motor selection for 20" twin cat

[Jesse J]

i have one of those hulls it was my first electric.I looked around on the internet and see some guys ran some pretty hot brushless motors in it they say the problem is the boat was only designed for about 25 mph.One trick is you have to file of the hooks on the bottom of the sponsons.I didn't know if you already new about that Jesse I know you have built some scratch built cats already.It was a fun boat to drive i was thinking of putting something in mine to use as a rescue boat.

Ahhh, the beauty of dealing with Meniscus Ben, he had that done already. He is suggesting that I go really big with lots of cells and is talking about what will be happening as it passes 70mph........

He has suggested a pair of these motors.

[Meniscus]

Jesse, those may still be more KV then you want. My purpose for suggesting lower KV is to allow for more prop options in L&R. There are some options in 380L that would work, but for the money, you can't beat that line of motors as you well know with the NS1.

The other aspect is if you're going for speed, then you will need the weight, due to the lift of the tunnel for this specific hull. Lower amp ESC's should be fine if you watch climb-out.

Hope this helps. If you end up trying one of the 380L from HK, just be sure you don't use the ones that are purposed for ducted fans. Most of the time they can't handle the amps.

[Meniscus]

Another thought, if you don't mind spending a few extra dollars, why not try a couple higher quality outrunners? For example, the Scorpions have the torque and will handle the heat. Just another idea.

[Meniscus]

Try this on for size: http://www.scorpionsystem.com/catalo...k22/HK-2221-6/

On twin setup with 3s she'd fly.
On twin setup with 2s she'd do a respectable 50mph on X442L&R.

You'll have to be careful with battery placement to get the balance right and running 3s, you'll run wet until you get up to 45mph. And like I said before, you'll have to be careful with climb-outs. Run the strut shallow and push COG slowly forward.

[Jesse J]

Sweet, thanks Ben for all the tips. I am liking that motor you posted, nice!We still have ice fishing for another couple months, so I don't have a whole lot of inspiration to work on boats - maybe when tax return gets back, I will pick this up and get me some good motors.

I am thinking I might be able to use a pair of Proboat 45A speedos - whatchutink?

[Meniscus]

I would think that the Proboat 45A ESC would be fine, again you'll have to put a logger on to view climbouts. Keep in mind that under no circumstances should you use the BEC. Typically to keep weight down, I use Energizer AA lithiums for receiver pack.

You will need to advance the timing on the ESC's so keep this in mind if you entertain other options. I'd have to look in my stuff, but I believe I have two Etti 45A ESCs that could work. The consideration is that the Proboat ESCs are considerably heavier than many others. Ultimately, a couple Seaking 60A Marine ESCs would be perfect. I often see them for sale from time to time and are fairly inexpensive used. The good news is, with the Seaking 60, it will handle a fairly decent spike during climbout and have advanced timing adjustments to match those outrunners. They also typically run cool, even if cooling lines become blocked or are running at reduced capacity.

Plus, with these scorpions, they are sick in riggers. I have one that is in my Renegade and haven't had the time to run it much. However, put it this way, I can hardly squeeze the trigger on that thing, even with small props. If these motors don't work out in this cat, they are perfect for some high RPM smaller boats on 3s. For calculations, as best I can tell their efficiency is around 86% give or take. Maybe higher for certain windings.

Hope this helps.

[Meniscus]

Jesse, it seems some folks are having success with these: http://www.hobbyking.com/hobbyking/s...dProduct=11177

See here: http://forums.offshoreelectrics.com/...ad.php?t=21848

Haven't tried them myself.

[Jesse J]

Hey Ben, this is the other end of the KV spectrum... aren't we talking high amperages?

[Meniscus]

Higher voltage = lower amps. If you stick to the small x430 L+R, then you could run right at 50mph on 3s. You'd end up running 3s2p (2000 to 2500mah 3s1p packs in parallel) wired to both ESC's which keeps load even. The reason for going with a larger motor is for additional weight you'll need to go faster and the fact that I know you won't be happy with just 50mph.

What I suggested was a lower RPM solution, using larger motors to turn large props which gives you more selection for prop choices. Plus on a windy day, you could go with less cells.

If this doesn't make sense, give me a call.

[Meniscus]

For twins, I always recommend starting with the props you'd like to use. Then determine if you can change the props to something similar. The reason for this is Octura has limited number options, even less in smaller sizes which would affect whether you're going to run 1/8" shafts or 3/16"

[ray schrauwen]

If you run a 1/8" shaft you can run any prop almost, if you think outside the hull....

Lots of carbon threaded C/R props... take a look at R2 hobbies, these are 4mm bore: http://www.r2hobbies.com/eng/products.php?cat=240

Threaded carbon props you need to drill out with a new 7/64" bit, then tap it with a 5-40 tap from industrial supply. They will thread right onto a 1/8th shaft. use a nylon lock nut to back it up.

To adapt to 4mm bore D/D props, use a piece of K&S tubing.

To adapt to 3/16" props use 2 pieces of K&S tubing.

Easy peasey, now you have lots of choices...

[Meniscus]

Funny!

Nice Ray. I don't run any carbon props as most of my setups run more RPMs. I was unaware there were carbon props in the smaller sizes. Definitely something to keep in mind.

[Karfrik]

Hi Jesse,wondering if you ever finished this boat....Albert

[Jesse J]

Nope, still in the box.

[FloatDaBoat]

Jesse,

Here’s a link for a Leopard 2850 (54 mm in length, 1000 Watts) that I run on 3S in my 18.75” rigger - - runs PDQ !!!

http://www.ebay.com/itm/300557027556?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649