I spent yesterday (13th January 2012) knocking together a generic RV-4 weight and balance spreadsheet. I derived the sheet from the one available from my website for the 3. After I finished the sheet I started playing around with the numbers and I found that it is possible with a certain set of parameters for the c of g to migrate outside the rear limit with fuel usage. There are simple safeguards however to prevent this. Removing any and all weight from the rear baggage area helps but the c of g must be checked against fuel usage so it stays inside the required envelope. Using the optional front baggage area does help a lot to keep c of g within range. I am talking here of rear seat loads of 250 to 300 lbs which are very unlikely but still have to be considered.
Here is a link to the generic RV-4 weight and balance spreadsheet:
RV-4_WeightAndBalance_Calculations
Normal operation with one on board, leaves the c of g well forward and near the front limit with no issues on fuel usage bringing the c of g outside the envelope.
It is virtually impossible to do aerobatics in the 4 with two people on board the Aerobatic Gross Weight of 1375lbs sees to that. I will not be deviating from this “Set in Stone” weight and fuel WILL be considered in my aerobatic c of g calculations.
I am going to use the 4 as a single seater mostly with an option of the occasional second seat for pax weighing no more than 170 lbs. Used as a single seater and provided I have no more than 100lbs of luggage divided between the rear seat and the baggage area, I will not have to give c of g a thought. When pax are involved, the c of g calculations will be done before the flight to ensure c of g remains in the required envelope.
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