The D&E German 212

[Kazzer]

I received my 212 today from The Wiz, all fired up and ready to go. WOW!!!!!!! I simply cannot get over the detail on this boat. Apparently Brians Starks did all the detail work on the master, and it is simply stunning.

I fitted the prop and shaft, but having few tools here in Florida (yes I'm in Naples for a few days - Spring break!) I had to run to the local hobby store to get a few small tools.

Anyhow, this evening, I put the boat in the water and ran it for about 15 minutes. She turns on a dime, and is very responsive and FAST! I love it!

After a while, she wasn't running so well, so I pulled her out of the pool and took her indoors to find out what was wrong. I thought the battery was low, but it wasn't that. The set (grub) screw in the prop had worked loose and the prop was spinning on the shaft. Obviously, I had been a little too gentle tightening it up.

So, tomorrow, I jump into the pool with my Sony Sport Pack camera to shoot some video.

I won't be able to upload it until the weekend as I forgot to bring the correct cable. So tune in then - you are going to be IMPRESSED with this model.

[Outrider]

Do you have any other boats along with you so you could provide some comparison? The Wiz says that the little Skipjack may be faster and may perform better. (Probably a power to weight ratio advantage.) That said, the 1:96 Type 212 has a certain heft to it, and, because it's bigger, it may be easier to control.

[Kazzer]

Do you have any other boats along with you so you could provide some comparison? The Wiz says that the little Skipjack may be faster and may perform better. (Probably a power to weight ratio advantage.) That said, the 1:96 Type 212 has a certain heft to it, and, because it's bigger, it may be easier to control.

I think David was referring to the D&E Skipjack, not the tiny Revell model. Hopefully, David has the rework of his tools to get this boat back on the market. I have one and it is a really slick model.

In comparison, the D&E 212 is pretty hot, but not quite as fast or maneuverable as the Skipjack. But don't take my word for it, I'm no expert.

I will have some good footage of the 212 over the weekend, which I'll upload to Youtube. You'll note that the 212 tends to porpoise at certain speeds, and The Wizard tells me this is due to the X Tail and the ADF. KMC Designs has an X Tail mixer gadget in the works, I think.

[He Who Shall Not Be Named]

I think David was referring to the D&E Skipjack, not the tiny Revell model. Hopefully, David has the rework of his tools to get this boat back on the market. I have one and it is a really slick model.

In comparison, the D&E 212 is pretty hot, but not quite as fast or maneuverable as the Skipjack. But don't take my word for it, I'm no expert.

I will have some good footage of the 212 over the weekend, which I'll upload to Youtube. You'll note that the 212 tends to porpoise at certain speeds, and The Wizard tells me this is due to the X Tail and the ADF. KMC Designs has an X Tail mixer gadget in the works, I think.

The 1/96 X-tailed Type-212 turns much better than the 1/96 SKIPJACK... and the SKIPJACK is no slouch in the maneuvering department!

OK, about the X-tail porpoising and its likely cause. But, first, a few words about how the X-tail arranged control surfaces work.

X-tail control surfaces are actuated in one of two ways:

The basic method, the one most of us employ with our r/c submarine models, is to use only two servos, each servo controlling one set of control surfaces sharing a common operating shaft. Each set of control surfaces is disposed 45-degrees from the vertical and horizontal datum planes. The arrangement can produce pitch and yaw forces in any magnitude from zero to whatever can be produced as a consequence of the boats speed, control surface area, and degree of deflection. This scheme, however, can not induce any rolling force.

The more sophisticated scheme employs four servos, one for each specific control surface. This arrangement works as the first, but because each control surface is operated by a dedicated servo, they can be displaced to produce a rolling force. The added complexity provides for much better ship control in high speed, tight turns. And, coupled with a two-axis stabilization device coded with the appropriate logarithm, the arrangement will do a better job of damping out oscillations than the simplified arrangement most of us employ.

Disregarding roll control for the moment, both schemes provide for two sets of surfaces that together will produce the required pitch and yaw forces needed to effect positive ship control. If both sets of control surfaces rotate in the same direction, the same amount, the vector sum of the two forces by the four control surfaces (the pitch force elements cancel out in this example) presents to the boat a pure yawing (turning) force.
On a paired set of control surfaces (all four control surfaces at work), though the lower surface may be producing a downward force, its counterpart above, will be producing an equal upward force, therefore the only net force presented at the boats center of rotation is a yawing force (the direction of the yawing force dependent on the direction of the control surfaces deflection from center).

Keep in mind that since the control surfaces are oblique from the vertical and horizontal datum planes they individually produce both a vertical and horizontal force, each and every time they are positioned anywhere left or right of centerline. In the above example, the vertical force of the two opposed control surfaces (each pair sharing the same operating shaft) is negated by the other paired control surfaces. The resultant force applied to the submarine is a yaw force. the pitching forces are equally opposed and canceled.

Rotate the two sets of control surfaces in opposite directions the same amount and you get a pitching force -- all yawing force generated by the control surfaces are canceled out.

Vary the degree of relative motion between the two sets of control surfaces and you get both yaw and pitch forces applied and the boat rotates about its center of rotation in the appropriate direction.

So, why the porpoising? Pitch motion is more apparent to an outside observer (you, the Driver of the r/c submarine) on a submerged submarine than subtle yaw motion. Actually, the X-tail submarine will more likely be performing a cork-screw shaped motion through the water than a simple pitching sign-wave, or 'porpoising' when it gets into this self-induced, two axis oscillation.

Without accounting for the variable of speed, a given pitch and yaw vector will change in amplitude with a speed change and those forces will likely couple with the boat's natural pitch and/or yaw frequency and a regenerative link occurs, manifesting as a cork-screw and/or porpoising event.

All too often the two-axis oscillation is exacerbated by ADF/angle-keeper and your corrective actions at the transmitter ... and now things get really ugly: device and/or driver induced oscillations! Disregarding, for the moment, this out-of-phase device/operator ****-pie we've created, the oscillations induced to the boat is very much akin to the inertia-coupling that plagues high performance aircraft and missiles. We sometimes see this pitch/yaw oscillation problem on high performance submarines employing cruciform arranged stern control surfaces and stabilizers too, but not to the degree as with the X-tails.

How to fix the oscillations? Keep the speed down. And, at the transmitter, mix in throttle to temper yaw and pitch throws.

Hell! ... I don't know!

KEVIN!!!!???? help!

Learn to get in phase with your corrective inputs. That's eventually what I had to do.

Shut up and Drive!

Ever wonder why I don't fly anymore?

David,

[Outrider]

Not to contradict the Wizard's post above, I actually did ask about the little Skipjack, because David had noted how fast the little tyke ran in a pool. Interesting discussion. One of the things he talked about as a practical limit on the speed of submarines is a torque roll problem. Essentially, the amount of torque applied to the main shaft will exceed the control surfaces' ability to compensate, and the sub will roll about its longitudinal axis (centerline). (By the way, the sail is also a fixed anti-roll control surface.) One way around this is to use counter-rotating props, such as the coaxial set-ups used in torpedoes that have an abundance of torque and comparatively small control surfaces, but still go fast and maneuver well (or well enough). David wrote an article about the Albacore which mentions some of the experimentation done with a coaxial prop set-up on an experimental tear-drop hulled submarine.

An X tail mixer from KMC could be a timely addition to the Empire. Can you give us more? (Kevin seems to have done well with the ADF2, which is smaller than the ADF1.)

Looking forward to Mike's 212 videos...

[Slats]

Don't own either the Skipjack or the 212, but both look like superb investments in fun, reliability and max bang for your buck.

BTW - A couple of guys down here are interested in the Skipjack any idea on a release date as I understand it was being re-tooled?

Best
J

[KevinMc]

Hey guys,

Just so no one thinks I'm asleep at the wheel, yes I am looking in to this issue!

[He Who Shall Not Be Named]

Hey guys,

Just so no one thinks I'm asleep at the wheel, yes I am looking in to this issue!

Yah!, Yippeee!

David,