I have one of the very early Small World Models USS Bluebacks and it is one of my favorite models. I also REALLY like being able to carry it on commercial aircraft and run it in small pools thanks to its compact size.
However - I have had a recurring problem with the ballast system that I believe has been fixed in newer versions. It may have been caused by something I did when putting it together.
If the radio channel that controls the ballast vent/blow servo glitches - or I forget to turn the transmitter on first (duh!), the ballast servo cranks way around and the cam that runs over the schrader valve in the propel tank over rotates and it comes off the pin of the valve, jamming the cam all the way over and keeping it from rotating back where it belongs.
This requires taking the ballast tank apart (easily pulls apart) and with a thin knife blade, lifting the schrader pin and rotating the cam back around. Not a difficult or complicated fix at all.
Dave Manley suggested taking a heavy piece of styrene and CA-ing it to the end of the cam blocking it from rotating too far. I tried this fix and it worked for awhile but the plastic eventually bent over.
Rather than CA-ing on a new piece of plastic during a recent refit of the model, I decided to try something else.
I had used a product called Apoxie Fit-it while I was working on my H.L Hunley - using it to build up the bow to the correct shape. I found that this product is amazing. I have run the boat several times directly into rocks and cement walls of pools and it has never even chipped.
It is also sticks like a shadow. As a test, I molded a little elephant head and pressed it onto a glass beer bottle. That was four or five years ago, and I still can't pry it off the bottle or even break it off.
I molded a stop and pressed it onto the end of the ballast tank cam. I made it so when the cam rotated all the way to the end, the Fit-it stop ran up against the threaded body of the schrader valve and kept it from rotating too far.
Works like a champ! I suspect there are a few other guys who have early Bluebacks with this issue - I hope this helps!
Click below to go to the Aves Studio website - the perveyors of Fix-it.
Aves Studio Fix-it
Here is a rather fuzzy close up of the stop on the cam. Note that it is moulded so it runs up against the threaded schrader valve body.
Here is the two part product. It is available in several sizes. You take equal parts, kneed them together for about two minutes and its ready to go. Stick it on and that's it. It sets up in a couple of hours and is totally cured in 24 hours. You can smooth it with a wet finger and it cleans up with soap and water. There are epoxy products that look like this but are nowhere as good nor as strong.