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RE: The new Tornado sport jet - 11/9/2011 6:22 PM   
megafly


 

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Status: offline 		But with that cg the plane can't slow down for lanndings, it not conservative it's nose heavy, and the 1.5 lbs on the nose, at least for me the plane was tail heavy...

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RE: The new Tornado sport jet - 11/9/2011 8:33 PM   
KC36330



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Status: offline 		I'm shocked that my Tornado even flies................ dry weight is 14 lbs 3.2oz, blocked her up level and weighted the nose wheel........... 1lb 2oz, i guess i need to add 6oz of lead before the next flight

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RE: The new Tornado sport jet - 11/9/2011 10:58 PM   
Pondus


 

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quote:

ORIGINAL: megafly

Cg location in the manual ''CG Location- 12 3/4 inch back from the leading edge measured at the wing root,'' is wrong! If you balance that way the plane is going to be very nose heavy.


13" works very well for my Falcon, so it can't be very nose heavy if balanced at 12 3/4", that 1/4" difference won't make too much difference. I have no problem at all slowing down or loosing elevator authority at low speeds so I'm definately not nose heavy.

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RE: The new Tornado sport jet - 11/9/2011 11:19 PM   
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quote:

ORIGINAL: KC36330

I'm shocked that my Tornado even flies................ dry weight is 14 lbs 3.2oz, blocked her up level and weighted the nose wheel........... 1lb 2oz, i guess i need to add 6oz of lead before the next flight

Your nose wheel would actually weigh a bit more, since yours is dry and Henry says to balance with the UAT full. But your point is well taken. The 1.5 on the nose wheel only works if the total weight is the same. BTW where is the CG located on the wing? Do you agree with the 12 3/4 figure?

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RE: The new Tornado sport jet - 11/9/2011 11:30 PM   
KC36330



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Status: offline 		UAT full is dry weight............, you always balance with UAT full, it's considered part of the dry configuration.

my CG is a good bit back from the recommended, i put it there (as suggested in the instructions), flew it and adjusted till it was where i liked it, and i didn't recheck and measure it.

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RE: The new Tornado sport jet - 11/9/2011 11:47 PM   
Dr Honda



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quote:

ORIGINAL: DrYankum

..... BTW where is the CG located on the wing? Do you agree with the 12 3/4 figure?





Mine is at 13".


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RE: The new Tornado sport jet - 11/9/2011 11:53 PM   
KC36330



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Status: offline 		just measured, i'm a tad over 13 5/8", it flew fine at the recommended 12 3/4 but it wasn't how i liked it. with more power (i've got a P-60SE on mine) the more forward CG wouldn't of been as much of an issue to me.

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RE: The new Tornado sport jet - 11/10/2011 3:34 AM   
warbird51


 

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Status: offline 		Our Tornado came out at !7lbs dry with the UAT full. We balanced it at the 12.75" dim. listed in the manual. We double checked the nose gear weight and it was 1.8lbs. Had we used the 1.5 lbs, we would have been tail heavy. The 1.5 lbs will only be accurate if you have the same emty weight as the Modelbau listed emty weight. At 12.75" the balance is perfect on our Tornado.

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RE: The new Tornado sport jet - 11/10/2011 11:42 AM   
BaldEagel



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Status: offline 		Does not matter what the overal weight is, if you get 1.5Lbs on the nose wheel the C of G will be in the same place no matter the overal weight, think about it, put 6lbs of lead in the back, to achive 1.5lbs on the nose wheel you will need approx 12lbs of lead in the front to counterballance the load, (assuming a 2:1 ratio of distance to the C of G) you have just increased the weight of by 18lbs but still only have 1.5lbs on the nose wheel, unless it has given way under the weight.

The thing that confuses the issue is that the fulcrum (main UC) is not on the C of G, but if we think of the fus as a simple beam it starts to get a little clearer.

Mike

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RE: The new Tornado sport jet - 11/10/2011 11:50 AM   
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Status: online 		Mike,

Assume that you have a 10lb model and then you place a 10lb weight exactly on the c.g. Are you saying that the weight on the noseleg scales won't change?

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RE: The new Tornado sport jet - 11/10/2011 11:59 AM   
BaldEagel



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Status: offline 		No, its the problem as I tried to explain above, because the C of G is forward of the fulcrum the weight on the nose wheel will go up by the multiple of the distance, its only if you distribute the load at either end of the beam that the reaction at any point will stay constant, in our scenario the weight increase is likely to be because of a heavier turbine that has to be compensated for by moving the batteries/UAT etc.

Put this another way, put that 10lb weight over the main wheels/fulcrum?

Mike

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RE: The new Tornado sport jet - 11/10/2011 12:13 PM   
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Status: offline 		If you increase the weight of a plane, and keep the CG at the same exact point, I guarantee you that the weight on each wheel MUST go up (unless, of course, you move it to a low gravity world)!!!!

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RE: The new Tornado sport jet - 11/10/2011 12:32 PM   
BaldEagel



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Status: offline 		Yes the weight on each wheel will go up, but if the load is universally distributed the weight of the beam/fus is irrelevant, the C of G is so close to the main wheels on most airframes that the difference to the weight on the nose wheel is disproportionally small to the overal weight increase and that is the problem, because the C of G is in front by a small margin from the fulcrum (main wheels) the weight on the nose wheel will go up by a small amount, if the C of G was on the main wheels the difference in overal weight would not alter the weight on the nose wheel as long as the weight was a UDL (universally distributed load).

All I was trying to do was explain that the overal weight of the airframe does not make a great deal of difference to the position of the C of G taking into account the weights that we put in our airframes and how we distribute it, they would largely be within the C of G range of the airframe.

Mike

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RE: The new Tornado sport jet - 11/10/2011 12:44 PM   
Woketman



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Status: offline 		But the point is: If you increase the weight of a plane, and keep the CG at the same exact point, I guarantee you that the weight on each wheel MUST go up (unless, of course, you move it to a low gravity world)!!!!

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RE: The new Tornado sport jet - 11/10/2011 12:51 PM   
Couch Potato



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Status: offline 		Mike, you don't own a blue cap by any chance ?



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RE: The new Tornado sport jet - 11/10/2011 12:54 PM   
BaldEagel



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Status: offline 		Blue, Green and Brown. LOL

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RE: The new Tornado sport jet - 11/10/2011 12:57 PM   
Dr Honda



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Status: offline 		BaldEagel: You have given me a lot of good info in the past... (including mounting my engine at 0 degrees thrust) but in this case, you're incorrect.


As the weight changes... the scales have to change. Yes, the CG is in front of the rear tires, so the weights at the tires will change as a ratio of the distance from the CG. Weighing a single leg will not give you a valid CG.

Also... for the guys who said it has the be the same weight as the Modellbau demo model are not right either. It has to be the same in every respect. Think about this... what if I used full sized, metal gear servos out in the tail, but then I used small lipo batteries, and they are, and I had the exact same overall weight. By logic, I have a lot more weight at the tail than they do. SO... to use the 1.5Lb reliably... you have to not only use ALL the same equipment they used... but it has to be located in the same place.

A second example would be if I used a straight rear landing gear leg, or a trailing link. Lets assume they are the same weight. But the rear tire will shift back 1/4" or more from the straight leg. Now... a tire moving back a little will not affect the CG much, (in reality, it will move the true CG back) BUT, the effect on the scale is that the front tire will become heavier.


Anyway... what I'm saying is, the responsible thing for Modellbau to do is to NOT give a nose wheel weight. By it self... it's a dangerous number.



****** EDIT ******

Here's an FAA wights and balance PDF


http://www.faa.gov/library/manuals/aircraft/amt_handbook/media/FAA-8083-30_Ch04.pdf


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RE: The new Tornado sport jet - 11/10/2011 2:42 PM   
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We did no such thing if you look at the manual it gives both methods 
 
1.5 lb on the nose or 12 3/4 inches from the leading edge of the wing measured at the wing root. 
 
We have built about 40 airplanes for customers and ever one was exactly the same 1.5lb on the nose. 
 



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RE: The new Tornado sport jet - 11/10/2011 2:56 PM   
Xairflyer



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Status: offline 		I always find with these sort of things if you take it to an extreme it can be come clearer.

What weight would be on the each wheel if the aeroplane weighed 100Ton

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RE: The new Tornado sport jet - 11/10/2011 3:06 PM   
KC36330



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quote:

ORIGINAL: Xairflyer

I always find with these sort of things if you take it to an extreme it can be come clearer.

What weight would be on the each wheel if the aeroplane weighed 100Ton



10 ton as the nose is holding about 10% of the AUW.

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RE: The new Tornado sport jet - 11/10/2011 3:08 PM   
Dr Honda



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quote:

ORIGINAL: Xairflyer

I always find with these sort of things if you take it to an extreme it can be come clearer.

What weight would be on the each wheel if the aeroplane weighed 100Ton



Exactly....

According to Modellbau it will still weigh 1.5 Lb on the front gear. Now I have to go weigh mine.


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RE: The new Tornado sport jet - 11/10/2011 3:42 PM   
DrYankum


 

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Status: offline 		Copied from that other site The 1.5 on the nose wheel is based on part from this method



This method is how I go about checking CG on a plane that weighs too much to put on a CG machine or lift.

Have the plane all assembled RTF minus fuel. Find a place where you can put the nose of the plane up against a wall. Take a level and prop up the tail wheel till the fuse is sitting level. Your gonna have to take the hatch off in most cases to set the level on.

Once the plane is sitting level, mark on the ground the two points where the main wheels are with masking tape and draw a line right where the wheels contact the tape. Then make a mark where the center of the tail wheel sits in the same manner. Its gonna be on whatever you propped the tail up with. (I use magazines)
Its also a good time to measure from the wall, how far back the recommended CG is. Save that number for later.

What you are looking for at this point is the distance to each wheel from the tip of the spinner. (which should be touching the wall at this point)
I use a long straightedge to get the distances

Lets say you come up with theses numbers:
LH main - 22 inches
RH main - 22 inches
Tail wheel - 70 inches

Now get a scale and place it under each wheel individually. You will have to re-adjust the other wheels to keep the plane sitting level. Add more magazines.
(If you have three scales you can get the weights at the same time but make sure the plane is level)
Remember to put the hatch on after you level the plane before you weigh each wheel. You gonna wind up with three weights. One for each wheel.

Lets say you come up with these numbers
LH main - 9lbs
RH main - 9lbs
tail wheel - 5lbs

Now its just a simple math problem to find where the CG sits right now on the plane.

Weight x ARM (distance) = Moment
22x9=198
22x9=198
70x5=350

Now add the total of all the moments and the total of all the weights.
Weights 9+9+5 = 23lbs
moments 198+198+350 = 746

Then divide the total moments by the total weights.
746 divided by 23 = 32.43

That number 32.43 is "in inches" how far back from the tip of the spinner to where the plane balances right now.
Compare that to the distance that you measured earlier to the recommended CG location.
If you are off one way or another adjust items then recalculate the weights. The distances (or ARM's) aren't going to change so you already have those numbers.


It may sound confusing and a lot of work but it really only takes about ten minutes to do it.

This is generally how full scale planes are balanced. You cant go lift one of them by your fingers or stick it on a CG machine.


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RE: The new Tornado sport jet - 11/10/2011 5:23 PM   
rpat



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Status: offline 		DrYankum
Great post and thanks for the info. Your way should make the balance point dead nuts on.

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RE: The new Tornado sport jet - 11/10/2011 5:59 PM   
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Status: offline 		Dr. Honda hit one out of the park. He has it right!!!!

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RE: The new Tornado sport jet - 11/10/2011 9:05 PM   
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Dr. Honda you are absolutely right for the most part. Your calculations work great for small GA airplanes but for big stuff it's a little more complex than that. 
 
I'm a Checkairman on the MD11 and also instruct at Boeing in Miami on the 737,757 & 767. Moments on all real airplanes are precisely calculated and equipment is places exactly in those locations. Every piece of equipment has a moment calculated and a % of MAC. Installation is the same on every single airplane. If it was not the weight and balance graphs would be off. 
 
On RC planes this method cannot be done because everybody installs things in a different location even if the instructions say not to do it. 
 
Everybody is an expert which complicates things in the RC world so things should be kept simple. 
 
I have logged over 1500 flight on Tornados this year and I am telling you guys on our airplane 12 3/4 inches or 1.5 lb on the nose is correct for the general publics flying style and easy of handling of this airplane.  Now somebody like KC which has lots of turbine experience he can move the CG to his flight style which he has done. 
 
The empty weight of your airplane for the Version 1 or Version 2 Tornado's should be 14lb give or take 1/2 lb with a P60 or 15.5 lb give or take 1/2 lb with P70,K80
 
If Your plane weighs more than this you have not followed instructions and added extra things to the plane. 
So I recommend you use the conversional CG method to calculate your CG. Let's keep this simple guys it's not rocket science. 
 
Now anybody wanting to have some fun and if you are in Miami come and sign up for my advanced aircraft systems course at the Boeing training center and get some stick time on a 737-800 simulator. Lol



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