WesWorld

Since Hoo has requested this:

I am working on the assumption that

a) Diesels weigh 50% more than steam turbines

b) electric transmission carries a 10% weight penalty (this BTW should increase damage resistance by 10 to 20% IMHO, since internal subdivision improves - opinions?).

So if you have a diesel-electric ship, you take the machinery weigth given in the propulsion tab of SpringSharp and call it x. The misc weight wm you have to add to simulate the effects is:

wm = (x * 1.5 * 1.1) - x

a turbo-electric ship gets

wm = x * 0.1

now for hybrid propulsion we will have to assume that the more efficient machinery is used for cruise and the less efficient machinery for dash. SS gives us the power needed for cruise on the propulsion tab. Since I just have Navarra open, I'll use her as an example (suitably modified of course):

Oil fired boilers, steam turbines plus diesel motors,
Electric motors, 5 shafts, 44,311 shp / 33,056 Kw = 25.00 kts
Range 15,000nm at 10.00 kts


Now in this config the cruise speed is 10 kn, everything else would need steam. This is important! the reason for this is here:

The propulsion tab gives us the "power at cruising speed". In this case 2048 hp. We'll call it Pc.

The power at full speed (Pf) is 44,311 hp

the weight x = 2,238 t

Now that gives us the weight for our cruising machinery:

y = Pc/Pf*x = 2048/44311 * 2238

y = 103 t

mw(y) = y * 0.5 = 51.5 t

these are the diesel engines

mw(x) = x * 0.1 = 223.8 t

mw = mw(x) + mw (y) = 275 t for machinery

all in one formula:

mw = x * 0.1 + x * Pc/Pf * 0.5

in case of full diesel propulsion Pc/Pf becomes 1.

cheers

Bernhard

Ship design AND Algebra?
I feel like i'm back in school!!

hehe, I just hope, it's halfway understandable

ok, nobody has said anything. hoo, you want to put it into the rules then?

I haven't said anything ...cause ...well I don't understand a damn thing! Hooman may so I trust his opinion on this one.

catch me in ICQ and I'll try and talk you through it. I am not good at explaining that kind of thing in writing. And if Hoo doesn't understand it I definitely have been too cryptic.

Nicely put, LA.

I can´t tell if the factors reflect reality but the logic and math behind your formula does make sense except for one case. I´ll explain that below.

I don´t think we need long explanation for our rules and so I propose to use just the results.

Misc weight (wm) to be added for (x = machinery weight)

a) Turbines, electric drive

wm = x*0,1

b) Diesels, geared drive

wm = x*0,5

c) Diesels, electric drive

wm = x*0,65 [= x(1,5*1,1-1) = x(1,5*1,1)-x = (x*1,5*1,1)-x]

d) Mixed propulsion, geared drive

wm = x*0,5*Pc/Pf where Pc = Power/cruisespeed and Pf = Power/fullspeed

e) Mixed propulsion, electric drive

wm = x*0,1 + x*0,5*Pc/Pf*1,1

(-> I´ll explain what I did in the post scriptum.)

I´m aware of the fact that SS handles misc weigth differently from machinery weight but LAs rules are the best I´ve seen so far to handle other machinery - even if we need to assume that poweroutput scales linear (otherwise we couldn´t use Pc/Pf).

What I´m missing here is what effect those drives will have on range and damage resistance. To assume electric drive allows better subdivision and thus such a design could gain 10% resistance sounds okay to me. On the other hand I´ve read about several occasions where turbines on US ships still ran even while submerged due to flooding - something a diesel never would do. Further more diesels are higher, need more room than turbines and thus I would expect damage reduction to be somewhat less than on a ship using turbines....

What does the board think?

Regards,

HoOmAn

PS: Now it´s time to explain why I added that factor above.

If we look at the formula Bernhard uses for diesels, electric drive we can see that he does not only add a 10% penalty to the original machinery weight but also on the additional 50%.

He uses x*1,5*1,1 meaning that the original weight is increased by 50% and then another 10% are added. This sums up to a total 65% penality on diesel driven ships with electrical transmission.

wm = x*0,65 [= x(1,5*1,1-1) = x(1,5*1,1)-x = (x*1,5*1,1)-x]

Later he explains how one has to calculate misc weight for hybrid propulsion plants/electrical drive. He uses

wm = x*0,1 + x*0,5*Pc/Pf

If you look at it closely you can see that he now adds 10% on the original machinery weight but _not_ on the diesel weight. Thus the result does not compare to what he got before using the other rule. It becomes more obvious when using his remark. He states that Pc/Pf=1 if one uses pure diesels. In other words Pc/Pf=1 means that you´re simply using diesel, electric drive as explained above.

The problem now is that if you use Pc/Pf=1 the misc weight you have to add is only

wm = x*0,1 + x*0,5 = x*0,6

and not

wm = x*0,65 !!!

To fix that error we have to make sure the 10% penalty for electric drive does also apply to the diesel component when modelling hybrid drives. That´s why I added the factor 1,1.

Then we get

wm = x*0,1 + x*0,5*1*1,1 = x*0,65

if Pc/Pf=1 and everything´s fine again.

Hi

I actually spotted that error in my reasoning, just was to knackered at the time to fix it.

range improvement by diesels: 50% I'd say

turbines will run under water, boilers won't ;-)

Electric propulsion with diesels means that you can put each one in a separate compartment ...

so:

1.1 for electric propulsion, regardless of type, .8 for diesel-mechanic, .9 for hybrid-mechanic?

BTW anybody seen any evidence ever of hydraulic propulsion being used?

Hi there...

Looking through this thread again I noticed we haven´t agreed on a cataloque of benefits for those propulsion systems. LA proposed to increase the range of purly diesel powered ships by 50% and increase the damage resistance (hull points? floatation points? both?) of electric driven ships by 10%.

Does the board agree? If so, anything else? If not, what to change?

Regards,

HoOmAn

ahh, not quite. I suggest that the range of ships that use Diesel engines to achieve the cruising speed given in the SS file increases by 50% at that speed or lower speed.

Whatever rules you two can agree on I'll be happy to endorse, as you two seem to have the most knowledge on the subject. The hardest part is to get you two to agree!

LOL, naah, I think that'll be easy in this case. Most of the work is done.

So what benefits do you propose, LA?

well,

50% range increase at cruising speed or below for hybrid ships, 50% range increase overall for pure diesel propelled ships.

10% range increase at cruise for turbo-electric ships

10-20% (rather 20%) increase in damage resistance.

any more ideas?

cheers

Bernhard

10-20% dmg. red. (~15%) sounds okay to me for turbo-electric driven ships. IIRC, that´s where you first mentioned an increased dmg. red. I don´t see diesels to get that because they still need relatively large rooms and complex and large gears. Further more they don´t run half submerged as do turbines (the good ones at least).

50% increased range for diesels at all speeds and 50% bonus at cruising speed for hybrids makes sense too but...

Why an increased range for turbo-electrics? Those ships boilers burn oil as fast as if they had direct drive...

Quoted

Why an increased range for turbo-electrics? Those ships boilers burn oil as fast as if they had direct drive...

read the article on the US turbo-electric ships on Warships1. They were more efficient because they could run 1 turbine in an efficient power range for cruise rather than 4 turbines in an unefficient one - let's not forget that steam turbines as gas turbines are most efficient at full power.

And why do diesel-electrics need complex and large gears? they drive individual generators - the gearing is electric so to speak. Therefore they can reside in individual romms the same way turbines can. one can also use more smaller diesels, making for nice compartmentation.

LA,

you first sounded as if you´d apply an increased damage reduction to all diesel and hybrid variants, not electric driven ships only. Thus I wondered.

"And why do diesel-electrics need complex and large gears? they drive individual generators - the gearing is electric so to speak. Therefore they can reside in individual romms the same way turbines can. one can also use more smaller diesels, making for nice compartmentation."

See, I was talking about purely diesel powered units. You need complex gears if you want to put together several diesels to drive a shaft. In fact, the gears used on the PB were really heavy and large, causing much headache early in the design process and sometimes turing trials.

So to sum up the benefits:

NOTE! I have decreased range benefits for mixed propulsion. While I think LAs idea to allow a high benefit for cruising range is a good one I don´t see how we can handle overall range. A ship seldomly sails at cruising speed all the time. To make life easier (KISS) I´d cut those benefits but now they´ll always apply to ships with mixed propulsion and spring* sheets can be easily modified once a ship is designed.

Diesels, geared: range +50%

Diesels, electric: range +50%, dmg. red. +10%

Turbo-electric: range +10%, dmg. red. +10%

Mixed propulsion, geared: range +25%

Mixed propulsion, electric: range +25%, +10% damage reduction

Please carefully compare the benefits to the extra weight to spend and keep in mind balance has to be kept.

If nobody intervenes I´ll copy that into the infrastructure rules.

Regards,

HoOmAn

that's a classical 'yes but' - I disagree on the hybrids. the range given in Springsharp is _at_ cruising speed. all we are doing is changing the propulsion at that speed, ie gaining the increased fuel economy. The range of a ship does decrease once it exceeds that speed anyway. All the figure '10000nm@15 knots' says is that that ship could run 10000nm at a constant speed of 15 knots. It is purely theoretical and does not allow for real life use anyway. The fact that a hybrid would loose proportionally more range when going to full speed than a turbine-only ship gets a bit too detailed for our general set of rules IMHO - especialy since we are not simulating that with the non-hybrids anyway. So ceteres paribus I am for

Mixed propulsion, geared: range +50%

Mixed propulsion, electric: range +50%, +10% damage reduction

apart from that I agree. And my apologies for being unclear.

I just hope now that nobody comes up with electric and mechanical combined, or hydraulic.....

While I understand your concerns, LA, I disagree.

We´ve to do mixed calculations for range. I think that´s necessary when we keep in mind that we are also trying to find a way to develop all this into some kind of game rules. From this point of view mixed propulsion would get too much benefit for costs (weight) too low.

All this range stuff is purely theoretical, for sure, and as long as we don´t run a war (as long as we haven´t rules for that) it doesn´t matter. But it will be only a question of time until we get such rules.

So either we need a rule to calculate range in relation to speed - and that one will be way too difficult - or we have to follow KISS. From your posts I get the message you´re also prefering KISS - we just disagree on the percentage for mixed propulsion. How about 30%? No idea if that´s realistic but I can´t even proof that 50% would be...

Please note that even without a war we might be forced to use our ships at much higher average speeds than what is written down as "cruising speed" in spring*. As an example there was the high speed cruise my Royals did to get to the funeral of the Nordmark King. To get there within the timelimit set by Pengolodh it was necessary to cruise at different speeds between stops to refuel - and all those speeds were higher than what I had in mind when designing the ships cruising speed. Nearly got a headache while trying to find a route that is both quick and provides enough refuel stations.

It´s just a single example but it shows that there are reasons to be careful when talking about range or cruising range in particular.

What do you think? Do we agree on keeping it simple and in relation to costs (further keep dmg. red. in mind for electric)? Do we agree on 30%?

ya see - I don't think we are getting each other's point. We are using SS's assumption for steam turbine driven ships with geared transmission. This assumption is based on a constant speed of x knots (cruising speed field in SpringSharp). If you say we have to assume varying speeds then we will have to modify Springsharp's output as well. Since I don't want that, following the KISS principle, I'd like to treat cruising as cruising and thus give the full 50% benefit. If this still isn't clear - just look me up in ICQ and we can hash it out there.