Air prop driven 3 point hydro.....74mph

[crispyspa]

Just thought I'd share. I do have a question though. The ESC was a Swordfish 300a hv. During the video you'll hear some screaches from the motor. This happened when I pulled the throttle a little too fast. You'll see at the end that the timing or something is really messed up. Can it be repaired?


https://www.youtube.com/watch?v=ukcyJQemYT0&feature=gp-n-y&google_comment_id=z13kt1si2yzlfnodi22lize5gveycxeh q04

[Fluid]

What is the timing set to now? Most outrunners run best at 15 degrees, but if the motor cogs back down 5 degrees and try again. It is possible the ESC has a problem, but it could simply be the wrong timing setting. Did the ESC get wet? Is the ESC still under warranty? Could save you some $$$ if it is.

You are not at terminal velocity for the boat. It blows off because you chop the throttle too quickly, this causes the stern to sink a bit, increasing the aoa of the boat, which is still going pretty fast. Result is a blow over. Easing out of the throttle or adding some material to the rear sponson to add more support or depth to keep it up when off the throttle could help.

Nice boat BTW. Too bad Chris stopped selling the kits. What prop and voltage are you running?




.

[crispyspa]

The timing was set to "auto" as I did not know what was the best I figured I'd let the ESC do the work. It didn't get wet. I tried adding extra sponsons at the rear to raise it a bit, but that just made the front end plow and it would not even get on plane. I had thought of a gyro controlled wing hooked to the throttle so when I let off, it takes the task of down force.

Not under warranty, I got it a year ago. There is a Hz setting and that was set at 12.

Prop is a 16x10 APC with 14 cells or about 56 volts....which is WAY over the max voltage for that motor which is rated (I think) at 11 cells.

I kind of wish that Chris didn't give up the biz, but I understand. The stress of a new job and increasing responsibilities at that job just left no time for family, job and hobby. Something had to go.

[Fluid]

These big multi pole motors are challenging to ESCs if high rpm is desired. If it is a 12-pole motor (I am not certain what it is) the ESC will have to switch 3x faster than with a 4 pole motor, and the ESC may not be able to keep up with it. Your setup may be turning close to that terminal speed, hence the ESC lost control of the motor. Just a thought.

Too, set the frequency to 8 KHz and timing to low. The ESC might still be okay - or not - but try these settings and let us know.

Edit: I ran your motor/voltage/prop through eCalc and it shows the following:

145 amps
12,233 rpm
6162 watts (mechanical)
90% efficiency
36 lbs static thrust
116 mph pitch speed

That's a lot of power! But well under the amp rating of the ESC.



.

[Mxkid261]

That thing is sweet! Very cool boat. Btw, what part of Wisconsin are you from?

[kfxguy]

You know, this seems to be a thing with the sf300 escs. I've seen a few fail after a hard crash. I wonder what it is that's happening. I've had one instantly die after a hard flip. My buddy has had a couple do the same.

[dmitry100]

Man that thing is fast... with an airplane prop of all things! I wonder what that thing would be like with some twin electric jet turbines ;)

[Fluid]

...I wonder what that thing would be like with some twin electric jet turbines...
A lot slower. EDFs don't put out much static thrust, especially compared to the OP's setup. The 'official' NA record for an air prop boat is in the 90s. At one time Japanese air prop nitro boats were the fastest R/C boats in the world.


.

[dmitry100]

Dumb question but... what kind of thrust DOES it output if not static thrust? I thought they were THE way to go for thrust for airplanes.

[Rafael_Lopez]

Hopefully you have it all worked out by now, but I've ran in to this before with high voltage and "surface" ESCs, on high pole count motors. They simply don't have the programing to run high pole count motors; they cant keep up with the rotors location because of the high pole count. Get yourself an "air" esc and you'll see the problem solved.