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RV6 level attitude for W&B

N64GH

Well Known Member
Patron
I want to check the W&B on my 6 and was wondering if anyone has a rough idea how high I will need to lift the tail to achieve a level flight attitude for weighing?

I am not the builder and have never done a W&B. She has been flying for 23 years (at least half of that with me). There have been changes here and there I figure it is a good idea to recheck the data.

I tried searching but I am coming up empty.
 
well, you had better search in the building manual ;) Quote: the airplane should be weighed in empty condition and in a level attitude. Level attitude is established at the datum line which is the cockpit rails.
Copies of the instructions below.
 

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was wondering if anyone has a rough idea how high I will need to lift the tail to achieve a level flight attitude for weighing?

Using the drawing in post #2, calculate a scale, and it looks like your going to need 42" to 45" plus or minus.
 
Mike, If you haven't already, register your RV6 with Van's so you can have full access to their support. If you don't have the builders manual for your RV, you can purchase this from Van's and it will answer most all of your AIRFRAME questions......
plans.JPG
 
Well calculating that from a drawing is way over my blue collar head but thanks. Just looking for a ballpark figure for a place to start.

Thanks Dave
 
Thanks Warren

I did register with vans, not long ago actually. I overlooked it with the excitement of purchasing my plane 10 or so years ago. I contacted vans with a question recently and they set me straight and got me registered with them. I do have the manuals, drawings and builders log in addition to the USB drive.

I am putting in a new fuel gauge and want to calibrate it that got me thinking "why not weigh it". That started me on the search to find out how to do that. The level attitude (for fuel and weighing) looks like it will be higher than what I have handy to put the tail on so was wanted to get an idea on how high I might be going.

Thanks again for the suggestion of registering and getting the plans.
 
I want to check the W&B on my 6 and was wondering if anyone has a rough idea how high I will need to lift the tail to achieve a level flight attitude for weighing?

I tried searching but I am coming up empty.

I can tell you precisely how high you need to get the tail - it's " A two step ladder, two pieces of 4 x 2 and a piece of 12mm thick MDF."

And that should be perfectly level. :D
 
I placed the TW scale on a Harbor Freight rolling cart and was able to shim it with a few pieces of wood until the longerons were level when the mains were on the scales. Don't forget to close the canopy when taking the weight.
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This may give you a ballpark number.
A rolling cart, a 1/8 sheet of steel, a brick, a 3/4 thick plywood and a paint mixer...;)

From when I calculated the exact distance of the tailwheel behind the Datum for W&B.
It's for my 8, but it should be very close to a 6?
 

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My RV7 fuselage is in a pretty much level attitude in the garage right now. I just went out and measured and the tail wheel is 40" off the ground. I would think that a 6 would be pretty much the same.

It's doesn't have the wings or empennage on it so I suspect a completed airplane might squat a bit more but that will be in ballpark
 
Remember you don't need to futz with a scale when the tail is elevated.

1. Weigh in 3-point attitude, record weights for each wheel: Left_A, Right_A, and Tail_A
2. With mains still on the scales, lift tail until canopy rails are level.
3. Record weights for the mains: Left_B, Right_B
4. Calculate Tail_B = (Left_A + Right_A + Tail_A) - (Left_B + Right_B)

Use the B values in your W*B calculation.
 
I can tell you precisely how high you need to get the tail - it's " A two step ladder, two pieces of 4 x 2 and a piece of 12mm thick MDF."

And that should be perfectly level. :D

Perfect, directions even I can follow :)
 
1. Weigh in 3-point attitude, record weights for each wheel: Left_A, Right_A, and Tail_A
2. With mains still on the scales, lift tail until canopy rails are level.
3. Record weights for the mains: Left_B, Right_B
4. Calculate Tail_B = (Left_A + Right_A + Tail_A) - (Left_B + Right_B)

Use the B values in your W*B calculation.

I am going to need to think about it for a minute. I am a retired firefighter, good at breaking things, not so good at math. However it will be fun figuring it out.

Thanks
 
I pondered Snowflake's calculations, and by golly, that makes sense. The overall weight of the aircraft won't increase or decrease by changing the position, just the distribution of the weight.

With that off my mind, I have one piece of unsolicited advice: if you make a stand to do the W&B, make it sturdy. My stand has been used countless times to lift the tail up when I needed to crawl around inside the plane for annual condition inspections (or whatever). Sometimes it's helpful to not be facing downhill when you're wriggling in and out of the back of the fuselage.

And I'd have to go measure the stand on my 7, but 40" to 42" sounds about right as well. If in doubt, go a little short. You can always shim the tailwheel up, but it's really hard to shim it down. If you want to get it spot on, just pick up the tailwheel to where it's about right and have a friend step underneath the horizontal stabilizer and hold up the fuselage with his back right under the HS. It sounds strenuous, but you can hold that position easier than you can hold onto that skinny tail spring with the rudder in your face. Get it level and measure the height of the tailwheel. Allow for the height of the scale(s). It took me longer to write this reply than it will for you to measure it like that. :D
 
I pondered Snowflake's calculations, and by golly, that makes sense. The overall weight of the aircraft won't increase or decrease by changing the position, just the distribution of the weight.
Exactly. I watched a few people futzing with getting the level *just right* with a scale precariously mounted atop a stand, or weighing a bunch of stand parts first and then putting them all in place while holding the tail up. Then I realized that the total is the same either way, so just calculate the tail weight.

You can do it quite quickly if you use painter's tape to hang a level off the side of the fuselage parallel to the canopy rail but below it so it clears the canopy when it closes. Weigh in 3-point, one person lifts tail, another person checks level and then reads front scales.

It's important to hold the tail by the tailwheel though, so you get the correct lifting point (the axle) and even better to put it on a small square of plywood, tile, etc. on your hands so it's a point contact and you're not applying any lateral forces.

A similar process can be used for the nosewheel RV's... Weigh in 3-point, and then remove the front scale and drop the nosewheel. With the scales I had access to, that alone was enough to level the canopy rail on a -7A. On a -6A we had to dig a little bit of dirt out from under the nosewheel to get it to lower far enough. It's much easier than trying to shim up the two main wheels to get the plane level on the scales.
 
This may give you a ballpark number.
A rolling cart, a 1/8 sheet of steel, a brick, a 3/4 thick plywood and a paint mixer...;)

From when I calculated the exact distance of the tailwheel behind the Datum for W&B.
It's for my 8, but it should be very close to a 6?

Note that the main gear legs are different lengths for each different model line.
RV6 legs are shorter than a RV7, which are shorter than a RV8 etc. So do it properly, use a level on the canopy rail (longeron) to determine what your plane’s proper tail height is. Incorrect angle here can definitely affect your W&B calculations.
 
between 26 and 28 years ago

Back before my RV-6 made first flight, I ran into the same issue.

I had some plastic milk crates that were once used to move glass milk bottles from farm to market. I wired two of them together to create a stand for the tailwheel and also serve as a stand for the tailwheel weight and balance scale.

I have moved this stand to every hangar I have had since then and still have it.

70438566293__EB132986-8DBE-4E6F-A3E5-61311E83DAF2.jpg

This stand is 30-1/2" high. Typically I use a piece of one inch board (3/4") on top of the platform to keep the plastic from sagging. Has worked great for my RV-6.
 
weight and balance set up in Dynon Skyview

Hello everyone,

I just installed an HDX on my RV6A but I have questions about how to configure the weight and balance page.

Requires at least two CG limits with the corresponding weight and arm. They should be the max forward and aft, so what values should I use, the gross weight in both cases and the max front and rear arms from the Vans Manual (68.7 and 76.8)?

Thank you in advance,

Santi
RV6A EC-ZVZ
 
Hello everyone,

I just installed an HDX on my RV6A but I have questions about how to configure the weight and balance page.

Requires at least two CG limits with the corresponding weight and arm. They should be the max forward and aft, so what values should I use, the gross weight in both cases and the max front and rear arms from the Vans Manual (68.7 and 76.8)?

Thank you in advance,

Santi
RV6A EC-ZVZ

I *think* I know what you are asking but please correct me if I’m wrong. After adding new equipment the allowed max weight and the forward and aft cg limits are still the same. What has changed is the ‘empty weight’ and ‘empty cg’ (or ‘empty moment’). You need to measure the weight and location of the new HDX. You need to measure the location (‘moment arm’) using the same reference point as the original calculations. This is usually a point just in front of the spinner, but, at least in the US, the builder may choose the reference point. So you need to find out the aircraft reference point the builder used, and use the same reference for the arm (distance) to the HDX. For the new weight, just add the old weight to the weight of the HDX. For the new CG, use the formula ‘moment equals arm times weight’, find the old moment, calculate the moment of the HDX, add them together to get the new moment. Divide by the new weight to get the new CG. In daily use, you want to stay within the limits at all times. Some pilots forget to check the cg calculated for low fuel (landing) configuration. In many RV’s the cg will move aft as fuel is burned.
 
Santi

You can create 4 limits

1. Empty weight at forward limit
2. Gross weight at forward limit
3. Empty weight at rear limit
4. Gross weight at rear limit.

This will create the w&b envelope.

Yes use the Vans figures
 
Remember you don't need to futz with a scale when the tail is elevated.

1. Weigh in 3-point attitude, record weights for each wheel: Left_A, Right_A, and Tail_A
2. With mains still on the scales, lift tail until canopy rails are level.
3. Record weights for the mains: Left_B, Right_B
4. Calculate Tail_B = (Left_A + Right_A + Tail_A) - (Left_B + Right_B)

Use the B values in your W*B calculation.

A variation on this that is less stressful, it's not much fun if it rolls off the scale. Chock the mains when you lift the tail and weigh the tail.

1. Weigh in 3-point attitude, record weights for each wheel: Left_A, Right_A, and Tail_A
2. Remove scales and chock the mains, lift tail until canopy rails are level, with scale under tail wheel.
3. Record weight for the Tail (Tail B)
4. Calculate (Left B + Right B) = (Left_A + Right_A + Tail_A) - (Tail B)
 
A variation on this that is less stressful, it's not much fun if it rolls off the scale. Chock the mains when you lift the tail and weigh the tail.
I neglected to mention chocks but I assumed you'd be chocked when in 3-point as well... Then when lifting the tail it won't move. You can subtract chock weights later too.

1. Weigh in 3-point attitude, record weights for each wheel: Left_A, Right_A, and Tail_A
2. Remove scales and chock the mains, lift tail until canopy rails are level, with scale under tail wheel.
3. Record weight for the Tail (Tail B)
4. Calculate (Left B + Right B) = (Left_A + Right_A + Tail_A) - (Tail B)
This works, but has two issues: One, you lose the left-right balance information, which you may or may not want. Two, it requires futzing with a stand, spacers, and scale while the tail is raised, which was the entire point of doing it the other way around. Lift tail, read weights off front, drop tail. With one helper on each main wheel scale, the tail only has to be up for ~10 seconds... No stands, spacers to adjust level, or scales to drop.
 
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