What is the difference between flat weave and plain weave volan? i have used plain weave but i was looking at fiberglass supply and saw flat weave. Just curious. Austin S

I had seen that too, and kinda wondered what it was, then I saw it was often a term applied to woven roving and such so it kinda made more sense, as in ‘aha, now I know what they mean’.

To begin with, pull a strand out of a piece of plain weave common, garden variety cloth. You see it has a twist in the ‘yarn’, which is the generic technical term for the bundles of strands in something woven. As it’s twisted, it’s gonna have a round cross-section and it’s gonna stay pretty round when it’s woven. Kinda like three strand rope or garden twine.

Flat weave, though, uses strands that are not twisted- they are just a bundle of strands side by side like fin rope, so they’ll kinda flatten out into ovals or almost rectangular shapes when they are woven. In fact, it’s probably got a little sizing on the yarns to keep it that way. You see ‘woven roving’ in the real heavy department of a glass cloth supply, and it looks like this:

That is really, really flat weave stuff - think in terms of a lath basket. The cross section of ithe yarns probably looks like a piece of tape. Lighter weight flat weave cloth would be more oval in cross section.

A cross section view

A handy fin repair trick, while I’m reminded of it. Lots of fiberglass boat builders will have scraps of woven roving, like above, and they’ll be happy if you take 'em away. Take them apart, yarn by yarn, and you got all the fin rope you’ll ever want. In handy sizes. The sizing ( think of it as something like starch ) keeps it together somewhat so ya don’t get those miserable furballs you sometimes get with fin rope.

The flat weave woven roving ( haven’t used lighter stuff) tends to be kinda prone to snagging tools, more than plain weave cloth, prolly 'cos the yarns ain’t twisted and instead are just lying there. Leastwise, that’s my experience.

hope that’s of use


the glassguru in my neighborhood…never heard him say “plain”/

he simply calls 'em “round” or “flat”, & your helpful illustration

shows why.


Not a glassing “guru” by any means here.

Used both weaves in the fairing business (road racers) and also glassing fiberglass boats that were damaged.

I found flatweave is compacted, and harder to saturate, stiffer, and harder to cut.

Regular weave being more 3D, accepts resin easier, bends over curves (rails of surfboards), and sticks, staying in place.

I’ve always liked S and E over K.

In the fairing business, guys who use flatweave just roll the resin on, compacting, and saturating with pressure.

Why don’t we glass with rollers?