Hi Spidey,

I don't use much but I could not do without it. Some uses: Fillet on the inside stems, two fillets for the carbon coaming, all hardware bonding including footbraces, tip filler for bow grab loop, thickener for inside seam tape to mention few. Fillets are not just for strength but to span sharp gaps as well.

The problem with microfibers alone is that they don't increase thixotropicity in a controlled manner. To use an analogy, if you mix water with coarse sand, the mixture will be somewhat cohesive but the water will always ooze out. Now add fine clay dust or lime (fumed silica) and the mix will change into nice putty that holds its shape and doesn't sag. Thixotropic putty is important when the fillets are more horizontal such as the coaming rim fillet and you want them to hold shape after the masking tape is pulle off. You can mix in more microfibers but instead of better putty you will get porous stiff stuff that is harder to work with. As I said you don't need much but the small amount you use will make life easier :)

Vaclav

> Hi Vaclav;

> I enjoyed your site and your construction book a great deal. I'm starting
> to lean toward your composite graphite coaming for my first build, because
> it looks strong and elegant. Did I mention Cool?

> Your degree in ME and material science perhaps makes you the perfect
> person to answer this simple question: Where in the heck would one employ
> a colloidal silica & epoxy mix on a kayak? It seems like fillets are
> almost always used for strengthening a joining of surfaces of one sort or
> another, why not always use micro fibers? They are of approximately equal
> cost, definitely stronger as you said, and probably produce a noticeably
> clearer mix (I haven't gotten to the filleting stages yet 8-). I can't
> imagine a weight penalty whenever you use a structurally superior
> material, i.e., epoxy + micro fibers. Perhaps the microfibers don't
> thicken the mixture enough . . . ?

> Best Regards, Spidey