Author Topic: Cement on Plastic? (Read 3418 times)

Joe Messinger · « **on:** July 07, 2009, 08:30:59 PM »

Anyone know of a cement that will hold on plastic fuel tanks like Sullivan clunk tanks? I have several that have small splits in them that I've tried to repair with 30 min. epoxy, Duco and Sig plastic cement and JB weld. None of those seem to work.

I know, just toss those tanks and get new ones is the easiest but I hate dumping something when there might be a simple way to fix it.

Thanks in advance for any help.

Joe

Bill Heher · « **Reply #1 on:** July 07, 2009, 08:59:32 PM »

You might try melting the cracks closed with a soldering iron- you have nothing to loose.

Wynn Robins · « **Reply #2 on:** July 07, 2009, 09:16:02 PM »

Quote from: Bill Heher on July 07, 2009, 08:59:32 PM

You might try melting the cracks closed with a soldering iron- you have nothing to loose.

this does not work - believe me!!!! I have even tried melting parts of other tanks to use as a weld and this doesn't work either

I have tried all kinds of glue and nothing works.........as far as I know anyway - tanks are cheap enough and not worth the hassle of trying to glue up.

Chris McMillin · « **Reply #3 on:** July 07, 2009, 09:55:30 PM »

I agree with Wynn,
Toss the cracked tank in the trash and get a new one. If you fill the fuse with fuel it will most likely be the end of the model. It's just maintenance and worth the dough and time.
Chris...

Joe Messinger · « **Reply #4 on:** July 08, 2009, 07:49:14 AM »

Well, as I'm sure many of us here did, I grew up with meager resources. I learned early on that if I was lucky enough to have something, and it broke, I had to figure out a way to fix it or do without. Sure, I can afford a new $6.00 tank but I still remember the "fix it or do without days." That's why I thought someone might know of a cement that would work.

Also, most of my planes are profiles so if whatever repair I attempted failed, no real harm would be done.

Joe

Dennis Adamisin · « **Reply #5 on:** July 08, 2009, 08:37:34 AM »

Joe,
I agree with Chris on this however...

Try GOOP - available most hardware or houseware stores. Its kind of like silicone but dries much firmer. Unlike the other glues you mentioned it still remians a bit of flexure.

john e. holliday · « **Reply #6 on:** July 08, 2009, 09:11:35 AM »

I use silicone glue, not the sealer stuff, on even the metal tanks. Remember the surfaces have to be super clean. DOC Holliday

Derek Moran · « **Reply #7 on:** July 08, 2009, 11:22:58 AM »

Forget it, Joe. That tank is made of polyethylene or polypropylene and there are no commonly available adhesives that will bond satisfactorily to it.
Sorry,
Derek

John Cralley · « **Reply #8 on:** July 08, 2009, 12:51:34 PM »

You could always try Duct tape. LOL

Chris McMillin · « **Reply #9 on:** July 08, 2009, 02:43:40 PM »

Quote from: Joe Messinger on July 08, 2009, 07:49:14 AM

Well, as I'm sure many of us here did, I grew up with meager resources. I learned early on that if I was lucky enough to have something, and it broke, I had to figure out a way to fix it or do without. Sure, I can afford a new $6.00 tank but I still remember the "fix it or do without days." That's why I thought someone might know of a cement that would work.

Also, most of my planes are profiles so if whatever repair I attempted failed, no real harm would be done.

Joe

Hi Joe,
I didn't mean to be flippant or offensive, I just mean that for all of the time and effort one can spend trying to fix a bad tank, it's still going to leak and the engine won't run right so the flights flown with the tank leaking air in and fuel out won't be worthwhile. My father, known to be very frugal and worse yet a retired airline Captain (the cheapest) will not repair a plastic tank; But only after years of trying has he come to this conclusion!
Good luck.
Chris...

Frank Sheridan · « **Reply #10 on:** July 08, 2009, 03:07:28 PM »

Someone once suggested using Zap-A-Gap-A-Goo for glueing tanks to the inside of glass fuselages. I've never used it but I think it is similar to GOOP adhesive and sealant which can be found in the RV section of WalMart. Strong odor but sticks to just about everything. I've fixed air mattresses, glued on canopies, and fixed sneakers and a small tear in a convertible top. Wear gloves as it will burn your skin and stay in a ventilated area to protect your eyes and nose from the fumes. Personally I would replace the tank. If you decide to try please let us know the results of your repair. Just for kicks, I think I will go and try to bond two empty milkjugs together and see what happens.

Frank Sheridan · « **Reply #11 on:** July 08, 2009, 04:14:50 PM »

OK, I took two empty milk jugs (2% no less) and wiped off the bottoms with a paper towel and let them air dry for a couple of minutes. I then smeared a bead of GOOP around the perimeter and once across the molded rib of the bottom of one jug. I then pushed the two jug bottoms together and exchanged the glue between the two surfaces. I then pulled them apart and waited about four minutes before driving the two together. Then I set them out on the front porch because the fumes had already propagated throughout the house via the central air system.

Yes, I'm stupid sometimes. When I get home from work tomorrow I will attempt to pull them apart by the handles. I did not rough up either surface nor did I use any slovent for cleaning prior to bonding. I believe that the jugs are made of the same type of polypropylene plastic as the clunk tanks used today. Right now I gotta go open some windows!

Wynn Robins · « **Reply #12 on:** July 08, 2009, 04:36:46 PM »

Quote from: Chris McMillin on July 08, 2009, 02:43:40 PM

Hi Joe,
I didn't mean to be flippant or offensive, I just mean that for all of the time and effort one can spend trying to fix a bad tank, it's still going to leak and the engine won't run right so the flights flown with the tank leaking air in and fuel out won't be worthwhile. My father, known to be very frugal and worse yet a retired airline Captain (the cheapest) will not repair a plastic tank; But only after years of trying has he come to this conclusion!
Good luck.
Chris...

plus the glue will cost more than an new tank anyways.....

billbyles · « **Reply #13 on:** July 08, 2009, 04:38:07 PM »

Quote from: John Cralley on July 08, 2009, 12:51:34 PM

You could always try Duct tape. LOL

Yeah, Red Green of the Red Green show says duct tape will fix anything!

Wynn Robins · « **Reply #14 on:** July 08, 2009, 04:41:18 PM »

Quote from: Frank Sheridan on July 08, 2009, 04:14:50 PM

OK, I took two empty milk jugs (2% no less) and wiped off the bottoms with a paper towel and let them air dry for a couple of minutes. I then smeared a bead of GOOP around the perimeter and once across the molded rib of the bottom of one jug. I then pushed the two jug bottoms together and exchanged the glue between the two surfaces. I then pulled them apart and waited about four minutes before driving the two together. Then I set them out on the front porch because the fumes had already propagated throughout the house via the central air system. Yes, I'm stupid sometimes. When I get home from work tomorrow I will attempt to pull them apart by the handles. I did not rough up either surface nor did I use any slovent for cleaning prior to bonding. I believe that the jugs are made of the same type of polypropylene plastic as the clunk tanks used today. Right now I gotta go open some windows!

different platic and different application - trying to glue a crack is a lot different to gluing two big flat surfaces together.

Joe Messinger · « **Reply #15 on:** July 08, 2009, 05:09:28 PM »

I appreciate everyone's thoughts and comments regarding my cement on plastic tanks question.

Chris, no offense taken. Thanks for responding.

Frank, please let us know how the milk jug experiment turns out.

Actually, my quarry has two points of interest for me. Aside from the Sullivan tanks, I have an old (25 yrs.) Echo string trimmer/brush cutter. The tank on it has a about a 3" crack near the top of the tank. The thing runs great and the tank is the only problem. I've checked several Echo parts resources and most parts for this model (including the fuel tank) are listed as "obsolete." So, I thought that since Sullivan fuel tanks and the one on my Echo are made of similar if not the same material, I could fix them both if I could find the right cement, if that exists.

I,ll try the Goop and see what happens. Thanks to all who have helped. I'll let you know the results so if nothing works for me, Wynn can say "I told ya' so!

Best regards,

Joe

Dennis Adamisin · « **Reply #16 on:** July 08, 2009, 05:22:19 PM »

Joe:
Here's another long shot. Sullivan makes their Flex Tak series that are designed to be very pliable so they fit in odd shape fuselages. However they MIGHT flex enough to come close to fitting in your Echo trimmer???

If so then you have to convert the tank to the gas hardware too - but that ain't too big a deal...

Frank Sheridan · « **Reply #17 on:** July 08, 2009, 05:42:14 PM »

Joe, you didn't say where the cracks were on your tank. If they are in the neck areas, you are probably doomed. Overtightening the stopper is a common malady of these tanks. I had some Byron ducted fan model jets that came with a siamesed tank system consisting of a head pressure tank glued on top of a larger fuel tank with an adhesive that almost looked like hot melt glue, so there IS an adhesive that will stick to polyethylene, but I never trusted it and didn't use them for my planes. I have a sheet of ultra high molecular weight polyethylene that we use at work for making glide surfaces in cabinets, and it has some type of brown liquid primer applied to the back of the sheet so we can adhere it to things. But all this is high dollar stuff, and not really applicable to modeling. This subject reminds me of the comedian Gallagher who used to ask "If nothing sticks to Teflon, how do they stick it to the pots and pans?"

Wynn Robins · « **Reply #18 on:** July 08, 2009, 08:46:27 PM »

why not put a silicon balloon inside the tank - leave the neck out a little bit so the stopper holds it in, and go from there - crack repair from the inside

Larry Renger · « **Reply #19 on:** July 08, 2009, 09:01:36 PM »

Goop is relatively fuel resistant, and sticks to about anything. I use it for my film cannister fuel tanks, and it is good for the better part of a year. You can use it to bond, seal and reinforce fiberglass over cracks in polyethylene. For the neck of a Sullivan tank, you need to use metal wire to compress the crack and Goop to seal it. Or, as mentioned, bite the bullet and buy a new tank and don't over tighten the screws.

Similarly, you can repair the carb housing of a Tee Dee engine that has cracked byusing fine wirie to force the crack closed and a bit of Goop to provide the perfect seal. That one is pretty good forever! Fuel doesn't really get at the Goop, and the wire is not going anywhere!

Richard Antoszewski · « **Reply #20 on:** July 08, 2009, 11:57:32 PM »

The only stuff I found to be strong is 3M Marine adhesive fast cure 5200. It is available at West Marine. I have glued plastic tanks onto aluminum plate mounted on a profile
clown racer and a .46 powered stunt plane. After one year the tank sprung a leak and since I wanted to change the size, I had to cut the tank off of the plate.
The stuff is pricey but it works. I used Goop to seal a fitting on a tank once and it lasted for a short while until the fuel got to it.
Richard

GGeezer · « **Reply #21 on:** July 09, 2009, 06:00:52 PM »

There really is only one good way of repairing blow-molded polyethylene plastic articles and that is by hot gas welding.
The equipment is expensive and you must have an inert gas like nitrogen and the proper filler rod. Even then, it takes experience to do a leak-proof job.
I have had some success in using a high temp. hot glue gun and hot melt sticks. The trick is to use the tip of the gun against the parent material to start melting it and at the same time, flow in the hot melt. This repair only works in low stress areas.
Another technique used in industry to make a non-polar plastic like polyethylene more conducive to having adhesives and paint stick is to flame treat the surface in order to oxidize it. This is how poly bottles are treated before they are silk screened or pad printed in the factory. Even just passing the flame from a lighter over the surface will make things stick better.
But in the end, it is probably cheaper and easier to just replace the part with a new one.

Orv.

Frank Sheridan · « **Reply #22 on:** July 10, 2009, 04:08:59 PM »

I managed to pull the Milk Jug experiment apart, but it took quite a bit of effort. The funny thing was that I was immersed once again in the fumes of the GOOP, so apparently it had not fully cured in 24 hrs. Once an edge broke loose, I was able to peel the joint apart. I would not be afraid to bond a tank to another surface, but tank repairs are not adviseable - as we all seem to agree.