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Old Mar 02, 2011, 09:24 PM
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Titusville Fl
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Man i'm really having trouble finding the correct CG for my pro..I think i had it with my 1.6 battery. the 2.2 makes it real nose heavy, and i have to trim the plane up to keep it level going into the wind...then it either goes into a nose dive, or will porpoise. Tried a 1.3 which makes it VERY light....It kept going nose up into the wind, but was pretty easy to control. glided well down wind. The 1.6 had good balance of upwind and downwind flight. I'm thinkin a 1.8 would be best.


Ive been playing with the CG, and it seems 70mm is right along the front of the first spar in the wing right? The white tape you can feel where the cut is made, that appears to be about 73mm..give or take..
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Old Mar 02, 2011, 09:28 PM
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Quote:
Shultz,
Why would you build one up from parts rather than just buying one? Just curious.

Guys, should we tell Shultz the secret about the spar tube?
Well... it cost me just under $100 for all the parts shipped to my door... I have a Bunch of motors, ESC's, BEC's and servos on hand that are MUCH better quality than the PNP electronic's... make perfect sense too me


On a side note I should have searched the thread FIRST I won't even bother calling Horizon for the cheap fiberglass spar... they can keep it. If I can't find a 10mm OD 8mm ID tube at the kite shop I'll try Bass pro shops archery shop...maybe they will have something in the right Dia.

Thanks!

John
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Old Mar 02, 2011, 09:29 PM
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You know, I could have sworn that the original Radian used to list the wing tube as a separate piece. And for some reason, it was also listed as the ParkZone Extra 300 wing tube (PKZ5121). Maybe I'm imagining things.

I will make note that the wing tubes for the Radian and the Radian Pro are interchangeable. I've flown my Radian wing tube in my Radian with steel rods in it for ballast. Worked fine. The Pro wing tube is a different tube with thicker walls. Not sure if it is carbon fiber like the Radian, but it is definitely heavier and stiffer than the Radian wing tube. Haven't weighed it, but is noticeably heavier.

Hope that helps...

Andy
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Old Mar 02, 2011, 09:38 PM
Dixie Normious
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Quote:
Originally Posted by Sproket13 View Post
Ive been playing with the CG, and it seems 70mm is right along the front of the first spar in the wing right? The white tape you can feel where the cut is made, that appears to be about 73mm..give or take..
Sproket at that mark for me is 77mm. When you balance her before flight or just on the table. How does sit? Level/Abit of nose down/or tail down.

No matter were i set my CG to 70mm/77mm i always have a slight nose down


shultz the Stock Spar is not CF,but HH stated it was...Its Plaztic/FG. So im sure a 10mmCF Spar would be abit lighter etc...
Im not sure why the Spar is not included with the Wing. I guess another mystery. Like the metal housed Motor. If you want a Stock replacement Motor.you have to get the Plastic(Radain) motor.
While you are on the phone with them about the Spar,asked them about the motor too
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Old Mar 02, 2011, 10:00 PM
Drifting off the reservation..
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Quote:
Originally Posted by shultz View Post
Well... it cost me just under $100 for all the parts shipped to my door... I have a Bunch of motors, ESC's, BEC's and servos on hand that are MUCH better quality than the PNP electronic's... make perfect sense too me


On a side note I should have searched the thread FIRST I won't even bother calling Horizon for the cheap fiberglass spar... they can keep it. If I can't find a 10mm OD 8mm ID tube at the kite shop I'll try Bass pro shops archery shop...maybe they will have something in the right Dia.

Thanks!

John
Darn, you figured that one out quick!
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Old Mar 02, 2011, 10:38 PM
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Originally Posted by Eastcoast78 View Post
Sproket at that mark for me is 77mm. When you balance her before flight or just on the table. How does sit? Level/Abit of nose down/or tail down.

No matter were i set my CG to 70mm/77mm i always have a slight nose down
Mine sits pretty level, If yours is nose down i would look to see if your resting it on an even surface. But to be honest, what i use is just my finger nails..lol. nothing fancy yet, just getting stared but smart enough to figure most of this out for now
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Old Mar 02, 2011, 11:22 PM
Dixie Normious
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Originally Posted by Sproket13 View Post
Mine sits pretty level, If yours is nose down i would look to see if your resting it on an even surface. But to be honest, what i use is just my finger nails..lol. nothing fancy yet, just getting stared but smart enough to figure most of this out for now
Ok maybe i should of been abit more clearer. What i mean is i fly with a nose down manner to help with penetration. I make it nose down on my own doing. The CG is adjustable by moving the battery either forward or Aft within the CG range of the aircraft....Depending on the winds/conditions that day. CG still stays at the measurement. Battery shifts the cg either to the nose or too the Tail. It is fine tuning and does not take much to adjust. 5mm shift in your battery can do alot.
Like if its a 30km/h day a 1800mah with nose down attitude is great.
Verses a calm day!! I like using a lighter battery and either the CG(balance of the plane) neutral/level or even with a touch of tail down.
I like at least a 10degrees nose down normally. the Hands off /see what she does and fine tune with trim.

Fingers is all i do CG with aswell
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Old Mar 03, 2011, 12:46 AM
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Portland, OR
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Originally Posted by mgroves View Post
My manual notes the c/g at 70mm from leading edge...so you are indicating that the balance point it is back further, but then slide the battery forward to compensate...sounds strange or am i missing someting? Where did the 77mm come from?
77mm is a matter of flying preference - that is the point that seems to get the best l/d on my RP - I had to tape a qurter to the tail to get the CG back to that balance point ( and my battery is all the way back -3s 1350 pkz lipo)

Don
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Old Mar 03, 2011, 01:29 AM
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i so missed the boat on this,.. there are none due into Australia (from what I can find out [from MF here in Aussieland]) until April,.. they sound like the shizzle and from reading this thread not much, if any mods are required,.. I was put of by Parkzone after their first attempts at Aircraft,. but sounds like they are on the ball now,... can't wait!!
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Old Mar 03, 2011, 01:39 AM
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When I pieced my radian pro together from HH it didn't come with a spar either. I called customer support and they have no idea how to get one to me because there isn't a part number for it. I had to order a CF spar from goodwinds.com.
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Old Mar 03, 2011, 01:42 AM
Dixie Normious
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Originally Posted by donsinger1 View Post
77mm is a matter of flying preference - that is the point that seems to get the best l/d on my RP - I had to tape a qurter to the tail to get the CG back to that balance point ( and my battery is all the way back -3s 1350 pkz lipo)

Don
Interesting. Have you tried to balance her with the battery say 50-60% in the Slot? With out the added weight to the tail?
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Old Mar 03, 2011, 04:10 AM
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Originally Posted by Eastcoast78 View Post
Interesting. Have you tried to balance her with the battery say 50-60% in the Slot? With out the added weight to the tail?
Huh?

What will moving the battery forward and removing the tail weight accomplish aside from making the plane way too nose heavy?

I've got both Radian models and have never used the battery to adjust CG. The battery is always pushed into the slot as far as it can go. In fact both planes have weight taped to the tail to achieve a CG roughly 1/4 inch behind the manufacturers recommended CG.

I can't help thinking with all the talk of batteries half way out of the slot there's quite a few nose heavy Radians flying around. Unless you're counterbalancing a camera mounted behind the CG you really shouldn't need to shift ounces of weight forward to get a proper CG.

......Mike
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Old Mar 03, 2011, 07:18 AM
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MS_in_NY: "What will moving the battery forward and removing the tail weight accomplish aside from making the plane way too nose heavy?"

I think what Eastcoast78 is trying to suggest to you, is that this is a sailplane and any added weight effects efficiency and that in turn decreases duration. I believe he is correct.
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Old Mar 03, 2011, 07:56 AM
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Originally Posted by 1911tex View Post
MS_in_NY: "What will moving the battery forward and removing the tail weight accomplish aside from making the plane way too nose heavy?"

I think what Eastcoast78 is trying to suggest to you, is that this is a sailplane and any added weight effects efficiency and that in turn decreases duration. I believe he is correct.

Uh, no he's not, (he was replying to donsinger1 btw, not me). Not if he's suggesting donsinger1 can lose the tail weight, move the battery forward and keep the same CG.

If a Radian is balanced at the desired CG with battery fully inserted and weight on the tail, moving the battery forward and removing the tail weight WILL move the CG forward (probably alot). Thus making the plane nose heavier than it was before.

The only way possible to lose the tail weight and keep the same CG would be to install a smaller/lighter battery fully inserted into the slot.

.......Mike
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Old Mar 03, 2011, 08:50 AM
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cg and other confusions

I would imagine that the designer of the pro originally set the cg at the 77 mm mark. This point is about as far back as the cg can go and still have a controllable sailplane. I would also assume this is the max L/D point. This is where the factory places the recommended battery.Then after some testing and out of consideratrion for the newer pilots the cg was suggested at 70 mm. This gives a more contollable sailplane, but it requires moving the factory battery fwd until its almost out of its holder or add weight or get a heavier battery. That said the sailplane flies best at 77 mm. At that pount elevator trim should be almost zero. If its at zero the elevator creats less drag because its not offering much resistance to the horizontal airflow (drag).

Now if you move the cg forward You have to change the trim to pick the nose up or else fly faster both increases drag. A sailplanes in general terms has max L/D just above stall speed.

Now the Pro is light and doesnt penetrate well. There are a lot of people here and other threads that state on windy days " I move the battery forward (move the cg fwd)". This will help pentration but you will not stay up as long due to drag and if you do not change the trims it will not stay up as long either. The solution is to add weight as near the cg as possible. Some have the right idea by putting steel rods inside the wing tube. ASdding weight here does not require changing trims. The plane will fly as well with the weights as without and you greatly increase penetration. Weight here does not change the L/D (up to a point) Generally the higher the wind speed the more weight that needs to be added. L/D refers to how far forward a plane will fly for a given drop in altitude eg. 30:1 L/D means for every foot it drops in altitude it will fly 30 feet forward. Best L/D is the speed at which this 30:1 ratio occurs. Faster or slower than that speed will decrease this ratio. On purpose or not we try to fly at best L/D. (even in wind). How fast a sailplane flies is up to the pilot. If the wind is faster than the forward speed of the aircraft we have to fly faster by putting the nose down. We pay for this with a smaller L/D which means we are on the ground faster. If the wind is not faster than the best L/D speed then we can still fly the plane with at best L/D (dont forget to add glider speed to the windspeed)
See this link for non calculus explanation of how this stuff works.

http://flyingworld.dk/speed-polars.html
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