Fuel cap lost

[tailwind]

I have a question. Not having built a tank with rivets, is the sealing material going to seal the holes in the corners or are the holes for clecos and you are welding the corners and seams.

[stinger]

Pro seal does it all, however forming the aluminum in such a way making nice corners . No welding. Stinger

[Bcone1381]

I responded to a similar topic on another thread. Forgive me for repeating myself. A future builder a year from now might appreciate/benfit from my experience.

Before, I wished I had Stinger's or Collin Campbell's caps. My factory fuel cap was very difficult to remove.

Then I replaced the O-rings with a Dash 323 size which is one step smaller. Now I feel the Factory Cap fits just right. Before it was so difficult to remove I felt it was a hazard to me from multiple fronts....lubrication leading to a cap loss, ladder fall risk, damage risk to the cap/tank by using a tool to help pry/removal, etc.

The old O-rings were Dash 324, the new is Dash 323. This change was made through Mark, who consulted Bob. It was a quick, easy mod about the time and cost of a milk shake. I see no need for O-ring lubrication, and once released I gently rock the cab back and forth 2-3 times to work it out of the filler neck. The cap is very secure when I crank it down tight. I like the idea of tool to increase torque of the cap.

Beware, I'm still building so I have an experience issues in this arena.

[AKKen07]

Do you remember from where you sourced the rings Brooks? Looks like it’s not a standard size found at my typical shops.

[Bcone1381]

Oringsandmore.com. Part 323v. FKM heat resistant black oring size 323. This is fabricated from Viton rubber. Today they are .80 each.

https://www.oringsandmore.com/viton-heat-resistant-o-rings-size-323-price-for-1-pc-1/

[Bissetg]

Well, I joined the list of those that have lost fuel caps in flight today.

I’d filled to the gunnels for our days exploring. After about an hours flight Nev noticed we were streaming fuel from theRH tank. It seems it’s very tricky to get them tight enough to stay put without needing to be prized open with a screwdriver. I’m in the market for different caps.

[Utah-Jay]

schu I look forward to seeing your caps

[Battson]

I think an alternative design would be welcomed by the market schu

While I wouldn't personally be in the market for a new set, I think the demand is definitely there.

[Tim213]

Schu, Based on so many folks losing caps I would be interested in purchasing your caps when they become available.
Tim

[AZBearhawk272]

Schu,

I have caps out there flying. Right now, completing my Bearhawk is my Home priority and I am not going to get distracted at the last 3.258 %
I like several features of your design.
If you care, send me your e-mail and I can answer directly some of your questions and share my discoveries.

Kevin

Bearhawk#272@

Drop the # and add Geemale

[Battson]

Here is a sneak peak of the design. I'm missing the o-ring groove in the render and of course I need to build several that will get thrown away while working through the tolerances. One concern is how consistent are the filler necks? Right now the outside diameter is 1.72 which is .0035 smaller than measured in one bearhawk. I'll probably want to take this to 1.71. Perhaps some of you can tell me the diameter of your necks to see how close they are.

As far as safety, the bottom screws will have notches cut and staked like an andair valve to ensure they don't come loose.

Also missing the notch that will indicate them in the filler neck.

I like the mechanism which you have selected. I have been imagining solutions, your design is similar to what I had in mind. I think it's perhaps the most elegant design achievable without changing the filler neck design. Part of me thinks the best solution may be a different filler neck, but I haven't really thought it through.

If there was some way to ensure a good seal with downward pressure.... Perhaps if the O-ring was at the top up against the rim, in a recess, and then the design allowed the mechanism to close and apply a small downward force on the cap (tapered locking arms perhaps?). Just thinking out loud, you probably don't need extra ideas

[Utah-Jay]

Ok, that video is pretty impressive. Timeframe?

[Utah-Jay]

schu

I am still working on my fuselage, in the covering process, but will look at the fuel ID when I start on the wings, love your design

[Nev]

I should have some dimensions for you later today Schu.

[Mark Dickens]

In measuring one of my tanks, the ID is about 1.725 according to my caliper. The height is hard to determine because of the weld, but if I measure from inside the tank to the top edge, it came out to about 7/8"

[Mark Dickens]

I'm sorry, let me be more specific. When the ID was measured in one direction, it was 1.72", when turned 90 degrees it was 1.73", thus my statement as an average. My digital caliper only shows measurements in 100ths of inches. In terms of the depth of the neck, you want it from inside the tank? I only have one tank at home, so I'll have to measure the other when I get to the airport where the other wing is currently stored

[Mark Dickens]

I just went out and measured the depth and like the others, it came out to 22mm

[Bissetg]

Mine are ID 44mm Depth 22mm

[Nev]

Mine are ID 1.72 inches. Depth 22 mm. Apologies for the mix of metric/imperial.

[Bcone1381]

"Machine it, draft it, build it, brake it. Everytime something new gets built the whole world advances." M. Paytey

Experimental aviation has the element of learning ......

If a cap was inserted into into a tube, then hung it from a chain hoist with a "fish scale" maybe we could measure how much force it takes to remove it, then change things around like O-Rings, lubrication, try various torques on the cap.

So far, my take-a-way is from this thread.....torquing it down with a tool like what was posted by mbaerobat in Post #12 and no lubrication seems prudent to me. Our caps stay in place in a large part due to pressure those o-rings apply to the filler neck. Lubrication can only help them sneak out.

I hope to test mine some day. For now I'll build and keep an eye out for a tube similar to our filler neck.