Furling for twin turbine on a T

[SpmP]

Good Day all,

 I am building a wind turbine with a twin f&p genny set on the end of a spar to form a T - more power per tower

  BUT

I'me coming unstuck at the furling stage. In the interests of simplicity and reliability I would prefer to have a mechanical furling and wind tracking system . I.e a tail.

 Can I build a furling tail on a system where there is no offset.

 With two prop sets on the tower will the tail have to be huge to counter

   i) the swept radius

   ii) the angular momentum of turbines ~2m from the fulcrum?

I had invisaged using a simple active system with a small van in the centre on a bearing with a piece of metal only on one side, and the tracking done with two infra red switches mounted next to each other at a distance that would give some hysteresis. One normally o, the other normally off, such that as the van moved, one switch would either be covered or uncovered. I thought the 'move' signal could be put through an RC network to a PWM controller chip to ramp on and off the turning. With the turning dne by an electric window motor with its cable twisted about the tower so as to provide enough tension to move the gennies, but enough slack such that if a gust really does want to move the genny it still can.

  Does this sound like a good laternative to a passive system if that is impossible or impractical.

Thank you.

[windstuffnow]

  Why not simply stack them using a common pivot.  Both offset the same and a standard furling system would take care of both of them.  

  The T could be made to work with the correct offset as well, this might take some trial and error to get it right because of the rotating mass.  Stacking them would be the simplest way to a solution.

.  

[wdyasq]

A tilt back system might work also.

Ron

[spinningmagnets]

Perhaps mount the "T" on a turn-table that is faced to the wind by a rudder. Below the rudder is a drooping horizontal tail. As the wind speed increases, the drooping tail is lifted, and a linkage skews the "T" relative to the turn-table and the rudder.

Just an idea...

[thefinis]

Just out of idle curiosity why not mount two F & P gens on a single shaft and use one larger set of blades with furling? It may surprise you how little it takes in increased diameter to equal 2 smaller sets of blades.

Finis

[SpmP]

Thank you all for your comments,

 Over the past few days I have been trying to get to some conclusion as to what I will do.

 I am now certain that an active control sytem will be unreliable and energy hungry.

I already have the cross spar etc done, so thats sort of fixed, and the gennies are already two per shaft. So a twin double... its sort of neat, like a set of dumbells.

 I am very proud of the simplicity of construction, if you have a lathe, so if anyone is interested in the method I would be happy to share...

anyway, passive furling

 The traditional system would definitley be much trial and error. Although the offset can be added easily, I am worried about the weight in the tail that would be required to keep the tail down, whilst being able to turn the things in a normal wind (what the word for the reluctance of something to move, like inertia...).

 Just lots and lots of trial and error. Our experience so far with this furling method is that we dont have enough experience, and boy does the tail take a beating! SO help! anyone with alot of experience with furling tails, could you give me some intuative guesses based on ~2.5m diameter blade sets on either end of a 3m piece of 'cattle rail', with 4.5 - 6.5ms-1 being the average windspeed.

Hey, but I want to consider everything, especially the things I thought too unlikely  due to my lack of experience, liek tilting...

wdyasq do you have any simple examples of tilting systems that you could point me to? Or could you elaborate a bit as to whats involved. Sorry Ive never researched this as an option.

spinningmagnets, just and interesting idea , have you a working example or know of one... I am a little worried with this turbine, as I have to construct it at my current house. Pack up all my lovely tools, and moove into deepest darkest back country, with no power, phone, or ... ... SHED! So it needs to work fairly well before I get up there and test it. (help! ... <swallow>)