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PT boats

thesmilingassassin

The Chosen One

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1

Monday, April 18th 2005, 6:03am

PT boats

Has anyone designed a suitable PT boat? Currently the design I'm tinkering with useing historical dementions of American Elco boats PT 10 to 19 gives me a negative tonnage rating, GUH?

Also most sorces on PT boats do not display the draft while the only sorce of mine that does states it as 1.52 to 1.6 meters, seems kinda deep for a PT boat.

LordArpad

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Monday, April 18th 2005, 8:54am

'dementions' is right ;-)

Spring* does indeed react demented when confronted with a planing hull

thesmilingassassin

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Monday, April 18th 2005, 9:53am

Is there any way around the problem?

Rooijen10

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Monday, April 18th 2005, 12:43pm

There is one way that I found out using a minor anomoly in SS (got a negative value somewhere and no, I did not use a negative value), but Ian told me that at that point SS was not working properly. I'll send you the sim of my PT boat once I get home so that you have an idea how it looks like. The speed was there, but the design was using somthing like 12,000 shp!

Red Admiral

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5

Monday, April 18th 2005, 5:03pm

It can't be done. SS assumes the engines to be below the waterline. With a planing hull doing 40+knts you tend to bounce from wave crest to crest. i.e. there is more or less 0 draught, and thus no room to put the engines.

Ithekro

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Monday, April 18th 2005, 5:42pm

Then would you then sim it as resting in the water at no speed? or with water nearly to freeboard?

thesmilingassassin

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Monday, April 18th 2005, 6:58pm

Thats what I was thinking, but still the speed and hull strength will be terribly inaccurate.

Ithekro

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Monday, April 18th 2005, 7:48pm

Do two. One at low and one at speed and mix the two?

Commodore Green

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9

Monday, April 18th 2005, 7:53pm

Quoted

Originally posted by thesmilingassassin
Has anyone designed a suitable PT boat? Currently the design I'm tinkering with useing historical dementions of American Elco boats PT 10 to 19 gives me a negative tonnage rating, GUH?

Also most sorces on PT boats do not display the draft while the only sorce of mine that does states it as 1.52 to 1.6 meters, seems kinda deep for a PT boat.


PT Boats had their draft markings on the stern, and typical loaded draft was 5.5 feet when stationary, when travelling at full speed this dropped to about 6 inches, and on the boat that ELCO trialed their "Slipper" device on the draft was reduced to ZERO! only the props and rudders were left in the water!! Speed jumped up by about 10 kts, but she was a little sluggish in the turns.