loctite & fuel tanks

[joeboisselle]

In another thread about leaking fuel tanks (and a host of others) there's been suggestions about fixing leaks with loctite. Having patched mine up a couple times and the endless debate about pro-seal and ethanol... makes me wonder if you could use one of the many products loctite advertises on thier website... for the whole tank. I'm just not sold on the idea that pro-seal (or flamemaster) should be the only choice we have to seal our tanks. It obviously doesn't work 100% of the time, and it should. Any thoughts?

[Rick6a]

Originally Posted by joeboisselle

............not sold on the idea that pro-seal (or flamemaster) should be the only choice we have to seal our tanks. It obviously doesn't work 100% of the time, and it should. Any thoughts?

Joe,

The thoughts that follow are not meant as a criticism or indictment but merely underscore what this builder's thoughts on the subject are. From the seemingly large number of reports of cracked canopies, you may as well ask why a replacement for Plexiglas is not used. Proseal, properly applied is truly tough stuff and has a long and proven track record in an extremely wide range of military, commercial and general aviation applications. In the production world, workers are given proper training in the correct application techniques and some aircraft programs require workers to be certified to apply proseal. Even then, mistakes can and will be made. That is why inspection departments overseeing such work are an important part of the production environment. The customer requires it. Not so with RV's because WE builders are the customer. You are right to observe that it "obviously doesn't work 100% of the time" and I believe that as far as our RV's are concerned, the problem will always be traced to some degree of builder error. There is just no way to measure quality from one project to the next and consistency across the board is never going to happen. Sometimes, valuable clues as to why some builders are having trouble with leaking tanks can be found in the very questions that are posed. Many people admit to not replacing bad rivets, convinced they will cause more damage trying to replace than just leaving well enough alone. Sorry, but that excuse would never fly in the production world. As far as wet fuel tanks are concerned, material preparation is very important. Have the mating sufaces been truly prepared to accept proseal? Define CLEAN. Some builders never thought to seal under the rivet countersink, others have not adequately filleted the ribs or stiffeners, still others neglected to encapsulate the shop heads and I might add that particular detail has even been overlooked in premade quickbuild tanks. ANY single mistake in the proseal chain can lead to troublesome leaks later. Without a dispassionate inspector looking over the builder's shoulder saying "That work is unacceptable and must be done over." there is no assurance that any given builder's quality control efforts will be little more than a best effort based upon personal opinion and mixed with equal parts good intentions and an attitude of "good enough."

[N395V]

This would do what you want but it ain't cheap and has a limited shelf life.

http://www.aircraftspruce.com/catalo...s/tankseal.php

If you want a Loctite product for small areas try

http://www.aircraftspruce.com/catalog/wppages/hysol.php

[joeboisselle]

Originally Posted by Rick6a

Joe,

The thoughts that follow are not meant as a criticism or indictment but merely underscore what this builder's thoughts on the subject are. From the seemingly large number of reports of cracked canopies, you may as well ask why a replacement for Plexiglas is not used. Proseal, properly applied is truly tough stuff and has a long and proven track record in an extremely wide range of military, commercial and general aviation applications. In the production world, workers are given proper training in the correct application techniques and some aircraft programs require workers to be certified to apply proseal. Even then, mistakes can and will be made. That is why inspection departments overseeing such work are an important part of the production environment. The customer requires it. Not so with RV's because WE builders are the customer. You are right to observe that it "obviously doesn't work 100% of the time" and I believe that as far as our RV's are concerned, the problem will always be traced to some degree of builder error. There is just no way to measure quality from one project to the next and consistency across the board is never going to happen. Sometimes, valuable clues as to why some builders are having trouble with leaking tanks can be found in the very questions that are posed. Many people admit to not replacing bad rivets, convinced they will cause more damage trying to replace than just leaving well enough alone. Sorry, but that excuse would never fly in the production world. As far as wet fuel tanks are concerned, material preparation is very important. Have the mating sufaces been truly prepared to accept proseal? Define CLEAN. Some builders never thought to seal under the rivet countersink, others have not adequately filleted the ribs or stiffeners, still others neglected to encapsulate the shop heads and I might add that particular detail has even been overlooked in premade quickbuild tanks. ANY single mistake in the proseal chain can lead to troublesome leaks later. Without a dispassionate inspector looking over the builder's shoulder saying "That work is unacceptable and must be done over." there is no assurance that any given builder's quality control efforts will be little more than a best effort based upon personal opinion and mixed with equal parts good intentions and an attitude of "good enough."

Rick, no offense taken, I understand what you're saying. But after assembling a set of tanks, you can only hope you had it cleaned enough, hope you mixed the proseal right, and hope it doesn't start leaking after final assembly. You can, however, continue to fly with a cracked piece of Plexiglass... not a fuel tank. "I hope" isn't good enough for me. After a year my right tank developed a 1 gph leak on 100ll. I'm just not convinced that if I build another tank with proseal that I'm not going to do this again. Any sealant that is as tempermental as you describe shouldn't even be used. (certified to apply? That's terrible!) I'm looking for something you can apply and not think twice about.

Originally Posted by N395V

This would do what you want but it ain't cheap and has a limited shelf life.

http://www.aircraftspruce.com/catalo...s/tankseal.php

If you want a Loctite product for small areas try

http://www.aircraftspruce.com/catalog/wppages/hysol.php

3 gallons... geeze! anyone want to share?

[Hawkeye7A]

On my first tank I spread Pro-seal like peanut butter on the flanges of the tank ribs. Very messy! On the second I put some Pro-seal into a Zip-lop sandwich bag, clipped a corner and used the "cake-decorating" method of laying two good beads of Pro-seal along both sides of the rivet holes prior to sliding the rib into the tank assembly and it went much smoother. After riveting the ribs to the skin get real generous with the Pro-seal over the shop heads as well as the flanges (both sides) of all the ribs. The cake decorating method also works well with laying a bead on both upper and lower edges of the tank skin just forward of the baffle rivet holes (lay a thick bead!) before you place the baffle in place. Put a lot on the aft flanges of the ribs too as well as a good gob in the corners. The directions say to scuff the aluminum well with Scotch-brite. I've found that a cheap bead-blasting gun with the pressure turned down ruffins up the surface better and faster than the Scotch-brite pads could dream of doing and then just before the sealer is applied give them a good wipe down with Naptha. I've got no evidence of leaks in either tank. Hope this helps.

[rvbuilder2002]

Originally Posted by Rick6a

Joe,

The thoughts that follow are not meant as a criticism or indictment but merely underscore what this builder's thoughts on the subject are. From the seemingly large number of reports of cracked canopies, you may as well ask why a replacement for Plexiglas is not used. Proseal, properly applied is truly tough stuff and has a long and proven track record in an extremely wide range of military, commercial and general aviation applications. In the production world, workers are given proper training in the correct application techniques and some aircraft programs require workers to be certified to apply proseal. Even then, mistakes can and will be made. That is why inspection departments overseeing such work are an important part of the production environment. The customer requires it. Not so with RV's because WE builders are the customer. You are right to observe that it "obviously doesn't work 100% of the time" and I believe that as far as our RV's are concerned, the problem will always be traced to some degree of builder error. There is just no way to measure quality from one project to the next and consistency across the board is never going to happen. Sometimes, valuable clues as to why some builders are having trouble with leaking tanks can be found in the very questions that are posed. Many people admit to not replacing bad rivets, convinced they will cause more damage trying to replace than just leaving well enough alone. Sorry, but that excuse would never fly in the production world. As far as wet fuel tanks are concerned, material preparation is very important. Have the mating sufaces been truly prepared to accept proseal? Define CLEAN. Some builders never thought to seal under the rivet countersink, others have not adequately filleted the ribs or stiffeners, still others neglected to encapsulate the shop heads and I might add that particular detail has even been overlooked in premade quickbuild tanks. ANY single mistake in the proseal chain can lead to troublesome leaks later. Without a dispassionate inspector looking over the builder's shoulder saying "That work is unacceptable and must be done over." there is no assurance that any given builder's quality control efforts will be little more than a best effort based upon personal opinion and mixed with equal parts good intentions and an attitude of "good enough."

This is also not meant as a bash towards anyone who has had problems with a tank leak (or any other issue) but I totally agree with Rick's post.

There is nothing wrong with looking at alternatives for doing a particular process but many of these processes we use in RV construction, developed as a standard within the aviation industry (not just RV's). Why did they become the standard? Because they work, and have long term reliability. Is it %100 reliability? No. Occasionally there will be a problem. It is often times hard for us as builders to admit it may have been our technique that caused something unpleasant to happen. With us fast approaching 6000 RV's having been flown (with a very, very small percentage of them having had a tank leak) I think we can say that the current method for sealing RV tanks is a good one.
Sometimes instead of looking for a new process (which could induce even more problems if it is not proven), we need to investigate what might have caused the problem and find ways to avoid it. This is difficult since we are not employees on an assembly line. We do not have another set of eyes to supervise our work while we are doing it and because of the way they are constructed, it is difficult for someone else to evaluate our work after the tank has been completed. Because of this, there will be occasions when a builder thought he was doing everything possible to avoid a leak but still gets one (or more). He may have done everything possible, and he may not have. Since most builders haven't actually been through a hands on training class on building aluminum aircraft fuel tanks' it is very possible for someone to believe they are doing everything right but they might not be. Internet forums such as VAF are great resources, but just because someone has read everything ever written about a particular subject doesn't mean they now have all the skills to do it successfully.
Sometimes doing everything right is still not enough. Over the years I have built about a dozen sets of RV tanks. Of those 24 tanks I have had one leak. It was in a common location (bottom outside corner of rear baffle). I already had the experience of constructing about 6 sets of tanks prior to this so it wasn't because I was inexperienced...it just happened. It was fortunately pretty easy to repair and I have been even more careful since that leak and have been fortunate to not have a repeat.

Sorry....didn't mean to get so preachy...bottom line is evaluate teh problem

Is this a chronic problem experienced by lots of builders? If not, then we first need to consider that we may have been at least part of the cause.

[Robert M]

I built two fuel tanls for my RV-9. One passed the leak test and the other did not. The reason the one tank leaked was because I did a poor job of sealing the tank on the 1st go-round. I did a much better job on the 2nd tank. Once that rear baffle has been riveted into place there is no way you will know fur sure if the tank is completely sealed until it is tested. I have no illusions about the work I did lasting for ever - nothing does. Down the road (in the air) I expect I'll have to fix another leak because the turbulance that I subjected the tanks to caused a marginal seal to pop open. I can not put the blame of any leak on the poor quality of the Flamemaster sealant I used, it was all me.

Had I done a perfect job the tank would not have had a leak nor would either tank have a leak in MY future. BUT, I built my tanks in a garage and nothing I do is gonna be perfect unless I get lucky.

[joeboisselle]

Originally Posted by rvbuilder2002

Is this a chronic problem experienced by lots of builders? If not, then we first need to consider that we may have been at least part of the cause.

Seems to me there are several posts every year here on VAF about people experiencing leak problems. I don't doubt that I had something to do with the problem, even though I thought I'd sealed the @#$% out of the thing.

[lightning]

Originally Posted by joeboisselle

Any sealant that is as tempermental as you describe shouldn't even be used. (certified to apply? That's terrible!) I'm looking for something you can apply and not think twice about.

Joebird, i use proseal at work all the time. (Navy Aviation mechanic) anytime i pop open a panel on a compartment that is sealed, or holds pressure, it's gotta be cleaned and re-prosealed.. (external fuselage panels. sealed nosewheel or bombay panels, leading edges, etc..)

same with our fuel tanks..

having said that, i've seen my share of absolute garbage proseal jobs.. and i've done some bad jobs (when i was new )
it's a job that sucks.. nobody really likes to proseal, but when done right, it'll seal up a tank (or a pressure panel) for a good long time!!

[John H]

Hi All,

Having built 10 sets of tanks for various RV's I have learned a few tricks.

First and foremost you have to be very sanitatry about the entire process. That is clean, clean and clean again, don't use lacquer thinner or naptha both will leave a film that proseal doesn't like. The best cleaner is MEK. Second take what ever size rivits that are called out and soak them in MEK, you have to remember that rivits are bathed in lubricants during manufacture. Dont use shop towles at all, use white terry towles that have been washed and omit the fabric softner, this stuff has a lot of oils and other chemicals. If you use air to blow out the tank before proseal be sure you have either a Motorguard or a Whirlwind filter in the line. The last thing you want to do is blow microscopic oil into the metal.

Now here is the important stuff to do. Use only Class A proseal for the interior of the tank, that is all the interior ribs and riviting. Use the class B proseal for the end ribs and the rear baffle. Class B is designed to be applied with a pressure gun or a spatula not a brush. If you working in a hot time of the year you might consider using a A4 and a B4 compound.

Vans does a dis-service to builders in only selling class B sealant. The class A is considered hazardous to ship. You can order from Aviall it is a stocked item.

With care you will not have any leaks, it isn't rocket science just good planning.

Just my input for success,

John H.
N194JH RV-9