I have read some talk from time to time about gluing one arrow inside of another to come up with a stiffer spine for heavy draw bows. Does anyone have any info on these arrows. Like which sizes to use?
Tink Nathan wrote about putting wood shafts in aluminum, for his Africa hunts.
That was in the '70s.
Might Google his name for info.
It depends on overall arrow weight and spine required. You can do anything from GT35/55 carbon inside of a 2219 to a 2117/1916 aluminum combo or even a 2419 over a 2216 or 2219. For maximum spine a GT75/95 with a 2216 over the top should cover the heaviest bow you can draw.
Just remember that aluminum/aluminum composites are easier to tune by point weight that carbon/aluminum composites that require more tuning by length rather than point weight.
I think it has mostly done for heavy arrows on dangerous game.You can figure how much spine you need and find two shafts that equal that spine,as a starting point.I would have thought that today,there would be heavy enough carbons to cover it but haven't had the need to research it,myself.
Forgot to say,you might pose the question on the Dangerous Game forum and may reach someone with actual experience building them.