Thomas Linton :
... have you mesured the difference in effort between cutting wood with a folding pruning saw (e.g., Fiskars) vs. a large knife
Yes, many times. Last year I brought along a couple of saws when I was cutting the winters wood and ran them against many blades including axes both felling and bucking trees. In regards to raw time and effort, on hard and dry wood, a quality pruning saw (you want it really coarse ~6 tpi) is several times to one more efficient than even a very large chopping blade both in regards to time, and especially for effort.
As the wood gets softer and especially sappier, the penetration of the blade goes way up and saws can starts to readily bind, and thus the gap narrows significantly. On clear white pine you can easily get 2+" of penetration (straight down) into a piece of 3" thick wood. This means that it is just seconds for a quality blade, and little to no effort, so the saw is of little benefit aside from being able to produce a clean cut.
Much also depends on how the wood is being cut. Yesterday I spent the day giving a hand to my brother hauling out ten truckloads oo wood. The truck he was using could not take heavy tail loads so much of the small wood in the pile had to be cut in half (the larger sticks were already short simply for practical ease of carry).
I had a large felling axe (5 star I reviewed awhile ago), a GB Wildlife hatchet, my Battle Mistress, and a timber saw [tashiro hardware]. The axe was inefficient on such felled wood. The wood had no ability to resist the impact of the axe and would just move and thus the penetration was relatively low. The Battle Mistress was much more efficient easily as good penetration with far less effort, but the blade length made it difficult to cut the wood of choice without hitting the other sticks in the pile unless time was spent moving the sticks over the edge, then holding them down and chopping away. The saw was also inefficient for the same reason. The hatchet was ideal and by far the best choice.
Now take the same task with slightly different conditions, use a sawhorse to cut the wood to lengths. The axe is now even more useless, the hatchet has no advantage over the knife regarding extra contacts, and the knife is generally more efficient on the lighter springer wood, the saw of course is now in its element and by far the most capable tool.
However take a look at felling such small wood, including the task of clearing away branches and other light vegetation. The axe is again far behind, the hatchet works well on the notching, but the blade is just as capable and much more so for removing the limbs and any introuding vegetation (we get a lot of Alders around here which grow like thick heavy vines). The saw does well on the under cut, but takes much more time to notch the wood and thus really wants a blade on wood of any size fo clear the notch, it is also far behind on limbs and light vegetation.
But, if the ground is very poor and the roots very unstable, then the tree may not be able to take heavy impacts as it will just move and absorb the energy. Get this kind of rooting on a hard tree and the blades and hatchets start to become very inefficient (more so for the hatchet). The saw is then by far the more efficient. When the wood gets very large, the long blade gets very unpractical and the hatchet puts ahead readily and the heavy felling axe takes over many times to one.
-Cliff
