1999 Weight and Balance Calculations

Source: 1999 Beartracks, Bob Barrows

*Hold this dimension for all engine installations unless weight and balance calculation problems are encountered

Bearhawk N33RB

Aft Sample Weight Arm Moment Forward Sample Weight Arm Moment
*Main Gear R 600 -1.63 -978 *Main Gear R 600 -1.63 -978
*Main Gear L 596 -1.63 -970 *Main Gear L 596 -1.63 -970
*Tail Wheel 75 199 14925 *Tail Wheel 75 199 14925
Front Seats 400 14 5600 Front Seats 200 14 2800
Cargo Area 530 57 30210 Cargo Area 0 57 0
Fuel lbs. 300 24 7200 Fuel lbs. 30 24 54
Totals 2500   55987 Totals 1500   15829
Gross Weight 2500     Gross Weight 2500    
C.G. Range 10.5″ – 22.5″     C.G. Range 10.5″ – 22.5″    
C.G. Range 16% – 34%     C.G. Range 16% – 34%    
C.G. Aft 22.4″     C.G. Forward 10.5″    
C.G. (MAC) 34%     C.G. (MAC) 16%    
Empty Weight – 1270* Empty Weight C.G. – 10.2″*

*As per weigh in of Proto II N33RB on 9-9-99

Note: Empty weight includes: 10 quarts oil, O-540 Lycoming Engine, no electrical system, no rear seats, utility door system and constant speed propeller (3-blade composite).

Forward C.G. = 15829/1501 = 10.5″     10.5/66 chord = 16%

Rear C.G. = 55987/2500 = 22.4″     22.4/66 chord = 34%

Do your first test flight with the c.g. between 13.5″ and 18.5″.

N6890R Weight and Balance

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Noodling Bearhawk Weight and Balance, Part 2

Source: 2007 Q1 Beartracks, Rob Gaddy. Click here for Noodling Bearhawk Weight and Balance, Part 1
Before we begin, I made an error in Part I of this article. In Figure 3 the weight on the main gear should be 1,196 pounds, not the 1,271 pounds shown. The 1,196 pounds is just the measured weight on the main tires, the 600 pounds for the right gear plus the 596 pounds for the left gear. Since we were summing the moments around the main gear, the error did not affect the calculation.

This article is available for purchasers of 2007 Beartracks access. Click here to purchase access or validate your prior 2007 subscription. Multi-year bundles are available here.

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Noodling Bearhawk Weight and Balance, Part 1

Source: 2006 Q4 Beartracks, Rob Gaddy. Part 2 is in 2007 Q1.
What do I need to know about Bearhawk Weight and Balance? If you are still reading I will assume you have an interest in the subject also, so come along for the mental trip and we will see if we learn anything.
Let’s start with the basics; here is our Bearhawk, figure 1. Let’s assume we have finished it but haven’t flown it yet. It has all equipment installed and engine oil, but not fuel. I want to know two things, first what does it weigh, and second where does it balance, hence Weight and Balance or W&B. To answer these questions let’s put some trustworthy scales under each tire to find what the weight is on that particular tire. Let’s level the fuselage, it is important later. We will use the W&B for N33RB as given in the October 1999 Bear Tracks, page 6 for an example.

This article is available for purchasers of 2006 Beartracks access. Click here to purchase access or validate your prior 2006 subscription. Multi-year bundles are available here.

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