47" twin mono to one outdrive build

[Jacked1]

Here is what I have so far of my old 47in gasser hull that has never seen water i got from ebay about 7 years ago that was collecting a lot of dust and the gearbox i made to run a prather 275 with two motors to one outdrive. It is right at ten pounds right now without the batts. I know the boat only has one motor in it now(kb45 10xl) but two of these are on the way..

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11143&Product_Name=Turnigy_T600_Brushless_Outrunner_for_600_Heli_(880kv)

I made it so i just have to change the gears and put in a new motor mount plate when the motors come.
Let me know what you think! Any and all feedback is greatly appreciated!

Happy boating!

edit: Oh and the first pic was taken before the shaft tube was epoxied in so it is not really that crooked now. haha

[Jacked1]

One more pic!

[Jacked1]

Oh and the gear ratio right now is 1.7:1 and i am going to run 6-8s with the new motors.

[Jacked1]

I might have video tonight of the first run.

[Spot Me 2]

I might have video tonight of the first run.

Nice! looking forward to seeing how this works out.

[Gerwin Brommer]

Do I get it right ?
Gearratio 1.7 to 1

So the gearbox is bringing back the rpm's on the shaft ?
880 kv motors on 8s geared 1.7 to 1
What kind of prop do you wanna use on this large hull to get any speed at all ??

[Jacked1]

Do I get it right ?
Gearratio 1.7 to 1

So the gearbox is bringing back the rpm's on the shaft ?
880 kv motors on 8s geared 1.7 to 1
What kind of prop do you wanna use on this large hull to get any speed at all ??

It is a pretty huge prop! haha But i can see your concern.
I am going to be useing the prather 275 which is a 74.9mm prop and has a 4.3in pitch from a gasser. (the one in the pics) Gassers usually run between 14,000-18,000rmp and that would be at 15500rpm with what it has now with 8s and the new motors.
If you calculate the pitch and gear ratio it is the equivalent to useing a 45mm prop in direct drive. And I made it so i can change the gear ratio by changing the drive gear ($4-$5 each) instead of a different balenced and sharpened $20 prop everytime. I wanted to use a lot of parts from big gassers because i have a ton of them already.
I will probobly wind up going to around 20,000-22,000rpms (1.3:1 gear ratio) at the prop when it is all tuned with the new motors. That is 81mph prop speed at 20,000rpm.

[Gerwin Brommer]

15.500 in NO load, I think ?

[TotalPackage]

the gear ratio should actually slow down the shaft rpm to a point thats useable by the prop while allowing the motor shaft to turn fast like it wants to.

[TotalPackage]

why not a 1 to 1 simply tying the two motors to one shaft and 5s lipo

[Jacked1]

I thought a lot about two inline outrunners that have shafts sticking out of both ends but i could not find the right rpm and power level per motor except the scorpions and they are out of my price range. There are tons of inrunners that would work but no way to run them inline without extending the motor shaft somehow. Also to get the power level i want I need the hi voltage without going over the rated number of amps for the motors. So i thought the gears would be the best way to do it without spending too much money and using a smaller prop that would be more prone to cavitate.

The 15500rpm with the 1.7:1 gearing would just be to start out too like you would start out with a smaller prop and go up from there in a normal direct drive setup. I don't want to over estimate and have everything pull 150amps and burn something.

Doby's Rio 51 (SWEEET!!!) is running a 3blade prop that is a little smaller than this one and he has a freggin LMT 3080 12T!! That thing is HUGE!!! rated for 11kw!!!! And with that motor on 10s is 16206rpm and over 60mph.

edit: There is a video on here somewhere of it doing a blow over and i think he said it weighs 18.5 lbs!

[Jacked1]

Just got done running it for the first time!! The flex shaft to prop shaft coupler broke as it got on plane Of course the only spot in the drive i didn't make is the part that sucks! i have a short vid of it happening.

[Jacked1]

http://www.youtube.com/watch?v=q70UFhLNpiA

[Jacked1]

I have decided on a name for the boat since i go to OSU and it is red!
Scarlet and Grey Goose!

[TotalPackage]

get u a fdm gearbox and save yourself the trouble but a 1900zr series nue or a scorpion will give you what you want direct drive