My '98 H-376 Salon Window has a vertical, through & through, hairline crack. Any suggestions for a repair, so I do not have to replace window?? Possible to seal crack with an epoxy, or other material ?? Many Thanx, MRF
Salon window crack...Repair
- Thread starter John Murphy
- Start date
You MAY be able to repair it with clear Dow Corning 795. But it will look lousy. 795 is silicone and I know the purists around here are starting to groan, "Oh my God, silicone on a boat. NEVER"
Got bad news for the purists but your production boat (Cat, Hunter, Bene, Jenny, etc) has a heavy load of DC795 on its exterior as a sealant / adhesive on the frameless hatchlights and portlights.
You may be able to "V" out a groove over the crack and fill it with 795 but it depends on the shape and location as to what the finished product will look like as well as your skill in applying it.
Send those pictures and we'll be able to help you better. Or, as we say around here : "HELP US TO HELP YOU"
You'd be amazed at how many posters around here can't even bother to go to the length of sending a picture.
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Dow 795 and the standard hardware store and marine store silicons are different critters. If the silicon smells like vinegar, don't use.
Have you considered that "Late Night Special" FlexSeal? I see their commercials on TV during the daytime now, too. Might be a good interim replacement solution until you replace the entire thing.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,792
If this is an acrylic window, there is a solvent for rebonding hairline cracks: https://www.amazon.com/Acrylic-Bond...=acrylic+solvent+cement&qid=1765798953&sr=8-3
This melts the two surfaces and they fuse back together. You use the thin needle to wick the solvent into the crack through capillary action.
Another fast and easy method is to use superglue and let capillary action draw it into the crack. This does not melt the two sides together, but it does bond them.
Apply on both sides of the window. Put tape on either side of the crack as close as you can so that none of the solvent gets outside the crack and cloud the window around it.
Do not grind a groove into the acrylic, as this will greatly weaken the window and act as a stress riser.
Mark
This melts the two surfaces and they fuse back together. You use the thin needle to wick the solvent into the crack through capillary action.
Another fast and easy method is to use superglue and let capillary action draw it into the crack. This does not melt the two sides together, but it does bond them.
Apply on both sides of the window. Put tape on either side of the crack as close as you can so that none of the solvent gets outside the crack and cloud the window around it.
Do not grind a groove into the acrylic, as this will greatly weaken the window and act as a stress riser.
Mark
WOW !! THANX ALL, for the timely and astute replies. My Post was an afterthought the other night of the day whence I discovered the crack. There is a micro-space between sides ( light can be seen through it from the inside ) so I guess the fusion suggestions might not be feasible?? It's freezing here currently, so I'll send pictures once it warms up so I can visit the boat. Essentially, it's a vertical crack the whole height of the pane. It isn't noticeable from outside. I discovered it when I was raising the window blind....saw a sliver of light. Again, Many Thanx. MRF
If it is cold, then the two sides have contracted and pulled apart. When it is warm again, they will expand and go back into contact and you can weld them together then.
Mark
Not sure what your front (if it is front) hatchlight configuration is like but with our boats being one year apart (but different lengths), it "MAY" be one solid piece right across the deck which is a crack, in the centre, waiting to happen :
When one considers the enormous thermal stress involved in the winter (summer gives you compressive forces IIRC the relative thermal coeff. of exp. ) you will see how the window cracks open and why plastic welding and glue are as just as effective as spitting on the crack.
The problem I have is that every winter the glass contracts and opens either the port or starboard edge of the window which causes a small leak. After a few years (cycles) when it gets annoying enough, I seal it up with 795 again.
The support at the centre fothe window has no 795 on it so it's as good a place as any to split vertically at 90° to the stress as it does with the OP. Why my loooooong hatchlight doesn't split is due to the thickness of the sealant around the perimeter but I'm too lazy to get into that explanation right now.
Do to the large stress across the glass ( <--- x --->) you will need a sealant, not an adhesive, which will move with the annual compression and expansion.
Sharp points, like the bottom of a crack are stress raisers because they are extremely sharp at the bottom and have essentially no area, which gives you :
This is a remedial practice with large cast iron objects when a crack is located. The crack is ground out to its the base which removes the sharp stress raiser and prevents further propogation of the crack.
The problem I have is that every winter the glass contracts and opens either the port or starboard edge of the window which causes a small leak. After a few years (cycles) when it gets annoying enough, I seal it up with 795 again.
The support at the centre fothe window has no 795 on it so it's as good a place as any to split vertically at 90° to the stress as it does with the OP. Why my loooooong hatchlight doesn't split is due to the thickness of the sealant around the perimeter but I'm too lazy to get into that explanation right now.
Do to the large stress across the glass ( <--- x --->) you will need a sealant, not an adhesive, which will move with the annual compression and expansion.
Not exactly. If the crack has not yet penetrated the glass, placing a rounded groove of a Dremel going to the bottom of the crack, will reduce the stress, not raise it.
Sharp points, like the bottom of a crack are stress raisers because they are extremely sharp at the bottom and have essentially no area, which gives you :
Stress = Force ÷ Area
The thermal Force divided by an Area of almost zero produces a very high Stress. Rounding out the bottom of the crack with a rounded groove increases that Area and divides the Force by a much larger number thereby reducing the Stress..
This is a remedial practice with large cast iron objects when a crack is located. The crack is ground out to its the base which removes the sharp stress raiser and prevents further propogation of the crack.
Mark & Ralph, Thanx for Y'All's added info. I forgot about the basic physics, coefficient of thermal expansion. Ralph, the CoTP, plus the extreme drop in temp. here recently, probably contributed to the crack. The same window leaks along the stern edge, especially in our hot summers as it faces south and the sealer disintegrates. And, Dave, You are correct that replacement IS the best solution. I looked on HSBO website but did not find Salon Windows. Any other suggestions for a source?? Thanx to Y'All for Your help. MRF
Give them a call.
The OP stated the crack has penetrated through.
I did not understand how large this window was. Neither rewelding nor 795 is going to solve the problem. The OP needs to either do like you said and split the window and use the center frame as a structural edge for both pieces, or replace the window outright.
Your use of 795 to reseal the frame edge of the window is the correct application. Sealing a crack in the window with 795 is not.
Structural silicones like 795 are adhesives when bonded to two surfaces.
Mark
Correct me if I'm wrong but the reason sealants fail is due to lack of elasticity and due to that, the adhesion fails. So in theory, a stronger adhesive might fair better if more elasticity is not an option?
A better way to think of this is not "lack of elasticity" rather insufficient elasticity for the application. Rubber bands break when stretched because they have been stretched too far. Same with elastic caulks, a thin bead of caulk will have a more restricted range of motion than a thick bead of caulk.
The other issue is many sealants lose elasticity with age and that can cause them to fail because they won't stretch as far. Butyl tape does not do this, they remain elastic for decades.
I did not realize that sealants can lose elasticity with age. This explains a lot. I have a friend who's VERY knowledgeable when it comes to boat repair. He's stated that silicone is fine for bedding so long as the fitting doesn't move much. I've always been skeptical of his use of silicone but what you said backs him up.
Thank you for this info. Ok now back to the issue of the cracked window
The problem with most silicones is poor adhesion, this is especially true with marine silicones and hardware store silicones. There is a category of architectural silicones, like Silpruf and Dow 795 which have both good adhesion and elasticity. If the silicone smells like vinegar it won't have good adhesion.
Which is exactly what Hunter did in later models when they split the large forward window into two pieces with a narrow FG separator in between the two windows. Shorter windows = less thermal stress.