Repairing the Maxxus Tri-Fold Cover

We have a Maxxus hot tub, with a tri-fold insulating cover. We've had it about four years. The cover opens like this:
How the cover opens
We have a cover lift for it, which assists in opening the cover, but only assists in going from step 2 to step 3. However, a few months ago, the middle part of the cover became waterlogged, so that going from step 1 to step 2 began to require quite a bit of strength. My wife, who is quite a bit shorter than I am, and therefore has less leverage, was no longer able to open the cover by herself.

We went to the store from which we bought the hot tub, and priced the cost of replacing the cover. The quote we got (including installation) was in the neighborhood of $700.

The three parts of the lid are zippered compartments (made of something like vinyl), with an insert in each section. I decided to remove the insert and make one of my own.

Important disclaimer:

This page described what I did. I do not advocate that anyone else do it, because the cover can no longer support much weight. This makes the hot tub substantially less safe. In particular, children and intoxicated people should be kept away from a hot tub with this modification.

If you do anything similiar with your own hot tub, you do so at your own risk.

Making the insert

The middle section of the lid is approximately 45 inches by 90 inches by 3 inches. Fortunately, styrofoam insulation can be bought in a slightly larger size than this. So my first step was to gather materials.

Styrofoam Styrofoam.

Four 2 foot by 8 foot pieces, each 1-1/2 inches thick. These were about $11 each, from Home Depot. They are designed to be fitted together, long edge to long edge.

I figured I would need to glue the styrofoam together, wrap it in plastic, and tape the plastic.

For glue, I decided on Liquid Nails; the kind that is designed for foam, not the kind that dissolves foam. This kind says "Wood and Foam Molding Adhesive" on it.

In retrospect, this was not a good choice of adhesive. More on that later.

The next step (below) was to open the zipper on the middle compartment and pull out the insert.
Initial materials
Ready to open center section Showing the zipper
Removing the old insert Pulling out the old insert was every bit as difficult as I thought it would be. It was in there very tight! The replacement had better be a bit smaller, or I'll never get it in.

What do you suppose those gray rectangles are? They correspond to gray patches  on the vinyl covering. Your guess is as good as mine.

This thing weighed 46-1/2 pounds!

I was afraid of making the insert too big, or I wouldn't be able to put it in; or too small, or the lid would be floppy and not fit well. The original insert turned out to be 42-1/2 inches by 90 inches by 3 inches. I decided to make my insert 42-1/4 inches by 89-1/2 inches. (Since two styrofoam slabs add up to 3 inches, I didn't have an choice there.)
Of course, I had to put the cover back on the tub while I made the new insert. It was a bit saggy. Saggy lid
Now to smear some glue on the long edges of the styrofoam and glue two pieces together that way. Then do the same with the other two pieces.

Obviously, this is going to be a very weak join.
Glue on edges
Glueing edge to edgeHere are the four panels, being glued two-by-two. You're supposed to clamp pieces together while the glue sets. So how do you clamp styrofoam, anyway? I settled for puting a few books on top.
The pieces of styrofoam had to be cut to size. I did some of the cutting beforehand, but I left the last cuts until later, because I wasn't sure that I could line up the pieces perfectly.

Here's the best way to cut styrofoam:
Cutting with a knife
I used up one tube of Liquid Nails, then went to a closer hardware store to buy another. However, they didn't have the right kind, and the guy there recommended that I get Gorilla Glue instead. Good advice!

A word about Gorilla Glue: It's expensive ($13 a jar), and they recommend you wear latex gloves when you use it. Also, you put glue on one side and wet the other. How weird is that?
Gorilla glue kit
"Clamping" with toolboxesNow to glue all four pieces of styrofoam together (they are already glued in pairs, edge to edge). I didn't pick up one of the two pairs carefully enough, and it bent along the seam, showing that the Liquid Nails had not really set well.

After putting a whole bottle of Gorilla Glue on two pieces of styrofoam, I wet the other two pieces and put them on top, "clamping" them together with toolboxes. I also glued some carpet strips on them; one on one side, two on the other.
After this glueing, I finished the cutting.

Cut to sizeAt one point I tried a jigsaw on the styrofoam. It cut nice and easily. The bad news is that the cut edge was much rougher than I could do with a knife. The worse news is--styrofoam dust! Highly static, clings to everything, styrofoam dust. (You can see some on the carpet there.)
I had a twelve-foot piece of this carpet stripping (which I bent into thirds in order to put it in my car to bring home). This gave me three decent-size strips, plus a few small pieces which I thought I might as well use to help stiffen the joins between the long pieces a little bit.
Glued strips
Tape on metal endsI didn't trust the sharp ends of the metal not to damage the plastic I planned to wrap this thing in, so I put plastic tape over all the ends. Plastic tape is great stuff, and very water-resistant. Unfortunately, the 1-1/2 wide tape I use can only be found in older hardware stores.
Next, I glued some stair edging on the bottom side edges. This is the part that's going to be right against the hot tub, and was the best way I could figure to increase the strength of the assembly.

You can see how much the Gorilla Glue foams up. I had to cut off chunks of it.Stair edging
So, how do you "clamp" stair edging onto styrofoam?  With string and bungee cords!

Bungee cords
Unfortunately, strings will cut right through styrofoam, so on the edges where I didn't have stair edging, I had to put some cardboard protectors.

Cardboard protectors
Somewhere along the line I bought some Gorilla Tape (also expensive). I have no idea how waterproof this tape is, but it's pretty strong stuff, and has a strong adhesive. It occurred to me that it might help hold the metal strips to the styrofoam (since they are essential to whatever strength the whole thing has), and even if the tape came off, it wouldn't hurt anything.
Gorilla tape on everything
Now to cover the whole thing in plastic and tape it up with plastic tape. I have no illusions about actually making it watertight, but I had to do my best.
Sealed and ready
Now for the moment of truth.

Actually, as I expected all along, now for the hour of truth.
Going in

Sorry for the picture quality--my flash didn't go off, and I didn't realize it. But what you are supposed to be seeing is the insert completely in, but with the zipper refusing to turn the corner. I had visions of taking it out, taking off the plastic, and shaving off another quarter inch!

Fortunately, it didn't come to that. Twenty minutes with assorted pliers and other tools, plus some blue air, did the job.
Stuck zipper

Did I mention that I think plastic tape is great stuff?

I hate to think what would happen if anyone tried to climb on this, so you better believe I'm going to be careful about who I let get near it.

And that's it.

The whole project took me a weekend and part of a Monday--much of which was spent waiting for various glues to dry. The project cost about $70 or $80.

Remember I said that the old insert weighed 46-1/2 pounds? My new one weighs--wait for it--fifteen pounds! I don't know how long it will last, but it's been a week, and so far it hasn't broken, so there's hope. And my wife can open the hot tub again.