New to BL

[RUNNERX]

I am looking for advice on prop selection for a Hacker b50-8s with a 70a Kontronik. It is going in a MHZ shockwave it is 25"X5.5" I will be running 6 cells.

I have been told by the guy I bought it from what he was running, and I know his advice can be trusted. I just wanted to see what others had to say.

Thanks

 

[SteveReesor]

Sounds like Kelly Brooks boat. I don't know what prop he was running on it, but it will depend upon what you are setting it up for. 5 lap oval or 4 minute offshore....assuming you are going to race it.

I would start with an X432, and check the temperature of the motor, batts, and esc with a heat gun. The temps should come in around 120-130F. If your sport running it,it should run all day like this. I would then try an X435.

If it has a wire drive, you may be able to run an X632 on it...but really pay attention to

the heat. All of the above also assume it has an 1/8" stub shaft.

Octura has come out with a new prop...an M435/3...that might be a great prop for that boat. BTW...its a great boat. If it is Kelly's, he has it set up so well that whatever prop recommendation he has...go with it!

Steve

 

[RUNNERX]

Yes the hull is the same as Kelly's. Just runing it for fun, not any racing around here. All I have so far is the hull motor and esc, the drive and all I am open on. I am thinking of going wire drive though.

 

[brooks93]

with the rpm of the 8s being about 600 more rpm then I am running I would start with a 430 and check heat..I would think for a 4 minute setup a 432 or a 432 with the tongues removed would be perfect.. Personaly the motor is a bit hot for a sport runner but, will probably work.

you will want the cg to be in the middle of the front step and the start of the second step.

Steve I still have my shockwave.. Can't seem to want to sell it because its such a great running boat

 

[Andrewg]

thats a nice motor for a N2 rigger. rather than a long mono.....

 

[brooks93]

andrew I agree fully.. a 11S would be a better choice or a lehner 1530/9

 

[RUNNERX]

I picked it and a knotronik 3sl 70-6-18 from a friend for a great price. I will try it with the 430 and see how it goes.

If I am using heat gun to check the temp what would be considered hot.

 

[brooks93]

I consider the cells to be to hot at 140 or above and the motor if its 140 or above.. but, thats just me

 

[RUNNERX]

OK, thanks.

 

[Andrewg]

For safety sake start with a X427 - that is a very hot hot setup - much hotter than the best racers run in that N2 mono.

It would be unwise to go out with it in such a long hull for the first time, w/o brushless experience .

With a motor like an 8S - its always a low resistance - high amp setup - high rpm setup. It is always at risk that if the prop fouls it will rapidly put the cells and the controller at risk. Also the motor has maximum efficeincy at high amps not what you want for the type of running you want to do.

However an L would be your best option, maybe a lower revving S if you werent not concerned about speed thru turns

In N2 mono motors 3200-3600rpm/v motors do well with GP 3300's - but they are the setups the top guys use.

For sport you want a motor with max efficiency around 30-40 amps - that might seem a lot less power but it makes it possible to run like a hot race setup if you want simply by using a higher pitch prop. This is because the band of very high efficiency will be wide and at lower rpm.

Add to that if you want to do long run times you have almost zero range of prop choice and the motor will more often run out of its maximum efficiency band which will lead to more heat.

If the setup doesnt look fast and i mean FAST - get it out as it will be at risk of damage

 

[Paul Pachmayer]

Hey Guys,

You could toss that motor on a Hughey gearbox to soften it up a bit. I run an 8s in a 10 pound E-Maxx for close to ten minutes on 8 cells. That's at race speed I might add.

Paul.

 

[brooks93]

However an L would be your best option, maybe a lower revving S if you werent not concerned about speed thru turns

Sorry andrew I would have to disagree.. Being that I am the only one that I am aware of the actual race this boat in N2 offshore and have very very good sucess with it. L size motor is overkill a higher wind motor is a better idea.. A 11 or 12 S on a 435 would be idea or a 1530/8 or /9 with the same prop.

The length of the boat isn't the issue its so lite it doesn't matter.. Now the width is where the problem is. You do not want to go any bigger then a 435 on this boat or you will start to see handling problems because its so narrow. Thats why I run a 3500 rpm per volt motor so I can spin the smaller prop but, be just as fast as they guys run a lower rpm.

my rule of thumb when buying offshore motors is A use a gearbox then it doesn't much matter or B buy higher wind motors ie. 10, 11, 12, 13, 14, 15, 16 turn motors because the more copper in the motor the higher the eff. plus they tend to have more torque then the lower winds. S size motors in N2, L size for P, XL's for Q and up. N2 you can run B40 L's they would be equal to 1530 lehners

 

[RUNNERX]

I was thinking about gearing it after reading some earlier post with just a little reduction to keep it running smaller props. Like Brooks said its a needle and a big prop would roll it on its side.

I would also like to thank everyone for their input it is helping alot.

 

[brooks93]

a gear will help you out alot.. I would start 1.5:1 with a 432 and check to see what the temps are.. if you got room go to the 435 and recheck.. the 435 is the sweet spot on that hull.

 

[Andrewg]

I recommended the L motor because it has high effiiciency from 35-60amps but is a proven motor at national level racing. Very similar to an 8S but at a more sensible Kv - ie its usable with the props available. It is an excellent N2 motor.

I agree the S11 will give better efficiency at very low amps ie less than 30 amps or 7 minutes on 3300's. It will also be easier on the controller if things go awry. Its disadvantage is its softer midrange power (turns acceleration)

Before going to a gearbox see what runtime you have. A runtime of longer than 7 minutes will mean the amp draw is at a level where the motor is not running with high efficiency and may see it running hotter rather than cooler.

The S8 should work ok with a 427. Runtimes of less than 7 mins (GP3300) will indicate it is operating at good efficeincy. A 5 minute runtime with these cells should see the motor operating close to maximum efficiency with good power.

If the runtimes are short you might find it cheaper and less trouble to purchase a second prop and simply reduce the tongue (and some of the high pitch areas).

If they are longer go to a larger prop.

If you remain unsatisfied a gearbox may be the answer to a too high amp draw.

 

[crowebar]

Hey Kelly, How about makeing the trip down to nats to see if you can get by me and poor little "L" powered N2 Mono. (If you're busy playing dad I'll take a rain check)

I like the S's also, but I keep them for my small riggers.

Dick

 

[brooks93]

Dick by that time I will be playing daddy.. Trust me I would be there if the wife would let me. Come to the CAFE race sometime I will be happy to show you around the pond in offshore..

N2 mono yes a L series works great but where talking offshore, I know the L series work for N2 offshore. I have seen alot of them used in N2 Offshore but, they are also running 40 mm plus sizes props most of the time which in the case of this boat cause's server handling problems..

I have ran this boat dozens of times in race and fun. I know what I am talking about with this boat.. Anything over 35mm prop and you will have major handling issues. You get them with the 35 but, the are controlable.

 

[crowebar]

Ohhh, My bad.

I haven't got a clue what to run in N2 Offshore. I've never run that class except for saw's about 4 years ago and that setup was only good for about 20 seconds!

I was wrong, I was wrong, I was wrong. (I hardly ever say that three times!)

Dick

 

[brooks93]

LOL dick.. dont' worry your still my hero

 

[RUNNERX]

I may try direct drive but the gear box will not cost me anything to make. I have the gears and can machine one myself, so the plan it to do a 1.35:1 box. That way I have a few more props to use.