Tank Baffle Rivets

After working on one of my tanks I decided to complete the ailerons and the flaps. Now I've run out of other things to do so I have to go back to the tanks. Fun.

I finished one of my tanks following the procedure that I thought was correct for sealing the rear baffle. I layed down a bead of sealant in the location described in the instructions, below the rivet line. However I now have a small leak along the joint between the baffle and the skin. I may have been a little too neat with the sealant and I'll try adding some more along the outside of that seam to correct the problem. I could also drill out a couple of rivets and put sealant in the hole then re-set them.

As I move on to the second tank I wanted to make sure that I was using the "correct" procedure. I assumed that the seal of the rear baffle was made below the rows of rivets so that those holes did not need sealant applied and the rivets dipped in sealant. Is this correct or should I have been extra safe and used the same riveting process that I used for the ribs and etc? This part isn't very clear in the instructions so I'm just wondering what others have done.

If I remember correctly, all the rivets were supposed to be dipped in pro-seal and set. I know I did that with my tanks.

I understand your confusion as I just finished the first baffle. It isn't clear. In the end, I used the same technique I used everywhere else- fay sealing + the bead + proseal in the dimple and on the tail of the rivet. I haven't pressure tested yet, however.

Referring to the manual....

The only place I see where they tell you to put proseal on the rivets is on the blind rivets that attach the ribs to the baffle. Having said that, I recommend you put proseal on all the rivets. I didn't put proseal on any of my flush rivets and had many leaking rivets. The tanks were a complete nightmare for me. After 2 years of working on them off and and and going through about 11 reseals including cutting holes in the baffles, I now have leak free tanks. My leaks were a-plenty but most were so minor the soapy water test did not reveal them. I finally figured out my own method of checking to find all the leaks. The leading edge is so much more enjoyable to work on

rapid_ascent said:

After working on one of my tanks I decided to complete the ailerons and the flaps. Now I've run out of other things to do so I have to go back to the tanks. Fun.

I finished one of my tanks following the procedure that I thought was correct for sealing the rear baffle. I layed down a bead of sealant in the location described in the instructions, below the rivet line. However I now have a small leak along the joint between the baffle and the skin. I may have been a little too neat with the sealant and I'll try adding some more along the outside of that seam to correct the problem. I could also drill out a couple of rivets and put sealant in the hole then re-set them.

As I move on to the second tank I wanted to make sure that I was using the "correct" procedure. I assumed that the seal of the rear baffle was made below the rows of rivets so that those holes did not need sealant applied and the rivets dipped in sealant. Is this correct or should I have been extra safe and used the same riveting process that I used for the ribs and etc? This part isn't very clear in the instructions so I'm just wondering what others have done.

Click to expand...

Given the leak on my first tank I guess I will go with sealant on each rivet. I might drill out a few around where my leak is and set those after adding some sealant.

I applied sealant in all the skin to baffle rivet holes, AND applied a very narrow thin fillet to the skin to baffle joint (masking the line to make sure it didn't interfere with the wing spar), as well as encapsulating all the shop heads. I had ONE leak through the head of a skin to baffle rivet (no leak at the joint). I repaired the leak by replacing the rivet with the same procedure.

This is not an uncommon problem and that's a typical place for things to leak. The problem isn't the lack of ProSeal on the rivets so much as the ineffective "bead" along the inboard seam that is formed while pushing the baffle down.

I can't state strongly enough how much people should go crazy with ProSeal on that step. Put a ton of it there and let it create a bead the size of Rushmore if you have to. I ended up using two cans of proSeal in building my tank.

Also depending on which corner it's leaking from, you might be able to use the access hole for the fuel sender to reach up in there and put more ProSeal in.

Of the two tanks I have, I have one slightly weeping rivet, but it's not so much because of not having ProSeal on the rivet (which I did by the way, which also caused it to sit slightly proud), it's the poor bead on the rib flange and I could've used more on the flange itself.

ProSeal is cheap. Go crazy with it.

LettersFromFlyoverCountry said:

...
I can't state strongly enough how much people should go crazy with ProSeal on that step. Put a ton of it there and let it create a bead the size of Rushmore if you have to. I ended up using two cans of proSeal in building my tank.

...ProSeal is cheap. Go crazy with it.

Click to expand...

Just not so much that you block the drainage of fuel from bay to bay in the bottom aft corner where the rib meets the baffle:


I think where my problem was, the bead was just a hair too far forward, and the radius of the baffle didn't quite meet the bead in that spot. Were I to ever build tanks again (not out of the question), I would make sure the top of the bead overlaps the bottom of the rivet holes slightly. I went back to tank build photos and found a picture of the bead where I eventually had the leaking rivet. The red circle is the location of the leaking rivet, but I think the bead wasn't contacting the baffle near the next rivet to the right, and the leak migrated to the left until it found an inadequately sealed rivet head:


My first tank didn't leak, and I think I got a bit overconfident (spelled careless) on the second...

Miles,

I think I'm in the opposite situation. My first tank leaked so the second one will have a lot more sealant.

I soaked all my rivets overnight in MEK then dried them. When I had the ribs in for the last fit after I dimpled them I used gorilla tape and laid down the tape on all sides of the rib, about an 1/8 inch from the rib. No we did not measure.Then my wife and I buttered up the ribs with proseal and laid down a thin line over all the rivet holes on the skins. Put the rib in long wise from outside to the tip and being as careful as we could not so slide off the proseal. Once in place we clecoed the rib in place every other hole. The applied proseal to every rivet and used bamboo skews to dab every rivet hole before we put in the wet rivet then set them as we put them in.
After one rib was done we used Popsicle sticks to make a nice seam along the rib.
Then using bamboo skews we dipped then into the proseal and sealed the head side of each rivet
Nice thing about using the bamboo skews is that you and use both ends and throw them away. I actually cut them in half on the bandsaw.
The last item was to remove the gorilla tape. Cleaned up the strings of proseal with MEK and small pieces of cloth.

We used the 2 hour proseal. For those who might not know you have 1/2 hour, one hour and 2 hour proseal. Using the two hour gave us time and we did not rush.
After all the ribs were in place we lightly cleaned up the rivets with MEK.
The next day we cleaned up the rivets and the skin.
Z brackets we also used MEK and soaked the rivet and pop rivets overnight.
Smilin' Jack