Triple-Screw Boat in River in Boston

[Queequeg QuintParticipant @queequegquint38270]

I originally shared this video in the Build Blog section, but since I’m no longer building it, I’m putting it here.

It’s my triple screw boat that I designed a couple years ago. It’s running three MFA Como Drills 800 motors, turning three 55mm five-blade brass propellers, on a 12-volt NiMh battery pack with 8400mah. One MTroniks ESC operates the center motor, another MTroniks ESC operates the two outer motors. The center motor and the starboard motor turn counterclockwise as you face the stern of the boat (looking at it from behind the boat, that is). The port motor turns clockwise.

When running all three motors, the turn radius is not too good. But when I deactivate the center motor, the turn radius is beautiful. Same if I operate only the center motor.  The boat has three rudders, one behind each propeller. I The rudders are so effective at keeping the boat in a straight line– they give the boat the appearance of riding on a submerged rail!

Having a third propeller did not significantly increase my speed, but it does give me great authority at lower speeds. I truly love the uniqueness of having three propellers.

The runtime is splendidly decent, probably over 40 minutes. That surprised me, because I thought the battery would drain quickly.

I usually don’t drive this boat on an open river, but on this day, the river was unusually calm — except when an angry police boat drove by quickly to warn kayakers to get away from the fireworks launching site which had been set up for the Fourth of July here in the United States. His boat would create a huge wake! When he would create a big wake, I would send my triple screw boat out toward the middle of the river, and try to hit his waves going very slowly and at a slight angle.  Seems to work nicely everytime.

[ashley needhamParticipant @ashleyneedham69188]

Hi Q. good video clip. your a braver man than me to operate on a large river!

Boat going well, and having a bit of weight and oomph certainly pays dividends when using in the open water. good stuff.

Ashley

[Queequeg QuintParticipant @queequegquint38270]

Thanks Ash,

It’s quite a boat I’ve built, and I’m very grateful for this forum for all the information I learned about propulsion. The boat had ooomph for sure, even on this open river, but it did take on quite a good amount of water. It has no leaks, so I reckon it was from water splashing over the top of it.

Now that’d I’ve done a triple-screw, I keep wondering if it’s time to build a quad-screw!

[John W EParticipant @johnwe]

hi there

now that we have mastered and built a good seaworthy boat, by the looks of it, triple screw – you are thinking about quads.   Different ball game again – couple of ships I can think of to model would be, warship, passenger liner, or hows about a dog boat/rather large MTB – they had 4 screws.   Just remember that the two forward screws rotate in opposite directions to each other and the 2 rear screws rotate in the opposite direction to the forward screws – also think about the space for the motors.

Couple of pics  – one of HMS Exeter setup and one of the dog boat.

John

[Richard SimpsonModerator @richardsimpson88330]

Question John, why are the two outer motors Speed 600s and the two inner motors Speed 500s?

[John W EParticipant @johnwe]

hi there Richard,

Answer 🙂 the photograph was taken whilst I was trialling a fit of the motors in the mounts in the hull, along with couplings & etc.   So, they were (at the time being) the motors that I had at hand – as they are both the same basic size for the screw mounts holding the motors.  Now there are 4 x 500’s in the hull of the finished model 🙂

John

[Richard SimpsonModerator @richardsimpson88330]

There’s me thinking it was something deep and technical that I hadn’t come across before! Thanks John.

[Queequeg QuintParticipant @queequegquint38270]

My triple-screw boat was just involved in what we call a tug-of-war contest. This was not the most brilliant idea–  many things could have gone wrong very quickly. Fortunately, both boats survived, and here’s a video:

 

[Colin BishopModerator @colinbishop34627]

Shades of Rattler and Alecto.

https://www.philipkallan.com/single-post/a-tug-of-war-naval-style-hms-rattler-vs-hms-alecto

Colin

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