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Need aft CG - Battery move?

kozinski

I'm New Here
My RV-6 with 0-360 and fatty me need some aft CG. I cannot trim out at 80 for landings as I come in too fast when I release pressure. The AGM battery is in the usuallly place inside by the firewall. I'm wondering if anyone that has moved this to the rear baggage compartment has any input on CG affect and pictures to share. I'm open to other suggestions, like weights on the tail leg? Or? Thank you, Gary N38GK NH16 Brookline NH
 
Have you put the -6 on scales to confirm the CG location? I find this odd as most -6's and -6A are tail heavy. I have a -6A with an IO-360 and have zero issues trimming all the way down to 65 kts approach if needed. My battery is located inside the cabin aft of the firewall.

I'd verify the W&B to be safe.....
 
SNIP

I'd verify the W&B to be safe.....

And verify the trim tab deflection meets specs.

If you did not build this plane, I suggest you look to see if the builder added another shim under the HS forward spar. This was not uncommon - I did it for my RV-8A to bring the elevators more in trail for cruise. I still had full trim authority, but just enough.

Carl
 
CG

I have a 0-360 also and only run out of nose trim when it is just me with full fuel. Start adding passenger and baggage and the CG moves AFT fast!

My tool bag is pretty heavy so I just keep it against the aft bulkhead and have no problems with trim then. I have to move it forward when I start loading the plane up....
 
I have a 0-360 also and only run out of nose trim when it is just me with full fuel. Start adding passenger and baggage and the CG moves AFT fast!

My tool bag is pretty heavy so I just keep it against the aft bulkhead and have no problems with trim then. I have to move it forward when I start loading the plane up....

I would run a W&B check with all scenarios

Easier to add ballast than move battery and then be really aft in cg.

Use when solo etc.
 
6A had battery in baggage compartment in fabricated box

The battery was moved aft when an (I)O360/CS replaced O320/FP ---even then, no calculation would put the plane out of aft CG. With no one in the seat, a little forward of CG, but worked out OK when seated --- of course, fuel burn moves things a little to the rear. I never had (manual) trim issues.
 
Manual Trim distance fall short

So I checked the angles of my trim tab and I'm only getting 28 deg down and 18 deg up deflection. (looking for 35/25 per the manual). Built per plans. If I make a greater down deflection, it will be less up. What am I missing here? How to yield the 35/25 without physically changing the plans. I do recall something about a longer trim cable? Keep in mind this was one of the first kits to leave vans back in 1986. Thanks again!
 
For nose up, the trailing edge of the trim tab is down.

Adjust the linkage to get the 35 degrees spec. While you are at it figure out why you are not getting full trim travel.

Carl
 
Have you put the -6 on scales to confirm the CG location? I find this odd as most -6's and -6A are tail heavy. I have a -6A with an IO-360 and have zero issues trimming all the way down to 65 kts approach if needed. My battery is located inside the cabin aft of the firewall.

I'd verify the W&B to be safe.....

+1

First I have ever heard of someone wanting to move weight aft. Pilot sits aft of the CG line so a heavier pilot should move CG even more aft. Seems like some other problem to me.

Larry
 
So I checked the angles of my trim tab and I'm only getting 28 deg down and 18 deg up deflection. (looking for 35/25 per the manual). Built per plans. If I make a greater down deflection, it will be less up. What am I missing here? How to yield the 35/25 without physically changing the plans. I do recall something about a longer trim cable? Keep in mind this was one of the first kits to leave vans back in 1986. Thanks again!

trim tab is reverse from elevator. Tab down = elevator up = nose up. total range of deflection is dictated by the distance between tab hinge pivot and rod attach points. closer = more throw/less torque. Longer is opposite. Many of us bias the range to give more down than up, as very little up is ever required. I would go to at least 35 down and not worry about the up being less than spec; You will never need it. That said, I have never come close to full nose up trim in 800 hours and I am 200 lbs and have a 320/FP with a 20 lb crush plate, so a good bit more fwd CG than a 360 with FP prop.

I am a proponent of not fully trimming in the flare. The closer you trim to hands off at flare speed the harder it is going to be to keep the nose down in a go around. Better to under trim a bit and use the feedback force to help you "feel" what the plane is telling you. It will allow you to be a better pilot and make better landings in tougher conditions. It will also give you a better skill for dealing with the very light elevator when you are hard against the aft CG. Ever had to land with trim in the cruise setting? Best if you know how to do that, as @#$% happens with mechanical/electrical devices.

Larry
 
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Adjusting the trim tab to spec... even if it requires a new lever arm ... is going to be vastly easier than moving the battery aft.

Beware of treating the symptoms v. the root cause. Should be a take-away for everyone.
 
Have you put the -6 on scales to confirm the CG location?

Best advice of the thread :)
Many buyers will end up rubbing their eyes when doing that. The older the build, the more prone it will be to have difference on the original CG and weight. Assuming it was done properly in the first place.
They are a few thread about doing the procedure correctly here on your very VAF ;)
 
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