3M 5200 as Adhesive

[philwsailz]

It is reasonable that you will want to remove it at some point based on materials and assumptions. It is cosmetic only, and not a structural part. It is inside the boat. The external window provides primary seal...

Assuming these statements- I would recommend spot-gluing it in place with a few dabs of 4000....

 

[centerline]

CL, are you claiming that epoxy won't bond to poly?

Absolutely NOT.... epoxy is great stuff and has its uses. it creates a tenacious bond.... but what i mean is, when using it to repair polyester, if there is ever a need at some later date, to do a repair over the epoxy, nothing will stick to the epoxy as well as the epoxy will adhere to something else...

polyester will bond very well with polyester, and at anytime later, you can bond more polyester to it just as securely.... but if an intermediate patch was ever done with epoxy, it doesnt like polyester trying to stick to it as well as it likes sticking to polyester. neither does it like more epoxy trying to stick to it....

it may seem like a solid bond, until it takes an impact and seperates cleanly from the surface of the epoxy....

there are things that can be done to help create a stronger bond when it has to be done, but when covering cured epoxy with more epoxy or poly, the bond between the two will never be as strong as poly over poly when using the same normal technique.

when there is an option to use polyester on polyester, its usually a better choice than using epoxy.

 

[Ajay73]

It is reasonable that you will want to remove it at some point based on materials and assumptions. It is cosmetic only, and not a structural part. It is inside the boat. The external window provides primary seal...

Assuming these statements- I would recommend spot-gluing it in place with a few dabs of 4000....

It's structural in that it won't be removed.

 

[FourPoints]

It's structural in that it won't be removed.

Structural in the context of Phil and I's comments means it needs to be strong to hold a load, and potentially dangerous if it fails. You are just attaching a cosmetic piece, Which for anything non structural, you should always assume it may need to be removed at a later date, and use a less permanent adhesive like 4000UV.

Also, being inside the portlight means it will always be getting sun through the portlight, and even though much of the UV will be blocked, a non UV stable adhesive will slowly degrade and yellow where visible.

 

[FourPoints]

Btw, 5200 is a sealing adhesive, meaning it first and foremost is adhesive, that has a side benefit of sealing. IIRC it has a bonding strength of 750psi, and can actually rip gelcoat off your boat before the 5200 fails. Consider 5200 to be nearly as permanent as the fiberglass you adhere it to.

It should normally only be used on things that you expect to last the entire life of the boat, like where the keel is attached, and where the deck joins to the hull, the kinds of things that hopefully will never fail for the life of the boat, or at least the next 20-30 years.

My point: attaching something like a cabin light or cosmetic trim ring with 5200 will only result in a future problem of removing for either yourself or another future owner. Any smart boat buyer that sees 5200 used liberally on the boat for things like this would be wise to walk away and buy another boat.

And with that, I'll end with Stu's favorite line, Your boat Your Choice.

 

[Maine Sail]

Absolutely NOT.... epoxy is great stuff and has its uses. it creates a tenacious bond.... but what i mean is, when using it to repair polyester, if there is ever a need at some later date, to do a repair over the epoxy, nothing will stick to the epoxy as well as the epoxy will adhere to something else...

While polyester over epoxy is a weaker bond many of the myths about it have been debunked such as "you can't gelcoat over epoxy"... I regularly bond G-10 to polyester using polyester resin. G-10 is poltruded epoxy / fiberglass sheet. With proper prep the boat would come part before the G-10 breaks free. That said I don't know many instances where you would need to bond polyester to epoxy.

polyester will bond very well with polyester, and at anytime later, you can bond more polyester to it just as securely....

This is not true. Polyester to polyester in a primary bond chemically cross links. Any work done after the cure is now a secondary / glue bond and is less strong. While still strong they are never as strong as the primary lay up, but does it need to be?

but if an intermediate patch was ever done with epoxy, it doesnt like polyester trying to stick to it as well as it likes sticking to polyester.

It not that it does not like it, it is just that polyester over epoxy is not as strong as epoxy over polyester. Still polyester over epoxy, properly prepped, can be very, very strong.

neither does it like more epoxy trying to stick to it....

The secondary bonding characteristics of epoxy to epoxy or epoxy to polyester or epoxy to vinylester are far stronger than polyester over already cured polyester. That said "do you need that strength" should be the real question. In most cases you do not need the strength of epoxy.

it may seem like a solid bond, until it takes an impact and seperates cleanly from the surface of the epoxy....

Never seen this and I've done a bunch of destructive testing messing around with polyester bonded to epoxy. Again properly prepped is the key..

there are things that can be done to help create a stronger bond when it has to be done, but when covering cured epoxy with more epoxy or poly, the bond between the two will never be as strong as poly over poly when using the same normal technique.

Epoxy to poly, even as a secondary "glue" bond, is stronger than the original layup and can create an obscene bond strength.. Broken a few sagged or "misaligned during cure" brackets or items off polyester hulls glued with epoxy and it takes the substrate with it.

]when there is an option to use polyester on polyester, its usually a better choice than using epoxy.

There is nothing wrong with polyester over polyester and most often, even in a secondary bond, the strength is far more than enough if well prepped. People often assume you need the strength of epoxy in a secondary bond but we have millions of polyester boats out there with millions and millions of secondary polyester bonds not falling apart....

If you need the ultimate in "secondary bond" strength then epoxy over polyester is technically stronger. I agree that I would prefer polyester over polyester to polyester over epoxy but still the bond between polyester over epoxy can be amazingly strong if done correctly.

This is a decent read on the subject of gelcoat/polyester over epoxy:

http://www.westsystem.com/ss/polyester-over-epoxy/

I have a customers race boat I work on built entirely of epoxy except for the gelcoat.. It has held up extremely well and has been severely punished in a highly demanding racing environment. It shows no worse for the wear than a polyester/gelcoat boat....

 

[Ajay73]

Fourpoints said "Also, being inside the portlight means it will always be getting sun through the portlight, and even though much of the UV will be blocked, a non UV stable adhesive will slowly degrade and yellow where visible."

But the glue I use will be between the inner liner and the frame. It will not receive sunlight.

 

[Ajay73]

Fourpoints said, "Structural in the context of Phil and I's comments means it needs to be strong to hold a load, and potentially dangerous if it fails. You are just attaching a cosmetic piece, Which for anything non structural, you should always assume it may need to be removed at a later date, and use a less permanent adhesive like 4000UV."

It's not just a cosmetic piece and it will not be removed. But it's not really structural either. Think of it like someone who is adding a storage (think glove box) compartment under the side deck, inside the cabin of course.

 

[Ajay73]

Btw, 5200 is a sealing adhesive, meaning it first and foremost is adhesive, that has a side benefit of sealing. IIRC it has a bonding strength of 750psi, and can actually rip gelcoat off your boat before the 5200 fails. Consider 5200 to be nearly as permanent as the fiberglass you adhere it to.

It should normally only be used on things that you expect to last the entire life of the boat, like where the keel is attached, and where the deck joins to the hull, the kinds of things that hopefully will never fail for the life of the boat, or at least the next 20-30 years.

My point: attaching something like a cabin light or cosmetic trim ring with 5200 will only result in a future problem of removing for either yourself or another future owner. Any smart boat buyer that sees 5200 used liberally on the boat for things like this would be wise to walk away and buy another boat.

And with that, I'll end with Stu's favorite line, Your boat Your Choice.

I know that 5200 is a strong adhesive, but the original question was that will a very thin glue line of 5200 work, much like you would get with two panels epoxied together with moderate clamping pressure. Or, as I've read in other forum posts that you really need to have a little thicker glue line for 5200 to work correctly, that is, you need a little more of it for it to work properly.

 

[FourPoints]

I know that 5200 is a strong adhesive, but the original question was that will a very thin glue line of 5200 work, much like you would get with two panels epoxied together with moderate clamping pressure. Or, as I've read in other forum posts that you really need to have a little thicker glue line for 5200 to work correctly, that is, you need a little more of it for it to work properly.

Too thin and it fails sooner since it cannot elongate as far, but as long as it is a solid layer, the bond itself is the same.

 

[centerline]

It's structural in that it won't be removed.

if its plywood and its around a window opening, the chances of it needing to be removed at some later date if fairly high.

if you are planning to glass it in completely to the hull material and use it as a structural stiffener for sealing the window against, then polyester is the best choice.... but if you are trying to use it as the sealer for the window, its a poor choice.

in your OP, it kind of led one to believe you were intending to use it as the sealing product around the window....

polyester is still the best choice, but epoxy can be used. but make sure you use a non blushing epoxy, (generally found labeled as the high dollar marine stuff). but if you dont grind it down to bare material and prep it properly, the epoxy wont hold either. never try to adhere it to existing paint.....

 

[centerline]

While polyester over epoxy is a weaker bond many of the myths about it have been debunked such as "you can't gelcoat over epoxy"... I regularly bond G-10 to polyester using polyester resin. G-10 is poltruded epoxy / fiberglass sheet. With proper prep the boat would come part before the G-10 breaks free. That said I don't know many instances where you would need to bond polyester to epoxy.

I agree with your additional comments to my post (except for one, and only because it seems I was taken out of context)
no matter what is written, there is almost always room for it to be written better or more fully explained

when using the right products and the right prep, an experienced craftsman like yourself can make informed choices and improvise the technique (and the prep) to make things work that would not otherwise be considered normally acceptable.... everything works together smoothly to insure a successful outcome to the project..

and to a lesser degree, a novice using the correct product and the proper prep should be able to make an acceptable repair, even if the experience and technique is lacking.... key words, correct product, proper prep....

the Problem I see is a lot of people dont yet have the knowledge needed to select the correct products for the job, dont take any care in the prep and are lacking in experience when using whatever discount product it is they decided on....

so I was trying to give a general overview of the benefit of using polyester rather than jumping straight to the more expensive epoxy....

as you have already said, the bond between epoxy to polyester, or polyester to epoxy, or poly to poly or epoxy to epoxy, will almost always be stronger than the task calls for,
but when someone does not understand the difference between a blushing epoxy and a non blushing epoxy, or the properties of the different types of resins, or whether a resin would be better than a flexible sealant, there are some general guidelines that should be considered.
and that is what I was trying to offer any of the readers that may not be quite as experienced who are thinking about tackling a resin project.

and when using a blushing resin, if the blush isnt removed when applying additional coats, the additional coats wont really be adhered like they seem like they are.... ive seen it peel off like it was being released from the mold after taking an impact... it wouldn't of happened if the guy would of had some basic knowledge of what he was working with....

working with resin can be an easy and fun project if the proper prep is done, which usually involves 3-4 times as much work as the actual job.
and because of the amount of prep involved, people usually scrimp on it and that is where the job starts to fail without ever being noticed until its too late. ....do it right the first time and you will only have to do it once!

 

[Ajay73]

Too thin and it fails sooner since it cannot elongate as far, but as long as it is a solid layer, the bond itself is the same.

I don't really think I need the elongation aspect. If i used epoxy there would be almost no elongation. I expect it would flex just like an epoxy bond. so thin glue line should be OK?

 

[Ajay73]

Would like to use the epoxy since I worked with it almost hundreds of times before. I'm inexperienced with polyester except for making a seacock backing plate out of 1708 and vinyl ester resin. If I used polyester I would have to make a peanut butter out of resin and glass cuttings and other filler. I just don't yet have the confidence with polyesters to make an attempt. I would probably just end up with a big mess. I have some recoring I have to do and I will be using the poly for that but I will be doing some practice layups before starting the actual work.