German Type 212

[oztruck]

I am happy with the way the little girl runs, both on the surface and submerged.

The video was taken with my phone in one hand and the TX in the other. (driving with just one thumb) is not easy.

The cavitation only happens when the boat is running at over 60 knots (SCALE). I guess the 1/1 would do the same if it could.

When not videoing and have full control of all the sticks it drives like a well built German Sports Car. Very quick to get up to speed and just as quick to stop.

UP to and a fair bit above scale speed it will do anything you ask it to do, and do it without hesitation, but when you put the pedal to the metal it turns into a rocket and it is usually about a 1/2 a second quicker than my reflexes.

I am going to have to catch up with some of my "Flying type buddies" to see if there is an adjustable mixer for the X tail that they can recommend that will help an old bloke like me get the maximum out of her.


Cheers Chris

[Subculture]

There's a programmable v-tail mixer available at this link-

http://www.robotcombat.com/store_rc_accessories.html

If you have a computer set, could you not just dial in a bit of exponential if you find the boat a bit twitchy?

[He Who Shall Not Be Named]

I share Chris' experience. The SD I made for this boat is way, way too much power to the shaft.

And, Andy, thanks so much for that link -- a programmable mixer (or transmitter, as you suggest) is required to dumb-down control response at the higher throttle settings.

However, what we really need is a mixer that sees throttle settings; a mixer that will reduce control surface throws with increase in ahead throttle commands. I guess the best way to achieve this is at the transmitter (dumb, four-channel boxes need not apply here).

David

[Subculture]

The very high end transmitters with freely programmable mixers could mix throttle to rudder/hydroplane response, but low to mid end computer TX's (which most of us run, lets be honest) won't have that luxury. The operator could flick in rate switches if the TX has them fitted, but it's something else to think about when sailing. It's certainly within the capabilities of a PIC microcontroller to take a sniff at where the throttle is, and adjust control throws accordingly, but I don't know of any commercial solutions.

[roedj]

Just a thought...

Would there be any advantage to independent control of the four control surfaces in an X-tail?

I realize that it would require four separate servos and a fairly sophisticated mixer to make this work but what if - just what if...
There were four servos and an ADF2 mounted transversely as well as one mounted along the long axis each feeding the mixer so that maybe two of the control surfaces would be for turning and the other two to counter the roll. I haven't really thought this completely through but maybe if this were the case the four control surfaces would be fighting one another.

I am not a 1:1 scale submarine designer (obviously) but if I were, I'd probably give some serious consideration to doing this with any X-tail sub.

Or am I way, way over thinking this?

Dan

[Subculture]

I've seen some of the German modellers use independent servos for each control surface. If you look at Norbert Bruggens dolphin model he uses twin levellers on that, mounted at opposing angles with independant control of the rear vanes (flippers?) to enable the boat to counter torque roll. He has also done the same on his Deepflight Aviator model.

[MFR1964]

I agree with the guys that the trottle has to be the guide on how much deflection the rudder will get , the faster lesser deflection is needed, found that out with running the V80 at high speed.
What i did as a premature solution,decreased the senceability of the level controller, it sounds strange but less is better, running at high speed with setting at max will give you dolphin beheavior, setting her up at the lower setting will lengthing the dolphin wave movement.
Next thing i do with high speed runs, i only use the trimtabs, don't use the stick, i know from the guys which run the X tail Walrus scale 1:1 they only use a max deflection of two degrees at the rudders.
What we are trying to do is to over correct the rudder steering, the level keeper can handle the job but the high setting is way to nervous and will give the opposit result.
Using four servo's won't solve the problem of the longitutal stability, you still have to counteract the wave motion of the boat, other thing that is important, is the neutral position of the boat submerged, she has to be perfect level to give a good startingpoint, all factors together should give a pretty stabile boat at high speeds.

[oztruck]

Thanks for all the helpful advice, my first action will be to check what setting I have the level controller on then look into slowing the trim control as the speed increases. The 4 servo system is not an option in this boat, no extra room.

[MFR1964]

There is one trick more, if you can put a little piece of foam inside the top of your conningtower she will pivot around that point at running underwater, did the same trick at the V80, this made the wave motion less and gave me more stability.