Building a Nieuport 11...

[Frank Giger]

That's exactly what I'm building - a gas cap. The copper tube goes through the holes top and bottom of the plastic bit, and a brass rod with cork on the bottom goes through it.

The cap won't be immersed in gasoline, but I'm going to do a tolerance check for it because of fumes. The white plastic joiner bit fits into the top of the fuel tank neck:



Let's revisit this picture because I'm mucking things up in text:



Left to right:

Tube for the rod to slip through.
Brass rod.
Caps for the ends, which the tube will be fixed to and centered by means of washers.
Plastic coupler that forms the body of the gas cap. It fits the tank filler tube perfectly!
Cup of coffee because, you know, coffee.

I'll also find a gasket to go around the coupler where it meets the filler tube just to be pedantic. I'm not afraid of the gas cap coming out, as it's seating inside the filler tank by about two and a half inches. The kind of turbulence required to pull a gas cap two inches out of the filler neck of the tank will mean that the gas cap will be the least of my concerns!

[pittsdriver3]

My bad, I thought you were using the PVC for a float. It does need to fit tight as in turbulence you will have the pressure of the fuel trying to pop it out of there. Does the tank vent through the cap or does it have another source? Don

[Frank Giger]

Plastic floating in gasoline on an airplane....I would object, too!

Tank vents through the cap. The brass rod fits loosely through the tube (but not so loose as to bind) so I'm not overly concerned about pressure - the fitting fits well; neither snug nor waggling around, though it's on the loose side more than the snug. That's a good thing, as if the PVC does manage to swell over time it has some give.

The other reasons for not worrying too much about pressure is that I rarely find any reason to fly higher than 2,000 feet AGL. One cannot properly enjoy the sight of a cow grazing any higher than that.

[Frank Giger]

Here's said gas cap assembled:



It needs the weekend to sit and the epoxy to completely cure before I do anything else with it, but here it is on the aircraft with the brass rod inserted:



Side sheeting is screwed onto the aircraft:



They're bog standard #10 sheet metal screws, and I did a variation on the theme the KC Dawn Patrol guys did on their Nieuports for holding them.

Conduit holders did such a great job on the flooring that I went that way for the sides as well. Clips hold the screws within.

[pittsdriver3]

What I'm more concerned about is in turbulence or negative G the gas could slosh up the fill tube and blow the cap off. A big volume of fuel forced up that smaller volume fuel filler can exert some pretty high pressure on that cap. The fuel cap in a Pitts I flew was a thermos style cap with a locking lever. It fit pretty tight even without the locking lever down. I forgot to lock it one day and as I rolled inverted with less than 1 G it blew off. It is surprising how much fuel sucked out while flying back to the airport. I'm glad it was a S2B with a canopy. Don

[Frank Giger]

Ah, I see what you're trying so patiently to explain to me. While rolling is out (she's strickly a utility aircraft), I can see where strip induced turbulence, also known as test landings,* might send a geyser of fuel up the small neck.

So I'm going to put a swivel latch that fits around the neck of the filler cap. Push it one way and it clears the hole and one pulls the filler cap out; once back in place, pull it the other and it goes around it, keeping it from popping out. I did some back of the enevelope drawings and it should be easy to manufacture.

* Lesser pilots and uniformed observers have described this manuever as a "bounce," but that's their problem, not mine.

[edit]

This, btw, is precisely why this build thread exists - to trouble shoot my decisions and keep me out of trouble. Many, many thanks!

[Frank Giger]

Okay, center wing section stuff!

I've seen this done a bunch of ways, so I naturally tried something a little different.

First I took some sheeting and trimmed it to fit the upper and lower sections pretty well, and then covered it as one big long piece.

Then I shrank the fabric (which is doubled) around the center section to match the sweep.



Four inch industrial Velcro went along the edges to hold everything down, and she was painted.



I have to trim up the sheeting at the very back a little to clean it up, but there's a flap from the lower section that comes up to join them at the back and make it look better.



Kind of hair raising to take an exacto knife to fabric, but those holes have to go in if I want the thing to get on the aircraft!



One of the things that continues to amaze me is how tough the fabric is - I know it's just polyester cloth, but once sealed and painted it has the consistency of leather more than cloth.

[Frank Giger]

Well, as many triangular shaped bits of curled cowling shrouds piled up in rejected layers of my failure to grasp the intent and methods suggested by Robert and the maddening illustration in the plans, I stopped repeating the same effort that was ending in the same results.

Pictures later, but the problem was that I could get the curve to the firewall or I could get the flare from firewall curve to the flat sheeting, but I just couldn't do both. Not with any sort of satisfactory result.

I just lack the skill to properly "wad up" the aluminum to get it in the right shape.

So I was sitting there drinking coffee and trying to find out where the latest source of human red sauce was leaking out (bottom of left forearm this time) and suddenly stomped up to the aircraft to let it know my frustration with it.* So I put my left hand on my hip in a fist, squared up to it, and motioned at it with my right hand like a butcher knife (old Army habits die hard, I still can't point with one finger).

"Alouette," I admonished, "you're starting to give me the ass. What say you?"

My little lark just sat there, saying nothing, and then a little breeze blew the front flap of the Wonder Tent. A ray of sun struck the firewall right at the edge. The crimped edge. The one that was made the aluminum L shaped sheet that holds the clamps for the cowling to fit the curve of the firewall.

Ah, I think, she's a smart little bird, isn't she? And she just wants her wings back.

Back to my template and a fresh piece of aluminum. Adding an inch to the edge where it meets the firewall, I cut it and annealed along my marked lines.

Bending a nice edge by hand using a flat bending tool (it's too big for my brake), I went to work with the crimpers. Soon I had the curve to match the firewall, tweaking it here and there to get the fit right. A little bend past ninety degrees on the curve and she matched to the side sheeting pretty well.

Hmmmm, I'll put a crease on the back side where the rivets go to hold it to the sheeting. Done. And presto, the flare to the open bottom magically appears and it lays down nicely.

* I think most builders of things become animists of one kind or another. Intellectually I know it's just a machine - one with just eleven moving parts (not including the instruments on the panel) - but the other parts of me like to sing to her.

[martymayes]

You should leave that UPC label attached to your fuel "gauge" and paint it to look like a tricolour flag. When the flag gets to half mast you know it's time to start looking for fuel.....lol

[Frank Giger]

That's actually not a bad idea!

I cut the fuel cap retention piece late this evening...don't know if it'll work or not, so no pictures unless it does!

On to stuff I can show pictures of!

Okay, so this is how not to make a cowling cheek:

It's a floppy mess that would never fit right under the cowl and prove to be a nightmare lining up with the holes for the fasteners. This was one of my better attempts as well.

Bonus plan: it bulged out quite a bit to where it ballooned past the cowling edge.



So, as I wrote earlier, I had an epiphany of sorts to just put a lip on the leading edge, bend it over, and crimp to bend to fit the firewall. Here's the right side in profile.



And here's the left.

I've got some minor tweaking to do on it, but it's on and true to the firewall curve and lip.



I couldn't resist and threw the cowl on it for a test fit!



Because the cheeks are a little springy on the small flare from firewall to rivets on the side sheeting, I secured the flange in place with a sheet metal screw top and bottom.

In other news, the prop arrived as I was typing this update - holy smokes, what a piece of art!