OK the attempt to post the information as it was, was a big failure. wrong button no doubt. so i will just type it here word for word and have a go at the small drawing. i do not know who prepared this but i assume that it was part of the data package that had to be supplied when the lazair was presented for approval in 1986 when certification and compliance became mandatory here in Australia. (good luck)

DETERMINATION OF CENTER OF GRAVITY

POSITION FROM FIRST PRINCIPLES

it is possible to determine whether the C OF G is in aproximatley the correct position simply by checking the load on the tail spreader bar T11. However, doing this makes a number of assumptions about the positions of the wheels in relationship to the wing mounting brackets.

The following procedure will allow you to determine the C of G position exactley in the relation to the wing. For normal flight characteristics it should be between 30 and 38 cms back from the leading edge.

1. With the pilot seated in the normal flying attitude, the fuel tank half full, and the aircraft fully rigged for flight, place the hook of a spring balance under F4 or a pair of bathroom scales under the tail spreader T11.

2. Raise the tail until the fuselage tube T23 is horizontal (spirit level). Record the weight shown on the balance

See note (1)

3 With the fuselage held in the same horizontal position, drop a plumb line from the front assembly(the one that pushes into the very front of the fuselage tube). Measure the horizontal distance from the plumb line to the centre axis of the axil tube- usually about 8-12cms.

4 Measure the total length of the fuselage tube T23 from F4 to the front fitting from which you suspend the plumb line (Normally close to 295.5 cms).

CALCULATION

A. Weight W = Wt of aircraft plus pilot

Add your own weight to the empty weight of the aircraft. you may assume 140lbs for the series 1 Lazair (63.5 kilos).

Then G = distance C of G is behind wheel axis calculated as:

Load measured at tail x distance x - y

OVER

Total Weight W

The answer should be a small number(about 0-5cms) if it is much more you may have a C of G problems.

B. Add distance calculated above to the distance (y) measured earlier.

C. Add a further 24cms to this total - this being the distance from the front wing mount to the leading edge of the wing.

D. The total in © above is the distance from the leading edge of the wing to the C of G.

Note 1

it should normally be necessary to lift the tail. If you find a tendency for the aircraft to sit nose down, ie you have to hold the tail DOWN, the Cof G is in FRONT of the axle, and you need to make some changes to the calculation:-

1. Calculate G as given above in Calculation (A). the answer is the distance the C of G is IN FRONT of the wheel.

2. SUBTRACT this distance G from the plumb line to the axle distance "Y".

3 To the number calculated in (3) above is the distance from the leading edge of the wing to the C of G.

hope this provides some entertainment while you are waiting for summer..