wide you have no room to lift. It would be nice to use this effect to cushion ride height, but it's so close to the surface that the foil would breach frequently in rough seas. If comfort is as important as speed I think the single bent dagger board is the way to go for the simple reason that the horizontal part of the foil needs to stay deep in the water. My opinion of comfort is that big cats are already quite good so making a worthwhile improvement will be difficult.

 

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No, unless you design them that way. I think the forward position of the DSS-like foils is a bad idea on a cat for the reasons I mentioned earlier and that were just mentioned by Skyak. But you can design the foils to produce vertical lift at any angle of heel that suits you.

 

Fixed horizontal lifting foils for a multihull-(Kelsal, Grainger or?) :

 

a few more renders showing the sail plan and interior.
So far the total surface area of all panels shown in the render is 336sqm. There is more to add but its getting close to having all structural panels included.
Allowing for 10% wastage - thats 129 sheets of PVC foam. I have another spreadsheet which will calculate the cost of infusing all these panels.
Its designed to be 100% flat panel construction, infused foam core e/glass construction with carbon reinforcements to beams foils and rudders. Ill get to the weights soon...
Total mast length = 20m
Mainsail = 90m^2.
Genoa is 51m^2

 

Ive attached the 3D files in IGES and Rhino 3dm to this post so others may have a go at it!
I encourage anyone who is interested to have a go at this- show us your ideas now you have a baseline, interior decorators and designers - pick something and have a go!
PS - this is a work in progress so there may be (will be) some problems/mistakes in some of the surfaces however the general geometry is there.
Hydrostatics to go with this;

 

Dang this is a SMALL boat, I will come help you build it, will take about 2 weeks!!! lol
If anyone wants here is a Rhino file with basic shape. The Rhino file posted above opens as a single layer, this might save you some time. The V is really pronounced in mine, don't know why, if somebody wants to tell me how to fix that, would be nice )))

Actually I like it, I want to see how interior unfolds )

 

Staying pretty faithful to the design, only a slight mod to the coach roof and door which you will need to open a a hatch in coachroof to get into or do some pretty serious ducking. I will work on interiors next, I think the hull from the coachroof start to the end of the bridgedeck should be opened for storage and a seat. I will do that version later.

 

Looks great jorge - rhino certainly produces a nicer render doesnt it!

The entry into the cabin requires some lateral thinking, first you cut away a small area in the deck just in front of the door to create a step down. Then once through the door theres another step down before reaching the floor level included in the original drawing.
At this interior floor level, there should be enough internal volume to create a galley kitchen with benches down both sides- thats why the bulkheads are cut away in that funny shape. But your welcome experiment with whatever layout you can make work!
Yes its a small boat - everything so far has been designed to keep costs and building time down...

 

Yeah Rhino is a pretty impressive program especially when you consider price. I think you might build this boat for around $50K )) Funny that they sell the SIG in the millions.

 

No way jorge... just the foam glass and resin alone will be close to $50k.
And the rig and sails is over $50k, main sail alone circa $10k.
And the rest of the fit out...???
I doubt it could be home built done under $200k.