I'm working on a campaign where a giant forest covers the land where oceans should usually be. My party is going to have a vessel akin to a ship that will let them travel across this massive forest.
There are 3 forms of transport:
a ship that uses mechanical legs to walk on top of the canopy. Rust would impede speed. Built for safe travel and transversing difficult terrain.
A ship that has a giant keel that skims the top of the canopy. Pretty much a giant sailboat but out of water. Control Wind and Control Weather would increase the average speed. It's not meant for transporting people more than cargo.
A ship that has hot air balloons connected to different parts of the ship to keep it above the canopy. Gas/Magic powered fuel. Medium/Slow speed. Used to travel across forests as well as land. Can carry cargo but more fuel will be consumed the heavier the cargo and the more weight the slower it will be.
I have never homebrewed a form of transportation or vehicle before and I have no idea how travel speed on a vessel of this sort would work because it's technically not a boat and more akin to a walking/floating cargo ship.
Factors like the weather would probably impede speed of these vehicles: things like tornados, strong winds, and thunderstorms. Vessels like these aren't affected in the same way as real ships are so I'm unsure of the speed of these vehicles. In addition to this, the weight of the cargo could slow down or speed up the ship depending on depending on if the load is removed or gained. I'm not sure how ships work so I'm not sure that the weight might even matter but if it did it would impact the speed of the vessel.
To sum all of this up into a sentence: How would I create accurate travel speeds for homebrewed vehicles?
I kinda figured out the general speed, like if the ship was slow or fast or in between, but I'm not sure what the average speed would be per hour or week or day.