Fuel tanks are forward of the normal c/g on all RVs except for the -12.
Therefore the c/g will move aft as fuel is burned.
Worse case aft c/g is with minimum fuel, maximum rear baggage and occupants.
 
In my 9A, flying solo with 45 lbs of baggage my CG is 80.15 with full fuel and 80.60 with 6 gallons left. So yes, the CG moves back 0.45". What I notice is the weight difference, not the CG.

I'm not sure why you're asking but in terms of handling, the weight (a pax and full tanks) seems to me to make a bigger difference to the feel of the plane than the CG shift. Additionally, as you get close to gross weight and an aft CG, there's a noticeable difference in the landing flare. None of it is dramatic at all, just noticeable.
 
Don said:
as you get close to gross weight and an aft CG, there's a noticeable difference in the landing flare. None of it is dramatic at all, just noticeable.
Click to expand...

I agree. The first time I flew with my better half on a x-country with 50 lbs of luggage, the change in flare "feel" and pitch sensitivity after burning 17gals was very noticeable. Not really a problem, but that landing was a tad "klumsier" than most of my non-event 9A landings. As one might guess, sensitivity to aft stick pressure was significant. I don't notice that effect when the luggage bay is empty, even with passengers.
 
Careful with a -10

With typical loads the cg of a -10 moves aft as you burn gas. But, when I fly solo, the starting cg is close to the forward limit, and the cg then moves forward as I burn gas. E.g. You must always check the zero fuel cg if you are starting anywhere near either limit.
 
Right on

Exactly what Bob said.

It is possible to actually take off in C/G, and burn off enough fuel that you will land out of C/G aft---------in the 10. Dont know about other models.
 
Just hangar flying the idea of adding more fuel to a 9. Payload wise, it seems as if it will carry it. The thoughts went along these lines: Add more gas, and set it up for auto fuel. Fuel only at home. Also, range and endurance are a good thing in my book.
I know opinions will vary, but the nine looks best suited for some LONG flights... It's like having a long EZ that can take off and land on grass...
Back to dreaming...

Dennis

BTW, thanks for all the replies. Theres a lot of experience here... :)

Don said:
I'm not sure why you're asking but in terms of handling, the weight (a pax and full tanks) seems to me to make a bigger difference to the feel of the plane than the CG shift. Additionally, as you get close to gross weight and an aft CG, there's a noticeable difference in the landing flare. None of it is dramatic at all, just noticeable.
Click to expand...
 
Not to be a wet blanket, but . . . Be sure you understand the design impact of adding fuel weight like this. It's not just a GW issue. WHERE you put the mass is also very important to controllability.
Van's put the fuel as close to the actual CG as possible. I've seen some add-on tanks that go out in the wing tips. When used to hold fuel, this puts a lot of mass at the end of a very long arm.
I know a -9 is not intended for aerobatics, but you get a yaw going with that long pendulum at the wing tip and you may not have the control authority to recover.
Not to say don't do it, but understand exactly what's involved in such a big design change. Besides, as you get older you may find that the limit of endurance is not the fuel you carry, but your bladder.
 
larharris2 said:
Besides, as you get older you may find that the limit of endurance is not the fuel you carry, but your bladder.
Click to expand...

Sounds like Dennis is looking more at carrying enough fuel for making a round trip without taking on fuel rather than simply extending range to avoid fuel stops. There's a lot of value in that.

There is a lot of truth in the fact that adding tip tanks can change the way a plane controls. We have added 15 gallons outboard of the main tanks on each side in our -10 and have flown hundreds of hours. I have flown with and without fuel in the tip tanks, including flying other -10's without extra fuel tanks and have noticed no difference in handling. I do make a point to get as much of the outboard fuel inboard before landing. I'm not sure which planes do this, but there are some certified birds that added tip tanks after certification and they actually allow an increase in useful load for outboard fuel because it can actually reduce the bending moment on the spar. Don't quote me, but that's what I understand. Landing with fuel outboard would do the opposite, which is why I try to reduce the amount of fuel outboard for landing as much as possible, which is usually easy because I only use the tip tanks on long range flights or round trip flights, so by the end of the outbound leg, I've burned over 1/3 of my fuel, which is what is in the tips.

Btw, we transfer from the tips into the mains like the safair tanks.
 
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