Thorp Air Command - T18.net

I'ts been a long time since my T-18, but I do have four RV7 tanks & multiple repairs to RV4 tanks in my history. Van normally sells Flamemaster brand 2 part polysulfide, but I'm pretty sure the Chemseal CS3204 type B is equivalent. Type B means it's thick enough to stay put when you apply it. It's available in various cure times; I like the longer cure times (especially in summer) because it give more time to work with it. The other stuff Spruce sells may work just fine, but I don't have any experience with it.

If you're an EAA chapter member, I'd suggest asking around before ordering any. It won't take very much at all to do two fuel cap rings; someone may give you what they have left. If you keep it in the freezer, it will last for years (decades?) past its expiration date.

Charlie

I'll try to stop blabbering, but I should make clear I know it's the PIC's responsibility to make sure the fuel cap is secure. Cubes new cap setup just makes that a whole lot easier.

Shack
N921JK

Last comment - no one mentioned I was blabbering. I was in sales for 20 years after being a field engineer for over 15. Sales job will mess with your head. I'll keep it simple in the future.

Shack
N921JK T-18C

Well, I finished the install today (and shipped 4 packages!). Lessons learned..
I was completely focused on not allowing ANY aluminum chips into my tank. To that end, I think I succeeded. But I made life hard for myself. I did the process I outlined earlier. Here is what I would change next time.
1) Use tape around the perimeter to make sure the ring fits tight.
2) Drill one hole all the way through the tank flange using a rag and grease to catch shavings.
3) Carefully remove the ring trying to catch all the shavings.
4) Tap said hole
5) Drill out ring for screw clearance in that one hole
6) Reinstall ring with a screw tight.
7) Repeat 180 degrees out
Reinstall ring with two screws tight
9) Drill remaining holes
10) Tap, proseal, and install
The 4/40 screws require precision that I didn’t have with the ring removed
Cubes

Here are some pictures before I cleaned it up.
Cubes

More.

Last.

Cubes

Cubes looks like that is going to work pretty well. I was worried that you would have enough meat (edge distance) for the drilled and tapped holes but it looks like it worked pretty well. Thanks so much for sharing these install pictures.

I have been thinking about how to redo my scupper , I was planning on jbwelding or prosealing an aluminum strip similar to what looks like a rubber strip on yours. Having seen yours it might be easier if I changed that aluminum strip to rubber. Any idea what yours is made from maybe a weather stripping of some kind?

Thanks again

Dave

Yep. It’s just 1/16” rubber….not even fuel proof. It doesn’t see enough fuel to worry about it. I would use Proseal. This was my first time using it. I had some local help.
Marty, use the 1776 formulation. If you google the different types Spruce has, this is the one for fuel tanks. Ask around your airport. I’m guessing that someone has some they will let you use. It doesn’t take a whole pint..maybe a thimble full is enough.
Cubes

I have had some luck using Marine-tex from West Marine in some fuel related applications.

_________________
Bob Highley
N711SH
SN 835
KLAL

When I installed my Newton Aero 400 gas cap in 2008 I used Permatex #2 Form-a-gasket, it's similar to Proseal, fuel and oil resistant, seal is still tight as far as I can see.

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

When I installed my Newton Aero 400 gas cap in 2008 I used Permatex #2 Form-a-gasket, it's similar to Proseal, fuel and oil resistant, seal is still tight as far as I can see.

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

I finished my fuel caps. Just followed the same process Cubes used, 4-40 tap, screws and proseal. Here's a photo of my main tank completed, didn't get a pic of the aux tank. The other picture is the 'tool' I used to keep shavings out of the tank. I just bent up a piece of aluminum and covered it in grease, wiping off the shavings and regreasing after each hole. I also dipped the drill bit in grease before each hole.

This was an easy project but took longer than expected because of being extra precise on the hole placement and keeping shavings out of my tank. I suggest getting an extra tap to have on hand, I broke one and it delayed me a bit.

This is the fix to the biggest frustration on my plane. Thanks for making this happen, Cubes!!

Marty

_________________
Marty G
N50LE
YouTube Channel
martygrosse@yahoo.com

I finished my fuel caps. Just followed the same process Cubes used, 4-40 tap, screws and proseal. Here's a photo of my main tank completed, didn't get a pic of the aux tank. The other picture is the 'tool' I used to keep shavings out of the tank. I just bent up a piece of aluminum and covered it in grease, wiping off the shavings and regreasing after each hole. I also dipped the drill bit in grease before each hole.

This was an easy project but took longer than expected because of being extra precise on the hole placement and keeping shavings out of my tank. I suggest getting an extra tap to have on hand, I broke one and it delayed me a bit.

This is the fix to the biggest frustration on my plane. Thanks for making this happen, Cubes!!

Marty

_________________
Marty G
N50LE
YouTube Channel
martygrosse@yahoo.com

I wish it was my idea. I just worked with the machinist to refine his idea. I love my new cap. I’ve got three left if anyone wants one.
Cubes