Here is a simple and affordable curing platen that I use for I Beam Construction Out Of Autoclave
The inside blocks are aluminum as well to translate heat to center beam. Just vacuum bag the sides and drape the unit in a heavy 1597 woven glass cloth.
Using autoclave material usually gives you surface porosity but minimal as the ramp rate, due to the mass, is slow.
Thanks in Advance
"Plan your work and work your plan"
Composite Tech Spec II
Gulfstream Structural Test
912-395-0197 RDC Lab
Being that you are only curing a part 24" long one can make a chicken wire "BOX" inside and out and use 2" thick industrial stone wool for insulation Use heat guns for your heat source but make sure you vent out for circulation and deflect the direct heat of the part because if you don't than you will get hot spots
It gets hot so not put it on a table top use it only on a cement floor!!!!!!