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View Full Version : Commerce Raider a bit weird?



Foehammer-1
03-07-2007, 04:38 PM
Here is what I noticed a while ago, when sailing out of Wilhelmshaven. It seemed that this big commerce raider was following me around. Anyways, the thing moved at 15 knots. I looked at it with free cam and noticed one thing- a VERY tiny propeller. Now, to go at 15 knots, C3's for example spin their huge blades at pretty much the same speed as the commerce raider spun his teeny-tiny one. How the HECK can it move with that propeller on??? Sorry, I got no screens to prove my point

klcarroll
03-07-2007, 04:48 PM
It's not the size, ....it's how you use it! http://forums.ubi.com/images/smilies/53.gif http://forums.ubi.com/images/smilies/53.gif http://forums.ubi.com/images/smilies/53.gif

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Stingray-65
03-07-2007, 05:34 PM
Originally posted by klcarroll:
It's not the size, ....it's how you use it! http://forums.ubi.com/images/smilies/53.gif http://forums.ubi.com/images/smilies/53.gif http://forums.ubi.com/images/smilies/53.gif

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Excellent! http://forums.ubi.com/images/smilies/winky.gif http://forums.ubi.com/images/smilies/59.gif

@ Foehammer
I guess IRL it would have to rotate at a higher RPM than the C3 with a bigger propellor.

blastomatic1759
03-07-2007, 05:56 PM
you could also inlcude clutch factor , clutches have alot to do with how a boat performs. kinda like drag racing , you get the right rear end , the right transmission , and a good engine , you get a fast car , boats/ships are kinda the same way. ive been looking for Wheel size , and Clutch ratios , between the U.S. subs , and the Uboats , it seems the U.S. subs had a faster surface speed than Uboats , but way less horsepower , im sure hull design has alot to do with it too , but im still looking around for info on the rest. im sure its in one of my books at home , but im stuck at work.

klcarroll
03-08-2007, 09:02 AM
I sorry to contradict you, but the Gato and Balao class boats "out-horsepowered" the German TypeIXb, both on the surface and submerged.

TypeIXb Diesel HP: - 4,400
TypeIXb Electric HP: - 1,000

Gato Diesel HP: - 5,400 (4 x 1350)
Gato Electric HP: - 2,740 (2 x 1370)

You are correct about the Hull making a big difference:

In "Displacement Type" hulls, the maximum possible speed is a function of length. The naval design term that deals with this factor is "Hull Speed".

Once the "period" of the bow and stern wave taken together equals the length of the vessel, the vessel is essentially trapped in the trough of her own self induced wave pattern, and "Max Hull Speed" has been reached.

Once a vessel's "Hull Speed" is reached, the application of more horsepower will not significantly increase the vessel's speed. The excess horsepower is drained away in the form of larger bow and stern waves.

So, the longer U.S. fleet boats have an inherent speed advantage over smaller boats.

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blastomatic1759
03-08-2007, 10:02 AM
AH , i misread that , i just thought the Gato was 2 x 1350 and not 4. oops. im still curious on wheelsizes and clutch ratios though.