New Cover - Add Extra Polyethelene?

[jackmorgan]

I just received a new spa cover from alpine spa covers and was wondering if it would be in my best interests to add some extra polyethelene vapor barrier around the foam cores? (I happen to have a roll of 6 mil poly lying around from a renovation). I was thinking of using tuck tape to seal it. I realize the tape will fail eventually, but in my mind it makes sense that it will extend the life of the cover. Any comments?

Thanks.

[Roger]

I just received a new spa cover from alpine spa covers and was wondering if it would be in my best interests to add some extra polyethelene vapor barrier around the foam cores? (I happen to have a roll of 6 mil poly lying around from a renovation). I was thinking of using tuck tape to seal it. I realize the tape will fail eventually, but in my mind it makes sense that it will extend the life of the cover. Any comments?

Thanks.

Your going to take the cores out and wrap them? A quality cover will have them allready wrapped. And getting them removed, wrapped and replaced will not be an easy task. In my experience the trouble and time to take out and install cores is a very difficult thing and a cover will only last for 3-4 maybe 5 years regardless. I don't know, maybe it will extend the life but all I can say is good luck. They are a tight fit.

[n1oty]

I just received a new spa cover from alpine spa covers and was wondering if it would be in my best interests to add some extra polyethelene vapor barrier around the foam cores? (I happen to have a roll of 6 mil poly lying around from a renovation). I was thinking of using tuck tape to seal it. I realize the tape will fail eventually, but in my mind it makes sense that it will extend the life of the cover. Any comments?

Thanks.

Your going to take the cores out and wrap them? A quality cover will have them allready wrapped. And getting them removed, wrapped and replaced will not be an easy task. In my experience the trouble and time to take out and install cores is a very difficult thing and a cover will only last for 3-4 maybe 5 years regardless. I don't know, maybe it will extend the life but all I can say is good luck. They are a tight fit.

And to add to Roger's comment, do you have the ability to PROPERLY seal this new vapor barrier? If not, the whole exercise is utterly futile. I'll defer to any comments Doc may care to make, since his company makes covers, but my understanding is that sealing of the seams is absolutely critical, and is either heat sealed or laser sealed to ensure no leakage.

John

[jackmorgan]

actually I wasn't pleased with my purchase and the company is sending me out an upgraded cover. They asked that i remove the cores and ship back the old cover when i receive the new one. They came out quite easily and now the cores are just sitting in the garage waiting for the new cover to be shipped. Would tuck tape not work at all? They use it as a permanent vapor barrier sealing tape in homes. It's supposed to last for a long time.

[reeffreak]

One of my hot tub dream projects is to do an epoxy layup on my foam cores using cloth, finishing resin, and vacuum bag the whole thing while it cures. This is a technique used in modeling and full scale composite structures in aviation. The cores will last for a long time, and won't ever take on moisture. Adds almost no weight but will make the cores much more rigid. This is how some composite airplane wings are made.

[jackmorgan]

One of my hot tub dream projects is to do an epoxy layup on my foam cores using cloth, finishing resin, and vacuum bag the whole thing while it cures. This is a technique used in modeling and full scale composite structures in aviation. The cores will last for a long time, and won't ever take on moisture. Adds almost no weight but will make the cores much more rigid. This is how some composite airplane wings are made.

I was actually thinking about doing something along these lines as well - basically just fiberglassing the foam cores and adding a stainless steel piano style hinge. Not sure why this isn't an option - I guess since all spas have different shapes the costs would be extremely high. However, for a company such as aruba that has sold 10's of thousands of tubs through costco - all with the same dimensions needed for the cover - it may be viable.

[jackmorgan]

I ended up wrapping the foam cores in 6 mil vapor barrier while they were out. I sealed all the seams with tuck tape. It took me around 1.5 hours to get the cores out, wrap them and put the cores back in. If you try to do this make sure you don't have any wrinkles, etc showing (on the top anyway) or it will show through the vinyl cover. Time will tell if it makes any difference to the life of the cover.

[Dr. Spa]

Fiberglass resin will melt (dissolve) the foam.

You're tape will probably begin to fail (lose it's stickiness) in about a year.

Sorry for the bad news

[hot_water]

Fiberglass resin will melt (dissolve) the foam.

You're tape will probably begin to fail (lose it's stickiness) in about a year.

Sorry for the bad news

The guys are talking about epoxy as the resin. Polyester will melt the foam, but epoxy won't.

The real problems are:

#1 - If you vacuum bag the layup, you're gonna collapse the foam!

#2 - Epoxy is actually not waterproof. Actual material testing and real composite failures both show that MOST epoxy resins both absorb and pass water vapor quite readily. If you look at composite structures such as antenna dishes used on aircraft (in the nosecone) and military ships, these are typically high-quality epoxy-glass layups over various types of honeycomb cores (foam isn't used in very high quality layups), and are pre-preg layups that are controlled resin content, vacuum bagged, and autoclaved under highly controlled conditions. And these ALL have finite (and pretty short) lifespans, as moisture gets in, freezes and delaminates the structure. For a VERY long time, composites weren't used for primary aircraft structure for these (and other) reasons. THe carbon fiber/resins/methods used to beat the problems (finally) are typically not something you can do at home.

#3 - One of the most effective ways to address moisture with composites is to make the layup thick. But the density of a typical epoxy glass layup is around 60-70% that of aluminum. When you make it thick enough to work.... well, you can figure it out. It gets heavy, fast.

Rutan style homebuilt airplanes use foam cores with epoxy glass. Kind of a different thing, though.... I think you're gonna have a lot of problems with this type of construction in the saturated humidity environment of a spa cover.

Here's an idea though. You have to test this... but polyurethane sealants (NOT silicone) such as P&L door and window sealant MIGHT stick acceptably well to 6 mil polyethylene and will provide a water an water vapor seal. If that stuff isn't good enough, I would next try a product caled "Kerdifix" which is made by Schluter in Europe. It's a silane modified polyurethane - probably the best product of it's type I've ever used, but it costs $25 for a tube. Finally, there's one of the sealants used to hold the windshield onto your car. There are room-temp cure and very, very good materials.

Or you could be lazy like me and just plan on getting a new cover every 4 or 5 years.