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Old 11-07-2007, 16:13   #16
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Beau,

So aren't you basically saying that a multi that sits below its designed waterline is going to be slower (aka - the conventional wisdom)?

If so, then couldn't a multi be designed to be "overloaded" and still have curved surfaces? (But then I guess you could overload an already overloaded boat...)

Regardless, I am enjoying the discussion. Looking forward to hearing more and seeing your boat completed.
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Old 11-07-2007, 16:47   #17
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Amazing!

All multihull theory aside, this is one amazing story. Beau, I'm glad to see these posts up, as I had been curious how you were making out.

Looks like the finished hull came together beautifully. Congratulations on taking a very innovative design (and systems) and putting it all together into a marvel of efficiency. I am more than impressed. Great work.

I have been intrigued by outboards as propultsion for a long time to save on fuel in a way similar to what you describe.

I do have one negative to ask about: It's a 20 knot boat, right? I don't know many power boats that can cruise at 20 knots because the sea is typically too rough/steep, etc... and the boat then has to slow down to the typical 8 knots or so. Will the wave-piercing bow allow you to simply bash though some of it the way that aluminum boat the Dashew's have does?

All in all... I'm very VERY impressed. This looks to be an ideal boat. 2 outboards=economy AND redundancy, aluminum=low maintenance, very nice.
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Old 11-07-2007, 18:24   #18
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Good on ya Beau, great to see it all coming together for you.

Ally sure is fast when you get into it.

A question, Any reason for the square forefoot in the bow?

That will be less inclined to ride up over anything that you may [will] hit.

Dave
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Old 11-07-2007, 21:46   #19
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I'm really curious how it would handle in heavy seas. With all those flats I would think it would get pounded, especially going over a swell.

The theory all sounds fine and dandy for smooth waters but I don't get to see much of that around here. It's bad enough when an IOR breaks a crest on a closehaul.

And motoring into the chop with flats sounds like a noisy/jarring proposition.

Quote:
Originally Posted by beau
In the tropics most of the time there is little wind anyway, the sea is flat so why not motor at 10 knots......


That's funny after spending 4 years cruising the S. Pac. while in the Navy I don't much remember seeing flat seas much. I do remember a typhoon or two.

Have you checked the weather today in the S. Pac.?
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Old 11-07-2007, 23:11   #20
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Quote:
Originally Posted by delmarrey
That's funny after spending 4 years cruising the S. Pac. while in the Navy I don't much remember seeing flat seas much. I do remember a typhoon or two.

Have you checked the weather today in the S. Pac.?
Like myself, I think Beau will be doing his big miles on the reasonably calm day's that are great for motoring, crap for sailing.

On this post
Off to Vanuatu at Last

We had a run from Brisbane to Vanuatu, in the middle of Cyclone season, with mirror calm condition's for the whole trip.

I agree that you do get wind and wave, but you also get long section's of calm as well, and that is when i'll do a run across.

Beau can stuff his tinny in a container, so he'll always have an easy trip.

Dave.
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Old 11-07-2007, 23:17   #21
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First of all let me say I think your boat is fascinating and I wish you well with the project. That you have built 4 prototypes already is amazing and it would be wild, although probably beyond this forum, to see the testing data, particularly the hull drag data.

Quote:
Originally Posted by beau
Gordmay
The friction formed with wetted surface is linear and follows the principle of "to double your speed reguires four times the power"
Wouldn't that then be exponential?

Quote:
Originally Posted by beau
With this knowledge it is possible to design multihulls that "can" carry extra weight which has little affect on performance other than the "small" increase in drag caused by extra wetted surface.
Exponential drag coefficients are not "small"

I am definitely not a marine engineer. I am an aeronautical engineer - we build weapons not targets - LOL

Your hull is basically a wedge in the water. For each pound of load you have to displace a pound of water. With most curved hulls getting "beammier" as they sink in the water they do push a bigger wake. I would guess that with flat sides you boat will sink deeper in the water with each pound vis a vis a classic hull.

My final question is that if this construction method is so simple and so efficient as you state. Why aren't all boats built this way? It's not as if the study of hydrodynamic drag is new or anything.

Are we just romanticists for curves?
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Old 12-07-2007, 02:03   #22
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This is what I am planning and is almost completed.

Trimaran Motor Cruiser with sail assist (downwind)
12 meter (39ft long X 19ft wide+Swing wing 10 ft folded (marina).
Only 2.3 meters wide for shipping.
NEW CONCEPT Super efficient fast displacement hull
10 knot cruising speed at $5.00 /hour (aussie prices)
20 knots at $15.00/hour
Non planing and non healing, Comfortable motion.
Range 2,000 nautical miles at 10 knots
Two Petrol or two Diesel outboards, currenly fitted
with two Honda 30 hp outboards
+Fits inside a 40ft container
+Aluminium heavy plate construction
+Trailable (on the back of a truck)
+Shallow draft (1 ft)
+Sail assist,
+Double decker construction for maximum room
+Large fridge and freezer
+9000 btu Air conditioning
+Watermaker desalinator
+Large 200 amp Alternator driven by a 13 HP Chonda,
+800 amp hour AGM battery bank
+Large aft deck
+Flybridge
+Full foam insulation
+Ideal liveaboard for two, suitable for four
+World cruiser.
Cruise to Singapore and then ship it home
Ship to Tahiti, cruise home.
Ship to the Mediterrean,fold the outriggers (10 ft
wide)and cruise the Canals of Europe.


Now to answer some of the questions.
ssullivan, thank you for your kind words.
This is NOT a planning powerboat that rides on the surface of the water, is is fast displacement with a very narrow bow that cuts through the waves.
The angle of entry is less than half the angle of Dashews boat. Yes it will be a wet boat, and it is designed to take waves over the bow. However it will not throw a lot of spray, as even above the waterline the bow is esentially vertical but sharply angled backward.
I do not believe the boat will pound because it is not travelling on top of the waves.
However most cruising will be done at a comfortable speed according to what the weather will allow. If there is flat seas I can either cruise economically at 10 knots or 20 knots if for some reason I need to get "there" faster. I will have 500 sg ft of sail for use downwind when the wind is between 10 -20 knots. If it gets over 25 knots I will motor.


Cat Man Do "square forefoot" I agree not good but I wanted the longest waterline I could get and still fit inside a 40 ft container.

Yes Ex calif you are right exponential not linear but the resistance which is produced by a bow wave is much larger as speed increases.
A displacement hull requires 5 hp per ton to achieve displacement speed a planning boat needs a minimum of 50 hp per ton to plane

An intereresting aspect was seen in regard to the stern wave with the wedge type hull. (with the prototypes) at under ten knots the stern wave has quite large but as the water started to break from the stern (at about 14 knots) the stern wave flattened out completely, the boat actually seemed to raise up in the water a little, we achived 20knots with two large people on board a 15 ft Plywood prototype with a 8 hp outboard.
No bow wave was formed, the water flow along the sides of the boat showed little or no turbulence (which is why there was no bow wave).

Yes I think we are in love with curves, everyboy wants to have a nice looking boat. I am hoping that when my boat is on the water it will all come together and look pretty good.
Remember, the underwater surface of planning boats have been flat or deep veed, flat since 1948. (Raymond Hunt)
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Old 12-07-2007, 02:59   #23
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Beau, as a matter of interest have you any idea on immersion rate ie "how many kg to sink her a cm".

Tennant's hull shape while totally different to yours also dont change in the waterline footprint, but do suffer in the immersion rate area.[This is why I did'nt go the Tennant hullshape as shallow draft was a priority ]

Looking at the pic's i'm assuming a massive amount of weight ??? will be required before you get near the knuckle/second level area?

What affect will unintentional overloading have on your connection/pivoting point's in the main hull due to leverage?

And yes, I do realize that we don't normally overload our multihull's, and that you will have no real need to as you don't really need to cross an ocean on your own bottom.

Dave
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Old 12-07-2007, 03:02   #24
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Quote:
Originally Posted by TabbyCat
Beau,

So aren't you basically saying that a multi that sits below its designed waterline is going to be slower (aka - the conventional wisdom)?

If so, then couldn't a multi be designed to be "overloaded" and still have curved surfaces? (But then I guess you could overload an already overloaded boat...)

Regardless, I am enjoying the discussion. Looking forward to hearing more and seeing your boat completed.
Sort of what I am hopeing for building 40 foot accom on 50 ft hull's and getting near enough to a 3500kg cruising payload.

Dave
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Old 12-07-2007, 03:53   #25
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Hey Beau,can I show them the pic's now?
I've waited so long for this part of the grand show & tell come cross reference,debate and admiration.Best B/day present ever.Ya gonna turn a lot of heads mate,and the missus too of course.I don't think I've ever kept a secret this long.

Kick arse.Mudnut.
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Old 12-07-2007, 04:41   #26
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Dave,
The structural engineer expects an all up weight of 2.7 ton which is an 8 inch draft, the Knucke is 18 inches high.
I do think the builders used a bit more structral bracing than I expected, they are used to building catamaran ferries of 200ft so it may end up weighing a bit more.
The bracing system on the outriggers has been used on the dragonfly range of triamarans out of Denmark (i think) They have been using this system for thirty years. The real strength is the use of a high strength wire cable as per an earlier sketch I posted. Also The outriggers are there for stability (motorboat) and will not have anywhere near the stress of a high speed sailing boat.They are also long ( for a power tri) but very narrow, (less wave making resistance.)

I have a 500 liter fuel tank up front and another 500 liters aft of center. I have a transfer pump to even up weight distribution.
The center of gravity, (we lifted the boat with a forklift) is 2/3 back from the bow, and that is before fuel or motors were fitted.

I do expect to be able to cross an ocean on the boats bottom. (I have already purchased a parachute anchor and series drogue)

However I have the CHOICE to ship it in a container if I want.
This gives an enormous amount of flexibility in where I go and what time of year I do it in.
THe Cost to send a 40ft container from Singapore to Brisbane, Australia is USD$2,000
I do not have to circumnavigate and I do not have to be at a certain point at a certain time to catch the best cruising season.
How many boats end up in Singapore/Langkawi and do not want to go any further (dont mention the word pirates)
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Old 12-07-2007, 11:43   #27
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This sucks....

I'm DROOLING over here.

Man, would I like one of these boats. This boat makes more sense to me than just about anything else I've seen.

The fact that you can ship it in a standard 40' container is just icing on the cake. Who cares how it handles Pacific crossings (not that it wouldn't, but who cares?)... just pack her up and re-assemble on the other side.

How much do you think this boat was total again? $130K all in?

Very VERY nice. Can't wait to hear about the handling after the launch.
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Old 12-07-2007, 17:12   #28
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I understand that youve addressed all the thing's I asked about, never thought for a minute that you had'nt, but I would still be interested to know how much you'd expect the sinkage/immersion rate to be.

And how many boat's are in Singapore/langkawi area and don't go any further?

In Langkawi/Penang there were bugger all cruisers full stop, but I reckon they had all stopped,the ones we spoke to had, and I know that well be joining them soon enough, though you'll be there before us i'll reckon.

Pirates, plenty of them mate, but their all burning DVD's and making copy watch and handbag's.

Except for the "official" pirates in Indonesian waters of course.

Dave
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Old 12-07-2007, 17:17   #29
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Quote:
Originally Posted by beau
This is what I am planning and is almost completed.

+World cruiser.
Cruise to Singapore and then ship it home
Ship to Tahiti, cruise home.
Ship to the Mediterrean,fold the outriggers (10 ft
wide)and cruise the Canals of Europe.

This is bloody appealing. To be able to cruise anywhere in the world in your own boat, without the need for passagemaking. (Although the option is still there if you want to) It looks like a great concept.

When you launch (in a few weeks!) I'd really like to have a look.
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Old 12-07-2007, 18:27   #30
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[quote=beau]Dave,
The structural engineer expects an all up weight of 2.7 ton which is an 8 inch draft, the Knucke is 18 inches high. [quote]

Dave
With vertical sides this should give 135 kg/cm. The 10 inch clearance to the knuckle would be used up at 3375 kg payload.

Mike
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