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#1
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Bubble injection behind the step on seaplanes
I have been reading up on seaplanes (Seaplane Operations, by Cesare Baj
and Dale DeRemer) and one frequently repeated fact is that it is very hard to get a seaplane up on the step on glassy water, because the lack of bubbles under the float/hull causes the heel of the float/hull to adhere to the water surface. This seems like an easily solved problem -- inject bubbles behind the step. Clearly if it were that easy it would be common practice. What am I missing? Here is my hull profile at the step: To Heel -- Step -- To Bow _____________________ O| / x|______________________/ When moving at speed through the water, it seems that at point O there should be a circulating eddy or turbulence, and at point x there should be significant suction, yes? So if we attach at point x a hose, whose one endpoint is at x and the other is above waterline, without any further mechanics the low pressure at x should be sucking air through the hose and introducing a trail of bubbles, slipping past the turbulence at O and running along the undersurface of the heel. If we put in a bunch of such hoses, or one long hose running along the back of the step with a bunch of holes spaced along it, we should get a lot of bubbles. Yes? What am I missing? ~Adam |
#2
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Bubble injection behind the step on seaplanes
It's not a bad idea. You would have to build one and see if it works.
For all things seaplane go to www.seaplanes.org. They know a lot on there. |
#3
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Bubble injection behind the step on seaplanes
Yep! The concept works. The basic idea is at least 100 years old.
Some racing speed boats use this. JP "Adam Aulick" kirjoitti ... I have been reading up on seaplanes (Seaplane Operations, by Cesare Baj and Dale DeRemer) and one frequently repeated fact is that it is very hard to get a seaplane up on the step on glassy water, because the lack of bubbles under the float/hull causes the heel of the float/hull to adhere to the water surface. This seems like an easily solved problem -- inject bubbles behind the step. Clearly if it were that easy it would be common practice. What am I missing? Here is my hull profile at the step: To Heel -- Step -- To Bow _____________________ O| / x|______________________/ When moving at speed through the water, it seems that at point O there should be a circulating eddy or turbulence, and at point x there should be significant suction, yes? So if we attach at point x a hose, whose one endpoint is at x and the other is above waterline, without any further mechanics the low pressure at x should be sucking air through the hose and introducing a trail of bubbles, slipping past the turbulence at O and running along the undersurface of the heel. If we put in a bunch of such hoses, or one long hose running along the back of the step with a bunch of holes spaced along it, we should get a lot of bubbles. Yes? What am I missing? ~Adam |
#4
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Bubble injection behind the step on seaplanes
In article ,
Adam Aulick wrote: I have been reading up on seaplanes (Seaplane Operations, by Cesare Baj and Dale DeRemer) and one frequently repeated fact is that it is very hard to get a seaplane up on the step on glassy water, because the lack of bubbles under the float/hull causes the heel of the float/hull to adhere to the water surface. This seems like an easily solved problem -- inject bubbles behind the step. Clearly if it were that easy it would be common practice. What am I missing? Here is my hull profile at the step: To Heel -- Step -- To Bow _____________________ O| / x|______________________/ When moving at speed through the water, it seems that at point O there should be a circulating eddy or turbulence, and at point x there should be significant suction, yes? So if we attach at point x a hose, whose one endpoint is at x and the other is above waterline, without any further mechanics the low pressure at x should be sucking air through the hose and introducing a trail of bubbles, slipping past the turbulence at O and running along the undersurface of the heel. If we put in a bunch of such hoses, or one long hose running along the back of the step with a bunch of holes spaced along it, we should get a lot of bubbles. Yes? Look at the hull of any Lake Amphipian. |
#5
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Bubble injection behind the step on seaplanes
" What am I missing? ~Adam Simplicity...... You need to look at pictures of any large seaplanes to see how they get the step "energized". The Shin Meiwa, for example, uses fences along the fuse side to force a high volume of air into the step area. A fairly simple thing to do and you don't need to make hull penetrations to make it happen...... Have a great day Scott |
#6
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Bubble injection behind the step on seaplanes
JP wrote: Yep! The concept works. The basic idea is at least 100 years old. Indeed. The lapstrake construction of the Viking longboats carried bubbles down from the bow under the hull. People sailing modern replicas report a sort of 'surge' and an associated loss of rudder authority that corresponds to reaching a certain critical speed. -- FF |
#7
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Bubble injection behind the step on seaplanes
There is a picture about the subject ("Super Ventilated Positive Lift" in
this case) http://www.fountainpowerboats.com/te...ain/racing.htm JP "JP" kirjoitti ... Yep! The concept works. The basic idea is at least 100 years old. Some racing speed boats use this. JP |
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