Originally posted by joe yap
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Simple method to find CG. (interesting method)
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Permit me to add my thoughts to his discussion.
I believe the method, in post #1 by Sunny, is technical correct if you want to find the CG of a NON-MOVING object, with an irregular shape. I believe you can find this topic in our primary school's Science.
BUT this method is NOT practical if you are trying to find the true CG of a MOVING object. We know the CG will shift when the object is moving. Try taking a train and you will know why we keep shifting about when the train accelerate or slows down.
So, using the above method to determine the true CG for a plane may be an incorrect advice to give, to people who are just starting out.
For newbie, it is advisable if they seek assistance from people who has more experience.
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Originally posted by yongsinchee View PostPermit me to add my thoughts to his discussion.
I believe the method, in post #1 by Sunny, is technical correct if you want to find the CG of a NON-MOVING object, with an irregular shape. I believe you can find this topic in our primary school's Science.
BUT this method is NOT practical if you are trying to find the true CG of a MOVING object. We know the CG will shift when the object is moving. Try taking a train and you will know why we keep shifting about when the train accelerate or slows down.
So, using the above method to determine the true CG for a plane may be an incorrect advice to give, to people who are just starting out.
For newbie, it is advisable if they seek assistance from people who has more experience.
CG is CG and is NOT dependent on whether an object is moving. This is the point that i wish to clarify in this post.
And bro Sunny method is CORRECT in determining the Center of Gravity aka CG of an object. Something learnt in Pri school does not necessarily mean that it is incorrect.
I presume you do not hv engineering background, else you will agree.
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Originally posted by yongsinchee View PostPermit me to add my thoughts to his discussion.
I believe the method, in post #1 by Sunny, is technical correct if you want to find the CG of a NON-MOVING object, with an irregular shape. I believe you can find this topic in our primary school's Science.
BUT this method is NOT practical if you are trying to find the true CG of a MOVING object. We know the CG will shift when the object is moving. Try taking a train and you will know why we keep shifting about when the train accelerate or slows down.
So, using the above method to determine the true CG for a plane may be an incorrect advice to give, to people who are just starting out.
For newbie, it is advisable if they seek assistance from people who has more experience.
Just my 2 cents.
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Originally posted by GIWM View Postbro, pardon me, but you are complicating matter again like joe did.
CG is CG and is NOT dependent on whether an object is moving. This is the point that i wish to clarify in this post.
And bro Sunny method is CORRECT in determining the Center of Gravity aka CG of an object. Something learnt in Pri school does not necessarily mean that it is incorrect.
I presume you do not hv engineering background, else you will agree.
So, ..... you are looking for some engineering background to answer your query.
Yes, you are right; CG is CG regradless of static or dynamic. But, that's when we are talking about Mechanic of Solid.
In Aerodynamic however, other than the solid object "CG", you will have another quantity, that is Pressure Centre; call it "PC". The PC is actually the centre point of lifting forces. Most planes are designed to have the PC behind the CG, unless you are inventing some special flying object. So to determine the correct position of this "final CG" is not an easy task. Moreover, when your plane flying at different velocity would alter the PC. This is why when you throttle up your plane, it tends pitch up (due to increase in lifting force and moment about the CG). How determine the lifting force? I will charge $$ for the details before could reply.
So, do you think your method works?
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Originally posted by PT19 View PostI don't feel like replying you, but less this subject confuses other....
So, ..... you are looking for some engineering background to answer your query.
Yes, you are right; CG is CG regradless of static or dynamic. But, that's when we are talking about Mechanic of Solid.
In Aerodynamic however, other than the solid object "CG", you will have another quantity, that is Pressure Centre; call it "PC". The PC is actually the centre point of lifting forces. Most planes are designed to have the PC behind the CG, unless you are inventing some special flying object. So to determine the correct position of this "final CG" is not an easy task. Moreover, when your plane flying at different velocity would alter the PC. This is why when you throttle up your plane, it tends pitch up (due to increase in lifting force and moment about the CG). How determine the lifting force? I will charge $$ for the details before could reply.
So, do you think your method works?
I don't wish to go into detail on it otherwise i myself will be complicating matter. For detail of that you can dig joe's treasure and thrust him in what he says.
In order to keep the relevance of discussion to bro Sunny suggestion, i will just say that the Important thing to note is that CG, unlike CP, is not dependent on flight conditions [not whether plane is moving or not]. It is only dependent on the distribution of mass of the plane. So unless some of your components move during flight eg fuel slosh, the cg will remain fixed in flight.
Bro Sunny, you hv to pardon most of the technically challenged bros here.
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Originally posted by yongsinchee View PostHaving posted my first comment, in this discussion earlier, I fails to understand GIMW comment ".... you are complicating matter again .....".
Did I post earlier on this subject? Hmmmm.... Maybe that is how engineers work. I wouldn't know since I am not an engineer.
What he's trying to say is don't complicate things further.F5D Stratair Viper Triple Carbon
F5D Stratair Demon
F5D Jibe
Jiri Bachinski Escape Pylon
Voodoo S400
Kyosho Phantom 70 Reno racer
La Racer 56
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My 2 most simple; "uncomplicated" cents
This is a forum guys.
Different perspectives/opinions inherently exist among us hobbyists.
These differing perspectives/opinions should be taken with a pinch of salt; not an entire bucket load - with less egotistical/offensive remarks on who said it right and who said it wrong.
Just my 2 most simple; "uncomplicated" cents...Irony = displaying enough parking coupons on your dashboard but getting fined for littering when you throw the stubs on the floor
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Originally posted by joe yap View PostI did many posts so far. You just have to go through the achives. But that is just another story........
I wouldn't want to do it just to entertain a troll anyway.
It is a bit unhealthy here. some dennis guy even suggest having discussion hiding behind the PM "curtain" LOL. Can you imagine what will be like if everyone discuss behind curtain? then what is the pt of having a forum?
I am new to this forum. From what i observed so far, there are a few self-proclaimed "gurus" who are quite egotistic and feel very unhappy when some "junior" post something that are not in line with their ego. They will use very nasty words in reply, trying to intimidate. Instead of offering correction to wrong concept like eg "cg is dependent on whether an object is moving" which is utterly wrong, they will just go on showing off their past successes and worse, boasting that a 7 channel transmitter is too lowly for them.
i hope that all these seniors can be less egotistic
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Originally posted by GIWM View Postya, esp some very senior people here, very egotistic and like to use offensive words when they feel challenged.
It is a bit unhealthy here. some dennis guy even suggest having discussion hiding behind the PM "curtain" LOL. Can you imagine what will be like if everyone discuss behind curtain? then what is the pt of having a forum?
I am new to this forum. From what i observed so far, there are a few self-proclaimed "gurus" who are quite egotistic and feel very unhappy when some "junior" post something that are not in line with their ego. They will use very nasty words in reply, trying to intimidate. Instead of offering correction to wrong concept like eg "cg is dependent on whether an object is moving" which is utterly wrong, they will just go on showing off their past successes and worse, boasting that a 7 channel transmitter is too lowly for them.
i hope that all these seniors can be less egotistic
Which part of my forum did I put down on 7 channel transmitter? I simply say if you are keen on certain model discipline, some radio have better features.
I would like to take a poll if my words have been offensive?
1. GIWM
2.
3.
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Originally posted by GIWM View Postya, esp some very senior people here, very egotistic and like to use offensive words when they feel challenged.
It is a bit unhealthy here. some dennis guy even suggest having discussion hiding behind the PM "curtain" LOL. Can you imagine what will be like if everyone discuss behind curtain? then what is the pt of having a forum?
I am new to this forum. From what i observed so far, there are a few self-proclaimed "gurus" who are quite egotistic and feel very unhappy when some "junior" post something that are not in line with their ego. They will use very nasty words in reply, trying to intimidate. Instead of offering correction to wrong concept like eg "cg is dependent on whether an object is moving" which is utterly wrong, they will just go on showing off their past successes and worse, boasting that a 7 channel transmitter is too lowly for them.
i hope that all these seniors can be less egotisticIrony = displaying enough parking coupons on your dashboard but getting fined for littering when you throw the stubs on the floor
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Originally posted by GIWM View Postcg is cg lah, why complicate the matter?
it is just a point where all the mass appears to act, where you can balance the plane. Vectors, reference, dynamic forces are all nonsense that complicate matters. No need using such complicated word as vector lah. The direction portion is always pointing down towards earth due to gravity.
For one being egoistic or not, is subjective. I tried to be as cool as possible in my post in order not to provoke any unwanted and irrelevant squabbles.
I always try not to be judgemental, and if you read my first reply on this thread, I only brought up to the author's attention that not to confuse the CG of a stationary object with the CG of an airplane. I didn't even mentioned that his method is wrong, and so what is actually the problem now?
If you look at your own post I quoted above, in fact you are the one who started shooting down other's opinion. Instead of using aggresive words against my previous post, why don't you just be more diplomatic by saying politely " I have a different opinion here."
Just sticking to your opinion is suffice. There's no need to gain credit by pulling someone down.
Now it seems that you might be the one who started stepping onto other's tail and then criticizing thier reactions.
I can also foresee that you'll start quoting my other posts and flaming me again, but all I can say now is that these are just my reactions to your accusation.
For the sake of the health of this forum, I'll really wish to stop these. GIWM, may your God Is really be With you(Me). Post what you want, I stop reacting.
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