Epoxy thickened with milled fibers & silica weight

[abosely]

Wondering what epoxy thickened with milled fibers and silica weighs per cubic foot.
Obviously the weight would vary depending on ratio of epoxy, milled fibers & silica.

Figuring with as much milled fibers and silica to make peanut butter consistency with as strong of mixture when filling an area for compression strength.

Like when filling a V shaped void in bow section or between built up keel & ply skin.

Thinking of difference in weight between laminating pieces of wood (Douglas fit for example) bs filling area with epoxy, milled fibers & silica.

Not filling a huge area, but something that would be easier to fill void with several layers of thickened epoxy to build up without causing epoxy heating up.

Have no idea what a cubic foot of epoxy thickened like this would weigh compared to DF at around 32lbs cuft.

Just looking for rough idea of weight.

Cheers, Allen

 

[fallguy]

Epoxy wt/gal, typ 9.1#/gallon
Milled fibers, type 6.5#/gallon (can vary)
Fumed silica, neg

say off the cuff

5% milled fibers


The epoxy weight is the majority; gonna come in around 8 pounds per cuft, off the cuff

 

[abosely]

Ok cool thanks, just wondering real rough guesstimate.
Had no idea at all.
Don’t have need for it now, but was wondering if it would be bit lighter than wood like DF or similar.

That helps give general idea.

 

[fallguy]

Doug fir is gonna be about half the weight or more.

 

[abosely]

As in Douglas fir will weigh about half the weight of the epoxy mix?

 

[fallguy]

As in Douglas fir will weigh about half the weight of the epoxy mix?

Yes.

Epoxy at 9.1 pounds per gallon is 9/0.1336 or 67 pounds per cubic foot versus water at about 62 pounds versus doug fir at 32 pounds...

This helps explain how wood floats...

Also important to note; the ultimate strength of clear doug fir is likely a lot higher than epoxy and mf and fumed silica...

 

[fallguy]

Your query is a good one. I'd say anything 1/2" wide by half inch deep can be filled with putty, but beyond that use wood, or wood in combination with putty. Because milled fibers do basically nothing in the matrix; they can be eliminated and you would just mix fumed silica in the epoxy; then prewet the doug fir with epoxy before bedding it into compound. If you don't prewet; it is a very good formula for the lumber to drysuck the resin in the joint.

The putty helps because fitting the fir 'stem' is almost impossible to do well enough for clear epoxy..

 

[aaronhl]

I might do a test but maybe someone else has, does epoxy lose weight as it hardens? How about polyester based resins puttys or gelcoats?

 

[fallguy]

Nope.

It is a heat reaction. If epoxy is left out prior to cure; it loses some stuff to the environment, but it is not much, and then not really usable.

I expect esters are similar.