Window Sealant Predicament

[Matt M]

This week I replaced my side windows. I used CS3330-B2 to seal them as recommended. I finished sealing the last window 5 pm Thursday. Its been in a hangar at 65 degree F. This morning the sealant is still purple and wet to touch on three windows. One window is completely dry and a grayish purple as expected. I purchased the sealant from Skygeek (expiration date end of March 2023) and mixed the tubes as specified. Used the ram rod to push the black into the tube as I went down with the mixer. Then mixed it at least 50 times. Will this ever dry? I even rubbed some off and tried using a heat gun, but the sample just got warm. I am fearing the worst of having to pull them out and redoing them. Thoughts?

[Fly Boomer]

2 minutes ago, Matt M said:

This week I replaced my side windows. I used CS3330-B2 to seal them as recommended. I finished sealing the last window 5 pm Thursday. Its been in a hangar at 65 degree F. This morning the sealant is still purple and wet to touch on three windows. One window is completely dry and a grayish purple as expected. I purchased the sealant from Skygeek (expiration date end of March 2023) and mixed the tubes as specified. Used the ram rod to push the black into the tube as I went down with the mixer. Then mixed it at least 50 times. Will this ever dry? I even rubbed some off and tried using a heat gun, but the sample just got warm. I am fearing the worst of having to pull them out and redoing them. Thoughts?

Put some infrared lamps around the windows for a few days.  Regardless of the advertised cure time, it could take several days to set up.  The hand mixing is probably not as good as the machine mixer used by the professionals, so some variation from tube to tube is inevitable.  

[Guest]

Incomplete mixing results in incomplete curing.  You’ll likely be removing the windows and starting over.

[Matt M]

3 minutes ago, M20Doc said:

Incomplete mixing results in incomplete curing.  You’ll likely be removing the windows and starting over.

I think that is what happened or the sealant was bad. I find it hard to believe I mixed 4 tubes wrong, but maybe. The one window came out perfect. That one used its own tube. 

[Jsno]

Polysulfide sealant cures with moisture.  You could try misting some water on it and see if it cures.  I would wait three days to see if it hardens, if not the sealant was a bad batch.  May not have been stored at the proper temperature or may have been frozen to overheated during shipping.  If it hasn't cured in three days you will have to redo.

[A64Pilot]

I used to run into fuel tank sealant that wouldn’t cure in the Army pretty often. I think because we kept it in Conex’s out in the Sun and it got very hot.

My advice buy it in the can as opposed to the self mixing tubes, mix yourself by color, mix a batch the day before and validate it cures, then use that can after it’s been proven.

Mixed sealant can be kept in a freezer for quite awhile and it still be good, so if your going to mix a tube mix it, remove what your going to use that day and immediately put the rest in the freezer, then tomorrow or the next day take it out an hour or so before you need it then use it.

Even unmixed the shelf life of the two components is greatly extended in the fridge, or better the freezer.

You can unscrew the plunger part of the self mixing tubes, push in the valve at the end and get the harder out, then of course just push the product out of the tube if only a small amount is needed so you don’t have to mix a whole tube.

There is a machine that mixes the tubes but it’s hello expensive, I’ve redneck mixed tubes by pushing the harder in, then cutting the mushroom head off and chucking the plunger into a drill then spinning it medium speed while pumping the plunger in and out for a minute or so.

Buying a mechanical gun for the tube is worthwhile, the air powered ones are really great, but expensive.

[MikeOH]

As much as this thread is discouraging me from replacing the side windows myself...if I do so, am I legal without an A&P's supervision?  That is, an owner 'maintenance' item or not?

[hammdo]

Side windows - yes - if you’re the owner. Front windshield - AP has to sign off if you do it…

Maybe try one of those ceramic heaters for curing?

I use one to pre-heat the cabin — might be worth a try…

-Don

 

[Matt M]

3 hours ago, MikeOH said:

As much as this thread is discouraging me from replacing the side windows myself...if I do so, am I legal without an A&P's supervision?  That is, an owner 'maintenance' item or not?

If you do it you need plenty of patience. I researched on here plenty before I started. I have a J which I thought had clips held on with screws. Well surprise to me when I pulled the interior and found out the 4 clips per window are mostly riveted with some screws into the tubular frame. I believe I had to drill out about 40 rivets. All the windows needed trimming except the cabin door window. It all looked perfect yesterday. Then the sealant problem occurred. I ended up pulling the 3 windows today. The sealant was a mess. It was easier cleaning the old 40 year old sealant than the semi wet sealant I put on. MEK is your friend. Remasking the windows, removing them, cleaning up the sealant on the window frames on the airplane, and cleaning the plexiglass set me back 8 hours. Then I need to reinstall them at the end of next week and hope there are no scratches from the remove/replace process.

[Matt M]

4 hours ago, A64Pilot said:

I used to run into fuel tank sealant that wouldn’t cure in the Army pretty often. I think because we kept it in Conex’s out in the Sun and it got very hot.

My advice buy it in the can as opposed to the self mixing tubes, mix yourself by color, mix a batch the day before and validate it cures, then use that can after it’s been proven.

Mixed sealant can be kept in a freezer for quite awhile and it still be good, so if your going to mix a tube mix it, remove what your going to use that day and immediately put the rest in the freezer, then tomorrow or the next day take it out an hour or so before you need it then use it.

Even unmixed the shelf life of the two components is greatly extended in the fridge, or better the freezer.

You can unscrew the plunger part of the self mixing tubes, push in the valve at the end and get the harder out, then of course just push the product out of the tube if only a small amount is needed so you don’t have to mix a whole tube.

There is a machine that mixes the tubes but it’s hello expensive, I’ve redneck mixed tubes by pushing the harder in, then cutting the mushroom head off and chucking the plunger into a drill then spinning it medium speed while pumping the plunger in and out for a minute or so.

Buying a mechanical gun for the tube is worthwhile, the air powered ones are really great, but expensive.

It’s very odd that one tube worked perfectly and the others were crap. They were all mixed the same. I inserted the rod and put about 10% of the hardener in at the top then slowly moved the mixer down a I released the harder. Then I turned the plunger and moved it in and out 50-70 times. I even had someone helping me and they excessively mixed their tubes probably 100 times. I showed my mechanic and he never had any issues with the tubes before. They never used Skygeek though. He is going to get me new ones from Aviall this week. I am convinced that something was wrong with the tubes. 

[A64Pilot]

I hate to say you know what happens, but it sometimes does.

I do think the poster that indicated that they may not have been kept cool in storage could well have been correct. I feel sure heat reduces shelf life.

At the plant, we used to use the tubes, went through hundreds of them a month, never seemed to have an issue, new President came in and knew nothing about airplanes and he switched us to frozen pre-mixed product to save money, it had a short shelf life and we threw away lots of it at great expense, first time I had ever seen it pre-mixed and frozen, that’s what started me freezing it soon after it was mixed if I couldn’t use it all in one day.

[EricJ]

17 hours ago, MikeOH said:

As much as this thread is discouraging me from replacing the side windows myself...if I do so, am I legal without an A&P's supervision?  That is, an owner 'maintenance' item or not?

Yup, specifically listed in FAR 43 Appendix A (c)(13) as Preventive Maintenance:

(13) Replacing side windows where that work does not interfere with the structure or any operating system such as controls, electrical equipment, etc.

As previously noted, this does not include the windscreen.

[0TreeLemur]

I

19 hours ago, MikeOH said:

As much as this thread is discouraging me from replacing the side windows myself...if I do so, am I legal without an A&P's supervision?  That is, an owner 'maintenance' item or not?

Don't be discouraged.   It's not hard to do if you are handy.  When we replaced the side windows in our C in 2019, we used the Flamemaster sealant that comes in paint cans.  Weighed out the parts onto a plastic cutting board using a small digital kitchen scale, and mixed them with a tongue depressor.   We then used the tongue depressor to apply a healthy bead of the sealant to the frame edges, then installed the windows.  Worked great.

[Jsno]

I do stand corrected.  Freezing will actually extend shelf life but heat shortens it.

[Pinecone]

That is pretty much true for most chemicals.  Only thing to watch is that some do not take well to being frozen, so just a fridge for them.

[N201MKTurbo]

When I used to work on defence optics, they would use two part RTV. They would premix it, degas it then freeze it in LN2. it was mixed in dispense syringes. They had a temperature controlled syringe heater they would put them into before use. They would keep it for a year premixed.

[Jsno]

From Flame Master technical bulletin.

 

CURE

The cure period is dependent on the application life, temperature, and relative humidity. Increased temperature and increased relative humidity will speed cure. Reduced temperature and reduced relative humidity will slow cure. Accelerate cureby heating up to 120 deg. F.

STORAGE LIFE

The storage life of CS 3330 CI is nine months when stored at temperatures below 80 deg. F in the original containers. Some change in application life, viscosity and curing rate may occur during this period, however, such changes are slight and in not way effect the end performance of the product.

[Pinecone]

I don't use much polysufide, but I have used a good bit of polyurethane mastics (3M5200).  You can help the curing by misting it with water as mentioned earlier.

[Matt M]

I received new sealant ordered from Boeing. I couldn’t get the cs3330-b2 so had to go with the cs3330-b1/2. Made in Jan 2023, so much fresher than the Skygeek batch.  This worked like a champ. Mixed well and turned the grayish color like it should have. Was tack free after 2 hours. I mixed the same as the previous batch, so that eliminates improper mixing. The previous sealant had to be a bad batch. Something happened to the hardener. Not using the stuff before I wasn’t aware that a purple color is not the proper mixed color. I think I can put in Mooney side windows in my sleep now.