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  #11  
Old 05-28-2020, 02:43 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by Ralph Inkster View Post
Interesting joggle around the edges of those cover plates Dan. Advantages of doing this?
The polysulfide sealant specification includes a basic minimum test elongation of 200%. The standard is as low as 75% when tested in adverse conditions.

Let's use 200%, and assume a no-joggle riveted overlap joint with a 0.001" sealant thickness. Apply a shear load. If the strain displaces the two components by more than 0.002", the sealant line is subject to adhesive or cohesive failure.

Increasing the thickness of the sealant line in the fay surface boosts the capacity for displacement...so just add an outboard joggle.



BTW, warm fuel is one of the adverse conditions. And most readers will be surprised to learn there is no polysulfide standard for resistance to avgas. The test fluid is AMS2629: https://www.sae.org/standards/content/ams2629/

The good news is that most sealant batches test at 300% or more. The joggle is easy insurance.
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Last edited by DanH : 05-28-2020 at 02:48 PM.
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  #12  
Old 05-28-2020, 04:27 PM
Ralph Inkster Ralph Inkster is offline
 
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Hmmm, I should see if I could work a slight joggle into the tank rear baffle panel top & bottom flanges. Those joints need all the help they can get.
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  #13  
Old 05-28-2020, 04:50 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
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Default RV3 hubcaps

Quote:
Originally Posted by DanH View Post
Can't speak for consensus, but the statistics are clear. Paint blisters over tank rivets has nothing to do with MEK application. Nor is it strictly a QB tank problem.

Jim, roughly speaking, when were your QB tanks assembled?

BTW, it is not difficult or risky to install access ports in the rear bulkhead.





I read on here that if you use the RV3 hubcaps as access hole covers, you will get more capacity when it is all said and done. YMMV
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  #14  
Old 05-28-2020, 06:23 PM
JackZ JackZ is offline
 
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I had 1 weeping rivet on my tanks. I purchased the kit with the tanks 1/2 done so I don?t know if it was my rivet or the last owners rivet that leaked. In any case I took a small plastic syringe, cut off the tip about 1/8 inch long and put some new pro seal in it. I cut a 1/4 inch piece of 3/8 fuel line (vinyl). Place the fuel line over the cleaned weeping rivet and place the syringe over that. Squeeze the down on the syringe plunger as hard as you can. The fuel line will bulge out and you can squeeze pro seal in. Carefully wipe clean and do the next one. Simple and no tank removal needed. I was lucky to do mine to an unpainted fuel tank.
No further leaks
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  #15  
Old 05-29-2020, 06:06 AM
FinnFlyer FinnFlyer is offline
 
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Location: Bell, FL
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Default Not leaks

I don't think the paint bubbles over the rivets are leaks as much as some kind of out gassing from the proseal.

My RV-3B quickbuild wings have them too. Using 87 octane gas station gas (up to 10% ethanol).

I forget the survey results -- but how long after tank completion was the airplane painted? Mine at least a year.

Would be interesting to hear from someone who left their plane out in the weather (sun and cold) for years before they painted it.

Or perhaps the proseal never fully cures.

Finn
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  #16  
Old 05-29-2020, 06:34 AM
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caryr caryr is offline
 
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I have had several leaker rivits on my -7 fuel tanks. The ones with just blisters on the top side of the tank, I ignore.

The seepers on the bottom, i have had success drilling out the rivit and putting a sealed 3/16 pulled rivit buttered well with proseal in its place.
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  #17  
Old 05-29-2020, 08:46 AM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by FinnFlyer View Post
I don't think the paint bubbles over the rivets are leaks as much as some kind of out gassing from the proseal.

My RV-3B quickbuild wings have them too. Using 87 octane gas station gas (up to 10% ethanol).

I forget the survey results -- but how long after tank completion was the airplane painted? Mine at least a year.

Would be interesting to hear from someone who left their plane out in the weather (sun and cold) for years before they painted it.

Or perhaps the proseal never fully cures.

Finn
I have had multiple paint bubble over the rivet on both RV and none of them have leaked.
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  #18  
Old 05-29-2020, 12:43 PM
Achelis Achelis is offline
 
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I too have several paint blisters on the upper rivets of my quick build RV-7, and in fact am working on the "fix" now utilizing the vacuum-Locktite method. I placed two layers of blue tape on left and right side of the repair area to create a screed for applying JB Weld Marine epoxy as a filler as added leak protection. I'm now in the process of sanding to level the filler prior to painting.

https://previews.dropbox.com/p/thumb...56&size_mode=2

https://previews.dropbox.com/p/thumb...56&size_mode=2

Last edited by Achelis : 05-29-2020 at 12:46 PM. Reason: Added Second Photo
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  #19  
Old 05-29-2020, 05:43 PM
RV6JOY RV6JOY is offline
 
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Location: Albany, Western Australia
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Hi, leaking fuel tank rivets can be due to not washing the rivets before using them on the tanks. The rivets as supplied are OILY. It appears that in manufacturing the rivets oil is used as a lubricant. This can lead to the rivets leaking fuel.
If you put a couple of hundred in a small class jar and add enough solvent such as acetone then shake it for a while then remove the rivets and compare the solvent with a clean jar of solvent, it will be discoloured by the oil from the rivets.
If you need more convincing, mix some sealant and make a thick layer on a flat surface, poke some cleaned longish rivets into the sealant so the head is still clear of the sealant and do the same with some unwashed rivets. Let the sealant set and try pulling the rivets out of the sealant. You will find the unwashed rivets will pull out easily but the cleaned rivets won?t.
I?d suggest cleaning the rivets at least twice with fresh solvent before use.
I am surprised Van?s have never included this in thereinstructions.
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  #20  
Old 05-29-2020, 06:55 PM
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bruceh bruceh is offline
 
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I concur with the above advice. Clean those rivets thoroughly. I soaked all of my tank rivets in MEK before using them (let them dry obviously before setting). No leaks after 6 years.
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