How to perform W&B on a Taildragger

So, I am days from having my DAR come out to insect my RV7. In searching, I have found plenty of info on W&B numbers, but none on how to perform the actual test. I have good scales for the test. My confusion is when weighing it, I understand the aircraft needs to by in level flight attitude. Since it has never flown, I have no idea what that is (slightly nose up or nose down). Obviously, every degree nose down, has a significant effect on the tailwheel weight. So, does everyone just level the airplane using the canopy rail and call it good from there?

Thanks, getting EXCITED!!!

Level the longeron

Thanks Brian, I believe the longeron is level to the canopy rail right?

Yes, it is.

Also make sure that the aircraft is in normal flight configuration;
i.e. Canopy closed, flaps up, all seat cushions in place, etc.

Weighed in at a trim 1028 lbs! 70lbs on the tail. Maybe a little tail heavy, but not bad.

Mel said:

Also make sure that the aircraft is in normal flight configuration;
i.e. Canopy closed, flaps up, all seat cushions in place, etc.

Click to expand...

With oil but no fuel...

I had to have the hangar practicly hermeticly sealed to get an even reading. with a door open th e scales were dncing around. Closed up I got 3 exactly the same readings.

Personally, I weigh the airplane with the tail down as well, which is a simple and quick way to cross check the empty weight. I also weigh the thing three times, rotating the scale pads each time. So all in all, I move the airplane on and off the pads 6 times. (3 tail down, 3 tail up).

I was in charge of our club's scales for a number of years and came up with a much simpler way to weigh taildraggers than many people seem to use. You will need one helper.

First, weigh the airplane in 3-point configuration, to get the total weight (W). Chock the front wheels on the scales while doing this, it's important for the next step.

Second, raise the tailwheel off the rear scale until the level reference reads level. Support the tailwheel by putting it on a flat piece so you're only taking its weight on the contact point of the tire. I used a short piece of 2x6 most of the time, but I did have equal success holding the tire in my hand after a bit of practise.

With the tail raised, have your helper read the weights off the main wheel scales (WL and WR). Put the tail down and you're done.

Tail weight in flying attitude is simply W minus (WL plus WR).

You've now got everything you need, and you didn't have to build up a support that would hold the tail high enough and support a scale at the same time.

Incidentally, the reverse procedure worked well on an RV-7A as well... With the main wheels still on the scales, remove the scale under the nosewheel, and let it drop until the plane is level. As luck would have it, in the hangar we used there was a depression in the floor that was exactly right to allow the plane to sit level. It looked like on a level floor you might need a 5/8" sheet of plywood under the scales on the main wheels, but that will depend on the scales you're using.

A couple of missing items.
It is also important to level the wings laterally. This can easily be done by adding or removing air from one of the tires.
Also: you should drop plumb bobs from the leading edge of the wing, when it is in the LEVEL flight attitude. This will allow you to get the measurements from the axles relative to the leading edge of the wing. Due to the dihedral of the wing this measurement changes as you raise and lower the tail of the aircraft.
I have found differences of half an inch to an inch in the axle/leading edge measurements as compared with the numbers in the Van's literature.