As another consideration, foil shafts / cores are usually located at a position corresponding to the thickest cross-section of the foil, such that the actuating shaft and endoskeleton can be made as strong as possible in bending and torsional modes (greatest strength / weight ratio possible at maximum shaft diameter). The stiffer you can make the control surface, the less tendency it will have to vibrate in the presence of vortex shedding.
-Sean
On Aug 29, 2008, bottomgun@mindspring.com wrote:
Dean,
The 30% forward of the rudder post eases the force required to move the rudder but yet still allow the rudder to self center when a helm is released.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Recon1st@aol.com
Sent: Friday, August 29, 2008 10:30 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] U.S.S. Albacore Dive Brakes
Jay you bring up a point I had not considered.
30% in front of rudder post.
I had planned for 0% with a stationary leading edge. My idea was to remove any entanglement
problems. No edge sticking out to grab things. Smooth lines in all operational positions.
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Is the only concern just rudder pressure required, or am I missing something?
I am using hydraulics for control, so should have plenty of force to operate
the control planes.
Dean
Zero angle of attack and they were lucky to be alive. Speed is mentioned in the Albacore book form the Museum and/or Palomar’s 2nd volume on the history of US subs…I can neither confirm nor deny the facts in those texts.
The standard design criteria for an airfoil-shaped rudder is to have 30% in front of the rudder post for near balanced operation. I think your logic is flawed in your concept for your rudders.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Thursday, August 28, 2008 5:21 PM
To: PSUBSorg
Subject: [PSUBS-MAILIST] U.S.S. Albacore Dive Brakes
Hello Ray,
Interesting information. Did they say at what angle of attack they were when they deployed the braking flaps, or how fast they were going at the time? The speed might of been left out because of it being classified. Did it say any thing about whether of not all the flaps opened up at the same time properly. If the flaps towards the bottom opened up first they would make the sub point down very quickly.
I would think that what ever direction you were heading, the brakes if designed and functioning properly, would simply slow you down without changing your heading. To simplify the braking flaps on my sub designs I'm only thinking about having one on each side towards the back of the hull, or the two flaps on each wing, one opening up and one down, or a totally new system installed instead of a basic single rudder, like I have on my K-250.
The new system would be used for steering and braking. It would basically consist of two rudders about two feet apart or sandwiched together. Each rudder can only rotate 90 degrees towards the side they are one, and are controlled individually by a foot peddle that is just to control that one flap. This way you can move one and steer or move both and brake and/or steer. This can be a totally manual system, a partly manual system with a hydraulic assist like used in a car, or fly by wire controlled hydraulic, electric, or pneumatic actuator controlled. I'm designing a system like this to be installed on my K-250
For the purely manual configuration the steering/braking flaps need to have the pivot point back from the leading edge a certain amount to help you in moving the flaps with the assist of the water. My friend Doc, the inventor of the Bionic Dolphin told me how much it should be, but at the moment I'm not able to locate the data. I think it was about 30 percent surface area should be forward of the pivot point. They do this sort of thing one the elevator of planes as well. But they don't look to have as much as 30 percent.
Your resident possibility thinker. ;)'
Regards,
Brent Hartwig
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Hi Dean,
The U.S.S. Albacore had dive brakes around her circumference behind the sail.
The book "U.S.S Albacore" by Robert P. Largess says on pages 102 to 105 that they were a mistake. One time they were tried the sub lost control and bottomed at 400 feet. Another time the brakes were to be flapped to create an acoustical signal. A hydraulic seal failed and water pressure force hydraulic fluid into the engine room.
The brakes were immediately removed and were never tried again on another US sub.
Regards,
Ray
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