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Jacking RV-7 Fuselage at Firewall Flange?
I'm getting ready to fit the wheel pants and leg fairings on my RV-7 - so I need to get the fuselage up off the wheels and leveled, etc. The engine is hung and most FWF is done so the fuse is pretty heavy. Problem is, the plane is still in the shop and neither the wings or tail is on - so I can't jack using the wing lift points plus it appears the CG is pretty far forward of the wing spar attach structure in this configuration which would make it difficult to jack at that location. The question is, has anyone jacked one up under either the lower firewall flange or the engine mount cross bar when in this heavy configuration? If you have, what sort of fixturing (if any) did you use?
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I just did this a couple of weeks ago. Borrowed an engine hoist. wrapped some web straps around the engine mounts as close to the firewall as I could, and viola. Had to mess with the strap length a little to get the hoist to clear the front baffles. Sawhorse under the tail makes it easy to tweak for level, and shims under whichever side's tire you're not working on for level the other way. Good luck.
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I did this when building my RV-6A. I cut a clean 2X6 to fit between the fuel vents (for the tail-dragger, you could trim to fit the gear mounts as well) and act as a pad for two wing jacks I borrowed from a friend. There's plenty of structure up front, so it's safe as long as you don't concentrate the force all at a single point. I should mention that I did my gear before i had the engine mount on; for the RV-10, I used the method of hoisting by the mount.
Oh, yeah, and after my incident a while back, I hoisted the aircraft by the bent mount, put a sawhorse with board and padding under the fuselage a few inches behind the firewall, and proceeded to remove the engine, mount, and firewall to do my repairs. The sawhorse was a fine support and, even with the firewall removed, there was no problem with supporting the airframe that way. Once the repairs were done, it was simple to hoist the airframe again and remove the sawhorse before setting the aircraft back on it's wheels. |
Tubes
Its beginning to sound like using the cross tube would be a better choice. There is a good bit of structure along the lower firewall flange (angle riveted in both planes) as well as the hard points where the engine mount attaches. I wouldn't be worried a bit to lift in this area if the 300+ lb engine and accessories weren't on. My specific worries are buckling the lower firewall flange or localized crushing of the engine mount cross tube. Since people seem to be able to lift at the mount using straps with no damage, I suspect I could also jack this area if I used an appropriate saddle (drilled wood block, etc.) around the cross tube close to where it welds into the gear leg socket.
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Please post photos if you do this... It would surely help others in future. |
If your engine is already on, I'd suggest a 2-ton hoist (surely you have access to one or how did you get the engine up there?;)) and lift from the engine hoist ring. If you have a tri-gear, put a padded sawhorse under one of the rear bulkheads (the baggage bulkhead or seat bulkhead would be my preference) and lift enough to get another sawhorse under the fuselage just aft of the firewall (leaving enough room to drive rivets) as a safety. Ease the hoist down so that the engine is neither bearing down on the mount or lifting it up before you drive those firewall rivets. A little tension is fine, but the weight of an engine there is a bit much, at least in my opinion, until the rivets are driven.
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I have used the engine mount cross tube multiple times without trouble. Skylor |
Just Jacking
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I've got a tail dragger. Also, there is no riveting going on here - all of that up around the firewall has been done for years. I was just looking to lift and then support the (front) weight of the plane on the lower firewall flange or the ~ 1" diameter cross tube on the engine mount so I can fit the wheel pants. Quote:
I assume you are talking about the same tube I mentioned above (runs between the gear leg sockets)? Did you jack/support under it or did you lift with a strap? Did you do anything special (fixtures, padding, etc.)? |
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No----do not lift the aircraft with the engine hoist ring! Cracking the engine case will make you sad........ The engine hoist ring is intended to support only the engine weight, not the additional weight of the aircraft. |
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