Rivets

[sjt]

Can anyone tell me where to get rivets used in the aluminum fuel tank construction?

Bob, book says - use weldable solid and blind rivets.

I can not find a solid aluminum rivet that has the word "weldable". I think the standard AD rivet used on the wing is a 2000 alloy and is not considered weldable.

Also, not finding a blind rivet that is is called "weldable".
Wicks has:
Structural, self-plugging 5056 aluminum rivet with a 7178 aluminum mandrel.
The 5056 domed head is weldable but probably not the mandrel.

I am not sure if it is a better idea to bridge a S.S mandrel or a 7178 mandrel using a TIG.

CHERRY N RIVET IDENTIFICATION CODE:
First letter is rivet material:
A=5052 Aluminum B=5056 Aluminum C=Stainless M=Monel S= Steel U=Copper
Second letter is mandrel material:
A = 7178 Aluminum, S = Steel, C = Stainless
Third letter is head style:
P = Protruding L = Large C = Flush



The rivet I am thinking of using for the trailing edge is Cherry N CCC-42

I can not find a counter sunk aluminum 41 length rivet for the nose skin over the aileron and flap.

The only thing I can find is AD41-H domed rivet or a CHERRY RIVET BSP-41 domed rivet





stan

[sjt]

One other quick question for anyone who has built a fuel tank.
What 2 inch aluminum did you use to make fuel tank inlet?
The tank is 5052.
I do not think I will be able to find a piece of 2 inch 5052.
The best I can probably find is 6061. Is that what everyone does?

stan

[Steve W]

https://www.aircraftspruce.ca/catalog/pnpages/AN470A-4-5.php

1100 soft are weldable as far as I know. Weldable blind rivets, your on your own other than suggesting any soft composition with an aluminum mandrel. Riveted and pro sealed my tanks and knock on wood, no leaks. No distortion either from welding.

[jaredyates]

mswain
Mike Swain used a different style of cap that is flush fitting, and it turned out pretty nice. Let me know if you need any help getting in touch.

[Redneckmech]

One other quick question for anyone who has built a fuel tank.
What 2 inch aluminum did you use to make fuel tank inlet?
The tank is 5052.
I do not think I will be able to find a piece of 2 inch 5052.
The best I can probably find is 6061. Is that what everyone does?

stan

6061 will weld to 5052 nicely. Use a 5356 filler, 4043 will also work and there are claims that it is more crack resistant but I have not had as good of luck with it YMMV. I haven't built a fuel tank for the BH yet but I have repaired a lot of Cessna tanks and have added 6061 bungs to PA12 tanks with good results.

[mswain]

mswain
Mike Swain used a different style of cap that is flush fitting, and it turned out pretty nice. Let me know if you need any help getting in touch.

yes, machined some rings to mount flush caps to my tanks. It’s been awhile, but I think it was 6061 round stock. It welded
to the 5052 just fine.

[sjt]

Thanks for reminding me of SOLID ALUM RIVETS AN470A-4-3 as opposed to AN470AD. I actually have some that I had hidden away to prevent their use in for anything structural.

The A rivet is 1100 alloy - it is weldable.

I guess I will get the blind rivet from Aircraft Spruce CHERRY Q ALUM RIVET AAPQ-42

First letter is rivet material: A=5052 Aluminum B=5056 Aluminum C=Stainless M=Monel S= Steel
Second letter is mandrel material: A = 7178 Aluminum, S = Steel, C = Stainless
Third letter is head style: P = Protruding L = Large C = Flush
Fourth letter is type of rivet: Q = Cherry Q Rivet, structural, self-pluggingFor example,--8 is 8/16ths or 1/2" grip length

The 7178 mandrel is not listed as a tig weldable alloy. My only other choice would have been a steel mandrel.

[Redneckmech]

I would be concerned about welding over the 7178 mandrel, it is a high copper content aluminum alloy and will be susceptible to stress corrosion cracking if welded. Even diluted with a 4043/5356 filler there may be enough copper to compromise the weld.. I may just be over-thinking it, but would lean towards using the AN470A rivets.

Once I get to that point, I am planning to see if I can weld the formers internally to the fuel tank without riveting them but that is quite a ways out.

[sjt]

I absolutely will use the AN470a everywhere I can buck. There will be some pull rivets. There is no ideal solution for them. I guess I could use the steel mandrel 5056 rivets. I was not sure about the expansion coefficient of the steel/aluminum. It will either go wrong at the time of welding, or it should be good to go.

stan

[Redneckmech]

I have never tried welding over a pull type rivet either with an aluminum or stainless steel shank so I am not sure what the result will be in either case, any of my thoughts on it are pure conjecture. One of my old supervisors is a aeronautic welding engineer, I may reach out to him when he is back from vacation and get his thoughts on the topic since it is far outside my knowledge base.

Edit: The more I think about it, you will be melting such a minuscule amount of the 7178 mandrel when bridging it that it likely would not be enough copper to affect the weld.. I will phone a friend when he is back from vacation and get his thoughts on it, though as usual, I am likely over-thinking the topic..

[stinger]

2016-12-13 Fuel Tanks 003.jpg 2016-12-13 Fuel Tanks 008.jpg these are the fuel tanks i built for my Bearhawk LSA. Yes they are made of 50/52 as the instructions call for. However, I secured the tanks with Pro Seal and fuel tank blind rivets. The bungs I purchased from Aircraft Spruce I also installed them with a sealant and standard aircraft rivets.I had a fuel tank welded once and I could never stop the leaks. My RV8 tanks I also used Pro Seal with standard flush rivets and I never had a leak. These tanks have been working well for almost 4 years with no leaks. Good luck. Stinger

[sjt]

Did you make your filler neck?
stan


Also, the Pro Seal is a good idea. Unfortunately, I am compelled to put my finger in the wall socket to see if I still get a shock. The voltage in the U.S is only 120Vac not the 220Vac in Europe.

[stinger]

my filler necks are inverted RV aircraft fuel necks and caps. i vented thru the wing. I lived in Europe many years . Stinger

[fairchild1934]

I would think trying to Tig over a 7000 alloy rivet stem would be asking for the stem to crack and fall into the tank and then obstruct the fuel line.
and if 1 did it-- there would be several dozen along with it. Also -- the broken stem could cause a fuel to leak out the weld. (Depending on where it broke) I would bet it would 100% that the stems would brake off after welding. You can tig a seam down 7075 and it will crack in two somewhere between 2 min and 20 min after you weld. it seems like that allow is pushed right to the extremes of hardness to get great strength and rigidity. And that comes at the cost of being unweldable.

[sjt]

I guess I can get the 5056 blind rivet that has a steel mandrel. I just need to put a blob over mandrel.

stan

[sjt]

I spoke with Bob. He said I should use the aluminum blind rivets with the aluminum mandrel. He thought it would be a bad idea to use a steel mandrel.

I think I will go with aircraft spruce CHERRY Q ALUM RIVET AAPQ-42

Also -on the subject of rivets for the patrol- He thought it would be find to use a 3 size aluminum domed head rivet on the leading edge nose skin for the flap and aileron. The drawing indicated 1/8 aluminum pop rivet.




Lastly, on an unrelated subject, the patrol uses T14 at station C-P The side drawing is correct indicating T14. The T16 shown on another page is in error.
Drawing 17 correct. Drawing 19 should be T14.


stan

[Frank]

Consider also:
hansonrivet.com
Mark pointed me in that direction for blind rivets for a different part of the project (aileron skins).