Albacore continued

[He Who Shall Not Be Named]

Sail/bow planes is a must on the larger models. Smaller models, with their quick period of rotation, can get away with stern plane only control of pitch and depth. The 1/72 SKIPJACK is a joy to run at periscope depth with the sail planes active. I don't know how anyone can operate an r/c submarine realistically without 'em!

M

[greenman407]

There she sits........awaiting the Glib comparisons and confrontation to come.

[greenman407]

Since I am working on the 1/72 Moebius Skipjack, I thought that it might be interesting to compare its size and shape to the Albacore. For one thing, my version of the Albacore is an X Tail. I expect that the Skipjacks maneuverability will suffer If compared directly to the X tail. Also being a single propellor driven submarine I expect it to suffer from torque roll If not ballasted properly and too much throttle applied all at once. I can "Floor" my Albacore with no roll at all.
I remember when I was building my Albacore about 5 or 6 years ago. I didnt have enough ballast weight in her. When you advanced the throttle the thing would spin thru the water like a drill bit! It was so cool!!!
Also my plans with the Skipjack er...Scamp, is to use the New SAS subdriver with Gas backup.
Another cool difference is that the Scamp will have controllable sail planes. Im looking forward to exploring how much real affect they will have on operation.

[greenman407]

Now thats a thought.

[He Who Shall Not Be Named]

Yes........what you said. It did the exact same thing back when she had only one propellor.

Try another V-tail mixer, Mark.

David

[greenman407]

Yes........what you said. It did the exact same thing back when she had only one propellor.

[He Who Shall Not Be Named]

Assuming perfect torque matching between the two propellers, I'm wondering what would account as a source of the pitch up/down depending on which way you turn? Maybe something to do with the two staggard sets of control surfaces? More likely an asymmetrical mixing between transmitter and the two control surface servos?

Pictures, damit! Better yet: video!

[greenman407]

Thanks Kevin. Just to prove that last trip outs success was not a Fluke, I took her out again today. Excellent results again. I had fun with the ducks at the lake. I would try to sneek up on them, underwater. I can get pretty close before one of them would "Sence" something was coming up on them, then they panic. They must think that its an alligator.
This boat makes quite a wake , even with the periscope under the water. Moving at a good clip it leaves a large wake on the surface. Pretty Cool ifin you ask me.
I found it most helpful to use the slider trim lever on the radio to dial in periscope depth setting. The indents on the joystick are sometimes too course and you have trouble finding the sweet spot.
Another thing that I noticed was the tendency of the sub to broach when you turn to starboard, but the tendency to submerge somewhat deeper as you turn to port.

[KevinMc]

I usually scoff at folks who propose putting high-end servos in (slow) subs, but in your case you might benefit from high-speed cordless servos to help keep up with the quick reaction of your boat. By the way, I say cordless because they're better at quickly start/stop/reversing their direction than a standard cored servo. Digital may or may not help, but test-driving a high-speed cordless would make for an interesting experiment.

[greenman407]

There just the standard Minis that came with the original radio, a Hitec 6.

[KevinMc]

After careful observation I can tell you that some of the vibrations that are upsetting the ADF2 are caused by the propellers being out of balance. Depending on the speed at which they are turning, has a direct bearing on the severity of the planes jittering. At some speeds, you have no oscillations at all. At others you have an unacceptable amount of plane movement. From what I can observe, being in the water doesnt seem to reduce the problem.

Yup, that's an unfortunate side effect of striving for minimum delay in the ADF2...
A little background on this - when I was originally designing the ADF I wanted to minimize the delay from sensing pitch change to commanding a response, but this comes at the cost of the device being more sensitive to vibration. (Put another way, you can average out the vibes over several servo frames, but then the pitch controller behaves more sluggishly to angle changes.) The payoff though is that you can use a much higher sensitivity setting and still keep things under control than what you would be able to if you had a slower controller, and prop vibes can be dealt with.

Just out of question, what kind of servos are you using for your diveplanes in this boat? Are they coreless?

[He Who Shall Not Be Named]

It's a rocket with the two propellers! Not many boats permit we American's to feel Like a German at the sticks. Those guys are crazy!

[greenman407]

Ofcourse, the dangers of driving a sub this fast are very real. Because of the vibration/pitch control problem, you are walking a tightrope between control and out of control. If it were to go out of control, ie: dive, it could clonk itself into the bottom and knock loose the top half of the submarine with its attached floatation foam. At that point, it may not be able to surface because of the loss of floatation foam. So, I watch her very carefully. Any signs of her "disappearing" and its "All Astern Emergency"! Blow all tanks"!!
Of course its not always driven wide open.

[greenman407]

A few other thoughts on this problem. After careful observation I can tell you that some of the vibrations that are upsetting the ADF2 are caused by the propellers being out of balance. Depending on the speed at which they are turning, has a direct bearing on the severity of the planes jittering. At some speeds, you have no oscillations at all. At others you have an unacceptable amount of plane movement. From what I can observe, being in the water doesnt seem to reduce the problem.
Apparently however, we reach a compromise when the ADF2 is set for sensitivity setting 2.

[greenman407]

Ill have to work on getting up some video.He's on his favorite