Door Installation, and weight and balance

Today was all about installing the doors and doing the first weight and balance.

First thing with the doors was to install the arm that holds it up when open. First up was to attach the arm to the existing ball joint

Installing door arm

and then holding up the door at a good height, making a mark where the arm bracket would need to be mounted. A few holes later, and a lot of hand countersinking… the bracket was on each door.

Door arm and arm bracket

And here it is ‘in action’

Door arm installed

The doors still need some work before they can be riveted: file down some forward edges to come back behind the windscreen, and to get rid of the glue on the window.

I’ve tried goo gone, WD-40 and nothing seems to be working. Scott was at the hangar today and was able to get all the paper finally off but there is still a LOT of dried up glue.

Glue on door

Scott thought he was getting a little success with the heat gun and WD-40 so I can perhaps try that next time. I also might try gasoline which maybe has a shot. I did try denatured alcohol on a corner and it took the glue right off. But I read that you shouldn’t use any alcohol with acrylic so I don’t know if I just got lucky, or if there are some circumstances where it is ok. Here’s how well it did

Cleaned a little spot with de-natured alcohol

For a weight and balance I put everything in the plane: seats, cushions, access panels. With the cowling and the doors on, everything that goes on the outside was in place.

Everything assembled and in the plane

For the weight part I used three identical bathroom scales under each wheel and for the balance part I dangled a pair of snips on a string from the edge of the leading slat to get the arm. The arm is the distance from the weight to any fixed point. When you do the weight and balance calculations you will get a centre of gravity position relative to that position.

Weight and balance time

My total weight came in at 710 lbs which is very light indeed, in fact I wonder if something was wrong with the way we did the weighing. A quick look on the Zenith website and the lightest 720 I can find is 727 lbs. How can I be 20 lbs lighter? Am I missing a part? Certainly, my panel is very light, and of course I have the lightest engine but I am still wayyyy off most people who are in the 740-800 range.

Here’s a weight and balance worksheet that shows the empty weight calculation as well as a hypothetical flight in which I take off alone with full tanks and return with half tanks.

Weight and balance worksheet

The CG needs to be between 280mm and 500mm at all times so you can see that in my mythical flight the CG is rearward but well within limits.

I’m off to Japan tomorrow for a week, when I get back I will look at finishing the doors, and I also have to put more vinyl on the bottom of the plane. I may file my airworthiness paperwork the week after since I figure it will take a while and I can work on the “cosmetic” items while I wait.

Ever closer but still some ways to go.