Solutions from the J-27 Yahoo Group on replacing windows:

The problem: Replacing windows on the J-27. The old windows were sealed with a soft rubber bedding compound, maybe a butyl rubber. What material works as a replacement?

Comments provided by some Yahoo Group members:

Replace with Sikaflex lot 291 black caulk? Bad idea, since the black would show around the edges against the white of the cabin. Paint the area around the windows black first? It might work. However, don’t use thinners or acetone to clean the Sikaflex, as it will trash the window plastic.

Using “life caulk”? It has held up for nearly 5 years. Was the ONLY adhesive/caulk good with poly lens material.

Another member used the life caulk and it held up for ONLY about 5 years.

3M 4000 UV is good. Sand the windows a little before sealing, so the sealant has something to stick to. Also, add more screws than original had, and be sure and seal those screws.

Another ended up using "butyl sealing tape." This appears to be what was used originally at the factory, although he called the factory and they had no clue. He used 1" wide by 1/8" thick tape. It provides a nice clean line with no mess and never hardens. Wraps around the corners no problem. He found it at an RV place, seems to be a favorite among that crowd. We'll see if it works and for how long, but it certainly was easy to work with and looks good.

Another did his windows with slightly smoked acrylic 1/4" plastic. Used Life Seal sealant and it worked well. No more leaks. He drilled the fastening holes ever so slightly bigger for possible expansion. If you mask the area around the windows, the excess can be easily trimmed off. Plastic and sealant was under $50. total and the boat looks good with the darker windows. He would not use Silicone, sooner or later it just does not do the job.

Another solution came with an offer of help, so it is quoted in its entirety:

I just replaced my original ports with Lexan which I'm told only comes in one color; a medium smoky grey. I fashioned a 3/4" thick template from a scrap piece of MDF which holds an edge well when routing against it. I made the template 1/4" larger than the original portlights. I rough cut the Lexan on my bandsaw and finished it with a router using a 1/2" roundover bit which gives the 1/4" Lexan a slight roundover...I think it looks pretty slick. After routing, I wet sanded the edges with 400 and 600, then polished with a rouge wheel for a sheen. I affixed the Lexan with a double sided tape without screws. The tape I used is made for automotive body mouldings which I bought at a local NAPA store. So far, so leaks...I'll keep you posted. I bought the Lexan from a local plastics distributor. I paid $40 USD for a piece large enough to do the ports and companionway. From reading these postings. I realize there is a lot of talent out there, but I would be more than happy to help anybody who needs new ports. Now that I am set up, it takes about an hour to make a set. I work for beer!

Newport, RI
Cuckoo Voodoo

One response to this, however, did question whether taped in windows were strong enough in open water sailing (as opposed to lake sailing).

The butyl sealing tape did not last 3 years. Maybe if I used more fasteners. It tended to sag out of the joint from the heat. The proper way is to use Sikaflex -295 UV with 209-D primer. Be ready for the sticker shock on the primer - it is about $75! The 295 is about $19. Jamestown Distributors in Bristol RI stocks them both. You can find the directions at

Dan Simkins
Burlington VT