Displacement Speed Question

[Village_Idiot]

Originally Posted by FAST FRED

Would seem that most of the Atkin Box keel reverse deadrise are quite similar, however Atkin goes two steps further in an attempt to capture the velocity of the water dragged by the canoe body and hull above and feed it to the prop.

And in using the reverse deadrise to lift the stern from the water , perhaps reducing drag even further.
No stern flaps anti squat required.

We all dream of a series of tank tests to see if this old design is as efficient as claimed 50 years ago , and weather a modern version would indeed make a super efficient SL 2.5 or 3 cruiser .

With modern materials weight and maint could be minor , compared to planks.

FF

There is an outfit in Texas that is building a shallow-water marsh/flats boat that incorporates some semblance of the inverted V / Hickman design.

http://duckmasterboats.com/lagunatiger.html

http://duckmasterboats.com/lagunatiger2.html

[mydauphin]

Originally Posted by Ad Hoc

still confused, in what plane is the view?

Your in the back of the boat looking at bottom looking forward.

[Ilan Voyager]

A bit more infos on the USS Hurricane


Length, Overall 51.62 M (169 ft 4 1/4 in.)
Beam, Maximum 7.62 m (25 feet)
Length at design waterline (DWL) 48.00 m (157 ft 5 3/4 in.)
Draft above Bottom of Keel Corresponding to Full Load Displacement 2.14 m. (7.02 ft)
Displacement, Full Load 315.32 tonnes (SW) [310-34 L Tons (SW)]
Height of highest projection above baseline to lowest projection below baseline 17.77 m (58 ft 3 3/4 in.)
Superstructure Material 5086 Aluminum
Fuel Capacity 47,772 Liter (12,620 gallons)
Fresh Water Capacity 4,701 liter (1,242 gallons)
Lubricating Oil 568 liter (150 gallons)
Boats (1) 20' RIB, (2) Combat Rubber Raiding Craft (Large)
Crew 30 persons
Capacity (including crew) 39 persons
Maximum Speed
(sea state 1, 50% fuel capacity) 35 knots
Cruising Speed
(sea state 3, 50 % fuel capacity) 25 knots
Minimum maneuvering speed 3 knots
Seaworthiness Survive through sea state 5
Minimum Range 2000 nautical miles at most economical speed over 12 knots
Endurance 10 days
Propulsion Engines Manufacturer: Paxman, Type: Valenta 16CM Diesel, Model 16RP200M, Rating 3350 bhp @ 1500 engine rpm, QTY: 4
Reduction Gearbox Manufacturer: Reintjes, Model WVS 2232, Reduction Ratio: 2.025:1, QTY: 4
Propellers 5 Bladed Fixed Pitch Nickel Aluminum Bronze
Generators Manufacturer: Caterpillar, Model 3306 DITA, Rating 150 Kilowatts @1800 rpm, Quantity: 2
Air Conditioning Air Conditioning Plants 83.33 kW (23.7 Tons) Total
Desalinators Reverse Osmosis Desalinators 1514 liter (400 gallons) per day
Builder Bollinger Shipyards, Inc.

[Ad Hoc]

Looks like small "tunnel recess" for prop's...since it doesn't really show much else with one line and no reference to a baseline and CL nor how the shape changes as the lines go fwd in body, profile and plan view.

As for a name..pick one...does it matter so much?

[Village_Idiot]

Originally Posted by mydauphin

Ran across this reverse transom, it work its way to the front were it became a traditional V hull. So the boat had a large reverse planning area in between chimes. Anyone seen this type of hull, what is it called and do you anything more about it? thanks

Here is a similar, though extreme, version of that hull bottom that is in production (pay attention to their logo design).

http://www.shallowsportboats.com/body.htm

I'd consider it a modification of a tri-hulled monohull.

[mydauphin]

Yes, village it looks very similar, the one I saw is a little flatter and wider.

So my question is... Is a reverse planning area in between chimes typically better to worse at planning(lift) that a regular planning hull?... It would seem to entrap air better.

[Village_Idiot]

The best planing hull would be a true flat bottom. I believe an inverted-V-hull (e.g. - reverse chine) would plane easier than a standard V-hull of the same deadrise, and likely hold plane at a slower speed. The added benefit of the inverted-V would be raising the motor/prop for shallower operation. There is also apparently less spray from the hull since most of it is directed inward, although it may suffer from sneezing. Not sure how their ride would compare to a V-hull of the same deadrise configuration. I'd also think handling would get squirrelly in high-HP situations. However, I don't have any personal experience with these inverted-V hulls, so I'm just judging based off of simple physics (ya know, physics says a bumblebee cannot fly ).

A number of flats boats designed for extreme shallow water operation incorporate some sort of air entrapment under the hull. As another example, look at the flatscat www.flatscat.com although its purpose is to entrap water rather than air, and bring it up into the center of the hull where it can feed the prop above the waterline. Other flats boats that use air- or water-entrapment technology are Ultracat, Transcat, Laguna Tiger, and I'm sure many more that I cannot think of at the moment.

[Leo Lazauskas]

Originally Posted by Village_Idiot

...so I'm just judging based off of simple physics (ya know, physics says a bumblebee cannot fly ).

I heard that was just another urban myth perpetuated by village idiots

[mydauphin]

Thank you village...
Question - why on earth did you pick a name like Village_Idiot ?

[Ad Hoc]

Having chines lower than the keelson would mean the boat is very likely to be too directionally stable, so much harder to turn. May also induce a broach too. Also, the point of a chine and a keel is to separate the flow to provide a lifting surface, which is why round bilge hulls don't plane without spray rails. If the keel line is higher, the flow of water will be mixed, not separated as would be the case on a normal Vee hull.

[Willallison]

The Hickman Sea Sled featured an inverted 'v' and was reputedly an excellent sea boat

[Ilan Voyager]

Inverted V are planing boats. This shape is useless in displacement boats.

We are getting far from the initial question...I'm a bit more familiar with fast displacement boats as I've worked on them. A lot of research has been made about this kind of boats for fast ferries.

Myself I had a very small part in a research made by the French Navy about 20 years ago; the conclusions were simple: the lightest , the longest, the slimiest with the sweetest shapes (elliptic, plumb bows with no flats, no bumps, no hollows) were the winners. No miracle, no magic shapes... and I can say that a good number of shapes were tried. The better were rather close to the amas shapes of the actual 60 feet trimarans but with a different center of displacement (it's normal as sailboats have the engine -sails- several meters above the deck). Ratios LWL/BWL from 12 to 18. Chine hulls were not explored.

The difficulty with these shapes were 2;
- not enough stability so the multihulls were mandatory.
- very difficult to place the propellers and engines. Surface props, waterjets or pods were also mandatory.

None of this solutions were of the taste of the french navy. In fact no navy was ready to go that far 20 some years ago. Thus the classical monohull shapes were kept.

We can see the problem of the propellers with the USS Hurricane; a true forest of shafts and supports making a big drag plus 4 propellers that are robbing power each other. Not very clean in a hydrodynamics point of view. 13400 HP for getting 35 knots on a ship of this size and weight is not outstanding (but warships are designed with other requirements than only efficiency).
The ferry catamaran Patricia Olivia II, shorter (45 meters), and heavier achieves 50 knots with 15600 HP...

Both, USS Hurricane and Patricia Olivia II are displacement boats. At 35 knots the catamaran ferry is using far less than 13400 HP. There no competition.

It's funny that a situation similar to that happened in aviation in the States around 1935, when the civilian DC3 and other transport planes were faster than the fighters and bombardiers, is happening now; multihulls ferries are faster than warships of similar size, and the monohull ferries very close.

The catamaran ferry Luciano Federico makes 110 NM travels in Mar de Plata in 2 hours...http://www.ship-technology.com/projects/luciano/

Another link (in Spanish, but pics and ciphers do not need translation):
http://www.rkviajes.com/buquebus/flota.html

The navies have to change their minds...

Adrian Thomson draw a patrol boat and a prototype made with a very slim hull and 2 flats (what's the word :chines?) I do not know if it was succesfull or not. I do not find anymore a link.

The displacement boats with the highest Froude numbers are sailboats: catamarans and trimarans. A Tornado catamaran (20 feet) can attain 25 knots and the best 18 feet are very close, a Class C catamaran can reach a bit more than 30 knots knots (Victoria 100 has been measured at that speed), a 40 feet trimaran can reach 27 knots on 1 NM (Data General a 40 feet catamaran with oceanic ability could easily go to 20 knots on only mainsail and 26-27 with full sail and spi in 1987), a 60 foot trimaran can reach 35 knots over 3 NM and more than 24 knots during 24 hours.

And the big boys like Groupama III (trimaran 103 feet 794 NM - 1470 km or 914 US miles in 24 hours so 33 knots of mean speed, the Atlantic at almost 30 knots...) or IDEC (trimaran 30 meters, 11 metric tons, 26 400 NM -49000 km or 30385 US miles- at 19,09 nœuds SOLITARY, yes a guy alone around the world in every state of sea...)

As you see the recipe is simple: light, slim, multihull.

When applied to motor multi yachts that gives: Ilan Voyager 21 meters 5 to 7 metric tons trimaran 28 knots with 240 HP only. Main hull, elliptic shapes, 17 to 1 ratio. Oceanic ability.

[Willallison]

The Adrian Thompson boat was called the VSV and it has spawned several variants since. Most recently the pleasure boat Mary Slim. All were quite succesfull I believe, though I think all operated in the planing mode, even though they were round bilged

[Rick Willoughby]

Originally Posted by Ilan Voyager

.......

As you see the recipe is simple: light, slim, multihull.

.....

There is an exception to this.

If you go below the surface and consider submerged buoyancy or full submarine there is a significant reduction in drag over what is achieved with high speed surface craft.

As noted on the current SWATH thread the optimised submarine Albacore AGSS 569 achieved 33kts with 7500HP. It was a 1540t vessel.

A single hull submerged buoyancy vessel has significant advantage from a drag perspective but making it practical for common use poses many challenges. I have first hand experience of this.

Rick W

[Ilan Voyager]

Originally Posted by Willallison

The Adrian Thompson boat was called the VSV and it has spawned several variants since. Most recently the pleasure boat Mary Slim. All were quite succesfull I believe, though I think all operated in the planing mode, even though they were round bilged

Thanks for the news. Very interesting boat. Beginning at displacement mode, ending planning when the "flats" are on the surface of the water. You're right it's more a planing boat.