These are approx. 4 times the size... So if I order:
10 lb bucket of resin
4 lbs of gelcoat
50 meters of mat ( http://tinyurl.com/aqe73 )
10 meters of cloth (http://tinyurl.com/bpbcy )
10 meters of cloth ( http://tinyurl.com/7mdyh )
+ an appropriate quantity of hardener and release for a pair

I think you will need more resin than that. While a circular horn will not
resonate as much as a flat sided one you will still need a fair amount of
mass when your low end is around 300hz.. Look at product # 1901541 on page
7 of the fabrics. That is the roving I was talking about to build up the
mass and strength. You probably won't need as much of the woven cloth
because that only goes on the inner and outer layers.

You only need a little MEK-P catalyst as you use only 5 -10 ml per liter of
resin.

The vacuum is to drive the airbubbles out of the cast ? I have a couple
of
vacuum pumps from scrapped vacuum bagging machines ( industrial models for
food products ) I might be able to make something usable from those..

What the vacuum does is uniformly press the laminations against the mold
producing the densest possible layup. If you have the pump you can jerry
rig almost everything else but the process takes a bit of practice. You may
not want to risk it for your first time. Polyester sets up in 15 -30
minutes depending on the temperature, amount of MEK-P and the mass of the
layup so you don't have a lot of time to get the bag on. You can read some
basics of it on my web site in the Hull section.

If you want to try it get some 4 to 6 mil clear poly builders film for the
bag and seal it with vacuum tape. prod # 3901701 on page 2 of the vacuum
technology page. You will also need a breather mat prod# 3901801 on page.3
and a peel ply like 3901851. Alternately you can use nylon flag bunting or
taffeta for the peel ply. You can usually find that on the remnant counter
at a fabric store.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com