Folks

Putting a little survival bag in the baggage compartment does not do squat!! If you want to believe that old wives tale ....great.....I hope you believe in the tooth fairy too.

Yes, I am trying to get your attention.

Run the numbers. Lets say he has a 1200 pound empty weight (probably not far off for a 0-320 PA-12). To get his CG (based on the TCDS numbers).....

1148 pds on the mains at +1 = 1148 moment

52 pds on the tail at +200 = 10400 moment

Total moments = 11,548 divided by weight of 1200 = 9.62 on the empty CG (pretty close to his #9.69)

The CG range per the TCDS is 9.0 to 18.5

So lets add 20 pounds of survival gear in the baggage compartment 20 x 56(arm) = 1120

Moments 1148 + 1120 + 10400 = 12668 divided by new weight of 1220 = 10.38

You moved the CG less than 1" out of a 9 inch range. I call BS. You can't feel that in the plane. If I put you in the plane and did not tell you how it was loaded I bet you a steak dinner you are not good enough to tell the difference. There are a handful of people that fly 500 hours plus in a year in the same plane, (fish spotters and patrol line guys come to mind) that might be able to feel it because they are so intimate with the plane. You are not that good. It's a placebo, and a self fulfilling prophecy.

Someone suggested adding a quarter pound to the tail, or another leaf string. 1/4 pound will move the CG from 9.62 to 9.70. In a range of 9 to 18.5 that is totally insignificant.

Now lets play some more (take the survival kit out)

Airplane =1200 with 1148 on the mains and 52 on the tail gives an empty CG of 9.62 as noted above and pretty close to what his is at (I'm guessing)

Lets add full fuel 38gal = 228pds x 23arm = 5244moment

Pilot 200 pds x 6 arm = 1200

1148 + 5244 + 1200 + 10,400 = 17992(arm) divided by weight 1200+228+200 = 1628 = 11.05

So....in normal solo flight he is still in a pretty far forward CG

Max baggage on the TCDS is 41 pounds at 56 arm. If we max out the baggage with tools and survival gear his CG goes to 12.15 By **maxing out** the baggage we moved the CG one inch.

If we max out the allowable weight left, 81 pounds, and put it in the back seat, we get to 1750 (max gross) divided by 23,042(moments) = 13.16 That is as far aft as he can possibly **legally** load the airplane. Still not even to the half way point of the range.

In Cubs it takes roughly 10 pounds in the tail (at the tailwheel) to move the CG one inch. In a nine inch range one inch is not all that significant. So adding 20 pounds in a baggage compartment will likely move the CG less than an inch and it just does not change the "feel" that much.

I have removable weight in the tail of my Cub and I have played with the CG a lot. I have added up to 40 pounds of lead in the tail, and then test flown the aircraft to include multi turn spins. I am not a trained test pilot, nor am I am particularly good pilot, so take this for what it is worth. I would have to review the notes from my test flights but I can't remember much difference with 10 pounds of lead in the tail. It became noticeable when I got to 20 pounds, 30 pounds made a difference and the airplane flies great at that CG. When I hit 40 pounds it was starting to get a little lighter on the elevator than I personally liked, and I started to get auto-rotation coupling during the spins which was definitely uncomfortable.

Even with 40 pounds in the tail I was still about 3 inches from the aft limit. I did notice that the further aft you get the CG the more noticeable it becomes. IE moving the CG one inch from 9 to 10 is not noticeable. Moving it one inch from 16 to 17 is noticeable.

Run your own numbers and prove me wrong. A forward CG is most noticeable in the flare for a full stall 3 point. You will run out of elevator and not be able to get the tail down first. Do a bunch of full stall three points and pay attention to what is happening and how it is landing. Now put 20 pounds in your baggage compartment and go do it again and see if you can honestly tell the difference. I'll bet you can't.

Bill

(I am trying to get you fired up enough to really get to know your airplane. I want you to think "That Rusk guy is such a jerk.....I'm going to prove him wrong")