Proboat Miss Geico 36 with Dr Props 645/3

[hughb]

Here’s the first run of my Miss Geico 36 with the Dr Props 645/3. Only other mods were a quick polish of the flex shafts and rudder sharpening. The starboard motor mount seemed to be slightly out of alignment so I gave this a slight adjustment.

https://www.youtube.com/watch?v=Qg6LwGKzD44

Out of the hole the boat nearly launched in the air. Also I didn’t realise the boat needed more area to slow down compared to the smaller boats I’m used to (though it makes sense, bigger heavier boat, more inertia). No idea on speed, but I’m guessing lower than stock due to the 3 blade props? Either way is a blast to drive, and looks great with the shiny stainless steel props.

On a subsequent run, I noticed the right battery become extremely warm and swollen, following mainly right hand turns. I’m thinking to swap to bullets so can run 6S2P to share the load on the batteries.

[fweasel]

How long was your run? What were the cell voltage on your packs after the run? My guess is that you ran the packs down too low

[hughb]

Timing of the run I'm not sure. The surprising thing was the cell voltage was still roughly 3.6v. But that right battery was definitely toast. I could feel the heat coming through the boat when picking it up out of the water, and significant swelling. Admittedly they were cheap lipos from eBay.

[fweasel]

3.6V is too low. Aim for a return voltage of 3.8V per cell, which is much better for the health and performance of lipo packs. I would suggest you time your runs so you know when to bring the boat back. Depending on your setup and driving style, that could be as short as 2.5min or maybe 4-5min.

[hughb]

Thanks Fweasel. I assume the voltage would drop even lower when under load?

[fweasel]

Yes, but voltage sag depends on the quality of your batteries. By the time you get the boat out of the water, on the bench, and untapped, the cell voltages should have stabilized. That's when you're looking to see 3.8V. If they're lower, shorten your run time.

[Jesse J]

What batteries are you using ? Brand, Mah and c rating

[hughb]

That run in the video was using 2 Revolectrix 6S 5000mah 70c batteries.

The batteries in the later run where one of them swelled were Zopp Power 6S 4000mah, 50c I think.

[srislash]

There is a constant load going on in those runs too Hugh. That kind of steady load really knocks down a battery. I think I would try 2blades and either a little less pitch or smaller diameter. How is it handling with those props on it?

But I bet b the props look killer, I bought a couple sets of V9 Drprops just for ‘looks cool’ factor on my HPR. Then actually run pretty well too.