Propelling an autonomous Hobie Cat with T500s

Hi Everyone- I have a Hobie 18 Tiger that I am using for scientific measurements (anchored, with the mast removed). I would like to add T500s and an autopilot to enable waypoint navigation.

I don’t need it to go fast, 1-2 kts max would be ideal.

According to the Hobie website the Tiger weighs 397 lbs. I assume that weight includes the mast and rigging, which have been removed and replaced with scientific equipment so the overall weight probably hasn’t changed.

My back-of-the-envelope calculations suggest that one T500 on each hull should be sufficient, but these are based on weight alone. I’m concerned that wind drag on the hulls, since there’s a fair amount of exposed surface area, might overwhelm the T500s.

Has anyone here tried to mount T500s on something this large? If so, would you care to share your experiences?

I have read somewhere here on this forum there is a rule of thumb for trolling motors: 2lb of thrust for every 100lb of weight.

Hi @nuballawalla -
You are ahead of me - I too have an 18’ hobie cat with no mast that I hope to strap T500s too someday!

I think it will move the vehicle at speeds greater than 3-4 knots without issue. Currently, I’ve been testing 2x T500s configured as a Diver Propulsion vehicle, with a single 4S battery, and hitting speeds of over 1 m/s!

I believe the acceleration you get will be determine by the overall mass, but the top speed will come down to the hydrodynamics of the system. The hulls are quite hydrodynamic, so if you’re not reaching speeds that you want I’d recommend changing your mounting approach and eliminating the T500 nozzle. The thrusters are designed to push hard, but not necessarily move fast through the water! I believe the maximum speeds possible with this approach will be 10-12 mph.

Please continue to share progress on your cool project!

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