stuffing box for pedal drive

I have been looking over different designs for pedal boats, i was wondering how much drag or problems stuffing boxes create. should i expect a lot of drag if it is well set up?

is there commercial stuffing boxes for small shafts, say 10-20mm?
is it easy to DIY your own?
can you get away with no drip seeing as pedal drive wont do over say 100rpm?
what are peoples experiences with this?

 

You can use a regular oil seal for that application.
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I have used common tubing compression fittings, with an O-ring inserted instead of the metal furrel to seal the shafts of a few large model boats. For example, if you have a 3/8 inch diameter shaft, buy a 3/8 inch outside diameter tube compression fitting, typically pipe threads on the other end of the fitting. Drill through the fitting a 3/8 inch bore for the shaft to pass through. Use an O-ring with 3/8 inside diameter, and approximately 1/2 outside diameter. Lubricate the O-ring with grease or Vaseline, and tighten the compression nut to retain the O-ring. There you have a stuffing box that will reasonably seal water out. A simple clamp will keep the compression nut from rotating off it's threads. Compression tube fittings are available in all USA sizes, 1/8, 3/16/, 1/4, 5/16, 3/8, 1/2, and 5/8 inch sizes are common.

I have done virtually the same thing, on a larger boat using a Home Depot plastic drainage pipe compression fitting for a sink drain. This is for a one inch diameter shaft, and I installed it on a 14 foot electric boat swinging a 14 inch diameter x 17 inch pitch 3 blade propeller. I replaced the plastic ring that forms a static seal on the plumbing tube with greased yarn, and tightened the plastic compression nut on this packing. That packing has been in place since 2004, and since I converted this boat to steam power last year, it has just started to leak.