pmdevlin

I have a dilema, my 42" Huntsman, heavy all ply, uses a graupner 700 bb turbo 12v, direct drive, 2 x 8.4v 3300nimh wired to give 16.8v, 40 mm 2 blade "s" plastic prop. THis probably isnt the best set up, but its what I have. For 10 mins, it gives a superb performance, very fast planing speed, which is what I want. I have been offered the darke horse motor for a very reasonable price. It will run a much higher voltage, and I was wondering if this would give equal performance to the graupner, but a better run time. I would like anything over 15 mins, after 8 to 10 mins the performance goes right off to a crawl, by 12 mins. I have tried other batteries, its the same, the prop lines up fine, no resistance etc, the esc can handle much higher volts, and is water cooled, as is the motor, which runs cool when water cooled, but far too hot when its not, which suggests to me the set up is working too hard

In very long winded way, I want to know if anybody has any feedback to compare the motors, as I think the graupner is very amp hungry.
It has been suggested that with either motor, I should be running a gearbox, but I just cant understand why! If the ratio was say 3:1, does that mean that for every 1 revoultion of the motor shaft, rather than getting 1 revolution of the prop with direct drive, I will now get 1/3 of a reviolution, so does this not mean a gearbox will slow things down?
The best result for mw is keep the graupner, but sort the setup out, if I get the darke horse, then I need to upgrade the batteries, more money! If I can see that the darke horse will be more efficient, then it will be worth it I suppose.
Sorry to go on and on!
Many thanks
Paul

retaobcr

I'm no genius but a 42" boat on a single grauper and the cell count, something has to go, equipment wise. Bl and lipos is your answer. Now the other motor mentioned doesn't ring a bell. Now from what i gather , this motor is from the European area. The thing is if you continue using what you have but want more, something will give out and probably cost you a arm and leg, Not trying to be rude but these are facts. The bigger your equipment, the higher the price to use or play with. Best of luck on your choice!

in-d-boat

Have you thought about trying a 12 V , 7AH gel cell battery? I have a 46" SeaQueen that ran really well with the 700( CaulderCraft ) motor that came with it. But it ran even faster when I replaced that motor with a Speed 900 BB Graupner motor, and propped with a 3 bladed Rivabo prop. The 900 had the same bolt pattern and spacing as the 700. The only thing that was a problem was machining the U-joint coupler to fit the motor and the prop shaft. ( I probably could have purchased one, I know). I can get over hour run time from it, but that's not screeming it at full throttle the whole time either. Just a thought.

In-d-boat

pmdevlin

Hi Retaobcr, What lipo and bl can you recomend for this size of boat? I can only find stuff relevant for helicopters and planes

Hi Indboat, I tried various 12v and 6v lead acid, run times where great, put performance was really "put put" around the lake! I wonder is my prop is all wrong for this boat?

retaobcr

Go to Offshores site and look up bl Feigao in the 540xl section. I see no lipos there. Lets see, i would go saddle packs and reason is big packs are loooong and hard to fit, so saddle packs make sense. 14.8 for voltage but i'd make a harness for series 7.4 + 7.4 =14.8 and i'd make a harness for parallel so you can double the mah's. Contact Steve at offshores and Steve will send you to www.battlepacks.com but for me i go to Common Sense RC. I'm trying to be exact but it's real hard. One other site is Rumrunnerracing forum, there are just a few guys with the answers. My boats are 30" or less and i have 11 monos and 1 airboat.

retaobcr

You didn't mention esc ( size ) in amps!

pmdevlin

esc is mtroniks no limits, will handle 2 motors easily, so no worries there. Will a bl operate on nimh, or do they have to have lipo?

retaobcr

Bl has to run with a brushless esc and a brushless esc can run on nimh or lipo.

boater-117

here is your answer-

http://www.shopatron.com/product/part_number=3019/135.0

a nice low Kv. one for your huge boat!

(you really should just drop a zenoah in it)

retaobcr

boater 117-that motor can use cells of 1.2 per cell and rated at 4-7 cells so total rpm will be 22,680 but the way i read this gentleman, he want to keep improvements in cost down. Now $204 and esc maybe above his budget but that isn't a bad deal at all on 7 cells but runtime will be way down.