Q.Deer protection
Can I crimp a length of tin foil around my newly planted oak trees and fruit tree trunks to prevent deer rubs? I would crimp loosely enough to allow trunk growth. What about beaver, would tin foil prevent gnawing on my willows?

I did some research and these are ways that aluminum foil is used to repel deer:
1) used in conjunction with peanut butter on an electric fence
2) hung in strips from tree branches to sparkle and reflect light.
3) wrapped around the base of shrubs or saplings (foil should be at least waist high) - which is what you are proposing.
However, there are other methods of repelling deer, which might prove more effective and I have linked you to this information below:
Protecting Trees From Deer Rubs:
https://www.gardeningknowhow.com/plant-problems/pests/deer/deer-rubbing-tree-bark.htm
How To Protect Trees From Deer:
https://www.gardeningknowhow.com/plant-problems/pests/deer/how-to-protect-trees-from-deer.htm