What do you all think of "Flex Seal"

[Rohan]

If you haven't seen the ads, Flex seal is basically a group of products that claim to provide a flexible, water tight seal, applicable with a spray can, tape, or caulk type gun. https://www.flexsealproducts.com/

I have seen a lot of these commercials, including where this guy makes a functioning boat out of the product, but normally I don't pay that much attention to TV.

There are many other sealants on the market. But the commercial claims it even hardens UNDER WATER, and that got my attention. That is a big deal, and something that I could have really used in the past. (previously, the only product I knew of that would fix a leak underwater was this stuff for swimming pools and it was actually two different types of paste that you had to mix together just prior to applying). So using Flex Tape, for example, you could theoretically patch a small leak on your boat, or use the Flex glue or Flex Shot to repair through hull seals, even if they are underwater.

So I bought some flex glue. At the moment, I don't really have anything critical to use it on so I made a small test, deliberately as difficult as possible. I filled a bucket with cold water. Then put two pieces of very smooth plastic under the water and glued them together. I really didn't think this would work, but I felt a grip on it right away. The product says it takes 24-48 hours to fully cure (underwater might be different, I don't know). But about 12 hours later I checked it, and they were holding together pretty strongly. That's amazing!! I have never seen anything do that before.

On the other hand, not all reviews are positive. The most common complaint on web sites seem to be that the stuff requires a special type of caulk gun and is sometimes too difficult to push out of the tube (apparently it has a shelf life of 24 months and older product apparently is very thick and more difficult to apply than when it is fresh)

Have any of you tried this? What do you all think of its potential?

[tkeithlu]

I have not tried it, but I will note in the general case,

1. There have been a lot of improvements in adhesives in the last ten years or so, and we are benefiting, particularly (to me) in the realm of tapes that will stick where no tape used to.

2. Commercial claims run well beyond reality, and there is mouse milk out there. Remember that bee's wax-like paste that was supposed to seal big gaps in your boat a few years ago? Even West Marine marketed it for awhile.

[CaptTom]

I was talking to someone the other day about this. We've both used Flex products and found that they lose their flexibility and adhesion after some time, maybe one to five years. My experience was one year on gutters, his was 3-5 years sealing around a skylight. Both eventually leaked. Obviously both are exposed to sun, rain, hot and cold. Maybe out of the elements that wouldn't happen.

[Ndavies]

My friend had some damage the other day while we were at sea due to an overtopping wave damaging his da it supports. He tried to seal a small hole with flex seal tape....but found it won’t stick to fiberglass when wet. So much for the ads!

[Minggat]

I bought a roll of the tape. Last week I tried to get some off the roll. Good thing I didn’t NEED it

I gave up. More important things to do. But now I know that I should expect a problem.

[astokel]

I've never seen the tape but I've used the transparent spray and it works well with multiple coats following instructions. The transparent goes on 'almost' invisibly on an older boat. I've only been using it for a year so maybe it will require refreshing.

[JON REISWIG]

I used some of the flex seal glue on a dolly that had broken that I use to haul large sections of wood I split for fire wood I was surprised that it worked well. Problem I ran into was getting the glue out of the tube. I had to use a pliers to force it out and basically ruined one of the tubes but did get enough out to fix the dolly

[Monte Cresto]

I don't know about using it on our boat, however, I've used it to seal a
wood stove leak on our roof about 3 years ago and still doing it's job.
It tends to get much harder with time but still keeps it's adhesive properties.

[bailsout]

I posted a while back that a dock buddy had brushed it on at home below the waterline and now claims that his bottom paint is collecting sea growth, but not the Flex Seal.

[scubadad]

I have used the liquid poured from a gallon can into a roller pan and applied with a regular paint roller. This was to seal the roof of a few metal containers used for storage. The stuff went on without much surface prep and sealed very well, dried overnight so that a couple of coats were possible.
I just bought a gallon of white to be used to paint the inside walls and floor of two lazarets and while a gallon is likely too much, it was as cheap as 2 1/2 quarts ($90 at Lowes). I'm sure it will work well enough to seal out water intrusion.

[Cheechako]

All the particular group of adhesives and glues like Gorilla Glue are aided by water/moisture in curing.
I have yet to find one of these mass marketing miracles that are really much good. But welcome being surprised....

[jmschmidt]

One product which features a large animal in it commercials is junk. The glue, once open, turns hard within a couple of weeks or so and the tape fails as soon as any appreciable amount of water comes in contact with it.

[dlane1181]

We had a flange come partly loose from the intake side of a 30-gallon sump tank. It was too difficult to reach without taking down numerous components that prevented access. I cleaned the area as best I could with rags tied on various extenders, and then liberally applied liquid Flex Seal all around the flange.
It sealed the leak 100% for about a year, and probably would have kept it sealed, but I was torquing on the sump hoses a couple of feet away and it torqued the flange completely off the top of the tank.
There was no way around dismounting everything and doing a proper repair job. But the Flex Seal was a perfect stopgap repair.
We also had a leaky plexiglass hatch cover for a large hatch on the foredeck. Thickly gooped the liquid Flex Seal between the plexiglass and the teak frame for the hatch, and again, it worked great for about a year, which included a transatlantic crossing with plenty of water over the bow. And it came off quite easily when we bought a nice piece of teak timber to reenforce the seam properly and seal with Sikaflex.
So, Flex Seal was 2 for 2 for us. Not an adhesive cure all by any means, but terrific for quickly plugging ~1/4” gaps and seams.

[a64pilot]

Originally Posted by Cheechako

All the particular group of adhesives and glues like Gorilla Glue are aided by water/moisture in curing.
I have yet to find one of these mass marketing miracles that are really much good. But welcome being surprised....

Often it’s just repackaged existing products with a catchy name and heavily marketed at a jacked up price.

[billdre]

So I have one specific use for the Flex Seal spray that has worked well.
At the aft end of my encapsulated keel where it curves into the hull there was a small crack which dripped water after the boat was hauled in the fall. I had it examined and the fiberglass guy says it was an easy fix. He grinds it back to solid underlay and rebuilds the curve. Next fall it's cracked again and dripping until Spring.
This crack doesn't reach the interior of the hull. No leaks inside at all. So I conclude that the issue is the boat gets fixed when it resting on the keel then when they lift it to launch me it opens up again. So the part that attacked me to "Flex Seal" is the flex part. Five years ago I removed all the bottom paint from the area, sanded it and followed the instructions on the can. Several layers over time. Next Spring no leak. It lasted two years then I did it again. Worked again. Next summer it will probably be due.
It's obviously a very specific minor problem. But it keeps the sea water from getting up into the underlying fiberglass or whatever else might be affected. So I like it.