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Time for W&B

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drone_pilot

Well Known Member
Not sure where I should post this. Im almost done with my RV-7A. Im planning to finish up the interior in a couple of weeks and then Im ready to begin the initial weight and balance portion of the build. Does anyone in this forum have any aircraft scales in current calibration that they would be willing to rent?

Much Thanks!
 
I just did this, I bought one of those 440 lb postal scales, good for an A model but not a tail dragger. be sure to put a piece of plywood or something to spread the load out, my scale started to bend in the middle with the tire centered on it.
 
Mark Dickens said:
If it turns out that you can't find some to rent, you might be interested in a 550lb weight limit scale I just bought for $40.00 off of Amazon:

https://www.amazon.com/My-Weigh-XL-...ie=UTF8&qid=1477305822&sr=8-1&keywords=xl-550

My plan is to weigh each wheel separately...
Click to expand...

one thing to note I discovered doing one tire at a time, is to make sure that the fuse is absolute level doing it this way, just a 2" change in the nose ht. changed the nose weight 40 lbs!
 
scales

ck with your local EAA chapters as some may have scales. The chap that I belong to has scales for us to use
 
What about accuracy of these scales? I read about their resolution but see nothing stating calibration numbers. Are the lower cost scales linear in accuracy?
 
A word to the wise on the type of scales mentioned above. They don't stay turned on long enough to allow a person to practically weigh an airplane. I have similar scales and found them to be useful, but only marginally so.

The process for weighing is...
- jack airplane above scale
- press on scale to turn it on
- lower airplane wheel onto scale
- wait for reading to stabilize
- write down the reading before the scale automatically shuts off. If you missed it, you have to start over again.

There's no way I've found to be able to weigh all 3 wheels at once, short of using 4 people, one at each wheel and one to operate the overhead crane or underbody jacking system necessary to raise and lower the entire aircraft.

BTW, with respect to accuracy and repeatability, I can't vouch for the exact scale mentioned here, but the ones I have, rated at 300lbs, are very accurate and very repeatable at normal room temperature. They are NOT repeatable at anything other than room temperature as it appears their strain gauges are not well temperature compensated.
 
drone_pilot said:
What about accuracy of these scales? I read about their resolution but see nothing stating calibration numbers. Are the lower cost scales linear in accuracy?
Click to expand...

I got a 660 lb version and the "resolution" is a little overdone.

It displays weight down to two decimal points of a pound - about 5 grams. Those two lower digits are always in motion...:)

I managed to find a local set of race car scales that were non-working. Easily fixed by replacing the internal 6 volt ni-cad battery.

Placing the cheap package scale and the race car scales with its heavy cast parts side by side the difference in robustness is easily seen. :D
 
Canadian_JOY said:
A word to the wise on the type of scales mentioned above. They don't stay turned on long enough to allow a person to practically weigh an airplane. I have similar scales and found them to be useful, but only marginally so.

The process for weighing is...
- jack airplane above scale
- press on scale to turn it on
- lower airplane wheel onto scale
- wait for reading to stabilize
- write down the reading before the scale automatically shuts off. If you missed it, you have to start over again.

There's no way I've found to be able to weigh all 3 wheels at once, short of using 4 people, one at each wheel and one to operate the overhead crane or underbody jacking system necessary to raise and lower the entire aircraft.

BTW, with respect to accuracy and repeatability, I can't vouch for the exact scale mentioned here, but the ones I have, rated at 300lbs, are very accurate and very repeatable at normal room temperature. They are NOT repeatable at anything other than room temperature as it appears their strain gauges are not well temperature compensated.
Click to expand...

I hadn't thought about the automatic time out! In this case, it may be a benefit to have one scale and weigh each wheel separately. I have no doubt that the high end race car scales are a better solution, but they are a LOT more expensive. My plan is to weigh each wheel 3 times and take the average.
 
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