It’s not that easy to generalize and say this is how it’s done – there are always so many exceptions. Experience will tell you when to take what path. Having said that, and assuming the experience level is modest here is how I’d do if I hadn’t done it before.
I’ve never worked with Polyester, but the method is very similar.
- Sand the hull smooth and fill all cavities and holes with Bondo or similar. I’d typically go to about 18-grit sand paper. Don’t prime or use any type of base coat. It’s unnecessary and will only get in the way.
- For a beginner it’s easiest to use a patch-work approach to applying the fiber glass cloth. There are several advantages. The idea is to lay single strips from keel to railing vertically, but short segments along the length. The curvier the hull, the narrower the strips (more segments along the length).
- Cut 30-50% more strips than you think you’ll use.
- Starting at the stem and working towards the stern. Alternating left and right.
- At the keel, overlap the strips over the keel.
- Take a paint brush and cut the bristles about half-way to create a pretty stiff brush. It should be an inexpensive brush, but of appropriate quality – the bristles should not fall out as they tend to do on the least expensive Chinese and Indian brushes. Don’t spend a fortune either. After the Epoxy cures, the brush is dead.
- Mix the Epoxy and work as fast as you can.
- Position the fiberglass with one hand and wet it with the brush in the other hand. Start in the middle of the strip and wet it out towards the edges. You have to use a stabbing motion, not sweeping as you would when painting. If you sweep (especially at the edges) the cloth will fray and look ugly.
- With the brush, work out any air bubbles that may appear. Usually repeated stabbing will make the air disappear through the cloth.
- Keep covering. If you run out of Epoxy somewhere mid-way, try and mix up a new batch quickly and keep going.
- Any wrinkles need to be worked out. Sometimes they will come out easily by carefully working them with the brush. Sometimes you’ll have to lift the cloth and tug on it a little.
- Once covered, focus on the edges – get bubbles and air gaps out.
- Let it cure, but come back within a few hours and assess how much clean-up you’ll need to do
- As soon as the hull can be handled (usually after 24 hours for slow curing Epoxy), do a rough trim of excess glass cloth and epoxy along shear line or bulwark.
- At some later time depending on cure speed, start sanding. Go easy on the hull itself, but clean up the edges and bumps. Worst case you’ll need a second or third layer.
- To lay subsequent layers, the hull needs to be cleaned from the fatty residual layer that forms on top of cured Epoxy. Iso-Propyl Alcohol works well for this.