Prop selection- SAW rigger

[Simon.O.]

As some of you know I have a bigger rigger
http://forums.offshoreelectrics.com/...mon%27s&page=3
It is my solo/SAW/Gps rigger and it needs to get wet again.

It will get a Turnigy 180 instead of the Mystery 200's that it ate like pretzels.
On 4S the shaft speed is about 33krpm and that gave me near 70mph with a well worked 642.
Now for a lot of reasons I would like to feed it with 5S and this will give me a potential shaft speed of about 40krpm.
I have a handful of props ready to spin on it and would like some qualified input as to which are the best to start with, I have my own ideas but I am not familiar with the loading of the 3-bladers

The props are listed with the forward mm bite in brackets
637 (59mm)
640 (64mm)
438 (53mm)
537/3 (55mm)
440/3 (56mm)

These are the only props that I have that are up for consideration for a 5S burst with this setup. 6XL(2800kv) on 5cells

My gut feel is go with a 438 for kickoff and then move up. Do I tackle the 3 bladers as well or stick with my friendly 2 bladers ??

I know this is a tough call and all I want is opinions. No one will be held to that. What I do is my call and if the smoke blows then it is my fault.

[Fluid]

A 6XL on 5S should give you a lot closer to 50,000 rpm than 40,000, totally inappropriate especially for a Chinese controller since you won't get the rpm nearly that high. Actual rpm will be a lot lower, meaning amps will be through the roof. Your 33,000 rpm is too low for that motor which is why you smoked the cheap Mystery - amps were likely well over 200. I would not expect much different result out of the T180 with the marginal batteries fading on you.

My suggestions:

- Buy a decent 4S pack, Hyperion G3 45C/5000 mAh or equivalent. Your current pack is part of the reason you are blowing ESCs and are limited in speed.

- Put on a hydro prop! Oval mono props are not the fastest for riggers. Stop treating your rigger like a girly boat! Try these: v937/3, v940/3, 2041, 2140.

- Set the timing to 15-20 degrees.

- Put an extra cap or two on the ESC.

- Limit runs to two passes and bring it in.

Good luck!


.

[NativePaul]

I'm liking a n940 on a 6xl with himodel 200A esc on 4s1p in a rigger. its very fast stock and ovals well cut down to about 34mm for runtime without losing much speed. haven't tried the V series on it yet though, they may be even better.

[Simon.O.]

Jay, as always I appreciate your input.

You are correct that the older 4S pack I have is one of my problems, that is why I am keen to move the 5S 4500 40C set out of the cat and into the rigger.
I based my rpm estimate on the following equation
3.7(loaded volts) x 5 = 18.5v
2800kv x .8 (eff) = 2240
18.5 x 2240 = 41.4 krpm
This is how I have done many of my estimates, not to say that they are right but they seem to work for me especially when I add in props-slip and estimate speed.

I hear you on the props, but the list is of the props I have here.
I am not looking for much more speed as I am happy with mid-sixties a kiss at 70 would be all I want. I am not keen to push a bit of tree too fast

My other option is to get a new 4S pack (as more than one person has told me too) plus the T-180 speedy, and be happy with what I have.