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Old Jul 27, 2014, 05:00 AM
Registered User
France, Centre, Roinville
Joined Sep 2013
6 Posts
Question
Boosting my radian pro to get more climb rate

Hi All ,

I'm trying to use my radian pro for fpv , and with the original configuration , the plane seems not to like the extra weight of the fpv stuff ,
Gopro 2
Ezosd
Gps tracker
Immersion RC tx
2200 mah battery replacement
i got also some CG problems , but resolved that my putting the maximum on the wing , on the CG ( i m planning also to build a bigger tail with carbon or fiber glass, to have more surface for the elevator , because with the extra stuff the elevator is suffering )

So for that i bought a new motor
Turnigy Aerodrive SK3 - 3536-1050kv
bigger propellers :
Aeronaut Cam-Carbon 10x8"
I experienced a little improvement but it's not enough .
Just note that as the nose is fragile , and so is the hole foamy radian , i reenforced all the parts with fiber glass tape and that's added extra weight , but my radian pro is very robust now.
So my question is what to do to get the difficult equation to work :
Power for climbing easily + stability (CG) + extra weight (due to FPV + battery)
Any suggestions is welcome .

Thank you all.
Ryan.
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Old Jul 28, 2014, 04:11 AM
Registered User
United States, MA, Waltham
Joined Dec 2001
6,938 Posts
Bigger model or lighter gear, I'm afraid. Or else check if the prop and motor and battery match up, see: http://brantuas.com/ezcalc/dma1.asp You may have to make up a "custom" motor to match yours. You'll need the resistance in addition to the kv. How much does all this gear weigh?

Unless you have an awful lot of garbage hanging out in the breeze, if your elevator control is not working well, it's probably a forward c.g. , linkage that's getting a bit loose (check that staple attaching pushrod housing to fuselage), or a stab that's too flexible. If it was the original Radian, I'd throw in fuselage flex as a factor. If you're going to build a bigger tail, you might as well use balsa. It's not as if the Radian is some high tech model in the first place. But I doubt you need it if your installation is relatively clean.

BTW, you can have too much pitch stability if you move the c.g. forward too much. It will be harder to suppress the pitching oscillations. (not departures, oscillations. I think there's a better word but I don't recall it right now.)

What happens if you let the model climb at a shallower angle? The Radians I've seen using a 10X8 climb at steep angles, but they don't have so much weight.
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Old Jul 28, 2014, 07:46 PM
Old Prop Buster
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United States, CA, Grass Valley
Joined Dec 2009
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How many amps are pulling? Bigger prop to you get close to the max amps, I would think you could use a 12 inch prop?
Gary
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Old Jul 29, 2014, 12:33 PM
Proud member of LISF and ESL
LI, New York, USA
Joined Mar 2003
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First, climb is based on power to weight ratio and I don't see that you have posted the all up weight of the glider and the equipment. The stock radian is about 30 ounces and the motor pulls about 17 amps for about 180 watts, round number. So you are talking a little over 90 watts/pound. Not a bad ratio for a glider.

Let's say you added 2 pounds of stuff to the Radian. now we are talking under 50 watts/pound and the climb is going to be pretty poor. By changing the prop you can get that motor up to about 22 amps or about 220 watts. But if the all up is about 4 pounds that is still 55 watts per pound. Not great. And I don't' think I would take a Radian over about 250 watts. The structure is not made for it without some reinforcement.

A more powerful motor will help but the motor mount will not likely take the extra power very well and the nose is not going to do so well either. I have seen the nose twisted off a Radian by a big motor.

Second is CG. If you are mounting all that stuff in the front your CG is going to be way out of whack which would explain why your elevator is "suffering. You don't need a bigger elevator you need a better balanced glider. Are you keeping the CG where it should be?

Some photos would help.

Knowing so little about what you have, anything I offer is a wild guess. but it sounds like you need a bigger aircraft.

Consider the Multiplex Cularis
http://www3.towerhobbies.com/cgi-bin...&I=LXSBS8&P=ML
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Old Jul 30, 2014, 02:37 PM
Registered User
France, Centre, Roinville
Joined Sep 2013
6 Posts
Hi All, sorry for responding late , beeing busy lastday,
thank you for your replies , i 'll try to give further information :
For the weight :
Glider : 980
Motor :110
Gopro with case:120 g
tx + ezosd : 100g
battery : 178 g
fiber glass tape : 100g
We can say total weight is about 1700 g (about 60 ounce) with wires
aeajr when you say "the motor pulls about 17 amps for about 180 watts" how did you calculate that , is it the maximum power or power at half throttle, because the technical specs of the motor says the power is about 505 w and the maximum current is about 34 A,
note that i'm using a 40A hobbyking ESC, 10x8 folding propellers , as you suggest i'll try to 12x6 folding props and see if it adds something, i dont know the maximum propellers size i can put with my configuration.
AS i said i reenforced the nose with fiber glass tape , so that the plastic motor mount is attached to the tape and not the foamy nose directly , this way the power is distributed and not concentrated on the nose.
for CG , i'm balancing the glider after putting all the fpv stuff, i put two pens on wings at 70 mm back from the leading edge of the wing as mentionned on the manual of the radian .
Others said that 72 mm is better , i don't know if it makes difference , i prefered to respect the manual instructions.
after balancing the glider is slightly nose heavy (a few mm) .
i v seen alreeady videos where persons al ready put all that stuff on radian pro , and going high , that makes me think it's possible. with only Gopro on board the glider is very stable and climbs correctly , but adding the rest of materials , complicates the things , i think i need to be more precise on CG.

Thanks again for your suggestions.
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Old Jul 30, 2014, 03:30 PM
Proud member of LISF and ESL
LI, New York, USA
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Quote:
Originally Posted by RyanFPV View Post
Hi All, sorry for responding late , beeing busy lastday,
thank you for your replies , i 'll try to give further information :
For the weight :
Glider : 980
Motor :110
Gopro with case:120 g
tx + ezosd : 100g
battery : 178 g
fiber glass tape : 100g
We can say total weight is about 1700 g (about 60 ounce) with wires
OK, 60 ounces so you have increased the WL of the Radian Pro by 66%. I don't think that will be a problem, just making note. She is not going to float along. You will have to fly faster than usual in order to stay in the air. When you glide you will have to glide faster than a standard Radian Pro. But I presume you know this.

Quote:
Originally Posted by RyanFPV View Post
aeajr when you say "the motor pulls about 17 amps for about 180 watts" how did you calculate that , is it the maximum power or power at half throttle, because the technical specs of the motor says the power is about 505 w and the maximum current is about 34 A,
note that i'm using a 40A hobbyking ESC, 10x8 folding propellers , as you suggest i'll try to 12x6 folding props and see if it adds something, i dont know the maximum propellers size i can put with my configuration.
I was talking about the stock motor, not your upgrade. I was just commenting on what could be done with the stock motor. My 10X8 prop comment was again with the stock motor. Not relevant to your new motor.

Are you using a 3S or 4S battery?

I have no experience with your upgraded motor or what prop to use. Looking at user posts on the HK site:

measurements with a APC 12 X 6 prop, 3 S 2200mAH LIPO : 360W ; 11V ; 32A

This looks like a good combo for 3S pack. - At 60 ounces and 360 watts you would be at 96 watts/pound which should be excellent.


If the max amps on the motor is 34 then the most you can get out of a 3S pack is about 390 watts +/-. To get to 500 watts you would need a 4S pack probably running something 10X8 maybe. or maybe an 11X6 would work.

I would always use a wattmeter to test the set-up. Remember that the actual amp/watts will be a little lower in the air due to prop "unloading".


Quote:
Originally Posted by RyanFPV View Post
AS i said i reenforced the nose with fiber glass tape , so that the plastic motor mount is attached to the tape and not the foamy nose directly , this way the power is distributed and not concentrated on the nose.
for CG , i'm balancing the glider after putting all the fpv stuff, i put two pens on wings at 70 mm back from the leading edge of the wing as mentionned on the manual of the radian .
Others said that 72 mm is better , i don't know if it makes difference , i prefered to respect the manual instructions.
after balancing the glider is slightly nose heavy (a few mm) .
70 mm is fine. This is no longer being flown as a glider so we are not concerned about finding lift or reading the air. You are using this as a powered platform with the motor running most of the time I presume. Once you fly it a bit I would recommend you try moving the CG back to 72 or even 74 mm in small increments just to see how it flies. Glider pilots often move the CG back from the manual's recommendation but that may not apply to your application.

Remember that a more rearward CG will make the elevator and rudder more effective. You seemed to feel the elevator was struggling with the load. That could be due to the forward CG.


Quote:
Originally Posted by RyanFPV View Post
i v seen alreeady videos where persons al ready put all that stuff on radian pro , and going high , that makes me think it's possible. with only Gopro on board the glider is very stable and climbs correctly , but adding the rest of materials , complicates the things , i think i need to be more precise on CG.

Thanks again for your suggestions.
Keep the info coming. I am sure you will be successful.
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