Reinstalling Aluminium deadlights

Rick · Post by **Rick** » Tue Oct 07, 2008 12:30 pm

I just completed painting my Aquarius A21 deck and cabin exterior with Perfection and Interdeck. The next step is to repair and replace the deadlights. I removed the old deadlights and found very little sealant between the exterior aluminium frames and the cabin. It looks like old butyl caulk that was thin and hard. The acrylic was surrounded by a hard plastic ribbed gasket and inserted into the frame, but there was no additional sealant.

So, my question (finally) is: What do you recommend I use for sealant in the two different areas - (1) to hold the acrylic in place inside the aluminium frame; and (2) to seal the aluminium frame into the cabin openings. After searching previous posts, I was thinking of using buytl caulk to form a new "gasket" around the acrylic and that many of the polysulfide caulks would work between the cabin and the frames. What do you think? Suggest?

forrest · Post by **forrest** » Tue Oct 07, 2008 6:10 pm

I used silicone for the acrylic to the frame and Dolphinite for the frame to house. A lot of people dislike silicone, but it seemed like a good use for it.
I put them in a year ago and they are not leaking...yet.

Hirilondë · Post by **Hirilondë** » Tue Oct 07, 2008 8:12 pm

I would recommend carefully reading this post: http://plasticclassicforum.com/viewtopic.php?t=3361 Tim thought it was important enough to sticky it.

I think it is really important for boat owners to know the characteristics of the different beddings and adhesive sealants out there. There are so many varied needs for water-proofing on a boat. Choosing a product has to be based on the requirements of the application and products that address these.

forrest wrote:A lot of people dislike silicone, but it seemed like a good use for it.

Umm, no, there is no good use for silicone.

Rick · Post by **Rick** » Tue Oct 07, 2008 8:43 pm

Thanks for the reference to the sealtant chart. I'm not sure how much adhesion I want for the deadlights to not leak, but be removable if (when) they do in the future. I'm thinking of using either LifeCalk, 3M 4000UV or Sika 291LOT between the frames and the cabin.

It looks like Sika 521UV, Sika 291 LOT or Boatlife LifeSeal would work for bedding the acrylic in the aluminium frames. Is the consensus that Lifeseal contains silicone, so it should be avoided?

I've read some posts that recommended using butyl caulk to bed the deadlights. What would be the advantages/disadvantages of using it?

Finally, I was told to lightly sand the edge of the acrylic before applying the sealant to increase its adhesion. Is this recommended?

Thanks

Hirilondë · Post by **Hirilondë** » Wed Oct 08, 2008 5:28 pm

You're definitely on the right track. Can the Acrylic be attached to the frame as a separate step from installing the frames to the boat? Using 2 different sealants simultaneously can be a real pain. If so, then using Lifecaulk for the frame to cabin would be a great choice. As it is a polysulfide, it shouldn't be used for the acrylic.

I have never used 521 UV. Does it require a primer like 295 UV does? Can it be applied in direct sunlight? Those are the 2 reasons I haven't used 295 UV. I am going to have to look into that more. It might be a very user friendly option with good results for use with plastics. I have used Sikaflex 291-LOT for polycarbonate and acrylic with fair results, but I keep looking for a better bond to the plastic without getting into multi-stage processes, or restrictions concerning sunlight during application and curing. Sikaflex 291-LOT is slightly more adhesive than I wish it were (except to plastics like acrylic and polycarbonate), but I like everything else about it. I like that there is a long working time, and it cleans easily and well even after and hour or more. This isn't so with most other sealants.

Butyl tape is used a lot in commercial glazing. Butyl caulk is messy. But both yield excellent results. I find the tape to be a nuisance as exactly the right thickness has to be used for most applications, and it is often hard to gauge what thickness is needed.

Rick wrote:Finally, I was told to lightly sand the edge of the acrylic before applying the sealant to increase its adhesion. Is this recommended?

It helps, but be really careful not to scratch the viewable portion.

Rick · Post by **Rick** » Thu Oct 09, 2008 1:21 pm

Thanks for the info Dave. I like the idea of attaching the acrylic first and then installing the frames into the cabin later. The acrylic fits into a channel on the outer aluminium frame that is rivited closed around the acrylic. The width of the channel is 1/4" and the 3/16" old acrylic was inserted into a hard plastic gasket and then put into the channel. I'm leaning toward putting the butyl tape into the channel, inserting the acrylic and then riviting it shut. I've found a good selection of butyl tape at the local auto parts store. I'm just bothered by the fact that it isn't sold at any of the marine stores and the seller of the acrylic recommended silicone and not butyl to bed the plastic. Does anyone have any experience with Lifeseal (silicone & polyurethane) to bed the acrylic?

I'll go with your suggestion and use the Lifecalk to seal the aluminium frame to the cabin side.

Jason K · Post by **Jason K** » Thu Oct 09, 2008 2:07 pm

Rick wrote:I'm just bothered by the fact that it isn't sold at any of the marine stores and the seller of the acrylic recommended silicone and not butyl to bed the plastic. Does anyone have any experience with Lifeseal (silicone & polyurethane) to bed the acrylic?

Hi Rick,

I just did this, coincidentally. I've also used butyl (in a tube) in the past. I like the LifeSeal - it's not as sticky and stringy as butyl. This makes for an easier and cleaner installation. I let it cure for little while (but not to full cure) and was able to get a pretty crisp tape line. Butyl will tend to pull away with the tape, leaving a messy edge. I don't have any experience with butyl tape.

LifeSeal also won't eat the acrylic. Time will tell how well it works on the windows. I used it on my plastic clutches about a year ago and have no problems to report.

bcooke · Post by **bcooke** » Thu Oct 09, 2008 3:26 pm

I'm just bothered by the fact that it isn't sold at any of the marine stores and the seller of the acrylic recommended silicone and not butyl to bed the plastic.

Marine stores are a lousy source of advice, especially the big chains. Kind of like boatyards in my opinion. Home Despot gives some pretty crappy advice too now that I think of it. The sellers of acryllic rightfully have nothing bad to say about silicone because they aren't the ones trying to get it off the boat prior to painting. Marine applications are a pretty small segment of their sales. In today's race for the cheapest sales price, knowledgeable sales staff are nearly impossible to find and too expensive to hire. Why pay $20 an hour for someone that knows what they are talking about when you can hire someone freshly released on probation (complete with fancy GPS tracking ankle bracelet) for $8 an hour. If you don't know what I am talking about I can take you for a tour of my local Home Depot. Half the 'sales staff' are sporting the latest in ankle jewelry.

In a world drowing in marketing hype it can be tricky getting good information. Sort of like the recent political debates.

Do your own research. It would be nice to trust the advice of others but most of it is crap and not worth listening to.

Mine included :-)

bcooke · Post by **bcooke** » Thu Oct 09, 2008 3:28 pm

PS.

Just curious, are you using acryllic and not poly-carbonate? (lexan)

Rick · Post by **Rick** » Thu Oct 09, 2008 4:35 pm

Jason, thanks for the info and link to your repair job. It was very helpful. My situation is a little different, as my deadlights are mechanically clamped to the openings in the cabin with screws. I had to drill out many of the screws that broke when I tried to remove them. I'm planning to drill through both frames and use cap nuts on the exterior to clamp the frames to the cabin.

Just curious, are you using acryllic and not poly-carbonate? (lexan)

It appears that the tradeoff between acrylic and lexan is that the former has greater resistance to scratches and handles uv better, while the latter is stronger (bulletproof). I haven't been shot at yet - and hope to keep it that way. Actually, my boat is a 21' trailer sailer that will be used for inshore trips and overnighters. I didn't think the added strength of the lexan was necessary.

I'll post some pics of the completed job, but it won't be for a while. My acrylic dealer just called and said it wouldn't be available for at least a week. Luckily my 1972 project boat has a few other jobs to keep me busy over the long weekend!

bcooke · Post by **bcooke** » Thu Oct 09, 2008 5:57 pm

I didn't think the added strength of the lexan was necessary.

Fair enough :-)

bcooke · Post by **bcooke** » Fri Oct 10, 2008 6:58 pm

BTW,

I had just sanded the bottom of a 49 foot sailboat which might explain why I was a bit cranky yesterday :-)