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triPod RC

I designed and made this RC model of the triPod craft to test the idea and get a handle on the best shape for the pods. I was able to get a rough idea of the craft's weight by setting the material properties of the model and calculating the theoretical waterline.

Main build material was CNC cut birch plywood with epoxy resin to strengthen. I made up some steel parts on the lathe and hand cut/folded steel plates for steering components. Couple that with some old RC components and parts of an old cordless drill, and a functioning prototype got made. I was too impatient to test to make the proper covers for the electrics and pods, so I improvised!

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Unfortunately the videos above are the only existing footage of the only test. The camera was recording when the cameraman thought it wasn't, resulting in the classic of not recording during the times it was meant to!

The test was short, due to not being patient enough to make the cowlings and being concerned about the electronics getting wet. However, I did glean enough to advise the next iteration of the model.

Features of note were:
1) The craft was stable (see the little wiggle side to side at the beginning of the left video), and cornered flat. This was considered when setting the angle of the front two rudders/keels, aiming to add lifting force to the outer pod, and downward force of the inner when turning. My hope was for this to counter the natural lean of the craft towards the outside of the turn.

2) The craft sat too low in the water, having ended up slightly heavier than expected.

3) The craft was not able to rise up onto the plane to test the high speed characteristics. I believe this was down to 3 reasons in various degrees:
  a) Too little power
  b) Waterline too high
  c) The shapes of the pods not optimal

Build

Below is a gallery of the build process.

Re-Design

The test made me reconsider the shape of the pods, I incorporated a flatter and wider shape to increase uplift on to the plane, and considering the added volume of the pods, I also added a step on the planing surface of the hull, inline with the steering axis. The step creates a surface of bubbles to reduce drag. With enough thrust, I would be optimistic that this version would lift onto the plane, and perform well at higher speeds. Maybe one day I'll make this one!

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