30 Pilot II rub rail rebedding

[rgano]

I just finished rebedding the stbd rub rail and will be doing the port side when we get some cooler, drier weather in a week or so. Some observations of the notoriously leaky Mainship rub rail follow.

The deck mold-to-hull mold flange has a LOT of short stainless Phillips head screws! There must be one every 4 inches. Whether or not they contribute to the rain and salt spray water which finds its way into my bilge, I cannot say with any degree of certainty, BUT the sealant apparently squeezed out of the flange all along the joint would seem to indicate the nearby screws and flange itself are probably fairly well sealed.

What I can say for sure is that the thirty or so 2.5 inch long number 10 flathead Phillips drive screws holding the molded plastic rail to the hull were driven into the deck mold above the flange with NO sealant anywhere in the vicinity. At some point in the boat's life somebody had squeezed a tiny bit of silicone sealant into the narrow crease between the deck mold and the rubrail, and it was not completely continuous. This sealant was line was about the size of the lead in a number 2 wooden lead pencil - yes, tiny. Oddly, there is no such sealant on the port side.

I smeared a thin layer of sealant of the flange screws just to be thorough, and I laid a good sized bead of sealant just under the line of unsealed holes made by the rub rail screws before replacing the rail. Masking tape lines either side of the narrow gap between the top of the rail and the deck mold prevented the sealant from getting on the surfaces when the rail was replaced onto the flange causing the sealant to be squeezed upwards to form a bead which I then used my finger to remove. Thus all the rail screws were well sealed as they were replaced through the sealant.

This job was done with the boat hanging in the lift, and a couple of lessons were learned. As the stainless trim and the plastic mold were removed, cotton clothesline was used to suspend them from the handrail. It works out best to end up with the trim being suspended well above the joint and the plastic rub rail suspended below the flange to avoid dropping it on the big bead of sealant laid down before rail replacement. Also, the masking tape should be laid down before removing the rub rail to avoid guesswork later. It was a one-man job to remove the rail and clean up the area to ready it for rebedding, but it took two of us to get the aft section of the rail back in place and three people to get the longer forward portion into place.

 

[Comodave]

One thing I would suggest is the holes for the screws holding on the rub rail should be counter sinked before caulking. That way when the screws are tightened up fully there will be room for an O ring of sealant around the screw where it goes into the fiberglass.

 

[USNA74GRAYGOAT]

Bear in mind that I haven’t purchased my 30 yet, so my question may be off base. But could butyl tape be used in lieu of sealant? That is excellent for mounting deck fittings and most of my sailboats I’ve owned used it to seal the hull to deck flanges but using nuts and bolts instead of screws. As you likely know the stuff stays flexible forever and never dries out.
I hope I can avoid going through what you are, but these are boats in a harsh environment and depending on how the manufacturers build them we will always have a project to fix them.

 

[rgano]

If you buy a 30 Pilot II, I would imagine you will find water in the bilge after the first good rain or wet ride because while the flange may be well sealed, the brain trust in the assembly line just powered a bunch of big screws through the rail and into the deck mold above the flange with no effort whatsoever to seal those screw holes. I wet vac the bilge every time it got wet so have an excellent idea of how much got in after every rain until my shed was rebuilt. I cannot see why butyl tape would not have a beneficial effect if you were to place it over the screw holes and then drive them back in through the butyl with the rub rail pressing against the butly in such a way that you would have it also seal the top gap between it and the deck mold with the possibility of having to having to trim it a bit. I like the idea of the sealant (4200) squishing up through that gap (taped off) with the screw being driven through it sealing the hole for sure. Different strokes....hopefully with the same good results. If the job were to be done with the boat on the hard with a bit of scaffolding rather than my awkward method while hanging in the lift that if could easily be performed in a day. Really not hard at all.

 

[Comodave]

The problem with butyl in this application is that the screws won’t compress the rub rail evenly. Butyl needs a lot of compression to seal. I use it all the time when things are bolted down and you can compress it well. I think that the rub rail will get a wavy look where the screws compress the butyl and in between the screws the butyl will hold the rub rail out from the hull. When I use butyl I compress it over 3 days and tighten it each day a little bit. But if you do it and prove me wrong let us know so we will know about more applications.

 

[Bacchus]

My Bacchus website - Projects - Pg 4 has a write up on what I found and how I attacked my rub rail.
This was before I started using and liking butyl tape.
I'm thinking butyl could be effective as a seal around the attachment screws only - no real need to run it continuously in that location.
The place I believe butyl may work very well is at the inside of the deck flange where the top edge of the rubrail meets the deck piece. I ran a bead of caulk along that area but the adhesion and flexibility of the butyl may work even better.
Some claim just a frequent recall of the deck / rub rail is all thats needed... to me that approach works but is temporary and comes loose with flexing. I prefer the more permanent albeit more involved repair and has served me well for several seasons.
I found several of the short vertical screws connecting the hull & deck flanges missing or loose. I replaced them with short bolts / nuts as many of the holes were loose. I did inject some 4200 before pulling the flanges back in contact.

 

[Comodave]

The really good news about butyl is that it seems to have a life of way more than 10 years.

 

[rgano]

I finished rebedding the port side last week and took the bot out on a blustery day to get a good splashing and then thoroughly washed it down with soap and water. Usually that will see a half gallon or so of water sitting behind the engine, but today, not a drop. Hard to imagine that the few unused screw holes under the rub rail contributed that must water. Call me a happy camper for now.

 

[Comodave]

I finished rebedding the port side last week and took the bot out on a blustery day to get a good splashing and then thoroughly washed it down with soap and water. Usually that will see a half gallon or so of water sitting behind the engine, but today, not a drop. Hard to imagine that the few unused screw holes under the rub rail contributed that must water. Call me a happy camper for now.

Congrats on a job well done.

 

[rgano]

One number 6 one inch screw every 6 inches for the stainless trim insert and one number 10 2.5 inch screw one the molded plastic rub rail itself every foot. Lessee, with the wrap around the stern, that's right at 130 screws for the trim and about 65 or sow for the rail. That's a lotta screwing around.

 

[Dougcole]

I finished rebedding the port side last week and took the bot out on a blustery day to get a good splashing and then thoroughly washed it down with soap and water. Usually that will see a half gallon or so of water sitting behind the engine, but today, not a drop. Hard to imagine that the few unused screw holes under the rub rail contributed that must water. Call me a happy camper for now.

Interesting post Rich, and great job, as usual.


I have an 2000 18' Action Craft flats boat that I have owned since new. A few years ago it started leaking in a fairly significant way, but only when it was on plane. Since it's such a simple boat (one through hull) and sits on trailer most of it's life, I figured the leak would be easy to find. Suffice it to say it was peskier than I imagined. It turned out to be a 6" spot under the rub rail where the caulk was gone. When I would run the boat the wake splashed up on it (not a steady stream, just a splash). In 5 minutes of running the bilge pump would come on and run continuously until I dropped off plane. It amazed me how fast the water would get through that little crack and how much came in.



I pulled the old caulk all around and put in a new bead of 4200. No more leak.