Got another hair brained scheme in mind!I want to build an RC plane rescue boat this winter, but I was thinking I could have some fun with some parts and components that I've got already. Something cheap and made from junk and dollar store stuff, innovation and fun is the game, the greater purpose is to gain experience on the water and configure the control system which with the exception of the computer and GPS will be the same as on the RC rescue boat. Here I want to play with materials and dynamic forces, mount the runcam 2 and play it back at slow mo to look for flexing and other issues, gain experience with the components and configuring the transmitter.
I'm settling on a four 2L pop bottle catamaran pontoon design with a hardwood ($ store garden stake frame) using coroplast and a tupperware container as a structure and diagonally braced' It will be an air boat powered by 2 electric motors and props with a couple of pounds of thrust. For pusher props it is easy measure this using a digital scale, for tractors it involves a bit of fucking around. It doesn't matter much though cause everything is tested against reality in the end, Likewise I don't need to do buoyancy calculations either, with 8 liters of air volume supporting a kilogram of weight, I expect she will float real high on the bottles at 8:1!
I'll make retaining notches in the wood frame and strap the 2 liter bottles to the frame using 2 long heavy nylon wire ties and perhaps use some adhesive too. The raised control and propulsion system platform will be at the center of buoyancy, high enough to keep the spray off the motors, but keep the center of gravity low by recessing the tupperware container in the platform. I also have some cheap 3.3 volt LED tape that can be cut into 3 LED sections I could put a 6" self adhesive tape stips of bright LEDs inside each green plastic 7up bottle and I have salvaged waterproof bulkhead connectors for the bottle caps too! I also have several 30 watt very bright COBs kicking around with matching 12v DC drivers that should run off a 3S or even 4S Lipo.
I figure she should go like snot, can be easily FPV ed and should be like one of those bugs that walks on water without breaking the surface tension. Gonna buy some more 90CM hardwood garden stakes for the frame and long heavy wire ties at the dollar store. The frame will be wood glued and held with machine screws and washers and also diagonally wrapped in 2 wire ties for emergency backup at critical joints and to get the wreck ashore! Even a light buoyant structure has a lot of dynamic forces on it if yer skimming the waves tops at 30 or 40 miles an hour, there's a lot of pounding and vibration. Ya get serious when ya go to sea, if don't wanna swim fur the fucking thing!
Here is what I've got including a couple more bottles, I need a couple more packs of hardwood stakes, some large wireties a tupperware container and other assorted shit and I'm good to go, a small can of polyethylene varnish should protect the frame good enough. This is not something that will be around for a long time, just extending the life and utility of some junk and having fun with a cheapo short term project to try out some stuff.
The genesis of "The Junk Strapped Boat"! Strapped on junk for pontoons with wire ties and made from shit laying around, the name is appropriate.
Note my four beauties in the backyard under the pines, legal to grow 4 here and I do.
One thing I might try to do is vary the thrust pitch angle of the two propulsion units by 10 degrees from horizontal to pitched up 10 degrees. I only have 9 gram 90 degree servos but could use 2 for 18 grams total I could leverage the 90 degrees to 10 degrees gaining a 9: 1 ratio, or 18 gm x 9= 162 gm of rotational force on the shaft rotating it approx 10 degrees. However I will be directing a kilogram of thrust by rotating the shaft and the motor and thus thrust line will be centered on the shaft in balance with the load minimizing the force required. I can rig an experiment rotating one motor/prop with a levered servo under full thrust though and see how it goes at 9:1, I'll be using tractor propulsion for the props. If I can angle the pitch of the thrust upward slightly, the front pontoons should rise up slightly with an improved angle of attack perhaps and make it skim the water better. Dollar store tomorrow with a small list I think and start constructing the frame, no need for plans for a one off like this, nothing too complicated and no need to communicate the design, things are pretty obvious, it's built from what is at hand or cheaply acquired. If someone wanted to build one they can just look at the pics and description and use what materials they had on hand.