RV-7 with IO540 Battery in Tail for CG

I was looking at an RV7 for sale that has an IO540 in it. They have installed the battery in the back for CG.

Anyone have any experience with this set up? I was a little worried that it might add undesired momentum for ground looping.

Also, it bothered me that it would affect the aerobatic handling and maybe safety.

Thanks,

Sheldon

sheldon957 said:

I was looking at an RV7 for sale that has an IO540 in it. They have installed the battery in the back for CG.

Anyone have any experience with this set up? I was a little worried that it might add undesired momentum for ground looping.

Also, it bothered me that it would affect the aerobatic handling and maybe safety.

Thanks,

Sheldon

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I have a number of solo hours in the Super 7. I can not tell any ground handling differences. It has no undesirable ground handling characteristics. It does absolutely change the aerobatic handling of the plane. Each pound added is a pound of unhappiness for aerobatics.

Be aware that a few aircraft have had access panels added for batteries in the tail. Vans would not approve such a modification. With the design of the tail structure properly installing such a access would require extensive engineering and rework of the structure. I would take a hard look at the aircraft if a access has been cut.
G

sailvi767 said:

Be aware that a few aircraft have had access panels added for batteries in the tail. Vans would not approve such a modification. With the design of the tail structure properly installing such a access would require extensive engineering and rework of the structure. I would take a hard look at the aircraft if a access has been cut.
G

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I was told there was an access panel cut. Something else to consider.

Kahuna said:

I have a number of solo hours in the Super 7. I can not tell any ground handling differences. It has no undesirable ground handling characteristics. It does absolutely change the aerobatic handling of the plane. Each pound added is a pound of unhappiness for aerobatics.

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Kahuna,

Thank you for your input. On the aero, I was thinking about some maneuvers such as the humpty bump, at the top where you throw the tail over and how the tail weight would affect it. Also at the top of a hammerhead. Just extra weight to sling around, and then the momentum might take you too far

Of course the 7 does have a pretty good size rudder to counter act it.

Plenty of Super 8s built by John Marshall with the access panel cut for the rear battery. I do not know of any of them falling out of the sky because of the rear battery access panel.

sailvi767 said:

Be aware that a few aircraft have had access panels added for batteries in the tail. Vans would not approve such a modification. With the design of the tail structure properly installing such a access would require extensive engineering and rework of the structure. I would take a hard look at the aircraft if a access has been cut.
G

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If the standard techniques for the panel opening were followed, such as the perimeter doubler with nutplates, and the proper number of screws to attach the cover, then I don't see the structural problem you're worried about. This is exactly how the inspection/access plates are installed all over the wing bottom skin with no issues. I would think that the wing bottom is stressed more than the forward empennage. Just my engineer brain thinking out loud. Van's also doesn't want 540's in any RV except a 10, so they would not support the access panel either.

10" longer Super Six

My battery is located just forward of F8 and accessed through luggage area (not easy) I so much wanted to make an access panel but could not figure out a way with out weakning the monocque structure. CG came out at the perfect point. not too far forward and not too far aft. As for handling it is great in all respects. Not equal to a light stock RV6 or 7 in handling because of the extra length and and weight but the compromise is well worth it to me. 1100+ hours and going strong with no issues. I will mention that the fuselage was re-engineered for the the 540 engine and extra length. All the .024 skins changed to .032 and the .032 to .040. The .040 skins remained the same. There are two that were made based on the original Hallendorf Super Six engineering. There are three other 6's that I know of that are built a little differently (maybe more 6's too). No two are alike. As for the Super 7's I don't know much about them.

My 6 is licensed as "The Barnes' Stormer" N183SB

Steve Barnes

I have the Hallendorf Super Six, and like Steve said, there are strength mods incorporated (skin thickness, stringer thickness) and the fuselage is lengthened with one-off engineered bulkheads. My battery is further aft then Steve's and I have no access panel (battery changes are a gymnastic event?or a tunnel-rat experience?but do-able).

The CG range is great with the battery there, and I've found, in 1450 hours total, 1000 in my hands, the aircraft to have great ground and air handling qualities. Very stable, with no mis-behavin' tendencies. No issues in basic aerobatics noted so far.

As for an access panel, I would check the workmanship there as well. Could very well be fine, if good techniques were used, as Blackhawk said. F1Boss Mark and I have had some conversations about rear fuselage strength, and its an important aspect of Rockets and Super RVs to maintain for flutter margin, etc.

If Kahuna has wrung out the Super 7, then that is a good assessment!

Cheers,
Bob