Outrunner for a 20"cat

[Simon.O.]

As usual I have been up and down the pages and have a fair idea of what I need.

I need to replace the 23"Balsa cat that had a fatal run at the weekend and I am now looking at a hull between 18-21" loa. As I like the long overhang and a prop well aft of the sponson rear, the effective length of the hull will be closer to 18"

I have run a Feigao 12S(2800+kv) motor on 4S to a 432 prop before in the 23"hull.........It was well fast.!!

I am keen to have a go with an outrunner and broaden my knowledge base. They are very popular and very cheap. That works for me !

Here is a possible setup.
This motor

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9021

My reading tells me that there are two 450 size Typhoon motors and the shorter one is close to 4000Kv and the longer one is 3600Kv.

Now I can run the lower Kv motor on 4S or the higher Kv on 3S and both will give me wicked rpms..............so far I am happy.
If I feed either of these to a 432 ( my prefered prop for this build ) what sort of Amps am I likely to see ?
This will help me choose an esc. 60, 80, or 100+A and then my packs.
Do I need to prepare for a 60A load or a 120A load?
Is there a way I can convert data from FEcalc for estimates, say use a 380 can ?

Keep in mind I am a solo sport boater and like close to SAW setups.

Don't be afraid to shoot me a PM if you are unsure of your data. I will take any and all input and make a decision then.

[ozzie-crawl]

hobby king says that motor is good for 20-28 amps max (probably constant)
have a look at these more $$$ but more to choose from, motors are rebuildable and they sell spare parts.http://www.arkinnovations.com/shop/i...ex&cPath=16_46
i run a 3026 1900kv motor on my vs1 tunnel on 4s with a x642, my amp draw is around 66 amps average, speed is around 40 mph.
this is a 30" 2.5 kg boat so a 22 series would probably good for a 20" hull

[norbique]

Hi Simon, check this out : Turnigy 2836-2350kv Brushless Motor

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7993

review:
http://blog.hobbyking.com/blog/post/...ess-Motor.aspx

[CornelP]

Simon, I run the 450 typhoon in my ECO boat, on 2S with a 60A Seaking. During tha practice on sunday, running full throttle for 6 min, it got barely handwarm, the ESC was cold. I did a measurement with the boat in the water, static at full throttle, with a submerged 29mm prop and it will take about 35A. I would say that this one (3550) on 3S will be more than enough...

[Simon.O.]

I have done a lot of reading over the last few days while at work, even after blowing the trans on one of the fire engines.

This motor is the first suspect for my new build.
http://www.hobbycity.com/hobbycity/s...0kv_(450_class)
The reviews have folk who use it for EDF's at over 800W and that is enough power for me.
I read that this size hull (especially the Baby-Freya) will be fine with a 380L or XL and up to 80A draw on an innrunner. This equates to the power area I want to be in.

The 3600kv Outrunner on a 432 should net me close to low-mid 30krpm at the prop and well under 100A.
My proposed setup will then be 1800mAh+ at 30C or more in a 2P format. 108A total Amp delivery.

All going well this should be close to or beat 40mph on the water.
The bigger 23"(wet) cat got low 40's with a 432 spinning in the mid to high 30krpm area.
Keep in mind that all of my rpm figures are calculated with the assisstance of FE calc and a few formulas of my own and I have no way of confirming them other than sight and ear.

I will build the new cat to take the 28mm motor and allow room to fit an Inrunner if the torque roll effect of the OR is too much.

Lines and numbers are scribbled on paper and awaiting a build.

[CornelP]

Simon, I did another run with the ECO on a 40A ESC, still with 2S. It still works perfectly for 6 minutes... so ampdraw is a lot less than 40. I'll try with the 30A in the weekend. ... need to buy a datalogger...

[Simon.O.]

Another slant on the whole issue.
I currently have an older (tired) 12S about 2900kv motor I believe.
On 4S to a X432 it is nuts and 3S to a X637 or K40 produces smiles too.
I found that the 4S setup was not perfect for the size of hull that it was in, close to 25"loa and 23"wet.

I can fit this 36mm dia motor with a cooling coil or jacket into a new cat, easy when the new cat is not made yet.

I am confident that the 4S setup to the small prop for insane rpm will be good.
I can easily do the 3S setup to the bigger prop(s).

I need to buy new packs either way and a new speedie is not out of the question either. I have props and more CF ones on the way as I like a box full of CF's to trial with.

Here is the big Q. Do I:
1. Go with the 12S on 3S to a bigger prop
2. Go with the 12S on 4S to a smaller prop
3. Get the 3600kv 450 class outrunner and go 3S to the small prop.

[MarkF]

I'm going to try the 3600 KV typhoon motors on 3s and 430 counter rotating props on my 24" cat. I think this will be a fast and reliable setup.

Mark