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The common view is that in a strong wind, a F1B should be launched slightly to the right at a lower pitch angle. If the model is launched to the left and is pushed backwards by the wind, it’s VIT could trigger a loop. And if the model is launched too much to the right, the effect of a sudden wind burst hitting the model from it’s left is unpredictable.
Has anyone tried to launch his F1B between 135 to 225 to the wind, measured clockwise? (This is a 90 degree angle centered downwind). The model should be launched at a higher pitch angle and is unlikely to loop when the VIT kicks in.
Wind trim variants include dropping the stab’s trailing edge before the VIT to reduce the angle in which the VIT kicks in – effectively reducing the radius of the outside loop. Another is to get more energy upfront: by switching to fixed pitch front ends or reducing the low torque pitch on variable pitch front ends. Short motors with strong bursts and knees are always helpful.
This problem is more acute for F1Bs due to their strong burst and the VIT effect. Other rubber models conform to a more helical pattern from the beginning.
When I encounter such strong winds, I find the nearest beer-filled cooler and watch others sort these issues out.
After some thought it seems that the optimal launch bearing should be between 160 and 170 degrees to the wind. F1B models with a tighter climb pattern should be launched at a lower bearing to the wind, say 150-160 degrees. (My models do 2-2.5 revolutions per climb).
The model should be launched at a higher pitch than usual (by 5 or 10 degrees) as the wind will tend to push it’s nose down. To do this accurately – a (short) streamer should be set down wind.
The pitch variation of a variable prop should be set between the standard (calm weather) variable pitch and a fixed pitch prop (typically 29 degrees). The rational is that in a strong wind, a fixed pitch initially climbs quickly but has a slower cruise, while a standard variable pitch has a slow initial burst and knee but a faster cruise. So,if the standard pitch variation of a variable pitch front end is 8 degrees (between 33 and 25 degrees) then use a 4 degree cam (between 31 and 27 degrees). If it’s 12 degrees try 32 to 26. (Blank cams are available from the manufactures).
The combination of the two should, in my opinion, give a safe and a robust climb in the wind. However, I have not yet got the opportunity to actually try this combination myself. Have others conjured up or tried something similar?
@Bill Shailor wrote:
When I encounter such strong winds, I find the nearest beer-filled cooler and watch others sort these issues out.
I normally join Bill with a liter of Gatorade
I happen to have spoken to Igor Vivchar today and had raised the idea of reducing the front end’s pitch variation in very windy conditions (15+ MPH). Igor really did not like the idea and said that in windy conditions he switches to shorter motors. His long, medium and short motors correspond to 420, 400 and 380 turns respectively (you can back out the motor lengths).
Another point Igor made was that in windy conditions he also moves the CG forward, from the base 57%, by adding up to 7 grams in the nose. This requires augmenting the stab’s decalage by up to one and a half (screw) turns. (There are probably one or two intermediate steps).
This definitely sounds simpler than reducing the front end’s pitch variation. But a lower pitch variation might still be a good option under extreme windy conditions.
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