Re caulking giot hatches

[admiralslater]

I have a bunch of 2003hatches on our boat .the caulking between the glass and the frame is heavely degraded and needs renewing.there are no leaks but it has to be a matter of time.
I will clean out the old loose caulking and redo
My question is what would be the best caulking to use
David

[mikereed100]

I've done this several times using different methods on my hatches and found the following to be the only way that didn't leak.

1. Remove the lenses and clean out all the caulking that you can mechanically.
2. Clean with a silicone remover. I use McKanica. McKanica - Revolutionary Aerosol Dispensers - Silicone Removers
3. Rebed with Sika 295 uv with 209n primer (don't skip the primer)

I've tried just about everything else but this is the only cocktail that has remained leak-free.

[admiralslater]

Thanks mike that is what I was. Thinking. The only thing is that the lenses seen very secure and do no leak. I was just going to renew what is the gap between lense and frame to protect the actual adhered area

[mikereed100]

Ahhh. If that's the case, you may be better off leaving them alone until they do leak and then re-bed them. I don't know what kind of caulking Giot uses, but, assuming it is silicone, there is nothing you can do short of cleaning and re-bedding will stick.

[George DuBose]

I have started using butyl rubber in various dimensions. I recently installed a large Lewmar hatch on my foredeck using a 1/2" x 1/16" or so grey tape to bed the hatch and it was so easy. No tubes, no guns, so Sikaflex up to the elbows...

I will use butyl rubber tape to rebed all my hatches next month.

I don't know the life expectancy of butyl rubber, but I am sure it would be easy to remove and replace if it ever fails due to age.

[leftbrainstuff]

Originally Posted by George DuBose

I have started using butyl rubber in various dimensions. I recently installed a large Lewmar hatch on my foredeck using a 1/2" x 1/16" or so grey tape to bed the hatch and it was so easy. No tubes, no guns, so Sikaflex up to the elbows...

I will use butyl rubber tape to rebed all my hatches next month.

I don't know the life expectancy of butyl rubber, but I am sure it would be easy to remove and replace if it ever fails due to age.

Butyl rubber will last indefinitely, and stay flexible, within the seal itself. Its one downside is that whatever is exposed will accumulate dirt and grit. This grit may rust or discolor over time. This grit may also harden, crack or shrink sections of the exposed butyl rubber.

Butyl has a long history of good performance in many navies. They tend to paint everything. This seals the exposed butyl and eliminates the grit problem.

In many of the recreational boat applications we dont tend to paint as obsessively as the military. Choosing a good tube based sealant is the next step.

Barium based sealants work well but Barium has some health issues with regular exposure. Probably not an issue for us part timers.

Take notice of the advice for specific applications. Shrinkage is the usual failure mechanism that leads to leaks.

From an engineering perspective the following points are worth remembering.

1) compatibility between old and new sealants, and mating surfaces is not well understood. Therefore cleanliness is paramount. Mechanical and chemical cleaning of the mating surfaces is mandatory. No exceptions.
2) Repairing leaks by adding a bit of goop never works. You must replace the entire seal
3) check flatness of the mating surfaces. Often screw holes will bulge inward which will reduce the effective tension across the joint.
4) flexible seals will usually fail by peeling as long as the mating surface has enough surface area. Think at least 10x the final compressed seal thickness. When breaking an existing seal peal the surfaces apart. It will take a lot of force and time for a good seal to fail.
5) dont final tension on initial fitment. Final tension after the sealant has cured.



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[George DuBose]

In my Navy, if it didn't move, we painted it, if it moved, we saluted it.

[mikereed100]

I use butyl rubber to bed my hatches to the boat, but when I tried to use it to bed the glazing to the frame it failed in short order. Butyl is best used in conjunction with mechanical fastening.

[George DuBose]

Originally Posted by mikereed100

I use butyl rubber to bed my hatches to the boat, but when I tried to use it to bed the glazing to the frame it failed in short order. Butyl is best used in conjunction with mechanical fastening.

Butyl rubber is not an adhesive. That makes it simpler to deal with installing and I suppose, removing.

I had used Sikaflex to bed glass in a frame of one of my ports. The old silicone was easy to remove, but after I rebedded the glass in the frame the glass broke.

One can't imagine the difficulty of removing fresh cured Sikaflex from an aluminum frame.

I am only using butyl rubber in places that I can use mechanical means to periodically tighten the frame or fitting.

[calliopessoul]

I have had great results using Dow 795. It has great sealing qualities on Lexan, Plexiglas and metal. It is hard to find and generally available at professional building supply stores. Also check Dow's internet site for local availability. It was originally designed to seal in glass in high rise buildings. I am told that Giot used Dow 791 (a cheaper version of 795) in their hatches.