Moment of truth! Weight and balance has been a worry of mine since buying my angle valve engine. The 200hp Angle Valve engines are about 30lbs heavier than their parallel valve cousins. This means you need to make an attempt to put weight aft. Absolutely put the battery in the back. I put my ELT back even further. Hopefully this combination would result in a good CG.
Doing the weight and balance isn’t rockets science. Basically, you level the aircraft in flight attitude on 3 scales. Then makes sure you measure each of those three points (main wheels, and tail wheel) to the datum. For Van’s aircraft the datum is arbitrarily set at 70″ forward of the wing leading edge. To get those measurements, I put two plumb bobs on each wing leading edge. I then measured 50 (not 70 simple because I didn’t have room) forward from several points on that line. I then drew a line across and measured backwards to the main landing gear and the tailwheel. This provides the arm. Put those in a little table. Some math. Boom. CG determined. You can see my results below.
Here are my results. Turns out my empty weight is 1116. Which isn’t fat, but its not skinny either. With another 25-30 lbs of paint yet to arrive, I’m maybe a little heavier than I had hoped – but on the plus side I only weight 140 lbs, so I’m still ahead of most pilots! My CG is, predictably forward. In my case, my empty CG is forward of the forward CG limit, but as you can see, with even a lighter pilot, you can stay within the CG limits from fuel fuel to empty. Caution should be taken, particularly for pilots of my weight category to not exceed the forward CG. In other words. When solo – put the baggage in the back!
Am I happy with my results? I was hoping for a little less weight, and a little more aft CG. That said, I would call my weight and balance pretty average for an RV-8 with an angle valve engine. There are a good number of folks with higher weights and more forward CGs, but the same is true for less weight and more aft. So, yeah, I’m happy.
Here are the total results of my weight and balance calculations. Additionally, I have included the examples required for submission to the FAA as part of my Airworthiness Application.
First we have the empty weight and CG calculations resulting in an empty weight of 1116 and a CG of 77.13
My first example calculation shows a standard loading with two standard weight pilots and full fuel.
Next, the same loading down to minimum fuel.
Most aft CG is a required submission for your weight and balance with the airworthiness application. Basically you are showing what weight configuration will put you at the aft limit. Max out the stations that are behind the aft CG limit, use standard pilot weights, and fuel loading that creates the worst condition of CG. In this case you can see that with two standard pilots, maximum baggage weight of 75lbs in the aft baggage compartment, nothing in the front baggage compartment, and empty fuel, we just hit the aft limit. Takeway: N22UP is forward CG sensitive. It takes a lot to get towards the aft limit!
Most forward CG is also a required submission for your weight and balance. In this case, you want to use a standard pilot, and maximize the stations forward of the forward CG limit. My results show that with a standard pilot, and no fuel you can carry 23 lbs of baggage in the forward baggage area provided the rear seat, and aft baggage are empty. Of note, at my weight of 140lbs, you can only put a couple pounds in the front baggage compartment and run the full fuel range. Takeaway: Again, forward CG sensitive. Lighter pilots must be cognizant of forward loading.
The final weight and balance CG required submission is the weight and balance you will use for flight testing. In this case, we use my weight of 140 lbs, 30 gallons of fuel, and some weight in the rear baggage compartment to bring the CG into the flight test window. The optimum CG for initial flight testing is 1/3 to 1/4 rear of the forward limit.
Not related to weight and balance, but I bought a new toy. I’m a fan of Project Farm on Youtube. Project Farm does excellent testing of tools and shop items. He did a review on cordless screwdrivers. I had decided I needed a good lightweight solution for installing and removing all the panels needed for inspection. As I have converted the vast majority of my removable panels to Torx screws, I also wanted some new Torx bits and a holder on the screwdriver to make the process as quick and painless as possible. I also wanted 2 speeds, and a good torque clutch to avoid damaging nutplates and screws. Based on this Project Farm Review – I chose the Metabo HPT. I’m very happy with the purchase!
Little details here and there. First, my N-Number stickers arrived from Aircraft Spruce. Needed to get those on. Pretty quick and easy. I’ve gone with the smaller numbers for now, but my paint scheme will include 12″ numbers so that international travel doesn’t require any temporary stickers.
I also started reinstalling all of the fairings, inspections panels, baggage compartment panels, seats etc. Everything needs to be on the aircraft for weight and balance, which at this point is essentially my last remaining item for airworthiness inspection.
Not pictured here, but during my reinstallation of panels, I found a couple gripes. First there were 4 rivets that were missing from aft of the rear access panel. There were also 4 bolts that needed to be installed in the gear towers. I had removed them for installation of the vent lines and gear hardware. There was also one bolt that required final torque. They were, of course, difficult to get to, but I got them installed and torqued.