Stinson Floatplane Technique
Getting your underpowered Stinson off the water!
Out of necessity, I've spent a great deal of time perfecting my take-off technique with our modestly powered 165 hp 108-2. As a novice, I tried desperately (and unsuccessfully) to force the plane onto the step. What experience has taught me, is to plan ahead, perfect your technique, and be patient! Under most conditions the aircraft will get on the step, and once on the step one seldom has a problem getting into the air. Here's a few points that may help you:
Note: I prefer lifting one float prior to reaching lift-off speed, but this should be avoided in rough water as it places undue stress on the float gear. Also, I immediately place the flap handle in the take-off setting once off the water, then slowly and fully retract the flaps, allowing the airspeed to build to 80 mph IAS prior to initiating a climb. One should resist the temptation to attempt a climb below 80 mph when heavily loaded. I've found the added drag of the floats will prevent the aircraft from adequately accelerating if a climb is prematurely initiated. This can have disastrous results if attempting to clear an obstruction. On the other hand, once the aircraft reaches 80, decent climb performance is assured, and can easily be maintained.
This is the formula used by EDO to determine the take-off time (TOT) for proposed aircraft float combinations. I've presented it here, to show the theoretical difference between the 108-2, 108-3, and larger hp versions of the same aircraft.
For the 108-2 165 hp fixed pitch, on 2425s
PI=2235/165 x sr of 2235/155 = 51.4359
TOT=1(2235/4850)^.3333 x (51.4359/25)^5 = 28.48 seconds
For the 108-3 165 hp fixed pitch, on 2425s
PI=2500/165 x sr of 2500/155 = 60.8499
TOT=1(2500/4850)^.3333 x (60.8499/25)^5 = 68.496 seconds
For the 108-2 180 hp fixed pitch, on 2425s
PI=2235/180 x sr of 2235/155 = 47.1496
TOT=1(2235/4850)^.3333 x (47.1496/25)^5 = 18.43 seconds
For the 108-3 210 hp c.s., on 2425s
PI=2500/210 x sr of 2500/155 = 47.8107
TOT=0.93(2500/4850)^.3333 x (47.8107/25)^5 = 19.08 seconds
For the 108-2 210 hp c.s., on 2425s
PI=2235/210 x sr of 2235/155 = 40.413936
TOT=0.93(2235/4850)^.3333 x (40.413936/25)^5 = 8.32 seconds.. wow!
For the 108-3 235 hp c.s., on 2870s
PI=2500/235 x sr of 2500/155 = 42.724432
TOT=0.93(2500/5740)^.3333 x (42.724432/25)^5 = 10.28 seconds
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