Ed Note: This post is pretty much based on boat building techniques, but I know of car and bike builders that (very sensibly in my opinion) visited a few boat yards and buy the same products as the boat builders and save themselves hours of work on finishing. DC.One of the marvels of the modern boat building age is the development of adhesives, fillers and paints. In your own shed/barn/garden you can now produce the same sort of finish that 10, no maybe even just 5 years ago would have been only possible in a few boat yards in the country.
The biggest issue in the process of refinishing is trueing up, or fairing a surface. We used to mix epoxy resin with micro-balloons to form a skimmable paste, but man it was messy - and expensive, if not in materials (actually, yes in materials) then definitely in man-hours. Once that was done and had cured, you needed to get the long board out, but epoxy adhesives being what they are it was hard work - Not that we're scared of that around here, but long boarding a filler which has set like concrete is a long expensive process. Once that was (finally) done you'd use a high build primer applied with a brush, which was almost the same as normal primer in thickness, so you needed 2 coats of it. Then you could see the low points (man I'm boring myself here! - you can imagine how dull all of this is in real life!!) and you'd use polyester filler to tickle up the las few dips and hollows. After an all over sand, the the top coat primer would go on and then once that was flat and yet still covering the whole surface, you'd get the thing sprayed up to a finish. Weeks and weeks of work and unless done very carefully, adding heaps to the weight of the boat.
2009 and thanks to the paint companies all wanting a slice of the high performance keel boat market from Melges 24 to America's Cup and everything in between, epoxy paints and primer/fillers of all types are on the market.
You can carry out your repair and then after a rough sand to key everything up, skim with a super light fairing filler - many of which have a specific gravity of less than 1.0 - (Ie they weigh less than water) All of the surfaces of the skiff have been skimmed using this product - Nautix Blue Epoxy Filler - which weighs just 600g per Litre. When it has cured, we hit it with a long board and it's like sanding polyester car filler - easy. With the shape trued up, we roller on (yes ROLLER) a coat of hi build primer, which unlike it's predecessors really is thick. It goes off fast (like sandable in 3 hours on a warm day). The long boards come out again, followed by the electric dual action (DA) sander (rotating and vibrating orbital sander). Then finally a wet sand with 240grit wet and dry - and you are ready for a top coat!
Here's where it really gets interesting (in a paint mixing way!) The surface finish from the modern epoxy primer is better than the gloss top coats of 10 years ago - particularly when the boat is sliding through the water. So now we don't spray on a topcoat, we roller on using a fine foam roller, a high performance epoxy primer like Durepox as a top coat. When it has set, we polish it with wet and dry, right back to 2000 grit, then use cutting compounds. It comes up like a gloss. The advantage of the hard work is the boat slides through the water quicker (Ok, we'll have that discussion fully another time) but from a practical point of view it means any damage or repair work can be fixed double quick. Very soon the boat will be in it's fully finished colour - and under it you will find just one coat of hi build primer and some lightweight filler. QED.
8.30pm on Wednesday June 24 2009 and GBR52 has a rig put on her for the first time in maybe 4 years. We went straight for full rig tension, which although it made the mast creak and the pins bend in the chainplates, didn't seem to bother the structure of the skiff, and even though we put multiple tape measures on her, there didn't seem to be any hull deflection in any direction.
In higher loaded areas, for example on the deck of an 18ft skiff where 3 blokes will run around while the boat bounces up and down, it is best not to leave too much to chance. As watertight and solid as it feels, 0/90 standard taping isn't enough. Instead we took some time and cut some 45deg/45deg tapes from a metre of standard woven fabric - in this case a 200g/sqm carbon fabric. Lay up, peel ply, wash up and rest assured that all of the fibre is doing something to hold the deck together - and consider torsional or sheer case loading, the fibre is more directly resistant to loads. Savvy?
The thing is I guess better materials, computer modelling and the relentless driver of competition has developed sailmaking to a proper science and meant in the last what, 5 years? the industry understands better why this rig is more efficient and goes faster - and it is not the area that does it.
