TampaRC

With R/C planes the CG is generally at 25%

Look at where the balance point is on these planes. Near or in front of the L/E. Why is this?

aspeed

It pulls out on the lines better, and is less sensitive.

Clean

The easiest way to check airplanes for their current CG that I have found is to hang the airplane in a sling. This method uses a sling made from a loop of some heavy 1/8" chord. My loop is made from a 14 foot piece of chord which makes a diameter of about 4.5 feet. You also need a plumb bob and I made mine from an extra piece of wooden dowel. For a suspension point you can use a nail in an exposed rafter or a plant hook in your ceiling anything that can withhold the weight of your plane. In my example I used a simple piece of chain that is hooked onto a ceiling fan. The Chord loop is wrapped around one part of the airplane, up through the chain suspension point and back down to another part of the plane. Here I have it wrapped around the nose of my F-22 foamy. It then goes through the chain and then wraps around the cutout before the elevators.

TampaRC

Where should the CG be on a conventional C/L airplane ?

aspeed

I start at 15% and adjust after flying. A stunt plane, and racing plane or speed plane will differ. Stunt planes will alter leadout rake and tip weight more precisely than a speed plane which just needs to be stable on the level.

aspeed

Double post. TV distraction.

Clean

11 to 19% MAC. If at all possible, follow the plans. Try looking up your plane for plans and see if they are not on there. Looks like you have a Skyray or Goldberg equivalent, can't remember the name. Put the CG at 15 percent and try it, wait, if you've not flow before, put it at 11. It won't be very active at all but nose heavy planes fly again, tail heavy planes don't.

do335a

Unpainted plane in pix is a Goldberg Wizard. Also called Lil Wizard.

cyclops2

Since most of my C L planes were scale kit jobs. I relied on the plan COG point. I readjusted it to allow a easy dead engine landing. House framing nails into the bottom of a profile was easy way to do it.

grotto2

My Feedback: (2)

Don't let Clean confuse you. He mixed up cord with chord, two entirely different concepts.

qazimoto

My Feedback: (1)

A good rule of thumb for a simple c/l model like the Wizard is to balance them on the front leadout for the first flight.

Tom Nied

Well what Clean is describing is a Vanessa CG Rig. One important omission is that you have to get the model hanging level, in that sling, then the plumb bob will point to the CG. It works well once you get used to wrestling with the lines to get it right. But only works if done correctly. http://www.rcuniverse.com/forum/tips...g-rig-how.html

bingo field

The Vanessa rig works. It doesn't take that long to try it.

init4fun

I always heard that saying as "Nose heavy flies poorly , tail heavy flies once"

This was always the standard when the actual CG was not available , and has never failed me yet , very good rule of thumb qazimoto .

Clean

What I was describing was a rig I saw when I was a member of the Topeka's Capital City RC club back pre 1980. I heard of all the sticks and bobbles of the "V" about 10-15 years ago and that's after. Loop of string hanging from the ceiling, hang the plane level, hang a plumb bob over it, there it is, simple as that. Again, I didn't invent the thing but there sure wasn't much more then that. When I built my first one I thought it would be cool to have it spaced out on a stick, which is kinda like the V, but in the end getting rid of the stick made it easier. Here's a link to my old website, the Northland Flyer although the first published date on the wayback machine is December 20th, 2000 this page is saved in March 2001 https://tinyurl.com/yb5xyan5
In any case, it does show you an example of balancing a plane, it just shows I used to use a stick. The stick is redundant. I swapped to two equal loops, found one large loop was easier to tie and manage. I lost my wood plumb and swapped to a 1/4 x 20 nut, found that wood one when I moved 3 years ago. Where it is now?
Why am I contentious? I don't know if it's that so much, two minds working on a similar idea can come up with similar answers. It's just that your average Vanessa is a bunch of extra crap you just don't need, including a senseless name. What does he call his scales, Bobs?
Trust me, you don't need anything but scraps to know exactly where the center of mass is on your plane, what you use to move that to the correct position is up to you.

But I have ideas on that too!
Clean

cyclops2

Paper covered wings ? A Index finger under each side of the wing Is the COG... weight.
With all controls in NEUTRAL. Toss the plane to get a steady, fast, slightly nose down glide. I move the wing AOA as needed. Or the horizontal tail surface. Which ever is easier.
I always start with 0 degrees of angle on wing or tail.
I also balance for level wings. Some of the foam P B Ys were very heavy on the left wing side. A stall turned into a steep, left cartwheel crash.

qazimoto

My Feedback: (1)

Stuart Sherlock did a nice analysis of the situation on c/l speed and racing models quite a few years ago: Your simple trainer is more like one of these than a stunt model. Which may well have the ideal cg position at 25%.

It's published here:

Control Line: Speed model C/G position

qazimoto

My Feedback: (1)

Mate, you're talking control line models here. The wings and tail plane aren't relocatable and you don't test glide them.

Clean

Oh I do. I didn't accidentally let go of the handle, that was a "Test Glide".

cyclops2

I did the C L test glide on my VECO full stunt Chief 65 years ago. Memory ,pain & drugs do take a toll after snow shoveling. Better today With Ibuprofin.

Real test glides are rare on any C L plan. I added 2 inches to the inside wing panel during construction.

init4fun

My most recent C/L craziness needed almost 3 ounces of lead in the tail to balance at the model's advertised CG (which BTW is right between the front leadout and the center of the bellcrank's mounting point) . It's kinda small , and so the Enya .19 is kinda big for it , , , so it oughta fly like the literal "Bat out of Hell"

cyclops2

That rear portion is light compared to forward section. Add in a full tank ? The COG point will move around between take off & run dry, glide time. I always COG balance with the empty tank. To make a landing in wind easier.
I like to build, modify & repair models. Because I am a TERRIBLE pilot.

Tom Nied

init4fun, looking at your last photo I noticed the Enya .19 and metal spinner. Now I am open to be corrected here, but I think the Enya's were a bit on the heavy side and that metal spinner only works against you, even if it might be alloy. Switch to an aluminum spinner nut , move the engine back, and you would need less weight in the tail. John B., what do you think?

049flyer

My Feedback: (18)

init4fun

Thank You for the responses guys

Tom is right about the weight distribution , moving the engine back and loosing the aluminum spinner would have resulted in needing less tailweight . The plane came to me already put together (yard sale purchase) and was finished badly , I jokingly called it "Ugly Betty" when it first got here . I stripped off all the old covering and recovered it and noted that not only was it built badly , it had never been properly balanced , it was WAY too nose heavy and had no weight in the outboard wing to counterbalance the lines . Since the opening in the fuselage for the engine was only as deep as it was manufactured , the engine went as far back as it could without removing more wood from behind the engine and as to the aluminum spinner , I have had a couple of plastic ones fail while running so I always use the metal ones on every engine powered plane I own , right up to my Saito 270 twin . I know I could have used a spinner nut but this was more of a "run what ya got" rebuild and I was determined to use what I had kicking around the shop (including the red and yellow Monokote) .

As to training , I figure one of two things are gonna happen here ;

I flew C/L all through the 1960s and 1970s , up to and including my trusty Sterling Ringmaster and a .45 stallion powered Nobler , untill R/C became affordable enough for the common man . In that time I toyed around with some old vacuum tube "tailwagger" escapement equipped models , basically somewhat steerable free flight models that the TX may or may not signal the rudder , depending on mood and atmospheric conditions . I had gotten to the point that I could reliably fly the AMA C/L stunt pattern and was a member of a fairly large C/L club when I bought my first "real" R/C set and from then on I never had a C/L handle in my hand again . Fast forward almost 50 years and a good friend and flying buddy bought this C/L plane for me at a yard sale because I had casually mentioned one time in conversation how I'd love to see if I can still fly C/L , and so this project was born .

I figure this will go one of two ways , It'll be like they say about riding a bicycle , once you learn you never forget and I'll fly that plane like I always did , OR , my extended time away from C/L flying will result in a smoking hole in the ground . When it finally does have it's day it the field , I'll post up the results good or bad here in this thread