What type of adhesive?

[240da]

I'm in the process of replacing the port and starboard bilge area vent covers (they are about 54" long) on our Sundancer. SeaRay provided me the new covers (at reduced cost) but the install is my responsibility.

I believe the failure is due to the use of an adhesive that is far to rigid and that during cold weather the cover cannot contract freely resulting in excessive tensile stress along the faying surface, and eventually cracking.

Anyway, I got one of them removed, (inch by inch), it was a real pain, the adhesive they used actually pulled some of the gelcoat off! Fortunately, all of that will be covered by the new part.

Does anyone knows what they used?

I'm thinking of going back with 3M4200 after I do a compatability test on the cover material.

Thanks in advance for your thoughts!:smt001

 

[techmitch]

They probably used 5200 and you may not even need something as strong as 4200 but i guess your test will tell you that.

 

[240da]

techmitch:

Thanks for your response.

It is not 5200; it is much, much harder. I just can't understand why they didn't consider the coeffecient of thermal expansion issues. This stuff is so hard there is no way it allows the cover to contract (without excessive stress) in cold weather. Somebody dropped the ball!:smt009

 

[boatmailster]

you can use 4200 fast cure under vents and silicone around to give nice finish.

 

[Fishnut]

you can use 4200 fast cure under vents and silicone around to give nice finish.

How do you use it under? The vents look like they are caulked on the outside but that's it.

 

[Kurt]

240da, Post some pics of your replacement, step by step if possible. I am curious what is holding those piece of junk Mickey Mouse vents in place beside the glue. I know we talked about this before so I am interested in seeing the process as I know it is going to happen to mine some day. Thanks and good luck.

 

[240da]

Kurt:

I don't have any pictures yet but I'll try to get some. Perhaps as yours is a 2007 you have a different adhesive, something more flexible. Both of mine have cracked (during the winter) and I'm convinced it is because the adhesive is far too rigid and does not allow the vent material (similar to Cycolac) to contract. As it tries to contract the faying surface of the vent cover becomes subject to very high tensile stress (due to this contraction) and ultimately fails. All of my vent cracks eminate from the faying surface.

There are no mechanical fasteners, only the adhesive and some very flexible caulk/bedding material. The caulk is not at all structural and not the cause of the problem.

 

[Kurt]

So the cracks eminate from the union of the vent and the fiberglass on the top edge? I agree then the cracks would be a result of severe tension. But I thought Cyclolac material such as windows was made to flex without developing stress cracks. At any rate I think this should fall under warranty or recall issues as operation of the vent is imperative to boat operation. Like I have said since the first day I picked up my boat, the vents are the poorest design on the whole boat. I had MM recaulk them within the first week or so. I wonder if the vents are holding water behind them or deep in the caulk line? This may be an answer to why you're vents cracked? If mine ever crack I am going to investigate the use of carbon fiber fabrication for replacment. Like I said before I am anticipating them breaking as my raft up buddy has 37 SR AFT and there is just no other place to place the fender but beneath the stern cleats. Good luck, K

 

[Tail Chaser 661]

3 M 5200 is really for a permanent install.
3 M 4200 is good stuff.

If you have a West Marine catalog.
It tells you exactly which adhesives are designed for what applications.