Three Steps Forward, Two Steps Back

The title pretty much describes the feel of the work we have been doing the last few days.  It finally stopped raining and blowing, and we can deal with one or the other right now, but not both.  Wind by itself isn't much of an issue other than it can cause the top to wiggle just a bit.  Rain, of course, isn't good when you want to drill holes in a cored fiberglass panel (getting the core material wet can cause delamination and is very detrimental to the strength of the structure). We could put up a tarp to protect from the rain, but only if the wind isn't bad.

I just can't get away from those tarps.

Anyway, the weather was cooperating so it was time to get these supports installed.  The first step was to get them positioned correctly.  A task that is not as easy as it may sound.  The new top has a curve to it, and the cabin roof has a curve and a slope.  There are lots of angles to take into account, and getting the supports lined up properly is a bit of a task.  Oh, and don't forget nothing is attached so you have to hold the angled support (that won't stand on its own) while you attempt to mark drill holes...all while standing on a platform that is moving (boats are rarely ever completely still while in the water).

We put masking tape down in the general areas where the supports will be mounted and line them up as best we can.  While I try to hold the support still, my wife would hop off the boat and verify the alignment. Once the OK was given, I try drawing a line around the base and then mark the mount holes with one hand while I try holding the support motionless with the other.  We repeat this task until we have the mounting locations on the cabin roof marked.

Oh, I almost forgot...before we started, we had to disassemble the headliner in the salon.  The headliner consists of interlocking panels and a piece of fiberglass trim that needs to be removed so we can access the, soon to be, mounting holes.  The panels are oriented such that we have to remove the liner for the whole salon and galley area.  Now we have a bunch of big panels to trip over on the boat while we work on this project.

Bare salon roof, guess we'll clean that while the panels are down.

Drilling holes in the perfectly good structure of a boat always seems to make me a bit nervous. To make the task more interesting, we don't just drill holes and mount hardware in a cored deck, but drill the holes oversize, fill them with epoxy, and then drill smaller holes.  This encapsulates the core material and prevents any future leak from getting to the core.  It also provides some structure to allow bolts to be tightened without crushing the core material. (Core materials are typically designed to deal with shear stress but are not as good with localized compression stress.)

Drill with drill guide.

We drill the holes using a drill guide to help keep the hole straight.  This is important because the smaller holes drilled later will need to be centered in the larger holes.  I didn't oversize the holes a great deal, but instead elected to try a process that was described at Compass Marine. I drilled holes just large enough that I could insert a rotary tool cutting bit.  I then used the rotary tool to remove excess core material underneath the fiberglass skins.  The result is a hole with an enlarged cavity in the middle that will contain the epoxy sleeve and be trapped between the fiberglass.

Rotary tool with the cutting bit.

Then we take the two steps back and fill the hole we just drilled with epoxy.  I'm using epoxy for this as it has a bit better mechanical and adhesive properties than polyester resin.  We thicken the epoxy with the same fumed silica that was used to thicken the polyester.  I used duct tape to seal the holes at the bottom and a syringe to inject the resin.  Toothpicks were used to aid in getting the resin to sink to the bottom of the holes and allow any trapped air to escape (simply inserting them in the hole and then pulling them back out several times seems to have done the trick). All that work and the end result is resin colored dots in my cabin roof.

The epoxy "sleeve" that seals off the core material.

The next day we re-drill the holes using the same guide and a smaller bit.  I'm glad to report that the new holes were well centered in the old holes, all the way through the inch thick deck.  We mount the center support in the new holes and then mark the mounting location on the top. Then we remove the support and drill the holes in the top.  After the holes are drilled, we re-install the center support to help stabilize the top and then temporarily install the the other supports to mark the hole locations in the top for them.  After getting everything marked, we again removed all the supports.  Lots of steps forward and backward.

The remaining holes were drilled using the guide and angle adapter. A very fatiguing process to hold the guide on the underside of the top and drill the holes. The rotary tool was again brought into service to clean out the core material from these holes.  And finally, thickened epoxy was once again used to fill all these new holes.

So, after two days of work, we had holes in the top of the cabin roof and resin dots on the hardtop.  A lot of work but it doesn't feel like a lot of progress. I know I will feel differently soon though, after those last holes are re-drilled and the supports go on one last time to do their job holding up the top.