I just recieved my poxy-shield in the mail and it came with some fiber,microspheres and silca fillers but no information on using wood flour as a filler.
Has anyone used this product with saw dust as a filler. Say belt sander dust?
I tried the sanding powder from my orbital sander... I thought it was lumpy and hard to get a satisfying consistency because the grains were all different sizes and it didn't spread smoothly. It is likely that I wasn't doing it properly. I really like the West System colloidal silica filler; it produces a nice smooth paste when mixed with epoxy that is about as hard as the wood when dry so it is easy to sand. You have to wear a mask when mixing it however, because the silica powder is so fine it behaves like a liquid and puffs up easily. Apparently it's bad for your lungs.
I have never used Poxy-Shield so I don't know if this applies. I have got to where I use talcum power for almost all thickening needs. It has great strength although it is a bit harder to sand then some fillers. Still easier than wood flour from the sanders. For small fixes and fairing jobs I use the more conventional fillers you mention. Hope this helps... 8)
Talcum powder also has the additional benefit of providing a cool and dry feeling if you spill it on yourself....
I buy wood flour from Raka.com
It is rather cheap, far cheaper than my time is worth sifting sander dust and much more uniform. And since I learned how to sharpen adjust tune and use handplanes, I never take the beltsander off the shelf anymore. And curly cue wood shavings don't make much of a thickener. It does make right dandy tinder to start up the woodstove to burn off the rest of the cutoffs and heat the shop in the winter though.
I get large bags of it both Pine and Maple wood flour.. The pine gives a light colored fillet, and the Maple gives a deep chocolate colored fillet.
I use silica and wood flour most of the time, except for bondo where I use silcia and micro balloons or areas where I think abrasion might be constant then I use just graphite. I have had great luck with those combinations.
Thanks for all the info guys. Tried the wood flour myself and this was very inconsistent and lumpy =(
I have never used straight wood flour. I use a fairly even mix of silica and wood flour. I always stir in the silica first. It is hard to get the small white clumps mixed in but after about a minute of stirring they break down. Then I add in the wood flour and it mixes without clumps. I read somewhere the silica really aids in smoothing the mixture and it seems to work for me.
For example when making a 3 tbls batch of epoxy I add the 2 tbls of resin and the 1 tbls of hardener together and stir those for about 1 minute. Then I add 2 heaping tsp of silica and stir that in for about another minute (until it is smooth). Then I add 2 or 3 tbls of wood flour depending on how thick I want the batch. This would be for bonding or maybe filling in over the screws.
I am no expert but the surfaces sand out smooth enough that you can't feel the epoxy spots over the screws and no other fairing is needed in those areas. This is pretty basic and I apologize if it seems condescending. It was all new to me when I started my boat project so I am adding this because it might be new to someone else also
I am very new to boat building and epoxy so you have done a wonderful job of answering my question. Thanks again!