I've owned 4 Taylorcrafts, that probably makes me somewhat of an educated person on the type. Others are far more advanced than I. However, I feel safe saying:
The T-craft is a great choice for time building and skill building. You will not find one good pilot who regretted their time in the T-craft or what the old girl taught them.
There is a wood bar sewn into the front of the seat sling, that can be un-bolted from the fuselage and then un-rolled to let the sling drop down an inch or two. Or rolled up a little tighter for a shorter pilot.
Putting the skylight mod into the Taylorcraft is well worthwhile. You get an inch or two more headroom, and a huge huge increase in visibility. The skylight turns it into a whole new airplane.
The F series Taylorcraft gives up some of the light, balanced, "sportscar" handling of the B series, because of the longer engine mount. A heavier engine further forward, balanced by the battery behind the baggage compartment. More mass inertia around the CG in the pitch axis. In return, you get a much larger baggage compartment and a significant increase in power. The F series are a little heavier, which takes out a little bit of the "floaty-ness" of the older airplanes.
The F-21 has room for two big people. Two fairly big dogs can fit in the baggage compartment. My buddy Jim Brewer in Anchorage flies the F-21 with his dogs all the time. I'm guessing your mountain bikes can fit if you remove the front wheels, but I have not measured this. But no, it is definitely, absolutely, unequivocably NOT a Cessna size cabin.
The T-craft is an utterly standard, normal, typical steel tube airplane. Once you get past the Mustang vs. Caamaro personality yelling, cursing, and insulting references, the truth is that any Cub or Champ or Stinson or Stearman mechanic can work on one just fine.
There are parts that you cannot buy new anymore. But all of these parts can be repaired using 43.13 methods and practices. If the lower engine cowling is missing, that will be more of a problem, because I believe the F-21 cowls were still stamped with a curve in them. If I'm remembering right, the F-22 airplanes used flat wrapped lower cowlings that were less attractive but just flat aluminum. But the tail surfaces, controls, landing gears... it's all just steel tube and sheet metal stuff like any other fabric taildragger.
Univair and Aircraft Spruce carry the nose cowlings I believe. Those are stamped also.
The F-21 or any 85+ horsepower T-craft will make a wonderful little light-to-medium duty back country airplane. The VG's will make a worthwhile difference, mostly in low-speed control. You will go faster and further on the same power and fuel in a T-craft than the equivalent Cub, because the basic airframe is cleaner. More miles per gallon.
Once you have figured out how to use the forward slip maneuver correctly, in calm air, flying into flat unobstructed strips, the T-craft can operate from almost, but not quite, as short of a strip as an un-flapped J-3 or PA-11 Cub. However, an un-flapped T-craft cannot match the STOL ability of a flapped Cub. A flapped T-craft (F-22) can get really close on the same power, but there were only a handful of flapped F-22's built.
The place where the T-craft starts to fall short in STOL flying is when you are flying into short strips with obstacles and/or gusty winds. Throwing the T-craft into and out of forward slips every two seconds to match rapidly changing gusts is difficult , and the T-craft airframe is too clean for really serious work in these conditions, dropping in over treelines, etc. This is the main reason that Cubs are preferred by working bush pilots.
For your use, however... as a time builder, skill-sharpener, and a recreational back country airplane where you are not forced to fly into 99th percentile extreme conditions for business... the F-21 is an exceptional value. There is a thriving, educated community of Taylorcraft owners and pilots who are eager to help and mentor you. And they're quite a bit less surly and prickly as some other bushplane type clubs I've run into.
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