May 1st, 2008 Posted in hack, sailing, viper 640 | 2 Comments »
As I upgrade my Viper 640 to mirror the placement of the controls on the new Rondar-built boats, I needed to relocate a turning block for the spinnaker halyard/retrieval line to a new location on the cockpit floor. Unfortunately, the underside of this new location was impossible to reach through any existing inspection port, so there was no way to easily install a backing plate into which I could then screw the eye strap for the new block.
To use business-speak, this challenge presented an opportunity to apply a hardware installation method suggested by Brian Bennett, the designer of the Viper 640. Thanks, Brian for the process. It worked like a charm! Using your method it’ll be possible to install hardware pretty much anywhere on the boat without having to cut any new inspection ports to get at the underside of hardware locations.
Here are Brian’s instructions verbatim:
“As the boat is Epoxy, the best local repair and strenghtening can and should be done with G-10 (Garolite). This is a compressed fiberglass sheet product which can be tapped into (and American made). Because the Viper is a big can, you need to use a material than can be tapped without need for backfastenings. G-10 will do this. You will have to cut a hole (or slot), sand the piece of G-10 (I would recommend 8 - 10mm), and epoxy the contact side, before passing thru to the inside, and holding up in place while it cures. In the past I have used a piece of seizing wire, then just cut the wire when the epoxy goes off.
The core can then be backfilled with epoxy and the outside sanded and finished. Then your hardware can be installed via drill and tap method. The G-10 should be twice the size of the fitting you are installing.”
Here are a few photos of the process on my boat:
Brian had recommended 8 to 10mm thick G-10. I had access to some sheets of 1mm thick material (Thanks, Dave!), so I ended up building up a sandwich of 8 layers of the stuff epoxied together under mild pressure, which yielded almost 10mm thickness. And man, this stuff is dense and strong! Given that my 10mm thickness of G-10 was home made, I wanted to test it to make sure I could drill & tap it, and then also test its screw-holding capacity. So I drilled and tapped a hole for a 10-24 screw in the corner of the backing plate, which went smoothly. Here you can also see that the backing plate has been scored agressively (with coarse sandpaper and a hack saw blade) to help it bond to the deck once it gets epoxied.
Next, it was time to put a screw into the freshly made threaded hole, and test the G-10’s screw-holding power. In this photo you can see the screw in the backing plate, but unfortunately I didn’t get a picture of the next step; I clamped the G-10 with the screw in it to a workbench, put a pair of vise grip pliers on the screw head, and tried to yank the screw out of the G-10 as hard as I could. I ended up picking up the corner of the workbench, and the screw didn’t budge (nor did the G-10 flex at all, for that matter. This stuff is STRONG!) So, the test was declared a success. Time to get to work on the boat!
This step one was the easiest, AND most terrifying… cutting a slot into the cockpit floor. Below you can see the slot cut in the cockpit floor, with the backing plate that will go in the hole, and the eye-strap that is the point of this whole exercise. 
Below you see a test fit of how the backing plate will be inserted in the hole in the next step.
Next, I drilled a couple of small holes in the backing plate, exactly where the screw holes for the pad-eye will eventually be, and led a couple of long pieces of thin wire through those holes. The wire is there to pull the backing plate back up against the underside of the cockpit floor once it’s been fed through the slot in the floor. I put the wire exactly where I want the screw holes for the hardware to eventually be, for two reasons that should become obvious shortly.
Now it was time to mix up some epoxy. Two pumps of West system were enough for the job, with some high-density filler mixed in to thicken it slightly so it wouldn’t all drip off the backing plate while I was sliding it into the hull. I covered the bonding surface of the backing plate with epoxy, and fed it into the slot being careful to hold on to the wire “tails”!
Once the plate was inside the slot, it was easy to flip it flat against the underside of the deck and maneuver it into place with the two wire tails. By centering the two pieces of wire in the slot, I could also make sure the backing plate was located exactly where I wanted it (one of the reasons to drill for the wires where the screws will eventually go. In this picture, you can see the very high tech (NOT!) scrap-lumber tripod and screwdriver used to tighten the wire, pulling the backing plate up against the underside of the deck.
The Shiner Boch is there purely to provide scale and some Texas authenticity to the project. 
Once the backing plate was held in place by the tripod, I filled in the rest of the slot with thickened epoxy. Here I should have thickened the epoxy further, to “peanut butter” consistency, so I could fill the slot and then scrape off the excess with a straight edge. The way I did it, I ended up overfilling the slot and couldn’t scrape it flat since the epoxy was too liquid. This made for a little more grinding work later to flatten the epoxy.
After the epoxy set, the wire tails were cut off, and it was time to grind/sand down the epoxy plug.
Once the surface of the plug was flush with the deck, it got drilled and tapped for 10-24 stainless screws. The remaining wire also got drilled out in this step, so as not to cause a corrosion problem down the road (the second reason why the wire tails were located exactly where the screw holes would later go)
Finally, it was time to screw in the eye-strap. A little 3M 4200 on the screws to seal the holes, and that’s it! Of course, I forgot to take a picture of the finished product, but it looks great and feels rock solid.
This first time took almost an hour from start to finish, but now that I’ve done it once, I think I could cut the total time required to maybe 15 minutes. For hardware like the eye-strap I mounted here, I probably will also have to paint the small exposed epoxy area for cosmetic purposes and for UV protection. For other hardware like cam cleats and cheek blocks that I need to install next, I plan on cutting the slots so they will be completely hidden by the hardware once it’s mounted, so the end product will be completely invisible.
Thanks again, Brian Bennett for the process.
Capri 22 sailboat. We had some great times on that boat, learned some lessons, and even had a couple of close calls (stories for another time). Now, it’s time to move on.