My big project this spring will be replacing the Bomar portlights in our '85 E-32. Based on my web surfing, it seems that the aluminum flanges of the portlights should be bedded in either a polysulfide such as 3M 101 or a removable polyurethane such as 3m 4200. Of these two, which is preferred?
Akavishon
Member III
I've just finished rebedding six of my portlights with butyl tape ... much easier to work with than any goop, and so far leak-free:
http://www.rvwholesalers.com/catalog/butyl-putty-tape-13-0880x.html
good luck - Zoran
http://www.rvwholesalers.com/catalog/butyl-putty-tape-13-0880x.html
good luck - Zoran
tenders
Innocent Bystander
Ditto butyl tape. Recommended by "mainesail" who is quite the stickler--he's done a masterful post on this site of butyl tape's benefits complete with photos. My boat partner has been resealing the windows on our 32 over the last few weeks and says it works very well. I bought it from the same place Akavishon did.
Lawrence B. Lee
Member III
Last year we re-bedded a portlight and a fixed window with 3-M 101. That was the easiest part of the job. Getting the fixed window out without bending the exterior frame was tedious. Replacing the rotted teak on the interior was more of a challenge. Staining the new interior teak was a real trial and error adventure. We got it mostly right but the 101 was the easiest.
Lawrence B. Lee
Annabel Lee E 32-200
Savannah, GA
Lawrence B. Lee
Annabel Lee E 32-200
Savannah, GA
stuartm80127
Member II
rebedding portlights
I did 2 things on my E27
1) I filled the gaps between the hull and the liner with West epoxy thickened to peanut butter consistency. First cleaned the areas with acetone then brished in unthickened epoxy.Waited 2 hours then added the thickened epoxy. Cool with strong fan as can get quite warm.
2) Then next day I prepped with Ascetone and lightly sanded area covered by portlight. I then bedded the portlights with 3m-101. If you are in a hurry and don't want to wait a few weeks for a cure then the 3M 4000+UV is also a great choice. Alcohol to clean.
I did 2 things on my E27
1) I filled the gaps between the hull and the liner with West epoxy thickened to peanut butter consistency. First cleaned the areas with acetone then brished in unthickened epoxy.Waited 2 hours then added the thickened epoxy. Cool with strong fan as can get quite warm.
2) Then next day I prepped with Ascetone and lightly sanded area covered by portlight. I then bedded the portlights with 3m-101. If you are in a hurry and don't want to wait a few weeks for a cure then the 3M 4000+UV is also a great choice. Alcohol to clean.
Maine Sail
Member III
Consider the future
Consider the future. Nothing is permanent on a boat so when an item also has a mechanical seal I look for the lowest possible adhesion & longest flexible life. 3M 101 or butyl would be my choices. Polysulfide handles UV better than polyurethane and the jury is still out on polyethers like UV 4000. I have had UV 4000 yellow in one season.
Some like Life Calk which is another polysulfide but I personally have not found it to not hold up quite as well as 3M 101.
3M UV 4000 = 300 PSI per sq inch adhesion (polyether)
3M 4200 = 300 PSI per sq inch adhesion (polyurethane)
3M 101 = 139 PSI per sq inch adhesion (polysulfide)
Butyl Tape = 10-20 PSI per sq inch adhesion (butyl rubber)
Not just sail magazine that recommends those products. I believe they consulted Tony D'Andrea of Select Plastics who owns the worlds largest hatch repair & warranty facility.
Dow 795 is the most widely used product for bedding cast acrylic, what should be used in most marine applications, and polycarbonate/Lexan, what should not be used in most marine applications.
This however is not what should generally be used for sealing aluminum port frames to gelcoat. The 795 or GE SilPruf are used for direct bonding of acrylic or polycarbonate directly to gelcoat or directly to a frame then the frames are sealed with something else.
Some port manufacturers such as Bomon, not to be confused with Bomar, use neoprene foam weather stripping to make the seal. These neoprene gaskets have very little, if any, "bond" or PSI strength yet stay dry for a long time. New Found Metals recommends butyl too..
This is not to say you can't use a silicone for a frame to hull bond but future repairs will become very difficult due to silicone contamination and the next bond may not bond at all..
Consider the future. Nothing is permanent on a boat so when an item also has a mechanical seal I look for the lowest possible adhesion & longest flexible life. 3M 101 or butyl would be my choices. Polysulfide handles UV better than polyurethane and the jury is still out on polyethers like UV 4000. I have had UV 4000 yellow in one season.
Some like Life Calk which is another polysulfide but I personally have not found it to not hold up quite as well as 3M 101.
3M UV 4000 = 300 PSI per sq inch adhesion (polyether)
3M 4200 = 300 PSI per sq inch adhesion (polyurethane)
3M 101 = 139 PSI per sq inch adhesion (polysulfide)
Butyl Tape = 10-20 PSI per sq inch adhesion (butyl rubber)
Not just sail magazine that recommends those products. I believe they consulted Tony D'Andrea of Select Plastics who owns the worlds largest hatch repair & warranty facility.
Dow 795 is the most widely used product for bedding cast acrylic, what should be used in most marine applications, and polycarbonate/Lexan, what should not be used in most marine applications.
This however is not what should generally be used for sealing aluminum port frames to gelcoat. The 795 or GE SilPruf are used for direct bonding of acrylic or polycarbonate directly to gelcoat or directly to a frame then the frames are sealed with something else.
Some port manufacturers such as Bomon, not to be confused with Bomar, use neoprene foam weather stripping to make the seal. These neoprene gaskets have very little, if any, "bond" or PSI strength yet stay dry for a long time. New Found Metals recommends butyl too..
This is not to say you can't use a silicone for a frame to hull bond but future repairs will become very difficult due to silicone contamination and the next bond may not bond at all..
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