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Originally Posted by mbauer
That sub is totally awesome. Great photos of it diving. Really like the prop wash when near the surface.
Just watched the video. It really moves out fast!
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Thanks!
Cavitation shows inefficiency but that's only when it is close to surface and seems to draw in a bit of air. Reduces and becomes zero as it gains depth.
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What did you rig up for the prop?
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Took some pics just now to answer that and probable other questions.
Prop was from a Traxxis twin motor speedboat of some sort.
2 different props were available in both left and right rotation.
This is, I think, the greater pitch prop.
Prop shaft and hook is music wire with telescoping brass and/or copper tube over it to fit shaft tunnel in prop.
Tubes were notched at far en and an L in wire soldered in to notch, so as to ensure torque transmission, i.e. non-slippage of wire inside tube "sandwich".
Because prop is pushing versus pulling, thrust bearing from some Horizon Hobby mini-truck is used. It's never been oiled that I can recall.
Fitting in stern and propellor thrust button come from some full-body styrofoam airplanes by MRC that I'd acquired who knows when.
Bow and stern planes are sheet brass soldered to brass rod and tube.
Go through brass tube across hull.
Made use of that annoying barcode sticker K&S started putting on its individual tubes in the counter display of its tubes and rods by using its adhesive residue to allow friction setting of the planes.
Shaft is solid.
One plane was soldered to shaft.
Shaft was inserted through tube in hull, then sub wrapped in wet washcloths and far side plane quickly soldered with butane torch.
Stern planes were eventually "filled out" with balsa underneath because a little additional flotation was needed aft for trim to look right to me.
Bow planes were left 'unfilled' on bottom because they sometimes get bent when sub impacts pool side if I've misjudged pool current or circle radius when running in circle.
Rudders definitely have "Rudder Authority" They are styrene sheets super glued to brass shaft, one sheet each side of shaft.
Prior to gluing each sheet was bent a bit to give shape.
Gap between sheets was gradually filled with that baking soda then super thin super glue thing to give solidity.
Bellcranks for rudderes were supposed to eventually be cut from brass sheet and soldered to Carl Goldberg model plane wheel collars but I made some temporary sheet styrene bellcranks for ballasting tests and superglued them to wheel collars with cheap super glue figuring they'd be easy to pop off when I got ready to solder on the final brass cranks.
... that was in 2005 ...
styrene cranks are still there, because why not, they're working!
Book directions showed strip of solder bolted on for sub keel; I cut slot in bottom plan and used K&S brass strip inset. It might or might not have a couple retaining tabs soldered to its top edge, I don't remember.
Handrails are Athearn 'blue box' HO scale locomotive stanchions and beading wire.
Periscopes are K&S tubing, don't remember if brass or copper, they are open and go through to hull interior, which is free flooding.
They bubble as sub goes under
Ballasting of hull:
There is a LOT of steel shot glued in to recesses cut in hull bottom and in to box block.
After hull was assembled entire exterior of hull was soaked with super thin super glue to harden the balsa.
Hull interior is open and free flooding, it was treated same way.
It seems pool chlorine has seriously negative effects on rubber motor longevity, be prepared to get only 2 or 3 runs sometimes from motor loops.
Yes, I do use glycerin lube while prepping rubber for installation.
2 loops of FAI 3/16 tan sport rubber is enough to get that speed and power seen in video. Puts out plenty of torque to get that prop to get a solid bite of the water. Enough to cause hull to torque roll a bit at beginning of run.
Shoelace in photo below is to keep prop from falling out and becoming lost/damaged while sub is on display.
And it winds and turns prop just like rubberband! :D
