Designing a Biodegradable Floating Target for Aerial Small Arms Training

[FMAG]

Looking to design a floating silhouette for aerial small arms training. There don't seem to be any companies that provide such a product so we have to design our own. A few of our ventures have failed and looking for assistance from those far smarter than I.

Stipulations:
We use 36" high, wax board silhouette.
Must be able to be dropped from a helicopter from ~15' and right itself and stay intact.
Must be biodegradeable over time, i.e. no plastics.
The target should be able to withstand at least 3' seas (~5-10 knots of wind).
The time period that targer will be used is about an hour, so if it degrades soon after that, that's acceptable.
Design can be anything.

Problems to date is getting the target to either stay upright or stand high enough in the water.

At present, we have a wax board target screwed along the bottom edge to a 1x1x30" then another 1x1x30" forward to back, forming a cross. Pressure treated wood, with 4-5 oz of weight hanging 10" below center as a balance.. With this design, almost half the target is submerged. Target needs to float fully out of the water.

Any further ideas on this or completely differnet design would be appreciated.

dk

 

[FredGarvin]

A couple of quesions:
- Do you have an approximate weight of the 36" target itself?
- Is there a requirement for how close to the water the target must be (can the target stand proud of the base at all)?

 

[venuesystem]

buoyancy... maybe need to trap enough air at the base of the target to offset the force. You could increase the size of the "cross" and make crossed pontoons, maybe from 8-12" sonotube, it should degrade (BTW are you in saltwater?). Paper mache (sp?) the ends closed. To join the tubes in the center, each tube is cut halfway thru creating a lap joint. Join the same as the ends. You could bolt the target to the tube before sealing it up.

 

[venuesystem]

buoyancy... maybe need to trap enough air at the base of the target to offset the force. You could increase the size of the "cross" and make crossed pontoons, maybe from 8-12" sonotube, it should degrade (BTW are you in saltwater?). Paper mache (sp?) the ends closed. To join the tubes in the center, each tube is cut halfway thru creating a lap joint. Join the same as the ends. You could bolt the target to the tube before sealing it up.

Or just make two pontoons parallel if you want to take the fun out of it...!

 

[Danger]

If this was presented to me as a personal task, I would attack it thusly:

As a construction material, I would use the same thing that I sometimes substitute for latex in prosthetic make-up, which is gelatin mixed with about 10% of the water that would normally be used for Jell-O. It hardens to about the consistency of a pencil eraser, but will eventually dissolve or even be eaten by sea creatures. I would shape it like a wide bowl, with the target itself like a sail on a mast (I'd use a wooden dowel for the mast). For ballast, I would have a 'keel' moulded in the same piece as the bowl, but filled with sand. When the gelatin dissolves, the sand will just join all of the rest on the sea floor.