I'm designing a rubber band plane to give out to my nieces and nephews using a laser cutter- much more simple than this but I need to understand how to balance the plane initially- it'll take a lot of revisions no doubt to get it all right but I think this Tutorial will help me minimize how much material I waste in the design process. Thanks for this straight to the point video! I'll sub this :D
It was way out . Fixed with a couple of dollars stuck on the front. My tail was dropping, then doing a sharp turn and crash. So many thanks for this very simple method.
Adding weight to the front or rear of the plane is fine for IC engine equipped planes. But for electrics it's usually a matter of moving the battery. Rearranging weight in other words is almost always better than adding weight. But with IC models, rearranging the weight isn't usually an option unless you want to redo the build so servos, etc are more forward or aft. With electrics, moving weight, i.e. the battery, is usually an option.
I hang my planes from a screw-eye set in a basement rafter and use a plumb-bob. Plumb-bob will point to center of gravity of the airplane. Especially useful on a low-wing plane. Also, you can keep the plane hanging there while you adjust the center of gravity by shifting things around or adding weights. And yes, I aim for the manufacturer's recommended CG location, and also slightly nose heavy.
I have been flying RC aircraft since 1970 and have always marked the CG under the thickest part of the wing at the fuselage as my starting point. I usually like my nose to end up pointing down around 5 degrees. This was done so that if you actually stalled the plane, it was easier to recover from. This technique has never failed in 53 years of flying. Some planes did require some minor variation usually by no more that 1/4 inch plus or minus.
An oldie but still a goodie, Gerry. I come here every time I build a new model and follow your tutorial. BTW, you need to get back on FB even though you're retired. Later light winds and smooth landings.
thanks gerry, Ive got 20 plus year old model airplane news magazines that I still refure to.. I throw away the other mags but never a model airplane news mag. Ill try your balance method. thanks again...bob the builder
How are you Jerry? Tony from Warehouse Hobbies. Great video I learned a lot. Been designing and flying some electric planes since selling my boat division. Nice to have found you still at it, I will give you a shout soon and we can catch up.
Or just read the print. You can feel the structure point when you put your fingers under the wing and your close 1/3 back from leading edge. I hang it from the prop and tail wheel as well before i cover it. You would be surprised sometimes how far off it is side to side.
The general rule of thumb is the CG is approximately one -third the distance aft of the leading edge of the wing but........ that ONLY applies to straight wing aircraft - not a swept wing! To be as accurate as possible I recommend anyone serious about modeling purchase a balance machine from Great Lakes. I use mine all the time and It's never left me down. Of course at the field the old tried-and-true holding at each wingtip to see what the model does works but it's not real accurate. Just so you know.
Every airplane is different. But. Usually on a straight standard wing. a good general starting point is at the thickest part of the airfoil near the fuselage. Then adjust for your personal flying comfort from there.
Hi Gerry! Would you happen to anything about up-scaling a model aircraft to a full scale version, that one could climb aboard and fly? I want to design and build my own wing-in-ground effect craft. I think I could muddle past creating a working prototype model, but would the aerodynamic characteristics be the same for a full-sized version ? I'm curious that perhaps the air molecules act upon a small plane differently than they do a large plane. Perhaps this is why you see a B-52 model plane with a 4' wingspan, leap off the ground after only a 10' take off roll. Let me know your thoughts. I'm dying to learn more from someone who knows more that I do. Thanks! Dan
Airplane should balance slightly NOSE LOW, not level! It's always best to have a slightly nose heavy model for its maiden flight than completely level or tail heavy. Trust me, I know from 60+ years of model flying.
@@jonnylee5000, you trust correctly. I have spent a lifetime 40+ years as a professional pilot (airline and corporate) so I know a thing or two about how airplanes fly! Trust me when I tell you that ALL aircraft fly better in a "slightly" nose heavy configuration as opposed to being tail heavy. They have better overall stability. Aircraft controls function more efficiently when an airplane is perfectly balanced at its CG, or slightly nose heavy. Landing in any wind velocity is more successful especially in the lateral axis since extremes in either nose heavy or tail heavy configuration don't work out well. Too nose heavy results in the aircraft running out of (aft) elevator control during landing resulting in damage to the nose gear and/or propeller. Tail heavy configuration causes elevator movements to result in abrupt pitch changes at altitude and,during landing, porpoising, over controlling, or even worse - stalling. I hope this makes sense to you. Trust me, it works better having a "slightly" nose heavy model compared to one that's tail heavy.
@@williamhoenstine5057 As a heavy aircraft avionics technician, this makes 100% sense in regard to actual aircraft. The much higher power that an RC plane or Drone has compared to it's weight is what I was wondering about. I don't have any experience in flying drones, so I'm trying to absorb as much as I can. Thanks!
@@jonnylee5000 the same principles apply to model aircraft as they do to full scale aircraft except for the fact that we don't have "scale air" to fly in. There in lies a lot of the problems most new modelers learn the hard way! Add that to a improperly balanced and/or trimmed airplane - disaster is almost assured. I don't have any experience with quad powered drones but I do with single and multi-rotor full-scale helicopters. They ALL fly much easier if the operator takes the time to learn how to balance their model! Always "slightly" nose low/heavy! This is of primary importance - I can't emphasize it enough. Having a model fly on its maiden flight with control surfaces that move wildly up and down will almost always result in a crash (over controlling). Add to that windy conditions and disaster is guaranteed! Control movements (elevator & ailerons) that are set in accordance with what the manufacturer recommends is extremely important. Almost all model airplane crashes I've had myself and/or those of others most often resulted from one of the two factors I just described not being properly attended to.
@@jonnylee5000 Try making it slightly tail heavy and watch what happens on your first flight! It won't be pretty but if you're lucky enough to get the model back safely, you'll see my point! Every airplane I've ever built and flown has worked marvelously in a slightly nose heavy attitude.
For most biplanes I've seen, the top wing is about 25% of the chord forward of the lower wing. So the CG usually ends up at the LE of the lower wing. That would put it at the front edge of a CG range, good enough for a maiden flight. After that, you can adjust as necessary. For floats, determine the CG without floats first. Then see what the floats do to it and adjust weight to correct for the difference. To adjust means to move weight first, then add or subtract if needed.
If the wings are exactly one on top of the other I think this method would work. However, the Waco SRE has two different sized wings, both in length and chord, and the wings are staggered. Very difficult! You would have to look at the print.
what about the BATTERY ? Do you do the fingertip test AFTER you put the battery in place ? If you do it without the battery in place then should you line up the battery so it balances with 1/2 to the left and 1/2 to the right of the COG ?
I see more planes crashed by experienced RC fliers simply because the controls are reversed. They go through all the trouble to build a beautiful balsa plane that took all winter ,only to watch the plane invert upon takeoff and slam into the ground. You can actually see them rushing to get the plane on the flight line. You never see them stand behind the plane and operate the controls. Yeah, what a shame!
It is a very good idea to balance the wing by itself. If it has dihedral, turn it upside down and balance it. It should be able to compensate for small right to left unbalanced conditions of the fuselage since the greater weights are near the center of the fuselage.
My first large scale piper J-3 I decided to take up before I understood the concept of CG. I figured since the motor and tank were up front I’d put the flight pack and receiver towards the back... It was like watching a drunk chicken try to fly.... Part of this hobby is the feeling of heartbreak as you pick up the shrapnel from your yard....
A very common and unfortunate condition that many NEW modelers experience especially those who DON'T read the instruction manual prior to their 1st flight attempt (who does anymore?) nor had advice from an experienced flyer. It's a great way to watch several hundred dollars crash into little pieces!
Whatever you do... don't use this method of balancing an aircraft with any other type of wing except a straight wing as shown (even though this is still a poor example of how to ascertain the CG of a plane in general). That is, by ascertaining a CG of a plane by pure measurement, on all of the different aircraft wing types which are now available, will not produce desired results as implied, ie. Delta wings, swept wings, etc.
@@2891michaelk You balance a plane so that it stabilizes with the CG under the wing. High wings will stabilize with in an upright position. Flip it upside down and it will flip over back to an upright position if you place it on 2 points. A low wing will stabilize upside down. The CG is above the wing when it's upright. It will want to flip over when placed on 2 points so that the CG is now under the wing. How you place the airplane is for ease of balancing, nothing else. If the wing has anhedral on a high wing, or dihedral on a low wing, you have to experiment for how the plane wants to stabilize.
That might be the right spot for that airplane, It's certainly not right for all planes. I have many planes and they vary from plane to plane. This method will, in my opinion, lead to many planes being nose heavy. While this is safer than tail heavy, to tell people that this will correctly balance whatever plane they have is not helpful.
@@Jazzman-bj9fq You can search them up online or download an app. The app I have is airmodel calculator. This is for fpv wings but there are more complicated calculators for delta wings such as eCalc www.ecalc.ch/cgcalc.php
@@JF-cl6cj Ok nice, I'll check that out. You've found it to be pretty accurate and reliable? What I mean is that using that app, you haven't had a situation where you flew and the CG was crazy and way off?
@@retro440 Sounds like you have a plan that works for you. So long as the aircraft that's ready for flight is in the configuration we're discussing - all should go a planed.
This only works for bog standard air frames. Any difference in geometry or e.g. lift producing horizontal stabiliser this story goes out the window. In other words: read the damn manual. If you design your own air frame some more knowledge is required to determine the correct CG.
Yeah, I stopped watching after he placed a piece of paper in the wing. Zero way to get accurate cg with whatever he’s trying. Different planes, different sized batteries, wings may be further forward or backward. This won’t work.
This is a poor overview of how to balance a plane. There needs to be at least a little more detail. Anybody with experience with training knows speaking in generalizations like this to people who have no clue how to do it is dangerous. (gee my plane seems sluggish I'll just jam my battery all the way back) Should have mentioned checking the manual/PDF/threads for the PROPER CG. Should have mentioned that this is a general overview and that some planes are more important than others to be ACCURATE.
I agree. Find the correct CG and balance the airplane according to the manual. I thought this seemed a bit complicated with the paper folding and markings. It really is not as complicated as the video makes it.
Case in point today. On the field someone had a brand new plane and we did not know the CG and could not find it. I could tell him that the spot he thought was CG was well far back of 25 to 33 percent. It would have been quicker to do this method than all the searching. Setting at 25 % will be fine and work it back on the next flight if need be.
