On Fri, 4 Oct 2013 21:48:30 -0600, "Irv Finkleman"
wrote:

I wonder how much difference it would make if I were to
build a loading coil on a piece of 3''x3" wood?

Difference from what? What are you comparing the wood coil with?

It would be
very easy and I could suspend the winding above the wood
form with plastic dowel glued on each corner of the wood.
I could also make a similar coil using PVC pipe. Even in that
case the winding would have a somewhat rectangular form
factor.

Yep. Both PCV and wood are lossy. Put a piece in your microwave oven
and watch them both get warm. Actually, if the wood has a high
moisture content, it will get quite hot. If exposed, both materials
also have problems with UV resistance. If you must use plastic
tubing, you can possibly find something in polysulfone, polystyrene,
polypropylene, or polycarbonate (in order of preference). If you
can't find these, white ABS schedule 40 sorta works at low power
levels.

High power or low power? If low power, you could probably wind the
loading coal on kiln dried and sealed wood or PVC and it will work. On
the other foot, high power will heat anything that's lossy, including
the coil form.

High Q or low Q? If you need a really high Q loading coil, the
material losses might be a problem.

Hints:
http://www.w8ji.com/loading_inductors.htm
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm
Notice the preferred loading coil construction.

This might give you some ideas (good and bad):
https://www.google.com/search?tbm=isch&q=antenna+loading+coil

It wouldn't be air core considering that it would be over
wood (dry and waterproofed) or PVC pipe.

I do require the structure be relatively strong or I
would wind the coil, put epoxy glue strips along it
to make it like AirDux and the like.

Strong, relative to what? Are you supporting a tower on the coil, or
a length of wire? Some clues as to the weight load, and other
stresses (torque, shear, vibration, etc) would be helpful.

Any comments or suggestions??

Nope. You haven't stated what you're trying to accomplish or what you
have to work with.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558