Sealant Suggeations?

Hello everyone.

I have a newly leaky step compartment with no signs of outside damage

Normally I beach my plane when it's not in use, but I'm taking it to Oshkosh where it'll be at anchor for a week.

I wanted to do a soap bubble test on the step compartment, followed by applying a vacuum & brushing a sealany onto any leaks.

Can anyone.suggest a good sealant, ideally one I can pick up at the hardware store?

3m 5200, cut with alcohol...

Z-spar Splash Zone, mix and apply, no sucking needed.

My info is years old... new stuff may be out, but Z-Spar is still in use on boats here.

I just used a bunch of 3M 5200 on my boat to seal port holes where the stainless (316) touches the mild steel (A36). Those areas are subjected to corrosion because of dissimilar metals and salt spray. The 3M 5200 has no equal for me. But, it is more expensive than a tube of silicon from Home Depot. Luckily I purchased the 5200 wholesale.

3M 5200 seems to be the best ocean going (sealant and adhesive) application from what I see over the years. If it is exposed to UV Sunlight, painting works well but not really needed (opinion). There are two types 24 hour and 7 day dry formulas. I like the quick dry, it seems not to bubble as much in the tropics. But, I agitate it on the surface very well during application, thinner is always better for preventing shrinkage and bubbles. I might try what AKTANGO mentioned above about thinning for light applications.

With installed floats it's unlikely you'll get your surfaces clean enough for 5200 or a similar product (sika is my fav) to adhere well. If it's a seam leak and you can get it clean and dry, float lacquer penetrates better than anything from the outside. On the scuzzy inside surfaces, epoxy sticks made for boat repairs work pretty well. You'll still need to get the surfaces as clean as possible but dry isn't important. If you've used anti-freeze inside the floats for winter storage, nothing will stick.

I stopped using expoxy as a sealant because sometimes it will crack ( not always). But, I still carry 5 minutes epoxy everywhere. The underwater (plumbers AKA) epoxy has no equal and is consider good for emergencies from what I understand too. Cleaning is paramount! Filiform corrosion is the first sign of bad prep.

Z-spar will stick. Wet, dry, dirty... Clean what you can and stick it.

I used 5200 cut down to be almost runny, then applied to seams and rivits and sucked in with the shop vac. Worked well.

PRC was our sealer of choice, but harder to find. Was made for floats and makes 5200 seem difficult to use.

One note, any of these sealers are terrible to make come apart. It will take heat to separate and give fumes that will kill the dead.

Z-spar will need to be chipped out or just cut the entire patch out... it sticks that well, and can be drilled and tapped.

And just because a compartment leaks does not mean it'll be a problem. I've had floats that had step compartments that required 20-ish pump strokes to de-water after sitting overnight. If I left town for a week they'd leak the same amount. It concerned me at first but once I knew they wouldn't fill up and that the bulkheads were tight between compartments I quit worrying about it. I've had perfectly tight floats, too. I was always afraid to take them anywhere they might get bumped. My loss. Leaky floats let me go where I wanted and if they took a hit, I didn't care.

Also, all leaks are not always below resting level waterline. Make sure the leaks are not from hatches when you are underway with your floatplane. Underway leaks may stop when you moor.

Andy, if you have the floats out of the water, fill that compartment with water and check where it is leaking.

1. ensure the outside of the float is xompletely dry so you know when you see water, it is coming out of a leaky area.
2. check for loose or worn rivet heads
3. check any seam
4. check the keel area...sometimes the bottom skin will split at the bend from the keel-flat to the side-skin area.
5. you may need to drill out rivets, open a seam, reef out old dry sealant (what vintage are your floats?), apply new sealant, and re-rivet

A. use 3M 5200 Marine sealant FAST. It is THE standard. There are similar products.
B. Alcohol inhibits the cure of any polyurethane sealant......it says that right on the tube of 5200. I will sometimes clean with alcohol, but always let it evaporate before applying the sealant. As to AKTango's trick, I will not ever try it. (Sorry George, maybe I should not read the instructions )
C. wear gloves, and change them often as it becomes difficult to work with sticky fingers.
D.clean up excess sealant with Alcohol or Stoddard solvent on a rag. (rags are better than paper towels by far).
E. Clean any scum from the surface you intend to apply sealant to. I use warm soapy water, then sponge and wipe dry.
F. Polyurethane sealants are moisture loving and cure fine in a moist environment.
G. If you find the leak with the float in the water, apply the sealant and then fill the float compartment to the waterline/lake-level to equalize inside and outside pressure to ensure the sealant stays in place during cure.

a. Splash Zone is a wonderful repair/sealant, that is often used as a temporary repair both externally and internally. It can be difficult to remove, sometimes requiring grinding to remove. Any floatplane guy should have it (and also some 5200 FAST)
b. PRC/flamemaster two-part is a pain in the arse. (fiddly mixing ratio's, expensive, product goes out of date, super-stinky. However, it is supersticky!)
c. If you don't know what you are doing with leaky floats, you can learn.

d. as SB said, how many pumps? how many are you willing to live with? Also, is this a hatch-seal issue rather than a leaker?

Good Luck, you drew about the least fun thing to fix on an airplane.

Suggestion ....

After doing the repair, it may also be a very good idea to leave her in the water (after no leaks) and mark the water line at the level you feel comfortable with for general ops. Then at a glance anyone, you or a designated anchor watch, can immediately tell if it filling with water and how much.

I trained my wife to watch the waterline on our moored boats when I am out of town. I also gave her numbers to call of people who live close by, in case.

GCBC trained his wife. wow.
do you still have her?

Dave Calkins said:

GCBC trained his wife. wow.
do you still have her?

Click to expand...

I believe in an old fashion marriage. Wife is trained by husband only!

Although that is different in areas like Malibu!

Dave,

I agree that alcohol will inhibit 5200 from sealing, but when you have little tiny pinhole leaks along seams it is much easier and less invasive to thin out some 5200, paint along the seam or leaky rivit and put a suction on the compartment.

I flew five years on floats fixed that way without another leak.

Granted, if you have gushers, that is not the repair method, but for tiny pinholes...

to find leaks I don't like to fill with water. Quicker to make a blow tube and put in the pump out, spray the outside with soapy water and pressurise the compartment, (just blow into the tube, no need to get mechanical). Look for bubbling.

I seldom disagree with Dave Calkins, but I would NEVER fill a float compartment with water looking for a leak. First, it will take forever to discover the leak, and depending on the temperature, it may be hard to differentiate between condensation and small leaks. Finally, that's a LOT of weight to put in one compartment. JJ Frey once told me to never fill a compartment of a float unless the float is in the water (as in flooding a float to secure in wind).

Take a vacuum cleaner hose and modify the nozzle so it fits in a float pumpout. Put the hose on the discharge end of the vacuum cleaner. Pressurize each float compartment that's suspicious. Now, with the vacuum running, use a spray bottle filled with dilute dish soap to spray the rivet lines and seams, looking for bubbles. Once found, mark them with a sharpie.

If the leaks you found are around rivets, the best sealant is to simply re-buck those rivets that are leaking. Then re-test with soapy water.\

Once you're done with this process, and you're confident that you've located all the leaks you're worried about, turn off the vacuum, switch the hose to the suction side of the vacuum. Now, in seams or other leaky spots (assuming they're not so big they need a patch, of course), attach the vacuum suction hose to the pump out for that compartment, applying a slight vacuum to the compartment. Now, paint a LITTLE bit of PRC (agree with Dave on this--messy and a PITA) or 5200 to the outside, at the place you marked. Let it suck into the leak. Shut off the vacuum. Wait a bit for the stuff to set up. Start the vacuum again, paint a little tiny bit more at the spot. After you've done this with all the leaky spots/seams, leave it overnight, switch the vacuum hose to the pressure side again, and re-test with soapy water. If there are still leaks, consider re-bucking rivets or apply a little more stick-um.

I've sealed several sets of floats this way, and it works great. Do NOT put sealer inside floats. I've seen guys paint this stuff all over the inside of the floats. All that does is makes for a great place for corrosion to grow, and it really doesn't stop leaks all that well anyway.

By introducing the sealant from the outside, and sucking it into the leak, then stopping the suction, you draw the sealant into the leak, where it'll set up and pretty much seal any small leak.

Again, if your leaks are big ones or along seams, it MAY be best to bang those rivets first. That may fix your problem. In one case, I applied soapy water, found a leak along a chine, applied PRC to that seam, drawing it in with the vacuum, THEN bucked the rivets. Tight as could be as long as I had those floats.

Not that big a job, and certainly better than finding your pride and joy resting on the bottom in the AM.

MTV

MTV I agree with you on an important issue you posted...

Boats are chalked from THE OUTSIDE ONLY. Water pressure forces the caulking in! Organic sealants work better on the outside only! Not always but remember differential pressure on the floats below the waterline!

Kerdi fix is the best thing ive seen up to now it will stick on wet aluminium dry fast we do quite a lot of float repair and this stuff is rreeaaly good and expensive but it work , and it can be painted.

I know I am not the only one who has been at Lake Hood for over 20 years fixing floats the way I described.

I've heard of the "...vacuum the sealant into the leaky area..." fix. What guys used at one time was a fuel tank "sloshing sealant" brushed on the outside. This was the "Harry Home Owner" method of fixing a float. There was a time when guys would put 2 part expanding urethane foam in their floats too. Maybe there are professionals doing this, too.

I cannot argue with Aktango and MTV if this works for them.

Dave Calkins said:

I know I am not the only one who has been at Lake Hood for over 20 years fixing floats the way I described.

I've heard of the "...vacuum the sealant into the leaky area..." fix. What guys used at one time was a fuel tank "sloshing sealant" brushed on the outside. This was the "Harry Home Owner" method of fixing a float. There was a time when guys would put 2 part expanding urethane foam in their floats too. Maybe there are professionals doing this, too.

I cannot argue with Aktango and MTV if this works for them.

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Add me to the list on vacuum and seal from outside. I use the stuff from Lake & Air that I think is the same as sloshing compound. I'm in the water floating for 7 months. Floats are 67 years old.

Glenn

I'm in Dave Caulkin's camp on repairs, but I never filled a float compartment and looked for water coming out. I did 3500 hours on floats in about every place in Alaska salt and fresh water most seasons 4,000 landings a season or so. As you can imagine I had a few repair to do in the field and always some water in the floats as they were getting used hard. Like SB said, if it has water in it, its not necessarily broken. If there is a big change in water level get after it. When you have to use a gas engine pump to preflight clearing compartments you definitively have a problem. I am a 3M 5200 fan, never would start up and taxi a floatplane without it. That and some .020, shears, pk screws and an portable drill with bit and screw tip for the screws. Put all of that with the 5200 in an orange waterproof bag for the emergency fix kit. More than once had to put some logs on the beach and power the 185 up out of the water to fix a gusher. A few other times just jumped in the water and got after it. When the gaper showed up, I could patch it in the water with 5200 on the patch, tighten screws and its holds water. Sometimes those emergency repairs were better than the later permanent fix. Amazing stuff. Of course YMMV.

The Aerocet guys are smirking. I just know it.

8GCBC said:

The Aerocet guys are smirking. I just know it.

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Yep, I've fixed those too!

I even have an Aerocet hat

Andy505 said:

I have a newly leaky step compartment with no signs of outside damage

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If you have EDO 2000s there is a good possibility that the leaks are the rivets which hold the hydro booster to the bottom skin. There is a lot of flexibility in this area which causes loosening of the rivets.

Well said.

PK floats with hydroboosters are also suspect in that area. In fact, I have the task of determining a leaky compartment on a set of PK's this weekend. I am worried that this will be the problem........it is a big fix to do it right.

Most leaks I have seen were easy to determine. All that was needed was a flashlight to look inside the float as it was sinking at the dock

The spot that has a stream of water coming in needs attention quickly;-)


The seam at the back of edo steps are another irritating spot. They get worked all the time, and are cantilevered aft. That was the spot that I most used the thinned out 5200 and suction method. To remove that seam was a long process, and the leak was just above annoying... :???:


But seriously, look at where the bottom has been beat/bent/worn and look at rivits around those areas first, it might save you some time.8)

Hello, Dave.

This 1 step compartment required >20 pumps after being docked for a day. This was a calm 24 hrs on the lake, and I'm mystified as to why this problem would appear in just the one step compartment. Normally the plane isn't docked, instead it's removed from the water when not in use, and the floats are pumped dry at the end of the day.

A bad hatch seal is a possibility, but if that's the case: docking it shouldn't make the problem worse. As this problem happened recently, maybe I'm making the wrong association, and I'll start finding lots of water in the float after every flight..

I've owned the plane for 2 years, and the floats have been pretty tight so far. Last summer it was at anchor for a week @ Oshkosh, and I'd check the floats regulary, never with very much water inside. Last winter I vacuumed all of the compartments dry, and spread about 4 gal of plumbers antifreeze across the compartments.

As for your question about how many pumps I can live with: that's an easy one. For the rest of this season: I just don't want my plane to sink! I keep it out of the water when it's at home, but cottage country beckons, and so do some great camping opportunities. Come winter: I can spring for a gear change, and then work on these floats when there isn't 1000# of airplane attached.

Thanks to everyone for the advice so far.

I tried the "vacuum thinned sealant into the leak" trick last night. Acetone was used to thin the 3M 5200 fast sealant. The sealant cured perfectly as if it had not been thinned.

I determined the leaky areas by spraying soapy water on the bottom and vacuuming at the pump out....then opening the hatch and looking for bubbles.

This was a slick fix!

thanks Supercub.org members!

Dave Calkins said:

I tried the "vacuum thinned sealant into the leak" trick last night. Acetone was used to thin the 3M 5200 fast sealant. The sealant cured perfectly as if it had not been thinned.

I determined the leaky areas by spraying soapy water on the bottom and vacuuming at the pump out....then opening the hatch and looking for bubbles.

This was a slick fix!

thanks Supercub.org members!

Click to expand...

Nice. Did you use FAST or regular 3M 5200. (What did you charge $ ? )

Adding a couple tablespoons of glycerin to the spray bottle of soapy water will make the bubble-method work even better, especially if the floats are wet. By pressurizing the float compartment with the shop vac on 'blow', you can look for the leaks from the outside. Might be easier to see the locations of the leaks,,...especially if that compartment doesn't have a hatch.

The sealant I've been using is marked "3-M EC-776-SR Float Seal". I load some into a small syringe, then apply to the seams at the area of the leak with the shop vac on vacuum. It pulls right into the seam. Works OK for leaks in seams, but would obviously have to use something different for repairs to holes and tears in the metal.

Regarding "re-bucking" a loose and leaking rivet? Should a leaking rivet be removed and replaced, rather than trying to squeeze tighter?

Jim W