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Windshield sealant

Flying in the rain the other day, I had water dripping onto my head

Not very good for a classy aircraft

Anyway, there is a 3-4ft long crack in the sealant bead at the top of the windshield, about 0.5mm wide.

I could bodge it and just squeeze some silicone in there but it would be better to dig out the existing one and re-do it.

The TB20 MM mentions PR1829 which is 2-pack so probably good stuff (like the excellent PR1422 fuel tank sealant) but is a right pain because nobody stocks it, it costs about 100 quid, and the Semkit applicator (6oz, 180cc) is another 120 quid.

Also it self evidently isn’t all that great because it cracked very impressively after 12 years, on a hangared aircraft!

Is there another material for light GA windscreen sealing?

One name mentioned is Sikaflex 295UV which is about 25 quid, one can get it from Amazon (etc) and comes in a standard big pack like all the silicones.

Then there are all the el-cheapo silicones which everybody uses for everything, but half of them don’t stick to anything…

The temp range needs to be -40C to +60C, at least, and it needs to really stick otherwise water will come flooding in. It needs to be black or dark grey.

Administrator
Shoreham EGKA, United Kingdom

Sky geek shows a range of sealants, and they tend to have the good stuff Link

Mine is installed like a sailplane: epoxy bonded into the joggled frame, then filled and painted to make the crack invisible. This is attractive and durable but makes a big job when you want to replace a canopy panel as I did a couple of years ago.

Very good UK supplier: http://www.silmid.com/

Norman
United Kingdom

Skygeek have 1489 in stock, but in the USA.

Silmid had no stock when I looked last week. I buy TKS fluid from them (a drum every 10 years )

Also the 1469 needs the expensive applicator, which I won’t ever use again.

Sikaflex 295 has a temp range down to -40C only – marginal.

Can anybody explain how the 2 parts get mixed inside the Semkit tube?

Administrator
Shoreham EGKA, United Kingdom

It is quite easy, first with the rod you push the two components togeter, next a ships-prop like plastic device is used to mix the two components. You have to twist and push / pull it while doing so.

[ dead video link ]

The reason why nobody stocks is the very limited life time (unmixed) combined with being quite expensive. It is often ordered for a specific job.

JP-Avionics
EHMZ

It is common practice to dispense these sorts of compound with a double piston type machine (almost like a double barrelled syringe). On the end of the nozzle is a tube with a spiral inside. This tube with the spiral like a pasta twirl inside is known as a static mixer. We use these when we dispense 2 part potting resins in our production process. It is important to get the right one for the job, as there are lots of different sorts with different twists, diameters, and lengths. One would hope the manufacturer knows what is right, but our experience with our suppliers is not always so positive. Still, it keeps production engineers in a job.

I would try to find a single part sealer.

Darley Moor, Gamston (UK)

Thank you Jesse for that great video. Very interesting!

Neil: Yes – I use a lot of the stuff at work, with epoxies, where the nozzle has the spiral mixer inside. The pistol grip dispenser is standard and cheap

and this is the mixing nozzle (about 50p each – obviously one-use only)

but none of the “adhesive sealants” I found come in that package. Nothing with a decent temperature range. A million different types of epoxies, yes…

Anyway, I bought the Sikaflex 295UV and will try that. Need to wait for good weather for a day, or (virtually impossible right now) find a hangar I can do it in. The present hangar prohibits even approaching the aircraft.

Administrator
Shoreham EGKA, United Kingdom

Headcorn will let you use thier hangars for MX! quite local to you also.

London Area

When mixing those Semkits really take your time to mix the components properly. How do I know… Also the video is not exactly right. You are supposed not to push in the black thing all the way at once but to move the mixer handle and then push it in in parts. This way the compunds is spread across the whole package to begin with.
When mixed take a sample. The very first material will never be mixed properly as it was in the thread of the mixing mechanism. Order the dispensing nozzles separately. For European standards they have non standard threads, so no chance to find a nozzle away from the aviation supply companies.

If they agree to seel sell you stuff and do not think you are too small www.interturbine.com is a source for such products. A while ago they offered my a complete box of 12 Semkits for about what the local shop would charge for one of the same kind!

www.ing-golze.de
EDAZ

Mixing of all semkits are different. Each kit comes with detailed mixing instructions, on how to inject the activator, and how to mix. Both number of rotations and number of strokes up / down are dependend on the kind of sealant in the semkit

JP-Avionics
EHMZ
24 Posts
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