For years I’ve been pushing polyester auto body filler as one of the best materials there is for filling holes, dents, cracks and gouges in wood. I think it was this past month’s Old House Journal (I can’t check, they’re packed) that had a letter from a carpenter disputing a recommendation to use Bondo for wood patching – he said it doesn’t expand and contract with the wood and he gets called in to fix it. (So I guess it makes him money!) I can’t remember what he said to use instead, but the issue should still be on the newsstands.
The cost would be dependant upon the specification you would like to make your mould and indeed your part from, choices range from general purpose resins to tooling resins for you mould, it would be more economical to manufacture your bonnet moulding from polyester resin and chopped matt, but you can make it lighter and stronger using epoxy resins and more exotic materials like aramid and carbon fiber.
For example I do know that talc will make polyester resin less brittle (since polyester suffers from this) but I doubt whether it will add much extra to epoxy and I’m pretty sure that in the case of polyurethane resin it will weaken it, just as other fillers do. Another of the main reasons for adding fillers is to make the cast material easier to machine or sand, in other words basically weakening it, and this is particularly true of polyurethane.
Vinyl ester resins share the same cross-linking monomer (styrene) to polyester resins and Gelcoats so they are compatible with each other – you can actually mix the two together if you wanted to. Vinyl ester resins and blends of vinyl ester and polyester resins are often used as a blister resistant skin coat behind polyester gelcoats for boats etc.
By sloshing, banging, vibrating and, where possible, sticking your gloved hand or a brush in there and physically displacing the bubbles, you can get the air to rise out of the gates or vents of a well designed mold, if the resin isn’t so heavily filled that air won’t rise through it. The other solution is to apply pressure, and there are 2 ways to do that.
It is a wall plaque about 2ft x 1.5ft and my initial thoughts are to use clear cast resin mixed with marble dust (coarse and fine) for a gel coat with a little white pigment and maybe some ochre to vary it in places and slush mould it. Presently it is open backed but I will put a back on it to get the section down around the main feature of the plaque which is a horse.
GelCoat 65PA or Flowcoat 65PA and Crystic 491PA will be food safe when fully cured – all polyester resins will retain a small amount of free styrene which can taint water or food when they are cured at room temperature and need a post cure treatment in order to make them fully cured and non post cure schedule should be 3hrs at 80 deg C – this may be difficult on such a large area but some post cure will be required in order to make the laminate non tainting.
Rot and general wood deterioration in cored decks is a particularly difficult problem, largely because it’s so hard to get at. We hear more about it in sailboats than power boats, probably because sailboats have more hardware sticking through their decks (and therefore more locations for the water to get in), and because they are often driven harder in worse weather conditions than power boats.
We realize that epoxy resins are expensive, but it takes an adequate amount to create the solid base for your engine lags/bolts to attach to. Just remember that the resin is a lot less expensive than paying someone to remove the engine, cut the tops off the stringers, replace the wood, re-glass the stringers, and then re-install and line-up the engine.
I am thinking of making some children’s climbing holds using a foam and RTV silicone method as described on -your-own-climbing-holds/?ALLSTEPS The contributor uses lentils as filler but I’m not sure I’d want to use these as when sanding the back of the hold to a flat surface the lentils would probably become exposed and subsequently absorb moisture (I will be fitting outdoors).
RTM,cold and hot press moulding – 20Kg per tonn of resin a guide for normal hand lay up in open moulds you are likely to lose 5/10 % of the styrene content of the resin,this depends on surface area,temperature equates to around 21 – 42Kg of styrene per tonne of resin used,if you are using closed moulds where there styrene is contained then you will be emitting a small proportion of this figure.
We had some broken windows of late and I personally made my own, materials that give most transparency were powder bound chopped strand matt, laminated with a translucent sheeting resin, this is not often at hand so I used the water clear casting resin and gave decent results, 2 layers of 450g matting should be strong enough for a decent size stone to rebound off!
Example 14 This is an example illustrating the preparation of an air-drying ethylene glycol/maleic polyester having in its molecules an average of two residues of a 1,2,6-hexanetriol/formaldehyde acetal, and illustrating the use of such air-drying polyester in a pigmented, thixotropic coating composition adapted for general trade usage when applied over a catalyst-containing basecoat.
Filling the resin also helps produce castings with fewer shrinkage and heat problems. Surface repairs assume that the basic structure of the area to be repaired is sound and treatment is required only to stop wood deterioration or to fill areas where some wood is missing. I did have some success (>3 years) with an epoxy system that involved first saturating the wood with a very thin liquid epoxy and then applying a thicker paste to fill the gaps.
Fiber glass isn’t necessary, but if you want something strong as hell, I’d recommend mixing in wood dust/filler into a two-part epoxy and thicken to a peanut butter consistency. I think generally if you want c. 15mins working time the usual option is polyester resin as opposed to polyurethane. Adding 20% to the polyester resin will make a difference but you can add higher levels if necessay. Polyester resin is the resin component of most fiberglass layups and is normally glass clear.
After the wood is cut, trimmed, drilled and ready to install, it needs to be treated to prevent deterioration and delamination. To increase the quantity of powder to a resin and retain the flowability, a second, or even third filler powder of a larger particle size should be used. What I’m trying to do here is cover a couple of the sides on this void so that the filler when I put it in just ooze out. If the wood turns out to be good, squirt it with some CPES and then after the CPES cures fill in with an epoxy filler.