Twin Jolly / Ammos/ 4S, what props ?

[G Doggett]

I have repowered my twin Jolly with two Ammo 2300s, 2 X-Power 100 ESCs and have taken the plunge to 4S 5000 lipos, but am unsure which props to start with.
It was uncontrolable on 2 X 8XLs with 2 X 12 NiMH.
The rpm is going to be pretty high at 34040 ( 14.8 X 2300 ) so I was going to try a pair of Graupner counter rotating K40s.
This is just a sports boat so was hoping to keep the amps below 50 on each motor.
Any advice would be appreciated .
Graham.

[Mich. Maniac]

I have the maritimo with exact setup except the motors are 8xl's. I am starting with c/f 45mm props. I am pretty confident with fe calc that this will be around 55 amps if not under that. I wanna get an idea of what dia. will work and go for machined props from there.

[Jeepers]

I like the Octura X440 on 12 nimh cells with an 8XL, I managed to take out a 125amp CC BC with a X445 prop, 12cells nimh 8XL.

[SJFE]

Graham it's not going to be easy fiding a se of CR octura props for your app. I asked for CR X637s and there is none. I suggest you look into the new CNC props. With the weight of your setup, kv & size of the hull I would be looking @ somthing in a 3 blade around 38mm. Happy hunting.

[txboatpilot]

When ordering CNC props, be very carefull when selecting the "pitch mm" it can drastically effect handling and heat issues!!! Alot of the CNC props CMDI is putting out work well on riggers and hydros, but not so well on V hulls and Cats.... They are supposed to have some new "X" style props out very soon... I would keep an eye out for those!!

[Ctonez]

with so much RPM to spare, I'd go really small and think about getting shafts with 1/8 stubs. If you go with 3/16 props, you'll only be able to use the lowest part of the range...seems you'd have more flexibility with the 1/8 props, and have a better chance of meeting your 55amp requirements.
a 437/3 blade gets my SV to 53mph+, which as we know is plenty for that hull on an oval...
As far as finding right hand AND left hand props...I'm not sure what there is available for RH props with 1/8 bore...so maybe I'm leading you down a dead-end.

[G Doggett]

Oh dear, maybe choosing the Ammos wasn't such a good idea.
I must admit I hadn't calculated how many rpm they were going to produce on lipos.
Maybe a pair of SV motors would be a better choice as they would spin at 26640 rpm ( 14.8 X 1800 ) and then I could use my X442 props, or maybe a pair of ABC H1516/3s.
The X-Power 100 ESCs can be programmed for 6 pole motors and I have the neat little Program Box. Hmmmmmmmm.
Graham.

[Steven Vaccaro]

Graham do you have the graupner 40 & 40L?

[G Doggett]

Yes Steven
I have the Graupner K40 r/h and l/h, but I am concerned they will pull more than 50amps each with the Ammo 2300 motors.
Might have to invest in an Eagle Tree as there is not much experience or info out there with twin set ups.
Graham

[Ctonez]

Yes Steven
I have the Graupner K40 r/h and l/h, but I am concerned they will pull more than 50amps each with the Ammo 2300 motors.

I dunno, I think you're still under 50 amps...I've never run a twin setup, but part of the theory is that 2 motors makes things easier on the motors themselves, right?

My data input is this: I've run the Ammo in my SV on the Stock SV ESC (rated @ 50 amps) with a detongued x440/3...stuff got hot, but not too hot...just hotter than I like (150ish motor, 110ish ESC, 130ish lipos). Running a Barracuda 125 helped temps, as did a detongued x437/3, and I still GPS'ed a speed run @ 53.xx mph, but the boat was riding prop only. you'll be pushing more weight, but I don't know how that is offset by having the twins...either way, I'd think the 40mm's will work. you know the drill...check temps often and see what happens! Sounds blazing fast to me.

My point in suggesting the smaller prop sizes (if they're available) is that you'd probably still have lot's of speed because there's oodles of RPM, but the system would give you plenty of runtime and equipment reliability/longevity.

[G Doggett]

Thanks, thats the sort of info I'm after from someone who has actually run an Ammo on 4S lipos.
I'm sort of flying blind here because nobody seems to have run this combo and certainly not as a twin set up. I don't think the FE Calc is any help either on twin drives.
The main reason to try keeping under 50amps each is simply because this is a sports set up and I want a reasonable run time without having to carry heaps of batteries.
I'm not too fussed about the top speed, but 45 mph would seem reasonable considering the total power would be around 1400 watts. ( 14 X 50 X 2 ).
My gut feeling is I should be running a pair of 36 - 38 mm props but these don't seem to exist in counter rotating pairs.
Might just have to give her a run on the weekend with the K40s and see what happens.
Graham.

[Steven Vaccaro]

Graham you can easily file down the 40 carbons to 38. I have done it to larger props with good results. I start at the tongue and work up to the tip.

[robby76]

My gut feeling is I should be running a pair of 36 - 38 mm props but these don't seem to exist in counter rotating pairs.
Graham.

abc props offers the following;
1516, 1.56 dia. inches, 1.6 pitch ratio, 2.496 nom pitch avg (in.), 39.624 dia mm cad file, 38.847 dia mm casting, 63.398 nom pitch, 3 blade L&R, 0.187 bore, $29.95 each for the 3 bladers.

Steve here @ OSE could probably get them.

being beryllium copper could load motors. not sure.

[robby76]

do post some pictures of inside/out for us to view.

[G Doggett]

Here ya go Robby.
I bought this as a bare hull from Fast Electrics in Australia and have made my own twin drives.
I'm hoping the drastic weight reduction from 2 X 12 NiMH to 2 X 4S lipos will make a huge improvement in the handling.
If I can get her to go half as good as she looks I will be happy.
If the weather behaves this weekend I might get to have a test run.
Graham.