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Tip: Proseal ...The fact and the fiction

Rick6a

Well Known Member
Tip: Proseal....The Facts and the Fiction

Working with proseal is no big deal.....really. It continues to rate right up there with canopy cutting as a chore many builders seem to dread with a vague sense of impending doom......shadows of ill-defined personal perception overwhelming the clarity of knowledge and reality. Who starts these wild overblown horror stories? Overrated piffle. The stuff of wasted worry.

For years I worked with proseal, often daily and for weeks at a time. Even after many years of working with a material used in far more applications than just fuel tanks, I still had to attend 3 days of sealer school to satisfy customer requirements for training when I did a stint on the C-17 program. The cockpit and nose section of the giant cargo plane is produced in St. Louis. It is proseal that makes pressurization possible. It made some sense to retrain when assigned to the C-17 program because the enormous size of the pressure vessel demanded proseal be applied precisely and application requirements were somewhat different than the routine techniques we commonly employed on the F/A-18 Hornet. Interestingly, those persons skilled in icing a cake performed better with a filleting spoon than their polysulfide-challenged co-workers when requirements specified spreading proseal evenly over a surface without any interruptions or other defects. In the self-interest of limiting the mess to an absolute minimum and keeping my clothes unstained (rarely successful since I refused to wear an apron), I did manage to absorb a few helpful tricks over the years. Admittedly, most of the time I used a pneumatic Semco to apply the stuff, but the use of a Semco sealant gun does present a logistical nightmare for the average homebuilder because it can accept a dizzying array of accessories including various sized tubes, nozzles, spreaders, extentions and such. Last but not least, the stock of limited shelf life sealer was mixed daily and manually stuffed into appropriately sized tubes by the friendly folk working the neighborhood sealer crib, stamped with an expiration date, then distributed plantwide into dozens of stategically located 40 degree below zero freezers for shop use. That was the way things were done for decades until a new age of economic fashion swept the nation. Not too many years ago, the powers-that-be decided proseal mixing should be subcontracted out to distant strangers, layoff notices soon followed, and the proseal mix is now shipped in from afar and stored in new 80 degree below zero uberfreezers!

Fortunately for the RV builder, the job of sealing a bit easier with the introduction of this handy device, essentially a caulking gun. http://tinyurl.com/28gf9o I recommmend using one, if possible. Such a device sure beats using a common alternative a homebuilder has traditionally been reduced to using...a paper cup and a popsicle stick or tongue depressor. Still, the device is nice but not really an essential tool.

As for proseal itself, if you get the stuff on your clothes...forget it. Nothing out there will remove proseal without also discoloring your shirt or pants. I take that back. Methylene chloride will "sometimes" work (depending upon the fabric) but its dubious use is best served for a much more noble cause...to decaffinate coffee. Otherwise its just too toxic a chemical and not worth the risk to health from needless exposure. Prior to using proseal, rub some barrier cream or lotion into your skin to more easily remove the stuff from your hands after a sealing session. Wear a pair or two of latex gloves anyway. You can peel the first pair off as required.

When I assembled my leak free fuel tanks, I proceeded exactly as I would at work. There is no compelling reason to wallow around in wet sealer needlessly! I would commonly apply the proseal to the mating surfaces of the parts (called fay-sealing), 100% cleco the assembly together, then allow it set up somewhere between tack dry and full cure. That's it. Walk away. Upon returning to work the next day or even better....after the weekend, I would then remove every second or third cleco from the assembly, wet install and shoot the rivet, then repeat the process over and over again until all the rivets were set.

23sbuye.jpg


The above pre-digital pictures make a poor attempt to illustrate the procedure I used on my 6A fuel tanks. First, after roughing the local fay sealing surfaces with maroon scotchbrite and thorough cleaning with MEK, the ribs were fay sealed and secured to the skin by 100% clecoing into place. I insured adequate squeeze-out (smoothed into an uninterrupted fillet seal) existed around the ribs and skin (and previously installed stiffeners) without any voids whatsoever. Session complete. I felt no need to have extra sealer arbitrarily slopped all over the place as a sort of voodoo talisman employed to ward off leak demons. In my mind, excessive and weighty sealer needlessly laying about in perpetuity simply displaced that much more fuel the tanks would otherwise hold. A day or so later, the rivets were wet installed by first removing the clecoes from alternate holes. When all rivets were finally set and while I still had interior access, AND to further insure against leaks, using a Q-tip or a toothpick, I swirled a dollop of sealer around the shop head of each rivet to encapsulate it to its dimple. Next came attaching the rear baffle to the tank skin. As shown, I routinely 100% clecoed and clamped assemblies together. I then allowed the freshly (fay) sealed assembly to set up overnight before moving on to and completing the final riveting. This procedure greatly reduced mess and bother when I worked with wet proseal during this interesting phase of construction. Correctly applied, proseal is truly a tough and awesome material.

The photos below were were added on 01/07/09 to more clearly illustrate the procedures I outlined in the original posting. These are detail photographs of the RV-8 fuel tanks I assembled in January '07 following the exact same procedures. Filled with fuel for some months now and like my -6A flying since '05, no leaks have been detected.

29modva.jpg


2ymvzi1.jpg

As in all aspects of our personal construction experience, we should strive for perfection knowing we will never really achieve it. Prosealing need not be the nightmare scenario some would have you believe. Far from it. There are more pleasant sheet metal tasks to do...sure...but...whoever said building an airplane was not going to be a challenging experience from time to time?

Rick Galati RV-6A "Darla" 124 hours
 
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When you say "wet installed" what do you mean? Did you cover the rivet in proseal before putting it into the hole?
Any problems with fitting the rivets into the hole once the clecoes come out? i.e. proseal in the dimple or in the hole?

Thomas
-8 wings - close to tank time
 
Now you tell me!!

Hey Rick! That information would have been a lot more valuable 6 months ago, but I'll know better for the next plane I build.

The problem I have as a newbie is not knowing what it looks like when it's done, and done well. It's like the Star Trek pilot show, where the aliens with the big heads re-assembled the human woman without knowing what one looked like. She worked OK, but she wasn't pretty.

I used too much Proseal, because I figured it would be better to have a tank that was slightly heavy, than one that was slightly leaky. Next time I'll know.

Thanks for the great tutorial.

Tom Costanza
-7A Fuse
 
For me, personally, I went the Orndorff method. That is "ProSeal is cheap, use a lot of it."

So I did. I run the bead along the ribs (as Van's also recommends, by the way) and I put a dab on each rivet head. If there was any doubt, I covered it in ProSeal.

It's possible, I suppose to have used less....but I kept hearing George's voice : "if you look in there and say to yourself, 'this can't possibly leak, it wont. And if you look in there and say 'I hope that spot doesn't leak, it probably will.'"

My goal at the time was to make sure it didn't leak. And, yeah, I did sacrifice some of the interior beauty of my tanks.

But I agree, the dread over ProSealing is much ado about nothing. I really enjoyed building the tanks.
 
TShort said:
When you say "wet installed" what do you mean? Did you cover the rivet in proseal before putting it into the hole?
Any problems with fitting the rivets into the hole once the clecoes come out? i.e. proseal in the dimple or in the hole?Thomas-8 wings - close to tank time
Tom,

"Wet installing" simply means to dab the countersink (most commonly with a Q-tip) with proseal before inserting the rivet. The idea is to seal the area under the head of the rivet. If any proseal migrates into the hole...all the better. Don't worry in the least about clecos sticking to the holes after the proseal has set up. They will come out just fine and as a bonus, clecos with a bit of sealer stuck to them tend to grip future holes that much better. Of course there are limits....limits you and I will never see. In the production environment, clecos used with proseal daily can over time build up so much sealer on them that they become difficult to work with and the only practical method cleaning them is periodic immersion in industrial sized ultrasound machines. They come out pin clean and none the worse for wear.

Rick
 
Proseal

Kind of makes me wish I didn't have QB wings! :)

Want to write an article like that about fiberglass?
 
I don't know what everybody is complaining about with the Prosealing the tanks! Anyplace two pieces of metal come together on our airplane there is proseal. We did it to help stop corrosion which is a big problem in the Savannah area. I also think we could lose 90% of our rivets and the plane would stay together.
 
Great tips for using Proseal. I used the cover it all with proseal method the first time. This next set of tanks will get your method, seems a lot cleaner. One thing, how set can I let the proseal get and still be able to rivet?
 
Rick6a said:
When I assembled my leak free fuel tanks, I proceeded exactly as I would at work. There is no compelling reason to wallow around in wet sealer needlessly! I would commonly apply the proseal to the mating surfaces of the parts (called fay-sealing), 100% cleco the assembly together, then allow it set up somewhere between tack dry and full cure. That's it. Walk away. Upon returning to work the next day or even better....after the weekend, I would then remove every second or third cleco from the assembly, wet install and shoot the rivets, then repeat the process over and over again until all the rivets were set.

Rick Galati RV-6A "Darla" 124 hours

Rick,

Thanks for debunking the 'proseal nightmare' myth. I have been avoiding sealing my tanks for months, always looking for something else to work on. I had read so much about the trials of wallowing around in wet sealer that I couldn't even bring myself to ask anyone to help me with the project.

After reading your advice last night, I promptly got up from the computer and, following your suggestions, installed two tank ribs. There's not much mess at all when you don't try to rivet them while they are still wet. Today, everything looks great. And, I know that installing the rivets is a one-man job when everythig is dry...I did that on the leading edges.

Now I'm a believer. To seal your tanks, you don't have to make a mess, and you don't have to find a helper willing to make a mess with you.

Thanks again for getting me over the fear!

Dave Cole
RV-7 wings
 
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Rick--

I always appreciate your posts because they seem to have some real world experience behind them. I agree that the proseal process does not need to be as daunting as we sometimes make it out to be. My one concern about your approach has to do with letting the sealant begin the curing process before riveting...

I know, in my case at least, that the clecos would not hold the rib very tightly against the skin, with or without proseal. As I riveted my ribs in wet, I was amazed at how much proseal squeezed out in the process (and I think I spread my proseal on the rib flanges very minimally!). If I had not riveted wet, all that proseal would still be between the rib and the skin. Thus, using your approach, as the proseal set, it would be creating a permanent and unecessarily large gap (in relative terms) between the skin and rib such that, when the rivet is set, the rivet would be be likely to expand between the layers rather than pull the two layers together. Maybe no leaks, but also not a very strong rivet. Maybe not a big problem in the real world (I really don't know), but it does seem to be one potential drawback to this method.

Again, thanks for your helpful posts in this forum.
 
alpinelakespilot2000 said:
......that the clecos would not hold the rib very tightly against the skin, with or without proseal. As I riveted my ribs in wet, I was amazed at how much proseal squeezed out in the process.....your approach....be creating a permanent and unecessarily large gap (in relative terms) between the skin and rib...... Maybe no leaks, but also not a very strong rivet.......
Hi Steve,

Thank you for your kind words. I never suggest to others what I have not done for myself or have first hand knowledge based upon my experiences on the factory floor. At least two other local RV builders have adapted my technique for building the fuel tanks and have never looked back.

As you observed, by shooting the rivets while the sealer is still wet, much of it is squeezed out from between the parts. In reality, only a thin film remains. All the more reason why a good fillet seal (bead of sealer) around the perimeter of the parts is so vital. That really doesn't give me a warm and fuzzy feeling of leak free security. Alternatively, if you 100% cleco the ribs into place, you will still note much squeeze-out of the wet sealer still occurs.....just not quite as much as when shooting the rivets while the sealer is still very wet. Remember, it can take days or even weeks for proseal to fully cure.

While I suppose the issue can be subject to debate, I do not believe the strength of the rivet shot after the sealer is allowed to tack dry is compromised in any measurable or meaningful way.

Whether one chooses to use this method or not, at the least, I hope I dispelled some of the sheer nonsense that continues to circulate relating to issues concerning proseal.

Best of luck,

Rick Galati RV-6A "Darla"
 
Question....

Rick, informed others,

Do you prefer to buy several of the small tubes of proseal or the large can? It seems that if you plan several "small" sessions you would waste a lot of proseal if you use the tubes.

Also, where have you guys found the best price for proseal?
 
I didn't like the prefilled tubes. There was a lot of waste.
I preferred using syringes I bought from a pet store. Get the large ones for horses and fill it yourself from the quart kit. Change your gloves after loading & you're ready to go.
 
Rick,
Great advice. To bad it's about 5 years to late for me. I used Dan's method of using hypodermic syringes. You can buy them at the drug store. I bummed mine from a dentist friend and a veterinarian friend.
Using the syringe method allows you to "thin" your ProSeal as needed. Use toluene or lacquer thinner to thin ProSeal. Lacquer thinner is about 93% toluene. Toluene is the thinning agent used by the manufacturer.
One good tip not previously mentioned is to use blue "painters" masking tape. Tape off the areas you don't want the ProSeal to get on. I've found that ProSeal is like Napalm and NeverSeize. Trying to remove these 3 substances only makes them spread more! :)
I like to put on 2 or 3 layers of latex gloves. As the outer pair of gloves get soiled, I can simply peel them off. I don't have to stop work to get my hands clean.
I like to use tongue depressors or popsicle sticks for applying the fillets of ProSeal. It is during this phase that the painters tape really helps. I've built 5 fuel tanks so far, with no leaks.
Charlie Kuss
 
I am just about to seal the inspection panel and fit the fuel sender. Any tips on the best use of the pro-seal. Eg.

The cork seal. Proseal both sides, or not at all. Just seal the screws?

The sender has a rubber gasket, do I proeal it or just the screws?

Any advise welcome.

Tim.
 
Tank cover sealing

rtl_flyer said:
I am just about to seal the inspection panel and fit the fuel sender. Any tips on the best use of the pro-seal. Eg.

The cork seal. Proseal both sides, or not at all. Just seal the screws?

The sender has a rubber gasket, do I proeal it or just the screws?

Any advise welcome.

Tim.
I plan to use Titeseal instead of ProSeal, and apply it to both sides of the cork gasket and on the screw threads. Titeseal doesn't 'dry' or 'cure' so any future removals will be far easier than with ProSeal.

I currently have my sender ProSealed to the cover with no rubber gasket (and hope I never have to remove it :). I didn't know about Titeseal at the time. If I ever have to remove it I will re-install it with cork gaskets and Titeseal. Titeseal needs some sort of gasket between metal surfaces so that all the material is not squeezed out. From the comments I've seen, cork seems to work well because it 'absorbes' the Titeseal a bit. Another way is to use an open weave scrim cloth as a 'gasket' with the Titeseal. I haven't seen any reports about using Titeseal with the rubber gasket. You can always try it and let us know how it goes. The good news is that if it doesn't work, it's easy to remove and use a different gasket.
 
I am about half way through with my tanks. I am installing the interior ribs and am down to about 2.5 hours for two ribs. The first two ribs took five hours to get through. It takes about 7-8 oz of sealant (by weight) to do two ribs. That is about two golfball size lumps. I use the vans technique :). I bought a semco gun on ebay, awesome tool. I measure using a scale, mix by hand (Drill) and load the cartridge. I am also using multiple layers of latex gloves. I have burned through about 150 so far. I would rather toss a glove than sit there and try to clean it with solvent. I am using acetone as much as possible as I really hate MEK. Acetone works OK, just not as good as MEK. I have installed 8 of the 14 ribs to date. I am looking forward to getting through this phase.
-Ron

http://www.kitlog.com/users/index.php?user=rlo1&project=99
 
Update on my tanks-

I've finished riveting the right tank interior ribs using the method Rick spoke about earlier in this thread. I did the first rib using the method most people use, and that of the instrucitons given. That proved to be extremely messy, and time consuming (and stressful). The remaining four ribs on the right tank were fay sealed with 100% clecos, and then set aside for 24 hours. The only time I used gloves for this step was to clean the excess sealant with MEK from the skin from sliding the ribs in to place. I had one little dab of sealant on my index finger when finished. Step 1 done.

24 hours later, I wet installed each rivet by removing two clecos then skipping one, then removing two...The rivets set MUCH easier, and with better shop heads. THEN I put on gloves to clean up with MEK. Again, just a little dab of sealant on my index finger from pushing the rivets in to place. Step 2 complete. I will set this tank aside while I repeat steps one and two with the left tank.

Step 3 will be to simply cover the shop heads and fillet seal the ribs. I use the sealant gun and a cartrige, and a popsickle stick, and probably won't put gloves on do this step either, until I need to clean up using MEK.

This is just my experience with this method to date. It's been a much easier experience than I thought it was going to be, and much cleaner.

I also ran this method by all of our A&P's in my shop before I started it, and all of them agreed it to be a totally acceptable method to sealing the tanks.

.02 :D And thanks Rick!

I'll report back when they are completed, hopefully next week sometime.
 
Proseal and auto gas with ethanol

Can someone please confirm or deny that the use of auto gas that may have ethanol or alcohol in it will affect Proseal and cause my QB tanks to leak?

Is this another myth or is it true?
 
I finished my tanks yesterday! I have not leak tested them yet, but I have to say that using the method described in this thread proved to be CLEAN, and EFFICIENT!

6-25-06-011w.jpg


I did not have a pile of rags to dispose of after each session, I did not get sealant all over everything or myself, and clean up was a snap! I did get sealant on my fingers from wet installing rivets, and a dab or two on the table that was easily wiped up, but I can say I prefer this method hands down!
 
Ethanol reply / measuring question.

Regarding ethanol, the proseal is not the issue, the bare aluminum is the concern. My understanding is that aircraft that are running on 100% ethanol alodine the tanks and fuel lines.

What do you guys use to measure small amounts of Proseal? So far I've only been using proseal on my QB for "non fuel system" stuff, so I haven't worried much about getting the ratio exact. My eyeball seemed to work better than my cheap postal scale when it came to mixing small amounts. Any recommendations on scales or measuring devices for mixing small amounts of Proseal?
 
Rick_A said:
What do you guys use to measure small amounts of Proseal? So far I've only been using proseal on my QB for "non fuel system" stuff, so I haven't worried much about getting the ratio exact. My eyeball seemed to work better than my cheap postal scale when it came to mixing small amounts. Any recommendations on scales or measuring devices for mixing small amounts of Proseal?

Digital Kitchen scale is what I used. If you use your wife's, though, definitely put the whole scale in a ziploc bag first and don't clean proseal off the LCD display with MEK! How do I know this??? :eek: Good luck.
 
digital postal scale with tare function

I picked up a digital postal scale at Office Max (or Depot) for 33 bucks a few months ago that works great! They had scales that were 2-3 times as expensive that didn't look like they would do what I wanted. This one (Sunbeam? not handy to check brand) will measure in ounces or grams, and has a tare function so you're only measuring product. I also have a couple corelle plates dedicated to proseal, so chances of slopping proseal on the scale are minimal. The plates are handy for measuring and mixing both, and are easily cleaned up when done.
 
I'm about ready to start sealing up my tanks and am seriously thinking about using this method. It seems really clean and easy compared to Van's instructions and I'm all for that.

I have a couple questions before I dive in, however. When you use the term "fay sealing" what exactly is meant by this? Also, do you apply sealant to both the rib flange and the skin, or just to one surface before squishing 'em together? Finally, how do you remove the sealant that has oozed into the dimple and set up while waiting before riveting?

Thanks again for posting this method to the board!

--Ken
 
Kenneth said:
..........When you use the term "fay sealing" what exactly is meant by this? Also, do you apply sealant to both the rib flange and the skin, or just to one surface before squishing 'em together? Finally, how do you remove the sealant that has oozed into the dimple and set up while waiting before riveting?--Ken
Kenneth,

A faying surface is that surface to which sealer is applied. To answer your second question, you can apply the sealer to the skin or the rib flange or my personal preference....both parts. I do the best I can with the skin surface but I also like to spread the sealer on the rib flange evenly to insure complete coverage. A plastic knife works well. Like spreading butter on toast. After clecoing the rib in place, it is important that the squeezed out sealer be worked smooth into an uninterrupted "fillet" seal completely around the parts. There are special filleting spoons to do this but a popsicle stick will work.

The next day when you remove the clecos, you will have to clean
the countersinks up a bit but that's no big deal....simply wipe off the sealer with a solvent moistened rag or even your fingernail. I've even run a countersink or 100 degree deburring tool over holes in which the sealer has cured to a fairly hard consistency. In any event, it will come off easily. Use whatever works for you. The goal is to clean the countersink sufficiently so the rivet seats in it nice and flat.

"Wet installing" means just that. You put a dab of wet sealer on the
countersink just prior to inserting and shooting the rivet. You want
the bottom of the (manufactured) head of the rivet to be sealed to the skin
to help prevent fuel leaks. When all the rivets are set, you can then
wipe the skin surface down with MEK or similar to clean it.

Also, and this is important.....do not forget to encapsulate the shop head of the rivets to their dimples before you close up the tanks. A toothpick or cotton swab can be used to swirl the proseal around the shop head...just use a system that works best for you. Just make certain the shop head is completely covered with a dab of proseal.
 
Pastry chef prosealer

The only thing I don't like about proseal is that it resembles my work as a pastry chef.
I just finished the third leakfree tank.
I use parchment paper to make a nice little tube,wrap some tape around it and it is ready to go.Cut the tip as much or as little as you want to get a very small amount in the right place.Best of all when your done with it throw it away.
http://img79.imageshack.us/img79/4938/tankseal1ge6.jpg
http://img79.imageshack.us/img79/9384/tankseal2gi1.jpg
 
Rick,

If I see you at the next local chapter meeting, I'd like for you to look at what's going on with my quick built tanks. (I did not build them)

I've been over this with Van's and they say they have not seen it before, but just about every tank rivet is lifting the paint. There are no fuel leaks, but a blister of lifted paing. It would appear to be a gas formed at the rivet head.

Vans says it could the paint prep. But that doesn't make sense because it is happening only with fuel tank rivets, no where else. The final conclusion was it is filiform (sp) corrosion. Bu again, how come only with fuel tank rivets.

I wondered to Vans if the pro seal had been properly mixed and perhaps never cured? They said no way. What do you think?

dd
 
David-aviator said:
..................what's going on with my quick built tanks..............but just about every tank rivet is lifting the paint. There are no fuel leaks, but a blister of lifted paing. It would appear to be a gas formed at the rivet head.............only with fuel tank rivets......What do you think? dd
Dave,

I have no real idea who builds Van's fuel tanks nor what kind of quality control is maintained during the assembly process. For all we know it could have been an unqualified worker filling in for someone who happened to call in sick that day or a new hire cut loose on his or her own to build your fuel tanks after some period of training and their required work processes not carefully inspected along the way....but of course, I'm just speculating. I do think it is unlikely the proseal was mixed incorrectly as a potential factor because even poorly mixed proseal will within limits, eventually set up. The fact that your fuel tanks have for some time continued to hold fuel without leaking would seem to support that. On this point, I tend to agree with Van.

From what you describe, I would be inclined to think it IS gas forming under the rivet heads and if so...."could" that possibily be due to a chemical reaction with the paint or its base preparation? I believe you painted your -7A with a HVLP....is that yellow color you applied an automotive type paint? Still, I'm inclined to think that during the fuel tank assembly process, either the rivets were not "wet installed" properly or the shop heads encapsulated to their respective dimples with sealer or possibly a combination of both omissions. I would think that if the tanks were properly sealed in the first place, it wouldn't matter what kind of paint process you used, but again I'm speculating.

I know you complained about a few instances of blistering in the past but your recent post seems to suggest the problem is growing to now include virtually all the tank rivets.

Sorry, I really cannot suggest anything approaching a "silvet bullet" fix to make the problem disappear. Perhaps if you have not complied with the recent SB yet, this would be a good time to inspect what internal tank area you can by peering through the access cover hole and see if you can determine if a good fillet seal and shop head encapsulation exists on those areas you can see with a flashlight and mirror. At that time you might want to drill out an easily accessed tank rivet and determine once and for all if sealer traces exist under the head of the removed rivet. Lacking traces of that mandatory sealer, I'd have another chat with Van.

I hope to see you at the next chapter meeting but tend to doubt that upon a casual visual inspection I can add anything more than the possibilities I have outlined here. :(
 
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I Love Pro-seal!

Hey all,
I to am a professional tin bender, so here goes;
1. I cut those thick shop paper towels into 2" squares to wipe sealent off the tail of the rivit before I hit it, saves on puppy feet.
2. Mix as follows, weight one cup and one stick-tare. add 25g base and total, add 2.5g to that total (number only) and wipe a little black stuff on the side of the cup until I reach that number. 25g does one rib.
3.Shoot everything wet, partly cured sealant is asking for working rivits in the future.( Chapter 51 ATR:Boing: Dehavaland and my personal experience ect..)Wipe as much sealant off the finnished rib as possible, to recoat after the assembly is complete. That way any rework(swag) has nothing to stick to.
4. barrier cream AFTER everything is clecoed, then I also keep a cup of baby poweder to dip my fingers in. Try it. It helps. Sticky fingers has it's advantages, figure that out!
5. To clean hands,Go-Jo liberally, then put on a pair of laytex gloves, then work gloves. Your hands will sweat the sealant out of you pours and if you used enough baby powder it will just roll right off with a scotch brite pad. It really works, Mother being the necessity for this invention. ( I love mom more tha proseal!)
6. Hold your toung just right and recite the riviters prayer "Though I buck in a mess of proseal, I shall fear no puppy feet, for rhine Is the MASS, POWER, and DURATION Amen."
 
Fuel Tanks

Rick6a,

I am new here but not new to sealing. You bring up several good points. I have a question though. In your pictures in your first post is the sealant shown all that you applied? I have done a lot of fuel tanks and it looks to me that the void area in the front of the ribs where there are cutouts for rib curvature there is not enough sealant to stop a persistant generated leak path. After your hours flying, are you totally leak free? Thanks.
 
RV8SQDN said:
............In your pictures in your first post is the sealant shown all that you applied? I have done a lot of fuel tanks and it looks to me that the void area in the front of the ribs where there are cutouts for rib curvature there is not enough sealant to stop a persistant generated leak path. After your hours flying, are you totally leak free? Thanks.
RV8SQDN,

By viewing those early disposable camera pictures at the start of this thread, I concede it is very difficult to observe that the rib tip cutouts are completely filled in with sealer. You can barely discern a couple of black lines of sealer filling a few of those cutouts in the first picture of the series. See the photo below of a scrapped tank rib for illustration. In addition, because of the poor quality of the photos you cannot see the uninterrupted fillet seal around both the inboard and outboard edges of the tank rib flanges. I am pleased to report that to date, other than one intermittent weeping rivet on the top of the right tank when it is nearly full, the tanks continue to be leak free. BTW, I used medium weight Titeseal to seal the access covers.
img000120dj2.jpg
 
Is it really necessary to completely fill those on the interior ribs? There are no rivets or holes to the exterior in that area. On the end ribs it is a different story...

Thomas
 
Hey Thomas,

If you don't fill them, it will create a path to the row of rivets for that particular rib. They need to be covered to block that path.
 
Rick6a said:
Working with proseal is no big deal.....really. It continues to rate right up there with canopy cutting as a chore many builders seem to dread with a vague sense of impending doom......shadows of ill-defined personal perception overwhelming the clarity of knowledge and reality. Who starts these wild overblown horror stories? Overrated piffle. The stuff of wasted worry.

For years, I worked with proseal daily, often for weeks at a time. Even after many years of working with a material used in far more applications than just fuel tanks, I still had to attend 3 days of sealer school to satisfy customer requirements for training when I did a stint on the C-17 program. The cockpit and nose section of the giant cargo plane is produced in St. Louis. It is proseal that makes pressurization possible. It made some sense to retrain when assigned to the C-17 program because the enormous size of the pressure vessel demanded proseal be applied precisely and application requirements were somewhat different that the routine techniques we commonly employed on the F-18. Interestingly, those persons skilled in icing a cake performed better with a filleting spoon than their polysulfide-challenged co-workers when requirements specified spreading proseal evenly over a surface without any interruptions or other defects. In the self-interest of limiting the mess to an absolute minimum and keeping my clothes unstained (rarely successful since I refused to wear an apron), I did manage to absorb a few helpful tricks over the years. Admittedly, most of the time I used a pneumatic Semco to apply the stuff, but the use of a Semco sealant gun does present a logistical nightmare for the average homebuilder because it can accept a dizzying array of accessories including various sized tubes, nozzles, extentions and such. Last but not least, the stock of limited shelf life sealer was mixed daily and manually stuffed into appropriately sized tubes by the friendly folk working the neighborhood sealer crib, stamped with an expiration date, then distributed plantwide into dozens of stategically located 40 degree below zero freezers for shop use. That was the way things were done for decades until a new age of economic fashion swept the nation. Not too many years ago, the powers-that-be decided proseal mixing should be subcontracted out to distant strangers, layoff notices soon followed, and the proseal mix is now shipped in from afar and stored in new 80 degree below zero uberfreezers!

Fortunately for the RV builder, the job of sealing got much easier with the introduction of this handy device. http://tinyurl.com/egfol I highly recommmend using one. Such a device sure beats using a common alternative a homebuilder has traditionally been reduced to using...a paper cup and a popsicle stick or tongue depressor.

As for proseal itself, if you get the stuff on your clothes...forget it. Nothing out there will remove proseal without also discoloring your shirt or pants. I take that back. Methylene chloride will "sometimes" work (depending upon the fabric) but its dubious use is best served for a much more noble cause...to decaffinate coffee. Otherwise its just too toxic a chemical and not worth the risk to health from needless exposure. Prior to using proseal, rub some barrier cream or lotion into your skin to more easily remove the stuff from your hands after a sealing session. Wear latex gloves anyway.

When I assembled my leak free fuel tanks, I proceeded exactly as I would at work. There is no compelling reason to wallow around in wet sealer needlessly! I would commonly apply the proseal to the mating surfaces of the parts (called fay-sealing), 100% cleco the assembly together, then allow it set up somewhere between tack dry and full cure. That's it. Walk away. Upon returning to work the next day or even better....after the weekend, I would then remove every second or third cleco from the assembly, wet install and shoot the rivets, then repeat the process over and over again until all the rivets were set.
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The above pre-digital pictures make a poor attempt to illustrate the procedure I used on my 6A fuel tanks. First, after roughing the local fay sealing surfaces with maroon scotchbrite and thorough cleaning with MEK, the ribs were fay sealed and secured to the skin by 100% clecoing into place. I insured adequate squeeze-out (smoothed into an uninterrupted fillet seal) existed around the ribs and skin (and previously installed stiffeners) without any voids whatsoever. Session complete. I felt no need to have extra sealer arbitrarily slopped all over the place as a sort of voodoo talisman employed to ward off leak demons. In my mind, excessive and weighty sealer needlessly laying about in perpetuity simply displaced that much more fuel the tanks would otherwise hold. A day or so later, the rivets were wet installed by first removing the clecoes from alternate holes. When all rivets were finally set and while I still had interior access, AND to further insure against leaks, using a Q-tip or a toothpick, I swirled a dollop of sealer around the shop head of each rivet to encapsulate it to its dimple. Next came attaching the rear baffle to the tank skin. As shown, I routinely 100% clecoed and clamped assemblies together. I then allowed the freshly (fay) sealed assembly to set up overnight before moving on to and completing the final riveting. This procedure greatly reduced mess and bother when I worked with wet proseal during this interesting phase of construction. Correctly applied, proseal is truly a tough and awesome material.

As in all aspects of our personal construction experience, we should strive for perfection knowing we will never really achieve it. Prosealing need not be the nightmare scenario some would have you believe. Far from it. There are more pleasant sheet metal tasks to do...sure...but...whoever said building an airplane was not going to be a challenging experience from time to time?

Rick Galati RV-6A "Darla" 124 hours


RicK: You have some of the best and knowlegeable info on this site!!!! I was taught the same way , different production line!!!
 
cjensen said:
Hey Thomas,

If you don't fill them, it will create a path to the row of rivets for that particular rib. They need to be covered to block that path.

I'm not sure I get that. No different than the fillet that is next to the row of rivets along the length of the rib ... the proseal has to "end" somewhere.
Look at the pictures in the wing construction section of the manual from Van's. They don't have proseal in the very nose section of the tank (at least on the internal ribs). I can't see a good reason to seal this area... ?

Thomas
 
TShort said:
I'm not sure I get that. No different than the fillet that is next to the row of rivets along the length of the rib ... the proseal has to "end" somewhere.............Thomas
Thomas,

Perhaps this edited photo will help you visualize why it is important to fill in those
rib tip cutouts with sealer. In this situation, simply fillet sealing the edges of the rib
flanges will not "surround" the rivet locations on the rib tip cutouts, hence the
(potential) pathway if the entire cutout is not plugged with proseal.

img000160125wg4.jpg
 
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I guess I see the potential path...
The way I did mine, I "buttered up" the rib with a good layer of proseal on all surfaces where there is a rivet hole. I then placed the rib carefully into position, and when clecoed / riveted in place the proseal squeezed out and made a nice fillet all the way around the rib and all the rivet holes. I did not put any proseal on the tabs at the very end where there are no rivet holes; the area you marked as "potential path" has plenty of proseal, however.

I'm 1/2 way done with the interior ribs, doing all the shooting and bucking solo, and this is not nearly as bad as I had anticipated.

Thanks for the tips!

Thomas
 
Weeping Rivet

RV-6A,

One rivet weeping. Not bad. Are you planning on a fix for that? And if so, what is your plan? Because I am not sure if I would have one in your place. Getting something under the rivet head is going to be very difficult. And going in through another way is not very appealing either.
 
RV8SQDN said:
RV-6A,

One rivet weeping......Are you planning on a fix for that? And if so, what is your plan?...... Getting something under the rivet head is going to be very difficult.........
There are a few options to try in my particular circumstance without tearing into the tank.
#1. Do not fill the tank above 15-16 gallons. I know this works but the single weeper only yields a very small amount of blue dye over a period of several days. It really is no big deal to wipe the dye away. In practice, I routinely top off the tank anyway.
#2. Apply Loctite Threadlocker Green (901?) to the rivet head which I am told sometimes works due to its superior wicking powers. I may try that sometime, if I ever get the tank really dry.
#3 Apply a vacuum to the tank to "suck" proseal in from the outside. Apparently this has been done successfully many times.
#4. At AirVenture this year, I was amazed to spot an RV-6A with a blind rivet protruding from the exact same hole location as my weeper. What do you suppose the odds of that are? You can bet it was installed to deal with a weeper. This is a very common fix. Still, a protruding rivet just isn't my thing.
Builders sometimes cut access holes into the rear baffle to deal with bad leaks or in the case of older RV's....peeling slosh. I really don't see removing
the tank and going through all that just to address one single rivet.

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A day or so after I wrote those comments, using eyeball effort alone I mixed what I guessed to be an approximate 10-1 by weight dollop of sealer from what is left in a can of oh-so-long expired proseal purchased from Van in 2000. I applied a dab of it over the head of that weeping rivet and worked a popsicle stick back and forth over the area in an effort to shove some of the sealer underneath the less than perfectly seated rivet head. When in my imaginings I was reasonably sure I did as much as possible under the circumstances, I left the sealer glob to cure in place over the rivet and continued to fly the plane several times over the next few days. Later, I cleaned off the excess sealer from around the area and noticed a distinct halo of proseal remains around the perimeter of the noted weeper. The minimalist effort seems to have worked because since that time with the fuel tank constantly filled to the max, no traces of tell-tale dye have yet emerged from under that rivet. I?d rather be lucky than smart. As a back-up plan, I did manage to locate and purchase some very hard to find -1 grip length flush head Cherry rivets (CR9162-4-1) from Bon-Aero. At this point, my gut tells me it will not be necessary to eventually replace that rivet but as in all things, time will ultimately tell.
 
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Rick,
Your method worked brilliantly. Wish I had known this on the 1st tank.
Much easier to deal with ... less mess and increased visual inspection of rivets.
A counter sink bit was all I needed to clean the dimple of sealant after cleco
removal.
One thing I did learn was not to discard the little nubs (from the inside
of the tank, after cleco removal) onto the floor... :eek: Use the garbage can!!
Steve 81604
 
This procedure seems pretty good. The only question I have is if you let the proseal partially dry with the cleco's installed and then when you go to rivet everything together later. Is there any chances for the skins to get a wave in them between the rivet because the dried proseal may prevent the space between rivets from compressing. Do the skin come out smooth down the rivet line on each rib by letting the proseal dry before riveting?

I can see when riveting the rib to the skin with wet proseal, the proseal will squeeze out and make a tight fit between the rib and skin. Is my thinking faulty?
 
OS rivets?

Rick6a said:
....... As a back-up plan, I did manage to locate and purchase some very hard to find -1 grip length flush head Cherry rivets (CR9162-4-1) from Bon-Aero. At this point, my gut tells me it will not be necessary to eventually replace that rivet but as in all things, time will ultimately tell.
Rick,
For this application, wouldn't the oversize CherryMax CR3242 - which are easily available in the -4-1 size - be a better choice?

The existing hole, which I presume is double dimpled, will not have very parallel sides, which is of little effect to a standard driven rivet, but is not the best hole for pulled rivets, which prefer nice straight sides.... :)

It seems to me that drilling the hole out 1/64 and using a OS CherryMax rivet would give a better joint and also probably better sealing... with no effect on the fit into the existing dimple.

...just a question... gil A
 
Naruto said:
......if you let the proseal partially dry...... Do the skin come out smooth down the rivet line on each rib by letting the proseal dry before riveting.....
You are not really allowing the sealer to cure up hard, merely some degree of tack dryness and in my experience, no discernable waviness has ever been encountered.


az_gila said:
....The existing hole, which I presume is double dimpled...
Gil,

IF the hole were double dimpled (which it is not) the CR3242 would be a better choice. In this case however, the hole is of the standard DWG dimension complete with nice straight sides. :)
 
I shared this procedure with a friend of mine who is a A&P and he also sees nothing wrong with this way to seal the tanks, even though they (Duncan) rivet with the proseal wet. One thing he recommended was to spread proseal completely over the shop heads of the ribs flange instead of just wetting the rivet's shop head themselves with a q tip on the inside of the tank. He said a complete layer of proseal will lessen any chances of a individual rivet leaking later.

He was the one who questions the potential waviness between the rivets.
 
Those of you who used the pre-filled tubes method, how many does it take to do everything on both tanks?
 
Surface Prep of the Dimples

Thinking about the weeping rivets...we're told to Scotchbrite the fay surfaces between ribs/stiffeners and skin before sealing, but what about the fay between the rivet and outside skin dimple surface? Seems like the dimpling process is not a good adhesion-promoting prep. Could that be a reason for poor sealing and should we be addressing those?
 
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