I'm about to build a Builtright Sakitumi - E, and want to use a Power 25 for motivation on 4 S. Looks like the 1000kv would be the best for this, or the 870? I notice they ( Eflite) don't list them as good for over 4 S. If you're using one on a 46 size stunter I would appreciate your thoughts and suggestions. Prop, amp draw,Lipo size, etc. I'll be using an FM-9 and a Phoenix 60 esc, settings that you've used for those would help also. Thanks in advance!!

The 1000kV will probably be better with four cells, but IMHO you can safely ignore their 4-cell limit and go to five if you need it with the 870.

How much does a Sakitume weigh? At 40 ounces I get around 2500mAh for a 4-cell pack, and 2000mAh for a 5-cell.  Energy needs go up with weight, and the numbers are just starting figures.

I believe the Eflight power 25 comes in two versions, the 870KV and the 1250KV ( which is for EF-1 Pylon racing)
the 870 is a solid choice for a 4S setup, those who have tried it on 5S I recall were not that pleased , I think Mike Haverly did this and said the 5S wasnt the best option?
the 1250 KV is way wrong for us, it is designed to turn an APC 8x8 prop at full throttle for 1:30 minutes..

The 1000kV will probably be better with four cells, but IMHO you can safely ignore their 4-cell limit and go to five if you need it with the 870.

How much does a Sakitume weigh? At 40 ounces I get around 2500mAh for a 4-cell pack, and 2000mAh for a 5-cell.  Energy needs go up with weight, and the numbers are just starting figures.

If I'm lucky it will be about 40 oz. What plane/prop are you using it with, and how long a flight are you getting on 2500mah? I am well versed with electrics, but real world experience trumps all...

If I'm lucky it will be about 40 oz. What plane/prop are you using it with, and how long a flight are you getting on 2500mah? I am well versed with electrics, but real world experience trumps all...

Oops -- I forgot my disclaimer again.  I just take what's in "list your setup" and distill it down to some handy rules.  I'm just a circuit designer who flies slime.

I'm thoroughly confused now? What info are you distilling, if you don't have the amp draw, prop size, or any of the important data that is all part of the stew?

If you have flight duration and the amount of charge used, then you have the average current draw.  Many of the "List your setup" setups list these.

If you don't have the amount of charge used, then the batteries used give you at least an upper limit on current draw.

Note that I didn't say a @#%& thing about prop size -- that's also in the "list your setup" thread -- mostly you should figure on starting with a pitch that makes for a pitch speed about the same as or a bit higher than the speed calculated from your desired lap time (because if there were such a thing as "true pitch" then it'd be higher than most prop's listed pitch).  You should also figure on trying out a bunch of different props, or repitching what you have until you're happy.

You know Tim, I already know about all the things you are saying, except the "list your setup" thread. Hell, if I had found one of those I wouldn't be here. Since you have found one for an Eflite Power 25 1000kv on 4s, would you please link me to it?

Bill,
I sense some angst on your part,
please keep in mind that Tim was trying to help you.
did you note where I suggested contacting Bob Hunt? if you read, you would see that I commented he uses that setup and he has done setups for Classic sized airplanes as well. So he will surely have some answers for you.

also, as Tim noted, he is a controls engineer who understands the electric stuff, but he flies GLOW IC which he also said.

I also told you the setup I used on my airplane with the eflight 25,, in all honesty, I wonder if a 40 ounce airframe would not do better with an eflight 15, but I dont fly the smaller stuff, mine is all aproaching 700 square inches and weights half again what you are lookign for
smile, its toy airplanes

No, no angst, sorry if I came across like that. I was just looking for someone's real experience, and instead got a treatise on theory which to me came across as somewhat smartass. I spent hours going through all the Eflite Power 25 setups on list your setup, and only one said the kv he was using, and it wasn't the same as mine. This is an unusual forum. Everyone is so nice, but there is always that one thread where it seems that oneupsmanship is the objective.
I ALWAYS appreciate people trying to help, 

I certainly didn't mean to be smartass -- just helpful.  There's a lot of folks on the list that are hesitant to make decisions when either electrons or math are involved; since math & electrons are my business, I try to help where I can.

I'm not trying to pretend to be something I'm not -- what I am is a guy with lots of industry experience; I've done lots of motor sizing exercises for various machines both as a paid exercise and for RC planes.  What I'm not is a guy who flies electric CL -- to date my stunt planes have all been delightfully smelly and noisy.  You should take anything anybody says about this stuff with a grain of salt, sized to what you know about that person -- size the one you use with me accordingly.

Mark has direct experience with the 870kV motor and 4S, so move my "might work" to "will work", because you have someone who's done it.  For salt-grain-sizing, Mark's somewhere around the bottom of our local Expert pack and rising fast (it's hard to tell because he can't seem to wait until his second flight to crash*), and he's got considerable experience with RC airplane racing.  If I'm contemplating using motor "A" and Mark says "that won't work, use motor B", I'll probably try motor "A" out I'm both curious and contrary, but I'll build in structure so that I can swap in motor "B" with minimal pain, because he's Mark.

Based on my experience in industry, what I know, and what Mark said, I'd say that if the only thing you can get is a 1000kV you should be fine on four cells.  But based on what Mark's saying about his experience with the 870kV motor, it sounds like it's not a bad choice at all.

* Hi Mark.

Tim,, by the way, thanks for not laughing when the carcas of my airplane stopped at your feet,,

you have to admit, it was a pretty awesome slide job though,, that was almost the most gentle crash I ever had,, still dont know what actually happened,,

Bill
Bob Hunt is a great guy, this is in his wheel house for motor selection, like I said, I went through the 4S .25 setup and right on to the 6S eflight 32 setup,, I know my system worked ( 4S) but I just moved on

I tried a 5S 2700mAh set up for an Eflite 25 (870 Kv) on a 64 OZ profile.  The reason was I only owned 5S batteries.  It worked OK but got things warmer than I thought they should be.  I suspect the reason was having to operate on the low end of the available RPM's.  I switched to a lower rated Kv, 770 and stuck with the 5S batteries, again because of what I had that was available.  For the weight I haul around with the airplane it would need 4S 3000mAh batteries.

FYI I still fly the airplane and consistently use about 73% of the available battery @ 5 min. 20 flight time.  Like Tim says, weight is the big driver here.