A while back I wrote an entire article about epoxy 'tools' and included a
vast array of fillers {check the archives at www.duckworksmagazine.com . . .
under 'Columns'}

Basically, my STRUCTURAL 'filler of choice' is wood flour. In addition to
it's capabilities as a filler, it also has thixotopic properties. Silica is
more of a 'thixotopic additive' than an actual filler . . . as in
'non-sagging'. In addition, it cures VERY hard. Phenolic and Glass Micro
Balloons are in the COSMETIC class of fillers, along with Talc . . . hence
the ease of sanding. Because their surface is then rather porous, a further
'painting' with un-thickened epoxy is recommended.

Take a look at any number of booklets on the subject from almost any of the
usual suppliers {I use RAKA from Larry Steves}. Get familiar with the
properties of all the typical fillers. Then you can either use them 'as is',
or mix them to 'custom match' the filler to YOUR particular task. Along with
Wood Flour, I keep on hand {in order of 'hardness'} Fumed Silica, Phenolic
Balloons, Glass Balloons, and Talc. I also keep Glass Fibers {1/4 inch} and
Milled Glass Fibers {1/32 inch}for when I need extra strength of
cohesiveness.

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"raposaNegra" wrote in message
om...
I have been using Phenolic Micro Balloons while taping the outer
chines, transom, and bow of my drift boat (especially to hold the tape
in place on the vertical surfaces) and as fairing compound to smooth
everything out after taping, because of the ease of sanding, but have
noticed tha glass micro balloons are about 1/2 as expensive as the
Phenolic balloons.

What are the strengths/weaknesses of using the glass balloons vs the
phenolic vs wood flour (which I used over the tape on the fillets of
the inner chines)?

I have also been considering using in the future a mixture of micro
fibers and some type of balloons w/ maybe a little fumed silica in the
future for my chine work, with micro balloons for fairing and
smoothing.

What are the relative merits of the different fillers above mentioned?

Thanks!