Step 8.1, Firewall

The RV series of aircraft and most others constructed today, employ a construction  method called semi-monocoque.  Don't be put off just because the word sounds French.  Yes, the word monocoque is French.  But it is also Greek, and that is the part we can understand.  It turns out the French use the word coque when they mean to say shell, so monocoque simply means single shell.

To construct in truly monocoque fashion is to make an object like a soup can in which the exterior skin provides all of the structure for the object.  In contrast, the most commonly used alternative to monocoque is the internal truss method where a rigid frame is constructed and then covered with a non structural material such as fabric.  Monocoque construction is also known as stressed-skin construction because the outer shell carries all of the structural loads. The RV uses a semi-monocoque method which is a compromise between using an  internal trusswork like the fabric covered airplane and having to use a very rigid, and consequently heavy, material to produce a load bearing outer shell.

So semi-monocoque construction uses some internal structure for high load areas, but most of the forces are carried through the thin and very light aluminum skin.  It is this blending of methods that optimizes the strength/weight ratio and has made semi-monocoque the aircraft designer's method of choice for a strong and light airplane.

Now that the fuselage inventory is complete it's time to get going.  Van's build manual begins construction at the firewall which seems perfectly sensible to me.

The firewall is a large piece of stainless steel that represents the cross section of the airplane just behind the engine.  Despite being heavier stainless steel is used at this location to protect the occupants from a potential engine fire because its melting temperature much higher than that of aluminum.  In the picture above the first step is to debur the very sharp edges.

Fabrication begins with some flanges that are cut from 2" angle and then trimmed down on the bandsaw.

The final step is to smooth the rough edges with the belt sander and finish with the Scotch-brite wheel.  Then the firewall structural members are test fit and match drilled.  This view is from the back side, which is what you would see if you were to look under the control panel.

Once the parts are drilled, they are deburred on the top side and counter sunk on the bottom to mate with the firewall holes which are then dimpled.  The result is flush rivets on the inside of the engine compartment.

Roxy chews.  Trina sleeps.  Carol deburs.

After deburring, the aluminum parts go to the paint booth for priming.

While we wait for that to dry, the stainless steel part is measured for some of the holes that will allow engine control cables to go forward and cabin heat to come back.

With the parts primed, they are staged for final assembly.

This is the lower corner weldment that will tie the fuselage to the engine mount on the other side.  There are only 16 rivets here.  Hmmm.

And here it is.

Fire wall done.  Anything good in the fridge?

Step 8.0, Fuselage arrives

Over the last eight weeks that I've been waiting for the fuselage to arrive I've not been very busy with airplane stuff, although I did manage to get the wing tips in order.  I think most people put that job off to the end of the project because it has no dependencies and it's not really all that much fun.  At least I didn't think so.  But now the long wait is now over as my fuselage arrived just in time for the weekend.

The box arrived via Conway Freight, in excellent condition, COD.  I had the driver meet me at the end of my road because of the fiasco with last big delivery (wings). It seems that I neglected to tell Fedex Freight that there were low overhanging limbs over my road.  My bad.  When the Fedex driver got to my house, he was not in a charitable mood to say the least.  And I think the less said about that, the better.

So this time I decided it would just be better to meet them with my pickup and do the transfer out on the highway.  We had no trouble getting the box into the bed of my Ranger, but when I got it back to my shop I realized that it might be a little more difficult to unload it by myself.  The shiping weight was 358 pounds.  Fairly heavy, yes, but I would only have to lift 179 at a time.  

Once the crate was safely lowered to the floor it was a little past time to go drink a beer.

The next 10 or 12 hours would be consumed with doing the inventory.  I think out of the hundreds of parts in that box there is only one we cannot account for.  I think that's pretty good.  It's a little tedious doing the inventory, but the process makes one familiar with each and every part before it's actually needed.

 And on it goes, part by part...

That's the firewall in the foreground and Carolina working on sub kit #19 in the background.  Van thoughtfully provided these convenient cushioned floor mats to ease the burden of standing still on concrete for many hours.

It was actually quite surprising to me how many parts there were.  Eventually everything was checked and put away.  The bags and the other very small parts go in the roll around parts caddy.  The rest fit on two shelving units with room to spare.

All of the large pieces I stood up along the wall or just laid down on the floor.  Hopefully out of the way.

Although I wasn't too busy while waiting for the fuselage to arrive, my puppy Trina was hard at work.  I didn't catch her in the act this time, but I certainly recognize her M.O.  Oh, and did I mention that the book was brand new, still in the box from Amazon when she found it on our porch, freshly delivered by UPS.  I guess the curiosity was killing her. 

So I tried to smooth out the chewed corner to salvage the book. Fortunately not much of the text was affected.  Her good fortune is that it's just damned near impossible to stay mad at her for long.