Bedding deck drains - sealant choices?

[Beersmith]

After finally finishing the deck paint job, it is time to install some deck hardware. Right now my objective is to get the deck and cockpit drains installed so rain has somewhere to go.

The deck drains are all bronze, and the cockpit drains are UV stabilized plastic of some sort.

I had always intended on using butyl tape for items that will be bolted down, per Mainsail's instructions. However, these drains and a few other fittings are to be installed with small screws. It seems that butyl won't really work with screwed on fittings, only bolts.

What sort of sealant should I use for these fittings? I am adverse to anything "permanent" such as 5200. After taking my entire boat apart for this rebuild, I curse anyone who used such things on this boat. I read that polysulfide sealants cannot be used with plastic, so that is out for the cockpit drains.

Right now I am thinking either Boatlife Lifeseal or Sikaflex 291. Am I on the right track? Which would you recommend of these, or what alternative should I consider?

Also, I understand the techniques of bedding, but one aspect has me confused. I plan on using masking tape around and on the fitting itself to save the mess, applying the goop, screwing down lightly, let the goop cure some, then tighten down.

However, if I apply the goop under the screw heads, what technique do I use to make sure the excess doesn't get inside the screw head/slots when I wipe off excess?

[Target9000]

So why do you say butyl will work for bolts but not for screws?

[zeehag]

5200 isNOT a bedding compound, as is written on the tubes. 4200 is the bedding comkpound o f3m. life seal and some others also have good bedding compounds, and butyl tape, per mainsail.

[Beersmith]

Originally Posted by Target9000

So why do you say butyl will work for bolts but not for screws?

The technique usually described for butyl involves applying it to the underside of the fitting, and torqing the nuts from the bottom. It is said that you do not want the bolt to spin at all, and a screw can only be spun into place.

I may be wrong on this, if butyl would work fine with screws then I'm all ears.

[Target9000]

Well... I've been using it for screws...

Seems to work just fine. I find the most important thing is to get the tape under the fitting. The tape around the fastener head seems almost secondary. As the screw pulls the fitting to the deck its going to smush the butyl into the screw no matter if it is turning or not.

[Beersmith]

Originally Posted by Target9000

Well... I've been using it for screws...

Seems to work just fine. I find the most important thing is to get the tape under the fitting. The tape around the fastener head seems almost secondary. As the screw pulls the fitting to the deck its going to smush the butyl into the screw no matter if it is turning or not.

maybe I'll just do that. I ordered a few rolls from Mainsail so its already on the way. Plus, butyl it won't be nearly as bad to remove and re-bed if I change my mind later.

[elutherian]

beleive it or not i got a freind in the funeral business and i buy the butyl they use to seal caskets its 2 1/2 wide by 1/4 thick and under cleats and any deck fills or other assorted deck hardware i have installed in the last 10 years bolt or screw i have had no leaks and the hardware i have changed where butyl was used it was easy to remove said hardware and no damage to the finish occured

[Target9000]

Its like a joke on our boat now. "We put that sh*t on everything."

[Beersmith]

Originally Posted by elutherian

beleive it or not i got a freind in the funeral business and i buy the butyl they use to seal caskets its 2 1/2 wide by 1/4 thick and under cleats and any deck fills or other assorted deck hardware i have installed in the last 10 years bolt or screw i have had no leaks and the hardware i have changed where butyl was used it was easy to remove said hardware and no damage to the finish occured

Originally Posted by Target9000

Its like a joke on our boat now. "We put that sh*t on everything."

I think I'm sold on the idea of just using butyl

[S/V Alchemy]

Originally Posted by zeehag

5200 isNOT a bedding compound, as is written on the tubes. 4200 is the bedding comkpound o f3m. life seal and some others also have good bedding compounds, and butyl tape, per mainsail.

Agreed. 5200 is great for keels, but 4200 is the number you want if you ever, ever need to get it off again.

The PO of my boat used 40 bolts and a bead of 5200 to secure the aluminum pilothouse roof to the steel inward flange of the pilothouse sides.

Guess what took the most effort to remove? 5200 is a great glue first.

There are other choices, but they should be equivalent to 4200/Sikaflex 291, which are both polyurethanes.

[Saltyhog]

I forget where I read about this, but it seems the latest in above the waterline sealants is butyl caulk . I would think it would seal around the screws pretty well. I understand your concern regarding the screws turning in the sealant. But on second thought, I think the butyl tape would "self heal" after a bit of time. I think the butyl caulk would self heal immediately.

[S/V Alchemy]

Originally Posted by Beersmith

I think I'm sold on the idea of just using butyl

Actually, despite my endorsement of 4200, I like butyl for compression loads where the mated pieces aren't likely to move. I used it for fitting circular opening portlights last year and it works well.

The world encompassed: Bright and butyl full

I also endorse anything Maine Sail says on this or many other topics concerning best practices. You should read his treatise on crimping!

[mrm]

There is another sealant chemistry which is rarely if ever mentioned here. It is methylated silanes. A good example of a product using this chemistry is Terostat MS 939 from Teroson (a Henkel group). It performs splendidly as a joint sealant between metal roof plates and is also widely used in car industry. UV resistant, can be painted over and has nothing to do with silicones.

[Cheechako]

I wouldnt worry about getting sealant into the screw heads, it doesnt seem to inhibit taking them out. I always put sealant on the screw itself as well as under the hardware being attached. It's hard for me to visualize butyl tape squeezing appropriately into the threads and surrounding hole like sealant. One missed spot and the water will be running into the surrounding fiberglass etc for a long time. Still there are a lot of convincing arguments for butyl here. BTW, isnt butyl what they use on Car windshields? I've had 3 replacments that leaked in the last 15 years.... still I would use it for plexi windows etc. But hardware with multi screws? I'm not convinced ... How do you keep water from laying under the screw head?

[roverhi]

I've used LifeCaulk for more than 4 decades without any problems. It's easy to clean up with paint thinner and remains flexible forever.

Had to remove a couple of fittings that I used butyl to seal and it left an unholy mess. My gelcoat is old and porous and it left a big black stain. Be careful removing Butyl especially if you have to resort to a solvent to clean it up. Will still use butyl in areas that have lot of movement like portholes but dialing back on use in other areas. I wouldn't worry about using it with screws. Have done it and it's sealed without any leaks into the deck core.