Build log #2
                                  by Ralph --- SSBN 598 
A few modifications.
I had a lot of issues with the main motor.
I used the motor programing to reduce the RPMs to 20%.
I used the Tx menu to program the motor to 20%.
This did reduce the RPM but not enough.
I tried reducing the Tx down to 10% and this resulted in a sever cogging of the motor.
Not acceptable.
It was suggested that I try the Engel's 300 with the SubCommander ESC.
Both of these items are purpose made for submarines.
I removed the Rock crawler motor and Esc and installed the Engel's parts.
What a difference! ! !
The Engels is setup to run on 12v and my system is 7.2v.
On the high side, I have far more RPM than I will ever want to use.
I set the Tx down to 50% and this is so much better.

On the low side.
OMG. I can slow the propeller down to where I can count the RPMs as it is running.
No cogging at all.
I did a fast trim on the boat and took it to the pond.
The boat run so much better.
So much more control over the speed.
Only issue was my hurry to trim, I made the worst mistake.
I balanced the boat opposite of what I knew to be the way to do it.
I added more ballast to the stern to compensate for the smaller motor and ESC.
About half the weight and volume.
This caused the lost of weight and the increase of air volume in the cylinder.
The mistake was, I put the new ballast weight near the stern to replace the weight lost in the stern.

What this did was move the surface center of gravity forward and the submerged center of gravity rearward. 
The boat ran really well as long as I kept in mind that the trim was not correct.
In forward, I could control the pitch with the stern planes and the depth with the sail planes.

Where it got ugly was in reverse.
The pitch controller tried to correct the pitch but the controller is set for forward motion and not reverse.
The rear planes activated to bring the stern up in forward motion but the boat was going backwards so the stern dove to the point the boat was bow straight up.

This is something that causes extreme concern. (panic)
First thing I did as this happened very quickly was turn off the Tx.
This shuts off the main motor and centers all control surfaces.
And the biggie, this turns on the ballast pump to empty the ballast tank.
The boat surfaced and I was able to drive the boat back shore.
Took it out of the water and brought it home to be retrimmed correctly.
Got side tracked by an Akula II assembly.
That is complete and I can get back to the Skipjack modifications.
Opened up the Skipjack this morning.
Pulled the electronics tray out and put it on the work bench.

Before I start any trimming, I plane to make some changes to the electronics tray.

The new motor/ESC combination is much smaller than the original items.
The motor is shorter in length by 1.75".

Took some measurements and cut the electronics tray under the motor location.
Currently waiting for plastic cement to cure so I can do the hole drilling.
The long tray mounts to the motor frame with 2 small bolts.
This will allow me to move the ballast tank back 1.5" from the bow.
This will position the ballast tank under the rear of the sail.

The battery pack will remain in the bow.

I will remove the lead ballast blocks and start over with trimming.