What's YOUR favorite bedding compound?

I actually was forced to *buy* and *use* silicone sealant this year :-(
Unfortunately I needed to reseal the astrodome and if you are sealing acrylic plastic, you CANNOT use any sealent that has any solvents in the formula or it will craze your plastic. Silicone is the official reccomendation  Bloody horrible stuff to work with if you want a neat finish, and getting the suface prep good enough so it actually sticks properly is a bitch.

Generally speaking  I like a good butyl (rubber) mastic or a polysulfide sealent for above waterline stuff.  I used to be able to buy a butyl mastic called Farocalk.  Unfortunately the company went under and you can no longer get it. Might have something to do with it having a useable shelf life of about ten years and several years after opening.  Fortunately there are alternative brands but they dont sell it in the retail marine marketplace

Most of the modern sealents are only useable for a few months after opening however carefully you re-seal the tube and even if you keep them in a ziploc bag in the fridge with a sachet of silica gel.  If you just put the cap back or plug the nozzle, it will set in the tube and you'll be lucky if you find any thats still useable a month later even if you rip the bottom out. 

Under the water this year I've been using one of the multitude of Sikaflex products.  I probably haven't chosen the best one for the job, but the need to 'git er done' and local avalibility wone out.

Remember they dont call it 'silly-con' sealent for nothing . . . .

I have been using butyl lately and have been very pleased.  The stuff is a pleasure to work with, especially because one is not time limited.  That is, butyl never 'sets' which means plenty of time for fitting and adjusting and tightening

So far I have done portlights and stanchion bases with it with success. 

Christopher

I would most earnestly urge you away from 5200 for anything above the waterline. It's great for many purposes (say, thru-hulls) but for bedding a handrail or hardware, it's a nightmare. All bedding compound will eventually fail. Nature of the beast. 5200 WILL take gelcoat with it - I know from painful experience. There are products you can put on it that will soften it but why not just use 4200 or better yet 4000 for topside stuff? It's made for that purpose and much easier to remove when necessary. There's not much difference between the two except that 4000 is a newer product and has UV protectant in it so it doesn't turn yellow. My two cents...

BTW, I do know a few people who've used butyl rubber to bed portlights with some success. It never gets hard but they had problems with it oozing in hot weather. You can buy it at motorhome supply stores.