Thorp Air Command - T18.net

I'm posting this on behalf of Bill Williams

This is how Bob and I did ours. We made a door and a "S" type hinge and used a Hartzell latch. I bought the neck from Wag and welded a plate about 1/4" from the top to allow for clearance for the cap. The cap is a non-vented radiator cap. I riveted it to the tank and sealed with PRC.

Bill

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

The following web page describes how I converted my "Thermos bottle" gas cap to one with a positive mechanical lock, no welding required.
http://bfinney8.home.comcast.net/~bfinney8/thorp/gas_cap.htm

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

"Tanks!" I'm getting ready to put in a new filler neck as well.

Image Insert:

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In theory, theory and practice are the same. In practice, they are not.

I went with ACS Products Co. Updated thermos unvented cap. It did not fit well. The bottom plate and lower part of the main body of the cap were too big in diameter to fit the hole of the old bung.
When I de fueled old Feisty to weigh it (after changing the starter) I noticed how much junk & crud was in the bottom of the tank.
Today I addressed that. I swabbed out the last of the gas & warmed the tank with a milk house heater in the cockpit. When the tank was dry, I disconnected the fuel line to the fuel strainer/drain and blew it back with compressed air to make sure it is clear, then ventilated the tank with the out end of a shop vac. Then I vacuumed out the junk.
During this interlude I also used a flap wheel to slowly sand out the fuel tank bung until the new cap fit well.
I feel much better about the fuel system with it cleaned out, the tank valve tested, and the flow rate checked. And the new cap fitted and installed.

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Scott Emery
EAA Chapter 326
T-18 N18TE

Here's a photo of my style cap; I think its a marine type cap with an oring seal, for what its worth. Agreed with Shipschief, I couldn't believe the amount of crap in the bottom of my tank. Dick, that is a sharp looking tank compared to mine, nice welding beads. Mine looks like someone welded it with a broken zig zag sewing machine.

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Chuck Kincer
Richmond, Me
575CK
KIWI

Chuck, was your camera drunk when it took those photos? Can you take them again? Do you have part numbers?
Cubes

Chuck : It does look like a boat fuelin filler cap ! Also looks like it set in place with epoxy ? With your new tank I would recommend a flush fitting cap with the top skin . No need for a scupper and no fumes in the flight deck . BOOOM !

RB

Cubes; I think my camera is innocent; me however.........Let me try again. As far as part numbers, I'm having a new tank fabricated and sent my old one for "hole" location to the fabricator. I can ask if there are any reference numbers; he may actually read this thread.
Rich; yep, all epoxy...everywhere.

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Chuck Kincer
Richmond, Me
575CK
KIWI

That is one nasty lookin tank ! Good to hear all the passengers survived ! I know the new one will be AJ Squared Away ! BOOM !

RB

It surprises me that inspecting the tank interior wasn't on the condition inspection checklist! It should be on everyone's list.... just shine an LED flashlight in there and have a quick look.. no biggie.

I had a film of grunge in mine from Mogas residue, but no build-up of debris. However, I did find some red stick-on letters curled around the fuel strainer. They came from the fuel door, which at one time said "100LL 29 GAL."

BTW that vinyl vent line on my tank was as hard as a rock. I'll put rubber on it when I put it back in.

D

T-18 tanks are unique, being inspect-able. I can see the entire bottom of it from the fill hole.
With a piece of wire, I can lift and lower the fuel gauge float and I can see the finger strainer in the bottom of the tank.
So when I bought the plane last year (9 years sitting with mogas in the tank) I naturally cleaned the tank. Along with rebuilding the fuel strainer/drain and inspecting everything.
The fuel gauge assembly was quite rusty, and over the hours of flight, it dropped a layer of rusty looking sand into the bottom of the tank. (I'm amazed the thing still works!)
I have a nagging feeling that aircraft tanks which cannot be looked into because of their shape, baffles etc. will have junk in the bottom.
Anyway, when I de-fueled it to do a new weight & balance, I saw the junk.
Dan, you make a good point. Especially because T-18s have one tank. It is easy enough to syphon out the fuel and inspect the bottom and the finger strainer.

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Scott Emery
EAA Chapter 326
T-18 N18TE

Bruce, you did a good write up on your fuel tank, the filler you installed looks good and so does your Craftsmanship on the doublers and the lid on the fuse. Very nicely done....Dan

Fluid lines in the cockpit . Dick has a good point with his tank and the nylon/vinyl vent line that hardened and got brittle over time . I used a Goodyear fuel hose for my vent line and it should last longer than me . I suppose you could use an alum. tube from the tank to the floor and couple it with a short rubber connector ? Me thinks I saw someone post this install ? I would also recommend no nylon brake lines in the cockpit and to the brakes . Use SS braided with SS fittings .

RB

Thought I'd add my version of a fuel cap to replace the thermos bottle type. I accomplished this without having to remove the fuel tank. My aluminum fuel tank has a bottom flange that is 1/8 inch thick at the bottom of the filler neck. With about a 20 degree turn of the upper handle activates three cam actuated pins that slide under the flange. These pins are tipped on the top with nylon with a slight taper to lock up on the flange. An O-ring was used to seal the top.

Attached are two photos. Hope they went thru. If not got to the album.

Jim Borg

How cool is that!?

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Bob Highley
N711SH
SN 835
KLAL