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Old 16-08-2007, 13:21   #46
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Beau,

Well done, mate. I applaud anyone who can eschew traditional thinking and has the imagination and guts to see a dream through to reality. I look forward to the reports from your sea trials. Fair winds,

Kevin
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Old 16-08-2007, 15:31   #47
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i cant agree more especially considering the negative feedback he got from here when he put forward his ideas initially, so how is your website coming along then beau
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Old 16-08-2007, 16:48   #48
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How long before she goes in Beau?

I'm in CQ at the moment, and will be for 3 month's but if you end up here I'd love to do a lap around the Keppels. ??

At the rate your going that would be likely would'nt it ?????

Dave
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Old 16-08-2007, 19:32   #49
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That is pretty cool, I have flollowed this thread for a few days and must admit, when I saw the fist photos of the hulls welded up, I was OMG, is this guy NUTS?

The newer photos assemebled with paint I'm like, hmm...that looks pretty cool, even if it is a stinkpotter!!

I would still like to see a rudder for sailing, sorry, just my MHO!
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Old 16-08-2007, 20:25   #50
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Originally Posted by cat man do
How long before she goes in Beau?

I'm in CQ at the moment, and will be for 3 month's but if you end up here I'd love to do a lap around the Keppels. ??

At the rate your going that would be likely would'nt it ?????

Dave
Definitely let us know (if you feel up to a public launch) - that's three nominal Brisbanites here at least.
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Old 17-08-2007, 01:48   #51
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Thank you everybody for your support and your comments.
The design is based on what I believe is a suitable cruising boat for the tropics.
From my experience, a lot of the weather is flat calm or under 10 knots of wind, most of the time and to sail under these conditions is ridiculous.
The other extreme is 25-30 knots of wind and in these conditions, motoring with a boat designed for motoring offers a lot more control, as long as you have the speed potential to say ahead of the waves.

Sailing is great, but most of the time the conditions are not ideal for sailing and the engine set up in most yachts is also not ideal for motoring and pushing an monohull type displacement hull can use a lot of fuel.

When the conditions are ideal for sailing, I will sail, downwind or on a reach, to save on fuel, and yes I WILL need a rudder, but No daggerboards.

The type of hull I have developed has very lower friction along the sides (and bottom) and NO wave making resistance, which means I can motor at 10 knots using only 20 hp ( a 30 hp outboard run at 2/3 throttle)

Also I do not believe this hull will suffer from "overloading" like other narrow hull multihulls and that could be the greatest advantage of all.
I will keep you posted.

regards,
Beau
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Old 17-08-2007, 06:41   #52
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Beau,

Do you have any photos/video of your prototypes making way? I'm intrigued by the notion that there's no bow wave produced. I have an idea why it would work, but need an image to confirm the assumption.

Kevin
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Old 17-08-2007, 09:21   #53
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Looks cool, are you going to put some tramps on her?
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Old 17-08-2007, 10:50   #54
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Also I do not believe this hull will suffer from "overloading" like other narrow hull multihulls and that could be the greatest advantage of all.
One of the advantages of a square hull form that I don't think has been touched on here is that as you load it down the wetted surface increases at a lower rate than a rounded hull. The upshot is less performance penalty than a round hull as it is loaded.

By the way, bitchin boat!

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Old 17-08-2007, 15:52   #55
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Kevin,
I didn't take photo's just a lot of observation.
I was initially intriged by a 26ft telstar trimaran that I owned some years ago. It had a relatively narrow main hull and would motor at 10 knots with a 10 hp outboard. Previously I had a 30 ft monohull which motored at 6 knots with a 20 hp motor.

I put a 25 hp outboard on the Telstar to see what it would "do" and I got 15 knots. I then went and bought a 35 hp outboard and mounted it on the Telstar, however at 16 knots a bow wave started to form and we started climbing uphill . never got any more than 16 knots.

But it all made me think,why?

Nowdays it is well known particularly on commercial catamaran ferries that a 16-1 length to beam produces NO bow wave. I went on one last week and we were doing 30 knots, no planning and no bow wave.

16-1 is not suitable for boats under 150 ft long.

I started experimenting with 15 ft plywood prototypes, in all, I built five.
I found that if the angle of entry at the bow was small and you continued back (wedge shaped) with that same angle NO turbulence (eddys) was produced along the sides of the hull.
It is the friction or turbulence which produces the bow wave. I kept experimenting until I found the best angle of entry.

After that it was a case of making that concept into a practical boat.

With my design the hull is immersed at all times. Particularly the bow. The stern has large trim tabs to keep the bow submersed most of the time.
The sides of the hull are also vertical, which reduces spray, the bow is longer than "normal" for increased buoyancy.

IT IS NOT THE INCREASED WETTED SURFACE THAT SLOWS DOWN "OVERLOADED" MULTIHULLS.
I have proved that in tests.
It is the wider beam of the immersed hull producing the increased turbulence associated with the formation of a bow wave at a lower speed

YES, increased wetted surface plays a part in this speed reduction but it is not the main factor.
It is easy to prove, because it is speed related.
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Old 17-08-2007, 19:39   #56
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Steve Shidler Revolution Trimaran
this looks like it may have been one of your prototypes beau
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Old 17-08-2007, 19:50   #57
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Originally Posted by beau
Nowdays it is well known particularly on commercial catamaran ferries that a 16-1 length to beam produces NO bow wave. I went on one last week and we were doing 30 knots, no planning and no bow wave.
I imagine most commercial cat ferries are wave-piercers; your design seems similar to wave-piercing designs, in many respects. At first it seems counter-intuitive when you consider the most aerodynamic shape is an aerofoil shape, it would make sense that traditional hull-shapes, essentially being aerofoil-shaped, would produce the least drag in water. This may be true where the form is completely surrounded by water, as in a submarine. As you have already said, at the surface wave-generation causes the most drag, and aerofoil shapes create waves. I figure that as water is "reflected" off the hull it will move away at about the boat's speed; since traditional hull forms get exponentially beamier as they advance, the hull essentially overruns the incipient wave front, piling up on it. With your design, the beam increases linearly, so the advancing hull does not catch up with the reflected wave. So you don't have a bow wave, but I imagine you have a well-defined and narrow stern-wave (wake). Looking forward to seeing pics of your new boat not making waves

Kevin
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Old 18-08-2007, 04:10   #58
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It is interesting that you mention the stern wave.
At low speed under 10 knots the stern wave is quite pronounced and does seem to drag.
However as the water breaks from the stern, above about ten knots, the stern waves flatten out. The boat seems to lift slightly and the speed improves significantly as if the boat has cast off the drag of the earlier stern wave. The boat is not planning but seems to enter a new phase.

What really is "wave piercing"?
All the hulls I have seen (like the endeavour etc) have parallel sides and essentially fit into the 16-1 rule
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Old 18-08-2007, 09:40   #59
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Beau,

Good on ya for continuing to update us on the progress of the boat. I am not a yacht designer or anything approaching knowledgeable on all the technical aspects of what you are doing, so I hope it all works on the water as you envision.

In a previous post you discussed the wire designed to reinforce the arms holding the amas in place. How do you deploy the wire and how do you "force" the amas into the open/closed position and keep them there?
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Old 18-08-2007, 17:07   #60
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Kevin,
One more thing I just remembered. The bow must be keep immersed and should be the deepest section of the hull in the water (which is why I have large trim tabs plus movable fuel ballast tanks fore and aft) Under ideal conditions the bottom is angled upward right to the stern. What this does is create a low pressure area which "SUCKS" part of the bow wave generating water, underneath the hull.
For example I have sprinkled a white powder into the water along the sides of the boat (underway) and the powder is instantly sucked under the hull and NOT pushed outwards.

Mike,
The ama's use nylon bushes at the boat end and one large stainless steel bolt at the ama end. The swinging in or out is quite easy. When the ama's are in position, (out) I then insert 6 extra bolts to secure, and then fix the stainless steel rigging cable with a turnbuckle on the the ama's giving a V section type reinforcing. This not only secures the ama from moving up but also from moving backwards, by the cable at the front and forward by the cable at the back. The front cable is angled forward and the back cable angled backward.
This aspect of the boat has been copied from a "dragonfly" trimaran made in Denmark. The present system although very strong would take 20-30 minutes to move the ama's in or out. This is OK for my use but could be modified for a much faster turnaround if you were coming into a narrow marina pen every day.

I have designed the boat so I can cruise the canals of europe (narrow) plus the occasional marina docking at a lower cost.

I have "gone" trimaran because the longer the waterline length the more comfortable the boat is in a seaway. I can build a 40 ft Trimaran for the same price as a 30ft Catamaran. OR a 55ft Trimaran for the same price as a 40 ft catamaran.
With a trimaran like this, particularly with fixed ama's (not swinging) you are essentilly building AND FITTING OUT one hull not two plus a bridgedeck.
I have attached one of my designs of a 40 ft trimaran with fixed ama's. Which could be made as a aluminium "shell" for under USD$ 80,000
The main hull is much wider and has a lot more interior room than my boat which is only 7ft 9ins wide so it will fit inside a 40 ft shipping container.

Beau Lyons
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