Friday, September 4, 2015

Turning Turtle

I came up with a design for the finished top and made some plans for how to get there.  But, as they say, the devil is in the details.  I've spent a lot of time at just about every step of the process thus far figuring out some detail related to the build. How do I create the desired arch, how do I calculate and lay up the complex angle that makes up the mounting flange at the arch, and even how to apply 9 to 12 foot long swaths of glass fabric (particularly when you can't really reach the middle of a large surface).

The last couple days haven't been any different.  With the main layers of fiberglass applied to the top of the top, it was time to flip the thing over so we could start applying the glass to the underside of the foam.  Now it sounds like a relatively simple task to flip the thing over, but there are some catches.  Once the foam core of the top has fiberglass on both sides, it becomes rigid and can support weight.  With the fiberglass on only a single side, the expectation is that it is still rather flexible.  And if it flexes too much, I could imagine that the bond between the foam and the fiberglass skin could be weakened (I don't know if this is true, but it seems like a possibility). When the top is upside down, I expect that it will not retain the curve without assistance too.

Then there is the frame to which the foam was attached.  It held the foam at the desired curve (mostly) with a number of loops of 30 pound test fishing line. While this was sufficient for holding the foam above the frame, what would happen if we flip it over?  Would the lines pull through the foam? Can we keep the frame attached or will we have to remove it before turning it over? And will we be able to control this huge piece of plastic and foam as we flip it end-over-end?

Oh, and did I mention the canopy top?  It is a 10 foot square (measured at the feet, so the top is actually only about 9.5 foot square), and the bimini top is 9.25 foot by 12 foot at its widest points.  Can we maneuver the top out from under the canopy or will I have to disassemble all of the tarps and move the canopy first?  All of these problems to work through on the flip are similar to what I've had to figure out at every step of the process.

We thought about it for a while and came up with a plan that seemed like it would work. We recruited a few friends at the marina (6 of us total) to help with the task.  Naturally, as we were getting ready to flip it over, storms started brewing on the horizon.  As the fiberglass is still rather raw and water soaking into the foam would not be a great idea, we had to button everything back up and wait for it to blow over.  After the rain, I was able to get everyone back together and we were ready to go.

The process was that we would first move the top and frame off of the boat stands that had been holding it up, maneuver it out the side of the canopy, and carefully set it aside.  Then we would place the tabletop I originally built back on the boat stands so we would again have a table.  Using a bedspread we bought at a local thrift store, we added a bit of padding to the tabletop and then covered it with plastic so no drips will glue it to the top. We would pick the top and frame back up, carefully set it on the rear edge (where the fiberglass wrapped around the foam) and then continue flipping it over supporting the top with the frame just sitting on top.  The next step would be maneuvering the upside down top back under the canopy and carefully setting it on the table.  We would then use the scrap curved pieces of plywood, padded with pipe insulation foam, to cradle the top on the table and help maintain the curve.

Surprisingly, the move went about like we planned.  At first we didn't get the boat stands supporting the tabletop well positioned, and the tabletop started to pull apart after we set the top down.  We quickly went around and lifted the top and table to reposition the stands.  After slipping the padded cradle wedges into place, the top has successfully become a turtle laying on its back. Our friends Stewart and Julia brought a bottle of champagne to celebrate the event, and then we adjourned to our boat for some drinks, snacks, and conversation to complete the evening.

Working on the support cradle.

The next morning I went out to adjust the position of the top on the table and tweak the position of the cradle wedges before attaching them to the table.  We also cut up some foam pool noodles to help add support and distribute weight.

One of the things I haven't really mentioned yet is an issue we discovered while doing the layup on the top side.  Polyester resin shrinks when it dries.  As a result (we think anyway), we noticed that the side edges of the top pulled away from the frame a bit, stretching the fishing line as it did.  The movement was about 3/4 of an inch.  Since I assume applying fiberglass to the other side of the top will result in it curling back the other way, I set up the cradle wedges so the ends of the top were held about the same distance from the end of the frame.  My hope is this will allow for any shrinkage of the fiberglass laid on the bottom of the foam...and if the bottom doesn't shrink that much it is OK as the only place the curve is critical is at the arch, and the laid up tab at that position seems to be holding the curve well.

Removing the mold/frame.

Up to this point the frame was still mostly attached to the top in order to make sure we got the cradle positioned well.  But it was time for that to change.  Using some wire cutters, I carefully clipped all the fishing line flush with the foam.  We then tried removing the frame.  Unfortunately, but not surprisingly, the frame was stuck along the back edge.  When I made the frame, I intentionally didn't glue the back piece to the rest of the frame, it was only held with screws.  I removed the screws so we could remove the rest of the frame...but it still wouldn't budge.

Don't let anyone tell you that polyester resin doesn't make a good glue.  The resin that dripped through the holes we punched in the foam managed to glue the back lip of the mold to the rest of the frame despite my best efforts to not do that.  In the end I had to cut the supports to move the rest of the frame.  Using flexible putty knifes we were able to work the last piece of the mold free.

Almost ready to glass.

Now with the top free of the mold, it is time to clean up (sand down) any remaining drips and bumps, clean the PVA off the back of the mounting flange so the next layers of fiberglass will stick, and then we will be ready to apply more fiberglass.


  1. Hi Mike,
    "Turning Turtle" not exactly the 2 words any catamaran owner wants to hear, but in this case- Congrats....
    Doug in VT

    1. Hey Doug,
      Hopefully the only time I will have to use the term in reference to anything regarding my boat. Once installed, I hope the top will remain right-side up. :)