Dimensions at W&B

Just a question for other RV-6A builders....

How close to the dimensions for W&B shown in the plans were you?

My numbers seem to be nose gear 1.5 inches forward and main gear 1/2 inch aft with reference to the numbers in the instruction figure sample.

How do your numbers compare? Are mine typical?

I also asked another local builder and he said he didn't measure his plane, he just used the instruction manual numbers, which surprised me a bit.

They didn't match for mine either.

Sample shows 28.56" for nose gear, I measured mine to be 29.50".
Sample shows 84.25" for mains, I measured mine to be 85.06".

I suspect at least some of the deltas can be attributed to weight and weight distribution of the aircraft i.e. I'd expect the nose gear to flex forward slightly when the aircraft has an IO-360 and a Hartzell vs. an O-320 and a Catto for example.

I've run into this on all my airplanes. The -8 was the closest, but all my "rod type" gear airplanes have been all over the place. They are typically different from side to side as well. I average the two dimensions and apply the total weight to that one arm location.

Toobuilder said:

I've run into this on all my airplanes. The -8 was the closest, but all my "rod type" gear airplanes have been all over the place. They are typically different from side to side as well. I average the two dimensions and apply the total weight to that one arm location.

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That's sort of what I expected, and why I was surprised at the local builder who just used the book dimensions.

I must have received good gear weldments, my L to R difference was only 1/16 inch.

My numbers were -

Nose - 30.03
Left - 84.68
Right - 84.62

Yep, that's pretty tight. My Hiperbipe was .500 different side to side. Reviewing the Rocket's W&B card shows it the same (rounded to the nearest tenth).

One of my pet peeves is "getting close" with the initial W&B. This is something that lives with the airplane forever, and half a$$ing it the first time means it is probably wrong forever. I have a set of pad style digital scales available to me and I weigh the airplane 3 times, rotating pads each time to get an average (usually all are within 1 pound). This is one of those things that you don't shortcut.

I measured my RV-4 carefully and my positions where off too. And left/right as well a little. When I did the moment on the delta is was insignificant.

BruceMe said:

I measured my RV-4 carefully and my positions where off too. And left/right as well a little. When I did the moment on the delta is was insignificant.

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I think it's more sensitive for the -A models.

From a sample spreadsheet - 1.5 inch error in the nose gear dimension is almost a 1/2 inch change in the empty CG location.

Left and Right gear dimensions should simply average out as Toolbuilder said..