Help me spec out my power system

[v-spec]

I usually take 3 charged packs and run for about 2 minutes per pack. I'm going right after I write this! Once my boat is setup I do a run bring it in check temps look for leaks and let it cool off about 15-20 minutes before the next pack. Where I run we get lots of onlookers and interested people and sometimes people with a new rtr boat out for the first time so I get to do a lot of bsing in between packs and before I know it I've made a few new friends and 3-4 hours have passed and I'm usually sunburned and ready to go home. At least that's what I do and I have a great time! I try and get videos of my boats running so I can come home and watch them and see how I can improve both my boat and my driving and bs on the forums the rest of my free time. I love this hobby. To sum it up, once you get into all the other fun aspects of FE boating I think the 3 minutes won't seem too bad! Ok time to go to the pond!

[T-Man]

As a matter of fact, I'm heading to the lake in a few minutes myself. I'm taking my PB Shockwave 26 and my Seaducer .21 nitro boat with me. I have time to recharge my electric boat with my car charger while I'm running the nitro boat.

So, what you're saying is I will need to buy $400 worth of batteries to be able to get nitro boat type run time with a FE?

[v-spec]

That would depend on if you change your mind about buying Chinese stuff. You can pick up some pretty nice turnigy 4s packs for about $75 each.

[D&D]

I have a Mean Machine cat (same bottom as yours) with a New 1515 1Y, Castle Hydra 180, and Turnigy Lipos 4S2P 5000mah @ 35C in a standard inboard configuration and I run well over five minugtes. The boat runs 57mph and I've only hit the preset voltage limiter once and I had run over 4 miles.

[D&D]

Just for explanation a "minugtes" is slightly more than a "minute" - so that is quite impressive!

[Fluid]

I have run the Aeromarine MeanMachine on 4S for years. Speeds are usually in the high 40s/low 50s, but run time is under 5 minutes...

Your challenge is the combination of speed and run time. Balancing these is a challenge, although 35-40 mph with 10 minutes run time will probably be doable. To be successful you'll need to minimize amp draw while maximizing watts (power). The easiest way to do that is by using higher voltage - 6S instead of 4S.

Ten minutes of safe run time on 10,000 mAh of battery capacity means an average amp draw of 48 amps. Using 4S this means only 700 watts, barely enough for your targeted speed. On 6S, the total watts is closer to 1000, and 35+ mph is attainable with that power level as long as the drive system is reasonably efficient.

The motor? If you insist on "US" made then Neu is about the only game in town. The problem now is matching the motor to the prop. The OB unit you have uses a threaded propeller - very few choices available and all are plastic props. Plastic is okay - except it is not as efficient as metal. The GRP2327.42 is the most appropriate size (45mm would be better) with a pitch of 2.6". The approximate motor Kv (rpm/volt) you'll need is 1200 to 1300. The Neu 1521/1.5Y is closest at 1050. This motor may or may not fit under the motor cowling. If I were you I'd not limit myself to Neu motors. I love them and use them in most of my FE boats, but you need a Kv rating that they don't supply except in a motor which is too long for the housing. Consider running without the housing, cutting out the top, or making a new taller one.

For an ESC things are a little easier. The Castle Hydra 120LV is borderline for 6S but at the lower amp draw you will use compared to what many here want it should work well. The 180HV will allow you to grow to higher power later. Cell 'brand' is a crap shoot, but regardless you'll want two 6S/5000 mAh packs with a discharge rating of at least 30C, wired in parallel.

What some fail to remember is that your speed goal is lower than most of us target. If you wanted to run 50-60 mph then I'd say no way for ten minutes of run time. But 35-40 mph should be attainable at ~50 amps draw. How you drive will also determine run time. An average of 48 amps means some running at 100 + amps and some at less. Lots of WOT acceleration from a slow speed sucks up a lot of current. Steady high speeds means high rpm and lower current draws - translating into longer run times.

To me the biggest impediment to your goal is the choice of OB. I had one of the older Graupner units (with gear drive) and it was not very efficient. The new one is doubtless better, but no OB is as efficient as an inboard, and being limited by a very small choice of props doesn't help you achieve your goals. I'm not saying you cannot do it, you should try but consider compromises. Let us know what we can to to help.



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[Fluid]

Are you in the Houston area? I'd love to come out and watch some racing if so. I'm only about 2 hours from Houston.

John it would be great if you could come over some time. We run twice a month in Katy on the west side - it takes me an hour to drive there from Humble. We have some members who have driven down from Dallas on occasion - 4-1/2 hours one way! You'd be more than welcome.

We normally run on the first and third Saturdays starting around 10AM unless there is an out-of-town race. We did cancel yesterday due to the heat advisory and lack of a place to cool down. I am assuming we'll be running on the 21st. Check out our website here: http://www.hotmbc.net


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[forescott]

Bringing this back to the top. Any and all advice is greatly appreciated. Would like to see as many different ideas as possible before I make my selections.

1515 / 6s?

1512 / 4s?

KV?

Starting props?

FYI, the outboard has the same motor mounting pattern as inboard mounts (25mm mount screw spacing, adapts to 5mm motor shafts) and has enough room under the cowl for a motor that's about 2" dia X 2.7" L max, including cooling jacket. The cavitation plate on the lower end will clear props with a max dia of about 42mm (1.65").

Thanks!

Which 1515 are tou speaking of? the 2200kv is more suited for 4s. I would be a little concerned with the ability of the ouboard drive line being able to hold up to the torque of the neu, since it was designed around a brushed motor. I think a 540 can is better suited and will give you plenty of speed. Also keep the cost down.

[T-Man]

Thanks for the input, guys. Good info!

Actually, forescott, the Graupner 820 outboard was designed for a brushless motor. It even says "brushless" on the side of the cowling. It has the same flex drive you'd use in an inboard stuffing box setup, only shorter. There really is no difference except that there will be more weight hanging off the rear of the boat. I can accommodate that, though.

To clear up the China thing... I don't necessarily have to have US-made components. In fact, it's virtually impossible to get everything US-made. I just don't like buying things from China... and it really has little to do with quality issues either. I have no problem with stuff made in most anywhere else, but there are certain countries of origin I do have a problem with my money going to. I have political and philosophical reasons for this that I don't want to get into, but trust me, I have very good reasons. I know it is probably next to impossible to get any electronics without Chinese made parts, and I accept that. But, I want as little content made in China as possible, and I'm willing to pay more to get that. If I have no choice, I have no choice.

[T-Man]

Which 1515 are tou speaking of? the 2200kv is more suited for 4s.

I don't know. That's among the many questions I have. I was going by the motor/ battery/ prop chart posted on this forum for the 1515/ 6s or 1512/ 4s recommendations.

[T-Man]

I have run the Aeromarine MeanMachine on 4S for years. Speeds are usually in the high 40s/low 50s, but run time is under 5 minutes...

Your challenge is the combination of speed and run time. Balancing these is a challenge, although 35-40 mph with 10 minutes run time will probably be doable. To be successful you'll need to minimize amp draw while maximizing watts (power). The easiest way to do that is by using higher voltage - 6S instead of 4S.

Ten minutes of safe run time on 10,000 mAh of battery capacity means an average amp draw of 48 amps. Using 4S this means only 700 watts, barely enough for your targeted speed. On 6S, the total watts is closer to 1000, and 35+ mph is attainable with that power level as long as the drive system is reasonably efficient.

The motor? If you insist on "US" made then Neu is about the only game in town. The problem now is matching the motor to the prop. The OB unit you have uses a threaded propeller - very few choices available and all are plastic props. Plastic is okay - except it is not as efficient as metal. The GRP2327.42 is the most appropriate size (45mm would be better) with a pitch of 2.6". The approximate motor Kv (rpm/volt) you'll need is 1200 to 1300. The Neu 1521/1.5Y is closest at 1050. This motor may or may not fit under the motor cowling. If I were you I'd not limit myself to Neu motors. I love them and use them in most of my FE boats, but you need a Kv rating that they don't supply except in a motor which is too long for the housing. Consider running without the housing, cutting out the top, or making a new taller one.

For an ESC things are a little easier. The Castle Hydra 120LV is borderline for 6S but at the lower amp draw you will use compared to what many here want it should work well. The 180HV will allow you to grow to higher power later. Cell 'brand' is a crap shoot, but regardless you'll want two 6S/5000 mAh packs with a discharge rating of at least 30C, wired in parallel.

What some fail to remember is that your speed goal is lower than most of us target. If you wanted to run 50-60 mph then I'd say no way for ten minutes of run time. But 35-40 mph should be attainable at ~50 amps draw. How you drive will also determine run time. An average of 48 amps means some running at 100 + amps and some at less. Lots of WOT acceleration from a slow speed sucks up a lot of current. Steady high speeds means high rpm and lower current draws - translating into longer run times.

To me the biggest impediment to your goal is the choice of OB. I had one of the older Graupner units (with gear drive) and it was not very efficient. The new one is doubtless better, but no OB is as efficient as an inboard, and being limited by a very small choice of props doesn't help you achieve your goals. I'm not saying you cannot do it, you should try but consider compromises. Let us know what we can to to help.



.

Very good information, Fluid!

Keep in mind that I won't be using the 4mm threaded props. I have a 4mm - 3/16" adapter w/ drive dog that threads onto the 4mm prop shaft and allows me to use props for 3/16" shafts, so I don't have the prop limitations you mention. I can use any prop up to about 42mm dia (which is how much clearance I have under the cavitation plate), maybe a bit larger.

I understand the tradeoffs with the O/B, however, this particular one has the flex cable drive, not the geared lower unit. It has very little rotational resistance. The shorter flex cable length vs a typical inboard setup should compensate some for the slightly increased resistance of the greater bend in the cable. The dynamics involved are virtually identical to an inboard setup. The motor couples directly to the flex cable, which runs in a teflon tube inside an aluminum housing. It should be very stable and durable. The only difference I see in how the motor will be setup vs. an inboard is motor location at the rear of the transom rather than inside the hull, but I can move my batt packs further forward to balance out the CG. I just like the appearance and "bolt on" simplicity of the O/B.

The Neu 1512 will definitely fit inside the O/B cowl. The 1515 will be close, but I'm not as certain about it fitting. Can I run the 2 6S 5000 MAH battery setup with the 1512? There is a 2Y 1400 KV model of this motor. If not and it will work, which KV rating should I choose? Any other motor recommendations?

I'm not absolutely dead set on achieving 10 min of run time; but I would certainly like more than 5 min. If I could get even 7 min., I'd be o.k. with that. I'm not looking for 55 mph. 40 would be fine with me.

Thanks again for your advice!

[Fluid]

The reality is: no matter what we think a good OB should do compared to a good IB, the IB always wins in both FE and nitro, and usually by a good margin. Reasons include excessive cable angle, drag from the thick lower unit, etc. Reality bites. The difference is less in a sport setup though.

I stand by my 6s recommendation for longer run times, but a 1512 is marginal since the Kv is really a bit too high. A Feigao 540/14XL will work well, but it's not US-made or designed. A Hacker 14XL is a higher quality motor, but I'm not sure it is worth the substantially higher price over the Feigao. The 1512/2Y might work, but it will draw higher amps and shorten run time. But - it is more efficient than the Feigao so higher speeds are probable.

It's good that you can use decent metal props, that helps by several mph. Figure on x442 or x642 props for this hull depending on the motor. IME the MM works better with props over 40 mm.


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[BHChieftain]

No offense but i don't think you are going to be running your boat with NEU motor and 6s for 5 minutes let alone 10 minutes. If you do get 5 minutes out of it I don't think it's going to last very long no matter what country the parts are made in.

Everyone who gets into FE boating comes in wanting 10 minutes run time but it's just not going to happen. And if you think you will just put around partial throttle going slower to get more runtime you'll just burn it down quicker. Most of us run 2-3 minutes max and things can still heat up in a hurry in that short time.

I'd probably pick up the proboat bj26 motor and esc and maybe you will get 5 minutes out of that setup though I'd still cut it short and be safe.

I have a Neu 1515 1.5Y (1500kv) on my 29" hull and have been really impressed with this motor. On 4S I just CANNOT get the motor hot, even with props that are so large that I get so much prop walking that forces me to back off on the throttle. On 4S 5400 mah I'm getting 6.5minutes at about 45mph on an x447 or x646 prop. I am sure the boat will hit mid 50's on 6S with a smaller prop.

To get 10min runtime, you'll need a setup that runs really cool-- maybe a 1515 on 4S (with a larger prop), and run some packs in parallel.

Chief