Re: [PSUBS-MAILIST] Wet-sub propulsion stability and X-tail

[Ian Roxborough <irox@ix.netcom.com>]

Hi,

the software in development that Alec speaks of could be used for
controlling an X tail.  The software will be avaliable under the
GPL once an initial version is complete (there is a 'no warrently'
disclaimer with the GPL, so it's not my fault if something goes wrong
or it fails).

I know they are a few other embedded system developers on this list,
so I to hope get some peer review on what I write.  Also, I will
(hopefully) get to present information about this project at the
2004 Psubs conference.

However, there is also a cheap hardware solution which is used for
controling the X-tails for model submarines (it's second from the
bottom):
  http://www.rcboats.com/electronics.html

Maybe the chip solution could be used for controlling a psub with a
X tail as well, probably with minor modification so large currents
don't have to pass through the control circuit.

Ian.

On Fri, 21 May 2004 15:23:29 -0400
"Alec Smyth" <Asmyth@changepoint.com> wrote:

> Jonathan,
> 
> I love creative designs. This one has elements that have been done
> before, but it wouldn't be an easy one to pull off. Especially the
> retracting fins bit, that sounds pretty cool yet hard! 
> 
> As for the first part about a high-speed planning wet sub hull, Herve
> Jauvert of Seahorse Submersibles recently did just that, and sells it as
> a special forces military sub. However, rather than retracting the
> outboard, I believe he is pressure-compensating it and leaving it
> outside during dives. I haven't asked him, but I surmise that from
> photos. 
> 
> On the topic of an X tail, I don't know anyone who has implemented it.
> However, my own project has a V tail, which from a control perspective
> is very similar. The only way I could find to implement it was with
> independent electrical servos moving each control surface, and the
> signals being electronically processed. There must be a mechanical way
> to do this, as the Beechcraft Bonanza proves, but the mechanical
> approach stumped me. I first implemented this with oversized toy servos,
> but Ian Roxborough is currently writing software to do the servo control
> on a Unix platform with industrial servos instead. If you can make your
> way to the 2004 convention, I think you'll get some detailed info on the
> approach.
> 
> Cheers,
> 
> Alec
> 
>    
> 
> -----Original Message-----
> From: Jonathan Huntoon [mailto:jonathanhuntoon@hotmail.com] 
> Sent: Friday, May 21, 2004 2:10 PM
> To: Personal_Submersibles@psubs.org
> Subject: [PSUBS-MAILIST] Wet-sub propulsion stability and X-tail
> 
> Hello Everyone,
> 
> 	I have been an avid reader of the psubs website for quite
> sometime. My 
> purpose in this email is two fold. First, I have decided to join the
> mailing 
> list, and I thought I would make my formal introduction. I currently a 
> college student and I have been interested in submersibles since my
> senior 
> year of High School. I undertook an ambitious project to build a one-man
> wet 
> submersible. Using trolling motors, batteries, plywood and PVC, I
> created 
> what many considered a death trap, but it worked! Due to problems with 
> electrical insulation, the system only performed admirably in fresh
> water, 
> going 5 or 6 knots. I vowed, that if I ever had the time, money, and 
> inclination, that I would go back and try building another wet sub, 
> correcting all the problems with the first design.
> 	My second purpose in this email is to ask a few questions. I
> have done my 
> best to go back and read all the topics applicable to my situation. I
> found 
> very little information however, on my specific questions. I think the
> best 
> thing to do would be to give everyone a little background into my new 
> project, in hopes of giving you a picture of my ideas. I am majoring in 
> engineering, and I have experience in CAD. So someday I can attach some 
> design pictures.
> 	I case you haven't figured out by this point, I have decided to
> make a new 
> submersible. I was comforted to know I was not alone in my efforts. Most
> 
> people couldn't believe I made my first sub, so I thought they would not
> be 
> surprised when I started another. I was wrong (It is difficult sometimes
> 
> when everyone thinks you're completely nuts).
> 	I have made every effort in my new sub to follow hydrodynamics.
> As I 
> mentioned before my sub is a wet sub, it will hold two people. The sub 
> design is 14' long and 4' diameter at the widest point, which is 5'6"
> down 
> the length. The sub follows a tear drop contour and is as
> hydro-dynamically 
> sound as I can make it and still keep the project manageable.
> 	I wanted to make my project unique, and so I decided to try to
> come up with 
> one solution to the age old question of sub endurance and speed. Because
> my 
> vehicle is a wet sub, the driver must wear SCUBA gear to operate it. 
> Therefore it is not practical to drive the vehicle out to the dive site.
> I 
> wanted a way to quickly get the sub to the dive site, dive down,
> surface, 
> and then quickly drive the vehicle home. As I am sure you all know the
> ideal 
> hydrodynamic shape underwater performs very poorly on the surface. As
> waves 
> pile up on the hull, the vehicle looses all efficiency. I asked myself
> how 
> to fix this many times, and the solution seemed to be staring me in the 
> face. One of the advantages that wet subs have is their weight. I can
> make 
> my hull out of fiberglass. What would happen if I added enough power to
> the 
> vehicle to get the whole hull to hydroplane out of the water? The way
> the 
> sub is contoured it might work.
> 	I have designed my sub to (hopefully) hold a 40HP e-start
> outboard motor. 
> When the sub is on the surface, the outboard will propel the entire sub
> out 
> of the water at a high rate of speed. I can drain the hull and close it 
> making it a surface boat. Underwater I will withdraw the outboard into
> the 
> hull and store it in a pressure compensated compartment. This minimizes 
> flooding issues with the motor, and eliminates the hull protrusion.
> 	When I was faced with the obstacle of how I would steer my
> submersible, I 
> immediately drawn to the cruciform arrangement. I am a big proponent of
> the 
> KISS principle. Underwater steering can be accomplished with the
> cruciform, 
> but when the sub is hydroplaning the tail presents a problem. Even if I 
> extend the tail through some means so that a section of the rudder is 
> underwater, when the boat travels at high speed there could be a real 
> instability. Realistically the hull could be completely out of the
> water. I 
> was originally only going to have the motor stationary, but even if I
> rigged 
> it to turn a little, is there a danger of the sub getting out of
> control? I 
> have seen too many movies of those high speed boats flipping out of
> control 
> and hurting people. I know I am inside the sub, but it can still hurt me
> it 
> flips at 30+ mph.
> 	I decided a way I might combat this instability it to use an
> X-tail. Some 
> navies around the world have opted for the tail because it gives 25%
> tighter 
> turns. I like it because I am considering using a piston to extend the
> lower 
> fins of the X into the water when the sub is at high speed, effectively 
> giving me 3 points of a stable tripod. Does this idea sound crazy? I
> could 
> turn the sub, but also adjust the hull pitch up and down.
> 	My last question is if anyone has experience dealing with X tail
> control 
> systems. Due to the complexity, I would need all four fins to be
> actuated 
> separately. I would need joystick control, and some sort of motor
> control 
> that could take my stick position and turn it into the proper fin
> position. 
> The trick is the forces off the fins are additive, so all four fins need
> to 
> work together.
> 	I realize this is a long email, but I look forward to reading
> anyone's 
> insights on the matter.
> 						Best Regards,
> 
> 	
> Jonathan Huntoon
> 
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