What Glass / Epoxy to sheath wooden rudder blade with?

[seumask]

I have just striped the many layers of paint back on my mahogany lifting rudder blade and I would like to sheath it with epoxy and glass. The principal reason for this is to give it a slightly higher strength and lower maintenance.
My question to the forum is what weight and type of Glass cloth do you suggest I use and can anyone recommend a suitable supplier. The Rudder Blade is approximately 1800mm long by 400mm wide.
I am aware that the blade will need another coat of paint or Varnish once sheathed to protect the Epoxy from UV discolouration.

 

[NigelClegg]

West, SP and Epiglass all make suitable epoxy resins for a project like this.

In my experience, it is best to use a fairly lightweight woven cloth, (say 280 to 450 gram), as this will be easier to work than heavier cloths. As a guide, a single layer of 450 gram cloth will provide a thickness of 0.6 to 0.8 millimetres if properly consolidated, so three layers will provide around two millimetres thickness. Good, tight consolidation is important to keep weight down, to minimise air voids and to achieve maximum strength. Professionals often use vacuum bagging techniques, but you should be able to achieve satisfactory results using DIY tools on a rudder blade.

Epoxy resins usually stick extremely well to bare timber, but they do demand warm, dry conditions for optimum cure and strength. Too low a temperature (below about 10 ~ 12 °C) can result in undercure of the epoxy, so it never provides optimum strength of moisture barrier properties.

Moisture and humidity is another problem, and can result in ‘amine sweating’, where a thin layer of sticky amine carbomate forms on the surface of the epoxy. If not removed, this will behave like a mould release agent, preventing adhesion of subsequent layers. These problems can be overcome by using and curing the epoxy in suitable conditions, and by laying each layer of cloth as soon as the previous one has become tacky; rather than allowing the resin to cure between each layer.

You can also buy a material called Peel Ply, which is applied onto the final layer of glass, whilst the resin is still wet. This prevents amine sweating, and when pulled off, provides a ready keyed surface.

As far as varnishing is concerned, if you really want a varnished surface, I would use several coats of two component polyurethane varnish, as these are much tougher, and have much better water resistance than normal yacht varnishes (or enamels).

If the boat is to stay afloat, it would be better to apply four or five coats of International Gelshield® 200 as an antifouling primer onto the new epoxy laminate, followed by two or more coats of the antifouling of your choice.

 

[seumask]

Thankyou for your comprehensive reply.
This is similar to what I suspected.
Rudder is usually out of the water when the boat is not in use, so it wont be antifouled.

 

[retsina]

I sheathed a whole wooden boat 23 ft with West and wooven cloth; very effective and expensive. Must be moisture free and warm environment. You need to protect it from uv exposure. Point of caution, epoxy sticks on wood, fibreglass does not.

 

[vyv_cox]

West have recently produced a DVD that reputedly covers just about everything you need to know about using their product, at a cost of about £7. Sounds like a very useful bit of info, runs for 55 minutes. Apparently is on sale at many of their distributors.