Rob
I retire in August but I am having one more tilt at the Murray later in the year at the younger end of the oldest age group so I get the best possible age allowance. I plan to get fit for it and am building a new boat. It is a 6m version of Donna's boat with a few improvements based on what I learnt building that one. One change structurally is use of 120gsm cloth on the inside of the panels and 270gsm on the outside. Given that panels fail first on the compression side and are more prone to damage on the outside I figure this gives better use of the glass and necessary weight.
The proa rendering is a concept for a test model for something larger where it would not be an option to gain much from moving crew weight. If built it would have room in the ww hull for bunks under the deck.
The wing shaft has bury in substantial deck structure. It is not apparent in the view I provided but the deck is 300mm deep.
I have not gone into a lot of detail on how control surfaces would be operated. The biggest issue I see is raising the rudders rather than steering them. First thought for steering are tie rods from a pivot arm under the deck. The rudders are bi-directional. They do not need independent control. My view is that the leading rudder would be likely to ventilate once the lw hull is planing.
The dagger board would be lowered and raised from the cockpit of the ww hull with reeving through or winch in the deck structure. Aim would be to have neutral buoyancy and smooth guides so adjusting forces are low. It would need to be held down as well.
The centreboard is going to hit first in most circumstances. There would be progressive modes of release or, ultimately, failure before the hull was damaged. The rudders would be mounted in tapering wells. They can have a front edge taper to give some initial lift on a solid item. Again there would be progressive modes of failure.
The image does not make it clear but there is rough fairing on the deck and tower. This was the first pass so not much finessing in this detail. I am unable to accurately quantify the windage on the hulls but obviously there is advantage in having faired shape both from frontal and sideways. The most important aspect is to keep panel areas low.
The shear is a few seconds work with the intention of it fitting under the deck on the trailer. There is no need for the same on the windward side of the cockpit but then I have not given any thought to how the boat is boarded. The deck and cross beams are quite high. The floor in the ww hull would be above water level so it can drain.
The wing is symmetrical with a 12% thick section. 8% camber and 0.25% radius leading and trailing edge. This section has a maximum Cl of 1.6. The wing I have started with is 7m high and 10.5sq.m. I have only ever built wings for model boats so have not gone into any design detail. Weight estimate is based on using thin foam sandwich for the skin. I have not shown it in the rendering but I would consider using a tail foil to control the AoA of the wing. With this it would be possible to luff the wing without any flutter and take advantage of the very low Cd (.007) at zero lift rather than having to reef. The drag is less than a standing mast. The complexity with this is that the tail has to switch through 180 degrees when shunting - something that would need thinking about.
I will build a boat for my own use but I still like the simplicity of straight solar and it would do the things I want to do but slower than a proa. The proa design was for someone else and has some development from what I was discussing with Dennis Cox. I have now been on a proa but but yet to sail on one.
Another little project with the catamaran Peccadillo gave some rewarding results over Easter. She won the Three Peaks race:
My contribution can be seen on the aft steps. There are two pedal thrusters with big black model aircraft props that fold down (they can use human power in the race). They only needed them for a couple of hours in the race but they could hold 2.5kts continuously on a 30 minute crew rotation. Not bad for less than 300W on an 8t boat.
I am presently making a test thruster with a 4kW electric motor for Peter's proa using the same size prop. It will not handle the full thrust that the motor can produce but it will be OK for a test. Should have results of that in a few weeks.
Rick
On 12/05/2011, at 9:48 AM, Rob Denney wrote:
Rick,
Awesome! When are you starting to build? Some comments and questions:
Why not move crew weight inboard in the light so the ww hull can be smaller?
What holds the wing up when caught aback?
Do you control the rudders with tillers?
How do you get past the mast to lift the daggerboard?
What happens to the board and rudders when you run aground?
Is there a benefit to fairing the bluff front to the bridge deck and tower?
Why the dip in the windward hull sheer? How does the tramp attach?
Any more detail on the wing? (area, section, panels, structure, controls, etc?)
Agree about the single daggerboard, not so sure about the two small rudders. The practicality of two big rudders is hard to beat. Look forward to seeing your solutions.
It should be noted that Rick is one of the smartest guys I know, and that if anyone can make a proa like this work, he is the most likely.
Gardner,
Glad you like the boat, hope the judges do too. Don't be shy about posting yours, you usually have some good ideas to study.
The 35K includes the design fee. The boat will be painted with cheap paint, prep and application should be less than a grand or so. We have not quoted for the rig as the mast as it is a telescoping wing section and the sail a possibly very cheap new idea. Looks like I will be building one for El so we can figure out the cost of the bigger one. A tube mast for this low rm boat would be maybe $15,000, plus half as much again for the sail, maybe. A schooner will be more expensive than a 2 part mast, but not by much. If the 60'ter is a ballestron, then it will be very similar. Outfitting is the cost of a piece of string. Easy enough to do once you make a list of what you need.
The removable bows are nothing special, bolts and captive nuts through solids in the bulkheads.
Most cost effective is probably for us or the US guys to build the panels and you put them together. Did anyone get any prices from the US guys? I will contact them about the WB boat if there is any US interest.
Rick Willoughby
03 9796 2415
0419 104 821