SOT: Naval Architects of Lore May Have Been Right After All

[Symon]

ORIGINAL: pws1225

ORIGINAL: Symon

ORIGINAL: pws1225
And just what the frig is a Froude limit? I'd check Wikipedia but that source seems discredited now. [&:]

It's the area just past the second gator outside the city limits of Tate's Hell [:D] J

Well frig me! I shoulda knowed that. [8D]

[:D][:D]
It’s kinda funny because I’m visiting my sister, who’s a designer at GD Electric Boat in Groton. I asked her the question .. “so .. just what the frik is a Froude limit?” You would not believe the “look” I got. Anyway, this is our collective take.

Froude number is ‘jargon’ that’s used as a way of talking about hull speed and wave resistance (drag). The energy to propel a hull through water is transferred to the water, creating standing waves (bow and stern waves). As speed varies, these waves change shape, magnitude and angle (wavelength, phase speed, etc. for the tech heads); they constructively and destructively interfere with one another. Points of interference have a pronounced effect on drag. Drag is relatively proportionally linear to power (speed) up to a first interaction point where it increases dramatically because of a shift in the wave train characteristic.

A simplistic way of looking at it, but one suitable for game terms, is this is the ‘economic’ cruise speed point. A second interaction point is where the ship kinda, sorta, ‘outruns’ the bow wave, thereby effectively constructively converging it with the stern wave, causing a huge shift in the wave train characteristic. Simplistically, this is the vessel’s effective hull speed, because power to make another half knot would be prohibitive (if it even exists) against the added drag.

The Froude number is the characteristic hydrodynamic flow velocity divided by the square root of a characteristic length. Because all vessels have different lengths, hull forms, etc., the Froude number permits comparison between heterogeneous vessels, because standing wave pattern generation is similar at similar Froude numbers for dissimilar vessels.

The Froude limits are (very simplistically) those points where the wavelength of the characteristic standing wave pattern is approximately ½ and 1 of the characteristic length of the vessel (tech heads can think of pi and 2pi superposition). It wouldn’t be too far off to think of Froude numbers (limits) as the hydrodynamic equivalent of Mach numbers.

Hope this helps. JWE

[pws1225]

Hory crap! I better just stick with hull speed. [:'(]

[JockJimmy]

Thanks for all that. Just one more question - Does the pointy end go at the front or back? [&:]

[warspite1]

ORIGINAL: JockJimmy

Thanks for all that. Just one more question - Does the pointy end go at the front or back? [&:]

warspite1

Neither, the front bit of the boat is called Starbord.

[witpqs]

ORIGINAL: warspite1

ORIGINAL: JockJimmy

Thanks for all that. Just one more question - Does the pointy end go at the front or back? [&:]

warspite1

Neither, the front bit of the boat is called Starbord.

I didn't know that boats have bits. [:'(]

[warspite1]

ORIGINAL: witpqs

ORIGINAL: warspite1

ORIGINAL: JockJimmy

Thanks for all that. Just one more question - Does the pointy end go at the front or back? [&:]

warspite1

Neither, the front bit of the boat is called Starbord.

I didn't know that boats have bits. [:'(]

warspite1

Well to be fair witpqs I am not surprised. Some of the ignorance of boaty things round here is staggering. If you need to know more about stuff just let me know.

[Sardaukar]

ORIGINAL: warspite1

ORIGINAL: JockJimmy

Thanks for all that. Just one more question - Does the pointy end go at the front or back? [&:]

warspite1

Neither, the front bit of the boat is called Starbord.

These paramilitary yacht clubs have their own language. You know..port is where they drink port, starboard is where they gaze stars, bow is where they do archery and stern is the..stern place where guys shoveling coal are... [:'(]

[witpqs]

ORIGINAL: warspite1

ORIGINAL: witpqs

ORIGINAL: warspite1


warspite1

Neither, the front bit of the boat is called Starbord.

I didn't know that boats have bits. [:'(]

warspite1

Well to be fair witpqs I am not surprised. Some of the ignorance of boaty things round here is staggering. If you need to know more about stuff just let me know.

But, but, but I always boats were referred to as 'she'! [:D]

[geofflambert]

ORIGINAL: Symon

ORIGINAL: pws1225

ORIGINAL: Symon

It's the area just past the second gator outside the city limits of Tate's Hell [:D] J

Well frig me! I shoulda knowed that. [8D]

[:D][:D]
It’s kinda funny because I’m visiting my sister, who’s a designer at GD Electric Boat in Groton. I asked her the question .. “so .. just what the frik is a Froude limit?” You would not believe the “look” I got. Anyway, this is our collective take.

Froude number is ‘jargon’ that’s used as a way of talking about hull speed and wave resistance (drag). The energy to propel a hull through water is transferred to the water, creating standing waves (bow and stern waves). As speed varies, these waves change shape, magnitude and angle (wavelength, phase speed, etc. for the tech heads); they constructively and destructively interfere with one another. Points of interference have a pronounced effect on drag. Drag is relatively proportionally linear to power (speed) up to a first interaction point where it increases dramatically because of a shift in the wave train characteristic.

A simplistic way of looking at it, but one suitable for game terms, is this is the ‘economic’ cruise speed point. A second interaction point is where the ship kinda, sorta, ‘outruns’ the bow wave, thereby effectively constructively converging it with the stern wave, causing a huge shift in the wave train characteristic. Simplistically, this is the vessel’s effective hull speed, because power to make another half knot would be prohibitive (if it even exists) against the added drag.

The Froude number is the characteristic hydrodynamic flow velocity divided by the square root of a characteristic length. Because all vessels have different lengths, hull forms, etc., the Froude number permits comparison between heterogeneous vessels, because standing wave pattern generation is similar at similar Froude numbers for dissimilar vessels.

The Froude limits are (very simplistically) those points where the wavelength of the characteristic standing wave pattern is approximately ½ and 1 of the characteristic length of the vessel (tech heads can think of pi and 2pi superposition). It wouldn’t be too far off to think of Froude numbers (limits) as the hydrodynamic equivalent of Mach numbers.

Hope this helps. JWE

JWE, this is probably not your best post, but I'm thinking it's the best I've seen, at least for a while. Thank you for this instructive post. Let me digress. It's likely not the best I've seen from you, in part because I've noticed you craft excellent posts frequently. You also know a lot of stuff most of the rest of us don't know. I don't know what the WITPAE gamers would do without your input. You are a more important asset to this forum than me, without question. That's all.

[AW1Steve]

ORIGINAL: geofflambert

ORIGINAL: Symon

ORIGINAL: pws1225

Well frig me! I shoulda knowed that. [8D]

[:D][:D]
It’s kinda funny because I’m visiting my sister, who’s a designer at GD Electric Boat in Groton. I asked her the question .. “so .. just what the frik is a Froude limit?” You would not believe the “look” I got. Anyway, this is our collective take.

Froude number is ‘jargon’ that’s used as a way of talking about hull speed and wave resistance (drag). The energy to propel a hull through water is transferred to the water, creating standing waves (bow and stern waves). As speed varies, these waves change shape, magnitude and angle (wavelength, phase speed, etc. for the tech heads); they constructively and destructively interfere with one another. Points of interference have a pronounced effect on drag. Drag is relatively proportionally linear to power (speed) up to a first interaction point where it increases dramatically because of a shift in the wave train characteristic.

A simplistic way of looking at it, but one suitable for game terms, is this is the ‘economic’ cruise speed point. A second interaction point is where the ship kinda, sorta, ‘outruns’ the bow wave, thereby effectively constructively converging it with the stern wave, causing a huge shift in the wave train characteristic. Simplistically, this is the vessel’s effective hull speed, because power to make another half knot would be prohibitive (if it even exists) against the added drag.

The Froude number is the characteristic hydrodynamic flow velocity divided by the square root of a characteristic length. Because all vessels have different lengths, hull forms, etc., the Froude number permits comparison between heterogeneous vessels, because standing wave pattern generation is similar at similar Froude numbers for dissimilar vessels.

The Froude limits are (very simplistically) those points where the wavelength of the characteristic standing wave pattern is approximately ½ and 1 of the characteristic length of the vessel (tech heads can think of pi and 2pi superposition). It wouldn’t be too far off to think of Froude numbers (limits) as the hydrodynamic equivalent of Mach numbers.

Hope this helps. JWE

JWE, this is probably not your best post, but I'm thinking it's the best I've seen, at least for a while. Thank you for this instructive post. Let me digress. It's likely not the best I've seen from you, in part because I've noticed you craft excellent posts frequently. You also know a lot of stuff most of the rest of us don't know. I don't know what the WITPAE gamers would do without your input. You are a more important asset to this forum than me, without question. That's all.

+1.

[Symon]

ORIGINAL: geofflambert
JWE, this is probably not your best post, but I'm thinking it's the best I've seen, at least for a while. Thank you for this instructive post. Let me digress. It's likely not the best I've seen from you, in part because I've noticed you craft excellent posts frequently. You also know a lot of stuff most of the rest of us don't know. I don't know what the WITPAE gamers would do without your input. You are a more important asset to this forum than me, without question. That's all.

You are right Gorn, it wasn’t all that great. Maybe because my sister has submarines on the brain and they act a bit different from surface vessels. She’s a real tech freak, too. Some of it might not be too appropriate/correct when applied to surface ships, but what the hey, good enough for Govt. work. Anyway, thanks for the nice comments, ya’ll. I’ll try to do better and keep it simple next time. [:)] Ciao. JWE

[AW1Steve]

ORIGINAL: Symon

ORIGINAL: geofflambert
JWE, this is probably not your best post, but I'm thinking it's the best I've seen, at least for a while. Thank you for this instructive post. Let me digress. It's likely not the best I've seen from you, in part because I've noticed you craft excellent posts frequently. You also know a lot of stuff most of the rest of us don't know. I don't know what the WITPAE gamers would do without your input. You are a more important asset to this forum than me, without question. That's all.

You are right Gorn, it wasn’t all that great. Maybe because my sister has submarines on the brain and they act a bit different from surface vessels. She’s a real tech freak, too. Some of it might not be too appropriate/correct when applied to surface ships, but what the hey, good enough for Govt. work. Anyway, thanks for the nice comments, ya’ll. I’ll try to do better and keep it simple next time. [:)] Ciao. JWE

Yeah , I used to have submarines on the brain (except in my case it's what they call in dogs "chase instinct"). Good news, you can eventually have it wear off! [:D]

[Andav]

Here is another picture of the Texas with some of those wave things on the front and back bits.

Wa

[warspite1]

ORIGINAL: Andav


Here is another picture of the Texas with some of those wave things on the front and back bits.

Wa

warspite1

Nice picture of her starbord cutting through the wavy stuff, creating white frothy action down her side bits.

[witpqs]

ORIGINAL: warspite1

ORIGINAL: Andav


Here is another picture of the Texas with some of those wave things on the front and back bits.

Wa

warspite1

Nice picture of her starbord cutting through the wavy stuff, creating white frothy action down her side bits.

You silly boy. That foam is there to hide her bits!

[warspite1]

ORIGINAL: witpqs

ORIGINAL: warspite1

ORIGINAL: Andav


Here is another picture of the Texas with some of those wave things on the front and back bits.

Wa

warspite1

Nice picture of her starbord cutting through the wavy stuff, creating white frothy action down her side bits.

You silly boy. That foam is there to hide her bits!

warspite1

And you sir obviously know nothing about big boats an' £$%^. The foam is not there to hide her side bits but is in fact caused by the pointy starbord bit creating the wavy stuff that happens to hide her side bits, duh....

[witpqs]

ORIGINAL: warspite1

ORIGINAL: witpqs

ORIGINAL: warspite1


warspite1

Nice picture of her starbord cutting through the wavy stuff, creating white frothy action down her side bits.

You silly boy. That foam is there to hide her bits!

warspite1

And you sir obviously know nothing about big boats an' £$%^. The foam is not there to hide her side bits but is in fact caused by the pointy starbord bit creating the wavy stuff that happens to hide her side bits, duh....

Bits, bits - oh, bits!

These bits here make a smiley face!

11111111111111111111111111111111111111111111
11111111111111111111111111111111111111111111
11111111111110000111111111000011111111111111
11111111111110000111111111000011111111111111
11111111111110000111111111000011111111111111
11111111111111111111111111111111111111111111
11111111111111111110000011111111111111111111
11111111111111111110000011111111111111111111
11111111111111111110000011111111111111111111
11111111111111111110000011111111111111111111
11111111111111111110000011111111111111111111
11111111111111111111111111111111111111111111
11111111111111111111111111111111111111111111
11111111111000111111111111111000111111111111
11111111111000111111111111111000111111111111
11111111111000111111111111111000111111111111
11111111111000000000000000000000111111111111
11111111111000000000000000000000111111111111
11111111111111111111111111111111111111111111
11111111111111111111111111111111111111111111

[Lecivius]

Ok, this has gotten a bit off track

[warspite1]

ORIGINAL: Lecivius

Ok, this has gotten a bit off track

warspite1

Soz mate, I suspect its all got a bit too technical for you. I'll leave the subject there.

[;)]

[obvert]

ORIGINAL: AW1Steve

ORIGINAL: geofflambert

ORIGINAL: Symon



[:D][:D]
It’s kinda funny because I’m visiting my sister, who’s a designer at GD Electric Boat in Groton. I asked her the question .. “so .. just what the frik is a Froude limit?” You would not believe the “look” I got. Anyway, this is our collective take.

Froude number is ‘jargon’ that’s used as a way of talking about hull speed and wave resistance (drag). The energy to propel a hull through water is transferred to the water, creating standing waves (bow and stern waves). As speed varies, these waves change shape, magnitude and angle (wavelength, phase speed, etc. for the tech heads); they constructively and destructively interfere with one another. Points of interference have a pronounced effect on drag. Drag is relatively proportionally linear to power (speed) up to a first interaction point where it increases dramatically because of a shift in the wave train characteristic.

A simplistic way of looking at it, but one suitable for game terms, is this is the ‘economic’ cruise speed point. A second interaction point is where the ship kinda, sorta, ‘outruns’ the bow wave, thereby effectively constructively converging it with the stern wave, causing a huge shift in the wave train characteristic. Simplistically, this is the vessel’s effective hull speed, because power to make another half knot would be prohibitive (if it even exists) against the added drag.

The Froude number is the characteristic hydrodynamic flow velocity divided by the square root of a characteristic length. Because all vessels have different lengths, hull forms, etc., the Froude number permits comparison between heterogeneous vessels, because standing wave pattern generation is similar at similar Froude numbers for dissimilar vessels.

The Froude limits are (very simplistically) those points where the wavelength of the characteristic standing wave pattern is approximately ½ and 1 of the characteristic length of the vessel (tech heads can think of pi and 2pi superposition). It wouldn’t be too far off to think of Froude numbers (limits) as the hydrodynamic equivalent of Mach numbers.

Hope this helps. JWE

JWE, this is probably not your best post, but I'm thinking it's the best I've seen, at least for a while. Thank you for this instructive post. Let me digress. It's likely not the best I've seen from you, in part because I've noticed you craft excellent posts frequently. You also know a lot of stuff most of the rest of us don't know. I don't know what the WITPAE gamers would do without your input. You are a more important asset to this forum than me, without question. That's all.

+1.

+1

This stuff is amazing. Thanks for taking the time JWE