The weather changed our plans today, and kept changing them. We thought it was going to be wet most of the morning and then it wasn’t. So we cracked on, then it become more and more clear that from late morning tomorrow is going to be very wet. So it became something of a race.
By lunchtime we had 11 holes in the hull and I was writing “More and bigger holes in our boat” by about 5pm we had finished all the preparation. We have been following a guide from West Systems: Repairing machined holes in fibreglass
Jane had done most of the grinding the outside of the holes. The idea is to make the hull around the hole about 5mm thinner and then taper this to make a circle about 15cm diameter where the paint and gelcoat has been removed.
Meanwhile I was sanding the inside around each hole. This doesn’t need to be deep, you just want to be sure that the surface is ready for epoxy resin to stick to it.
Then I used the dremel on every hole to flare them out on both the inside and outside. The idea is that the hole becomes a bit of an hourglass shape. Then you fill it with thickened epoxy resin (resin with wood flour added to make it peanut butter consistency) and once set it is held in place by it’s shape as well as the bond with the original grp.
For the larger holes West Systems recommend creating your own resin “puck” by allowing some resin to go hard in a plastic cup the right size. We were short of time and didn’t have plastic cups the right size. So instead I used hole saws to cut pucks out of the FR4 sheet that I have bought to make backing plates from. FR4 is very dense fire resistant epoxy fibreglass.
We then cleaned around all the holes with a acetone type of liquid and washed it off.
Then an epoxy race began. Our bio-epoxy resin is a 2:1 mix of resin and hardener and it has a limited time before it starts to harden.
First task was to coat all the exposed fibreglass inside and out with standard resin mix. This ensures all the bits of fibreglass get wet with resin to improve the bond.
Jane did the inside and was rushing from cabin to cabin with her pot of resin while I followed up on the outside.
- 3 holes in the aft heads
- 2 holes in the motor compartment
- 2 holes in the galley
- 1 hole in the saloon
- 3 holes in the forward heads.
With floorboards up and stuff cleared out of the way it was a bit of an obstacle course.
The next step was to add wood flour to the resin to thicken it up. We got a bit nervous and I don’t think we really got it as thick as would have been best.
It was thick enough for me to fill all the small bolt holes (4 around each main hole).
Then I was rushing around finding props so that on the outside each hole could have plastic (we reused plastic bags from various packaging), then a square of foam (cut from a damaged form square we have used for temporary flooring) and then a timber prop to hold it in place.
As I covered each hole in this way Jane was suffling through the cabins putting in some thickened resin, then the FR4 puck and then more thickened resin, with a short pause to mix up another batch of resin.
We finished at about 8:30pm (not the colour comes from the wood flour, the resin is clear).
Fortunately, Jane had made a lasagne at home and brought it frozen so we tidied up a bit and then sat outside in the dark eating lasagna and drinking Sainsburys £4.85 wine. Then final tidyup and showers.
We can do the inside fibreglassing even if it is raining and the outside can wait for a fine day.
Overall we are absolutely stoked that we got this much done in a day. This was a huge day for progress towards being able to float (and the work on the stern tube flange this morning a huge milestone towards getting the motor working).