Rebedding Deck & Cabin Hardware ?'s

[Joe11688]

You asked: Can Dolfinite be used for plastics such as hatches and port lights? If not, what do you recommend, silicone rubber adhesive caulking, Sikaflex, or Dow Corning 795? I'm told that silicone is bad for FRP. Is this true?

Joe
　
Nathan answered: Dolfinite is ideal for bedding wooden boats such as hulls, keels, etc., but technically yes it can be used on fiberglass, and most metals. However for plastics especially hatches and port lights which can be exposed to the sun, I highly recommend 3M 4000UV "MMM-06580" which is a great overall product, for flexible rub rails as well. If your set on using Sikaflex the "SIK-295UV" is an excellent choice for your application, either will work well. For FRP's (Fiberglass reinforced panels), use our 3M Polyurethane Adhesive Sealant 560 "MMM-41597" instead of silicone, Silicone shouldn't damage it as it's used to caulk all expansion joints around and between FRP panels in many jobs, thank you.

Nathan
JD Store
(401)253-3840 ex130
store@jamestowndistributors.com

3-M 4000UV has always been my favorite sealant! :dance:
Joe

 

[Merlin Clark]

Maybe that was someone elses post asking about Dolfinite.
Wasn't me, I was making a somewhat offhanded joke because Dolfinite was around long before 3M or Boatlife got involved in marine stuff.
I was introduced to this product by an 86 year old sailor that had used it on his 50' wooden schooner that he sailed/moved to Florida on 50 years before I met him and this stuff was used on that boat long before he got his hands on it.
It works like butyl tape (doesn't glue anything together, comes apart when needed and isn't ruined in a very short period after opening like the tube products) but I prefer the tape because it's so easy to work with and there is NO mess.
As for plastics, I guess I'm a weird one but I go with the manufacturers recommendations over people on forums or salesmen. We have a salesman at the local WM that I heard suggesting 5200 for ALL boat work. This guy is a sailor and also dumb as a box of rocks.
If I have a problem with a plastic port for instance and I followed the manf recommendations, no problem - but if I say "no, I ignored you and followed the advice of Mr. Whozits on SBO" I know exactly the response I'll get.
This is just what I do and I have no interest in persuading anyone to do what I do.

 

[Maine Sail]

You asked: Can Dolfinite be used for plastics such as hatches and port lights? If not, what do you recommend, silicone rubber adhesive caulking, Sikaflex, or Dow Corning 795? I'm told that silicone is bad for FRP. Is this true?

Joe
　
Nathan answered: Dolfinite is ideal for bedding wooden boats such as hulls, keels, etc., but technically yes it can be used on fiberglass, and most metals. However for plastics especially hatches and port lights which can be exposed to the sun, I highly recommend 3M 4000UV "MMM-06580" which is a great overall product, for flexible rub rails as well. If your set on using Sikaflex the "SIK-295UV" is an excellent choice for your application, either will work well. For FRP's (Fiberglass reinforced panels), use our 3M Polyurethane Adhesive Sealant 560 "MMM-41597" instead of silicone, Silicone shouldn't damage it as it's used to caulk all expansion joints around and between FRP panels in many jobs, thank you.

Nathan
JD Store
(401)253-3840 ex130
store@jamestowndistributors.com

3-M 4000UV has always been my favorite sealant! :dance:
Joe

Tony D'Andrea of Select Plastic actually knows about this stuff. He worked for Cyro Plastics long before starting his own company.

Here's what someone who knows this stuff and works with it everyday has to say:


Tony D. - Select Plastics:

"I hear the question as to which sealant to use when bonding Acrylic, or Polycarbonate to aluminum, stainless or FRP over and over and over.....
Well here goes...


The only three adhesives I would consider using are Sika Flex 295 UV with the primer, GE SG-4000, and Dow 795. Using the correct adhesive is only 1/2 the battle. Do not apply the sealants below 50 degrees F. The temperature must maintain at least 50F during the entire 21 day cure cycle. Cut this corner and your finished before you start. Preparation of the bond area is also very/ very important. DO NOT TOUCH THE BOND AREA WITH YOUR BARE HANDS! Contamination from the dirt and skin oils will make a solid cure impossible. You may clean the FRP and metal with acetone to prep the area but if you touch the Lexan or Plexi with harsh solvents you will ruin the portlight. A 50/50 mix of isopropal alcohol and distilled water will work well to clean the plastic if needed. Remember that clean enough is not clean enough."




Beyond that;


Darrell at Cyro Plastics, the actual manufacturer of Acrylite GP, the most widely used cast acrylic in the marine market, has stated that no 3M sealants of any type, polyether (UV 4000), polyurethane (4200, 5200), polysulfides (101 - now discontinued) or the 3M silicone (marine silicone) are recommended for use with Acrylite GP cast acrylic.


They tested UV 4000 and all the other 3M products just last year and none got the nod.They all caused accelerated failures of the sheet due to the solvents in them. What you got from JD is poor information at least in regards to acrylic in terms of the UV 4000. Sika 295UV is still good, and that was good info BUT it must be used with the special primer which Nathan left out of the answer.

 

[FastOlson]

Great comments about surface prep and cautions about contamination.

I would like to add a lonely data point about one adhesive/sealant that sometimes is overlooked. "LifeSeal" from the BoatLife brand.
We used LifeSeal black to properly "float" out new Lexan fixed port lenses against the gel coated cabin sides in '95. Still NO leaks, ever. That's about an eigth inch of the sealant under the edge of each port lens. The overlap is about 3/4", and I cleaned both mating surfaces with acetone (frp side) and water (Lexan) and then roughed both mating surfaces with some 80 grit.

As could be predicted, UV exposure has dulled the lens surfaces over the decades, but the seal remains intact.

 

[Joe11688]

Great comments about surface prep and cautions about contamination.

I would like to add a lonely data point about one adhesive/sealant that sometimes is overlooked. "LifeSeal" from the BoatLife brand.
We used LifeSeal black to properly "float" out new Lexan fixed port lenses against the gel coated cabin sides in '95. Still NO leaks, ever. That's about an eigth inch of the sealant under the edge of each port lens. The overlap is about 3/4", and I cleaned both mating surfaces with acetone (frp side) and water (Lexan) and then roughed both mating surfaces with some 80 grit.

As could be predicted, UV exposure has dulled the lens surfaces over the decades, but the seal remains intact.

I've heard some good reports on LifeSeal. I had talked to Rudy Nickerson at his store about dull port lights and he told me that some guys have used an extra fine steel wool and followed it up with a rubbing compound to get it back. I really don't know. I haven't tried it. It sounds like it would be a good last resort if you ever plan on replacing them though. He also told me to never clean the lens with Acetone. I use denatured alcohol to clean the lens and frame on my hatch cover.

 

[Joe11688]

Thank you for the info Phil. I'll keep that in mind. I was kind of surprised and a little incredulous when he mentioned 3-M 4000 UV. Outside of that stuff being a fast cure adhesive sealant, it really isn't any different than 3-M 4200 which is something I wouldn't use on plastics. I thought Nathan knew what he was talking about. Someone needs to straighten him out.