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.
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.
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.
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.
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.
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
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.
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.
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 ?
@@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?
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.
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.
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.
@@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.
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!
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!
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.
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.
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.
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.
Very informative vid
Thanks
Brian
London
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.
That helped me heaps. Thks 👍
This is fantastic, i have struggled for weeks, as my glider is old with No instructions / manual,
Thanks for your Tutorials 👍🇬🇧
Yeee , love it I'm now going to check thank yo
Thank you so much i have problems with my plane being unbalanced and now I can finally fly it good
What a great tip, thank you.
It makes more sense to place the marking on the underside of the wing, because you have to hold the wing there to balance it.
Since the 25% & 33 % marks from leading edge on the underside will be too aft the measure should be taken on the top side due to the corda.
P Sblad then how are you supposed to see where to hold the wing when balancing? I have balanced hundreds of models measuring from underneath.
Extend the marks on top of wing to the wing tips and balance plane by supporting at these points
@@psblad2667 morning my love
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.
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.
Great.
I do this with a ruler, but indeed with papers it is much easier.
Congratulations.
I m planning to make a glider (without engine) . Wing span 30 fts. Wing area 150sq. Fts. Does the same calculations will apply for it?
Thank you!
Very useful could never understand how it was done but now I do
Ok very good. That is the dynamic balance , but where is the statistical balance ? Need the second video .
This is all fine for a constant cord but I'd feel better if you had also included a treatise on both a swept wing and a tappered one.
Great video!! This also applies to full scale aircraft.
ALL AIRCRAFT
Instructions unclear. 747 stuck on foot.
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.
its good but how to find CG for helli and rc 52
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
That is asking for trouble... only works on specific NACA Airfoils... always refer to the manufactures cg limits.
My general and simple rule is to use the wing spar as the CG. This may not work for exotic wings.
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.
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.
Lateral balancing is very important especially in sailplanes.
So - you do include the ailerons (or flap area) as part of your wing measurement ?
The ailerons and/or flaps are a part of the wing and they have weight, so they have to be included
Why you dont say how to fold paper to 3 part?
The manual that is supplied with the model should show the correct CG range.Sometimes it varies with different size batteries.
that was helpful
Do you balance a botom wing plane the same way?
I saw you marked the wing on top but put your fingers under the wing,how do you Mark under the wing? Do you use the same paper under the wing?
Generally speaking, the bottom of the wing is flat, so the distance across the top of the wing will be greater..
Does the same method work for a bi plane and what about a plane equipped with floats?? Appreciate your response.
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 ?
If you're flying an electric powered model of some sort, always do you final balance calculation in a "ready for flight" condition.
@@williamhoenstine5057 thanks, all my planes are electric and that's how I've been doing the test
Obviously the plane can not fly without the battery. Therefore, put the battery in first and then test.
No point marking on top of the wing ! Mark it UNDERNEATH the wing !
he is a kolbi man..
Hello, this method with folding paper sheet will work same on delta wing? how you think?
I'm wondering the same thing. I doubt this technique would work reliably for swept wing jets.
I don't think it will but I just use a cg calculator for fpv wings
@@JF-cl6cj Where did you get the cg calculator? Or is it a formula?
@@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?
What about the balence for right and left
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.
anyway thanks, i am going to use this method on my ultralight which i am building, it will be around 180 lbs, wish me Good luck , thanks.
Have you completed your ultralight ?
Balance with battery inside right?
Yes
Balance each time a battery goes in.
w a charged battery, not empty... jk 😆
Yes you balance with all the gear installed and an empty fuel tank..
Now what if you have a flying wing or a plane like an f-16 type of wing?
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.
why do some balance upright and some upside down
@@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.
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.
I'll trust your 60+ years, but how come you want it slightly nose heavy?
@@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.
what about fuel planes do balance it the same way with fuel or not
Allways without fuel - empty tank.
@@shimanosv9143 Always WITH FUEL, just like you plan to launch it on its 1st flight.
@@williamhoenstine5057 I have always read empty tank. That way, it will be slightly nose heavy when ready for flight.
@@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.
Dude....what am I, stupid or something?? How did you fold the 2nd piece of paper into thirds to the mark??
just fold it lightly and guess until you've got it right, then make hard folds.
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!
What plane is this?
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!
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.
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.
Dont you
Duhhhh!
You want a slight nose down attitude.
You call that easy
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.
Joey duncan. Funny, you missed the whole point that a manual is not always the only way to find it.
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.
How do you think the manufacturers find their mark?
Great point!!!!
I will have to give it a second look today.
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.