Rub rail - slit behind rail

Major Tom · Posted: Wed Jul 29, 2020 3:31 pm Post subject: Rub rail - slit behind rail

I had 9 of the rub rail rivets come loose on the forward starboard side, and am repairing it. My boat is a 2005 CD22 and it has the slit behind the rub rail, running the length of the rail, as far as I can tell. The rivet holes are in line with the slit, and the slit isn't very deep, from what I can tell, maybe 1/8"-1/4". I think I read in one of the posts about some boats having the slit, but I can't find it again and can't remember the detail. Anyway, should I leave the slit as-is, or try to seal it with 4200 or 4000? Seems like water will definitely get in there due to that slit and will corrode the rivets? OTOH maybe the slit will allow it to dry better? And I can't remember the purpose of the slit, other than possible drying, I can't see the advantage. For now I'm just repairing the 9 broken rivets to get back on the water, but at some point I'll need to take both rails off and do them all with SS screws/bolts.

Thanks to Sunbeam's excellent write-up and some others, it's going pretty smoothly. FWIW, some of the caulk blobs were very hard, probably glassed over. They were difficult, I had to use a hacksaw blade and a small sheetrock hand saw to carefully wear down the thin layer of glass. I tried a small grinder attachment for a drill but it was too easy to go too far. After gently tapping from the outside with a punch, then going back inside to trim the now-slightly-raised glass and caulk, I got them off.

I started with 8 broken rivets but as I was working with the rail I pulled it out just a bit too far and the 9th one pulled out from the outside, even though I hadn't touched it. But it didn't come off the rivet head like the others, the whole thing pulled right out. And instead of a thin rivet rod and mandrel like the others, the aluminum rod part that goes through the hull was deformed and much larger than the others... almost like a blob of aluminum. Maybe it mushroomed somehow, which is odd. Or did the factory use some kind of "blob rivet" that was sealed in the glass? Luckily I was able to chisel off the rivet head and separate the mushroom and drilled a clean hole for the new screw.

Thanks for the help!
Tom

Major Tom · Posted: Wed Jul 29, 2020 5:18 pm Post subject:

I took a closer look at the slit, and I answered my own question, at least on that part... the slit is only about 1/4" deep, and by simply sealing each hole well before inserting the screw, my new screws will be well protected. But for the old ones, well, I'm sure I'll be taking both rails off completely one of these days and redoing them all... it's far too easy for water to get in that slit and stay there.

But I'm still curious as to its purpose, it's effect on corrosion, and the "blob" mushroomed rivet. If I'd been tapping too hard I could see it would mushroom like that, but I didn't tap that one at all, it just pulled out with very moderate force, from the outside of the boat. Hmmm.

Also, in case it helps anyone else, most of my screws are ending up to be 1.25", not 1" as many have said. If you're ordering in advance of tackling the job, so you can't really measure yet, order some of those too and maybe even 1.5".

tsturm · Posted: Wed Jul 29, 2020 5:52 pm Post subject:

Major Tom · Posted: Fri Jul 31, 2020 11:45 am Post subject:

Well it doesn't split into 3 legs but it had mushroomed pretty well, apparenlty. Anyway, I got those finished for now and can get back on the water, let's hope the other's don't start pulling out,a t least until Fall! But I can see that I'll need to pull both rails at some point and replace all those rivets.

colbysmith · Posted: Tue Jul 08, 2025 8:38 pm Post subject:

Resurrecting this thread, as it seems to be more recent than the ones from 10 years ago. I had the tailend of my starboard front section of rub railing pop away from the boat last week. This was just about under my forward cleat, or next to the cabin helm. Pulling the rubber insert out, I found that the vast majority of the rivet heads were popped off, so I drilled out the few remaining and pulled the rail off. The only thing holding the railing on, other than about half a dozen rivet heads, was just the rivet bodies. I did see Sunbeam's write up from I think 10 years ago. The material on the inside of the riveted areas in the cabin, is more glass, so I don't think I'll really be trying to hammer the rivets into the boat. Tomorrow I'll plan to drill all the rivets out, from the outside. And probably go all the way thru into the cabin. This section is very easy to access from inside the boat, as it's beside the helm and then along the starboard side in the V-berth. I'm guessing the best repair will be to use ss machine screws and acorn nuts. Or nylon lock nuts. And put a generous amount of sealant on the screws where they go thru the hull. Then again, I kind of like this idea:

thataway · Posted: Wed Jul 09, 2025 11:41 am Post subject:

A good way to remove enough of the inside material over the inside end of the pop rivet is to use either a Dremel or Rotozip with a flexable shaft and cutter head to remove the material to expose the end of the the pop rivet. That way you can tap the pop rivet to the inside. and avoid trying to drill them out. I would put some tufgel under the head of the rivet, to decrease the reaction between the SS rivet and aluminum rub rail channel.

ssobol · Posted: Wed Jul 09, 2025 11:44 am Post subject:

colbysmith · Posted: Wed Jul 09, 2025 12:40 pm Post subject:

Just finished drilling out all the rivets. 29 of them. Didn't want to go the route of grinding down the material inside and pushing the rivet bodies through due to dust cleanup then. Probably going to go the machine screw/washer/nut route, but will decide that based on what is available at the hardware store today. Colby