I'm mostly interested in RC Air, but this in particular intrests me. It's sort of a conflict between you and nature and failure means you lose your investment.

I like to draw and design things to address a particular problem. I was thinking it would be cool to have a sub that isn't so much radio controlled, but instead dives to the bottom of whatever body of water you put it in. When it touches bottom it releases a trip and dumps part of its ballast, just enough to make it rise slowly. Instruments on board will have recorded the maximum depth (pressure) and the excitement will be to obtain a map of a lake with depth indicated, and to release your vehicle in gradually deeper parts to see if it can take the stress. If it comes back to the top, Success! If after a min or two bubbles rise to the surface.. you should have built it better.

I drew these things as my first idea of how to make it release when it touches bottom. Also I was thinking of a way to recover it even if it does collapse. For example a small battery holds a float to the body of the vehicle with an electro magnet either directly or by some sort of relay. The vehicle goes too deep and implodes, floods and stays on the bottom. After time, the battery runs down and releases the float which is attached to a spool of strong thread, like 20 pound test woven fishing line. The float rises, unspooling the thread and you just drive your boat over to the float and haul whats left of your vehicle up.

Any thoughts?

[link=http://i5.photobucket.com/albums/y177/dustyatticx/Vehicle.jpg]Capsule[/link]
[link=http://i5.photobucket.com/albums/y177/dustyatticx/Ballastdump.jpg]Dump[/link]

What a nice idea!!

You're right about it not being much radio controlled but a device like this could grow up the envy of any sub-fanatic! You can perhaps use a timer to calculate the time it takes to reach the bottom (and going up!) couple that by the speed it takes for the boat to reach the bottom and you'll probably get an accurate distance calculation. I wouldn't call this much of a "boat" but perhaps rather a "capsule". This could be really useful for any sub modeler who wants to run their boat in a pond or a lake, by dropping this to the lake's bottom, you could get the approximate depth of the lake in advance, before running your boat just in case something happens.

Be sure to let us know your progess if you plan on continuing on on this idea.

P.S: I don't quite understand your last drawing, is it the trigger that will activate the ballast release mechanism?

Looks very promising!

Thats correct captain. The trigger is slid in (towards the middle of the capsule) within its guides on the side of the body. Then the piston in the dump chamber is compressed until the piston rod extends out of the other side of the body, through the large eye in the trigger. The slot is aligned with the groove on the piston rod and then the rod is slid out capturing the piston in the narrow slot.

When the vehicle touches bottom, the weight of the whole thing continues to press downwards, sliding the trigger in until the hole is yeah.. you get the picture. It springs out and dumps the ballast you stuck in the dump chamber and up it goes.

With the dump chamber empty it should only be slightly buoyant so as to not rise too fast. It wouldn't be good if all was quiet and all the sudden it shoots 6 feet out of the water beside your boat. If it becomes a problem, I suppose a skirt of some kind could be added to make lots of drag as it rises.

What would the dumpload be? Well environmentalists would be upset if it was some kind of trash like beer cans filled with cement or lead. I think a good disposable ballast would be steel shavings from a machine shop, packed in a cotton cloth bag, or old 100% cotton T-shirt. All biodegradable right?

Nice plan. Another question, how much do you think it will cost to build such a device? I mean, there's no RC-radio equipment involed so that'll probably spared a few hundred dollars or so. Another thing, perphas a PVC tube could be used for the electronics (instruments), and the wtaertight part of the capsule? When you're talking about going down to the bottom of a lake or pond, you're talking water pressure, so a PVC tube might be able to resist such pressure if the thickness of the tube walls is chosen correctly. You'd also have to make sure that the capsule lands vertically on its trigger.

How about using earth or soil as the solid ballast to be dumped? You could usually find some near the pond or lakeside, and it'll be pretty environment-friendly.

I'm thinking there is a way to improve the dump section. In reality I think it will take some skillful grinding, drilling and honing to make the trigger operate smoothly. It's going to weigh very little underwater since its just slightly negative, so if the trigger isn't just right its going to the bottom and waiting there for eternity. A better trigger needs to be thought up that takes little effort to hold a significant spring pressure. Think about a mousetrap. Enough force to kill a mouse, but triggered with a nibble. Also it would be nice if the rod goes up through the center instead of the side. Besides looking better, as it rises the triggerplate will act like fins in the rear or a weathervane and hopefully make it rise as straight as possible. If it's out to the side it might ascend with a crazy spiral.

With the air chamber on one end and the permanent ballast on the other end, I think it should stay reasonably straight up and down. The air chamber could be permanently sealed. Before you glue the end cap on though, what if you drill a nice smooth round hole and pull an automotive (or semi-truck) valve stem through it. Then, you could pressurize the chamber. Schedule 40 PVC holds what, 300psi? Thats about 655feet! And even at that depth, the pressure is only equalized, you could dive much deeper still! If you went that route though, pressurization would be required if you went to any depth or else the valve stem would be sucked (or blown or whatever) inside the chamber. Here's a waterdepth/pressure calculator for salt water:

[link=http://www.gazza.co.nz/waterpressure.html]Pressure Calc.[/link]

I was thinking of a way to record the maximum depth. How about this:

[link=http://i5.photobucket.com/albums/y177/dustyatticx/Depthrecorder.jpg]Depth Recorder[/link]

Its just a pressure gauge from 0-50 psi or whatever range you plan on diving in. The face is removed and attached to the needle is an extension arm which has a felt tip marker on the tip. The rear of the gauge has cardboard attached. As the gauge moves, its marks the cardboard. In the pic that you see, you have just opened the instrument package and see that the capsule has decended to XXX depth by the red line.

The cost should be minimal. Whats a joint of PVC cost? Primer and glue, some fittings. Some aluminum rods and stuff. Any local hardware store should have everything needed. If I come up with a trigger that I am satisfied with I might make one of these things to see what happens. I just need someone with a boat to go to the lake with to test it.

You would be far better having a compressed air tank that pushes an amount of water out of balast tanks for the raising. Simple I would say but you could make it simpler by having a compessed spring to push the water out instead. Also temperator effects pressure, and it's not a negligable effect so you will have to record that also. Another thing to remeber is that the bottom of the craft will have to be the heaviest or it will roll over and your bottom sensing switch will never get pressed.