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Advice needed re:setting up the innards for secure flying.

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Old 02-14-2015, 12:39 AM
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Pete B.
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Default Advice needed re:setting up the innards for secure flying.

Hi Sal, I'm at the stage in a scratch Skyraider 1:8 build where I need to seriously start considering the electrical install. This is a fully sheeted,(and will be glassed), plane of about all in 6-8lbs weight.My "bits" tally so far is:-SERVOS..E=Savox SC0252mg,,,R= JR NES-591,,,Flps & Ail's=Futaba S3152's(4 of) ,Rx=Spek AR610 and Tx is a new DX6. The MOTOR is an Energy 50/30 brushless outrunner turning a 15/8 prop.run through a Energy JP Sbec ProB,85a brushless ESC . The prop can be up to 18/10 using different lipo sizes. As a relative newby, what specifically I need help with is info. about a wiring diag. on how to power the servos separately to preserve the RX power.?...plus any observations re: this collection you may have. Apologise for the length of this mail but listing all the items gives you a better chance of helping me.Many thnks, Pete.B.
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Old 02-14-2015, 02:58 AM
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That's a pretty good weight for a 70 inch plus warbird fully sheeted and glassed. Going to make a lot of guys envious. Retracts? How much you figure all up flying weight is it going to be?

Dennis
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Old 02-14-2015, 03:12 AM
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Talking Advice needed on setting up the innards.

Dennis, Don't you know we are all eternal optimists?? In truth, that weight was just a guess but I've gone with a fixed U/C.......I know, I know, the warbird purists are shaking their heads ...but in my defence , I am a newby and the less problems I have thrown at me, the more likely I am to complete and maiden.besides, our strip can be a little "bumpy" despite all the brest efforts to smooth it out.! LOL! The next one is another story however........Pete.
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Old 02-14-2015, 08:19 AM
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Quote:
Originally Posted by Pete B. View Post
Dennis, Don't you know we are all eternal optimists?? In truth, that weight was just a guess but I've gone with a fixed U/C.......I know, I know, the warbird purists are shaking their heads ...but in my defence , I am a newby and the less problems I have thrown at me, the more likely I am to complete and maiden.besides, our strip can be a little "bumpy" despite all the brest efforts to smooth it out.! LOL! The next one is another story however........Pete.
Don't let the so called experts talk you out of or into thing unless your convinced it’s for the better. Nothing wrong with fixed gear on a war bird even the purists have probably had one or two when they first started. In this day and age I'm just pleased you’re building something instead of the quick fix of an ARF.

You’re going to get a lot of experts with all kinds of suggestions for motor/esc and battery selections. Lots of different opinions. My personal experience is that if a similar plane size and weight flies very well I would like to start with the same pitch and diameter prop turning at the same RPM. This should get me close to what I would like to see my model do.

Start by figuring out the number of cells you need to get that rpm. Is it within the limits allowed by that motor? Size or capacity of the battery for testing is not critical at this time. I have on occasion put two packs in series to get the cell count where I wanted it to be. I will size the battery for run time later. When you place packs together the cell capacities must be the same. If not you risk damaging cells even a fire.

This is where a meter to measure the draw in amps is invaluable. I have a Watt Meter only because it was the only one available when I purchased it. Others including Hobby King sell versions that are very reasonable. These go between the battery and esc via plugs you will have to solder in place to match the battery and esc.

If you can build a test stand, or mount the motor to a piece of wood and assemble the receiver, esc, battery, meter, motor and prop. Run it on the test stand and notice the draw and check the rpm with a prop tachometer. If the draw is too high or near the upper end of what is suggested for this motor esc combination you will have to make some compromises. Reduce the diameter of the prop, reduce the pitch of the prop or reduce the cell count of the battery pack. All of these will result in a reduced performance. You have to decide if it will be enough to fly the model. If the internal combustion model spends most of its time flying around at half throttle with no problem you may indeed be able to compromise. If not then you may have to rethink your motor esc combination.

If the draw is low for this combination then you may be able to increase performance by increasing cell count for more rpm, increase in pitch for more speed or increase in diameter for a more scale like prop and higher tractive effort. Change only one thing at a time and retest watching the draw and temperature of the esc and motor.

When you have what you feel is the right combination charge the batteries fully and with the low voltage cut off set run the combination the on the test stand wide open until it either cuts out or the battery pack gets to hot. Note the length of the run Battery capacity is simply the same as size of fuel tank so roughly if a 2300 mA battery gives a 6 minute run and you would like to fly for 12 to 15 then you would expect to need at least a 6000 mA pack if you run near full throttle for the whole flight. Lower throttle settings will extend flight times.

Now you know the battery pack size you can size the area inside the model to accommodate the pack. The more air you allow to pass by the motor/esc and battery the better.

This method works for sizing your equipment if you have a known comparison of the type of model you are trying to build. There are many other ways to calculate the sizing of your electrical components but it can be complicated and intimidating I leave that to the others who are more expert in the theory.


I hope this helps
Dennis

Last edited by Propworn; 02-14-2015 at 04:32 PM.
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Old 02-15-2015, 02:09 AM
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Dennis, Many thnks for the comprehensive reply. My "newbyism"...(new word), means that I never even thought about working out what physical area my batts would need and , of course, their effect on the CofG. I haven't got a tacho but someone in my Club will have I'm sure. Thanks for pointing me in the right direction, Pete.
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Old 03-03-2015, 08:37 PM
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Please note that there is no expert SAL.

It is noted in the forum that this is a dead forum and you should not post here.

Glad you found Dennis to answer you but please avoid this sub forum in the future.
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Old 01-22-2017, 01:41 PM
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Aeajr,Sorry I've been so long but have been fighting brain cancer for some time now. However, the reason I'm replying to you is to ask you to explain your comment. Did I post my request in the wrong section ?....and what does " SAL" stand for ?Rgds,Pete.
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Old 01-22-2017, 02:46 PM
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As it says in the beginning of the forum, the guy named Sal, has not been active on this forum for years. I have tried to get them to close this forum for a long time but it seems they can't.

Please post your question in one of the other forums.
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Old 01-22-2017, 03:52 PM
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Hi, Well I.m enlightened by your explanation ...except....to my knowledge it was I that started this question in 14th of Feb. 2015, not someone called Sal so I guess my option is to go to another "club"See ya, Pete.
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Old 01-22-2017, 04:08 PM
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Pete,

The forum you posted in is titled "Ask The Expert Sal". So you posted in a form where Sal was to answer the questions. What I am trying to explain is there is no more Sal. He is no longer active on the forum. Better to post your question in a different part of RCUniverse.
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Old 01-22-2017, 04:29 PM
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AH !.... now I understand....my bad DOH!!! will do as requested and thanks,Rgds, Pete.
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