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Left tank- HERE I COME!

I

instructor_bill

Well Known Member
Aside from having put my sender hole in the wrong spot (too close to stiffening depression in the web) I've got a pile o' parts that should be a tank in a few days. Van's says ditch the cork gasket and go bare proseal and it'll be fine.

I know of the fay sealing method, and the use of tape to keep the proseal where I want it. I have a scale for the proseal as well as lots of gloves and throw away clothing. MEK, Acetone, Dawn. Respirator. Rags.

Any last words of encouragement before I dive into the goo?
 
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Pre-cut a bunch of blue shop paper towels into ~ 2" x 2" squares. You can dip those little squares into MEK/thinner and clean a spot up and then throw it away. With full sized towels, you'll create more of a mess trying to fold it to a clean spot. Have fun. It's not that bad. -Jim
 
Git er dun

instructor_bill said:
Aside from having put my sender hole in the wrong spot (too close to stiffening depression in the web) I've got a pile o' parts that should be a tank in a few days. Van's says ditch the cork gasket and go bare proseal and it'll be fine.

I know of the faye sealing method, and the use of tape to keep the proseal where I want it. I have a scale for the proseal as well as lots of gloves and throw away clothing. MEK, Acetone, Dawn. Respirator. Rags.

Any last words of encouragement before I dive into the goo?
Click to expand...

You've made it this far just keep going. Look at how many people stop at the empennage. At one point I bought a -6A that was already started. I got it at the tank stage and built 2 tanks. It's just a different phase of the build. You can do this.
 
I never had a problem with the smell of pro seal. Some people act like it was worse than anything they have ever smelled. Have they ever changed a diaper? Just measure with a scale and use enough to seal well. Make sure you degrease with MEK and you will not have a problem.

DWConner

RV7A
Wiring in the fuse
 
instructor_bill said:
Any last words of encouragement before I dive into the goo?
Click to expand...

How about a few pictures worth a thousand words....from an original Essex Chemical Corp publication, "Polysulfide Sealants For Aerospace", circa 1965. Nothing has changed.



 
Building leak free fuel tanks is easy.....if you pay attention to the details. Like the experience of most builders, chances are the tanks you build will be leak/fume and trouble free. That said, all too many builders continue to run into needless problems. DO NOT thin the proseal and look carefully at the diagrams Dan provided. Keep those illustrations in mind even when some builders may wrongly insist that encapsulating shop heads of the rivets is not all that necessary. I consider their personal experiences to be nothing more than "luck." Take "luck" out of your personal equation and build the fuel tanks to standards that were long ago were established by dedicated professionals. Above all, have fun.
 
Cork Gaskets

I'd ditch the cork gaskets, but use Vyton gaskets. I have a bunch that I'll send you at my cost, along with a disposable punch to make your screw holes. This way if you ever have to get at the fuel senders, it'll be easy.
Drop me a line if interested.
Jack Dekkinga
[email protected]
 
update on the left tank

the stiffeners are all riveted now... it didn't go perfectly, but the're done as are the cap and drain flanges.

my short back rivet set blew up (the roll pin took a hike somewhere in the garage) and I had to set more than half of the rivets with a flush set and bar. Two stiffeners have over driven rivets and enlarged holes with oversized rivets squeezed to fatten them. I was enraged but pulled through.

Later this afternoon I fay sealed all of the interior ribs and clecoed all of the holes. I didn't get the squeezout that I had expected with the ammount of proseal that I put onto the ribs so went back over the web side with another bead to form a complete fillet seal. Doing this I blew up a freezer bag full of proseal and put a bananna slug size pile of sealer on the web of one of the ribs... the humanity!

After cleaning that up and loading a monoject I finished the rest of the fillets on the web side of the flanges. Not a super clean version of fuel tanks like Rick's, but they'll be fine.

I did notice that I didn't encapsulate the rivets on the stiffeners like I had planned before folding the taco-- now I need to use proseal and a stick in a mirror. I can't hardly wait.

I'll set the rib rivets tomorrow or the next day and then later get to encapsulating the whole lot of rivets and then run another fillet on the flange side of the ribs.

The upside... I didn't get proseal in my hair, on my clothes, or all over my tools.

I do have a question though. Should I treat what looks like a pinhole in a fillet as if it were a void that leads to the open air?
 
I guess I should clarify

It's hard to tell what I'm dealing with here. It doesn't photograph well either.

Looking at the fillet, it appears as if there was a tiny bubble that popped, or a tiny little hole in a 1/8 to 3/16 inch fillet. Do I encapsulate this pinhole or is there another completely different method to deal with this issue.
 
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instructor_bill said:
Looking at the fillet, it appears as if there was a tiny bubble that popped, or a tiny little hole in a 1/8 to 3/16 inch fillet. Do I encapsulate this pinhole or is there another completely different method to deal with this issue.
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Encapsulate. Assuming you have a smoothly tooled filet of proper thickness, a dab of sealant over the hole should be fine.

I discussed sealant voids in some detail with our Flamemaster rep some weeks back. If you section a sample of sealant after cure and examine it under magnification, you'll often see closed cell bubbles. They are caused by two substances, air and toluene. The air was whipped into the sealant by the mixing process. The toluene was added by the sealant manufacturer to adjust viscosity. The tiny voids are not a problem as long as they are closed cell (not connected to other bubbles) and not so numerous as to change the physical properties (strength and elongation) of the sealant, ie turn it into something more like sponge rubber.

The trouble with an open void in the surface of a filet is that you don't know if it leads somewhere or how deep it goes. Is it just an open top bubble or is it a tunnel? Best bet is to cap it. The fact that you now have a closed void is no big deal; within reason, closed voids are normal.
 
all ribs riveted, fillet sealed, rivets encapsulated

I went full steam ahead on the tank today.


All but the end ribs are riveted.

All ribs and stiffeners have encapsulated rivet shop heads

All ribs and stiffeners have fillets that would make the Orndorffs smile.


I'm not sure it is the cleanest most finely sealed tank in the world, but there's no way in **** it'll leak (as far as I can tell right now). I'm fairly confident that the extra sealer will provide extra insurance against leaks. I'm willing to sacrifice beautiful slender fillets and no proseal to spare. Put me in the category of: in favor of slightly heavier leak-free tanks. I'll get to the end ribs tomorrow, run the vent line and set up the sending unit. I don't think I'll get to the baffle by tomorrow evening.

Tanks aren't that bad, but I'm glad this one's almost over.
 
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finishing up odds and ends to close the tank

I didn't expect for the last portion of the tank to take as long as it did. I guess I should have expected a bit of extra fiddling to make it come together.

In the last two days I finished the vent line, pickup line, anti-rotation bracket, sender, and float arm all figured out.

A little more proseal to go. I hope to mix enough to do the end rib and all of the fittings/rivets/screws/inspection plate and baffle and get it all done in one swoop. I'll freeze what can't be used right away.

Question of the day: What do I safety wire in place and what would be better to proseal the heck out of to keep from backing out?
 
Tank Stiffeners

Looking at the diagrams it seems that the proseal should start at the vertical portion of the stiffener and extend over the shop head of the rivet and onto the tank skin. Am I looking at this correct?:confused:
 
pilot28906 said:
Looking at the diagrams it seems that the proseal should start at the vertical portion of the stiffener and extend over the shop head of the rivet and onto the tank skin. Am I looking at this correct?:confused:
Click to expand...

Yes, assuming your app falls within the noted dimensions. A mil is 0.001", so 250 mils is 1/4", 60 mils about 1/16".
 
what I've learned on my first tank

buy several 35cc monoject syringes. I mix about 3.5 to 5.5 grams of sealant at a time, load as much as I can, and freeze the syringe I'm not using. If I pull the other from the freezer when I'm prepping it is ready to go (thawed) when I'm ready for the sealant.

Fay seal, cleco, wait 8-12 hours. Any temps over about 65F will tack up the sealant enough to avoid a horrible mess.

Blue tape is valuable but I chose to apply a healthy bead of sealant to all areas that might be prone to leak.

It may be taboo to some, but I chose to smooth the fillet with a gloved finger and some MEK. That way I could see any voids much easier.

I riveted an extra tab to the web of the inner rib that I used to safety wire the vent line. I'd put it between the sending unit plate and the vent line, I however put it on the opposite side and it was a pain to reach and/or see.

Test fit the leading edge mounting bracket after riveting the skin and make adjustments, I didn't and had to clean proseal off of it, make adjustments, and then re-check, clean again, adjust, re-check, clean yet again, adjust, cleco and wait... total pain in the arse and could have been avoided.

In addition to a bead from the rivet holes foreward--the baffle got fay sealed as well. I used blue tape to cover all areas that the baffle would not cover when seated. I feel that the seal should be more than adequate.

I still plan to use the cork gaskets and tite-seal for the sending unit plate as well as the sending unit seal. RESULTS TO COME. I hope for leak free tanks the first time out. I've still got a bit of Proseal to go on the plate and anti rotation bracket before I can put some pressure to it.

Thanks for everybody's input.
 
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LEFT TANK COMPLETE

the final proseal session after installing the baffle is complete. Yesterday I did the tank spacer brackets. I then encapsulated the rivet heads on the baffle and took care of pickup, the anti rotation bracket and vent line. Both are torqued, prosealed, and safety wired.

I really like the tite seal stuff. It's more like really thin clay, but it is a little abrasive when you wipe it up. Not the same demon as proseal and seems to work fine. I think it's quite like rector seal (which is used for household natural gas lines and other plumbing) but not nearly as messy and provides care free cleanup of squeeze-out.

I've got a new tip for you guys that I've not seen anywhere. Plug the vent line with a 1/4 inch flare cap from the hardware store. I know that it's the wrong angle flare but I used a little tite seal on the threads and it seals fine for the pressure test.

Next, flare the end of a short piece of line and attach it to the fuel pickup fitting in the bulkhead. To that, attach the standard aviation issue tank testing balloon. I used the rubber band rib off of an old proseal fouled glove to tighten the balloon to the line and fitting on the fuel pickup.

Install the standard fuel drain.

Using your air compressor and a blow gun, slowly inflate the balloon to your liking through the standard fuel drain.

No need for an extra kit. I'm sure that the $6 van's kit works fine, but I didn't want to wait and I did it for $1.25 (balloon and cap)

Check for leaks with windex. I had small leaks in the threads on the drain valve, put a bit of the mighty tite seal on the threads, ran it back in-- and now I've got a nicely closed system.

It's been several hours and there's no change in the balloon yet. I'll give it at least 24 hours and as long as the temp and baro are the same, we'll see what I've got. Hurry up and wait.

Wish me luck.
 
If you ever plan on using an fuel injection engine, do yourself a favor and install your vapor return fittings before you close the tank. :eek:

It will make hot starting the engine fool proof without a problem of vapor lock. I know ECI engine installation instructions shows it. You can get by without, but then you need to learn the tricks of the trade in starting a fuel vapor locked engine.

Even if you don't use a fuel injection engine, you can still install the fittings and cap them off, just in case you want to upgrade.
 
filling syringes

found this worked well on the right tank


  • Mix proseal well and push it into a pile
  • take a 35cc syringe (or whatever size you use) and remove the plunger
  • put a length of poly tubing on the squirt-end
  • Suck the pile of proseal into the tube (leave some room for the plunger)
  • insert plunger
  • clean off the end of the syringe tube that was in the proseal
  • heat with a hair dryer so the proseal flows well
  • if you load several syringes, you can put the rest into the freezer
  • apply and repeat


Note: if you wait until the proseal has cured, you can use a blow gun and your compressor to shoot the plunger back out, clean the syringe by wiping with a clean dry finger, clean the plunger and put the syringe back into service.
 
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