Dave Allyn wrote:

For information like this, there are better places for you to ask than
here. I suggest posting on the kayak building forum at kayakforum.com.

I am building a S&G canoe. I am going to use fiberglass cloth on the
entire outside for extra strength, and to prevent any checking in the
plywood. I'm useing 1/4" BCx plywood.

What weight of cloth would I want to use for this aplication? And the
next question, how would I decide that on future projects? Is there a
general rule of thumb for weight?

Most canoe and kayak builders use 6 oz. cloth, typically one layer over
the entire outside of the hull and often a second layer over just the
high wear "football" area on the bottom. Another common and lighter
alternative is 4 oz. cloth.

One last question, I know I need to tape the inside and outside with
fiberglass tape on the seams, but If I cover the whole outside with
cloth, do I still need the tape on the outside of the seams?

No it's not necessary, but extra wear protection on the chines is a good
idea. The outside should be completely glassed for durability. How much
glass/tape you use on the outside depends on how rugged you want the
boat to be.

What you need to do on the inside is to fillet the seams to provide a
smooth transition between the panels, then glass over the fillets. If
you do decide to fully glass the interior (not a bad idea), you can skip
the tape there, too. If you don't fully glass the interior, the rest of
the interior plywood surface should be covered with epoxy to seal it.

Once the boat is glassed, all surfaces that will be exposed to the sun
must be varnished or painted to provide UV protection. Otherwise,
sunlight will break down the epoxy over time.