Maori DE-1913

[Valles]

I had a brainstorm that resurrected this unholy evil of a concept.

Namely, that it'd probably be considered wise to have a more conventional, cheaper cruising engine that could be entered into SS as the 'primary' engine to get an accurate read on the resulting boat's steadiness and stability. The aero engine would be entered under misc weight and the top speed tweaked in the design process to get a 'combat seakeeping', which could then be included under the 'notes' section. Each engine would either drive different props or require Geared Drives to be able to switch between them.

Reasonable?

[Korpen]

I had a brainstorm that resurrected this unholy evil of a concept.

Namely, that it'd probably be considered wise to have a more conventional, cheaper cruising engine that could be entered into SS as the 'primary' engine to get an accurate read on the resulting boat's steadiness and stability. The aero engine would be entered under misc weight and the top speed tweaked in the design process to get a 'combat seakeeping', which could then be included under the 'notes' section. Each engine would either drive different props or require Geared Drives to be able to switch between them.

Reasonable?

Just how small a ship are you talking about, 100tons or as large as 200?
The reason i am asking is that with areo engines limited to 120hp, you need a very small boat to make them an improvment in speed. :)

But considering the hp limits we got on all engines, I do not really see this as reasonable. While we should not follow history like slaves, it is worth to ask oneself why no one tried mounting aircraft-style engines in ships of any size, it might be that there are physical reason that makes that sort of engines unsuited to ship propulsion.

[Sachmle]

 Ever wonder why no one ever did this in RL? Probably because it's an inherently bad idea. I don't have a problem w/ originality, but seriously this is a little overboard.

[Desertfox]

Alexander Bell did, with a hydrof...err speed boat no less!

Now to begin work on that hyrdofoil...

[Sachmle]

A hydroplane is one thing, a 100-200t TB is another. Maybe if we were talking MTBs here, but a TB?

Or if this topic was Maori DE-1943.

[P3D]

I had a brainstorm that resurrected this unholy evil of a concept.

Namely, that it'd probably be considered wise to have a more conventional, cheaper cruising engine that could be entered into SS as the 'primary' engine to get an accurate read on the resulting boat's steadiness and stability. The aero engine would be entered under misc weight and the top speed tweaked in the design process to get a 'combat seakeeping', which could then be included under the 'notes' section. Each engine would either drive different props or require Geared Drives to be able to switch between them.

Reasonable?

Umm... No? IMO the easiest and best is to have separate tech for (M)TBs that have fixed characteristics to overcome SS2 limitations - similar to the sub techs. Also, the lack of any naval engineering experience on the forum (AFAIK) is a big obstacle in the way of multihulls.

The main advantage of a trimaran that it have shallower draught, and the main hull can be longer without much regard to stability consequences - at the cost of larger waterplane area thus resistance, and additional structural weight - the outriggers and  the extra weight of the sponsons. Also, a trimaran would not right itself, so storms that can be survived by a destroyer might cause a trimaran to capsize.
And we have the complete lack of historical steel (or even wood) high-speed trimarans for this time period.

[Valles]

It's rather amusing how much harsher the responses get as I start to get more serious about this concept. ^_^

Anyway, I'm talking 'full sized destroyer' for the moment, very much like a refinement of the multi-hull design on the previous page of the thread. A number of cruise and military ship designers in the present day think that a very similar arrangement is quite a good idea, I'm given to understand. Real world designers in the nineteen-teens likely never considered such a thing because they'd never been so crazy as to try and develop steam engines light enough to drive an airship and so were limited to, as noted, about 120 additional horsepower.

And, no, P3D, I'm not intending to build a 'combination powerplant' into a multihull - having the heavier cruising engine would give sufficient stability in its own right to render the outriggers unnecessary.

I do like the idea of separately researched MTBs, though.

[P3D]

It's rather amusing how much harsher the responses get as I start to get more serious about this concept. ^_^

Anyway, I'm talking 'full sized destroyer' for the moment, very much like a refinement of the multi-hull design on the previous page of the thread. A number of cruise and military ship designers in the present day think that a very similar arrangement is quite a good idea, I'm given to understand. Real world designers in the nineteen-teens likely never considered such a thing because they'd never been so crazy as to try and develop steam engines light enough to drive an airship and so were limited to, as noted, about 120 additional horsepower.

And, no, P3D, I'm not intending to build a 'combination powerplant' into a multihull - having the heavier cruising engine would give sufficient stability in its own right to render the outriggers unnecessary.

I do like the idea of separately researched MTBs, though.

XIXth century engineers were much crazier than you'd think. E.g. there were about a dozen attempt to build a rotary steam engine that I know of - Parsons himself had some before finally arriving at the turbine.

Again, this could be solved by variable engine specific power. Even so, contemporary large IC engines were heavy, and airship engines were far from the power requirements. So a 14000SHP diesel would weight more than 30t. And forget about electric propulsion, that would add so much to the weight (another 60+t for the power) that any weight savings from the lightweight IC engines would disappear. And the adequate I engine technology still needs to be developed.

Does anyone have some weight figures on airship engines?

[Valles]

I spent a few very frustrating hours trying to research airship engines before I went and expanded on the power/weight ratio of WWI fighter engines; no joy.

I was on a big 'the world can be saved by STEAM' kick when I put together my 'application for' tech tree for the Maori, though, so their airships are designed to use central steam engines throwing shafts off to multiple propellers, rather than having several engines like real world rigids did. I haven't had occasion to build any new ones, yet, but I've been planning to add $0.1 per engine to my airship building costs to account for the exotic materials (in 191X, titanium is exotic) needed to build their engines; whatever ships or boats get built using the same technology would have at least that much added. I've been consistently rounding numbers up from my base 500 hp/ton guesstimate, also.

[P3D]

Titanium is too difficult to manufacture (just ask maddox).
Pure metallic Ti was first produced in 1910, and practical uses are still several decades of materials research away (historically, after WWII). IMO It does not offer much advantage over some advanced ferrous materials.

Scaling up high RPM aircraft engines is not a good way to estimate power-to-weight ratios. As engines grow, max RPM decreases (due to the combustion speed of the fuel-air mixture), with it the power output. Using diesel instead of gasoline/petrol makes the engine even more heavier.
500HP/t is the Maybach HL230 of the Tiger. Petrol engine, 1200kg for 600HP(sustained).

I will do some SS to see if i can get some enigne weight estimate for Italian MAS.

[P3D]

I simmed hulls for MAS and S-boats, then increased engines to get a composite strength of 0.8-0.9. Also added some arbitrary misc weight for guns torpedoes etc.

MAS 204 (1918) had 2x700HP engines. Engine weight comes at ~5-6t, giving 2-300HP/t. MAS 432 has 3x1500HP engines - the engine power-to-weight corresponds well to aircraft engines (1000HP/t).

Looking at medium-power marine engines (2500HP) for the larger Schnellbooten, power-to-weight ratio is somewhere between 150 and 200HP/ton (let's say 200). Compare it to 50-60SHP/t for the German battleships' high-pressure steam machinery in WWII, 30-40 for large marine diesels, or RN destroyer machinery (essentially constant at 80-90 SHP/ton between 1914 and 1942).