Question re spray polyurethane foam

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  #1  
Old 03-25-15, 08:09 AM
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Question re spray polyurethane foam

Not sure where to put this question. I need to perform a somewhat unique modification to my landscape lights, and it seems that spray foam would be the best product for the job.

I purchased a bunch of Malibu bollard ligts, which get good reviews except that they have one big design flaw: the bottoms of the bollards are wide open. This allows soil, moisture, and insects to work their way into the bottom of the fixture, which tends to corrode and damage the light socket. It doesn't take much because the light socket is set only about an inch above the bottom of the bollard.

The bottom piece of the bollard, which holds the light socket, screws off. Here's the best picture of it I can find online. The spike in this picture is also removeable. What you're left with is a hollow metal ring with a thin metal "cross" inside holding the light socket but otherwise empty.

[ATTACH=CONFIG]48483[/ATTACH]

Some reviews I've found recommend spray foam to seal up the bottom. Seems pretty easy to do because the bottom screws off and is easily accessible, but the foam is messy and expands everywhere. It will expand right up through the top of the ring and cover the light socket, requiring messy trimming. What I'd like to do is cap the top side of the ring prior to application and then spray the foam from the bottom so I get a more even finish on the top. I could cap the top simply by turning it upside down and pressing it into a layer of play-dough or even a piece of cardboard - but is there something I can spray on the cap to prevent the foam from sticking to it?
 
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Old 03-25-15, 08:20 AM
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Use DAPTex Plus foam from the paint department. It doesn't expand as much and cleans up with warm water before it cures.

I really can't offer much more, because I don't understand anything of your description about the fixture itself. Not your fault, I just never messed with those lights.
 
  #3  
Old 03-25-15, 11:16 AM
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I'll try to take and post my own picture, but if you look at the picture posted below, imaging rotating that 90 degrees so you're looking straight into the bottom of the fixture. You'd see right out the other side because that ring is hollow. So when you push that spike down into the ground, the dirt, moisture and bugs can come right up the bottom of the fixture into contact with the light socket (which you can see in the picture is set in the middle of the ring).

So, some people spray foam to fill in the ring, but the foam obviosuly expands out both sides of the ring and makes a mess, not to mention potentially clogging the light socket.

I want to cap off the top of ring and light socket before I spray. I'm thinking I'll try taking some playdough and rolling it into a thin smooth sheet. Then I'll put a piece of saran wrap on top of the playdough. Then I'll take one of the rings and push it down, upside down, into the playdough, which should cap off the top of the ring and the light socket. Then spray the foam into the bottom of the ring (facing up because I turned it upside down), let it set up for a few minutes, and trim the bottom with a razor. We'll see how that works.

I'm reading that PU foam doesn't stick - at least very much - to plastic sheets like saran wrap.
 
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Old 03-25-15, 11:37 AM
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Ok, that's clearer now. There must be bars or something connecting the outer ring to the inner area?

I wouldn't use the poly stuff...period. It's a complete mess and expands far too much...even the low expansion kind. It sticks to everything and has to be cleaned off with acetone which wouldn't do the housings any good. If you have to use foam, get the DAPTex Plus (smaller blue can in the paint area).

In fact I probably wouldn't use foam at all I imagine. They make a clay like substance that you can buy in sticks or bars called duct seal compound. You'll find it in the electric aisle (NOT ventilation duct seal which would be in plumbing/HVAC). You can just press it down into the area you need covered, then trim what sticks out the bottom. It will adhere, but will stay semi-pliable. Only about $2.50 for a 1 lb block.
 
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Old 03-25-15, 02:13 PM
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Correct - there are two little metal pieces that form a cross to hold the light socket in the middle of the ring.

I'll look into the duct seal compound - that sounds like it would be way easier and cleaner to apply. Thanks.

Another idea I had was to just take a small square of seran wrap and stretch it over the bottom of the ring. The spike is threaded and might screw right through the seran wrap. Then I'd just take the edges of the seran wrap up around the sides of the ring and secure with a rubber band. That portion will be hidden below the mulch, but the rubber band would freeze and break down over time. Still something else I could try. I'll look for the duct seal compound.
 
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Old 03-25-15, 03:13 PM
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The ductseal is the proper product to use. Bugs can easily eat through spray foam.
 
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Old 03-25-15, 07:05 PM
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Ok, looks duct seal compound it is. All the stores seems to carry it. I've been reading about it online and it is described as "duct tape in bar form" and "play dough for adults." Sounds like just the ticket, as long as it adheres well enough to the painted aluminum these bollards are made of.

Also, I forgot about the connector wires, which you can see stick out the bottom of the ring. I guess I'll just have to mold the duct seal over these wires and hope for the best.
 
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Old 03-25-15, 09:08 PM
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I guess I'll just have to mold the duct seal over these wires and hope for the best.
And that is exactly what duct seal is made for.
 
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