Large hydro electric power ? - RC Groups
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Jan 28, 2013, 05:23 PM
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Large hydro electric power ?

I have built 6 of these. They weigh 4 .5 pounds with the top skins off. Should add no more than 1/2 pound covered & varnished.

I want to let people use them with NON - expensive motors. How many watts & what motors & props would plane it ?

Thank you.

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Jan 28, 2013, 07:51 PM
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Cost is all relevant to quality.

If you want rubbish then you pay peanuts.

However, there are some very cheap brushless setups available from Hobbyking.

I'd go with something in the 1000-1500kv on 4-5S with a 100A ESC.
Jan 28, 2013, 08:58 PM
Steps? What steps?
zozer's Avatar
Geeze, throw us a bone guy. How long and wide is the hull? How wide is the tunnel? What is the speed goal? Run time length?

Jan 28, 2013, 11:01 PM
RELAX. You'll live longer
785boats's Avatar
Seems to be a 45" x 20" hull. Nice & light though.

If it were mine, I'd try the TP Power 4092 1350kv on 6s. Only $100.00 for a good motor. From my experience, they are better than the Leopards.

A Swordfish or Turnigy 240 12s ESC. The ESC is always going to be the most expensive part if you want reliability.

Props, for me, would be starting with the m645, or the, ABC H5, Then the m447, working up to the X447/3 if the temps are good.

There will be other suggestions coming along soon, I'm sure.
Last edited by 785boats; Jan 28, 2013 at 11:17 PM.
Jan 29, 2013, 01:59 PM
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JimClark's Avatar
Scorpion 4035-800 look here for more info
Jan 29, 2013, 07:24 PM
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I had bought the planes from the Scale Hydro Museum in Washington ?

Retired & finally finishing the 6 boats up. I Do lots of RC electric planes.

Did the 8' WWII PTB with a Novak Reversing Super Rooster ESC & a car battery.

But this size was just skipped by me. Thanks for the 4035 800KV motor .
What prop diameter & pitch is average ?
I have used the Octura props & drives in another smaller boat
Jan 29, 2013, 11:50 PM
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JimClark's Avatar
they use a 57mm Graupner Series 2317 prop. I wasn't aware the Hydro Museum sells anything that big
Jan 30, 2013, 07:41 AM
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Hi Jim.

Maybe when it first opened ? They had tons of plans when I ordered.

This is what my boat will be. Always did like the side pipes.
Jan 30, 2013, 03:26 PM
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JimClark's Avatar
Ah so you just bought plan's. Must have been Newton Marine plans
Jan 30, 2013, 08:19 PM
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BINGO ! Jim.
I could not remember. The plans are EXACTLY perfect.. Everything lined up very easily.

Feb 02, 2013, 03:28 PM
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Amp Abuser's Avatar
So Rich what are the actual dimensions of the hydro LxW?
Last edited by Amp Abuser; Feb 02, 2013 at 03:34 PM.
Feb 02, 2013, 10:54 PM
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They are 45" long x 20" wide.
Feb 03, 2013, 11:06 AM
Steps? What steps?
zozer's Avatar
That boat is awfully large for a 4092 motor on 6S. Hydros this size take more power to plane off than do monos and cats. Most boats that size use 8S or 10S and a larger format motor. And a 45mm prop is a joke, I doubt it would plane a boat that size - normal diameters for 40"+ boats start at 57mm and go up to 70mm. Don't make the mistake of buying too cheap, then having to replace everything because it didn't work. Buying twice is an expensive lesson. Please listen to those who have actually built and run these large hulls, not guesses from those who are trying to be helpful but get it wrong.

If it were my boat (and I've built and raced FE boats up to 45") and I wanted to build on the "cheap", this is as cheap as I'd go:

Motor: Leopard 5692/730 (cheaper than the Scorpion and easier to cool)
ESC: Swordfish Pro 240HV or Castle ICE200HV
Batteries: 8S/2P/5000mAh packs with a minimum of 40C discharge rate
Prop: Octura x462 to x465

In my experience this setup should give reasonable reliability for the cost and will run the boat well. But an 1/8 scale 8S hydro is not the boat for the new-to-FE boater! Do not make this your first FE build. Start with an AquaCraft Revolt or UL-1 first. You will make mistakes which in the small boat will not cause much damage. In an 8S boat, the same mistake will cost a lot of $$$. Trust me, I have seen it happen at least ten times.

The above setup will run in the mid-50s, which is plenty for these hulls. There are three 1/8 scale round-nosed hydros in my club (one was built by Roger Newton himself) and they run great in that speed window. Much faster and they tend to blow off - no surprise, the originals did too. 55 mph translates to over 150 mph scale speed, right where the originals ran topped out. Have fun!

Here is what happens if you try to push the big boats too fast.

Last edited by zozer; Feb 03, 2013 at 10:35 PM. Reason: added photo
Feb 04, 2013, 11:02 AM
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Thank you zozer.

I did not realize big electrics need HUGE wallets times the 6 boats....

I will go to the gasoline engine. Larger weed wackers on sale.

Thank you
Feb 04, 2013, 02:26 PM
Registered User
I took a chance on a battery powered chainsaw motor for $25 as a test. At 20 volts & 2 speeds of 2.6 amps & 5.2 amps. What the heck. Seeing as how they are overloaded all the time. I will try it out.

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