Another first time boat builder Info Request. Zonda, Fountain.

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Hi.
I am building 2 boats for a friend. I have been in RC for 40+ years and am very familiar with aircraft, but not model boats.

1st; 48" V-bottom Fountain, Castle 2028 motor, 800KV, single "Merc #6" drive uses flex shaft 1/4". 10S battery not bought yet.
Have a used Swordfish 240A+ HV ESC, may be pooched?
Want rough water handling, reasonably fast.
Any comments, what prop, Servo, Prop shaft height, C of G location, square shaft vs round shaft, Teflon flex shaft sleeve or not, capacitors, ideas???

2nd; TFL Zonda Cat (or 42" Fantasm) same boat. Sirius 1520-1500KV (x2) and OSE 80108 Arneson Drives. I can't find info on these motors so no idea of Amps on 12S.
Want 90+ MPH.
Recommendations; ESC's, Props, Rudder, C of G, Drive spacing relating to vertical edge of tunnel and bottom of pad, servo kg, Capacitors, etc. Ideas???

What is the answer to an On-Off switch that is water-proof? Antenna? Shaft tube lube / bending ?

Many Thanks!!

[Fluid]

First off, the Zonda is totally inappropriate on 12S with those motors. They will run on 6S reasonably well, maybe 8S for short runs; not certain you’ll make a reliable 90 mph with those motors though. Lots of info on that boat in the forums, use the Search function.

The Fountain will run okay on 10S with an x460 prop, you may be able to prop up a bit depending on the run time you want.

Why have you chosen the components you did, not knowing about FE boats? Or did your friend get them? Search is your friend.


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These were the parts supplied. On the Zonda, I assume we need max RPM of 60,000 or so. There fore ~ 40 Volts. 10S !
I will get different motors if required. Is the Serious actually a Neu-Castle motor? Are they any good? Why can't they take 10-12s?
Thx

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The Castle 2028- 800KV motor is only rated at 45,000 RPM. That would restrict it to 6-8S wouldn't it?

What speed should a straight 48" V bottom fiberglass boat likely achieve with this power? Single drive.
What size ESC will it require? Apparently no specs are available but it puts out about 8000 Watts.
Thanks

[Nevs]

Nominel 10s./37V x 800 kv 0=29600 kv... With a 460 prop you will probably have 250 A peaks. Speed will probably be 29600 x60 x 1,4 0 2,48 x60 = 149 x0,7 = 104 kmt / 65 mph.

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Thanks Sven. Working it backwards, what speed is likely with this setup / power to weight ratio? I am only guessing but 50+ MPH ??
I play with this math for full scale race boats at work.
Lets say 55MPH. Turning a 3.7" pitch prop at 25% slip would require 19,620 RPM. An 800KV motor would require ~24V / 3.7V = 6.6S Battery. That is where I come up with 6-8S Battery.
That is where I would want a current (Amperage) estimation. Can it really be in the 250 Amp range? I have a 180A ESC already, not sure if big enough.

Has anyone measured or logged a setup like this? I'd love to know. I asked Castle via email last night, waiting for a response.
Thanks!

[Nevs]

With a 60/1,4 you would end with 39 mph +/- 5 .on 6s... And 52 mph on 8s+/-7. Amp peaks with 6s. would be around "20-40" A. On 8s. around 120 A/average 60-80 A.

[Vin-m]

Use the speed calculator here on this website. It gets you pretty close. The Zonda you can get 85mph out of real easy w motors in the 1650 kv range on 6cells.

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Vin-m
What is the difference between low KV with hi cell count and Hi KV and low cell count? Same RPM ???
I would expect hi voltage = less amps, smaller wires, more efficient, same RPM and Power (Watts)
Thanks

[Vin-m]

Ya it effects amps. Staying about 35000 rpms with what ever set up you go with seems to be a reliable rpm. When you start to go above 40-45000 your better just doing saw passes.