USS Alligator Bouyancy Tanks

[redboat219]

David can you enlighten us about this interesting mechanism. From what I read so far these were used to give the sub longitudinal stability while underway submerged. They were deployed and retracted using chains.

Did the tanks remained on the surface with the Alligator suspended under them or did the Alligator took them down with it?

[He Who Shall Not Be Named]

Once upon a time D&E Miniatures built special effects miniatures and sub-assemblies for the motion picture-television industry. That work, of course, came to a screeching halt with the advent of CGI.

Our most involved TV project was for an independent Producer who was putting together a one-hour long show for the Discovery Science Channel

(that video can be purchased here: Amazon.com: Hunt for the U.S.S. Alligator: U.S. Navy's First Sub : Discovery Communications, Inc.: Movies & TV )

The USS ALLIGATOR, America's first commissioned submarine of the United States Navy. Built during the civil was it was intended for salvage, and attack work. The effects miniatures are to 1/12th scale.

Here's some footage from the show: https://youtu.be/DMOiNqraEOA

As this vessel had no horizontal control surfaces to help maintain depth, it instead relied on hanging off of two floats -- depth control achieved by reeling in the lines between the buoys and the boat. Simple, effective, and provided an assured means of setting and staying at an assigned depth.



The Producer sent me the script with a rough storyboard of the scenes where the models would be employed. Tim Smalley built a model of the prototype, which would be used for surface shots in a local canal; and I built the 'production' version, what became the USS ALLIGATOR for all surfaced, submerged, and table-top shots.



All filming was done at the David Taylor Model Basin and locals in and around Carderock, Maryland.

Here I'm briefing the diver-camera crew and the Producer on the does-and-don't of miniature handling. Our staging area was one of the bays adjacent the big maneuvering and sea keeping (MASK) tank we used for some of the underwater shots. This one day-one of a three-day shooting schedule.



Here I'm testing the miniature to affirm that it indeed did work as designed -- hanging off the two deployed buoys at a fixed depth. This was the entrance canal to the big MASK tank.

On-set time is expensive, and the clock ticks away hunks of money by the second, so one had better be prepared when the cameras are ready to roll. They don't call me one-take-Dave for nothing! You don't stay in this game long if you keep people waiting.




And here is the miniature doing what most r/c submarines can't do: holding perfect depth while backing down! Another virtue of the design. The testing done I transferred to a workboat with my gear and the miniature and puttered into the big MASK tank for a day's shooting of the model surfaced and submerged.




Kevin Rimrodt, my partner in crime for this gig, positioned himself in the rafters and called down to me when the model got close to an obstacle or diver. It was during our lunchbreak that we found that the buoys also permitted me -- with only slight changes to speed and occasional squirt of gas or vent to the ballast tank -- to achieve reasonable depth control with the model submarine at any depth!

Kevin and I later talked it over. We figured that the deployed buoys raised the vehicles center of buoyancy so high that there then existed enough moment arm to keep the vehicle statically stable not only about the roll axis, but the pitch axis as well! Did the inventor of this submarine know that? We were not only surprised by this finding, but the PhD's who work there were also left scratching their oversized heads.



One of the two buoys is right behind the copula. These floats are released, via r/c, as I flood the miniatures ballast tank.



The second day of the shoot we went outside to the 'explosive basin' to run the model. And again, we found that the miniature could run well with the deployed buoys to any depth needed; I could ascend or rise at will with just an alteration in speed, and the occasional squirt of propel or vent of the ballast tank. This was one of those rare jobs where almost everything worked right the first time!

The diver's were real pro's, most of their work was open-ocean stuff chasing man-eating sharks around for the Discovery Channel. This was play-time for them. Once we had the day's tape in the can almost the entire production team had a swing at driving the model around the basin. A good crew!

[redboat219]

Okey, so Brutus de Villeroi really designed it to be suspended under the floats.

Let's see if I got this straight, the BT(s) partially dove the boat to a point were the bouys can then be deployed, lowering the boat further down. Depth was maintained by winching it up or down the floats, which acted something like a variable ballast tank. To surface, the boat was winched up to the float then the BTs were pumped out.

Any photos of the WTC you used, specially how you deployed/ retracted the bouys.

[He Who Shall Not Be Named]

Okey, so Brutus de Villeroi really designed it to be suspended under the floats.

Let's see if I got this straight, the BT(s) partially dove the boat to a point were the bouys can then be deployed, lowering the boat further down. Depth was maintained by winching it up or down the floats, which acted something like a variable ballast tank. To surface, the boat was winched up to the float then the BTs were pumped out.

Any photos of the WTC you used, specially how you deployed/ retracted the bouys.

When and if I find the time, I'll break the model out and take those pictures.

David