General SPADET BUILD WITH ELECTRIC

[Returningrcr]

I am nearly completed building the Spadtothebone.org and about. I have made many revisions. Probably the biggest change I made is going to electric v.s. nitro. I chose to use the motor from the Timber X Night that I so successfully trashed. That motor is a BL10 and says it is 900Kv. I have several 2300Ma 4 cell batteries I have used with that motor. The 4 millimeter coroplast used for the build has a 66-inch wingspan, 51 inches long and 5.5 to 6 pounds. Now I am hoping this motor will propel this machine with a 10X8 prop instead of the 13X4 that was too long. Another big question I have is what size servos to use on the ailerons, elevator and rudder? I am going to use 2 servos for the big ailerons and the Spektrum 2300 Ma 4 c batteries along with the spektrum receiver that came with the Timber X night.
Any help with this challenge (at least for me), would be appreciated!

 

[RandyDSok]

There are a lot of questions and information that you are simply not providing for anyone to assist you with.

First is the obvious lack of a specific model ... you mentioned the website Spadtothebone.org which has a lot of various ( the term crap ton comes to mind ) models listed. None of the ones listed in the .15 ci motor size ( which is the approx equivalant to what a Eflight BL-10 would be used in if not a little small for those even ) were of a 66 inch wingspan.

You did list the approx build weight which is something you can use to start to select proper sized components for. So this is where I'd point that you start your research in. Look at existing electric models that have that approximate wingspan, type of wing ( top, mid or low wing ), if it's a trainer, sport or 3D type etc... and look at what they are recommending for components. The more models you look at for the specs of the type of aircraft you are planning... the better and you can then intelligently select possible components that may be comparable to the model you are making.

I suspect the BL 900kv motor ( which I can find no actual specs showing wattages, amp ratings, voltages and recommended props for ) can probably be used on around a 40-48" sized model at the max if it's a trainer type. I may even be over estimating the specs for use at those sizes so don't completely go by my guess for that motor even. I just know it's likely well undersized for the project you mention at the wingspan and weight you listed.

 

[Returningrcr]

There are a lot of questions and information that you are simply not providing for anyone to assist you with.

First is the obvious lack of a specific model ... you mentioned the website Spadtothebone.org which has a lot of various ( the term crap ton comes to mind ) models listed. None of the ones listed in the .15 ci motor size ( which is the approx equivalant to what a Eflight BL-10 would be used in if not a little small for those even ) were of a 66 inch wingspan.

You did list the approx build weight which is something you can use to start to select proper sized components for. So this is where I'd point that you start your research in. Look at existing electric models that have that approximate wingspan, type of wing ( top, mid or low wing ), if it's a trainer, sport or 3D type etc... and look at what they are recommending for components. The more models you look at for the specs of the type of aircraft you are planning... the better and you can then intelligently select possible components that may be comparable to the model you are making.

I suspect the BL 900kv motor ( which I can find no actual specs showing wattages, amp ratings, voltages and recommended props for ) can probably be used on around a 40-48" sized model at the max if it's a trainer type. I may even be over estimating the specs for use at those sizes so don't completely go by my guess for that motor even. I just know it's likely well undersized for the project you mention at the wingspan and weight you listed.

Thank you for the info. The "General" tab subject says it is the Spadet. It's final weight is 6.5# That indicates it should be around 600 watts minimum. It is a coroplast trainer with a flat bottom wing, 5" of dihedral, wingspan of 5.5' and 51" long. With the different motor I installed with a Spektrum 80A ESC, the motor get's really warm after a minute full throttle using a3S 30C lipo battery. Not sure how hot or warm the motor should get as I have a comparable at this point in time. I tested several different props using a watt/power meter and could get up to 1,100 watts with a 12 X 8 prop. After a minute full throttle the motor was just about to hot to touch. I was gifted the motor and all it said on it was "Horizon Hobby" and the dude who gave me the motor had in his writing AT-6 written on tape attached to it. All I know is the motor is heavier and deeper than the BL10 that I had on it. The BL10 came from the Timber X night and was coupled with an 80A ESC. All this electric stuff is new to me and a real challenge to grasp, especially when there is no information on the motor.
Thanks for any help anyone my provide!

 

[LooseNut]

If the motor is off the E-Flite AT-6 (most likely), the manual says it's a BL-15/950kv. The recommended Battery is a 3s/2200-3000/30c, and the prop is a 12x8. The normal weight of the model is 60 - 62 grams (so about 5 lbs) with a 57 inch wingspan.
So it sounds like to me that it "should work". The AT-6 is probably more of a Sport plane and the motor probably puts it in the scale performance range. Not too much in the way of "Specs" for the actual E-Flite motors, they play them close to the chest for some reason.
Getting to hot to touch from running full blast static on the ground is no surprise, just like the Nitro motors you are used to they expect some airflow to keep them cooled.
Welcome to the world of Electric motors. Your 80 Amp ESC will do the job since E-Flite only used a 40 Amp.
Learn as you go, but remember that the prop will bite you, and far quicker than a Nitro motor. I always make sure that I set up a Throttle Cutoff and use it. Take the prop off when working on the bench.
Have fun.

 

[RandyDSok]

I never run at full throttle for any length of time... I typically try to keep it at most around 75% and keep full throttle to only pull out of trouble or briefly at most.

 

[Returningrcr]

If the motor is off the E-Flite AT-6 (most likely), the manual says it's a BL-15/950kv. The recommended Battery is a 3s/2200-3000/30c, and the prop is a 12x8. The normal weight of the model is 60 - 62 grams (so about 5 lbs) with a 57 inch wingspan.
So it sounds like to me that it "should work". The AT-6 is probably more of a Sport plane and the motor probably puts it in the scale performance range. Not too much in the way of "Specs" for the actual E-Flite motors, they play them close to the chest for some reason.
Getting to hot to touch from running full blast static on the ground is no surprise, just like the Nitro motors you are used to they expect some airflow to keep them cooled.
Welcome to the world of Electric motors. Your 80 Amp ESC will do the job since E-Flite only used a 40 Amp.
Learn as you go, but remember that the prop will bite you, and far quicker than a Nitro motor. I always make sure that I set up a Throttle Cutoff and use it. Take the prop off when working on the bench.
Have fun.

Thank you Loosenut for all the info. I will bench test with the watt/power meter using the 3s 2200 30C and see what I get. I am curious to see what the output is with the 12X8 prop. I always make sure I set the throttle cut 1st thing in a setup and all loose items are away and secure. Normally always run all setups without prop but to use watt meter it's a different situation in the shop.
Have a Great Day!

 

[LooseNut]

There is lots of info good/bad (typical internet) out there, but, if you Google "Watt Flyer" you should be able to find a fellow that wrote quite a few articles on sizing and motors in general. Great info for learning.
I have an Excel file I use based on another I found on the web that does some basic calculations for me to get in the ball park, and I also have a thrust stand for motor testing that I've done quite a bit of work with. I can tell you the no 2 identical sized brands are alike.
I took a couple pictures of what I input from the info you gave for the plane. I didn't have your Wing Cord, so I did a TLAR on the Wing Area.
The pics below;
First one shows input area for the plane (green), as well as the prop you mentioned. The red areas are the Calcs made from those entries.
Second one shows the output and expected run time on the Battery.
It's actually all on one page, just had to scroll for the shots.

 

[LooseNut]

You will notice in the chart the "Target RPM" is 9225 rpm, the 3s on the 950Kv would be, 950kv * 11.1v = 10545rpm. So you are in the ball park for what you are looking for.
As Randy mentioned, you aren't going to be wide open the whole flight, so the battery time will extend by the lower throttle settings, and I'd definitely stay with the 80A ESC. The chart shows 65A input and you always want to be sized larger than your max draw for safety.

 

[Returningrcr]

You will notice in the chart the "Target RPM" is 9225 rpm, the 3s on the 950Kv would be, 950kv * 11.1v = 10545rpm. So you are in the ball park for what you are looking for.
As Randy mentioned, you aren't going to be wide open the whole flight, so the battery time will extend by the lower throttle settings, and I'd definitely stay with the 80A ESC. The chart shows 65A input and you always want to be sized larger than your max draw for safety.

Awesome info, LooseNut! Thank you so much!

 

[LooseNut]

Quite welcome!

 

[RandyDSok]

The power efficiency of any electronic device, whether we are talking about motors or computer CPU's etc, will vary somewhat but can still be generalized and be close enough to keep in mind. They all will have their best efficiency in or around the 60-70 % area... As you pass whatever the best efficiency point of the device you are talking about, the amount of power that device needs increases substantially. After you pass that point, the extra energy to get just a little more power, is converted to heat instead of actual power you will see. This is also why I seldom go past the 75% point... while I could get a little more power, most of it will be just making heat. Heat is an electronic components worst enemy.

On most quality motor specs... you'll see the maximum power listed. This isn't the amount of power the motor can run at constantly but only for a few moments, this is often called the burst power limit. I've seen very few that actually list the recommended constant power limit. That limit is dependent on the air flow, which is variable enough and why you won't see it listed very often. I think all specs should be listed with the kv, max burst power ( watts ) limit, voltage ranges ( hence number of battery cells ) and amp limits. It's also nice if they can give expected power ( wattages ) for a selection of props but I understand why they wouldn't since each use case can vary. It's my opinion that if a company doesn't list the most basic specs, that is a product that you should keep away from since you can't calculate approximate safe usage limits.

 

[LooseNut]

I think all specs should be listed with the kv, max burst power ( watts ) limit, voltage ranges ( hence number of battery cells ) and amp limits.

I couldn't agree more. I've tested quite a few motors, ESC's, and recommended props over the last few years. Smoked a few too, on purpose just to get a measure.
A quality motor will have good specs that align with the product. That said, I've tested some that the specs weren't worth the time to read them.
I can say that one of the nicest motors with specs that align and are reasonably priced are the Leopard series.
Of the Cheap motors, the Suppo do match their specs, but the quality of parts are lacking and longevity becomes an issue.
A must! Getting rid of the sticker on the bell is a must, log the motor info in the plane or a card file. The Sticker causes an off balance that will create vibration and reduce bearing life.