Thickened epoxy using sawdust

[Milehog]

R88, there is no shortage of YouTube incompetents for any discipline. Some of the worst offenders are the best salesmen. Beware.

 

[magnus]

No in theory it sounds great, do not clamp tight, but we have all done this and stuff moves around and we are to leave our c clamps loose? It does not work, maybe spring clamps in their limited applications.

I am attaching wood gunnels inside only to infused canoes in the mold. Once cured I use simple screw jacks pulling under the gunnels supported at the mold flange at the stern and bow. This is a good bond test I think. I experimented with one of my seconds by not wetting the wood but only applying epoxy/silica to the wood generously and had my first seperation of wood to hull during part pulling, lots of pressure. One end/one gunnel, three remained solid.

I agree with all that say you should always pre epoxy first and let it get tacky. I have been good with epoxy/silica after that. I do not work with sawdust as others have said it has many problems. For aesthetic work, minor fills, I will save my top sawdust, nothing off the floor, and process it in the blender, you can make flour or any thing in between. Do not tell your wife.

I also have started to use the fiberglass mesh used by amateur drywallers like my self to maintain a gap with pressure. It is only 5 mils thick but I double it up, It is 2 inches (50 mm) here and is a0/90 grid so easy to cut with consistency. It has a light tack but I put the epoxy to the wood first. Cost is nothing. Not sure it is necessary but maybe insurance?

 

[BlueBell]

There are several issues with using sawdust. The first is contamination, you don't really know what is in it. Second, it is an absorbent load. That means that, as was noted before, it may starve the joint. The only way to keep the joint wet, is to make the mix runny, which does not work well for fillets. Third, as has been noted by other posters, the finish will be rough and hard to finish. Fourth, it will use more resin than fumed silica, which will offset any savings. Epoxy is a lot more expensive than silica. Finally, the rough surface will greatly increase the labor and the cost. You will have to use abrasives and cleaners.

I think this needs repeating.

 

[magnus]

Agreed.