Couldn’t you just buy two rolls of 1" tape and be done with the whole thing?
Sorry… Just being a wise acre!
In reality, say you did want to work with a 30’ long item. You’d need to have an in feed support and an out feed support. Ideally they should be 30’ each and the width of the 20 inch wide cut area of the glow forge. They also need to have a “fence” to help align and keep the item straight.
[ bed for item_____| < fence ]
Align the item to the Glow Forge first.
Start by running the 30’ item half way thru the Glow Forge ( “GF” )
Use a large carpenters square to check and adjust the “GF” to the item if necessary.
Disengage the “GF” feed mechanism from the item to adjust for squareness.
Now re-engage the “GF” feed mechanism.
Align the in feed and out feed supports to the item. BY DOING THE FOLLOWING ! ! !
***USE 1/2" Spacers to keep BOTH supports fences 1/2" AWAY from the item.
Lock the supports down so they do not move.
“Feed” the item “in to the “GF” 10’. Measure the distance the far corner of the item is away from the fence. Ideally, it should be 1/2” !
Reverse the “GF” and move the item 20’ back. ( that brings it back to the midway point AND 10’ more!)
Measure the distance the NEAR corner of the item is away from the fence. Ideally, it should be 1/2" !
Run it back and forth a few times, taking measurements and see if they differ or are the same. If they are the same, then the “repeatability” is excellent. Not likely though, since the item is probably moved by friction rollers and the friction of the item on the tables can also affect movements!
If they are off by the same amount, one (+) and the other (-), then the support tables need to be adjusted by half of the measured distances and in the OPPOSITE directions.
In the aircraft industry, a 100’ wing-skin is held down by vacuum and the cutter is on a rack and pinion gantry and the alignments are checked with a laser!
Let me know how that works!
Worst case scenario is you’ll have extra material for your wood shop!