Hi there everybody

I need some help to understand a few things about propellers

I'm mounting a Suppo BL motor with an 40A ESC and 3s 1800mAh Lipo battery (20C)
on a 800gr (1.7 pounds) aerobatic plane, the BL has these specifics:

<font size="2">- 70g Outrunner
</font><font size="2"><font face="Arial, Helvetica, sans-serif">- Kv: 1100, Rm: 0.125, io: 1.0A, Poles: 14
</font>- Max amps: 18A for 60sec
</font>
Now ...i'venoticed, around the web , and using motocalc and similar software's, that the good choice of propeller is an Apc 10x5 or 11x6 ..... so i went in a shop and bought both
then locking the plane on my table and trying an 80 % thrust for less than 1 minute , i've noticed that with both props , the motor , the esc and batteries becomes quite hot ....
Why ???? what did I do wrong ???

Changing the prop with and old 7x5 APC after 8-9 minutes of 70-80% thrust , electronics is barely warm....
but of course the 7x5 has only a 600-700 max thrust , this won't allow me to do acro with my plane...
Instead mounting a 8x5 GWS i should have a max thrust of 988gr

Which propeller do you suggest ??

By your experience what could i do for it ???

Thanks in advance


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Propellor selection on an electric is a tad bit more critical than it is with glow.  But the selection process is about the same.  You have to make sure that you don't over prop it because you will quickly burn out either the motor or the ESC, or both. 

But, with that said, if you carefully select a range of propellors, based on wattage (which is based on weight and desired performance) and buy one of each.  Don't worry about having to many because if you are like most of us, you will have a good selection of props of various sizes before long and you won't have to go through this too often. 

But, what you have to do is select the prop you want to try, make sure it is within the range that won't over-burden the motor and esc, attach a wattmeter to the power path (Wattsup is a good one to  use, but I'm sure there are others) then run the motor up.  Check to make sure you are within the current/wattage ratings for your application, then put it up and fly it.  You will quickly see if you have the right combination for your airplane.</p>

I know that does not give you a specific, but you have an idea already as to what you want to do.  Now it becomes a trial and error process to select the right one for you.</p>

CGr</p>

Thanks CGr....

one more thing , what's the main difference between an APC and GWS, 'cause looking at some charts same props (pitch and diameter) gives two different thrust ??????
and most of the times the GWSseems more performant ..

be careful when doing static tests with motors and props.. some motors caution you not to run then for a given amount of time static!
eg hobby lobby little screamer! They run hot normally and are suppoed to unload in the air. after a flight they come down cool on the bench they get hot.
Just a thought so watch it!

I think i will use a 50% throttle for 10 seconds by slowly encreasing , if it gets hot , or it gets too warm i can break immediately
it's something thust must be done if you want to check the Amps with the gage , isn't it ???

hm Id check with the motor manufacuture, you might be able to push it more than that maybe even to full throttle... what i spoke of is just a general cautionarything and something that came with my little screamers motor, they warned not to static run it for more than a certain amount of time.. This may not be the case with all motors.. I'm not surehow safe a minute of run time is, 10 seconds might be ok,i think mine was up to 30 sec I cant quite remember but i've never had a watt meter so i've never static tested anything for more than 3 seconds. I'll be getting a watt meter soon (its on its way) I'd say check with the manufacture. As for me id for sure take it to full throttle get a reading and then back to off... and let it cool off a bit too. just my two cents.. maybe someone else can chime in with better advice

I propably will buy it very soon .... i think that when you start to tweak your planes it's a necessary tool

what about GWS props , what's the main difference between them and APC's ???

Thanks

hmm I've never used GWS props I've only ever used APC, maybe someone else can shine light on this issue. I can understand why you're crossed though. I remember when i wanted to know every thing and try everything too keep that enthusiasm it will take you pretty far! All i can say about your props though is to get one of each and try them out in the air see which you prefer. the real life test is the best judge! good luck

Ok , super testing on props next week , then i'll post a chart with the result

thanks a lot for now

How much does your plane weight with the current setup?

Given the specs you've stated your max draw is about 200 watts which indicates to me that your plane is under 2 lbs.

You should be able to get away with installing TWO of those 3S packs in parallel ( assuming there is space in the fuselage ) to effectively create a 3600mAh 11.1v 3S batter pack.

This will let the batteries run relatively COOL, and they will therefore last far longer.

You will also double run times.

In a very similiar plane but much heavier ( Super Sportster EP ), with an 1100 KV motor ( identical KV specs ) I run a 9x6 prop and two 2200mAh packs ( see my gallery ).

Performance is fantastic, but the motor I have is capable of much higher amperage and wattage ( 600 watts ).

In tests I pull about 29-32A at full throttle, and that is with a SMALLER prop than you are using!!!


The 11x6 prop is likely to burn your motor out as your motor is much lighter and smaller.

Your motor is attempting to spin at a max of 12,210 RPM's and your 11x6 or 10x5 prop is simply NOT going to let it!

( Remember Brushless motors are always trying to attain max RPM's, only the voltage pulse duration is modified to make them seem to slow down ).

An 7x6 to an 8x6 would be within the range for that motor!


It sounds like you want a bigger motor for that plane, but around the same KV rating or less.

thanks guys fro your reply and support.

Yesterday i went on field for an "on air" prop testing :

the weight is 720g
testing has been done on two props, 9x7.5 APC and 8x8 APC ( sorry opjose but my shop didn't have 7x6 and 8x6 but they'll arrive soon )

take off went fine and reached a good levelled flightat 40% ( for sure less then half stick) of full throttle , it happened that
the plane "on level flight" as soon a si give 1% - 2% throttle more , drastically tryies to goup vertically like if it has an elevator fulldown ( onTX)
by dropping down the throttle again at nearly half stick it levelled perfectly straight , is this a problem of weight or baricenter ????


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I'm only guessing, Sounds like you've got a lot of excess power on that plane lol and also you need to trim you're controls. Fly full throttle trim for level flight... I hope some one else chimes in