Date:  07-26-2024

Number of Hours:  10

Manual Reference:  26

This is how I approached the weight and balance. I should say ‘we’ as a fellow airplane scratch builder was an enormous help having done it before, and he is better at these thing anyway.

There are two tasks for the W&B. One is to take measurements of the plane, the other to weigh it. Who said it all has to be done on the same day? It was easier to do the measure up first. There are plenty of articles and papers on how to do this.

Here my friend is dropping a plumb bob at the nose, one of various locations on the plane. We then marked them on the floor.

That yellow bit of tape is another one of the locations.

We used a chalk line between marked points which is standard practice for setting up these measurements.

This is a ‘DATUM’ I marked on the plane. The Long-EZ plans tell you how to do the measurements in the POH. The Datum used is kind of a location that would be challenging to measure from when adding new items to get the ‘arm’ or ‘station’. This permanent line is 47.55″ back from the nose and made it easy to set up the W&B extra items.

OK, not exactly my neatest work. These are the raw numbers we ended up with and are critical to getting thing right. Everything we needed was here. Except the weights, that was done nearly a month later.

This is set up on the scales. Someone had made some nice ramps to get the plane on and to prevent overrun at the front. The aircraft is leveled fore and aft at zero degrees and side to side as well. Everything is on the plane for ‘basic’ empty weight. This includes full oil of 8liters and full coolant of 6 liters.

Here is the BEW, it includes a right main side wheel chock of 1.38kg which we take off later in the calculations. You can see it is very close to the same weight on each main. I’m happy about that. My girl is ‘festively plump’ you might say at a tad over 500kg or about 1,100 pounds. I have set the maximum at 995kg, something I can do as the manufacturer. This is well over the plans weight and I have engineering justifications and documents to support my decision.

Frankly, these are just a few shots of the plane. I haven’t seen it with everything on and mostly painted.

The cowls will be painted white soon, a big job.

I may leave the spinner in the carbon black and just clear coat it.

Beautiful nose art, airbrushing by a very talented artist.

This is the ferry tank. I’m yet to decide how I will secure it.

OK, on to the paperwork and calculations. This is a plan I made up and printed before weighing. I wanted to know the exact correct stations for the key items. Things like the PODs effect of the balance needed to be found as well as the effect of luggage in the pods.

We set this up so that we progressively add items making the process easier on weighing day. We did two lots of numbers for BEW. We correctly unstrung the landing gear to remove side forces that distorted the result on the first numbers. The scales only do whole kilograms. This is fine. The process took us only about 2.5 hours to do, if you don’t count lunch.

WEIGHT & BALANCE Results and Workings
I’ve put this all in, just in case someone needs to see the workings. I found it a little hard to do. My skills here are pretty poor, I’m more a big picture guy. I had to think about it for a bit and correct a few errors. You, my friend, are probably a lot smarter.

• Allowable CG range is 97″ to 103″ (all CG distance numbers in inches)
• Weights in Kilograms
• Numbers done 26/7/244 Darren & I @ YMMB RVAC hangar
• Corrected for RHS wheel cock of 1.38kg (this number taken from collected Rt Main data)
• Numbers to two decimal places only
• We did multiple weighings so we could work out our own moments with some accuracy

ITEM	Item WT	TotalWT	Nose	LTMain	RTMain
BEW     8lt oil (full), 6lts Coolant, No fuel		501.62	12	245	244.62
BEW + Oxygen (then removed)	5	506.62	14	246	246.62
BEW + Pilot	73	574.62	56	260	258.62
BEW + Pilot and PAX	168	669.62	69	301	299.62
BEW + Empty Pods	9	510.62	11	250	249.62
BEW + Full Pods (40lbs/18.14kg each)	37	547.62	9	269	269.62
BEW + 60lts wing Fuel (44kg)	44	545.62	16	263	266.62
BEW + (incl 60L Wing fuel) Empty Ferry bladder , associated pumps and hoses	44+6	551.62	17	265	269.62
BEW + Ferry Tank + 40lts (32kg) Fuel	44+6+32	583.62	23	278	282.62

Calculate Center of Gravity (CG)           

BEW	Weight	ARM	Moment
RH Main	244.62	110.65	27,067.20
LH Main	245	110.65	27,109.25
Nose	12	18.65	223.80
Totals	501.62		54,400.25

BEW CG = 108.45″ Moment/Weight = 54,400.25/501.62

BEW + Oxygen (then removed)					5	506.62		14	246	246.62
	BEW	Weight	ARM	Moment
	RH Main	246.62	110.65	27,288.50
	LH Main	246	110.65	27,219.90
	Nose	14	18.65	261.10
	Totals	506.62		54,769.50

The change in moment from BEW to when we added the Oxygen  is 54,769.50 less 54,400.25 This is a moment of change 369.35.

Oxygen Arm= 73.85 Moment/weight = 369.25/5

BEW + Pilot					73	574.62		56	260	258.62
	BEW	Weight	ARM	Moment
	RH Main	258.62	110.65	28,616.30
	LH Main	260	110.65	28,769.00
	Nose	56	18.65	1,044.40
	Pilot	73	Unknown yet
	Totals	574.62		58,429.70

CG = Moment/Weight = 58,429.70/574.62 = 101.68″

We need to know the ARM or “Station” for the pilot so we can use a weight other than 73kg
The change in moment from BEW to when we added the Pilot is 58,429.70 less 54,400.25. This is a moment of 4029.45.

if       WT x Pilot ARM = Moment   then
Pilot ARM = 55.2 Moment/weight = 4029.45/73 

BEW + Pilot and PAX (no fuel)					168	669.62		69	301	299.62
	BEW	Weight	ARM	Moment
	RH Main	299.62	110.65	33,152.95
	LH Main	301	110.65	33,305.65
	Nose	69	18.65	1,286.85
	Totals	669.62		67,745.45

The change in moment from BEW with the Pilot to when we added the PAX (94.9Kg) is 67,745.45 less 58,429.70. This is a moment change of 9,315.75.

PAX Arm = 98.06 Moment/weight = 9,315.75/95(weight of PAX) 

BEW + Empty Pods					9	510.62		11	250	249.62
	BEW	Weight	ARM	Moment
	RH Main	249.62	110.65	27,620.45
	LH Main	250	110.65	27,662.50
	Nose	11	18.65	205.15
	Totals	510.62		55,488.10

The change in moment from BEW to when we added the empty PODS is 55,488.10 less 54,400.25 This is a moment of change 1,087.85.

POD Arm = 120.87 Moment/weight = 1087.85/9 

BEW + Full Pods (40lbs/18.14kg each)					37	547.62		9	269	269.62
	BEW	Weight	ARM	Moment
	RH Main	269.62	110.65	29,833.45
	LH Main	269	110.65	29,764.85
	Nose	9	18.65	167.85
	Totals	547.62		59,766.15

The change in moment from BEW with empty PODS to full pods is 59,766.15 less 55,488.10 This is a moment of change 4,278.05.

POD baggage Arm = 115.62 Moment/weight = 4,279.05/37

BEW + 60lts wing Fuel (44kg)					44	545.62		16	263	266.62
	BEW	Weight	ARM	Moment
	RH Main	266.62	110.65	29,501.50
	LH Main	263	110.65	29,100.95
	Nose	16	18.65	298.40
	Totals	545.62		58,900.85

The change in moment from BEW to when we added the 44kg of fuel is 58,900.85 less 54,400.25. This is a moment change of 4,500.60.

Wing Fuel Arm = 102.29 Moment/weight = 4,519.25/44(weight added in the fuel tanks)

BEW + 60L Wing fuel Empty Ferry bladder , associated pumps and hoses					44+6	551.62		17	265	269.62
	BEW	Weight	ARM	Moment
	RH Main	269.62	110.65	29,833.45
	LH Main	265	110.65	29,322.25
	Nose	17	18.65	317.05
	Totals	551.62		59,472.75

The change in moment from BEW then adding 60lts wing fuel adding the ferry tank and hardware is 59,472.75 less 58,900.85. This is a moment of change  571.90

Ferry Tank Empty Arm = 95.32 Moment/weight = 571.90/6

BEW + Ferry Tank + 40lts (32kg) Fuel					44+6+32	583.62		23	278	282.62
	BEW	Weight	ARM	Moment
	RH Main	282.62	110.65	31,271.90
	LH Main	278	110.65	30,760.70
	Nose	23	18.65	428.95
	Totals	583.62		62,461.55

The change in moment from BEW then adding 60lts wing fuel adding the ferry tank and hardware is 62,461.55 less 59,472.75. This is a moment of change 2988.80

Ferry Tank FUEL Arm = 93.4 Moment/weight = 8,061.3/32

EXTRA ITEMS

For Baggage like water bottles, safety gear and anything thrown in the strake baggage area we need a DATUM that is easy to measure from so we can get our moment arm or ‘station’

The plans DATUM or zero point, is at 113.9 forward of the leading edge of the wings back to the nose. Our convenient DATUM is 47.55 back front the nose.

On the pilot side longeron just back from the panel I have scribed a line and then rubbed in a little black paint to make it easy to see. You can’t miss it. This is an adjusted datum.

To use this, measure from this cockpit scribed line and whatever you get, ADD 47.55″. This is your arm to then multiply by the weight of what you are putting in.

Lets say you are adding a water bottle that weights 2kg behind the front seat. You measure from the longeron line to the bottle, say 30″, then add 47.55 = 76.55 is your ARM, Multiply this by the weight to get the Moment which you would add on your Weight and Balance table

Strake Baggage 77″ from mark arm = 47.44 + 77 = 124.44
Rear of PIC seat 39″ from mark = 47.44 + 39 = 86.44

Here’s a spreadsheet modified from one I stole here… The site has some good weight and balance information relevant to a Long-EZ. Downloads for the ‘unmodified’ excel sheet and a measurement diagram are found there.

If I work out how to get the above sheet live, I will in case one or two people want to play with it. For now you can grab your own copy.

Overall I am very happy how things turned out. I do NOT need nose ballast despite NOT doing a long nose on the airplane. I did try to get all the weight forward that I could during the build and it has paid off. That said, 100 pounds lighter would have been better!