Number cells/Motor Kv/Prop Size/Hull Size

[ED66677]

when will this thread be STICKY?
I'm seing some newbies going away from this base, no good for them IMO!

[BassBoat88]

[QUOTE=ReddyWatts;44733]What about a spreadsheet to help users decide on a build?


"Updated" with Lipo and esc amp ratings. There are too many variables for this to be exact for all of the different hull and motor loads. Many setups will fall outside of this general data spreadsheet. Just hope this gives you a better understanding of FE for designing successful setups.

--hull size /--------Cells---------/ ----Motor Kv----- / -------Prop Size------/---Type ESC---/-BEC-/ESC Amp Rating

17”- 24” / 2s LiPo or 6 cell NiMh / 5500 -3200Kv / 30mm - 40mm Diam. / Low Voltage / Avail. / 120 amp

20"-27" / 3s LiPo or 8 cell NiMh / 3500-2500kv / 35mm – 42mm Diam. / Low Voltage / Avail. / 120 amp

24”-29” / 4s LiPo or 12 cell NiMh /2650-1600Kv /37mm - 46mm Diam. / Low Voltage / Avail~Disc / 120-240 amp

26”-32" / 6s LiPo or 18 cell NiMh /1800-1100Kv /40mm - 52mm Diam. / Low or High / Disc. / 120-180-240 amp

30"- 36" / 8s LiPo or 24 cell NiMh / 1350-800Kv /45mm – 55mm Diam. / High Voltage / N/A / 180-240 amp

34" - 42" / 10s LiPo or 30 cell NiMh / 1100-600Kv /47mm + Diameter / High Voltage / N/A / 180-240 amp

38" - 46" / 12s LiPo or 36 cell NiMh / 900-550Kv / 50mm + Diameter / High Voltage / N/A / 240 amp

Does this table also hold true for dual-drive setups?

[sailr]

Lots of talk about 3S lipos in here. Unfortunately, the dolts at IMPBA have deigned 3S lipos as non-existent, having 2S, 4S, etc. classes.

This is really stupid! There are so many RTR 3S lipo boats out there they are totally ignoring a segment of the market and eliminating newbies that would like to race!

[sailr]

this doesn't make any sense to me. Your spreadsheet says to use a 52mm diameter prop on a 4S 1800KV motor! NO WAY! You'll burn it up!

[sailr]

Typically 6S is 6S2P or two 6S packs in parallel. Two 3S in series will not yield enough mAh generally.

When you call for a 26 to 32 inch hull using 6 cell LiPo's, does that mean 2 packs with 3 LiPo's each. Thanks for the reply!

[ReddyWatts]

This was an on going project. I would update the chart as users gave suggestions. I have not been able to update any of this since it was moved to this section.

[Steven Vaccaro]

This was an on going project. I would update the chart as users gave suggestions. I have not been able to update any of this since it was moved to this section.

Readdy's right. I kinda put a strange hold on him when I started this area. I hope thats somewhat resolved now.

[Doug Smock]

Lots of talk about 3S lipos in here. Unfortunately, the dolts at IMPBA have deigned 3S lipos as non-existent, having 2S, 4S, etc. classes.

This is really stupid! There are so many RTR 3S lipo boats out there they are totally ignoring a segment of the market and eliminating newbies that would like to race!

Nevermind

[ryan_t888]

There appears to be a bit of information directly taken from what I had written on rcuniverse several months ago.

Here is a direct link to the original information.

http://www.rcuniverse.com/forum/m_7603257/tm.htm

Even with the information available, I still get one pm per week asking why my power system failed resulting in burned electronics. People still are choosing motors way outside the kv range listed and props that are far too large for the application. Most are new boaters trying discover FE, not trying to make a rocket on water.

My advice is somewhere it should be stressed that if one does not know which prop or motor to select for their application PM someone who can help out.

I have designed many excel spread sheets to calculated a starting prop diameter based on weight of motor, diameter, length, boat type, and kv. It is near impossible for them to work well for every combination. My point is, experience might be the best starting point for a new boater to selecting a power system.

Does this table also hold true for dual-drive setups?

In most cases yes it would also hold true for dual drive set ups.

this doesn't make any sense to me. Your spreadsheet says to use a 52mm diameter prop on a 4S 1800KV motor! NO WAY! You'll burn it up!

Not my spread sheet but I'll still chime in since it was not answered
4s 1800kv motor is a very vague description. You are missing so many other variables. For example If you had an 1800kv S can motor it would not be too happy on a 52mm prop. If you had an 1800 kv motor in a 1521 NEU size, it would handle it with absolutely no problem and would NOT burn up.

Ryan

[ReddyWatts]

Thanks for the idea and starting point for this spreadsheet. I have tried to stress that users start with the small props and work their way up to the desired setup. FE setups are not an exact science, there are just to many variables.

[Flying Scotsman]

[QUOTE=ryan_t888;86608]There appears to be a bit of information directly taken from what I had written on rcuniverse several months ago.

Here is a direct link to the original information.

http://www.rcuniverse.com/forum/m_7603257/tm.htm

Even with the information available, I still get one pm per week asking why my power system failed resulting in burned electronics. People still are choosing motors way outside the kv range listed and props that are far too large for the application. Most are new boaters trying discover FE, not trying to make a rocket on water.

My advice is somewhere it should be stressed that if one does not know which prop or motor to select for their application PM someone who can help out.

Response

The problem is rcuniverse is not a good source of info for FE boat information and as you state and my largest concern..newbies burning up their stuff with bogus information. Tell them to join OSE or RRR forums and even then have caution to some advise espicially on RTR boats from newbies

Douggie

[Anbjorn]

This is great info. However I cant realy make my decision as my boat is slightly in the larger end of the scale.
I have a home made 67" Epoxi V hull.
I originaly designed this hull for competition in 35cc gas class.
However I have run it with a Quickdraw 25cc HT engine. It runs great with this engine. It runs 58-59mph in light chop with a stock 7018/3 prop.
Rpm is apr. 16800rpm. Weight with fuel is 11 kg or 24 pounds.
With more prop testing and tweeking I am confident I can get it past 60.
The Quickdraw is only 7,3HP and I would think this boat will be alot faster with a big brushless system.
The hull weighs about 11 pounds empty. However I will make a lighter one for electric setup if I decide to try that. To come down to 9 pounds will be doable I think.
I was thinking that a Lehner 3080/5-7 a Hydra HV240 and 4 pc. 5000mAH 22.2V Kokam lipo packs, 2 in paralell and 2 in series might do the trick. Starting prop 6717/3
Any thoughts and advices?
Yeah and I want to go fast
Thanks
Anbjørn

[ReddyWatts]

Check this.

http://forums.offshoreelectrics.com/...ht=Lehner+3080

[Anbjorn]

I am not sure I got more enlightened. This was a lot smaller boat than mine.
Good acceleration but the speed did not impress me.
Will I have problems powering my boat into realy high speeds with brushless?
Anbjørn

[ReddyWatts]

Contact this guy with a private message, has lots of experience with large hulls and setups.

http://forums.offshoreelectrics.com/member.php?u=568