Question about W&B on a 701

I am trying to do my weight and balance figures on my 701. I have built it without slats. On the worksheet it calls for the datum to be taken from the leading edge of the slats I do not have. Should I take measurements from the leading edge of my wings instead or should I add 4.75 inches to that number and use that as my datum.

If I try to use the new datum from just the wing, all of my calculations put my CG way forward. Like empty CG is coming out 3.75" when its supposed to be between 11" and 20". Has anyone else run into this? Should I be using the same datum without slats? Help please. Very near inspection for airworthiness.

Thanks

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Permalink Reply by John Austin 15 hours ago

The datum can be anywhere on the length of the airframe that you want to put it.  If you're using a worksheet that already has some of the moment arms measured and filled-in that used the leading edge of the slat as a datum, then any subsequent measurements of additional moment arms will have to use the same datum.  So, if this is the case with your worksheet, then yes, if you have to measure from a wing leading edge, the difference in distance to the original datum will have to be accounted for/corrected in any moment arms you measure.  Otherwise, set the datum anywhere you want but all new measurements for moment arms will have to be taken.

John

N750A

Permalink Reply by Jim and Amelia Isaacs 12 hours ago

Several threads about this topic in the 701 forum. That’s the good news. The bad news? Well, read through them and you’ll know 😀. Anyway here is one of them. CG datum without slats

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