What is world's biggest planning hull boat and how fast?

Ummmm, this falls into my "Possible- feasible-practical" argument. I would say the cube-squared law makes it unfeasible at the present time, we have no good concept of of future power densities beyond what stars make. Realistically, I think both you (DogCavalry) and he (KeithO) need to understand the differences between how power is made and how power is delivered to the propulsion unit. LSDs use massive pressures and long strokes to deliver variable high-torque low-rpm directly to the driven shaft. For ST and GT main propulsion of large vessels, the ST or GT delivers constant high-rpm low-torque power which is converted by electrical manipulation to variable-torque variable-speed main propulsion units. This is not new, the mid WWI standard class battleships and the LEXINGTON class BC/CV's used ST-electric drives of 180,000+ SHP. The current AMERICA class LHA's use a mixed, and distributed, CODAG-electric system of ~80,000 SHP. So you are really arguing apples and oranges as it becomes a need, space, weight, and arrangement tradeoff.

 

Actually I'm not sure what you're arguing for or against. Jehardiman, have you been following this?

 

Yes, and I don't think either of you understand the complex tradeoffs. KiethO is patently incorrect when he states "The most powerful boats have gas turbines that make considerably more hp/lb than any reciprocating piston engine." And you are also incorrect when you say "Most powerful engine is that Wärtsilä, making 46hp per ton." There are lots of things wrong with both statements in terms of overall ship design and how power (and fuel and air) is supplied to the prime mover and then on to the thrust unit.

 

One has to respect the obviously extensive knowledge of jehardiman, DC !

 

One of the highest power to weight ratio engines is the Cox TeeDee .049 cubic-inch engine.
It only makes 1/20 of a horsepower but weighs next to nothing.
Can turn up to 35 000 RPM.

 

I acknowledge and respect Jehardiman's erudition, but this is being pedantic for the pleasure of being pedantic. My statement about the Wärtsilä is simply correct. Unless someone can provide an example of an engine that makes more than 107000 hp, I am quite reasonably going to be annoyed. At no time did I make a statement that resembles a claim about it's installation. I referred to the Wärtsilä when describing how engine output, like planing lift, suffers from cube/square limitations that are punitive at the high end. I provided the (correct) figure of 46 hp/ton because I imagined the reader could call to mind many examples of good diesels with much higher power to weight ratios, and visualize the power to weight ratio curve, as I did.

Discussions of installation details are extremely intrinsically interesting to me, but do not meaningfully contribute to an attempt at defining the theoretical physical limits of planing hulls.

 

Awesome Bluebell. I don't mean to be cranky, but we do tend to go off topic.

Points: that little screamer is amazing. It's power to weigh ratio is the perfect anchor for the other end of that curve.

Also: the mean piston speed is about the same in both engines. Isn't that interesting? It's higher in the screamer, at about 11ms, vs 8.5 in the Wärtsilä, which when talking orders of magnitude, is basically the same. The actual limitation on engine output is air flow velocity, so all piston engines are limited to similar piston velocity. More efficient intake ducting, or supercharging, both push these limits. Intercooling and charge cooling allow denser cooler air, which can move as quickly but carries more oxygen.

ICE studies are endlessly fascinating.

 

Jehardiman ( A.K.A. John ),

To extend this thread drift,
and you being a local,
can you shed any light on why Clipper Vacations removed the turbine engines
and replaced them with diesels on their MV Clipper IV?
That's an expensive switch.

BB

 

While I am retired and have no direct knowledge (which would fall under professional confidentiality requirements anyway) of the Clipper refit, from my personal experience most refits come from three major concepts; there is a mission change, there is an economic change, and the refit is cheaper than a new build. Perhaps it was a mission move from just doing Victoria runs (which would favor a GT) to route runs (which would favor a MSD), or perhaps it was a change in Canada's emission regulations (favoring new Gen III diesels) or bunker prices, I really wasn't involved and can't give you an exact answer.
Rather than getting into a "pedantic pissing war", lets touch on some topics of prime mover selection.
1) There can be no prime mover selection without a mission requirement and statement of requirements (SOR). Every decision is based upon this, and it has to consider the whole concept. You would get a very different vessel if you asked to "go as fast as possible" than "highest sustained speed across the Atlantic" or "best fuel economy of the specified ferry run", or "lowest economic cost of the specified route", or even "highest sustained speed while carrying 9 16inch/50's and sufficient armor to defeat a similar armed ship at 10,000 yds and having a 15,000 mile cruising range and fitting into the 1940 Panama Canal locks"...which was effectively the IOWA class BB ship spec.
2) When considering a prime mover you have to consider the whole install. While the specific power that was quoted for the LSD was for the installed piston stacks, I doubt it included all the ancillary equipment needed to make the engine run. The air compressors, coolers, heaters, pumps, etc are a significant weight and space. It is impossible to compare true specific power over the power range from the Cox .049 to a FORD class CVN, especially when bunker, lube, and range are added to the SOR.
3) In very large power installs, multiple units are installed for redundancy...and this includes LSDs. Realistically, since the mid 1970's LSDs are spec'd and sold by the piston; need more power?...add another piston. Today LSD's are designed so that individual pistons can be decoupled to allow maintenance while underway, so that 11 piston engine is typically not hitting on all cylinders.
4) It is correct that piston speed is effectively constant across ICEs (~9 m/s recalling from memory) and one of the limiting factors in engine size and speed. The other is cooling the piston, which limits bore; LSDs have significant LO consumption because it is sprayed on the piston to cool it.
5) Single acting diesels do not have the greatest specific power for diesels in the mid power ranges, that title belongs to the twin opposed piston and tri-deltic units fitted in submarines and patrol craft respectively.
6) Marine GTs have a significant weakness to salt mist ingestion. Salt plating out on the power blades is the main cause of turbine replacement. Significant space and equipment is required to ensure clean air to the turbines. This is one of the reason marine GTs are pre-packaged for easy swap out, so you can inspect and clean the hot end of the turbine before you have a blade failure.
7) My last involvement in a study may be a little dated (early 2000's) but for very large power installs on military vessels considering only specific volume and specific weight OF THE PLANT, the order was: superheated steam, GTs, distributed MSD-electric, saturated steam, LSD. When bunker was considered it was saturated steam, a tossup between distributed GTs, MSDs, CODAG, or D/G-electric, superheated steam, LSD. The real killer to LSDs was arrangement issues for military vessels.
I could go on, bur as usual the actual answer is "it depends..."

 

Agreed very sad, went onboard her in NY in 92 as she needed some repairs....had half the shipyard down there!.....quite a machine

 

Jehardiman, I am, as always, impressed by the breadth and depth of your knowledge. Thank you for allowing me my tiny corner.

 

DogCavalry, are you aware of any planing hull applications of those large MTU engines ? It would seem that the weight/thrust balance would be exhausted quickly with that kind of setup ?

 

I don't pay any attention to the extreme edge of the envelope, keith0. Sorry. My favourite things are the kinds of things I can work on myself. I'm a scarred knuckles kind of guy.

 

She is a stepped hull planing boat, as is obvious from the photographs. Possibly the largest planing boat built?I wonder why they chose waterjets?

Edit: I am well pleased. I just ran her published displacement and installed horsepower against her reported top speed, to see what Crouch constant would pop out of Crouch's formula. I got 220. Which, according to Gerr's Propeller Book is actually the constant for a step hydroplane. How cool is that?

 

You are missing the basic concept. Waves are formed at the interaction between two media of very different density and viscosity. A submarine completely submerged at a considerable depth on deep water , is not creating waves.