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

[baeckmo]

Thanks John, (both of you....!). That warms a frozen heart, now let's get on forwards

 

[gonzo]

What the hell are you two talking about? Baekmo, that was nonsense.

No, Gonzo, KE is not fuel burned. It is kinetic energy. Work done in accelerating water rearward so that the reaction force described under Newton's 3rd law (momentum) can propel your boat. So your power requirements scale with kinetic energy, but your thrust scales with momentum.

That was in response to your claim that burnt fuel is KE. It appears that it meant that in that context it was the energy in the fuel converted to kinetic energy.

 

[BMcF]

Bodo,
In the paper by Rolf Svensson, KMW - Waterjet Conf. - RINA 1994, they show slight fluctuations - with some measuring imperfections - but with values in the 0.73 - 0.78 range.
View attachment 164611

I still recall this conference, as it was the first i co-authored at and presented!

I worked with Rolf back in the 80s as we sorted out the various issues encountered in getting the KaMeWa jets properly integrated with the SES vessels we were developing and building back then.

 

[BMcF]

Right. Ad Hoc emailed me to say that Baeckmo is top drawer in his field, and we are arguing definitions, not content, and talking past each other. So I'm climbing down from DevCon4. I'll try to learn what I can, from your particular expertise, Baeckmo. No doubt your knowledge of pumps is encyclopedic. I took vector mechanics in 1983, not pumps.

J

Bodo is indeed that....which is why I've enlisted his help and expertise on occasion. When it comes to propulsion..it vastly exceeds my own.

 

[BMcF]

I'd prefer a Norwegian Skjold-class corvette which is a SES, see Leo Lazauskas paper.
Wayback Machine https://web.archive.org/web/20080719002649/http://www.cyberiad.net/library/pdf/giam260a0.pdf[/QUOTE]

Always my favorite SES...but perhaps I'm biased. ;-)

 

[DogCavalry]

That was in response to your claim that burnt fuel is KE. It appears that it meant that in that context it was the energy in the fuel converted to kinetic energy.

You are right. Brevity is only the soul of wit if you're Oscar Wilde. I meant to say that, all other things being equal, you vessel is driven by reaction forces from momentum imparted to the working fluid (water or air), but the power required to accelerate that fluid depends on the kinetic energy imparted to the fluid, so half the fluid at twice the velocity gives the same thrust, at twice the power requirement.

Of course Baeckmo very eloquently expressed exactly that in his first post in this particular exchange. Jehardiman's contribution expanded on that. To the effect that while generally speaking, I was correct. An open prop can be substantially more efficient. However.... there are regimes where the limitations on props are not the same for pumps, and under those conditions, a pump is the correct answer for the system as a whole. Well, it only takes a boot up the arse from a guy in Japan, and even an old Dog(cavalry) can learn something new.

 

[Squidly-Diddly]

anyone got a basic graph/chart of power to weight ratios required for planing boats, especially at the higher weights?
Maybe a 3D graph that also factors in hull size/planning area?

Maybe with flat, shallow and deep Vee hulls?

 

[DogCavalry]

Savitsky pointed out that hull size is irrelevant, only weight, beam, and deadrise angle.

 

[jehardiman]

anyone got a basic graph/chart of power to weight ratios required for planing boats, especially at the higher weights?
Maybe a 3D graph that also factors in hull size/planning area?

Maybe with flat, shallow and deep Vee hulls?

Generally results like those are presented as a graph of total resistance/weight vs volumetric Froude number for standard series hull forms. Try the DTRC (or whatever DTMB was calling itself at the time) Series 62 (codified into SNAME Bulletin 1-23), the DTRC Series 65 papers, as well as Hadler's expansion of Savitsky's work (SNAME Trans. Vol 74).
The fact that planing hull data is presented as Rt/W vs. Fnv allows us one last touch on the whole propulsor-prime mover- bunker issue. Yes, specific energy of the fuel plays a part, but only in the weight of the overall vessel. Because in actual practice there is not really that much to choose from in the weight of installed propulsor(s). It is only the weight of the prime mover(s) and the bunker that actually drive overall displacement (i.e. weight) assuming that the rest of the loadout is identical. This means that a more power dense fuel results in higher speed and/or longer range. This is why the gasoline engine supplanted most others in the small planing vessel market.

 

[HJS]

Savitsky pointed out that hull size is irrelevant, only weight, beam, and deadrise angle.

...... and LCG which indicates the bottom aspect ratio.

 

[gonzo]

Generally results like those are presented as a graph of total resistance/weight vs volumetric Froude number for standard series hull forms. Try the DTRC (or whatever DTMB was calling itself at the time) Series 62 (codified into SNAME Bulletin 1-23), the DTRC Series 65 papers, as well as Hadler's expansion of Savitsky's work (SNAME Trans. Vol 74).
The fact that planing hull data is presented as Rt/W vs. Fnv allows us one last touch on the whole propulsor-prime mover- bunker issue. Yes, specific energy of the fuel plays a part, but only in the weight of the overall vessel. Because in actual practice there is not really that much to choose from in the weight of installed propulsor(s). It is only the weight of the prime mover(s) and the bunker that actually drive overall displacement (i.e. weight) assuming that the rest of the loadout is identical. This means that a more power dense fuel results in higher speed and/or longer range. This is why the gasoline engine supplanted most others in the small planing vessel market.

Small planing vessels are usually designed for a short distance range. When vessels are designed for longer range, diesel fuel is customary because of its higher energy density.

 

[TANSL]

I'm curious, how does the design of a planing hull change (hull not a boat) depending on whether it is for short distance range or for long distance range? And, on the other hand, how is energy density measured?, amount of energy, joules, per cubic meter of ship ...?

 

[gonzo]

Energy density is measured as energy/volume or energy/mass. The units are irrelevant as long as they are consistent. Diesel fuel has a higher density than gas by either criterion.

 

[TANSL]

Amazing, you keep surprising me with your technical concepts.

 

[bajansailor]

Just an observation - sadly so many threads on here nowadays invariably stray away from the original topic and develop into a peeing contest about semantics and definitions with subtle insults being hurled around - please, lets just stay on topic?