Filler mix question

Louis Michaud

LOVES Wooden Canoes
Going to try to use the filler receipe from W.B. #16. I have access to diatom. earth and would like to use it instead of the regular silica. It takes about 6 cups of diat. earth to make 1 pound. Seems it's a lot lighter than the regular silica. Just to give me an idea how much should go in to replace the regular stuff: how many cups of regular silica does it take to make a pound ?

Thanks!

Louis Michaud
 
Louis,

I'm not sure you would want to substitute diatomaceous earth pound for pound for the silica in tradiational fillers. Silica or silicon dioxide is very heavy per unit volume. Diatomaceous earth- the mined form of once-living diatoms- should be much lighter per unit volume because the shells of diatoms consist of hydrated silica embedded in an organic matrix; they have many microscopic pores and are hollow, both of which make diatom shells much less dense than silica. Thus, if you did a weight-weight substitution your filler would contain a much higher volume percent of diatomaceous earth than it would have had with silica, making the filler much too viscous. Therefore it seems that a volume for volume substitution would be more appropriate, and would provide a filled canoe of lighter weight.

The use of diatomaceous earth has been discussed before. Has anyone out there ever tried it?

Michael
 
Bonjour Michael,

"that a volume for volume substitution would be more appropriate"

Seems my mastery of the english language leaves to be desired... This is exactly what I was trying to say... I've searched the archives and some have used D.E. but nobody reported on the amounts used. I figured if somebody could tell me that 6 pounds (or any other amount) of silica equals "X" cups, then I could do the conversion to D.E. using the cup as a volume measure.

Louis
 
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