Electriceddie

Hi All,

I have a Flight Balance Theory Question for the Guru's:

Been in and out of racing over the years, and as the years go by you tend to forget stuff.

Anyway, in lateral balancing of the plane there were times that we use to place by means of taping a Quater to under the wing tip to flight to balance it better as it pulls thru the turns.

Now if memory serves me correctly, if the plane is rolled to it's side as it would upon entering a left turn and starts to slide downward a bit, you would then add a little weight to under the high wing (Hence, the Quater Trick). The opposite would be then be true, if it climbs a bit in the turn, then you would add weight to under the low wing.

The plane of course has been horizontally balanced, CG and laterally. Which is good. I think the theory was, if the plane slides down a bit the addition of the Quater gives a bit added weight to make the upper wing fly slower thru the turn. Thus making the plane not slide anymore. Of course the weight could end up being a little more or less then an actual Quater. But I remember for the most part the Quarter did a pretty good job, when needed. (LOL)


Am I correct with this logic?


Thanks Guys, I look foward to your replies.

Super Splatter

My noodle says it the weight of the side mounted engine with the jug and the muffler hanging off one side like that is why you would put a coin on the opposite wing.

But my noodle has been deep fried once or twice..

kane

Eddie,

You are correct in your logic. Be careful though because a nose heavy plane will also tuck it's nose at number one.

Sometimes more than one quarter is required.

Dan

Jimnie

So is the opposite true as well, that is a tailheavy model will climb through the turn? I have added weight to the inside wing but the model tends to keep climbing through the turns. It has gotten better.
Jmnie

Jim Duda

Like Dan said, sometimes it takes more than one quarter! We used FIVE on this Polecat...

djlyon

I use dollar coins so that if the sh*t happens it will still be worth at least a dollar.

Denis

Ed Smith

Forget lateral balancing when stationary. Forget the effect of the weight of a side mounted engine. The trimming in the turn is performed in flight, as is balance and control surface throws.

Going through the turn the airplane is up on knife edge with full up elevator. Centrifugal force of the turn will cause the heavy wing to swing outwards. If it is the high wing the airplane is no longer on knife edge, the up elevator will induce a climb. The converse is true for the low wing. This time however the airplane is over knife edge heading for inverted flight. The up elevator now causes a dive.

The coin placement is to prevent any swing during the knife edge turn. All other trim and balancing shouild have been carried out before this feature.

Ed S

rmenke

My Feedback: (13)

EEddie:

As you can see, there are differences within the old guys group, guess I should say "experienced". Ussen real old guys consider this as dialing in, and next to the engine, the most important thing you can do. Set up correctly, most birds will "grove" around the pylons without tucking in or up. Either one will cost you the race, and maby the bird. Getting the control surface movemnts correct are also critical. Do not kiss off DR and expo as unnecessary, its a great tool. You are going in the right direction, keep it on track. If you ever get a chance to fly one of the top pilots airplanes, jump in. Your gonna find one sweet flyer as a general rule. These guys are on top for a reason, and its not all pilot ability, its overall setup and pilot ability. A well setup arframe will frequently beat a superior pilots average airframe. The more you learn, the more you realize you's got a lot of learning to do yet. Had the chance to fly Chip Hyde's bird about 2 years ago. My reaction (flawed) was"no wonder he looks like such a outstanding pilot" Yes, the thing was that far above my stuff, average VS wonderful. Now I work a lot more on setup with all my birds, 3D and racing. My motto, "take from the best and beat the rest". Works. ENJOY

DHG

My Feedback: (7)

Eddie,

The following is reprinted without permission from Dub Jett's web site, www.jettengineering.com ... it's chapter 3 of the "Crap Trap" series in his Technical Library:

"Rules for trimming a racer:

"1. Call the manufacturer and find out the best c.g. and throws and use them!!!!!!. If you don’t balance the airplane, then please skip to the next page. (maybe later I will do a crap trap on balancing)

"2. Set the low rate throws at slightly less than recommended and the high rate at 20% more. That’s 20% more than the low rate! E.g., if the low rate is “40”, then the high rate should be “48”, not “60”. (1.2 times the low rate). Take the time to do this. It will save you a crash later.

"3. Fly the first flight rich, very rich, so you can get the centers of the trims without crashing. Center the elevator and ailerons first, obviously. Then try to fly the course.

"4. When you make your first few turns around the course take note of several things: How are the rates? Try the high rates (remember they are 20% higher) You can get two shots at the throws this way and use this info to set your final throws. Second, watch the airplane thru the turns. Is it yawing? Is the nose high or low? A few clicks of the rudder will take the yaw out. (do not watch the smoke trail, it will confuse you)

"5. With all three trimmed, there is one important thing left, which is really the subject of the Crap Trap. What are the wings doing during the turn? Think of the fuse as an arrow. When you enter the turn at pylon 1 it is pointed directly away from, regardless of the bank of the wings, right? When it finishes the turn, it should be point directly back to you, regardless of the bank of the wings. If not, then the airplane is either rolling up, or down. If up, then add weight to the left wing. If down (seldom needed), then add to the right tip. Do not change the Rudder!!!!!!!! Do not change the rudder!!!!!! Do not change the rudder!!!!! Get the message? You have already trimmed the rudder for zero yaw, then why would you want to race a yawed aircraft? It doesn’t matter if you under roll, or over roll, the “arrow” will always return to you, if you have the wing weight right. If not, it will never return to you, and you will continue to fight it around the course. Sometimes you have to add a bunch of weight, like ¾ oz. It depends. Sometimes I add some aileron mixing, but that causes adverse yaw in the turns, so be careful.

"This is essentially a balance problem. The engine is on the outside. When you pull g’s, you are multiplying your imbalance by 25-50 times. This causes the airplane to roll right or left during the high-g turn. A little weight on the tip goes a long way. Watch the spinner. It should be point right back to you every time!!!

"In summary: Balance the airplane to specs. Trim the airplane, and set the rates. Add weight to the wing tip until the airplane does not roll out or into the turn. Don’t use rudder to control a balance problem.

"Dub"

daven

My Feedback: (1)

I skip the weight and mix aileron to elevator, start with a small amount (5%) and adjust as needed. I have a couple planes with quarters on them, but do it all with mixing now. Rarely do I need that much, works good.

jaka

Hi!
I always balance (axial) my airplanes be it racers or sport airplanes
Then if the airplane dives slightly in a sharp pylon turn ...it's noseheavy and I move the battery slightly backward to make the plane more tailheavy...untill the plane goes thru the turn without any problems...just floats!!! I never ever ad lead to a plane if possible.
The secret is to make plane as tailheavy as possible without sacrifing control.
Simple as that. That way you can minimise elevator trow.
This has worked for me for 30 years.