Weight and balance with jack stands

[AltonD]

I am going to weigh an RV7A in the morning. I was going to jack up the plane and put the scales under the main gear and then let down the jacks. It occured to me that I can just put the scales under the jack stands but I would need to measure the arm of the tiedown station. has anyone done it like this? I am sure they have. I was looking for someone else' measurement to bounce off what I get in the morning.
For the nose wheel, I am just going to push down the tail and put the scale under the nose wheel. I already know that the mains must be ~1.5 inches higher than the nosewheel to put the airframe in a level attitude. I should be able to get the mains off the hangar floor no problem. I am using the scales from Avery tools.

[hydroguy2]

Why, what's the point?

[AltonD]

Its just easier to weigh the plane on the jack stands. I also think I wll get a more accurate number. But, I will have to have an accurate tiedown arm first.

[Snowflake]

Having just done a W&B on an RV-7A in the last month, I can say that weighing on the wheels works just fine. And I don't know if it was just the right combination of air pressure in the tires or a slight downhill grade on the hangar floor (there is one) but we didn't need to shim the main wheels up to get the nosewheel down to flying attitude.

A W&B using Van's standard wheel location dimensions and the weights you measure will be accurate enough for any flying you're likely to do.

[Pat Stewart]

Alton,

I would make some cheap wood ramps and pull it onto the scales. I used Bob's scales also and that worked well for me.

Pat

[Jekyll]

As a former weight and balance supervisor, I've weighed many aircraft using jacks. Works great but, you must subtract the tare weight of jacks and possibly the jack points. Example, if you intend to fly with jack point/tie down rings installed, then they are not tare, just subtract the jacks. If you intend to fly with the jack point/tie down rings removed and stowed in the baggage compartment, they must be considered tare for the scale readings and then mathematically added back in with the correct storage arm.

[AltonD]

Thanks guys. The deed is done. I measured back from the leading edge, the tie-down arm is 86 7/8" (16 7/8 back from the leading edge at 70"). I put my main gear jack stand and jack point on the scales and zero'd them out. I pulled the tiedown rings and laid them on the base of the jack stands. I pushed the tail down and put the scale under the nose wheel. The net result was that I was able to get the plane perfectly level without any shimming.