I built the cylinders, Roger. If you look in my photo uploads there should be some photos of it in there on the bench, showing the internal parts.
It will easily work on a 17 (with the appropriate stroke and spring pressure). Jacobs has been using spring loaded tails on their machines for years, mainly to prevent damage to the boom assembly in side gusts, but also for initial furling before the prop governor starts feathering the blades. I just built a 13 with one on it that has 11" of stroke using Hillman #62 springs in it. I don't have that machine up yet - I'm working on building a tower for it.
The total tail travel on this one is 75°. My newer ones have 85° of movement. In the video it never got to fully furled. But when it does it turns the rotor at about 80-85° to the wind due to the tail itself running at approximately 10° to the wind direction.
I started working on this concept awhile back because I got tired of having the tail weigh a specific amount, and be limited on the length of the boom. This arrangement allows me to use whatever size (and weight) tail feather I want, and to fly a long tail boom that would otherwise not work with an angled hinge system.
Wind turbines work by having a higher pressure in front of the blades than they have in back. Without that pressure difference they wouldn't even run. Getting the tail further back, out of the wake turbulence and low pressure zone in back of the blades gives better steering control, keeps the rotor more accurately steered into variable winds and enhances total kWh output because the rotor maintains a more constant speed. Since I started doing this my ammeters no longer dance up and down the scale like they used to when I was restricted by the required design parameters of the old gravity tail.
On larger machines with gravity tails, builders go to great lengths to get the tail light enough to even work properly. With this, you don't have to worry about that.
The gravity/angled hinge tail is limited in what it can do. You don't see it on bigger machines, like the Jacobs, because things get too heavy and it won't stand up to the test of time and high winds. I'm just adapting what Jacobs has done to these smaller machines.
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Chris