Albacore continued

[Slats]

Can do on the 3.5 SD's. But not likely on the 2.5 and 2 SD's as the larger diameter conduit tubes gets in the way of the gas and/or safety float-valve.

David

Understand David
but can you do it on the 3" as well?

J

[greenman407]

Today we got in a little run time with her. Then surfaced a re-occurring problem. The dive planes are jittering too much again. You could probably get away with it on a standard cruciform rudder sternplane arrangment, but not with an x tail. Its just too sensitive. If you operate at slow speed with her you have no problems. As you increase speeds she starts the "Up and Down" movements again. Whats interesting about this is, a couple of weeks ago she went full speed with no problems. Now we are back to jittering again. As you know I detected this early on and for that reason I tried multiple ADF2s as well as a Thor pitch control. But to no avail. So I put it up front with the Battery. I guess its picking up on vibrations again. I think Ill try a layer of thin bubble wrap between the battery and the shelf that the ADF2 is mounted on. I have to get this problem solved once and for all. There is no need to buy new more powerful motors If I cant use them.

[greenman407]

Here is a short video of her today. At about halfway thru the video you can get a glimpse of her below the water speeding along at about 3/4 throttle.http://www.youtube.com/watch?v=FI5dj...ature=youtu.be

[MFR1964]

Mark,

I've encountered the same issue with the 212, but allready had from the start the ADF2 inside the front compartment, on the bench it will pick up the vibrations as expected, normally it would be less when in the water.
Insulating the ADF with some bubble rap could be a solution, however it maybe catches up a oscillating vibration from your gears running both shafts, did the sound from your gears alter from your previous runs?
For me the only solution was, reduction of the topspeed by 60%, which gives me a stable run at the scopes, higher speeds means more yanking at the sticks by hand, it's possible, but the easy ride is gone.

Manfred.

[greenman407]

Manfred, thanks for the feedback. I havent noticed any change in gear noise. Inside the front compartment, on the back of the ballast bulkhead, there is a screw in the center of the bulkhead that is touching the panel that the pitch control is mounted to. Perhaps its transferring some vibrations. Ill probably take the screw out and seal the hole up and then try to insulate that panel from everything else.

[MFR1964]

Mark,

You can also try to make some soft rubber insulation between the hull and your SD, i removed the dogbone and replaced it by a silicone hose to couple the SD to the shaft, lesser noise and offcourse lesser vibrations.


Manfred.

[greenman407]

I just tried bubble wrapping the shelf but by the time you put the endcap back on you have the battery wires jammed against the shelf, negating your attempt at isolation. I wonder if there is an APC out there that is not so affected by vibration?

[greenman407]

Thanks Manfred, perhaps. I think that the props are not balanced, setting up a vibration. At certain rpms there is barely any movement of the planes at all, and at other rpms,WILD GYRATIONS! This fix will probably envolve a lot of little things together.

[greenman407]

NEWS FLASH!! NEWS FLASH! I feel so much better............................................ .................................................. .......................OH! Why do I feel so much better? I checked the sensitivity setting on the ADF2 and found that ,somehow it had , apparently reset itself to setting (3) three, for the most sensitive. Preliminary tests on my work bench show that if I back it down to setting one, it doesnt pick up any vibrations. I posted a note on KMC designs section and see what Kevins take is on this. Do you have to reset the sensitivity setting every time you power it up? was my query. Manfred , you might check your setting on your ADF2. If you have lost your instructions, I can post it here tomorrow.

[greenman407]

The problem with soft rubber to isolate the subdriver from the hull is that after you rubber band your subdriver down so that it wont move, your soft rubber has collapsed into hard rubber. Unless I devise a way to hold it in place by other means. (Evil laugh) as he slowly fades away.

[MFR1964]

Mark,

Remark noticed about the ADF, i'll check her up tomorrow, and yes i still have the instructions, i use a different system to clamp the SD inside the 212, but your remark about the soft rubber is right, if compressed too much the effect will be gone.

Manfred.

[He Who Shall Not Be Named]

Have you changed the 'sensitivity' of your ADF2 yet, Mark?


Every item that has the property of mass has a natural resonate frequency and harmonics of that about which that mass readily oscillates if excited. A system of different masses rigidly held together (no such thing, I know ... humor me, damit!) has a specific natural frequency unique to that system. Look on your ALBACORE as such a system. You've got a regenerative system vibration feeding the sensor of the ADF2. You're in a feed-back loop, pal!


We don't kneed to know what the frequency is... anyway, we don't know how to measure it (well, maybe Andy and Norbert do). But, we do know that by changing the mechanics of the system: rigidity-elasticity of the system (your bubble-wrap for example); distance of the sensor from the center of rotation (jamming the poor ADF2 into the bow compartment); circuit response time, or circuit response amplitude (sensitivity setting), we can eventually create the environment where the sensor response to system vibration is degenerative rather than regenerative. The objective is to get away from system induced oscillations. Change one variable at a time and test, observe, and analise. Do that till the boat stops chasing its tail at all throttle positions. (Easily said!)


You are now at that happy-space where all you need suffer is pilot induced oscillations.

David

[greenman407]

Thanks Dave. I think you missed my earlier post about discovering that the ADF2 had, by itself, changed its sensitivity setting. I turned it back down to where it was before and the flutter is gone. Got to get it back into the water to make sure that was it. Thanks.

[greenman407]

OK, so to recap what has transpired. In order to get the Pitch control to work, it became necessary to install it in the forward dry space. This because of the vibrations being picked up in the rear compartment. After installation in the forward compartment , the Subdriver and APC worked well, sitting on the bench. After installation of the subdriver into the submarine, new vibrations were entered into the equation. Two propellers and my home made twin shaft produced vibrations that the Pitch controller picked up. The solution to this was to reduce the sensitivity of the pitch control, in this case , the ADF2. Since its maiden voyage was successful but the second voyage was not, it seems most likely that this particular ADF2 changes sensitivity settings on its own. Therefore, as part of the on site, pre sail checklist, a new req. for this sub is to check and reset that setting. No Rocket science here. Tuesday, January 1st will be my next opportunity to test it and confirm. I am also hoping to get some better video of her that day.

[He Who Shall Not Be Named]

Good report, Mark. Good luck.

This damned flu has me out of the shop for nearly a week now!

David