3M 5200 doesn't always play well with others

[bsangs]

Needed to build a "platform" for the high water alarm float switch in my bilge, as the previous owner just had it hanging out on top of the centrifugal bilge pump, not even affixed to anything, which rendered it pretty useless. Bought a small sheet of HDPE (StarBoard), cut a few 2" x 5" strips to layer together, which I was then going to stick to the bilge floor, and affix the high water switch on top of the platform, so it would be higher than the pump float switch. I planned to use the mother of all adhesives - 3M 5200 - to stick everything together.

At this point, I'm guessing all you expert repairers and restorers know how that went. For those boat maintenance newbies like me, here's the takeaway - 5200 doesn't work with HDPE. I scuffed the HDPE board a lot, but still, the 5200 didn't want to stick. Not even a little. My fault for not checking beforehand, but I just assumed it would. Come to find out HDPE and 5200 are apparently mortal enemies.

So, back to the drawing board, I bought a roll of 3M VHB tape which was said to work with HDPE. Happy to report it does. Built the platform with layers of the tape, stuck it to the bilge floor, taped the float switch to the platform, and now have a (hopefully) reliable high water alarm. We keep calling it our "learning boat" for a reason.

 

[Prairie Schooner]

My understanding is that basically there aren't any glues that work with polyethylene. I thought the only choice was welding, either chemically or with heat. Which means only PE to PE. Interesting there's a tape billed as workable. I'll be interested in hearing how it holds up.

 

[bsangs]

My understanding is that basically there aren't any glues that work with polyethylene. I thought the only choice was welding, either chemically or with heat. Which means only PE to PE. Interesting there's a tape billed as workable. I'll be interested in hearing how it holds up.

My understanding was, well, none whatsoever. But I get it now. So far so good on the tape, but it's only been a few days. Decided to give it a shot, as a bunch of others reported using it successfully. If it doesn't hold I'll be breaking out the screws which will, ironically, be dipped in 5200 before being fastened. (And in all fairness to 5200, there are a handful of people out there they said they've been able to fuse the two together, but lots of scoring, heat and other things were used to make it so.)

 

[Prairie Schooner]

My understanding was, well, none whatsoever. But I get it now. So far so good on the tape, but it's only been a few days. Decided to give it a shot, as a bunch of others reported using it successfully. If it doesn't hold I'll be breaking out the screws which will, ironically, be dipped in 5200 before being fastened. (And in all fairness to 5200, there are a handful of people out there they said they've been able to fuse the two together, but lots of scoring, heat and other things were used to make it so.)

It's all Ericson University here and I'm just in the beginning of my sophomore year. 5200 is so powerful, I can see where the scoring would give it something to grab onto. StarBoard is great stuff. I use it where there will be a mechanical connection, but wouldn't rely on adhesive for anything mission critical. Your application isn't structural so it's a perfect place to experiment. Keep us posted, Brian.

 

[markvone]

I much prefer to use G10 F4 fiberglass sheet in lieu of Starboard HDPE or wood in the bilge because you can bond it to itself or the boat with epoxy. It's strong enough to use 1/4 inch thick sheet, maybe even 1/8 inch. Can be bought in 12" x 12" sheets (or larger) on Ebay. I also use it for backing plates for thru-hulls and deck hardware. Easy to cut with a tile wet saw.

See my emergency bilge pump stand in post #33 of this thread:

Bilge maintenance questions

Knowing what you know now, I think that simply removing that check valve might fix your problem. There is no danger of flooding your boat because the exit through-hull is well above waterline. You will, however get the in-rush of the full volume of water that the check valve was holding...

ericsonyachts.org

I built this with 3/4 inch thick verticals so I had more room for threaded inserts. Top (pump base mount) is 1/2 inch thick, it could have been 1/8 inch, it screws to the two verticals so it is removable. Verticals are epoxied to the bilge floor with West thickened G/flex epoxy.

Mark