Hi All,
I am in the beggining of designing my own slope soarer[8D], and reading some helpful info, when i came across the term 'Moment Arm'[X(],
I learnt about all this sort of stuff a couple of years ago doing basic aeronautical knowledge with some pilot training i did [31hrs, 1st & 2nd Solo](but haven't the funds to continue yet[&o]), and i can't remember what Moment Arm means, I have a feeling it has something to do with weight etc.
Any help would be appreciated

Thanks for any help
'Cheers'
BushBoy

Its the distance between the centre of gravity to the aerodynamic centre of the tailplane.

I think!

Basically to change the moment arm you change the position of the tailplane relative to the wing (horizontally).

Hope that helps, i'm sure someone will post a better description shortly..!

Moment arm is a generic term. It's the distance between an appied force and the pivot point.

It's commonly used in model terms to mean the nose length or tail length. In the case of the tail it's defined as the distance between the 25% chord points of the two surfaces. For the nose it's the front end to the 25% wing chord point. If you're considering spiral stability then I think it's the distance from the 25% chord point of the wing to the same on the vertical tail or it may be the center of area of the projected wing in side view to the 25% mark on the tail. For this last bit it's been a while since I looked at the particulars.

In other matters ksechlers' distance from a force to pivot is proper. For example the moment arm from the CG to the drag center or CG to neutral point, etc.

Weight X arm=moment. From the pivot point on a teeter toter 10 lbs at ten feet = 100 moments. 50 lbs at 20 feet = 100 moments. They balance. "Positive and negative moments." The pivot point on full size planes is called the reference datum point and is located near the nose so that all moments will be positive to allow use of tech manuals for cg computation.Moment arm in purest terms is the distance from the pivot point to the weight or applied force,pressure.
CAZ

excuse me for a MOMENT, my ARM fell asleep

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