What is the offset in a seaplane's hull?
$begingroup$
I noticed there is a little offset in a seaplane's hull (highlighted in the following picture). I suppose this is useful as it exists in all the seaplanes I know.
It appears to be neither a hydrodynamic nor aerodynamic feature. I could not find clue by myself as I don't know this feature's name.
My question, what is its name and purpose?
(wikimedia.org)
aircraft-design feature-identification fuselage seaplane
edited 2 days ago
Notts90
2,13231640
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
$endgroup$
add a comment |
$begingroup$
I noticed there is a little offset in a seaplane's hull (highlighted in the following picture). I suppose this is useful as it exists in all the seaplanes I know.
It appears to be neither a hydrodynamic nor aerodynamic feature. I could not find clue by myself as I don't know this feature's name.
My question, what is its name and purpose?
(wikimedia.org)
aircraft-design feature-identification fuselage seaplane
edited 2 days ago
Notts90
2,13231640
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
$endgroup$
add a comment |
$begingroup$
I noticed there is a little offset in a seaplane's hull (highlighted in the following picture). I suppose this is useful as it exists in all the seaplanes I know.
It appears to be neither a hydrodynamic nor aerodynamic feature. I could not find clue by myself as I don't know this feature's name.
My question, what is its name and purpose?
(wikimedia.org)
aircraft-design feature-identification fuselage seaplane
edited 2 days ago
Notts90
2,13231640
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
$endgroup$
I noticed there is a little offset in a seaplane's hull (highlighted in the following picture). I suppose this is useful as it exists in all the seaplanes I know.
It appears to be neither a hydrodynamic nor aerodynamic feature. I could not find clue by myself as I don't know this feature's name.
My question, what is its name and purpose?
(wikimedia.org)
aircraft-design feature-identification fuselage seaplane
aircraft-design feature-identification fuselage seaplane
edited 2 days ago
Notts90
2,13231640
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
edited 2 days ago
Notts90
2,13231640
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
edited 2 days ago
Notts90
2,13231640
edited 2 days ago
Notts90
2,13231640
edited 2 days ago
Notts90
2,13231640
2,13231640
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
asked Apr 6 at 12:09
Manu HManu H
5,6841060139
5,6841060139
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.
However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.
edited yesterday
Federico♦
26.4k16106157
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
$endgroup$
8
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
2
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
|
show 1 more comment
$begingroup$
It's called a hull step. Below is with and without:
It reduces water drag. As the plane gains speed and the aft body is lifted, only the forward hull will be in contact with the water.
Source: Laté 631 Replica - Chapter 3 - Hydrodynamics
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
$endgroup$
add a comment |
$begingroup$
As everybody has said, it's called a 'step'.
But it's nothing to do with buoyancy, it's to do with the opposite effect - water suction. Without the step you will never get the airplane off the water simply due to the suction of the water clinging onto the airplane.
The step forces a break in the water-suction, in the case of the Catalina above probably halving it, which then allows the lift of the airplane to overpower the remaining water suction.
answered yesterday
RACRAC
2,55559
$endgroup$
add a comment |
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3 Answers
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active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.
However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.
edited yesterday
Federico♦
26.4k16106157
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
$endgroup$
8
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
2
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
|
show 1 more comment
$begingroup$
That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.
However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.
edited yesterday
Federico♦
26.4k16106157
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
$endgroup$
8
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
2
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
|
show 1 more comment
$begingroup$
That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.
However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.
edited yesterday
Federico♦
26.4k16106157
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
$endgroup$
That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.
However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.
edited yesterday
Federico♦
26.4k16106157
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
edited yesterday
Federico♦
26.4k16106157
edited yesterday
Federico♦
26.4k16106157
edited yesterday
Federico♦
26.4k16106157
26.4k16106157
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
answered Apr 6 at 12:32
HobbesHobbes
4,4001117
4,4001117
8
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
2
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
|
show 1 more comment
8
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
2
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
8
8
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
$begingroup$
Re the drag in flight, an obvious question would be whether anyone had a retractable fairing behind the step to solve that problem? I hit Google and found a few places speculating about that (including US patent US6042052A in 1998), but no evidence of designers actually using one.
$endgroup$
– Graham
Apr 6 at 23:41
2
2
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@Graham I think the demand for better sea planes died around the time the Sea Dart and the Caspian Sea Monster. (Both of which incidentally had a different solution to the lift off from water problem than the step.) So lots of cool ideas but nobody to pay for actually using them.
$endgroup$
– Ville Niemi
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
@VilleNiemi Yes, that was my thinking too. It did seem like something they could have tried before then, but I guess no-one did.
$endgroup$
– Graham
2 days ago
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
A retractable fairing would complicate the design: the fairing has to seal perfectly against the step when it's extended, otherwise you're creating a giant scoop. It has to be sturdy enough not to be ripped off by the water. etc.
$endgroup$
– Hobbes
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
$begingroup$
No, the angled part allows for rotating. The step reduces water drag.
$endgroup$
– bogl
yesterday
|
show 1 more comment
$begingroup$
It's called a hull step. Below is with and without:
It reduces water drag. As the plane gains speed and the aft body is lifted, only the forward hull will be in contact with the water.
Source: Laté 631 Replica - Chapter 3 - Hydrodynamics
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
$endgroup$
add a comment |
$begingroup$
It's called a hull step. Below is with and without:
It reduces water drag. As the plane gains speed and the aft body is lifted, only the forward hull will be in contact with the water.
Source: Laté 631 Replica - Chapter 3 - Hydrodynamics
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
$endgroup$
add a comment |
$begingroup$
It's called a hull step. Below is with and without:
It reduces water drag. As the plane gains speed and the aft body is lifted, only the forward hull will be in contact with the water.
Source: Laté 631 Replica - Chapter 3 - Hydrodynamics
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
$endgroup$
It's called a hull step. Below is with and without:
It reduces water drag. As the plane gains speed and the aft body is lifted, only the forward hull will be in contact with the water.
Source: Laté 631 Replica - Chapter 3 - Hydrodynamics
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
answered Apr 6 at 12:32
ymb1ymb1
70.1k7225372
70.1k7225372
add a comment |
add a comment |
$begingroup$
As everybody has said, it's called a 'step'.
But it's nothing to do with buoyancy, it's to do with the opposite effect - water suction. Without the step you will never get the airplane off the water simply due to the suction of the water clinging onto the airplane.
The step forces a break in the water-suction, in the case of the Catalina above probably halving it, which then allows the lift of the airplane to overpower the remaining water suction.
answered yesterday
RACRAC
2,55559
$endgroup$
add a comment |
$begingroup$
As everybody has said, it's called a 'step'.
But it's nothing to do with buoyancy, it's to do with the opposite effect - water suction. Without the step you will never get the airplane off the water simply due to the suction of the water clinging onto the airplane.
The step forces a break in the water-suction, in the case of the Catalina above probably halving it, which then allows the lift of the airplane to overpower the remaining water suction.
answered yesterday
RACRAC
2,55559
$endgroup$
add a comment |
$begingroup$
As everybody has said, it's called a 'step'.
But it's nothing to do with buoyancy, it's to do with the opposite effect - water suction. Without the step you will never get the airplane off the water simply due to the suction of the water clinging onto the airplane.
The step forces a break in the water-suction, in the case of the Catalina above probably halving it, which then allows the lift of the airplane to overpower the remaining water suction.
answered yesterday
RACRAC
2,55559
$endgroup$
As everybody has said, it's called a 'step'.
But it's nothing to do with buoyancy, it's to do with the opposite effect - water suction. Without the step you will never get the airplane off the water simply due to the suction of the water clinging onto the airplane.
The step forces a break in the water-suction, in the case of the Catalina above probably halving it, which then allows the lift of the airplane to overpower the remaining water suction.
answered yesterday
RACRAC
2,55559
answered yesterday
RACRAC
2,55559
answered yesterday
RACRAC
2,55559
answered yesterday
RACRAC
2,55559
2,55559
add a comment |
add a comment |
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