Introduction

My name is Frank and I am going to write some articles about the use of epoxy in boat building. I'll try not to be too technical but will focus on the practical site. If you have any subjects you'd like to see covered please let me know.

A little more about me: I'm the owner of 2 websites regarding boat building - www.europe.boatbuildercentral.com is the european branch for the US site www.boatbuildercentral.com. We are selling epoxy and wood kits for the Bateau building plans throughout Europe. The other site is www.mrboat.nl and sells Epoxy and supplies for Dutch customers (not only boat builders). I also have a weblog about water(sports) and everything related. It's called Mr.Boat Blog (www.meneerboot.blogspot.com) . Some of it is in Dutch but I think the site and the pictures are very self explenatory.

If you have any questions or comments please feel free to email me.

About Fillers

We get a lot of questions from people why and how to use fillers. Epoxy resin is too thin for some applications. For instance glueing or filling. Fillers are used to thicken the epoxy resin. Because of this the epoxy can be used for several applications. Thickened to a ketchup like substance, the epoxy is perfect for glueing. If you add more filler so the substance has the same thickness as peanut buter (nutella in Europe - Ed.) it won't drag so you can use it as a filler. There are ready to go epoxy fillers but they tend to be very expensive. We prefer to make our own. Cheaper and it can be made to meet our specific requirements. There are a lot of different types of fillers, each with their own qualities (and price). For example there are: wood flour, cotton fibre, chopped glass fibres, Stewathix, microballoons and aerosil. The choice for filler depends on the way you want to use it. The first distinction can be made between fillers with high or low density. Fillers with high density are generally the strongest but also the heaviest. A low density means a light mixture which is, in general, less strong.

Overview of most-used fillers and their properties.

Wood flour

Very fine sawing dust. Makes a good filler for many applications such as glueing and making filets. The wood flour gives a pale brown colour which is perfect for applications in which the wood remains visible (bright finish). Always coat with epoxy after sanding because of watertightness. And hey it's cheap! You can harvest it from the dustbag on you electric saw. (you should first pass it through a fine kitchen sieve to keep the big chunks out - Ed.)

Cotton fibre

Consists of small chopped cotton fibres. Makes a good, cheap filler for glueing or making filets. Cotton fibre is white and the hardened epoxy has an off white colour. To make the fill lighter you can combine 50% of cotton with 50% of Stewathix (or Aerosil).

Chopped glass fibre

Fine glass fibres. Cheap but rather heavy. Perfect for filling large holes.

Stewathix

Very fine and light powder. Same characteristix as Aerosil but much less dusty. Mix 50% cotton and 50% stewathix for a relative light but strong result. Also perfect to use it as a fill.

Aerosil

Available in several densities. Aerosil a very fine and light substance that, when mixed with epoxy, gives a strong and light mix that won't drag. The disadvantage is that it's hard to sand.

(Red) Microballoons

Very small phenol-balls. Available in red and white. Are used to make light fillets but is not very strong. Because of this it should only be used on corners and wood up to 6 mm. thickness. Microballoons also make the hardened epoxy easier to sand. After the sanding the filets aren't watertight anymore and should be coated with epoxy. The red ones are used when you desire a wood finishing (you can mix red microballoons and cotton for a stronger red/pink glue or fileting mix that looks OK with bright finished okoume - Ed.)

In general: don't mix to much filler in once but add in small portions and mix it well.

I will add some photos and personal notes at a later date - Ed. PS I prefer "filet" and "filler" spelling though "fillet" is an accepted variant.