Replacement Bang Cap sealant?

[Recoil Rob]

My aluminum original is corroding and there seems to be some loose caulk but the but the transom is good so for now I'm going to go with just a replacement instead of glassing it over.

I've read of all different makes sealant used to seal this, some say 5200, others say 4200, yet others Boatlife caulk.

Looking fro some guidance as to what is the best product to use, short of glassing the whole thing over.

I'd ask Grady but they have no experience in this area...

 

[Fishtales]

Prob 4200 is best. My guess is you'll be in there at some point. It's just time with that joint. They make a plastic bang plate now that you can get from your dealer if interested.

 

[DennisG01]

Yeah, either LifeCaulk or 4200. Just know that both of these are still a decently strong adhesive - although nowhere near as strong as 5200. Really, since it's secured with mechanical fasteners, you only need a sealant, though. Something like LifeSeal would would be perfect. But LC or 4200 would work great, too - and it won't be "too" hard to remove the cap in the future.

 

[efx]

The key here is not what sealant is used but how well it penetrates the gap and what top profile it takes. I’ve redone a bunch of GW transoms and take off the old plate, really clean out the old sealant, chisels and hammers are required. Sand everything clean. Use compressed air. Dry it well. Then start with small beads to get into the crevice and build up from there. Lay in the new bang plate, cut to fit the length exactly and fasten it. There should be some oozing of sealant. Clean it up. The next part is the ends. Same process. It takes time to do well.

 

[Fishtales]

Sad how the joint/cap was designed and executed. I think this is going to be a big issue in the years to come for many owners.

 

[Recoil Rob]

Thanks all.

efx, sounds like you're in the business, anywhere near CT?

 

[DennisG01]

Sad how the joint/cap was designed and executed. I think this is going to be a big issue in the years to come for many owners.

My parents are buying a 192 Tournament and even though things look good, I'll probably still pull the cap off. Most likely, I'll just glass it so we never have to worry about it again. The plus, for me, is that they're concerned much more with functionality than aesthetics... which makes my job easier!

 

[seasick]

If it ain't broken, don't fix it, as they say.
Of course, it may make sense to check the transom under the cap but that is a decent size job. An inspection for apparent leaky seams, staining, evidence of a wet transom etc. could be done first.

I am also not sure if adhesives like 4200 are appropriate. Those things are intended for applications where the parts don't move in relation to each other. My question is; Does the transom at the bang plate end, flex under power? I really am not sure but if it can flex, then a sealant would be preferable over an adhesive. Glassing or epoxing the are under the cap, could lead to micro cracks if flexing occurs.

 

[Doc Stressor]

Grady told me to use 5200 when I replaced mine. And to work it well down into the wood leaving no voids. I am getting cracks in the gel coat after a 1.5 years. I put a jack plate on at the same time so that might contribute to flex. I don't see why a more flexible sealant such as Lifeseal wouldn't be appropriate.

 

[oliver305]

3M 5200 is a good product, I've used this for everything from patching my boat, to roof repairs. This is by far the best product on the market. The UV resistance is what sets this product apart from others.

 

[trapper]

I went with Sicaflex 291 used it for years on my wooden commercial troller, found it to stand up well to west coat abuse.

 

[seasick]

3M 5200 is a good product, I've used this for everything from patching my boat, to roof repairs. This is by far the best product on the market. The UV resistance is what sets this product apart from others.

The problem with 5200 is that if you ever need to remove the cap for whatever reason, the 5200 can actually peel off the gel coat or fiberglass when you pry the cap off. It is for the most part a rather permanent adhesive,
If you are applying 5200 under the cap only, UV resistance isn't a concern since it won't be seeing the sunlight.
Life Seal/caulk products are good choices. Pettit has some new sealants available in both cartridges and tubes for both above and below the water line. They are very new but I might give them a try
Here is one of the new products

Pettit | UV Resistant Adhesive Sealant

 

[DennisG01]

Oliver, just a heads up, 5200 is NOT rated by 3M to be UV stable. Plus, as Seasick mentioned, it is VERY strong. It's bond to the gelcoat is stronger than the bond between the gel and fiberglass. Truth is, there are very few places on a boat where 5200 is the appropriate sealant. It's great stuff for the right purpose - there just aren't a lot of places where it should be used. It gets thrown around a lot on forums and youtube as the be-all, end-all sealant - but if you talk with any, credible person, "in the business", they'll tell you what we're telling you. Again, just something to be aware of for the future.

I can see using it to seal the gap between the two sections of glass. But as for the bang cap itself, something more flexible, like Doc said, would be more appropriate.

 

[SkunkBoat]

I would use G/Flex epoxy filler...over fill and sand it.. ... maybe even lay in a strip of glass.. Then use 4000uv when you mount the trim

 

[DennisG01]

I would use G/Flex epoxy filler...over fill and sand it.. ... maybe even lay in a strip of glass.. Then use 4000uv when you mount the trim

I'm doing the bang cap on my parent's 192 that they just got and I may actually end up doing that. Definitely got to use some glass to give strength to the epoxy (I still have a couple gallons laying around from a previous rebuild). They don't care much about aesthetics - I may just use a strip or two of 1708 and be done with it.

 

[family affair]

Oliver, just a heads up, 5200 is NOT rated by 3M to be UV stable.

Dennis, not to argue, but I am curious. Have you ever seen 5200 weather away from sun exposure? 3m states the color is not UV stable like 4000. 4000 won't turn yellow. 3m does not state that 5200 should not be used in an exposed application.
I've had 5200 FC exposed for 10 years. It hasn't yellowed, cracked, or debonded. The boat is garaged, but has spent plenty of time in the sun.

 

[Fishtales]

Factory went to Plexus I was told to improve the joint on newer boats.

 

[DennisG01]

Dennis, not to argue, but I am curious. Have you ever seen 5200 weather away from sun exposure? 3m states the color is not UV stable like 4000. 4000 won't turn yellow. 3m does not state that 5200 should not be used in an exposed application.
I've had 5200 FC exposed for 10 years. It hasn't yellowed, cracked, or debonded. The boat is garaged, but has spent plenty of time in the sun.

That's a good question. I know that 3M doesn't list it under their "UV Stable" section, but have I ever actually seen it? I can't say for sure - at least not that I can remember. But then, in the number of decades I've been in this business, I've never used it (or known of anyone that has) in a spot where UV would be beating down on it. I do like the stuff - but given it's small application window and since there are other products that ARE UV stable, there's always been better choices.

 

[PointedRose]

Both 4200 and 5200 have strong bonding and sealing qualities. The difference is 4200 has more flex than 5200.

 

[Fishtales]

The prob is by the time you need to seal the joint, water has likely already gotten in and you are putting lipstick on a pig. I'd say you could use just about anything because if there is water in there you are either going to repair it or wait until the transom delams, core rots and turns to mush or starts to flex to the point you are forced to fix or toss.