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3M 5200 question


wagonmaker

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Good evening to all........Progress goes a bit slow on my mini skipjack. I have most of the major pieces cut and loosely joined so I could make my dagger board/mast box fit into the space between the hull & topside. This is my second attempt on the dagger board box...........the first attempt I simply made to exact dimensions as called for on the plans and it didn't fit. I won't do that again. Anyway...............the question??

While reading Sam Devlin's book he suggested laminating formica to the insides of the box for waterproofing. I didn't have any formica but had alot of aluminum trim coil. The type used to cover exterior trim boards on homes, door & window casings as well as fascia. Since I have done tons of this stuff for Sears & had a brake & lots of the coil stock, I laminated all the interior surfaces with the aluminum & it seems to work great, it is about the same thickness as roof flashing & very malleable.

The plans call for siliconing the interior joins, however I don't feel comfortable with silicone here, especially since it won't be a serviceable area once it is closed up & installed. I tried a test piece using marine tex epoxy had left over from a fiberglass boat repair a while back & it works good. I don't think I have enough marine tex for the complete job & at $30 for 12 ounces not sure I'll buy more anytime soon. I also have not purchased any epoxy for my exterior glassing. Is the 3m 5200 suitable for sealing the interior joins of the dagger board box?

Once again guys , thanks for your help. By the way I ordered a digital camera a couple days ago, maybe i can post a pic or two soon......Wayne

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5200 is a very good adhesive and should work quite well for that app. I patched an inflatable using 5200 to stick the patch on, back in 1982 or 83. Still have the boat and the patch is still holding fine.

I HATE silicone on anything to do with boats. Sometimes you just have to use it, but otherwise I don't want it anywhere on my boat. And if I can find ANY alternative I don't use it.

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I think Charlie's right on this one. 3M 5200 is probably good for that application, as it STICKS and works pretty well where it gets wet. I had used it for several things on my Weekender, and it is still holding up on it (even though it sits, sadly, in my brother's side yard).

There are some very good adhesive silicones, like RTV, but silicone can leave a residue that makes it hard to paint ... and for some reason, I can get that residue a foot or more away from what I'm using the RTV on. So for boat use, I tend to go toward the 5200.

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I HATE silicone on anything to do with boats.

Amen!!! The stuff should be illegal. There is little I hate more than having to repair or replace something bedded in that stuff.

5200 or 52-goo as we call it at the boatyard is great if you never want to take it apart. All too many people want to use it as a bedding compound. It does bed well but removal of the bedded piece often causes damage and when mechanical fastening is being used the adhesive properties are unecessary. Sounds like you have a good application for it though.

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3M 2500 is good stuff and I use it frequently, but it has limitations. It's not nearly as flexible as most other sealant/adhesives. It dries to a hard rubber like material, which can't be expected to deform more then 20% of it's bead width, before it rips. It's incredible grip on most things can cause difficulties come repair or maintenance time. When used as a seam compound, on wooden joints that will become water soaked, it will pull off like a thick rubber string with surprising ease. Trailer boats have little issue with this. I've seen 2 and a half ton fin keels held on, with only a 1/4" bead of the stuff providing the stick-um. I've also seen large chunks of boat removed when a piece of hardware, bedded in 5200, is pried from it's grip.

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I have some access ports to be installed, and the manufacturer says to use nothing but silicone to bed them. What alternatives are there? Boatlife polysulfide? Maybe 3M 4200?

Seems to me that some of these will eat through or destroy some plastics (like Lexan). Apparently, silicone does not, which is why they say to use it.

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My favorite bedding is Sikaflex, and it harms nothing. But it only comes in cartridges and doesn't keep well for long after opened. It has a fairly long working period in which it cleans easily

Boatlife's Lifecaulk works very well and comes in small toothpaste like containers. These tubes last quite a long time when recapped. The working time isn't as long, especially when warm. It turns to a cottage cheese like consistency after a while and becomes a nuisance to clean up, but it does still clean.

Both clean easily with mineral spirits within their windows.

I assume these access ports are plastic? The manufacturer probably wants to make sure you don't use any harse solvent based materials which may eat into or at least etch the plastic. Neither Sikaflex nor Lifecaulk will attack plastics and mineral spirits doesn't either.

4200 isn't quite as tenacious as 5200, but still more adhesive than you probably need.

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I didn't have any formica but had alot of aluminum trim coil. The type used to cover exterior trim boards on homes, door & window casings as well as fascia. Since I have done tons of this stuff for Sears & had a brake & lots of the coil stock, I laminated all the interior surfaces with the aluminum & it seems to work great,

I would be hesitant to use aluminum if you plan on putting it into salt water. The aluminum will be destroyed in short order.

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Polysulfide based sealants are not compatible with acrylics (plexi, ABS, Lexan, etc.) it will attack the plastic. Ditto with polyurethane based goos. This is one place that silicone has to be used, but is doesn't have to be just silicone, which has limited tack and strength, some polyether based products (silicone will be listed on the contents label) will work, but I only know that 3M 4000UV is plastic safe. West Marine Silicone Sealant and 3M Silicone Sealant are plastic safe. Sikaflex 291 and 291 Fast Cure are not recommended for these types of plastics.

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The manufacturers of polycarbonates still do recommend silicone. They do so because they know it doesn't attack their material and they want to cover their liabilities. They also don't have to warantee whether the installation leaks or not. I have been using Sikaflex 291 for the past 4 years on countless fixed port bedding jobs using polycarbonate and have yet to etch the material in the slightest, inspite of smearing it all over the viewable portion of the port during the cleaning process.

I am not advertising for Sika. Everyone should use their own best judgment in choosing materials. But keep in mind that manufacturers may be more interested in their liabilities than researching new products.

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