I have a 10" Dob made of sturdy Sonotube.  I'm about to install a
cooling fan, which requires me to drill a 3" diameter hole.

While I'm not worried about the aesthetics, I wonder if having this
hole in the tube might weaken it.  I'm thinking "no" since 3" is only
a small fraction of the 31" circumference, but I thought I'd check
anyway and get the prevailing opinion.

Dave

Once you have made the hole, you might soak the edge with a super glue made
to work on paper/wood,etc.

--
2,500,000 tons of steel, spining all alone
in the Dark ... The Place is Babylon 5

SIAR
www.starlords.org

Akumaizer Cattery
http://akumaizer.united.net.kg

Yes, you do get a little bit of reduction of the strength of the tube but
the tube is so far over the needed strength that the end result will be
negligable.  Go forward and have fun!

--
Bob May
Imagine the terrorist's fun when they realize that their 72 "nubile {*filter*}s"
are all {*filter*}s and cranky from it being that time of the month!