Rainproofing (Sealing) A Cabin

[JustJames]

Over the Xmas break, SWMBO and I booked our boat into Soldiers Point Marina in Port Stephens, which turned out to be a great way to spend a week, heading out to snorkel and fish most days.  Less delightfully, it turns out that our boat leaks.  It leaks where the all around white light base is attached to the front of the hull, it leaks where the windscreen meets the scuttle and it leaks around the small side windows on the cabin.  For most of these I figure a bead of sealant is called for, with the light fitting being removed and resealed.

 

Any suggestions on how to tackle the job/s are most welcome, and especially recommendations on what sealants will work well.  Every sealamt that I have looked at seems to have some or other drawback, so I am particularly keen to hear advice from anybody who has tackled this sort of job.

[BaitDropper]

Hi James,  Leaking things on a boat is annoying for sure.

Every sealing job is different, depending on what is actually leaking. Generally fittings and the like, the water will track down the threads of the screws used. Windscreens and side windows, well, I used to be involved in making and installing those, again, it depends on the actual type of fitting method etc etc.  If you want to post up photo's of what you have, including when things have been removed, that would be ideal.

As far as what type of sealant to use, I was always a firm believer that standard silicone, has no place being used on a boat to seal anything !!.

Now, Sika urethane, the one designed to be used for above deck and underwater situations ( 291 ) is a perfect marine sealer,, the other day I mistakenly bought what I thought to be Sika 291, it turned out to be a Sika Marine silicone !!  first time Ive seen that, so for above water line, it may well be fit for purpose.

Many people are put off by the likes of Sika 291, because they think of the issues that can be had should they ever have to remove it again, then use a crap sealant, then it inevitably leaks and have to start the process all over again. Use the best product available, I always use Sika 291 for any adhesive or sealing job, cause that's what it's designed for. Like all sealing jobs, prep is the key and surface preparation being the most important.

As mentioned, have a crack at the job, strip things down and put up some Pic's, I'm sure others will chip in and help. Everyone will have different methods or products they use for certain, I'll sure help and tell you how or what method I used for installation,   as mentioned earlier, there's nothing worse when you have little leaks everywhere, very frustrating..

[riveRecon]

I have an Aluminium boat so might be a different experience. I agree with the sika 291 above. Works great at sealing and bonding jobs I have done around my casting deck. I have also used the grey gutter sealer/silicon along my gunnels which has lasted really well in the weather permanently for three years now. I use metho to clean and scrub first before applying the sealant. I hope that helps.

[JustJames]

Sika 291 is the obvious option, but caims to be for interior sealing.

 

Through my work I am able to get Wurth products, so I have ordered Wurth 08932913, which is a "1-component polyurethane adhesive and sealant specially developed for use in boat building and shipbuilding. For variable, waterproof, weather-resistant sealing tasks and simple bonding for indoor and outdoor use, including below the water line after curing."

 

TBH, I suspect that HOW sealant is applied is going to be more crucial than choice of sealant.  I'll take some pics over the weekend when I have the boat out of its covers.

[BaitDropper]

Hi James, the application of the sealant is important, BUT there are many methods or ways to seal, depending on what you have. PREP is your biggest factor.

Example,  Just like the installation of car windscreens, a " Dam" rubber ( foam ) is used to pack out the screen to ensure the thickness of the Urethane is correct,, plus to stop excess Urathane oozing inside. Where boat side and front screens are glued straight to the fiberglass itself, you don't want the acrylic or glass to be pushed hard back on the substrate. Even aluminum framed glass/Acrylic panels, should be done the same way, which allows for the flex of the boat and then maintains its seal.

It's not rocket science, but there are " better methods" of doing the job, and achieving a longer lasting seal, if you follow.

Photo's will be good, I'm sure it will be successful.

Oh, and the Wurth products are very good.. 

Sika 291 is rated for below water line.

Edited January 3 by BaitDropper

[JustJames]

OK...pic 1 below shows the area around the front of the windscreen and my prime suspect for water ingress, which is the fitting for the all around white light.  I have hand drawn a red oval(ish), which indicates the area where water is dripping from on the inside of the boat.  There is a bowl in the ceiling, which contains the interior light, and that is where water is dripping from.  I suspect that it is getting in at the all around white light fitting, but I can't rule out the windscreen.  If the windscreen is the culprit, can I get by with adding a bead of sealant around the base, or does the windscreen frame need to be removed, or loosened before sealant is applied?

 

 

Pic 2 shows the side window.  These are held in place with just 2 screws, highlighted with red cicrcles, which isn't going to do much to aid in waterproofing.  I am inclined to add a bead around the top of the windows without removing them but I am open to advice from people who have tackled this sort of job before.

 

[BaitDropper]

 

The trick to finding/fixing leaks is to go through an elimination process. Firstly, I would sit in side the boat, while someone uses a hose over the white light fitting and try and create the leak there first, only put water on the white light fitting, not the windscreen If indeed you find one there, that should be simple enough to seal up.  As far as the front windscreen goes, sealing up the bottom could have a detrimental effect, creating a swimming pool effect, I would say, underneath the aluminum, it will have screw fixings, unless it's only held in by Urethane ( which I doubt ).  Same with the side window, just having 2 screws doesn't help, for sure, but depending how its fitted ie, urethaned in, if the seal has broken, it may very well be better to remove it, add a couple more fixing screws and re fit and re seal again.  But again, by eliminating potential leak points as you go, is the correct way to do it in my opinion.