looking for advice for a 12' homebrew on a 93' tower

[windme]

Turbine will be 93 feet high, using 8" 12 gauge tubing.
Side guy wire distance can only be 35' do to a lake on one side and a small downgrade on the other.
I realize this distance is a bit short, so does anyone have any comments on what is the most cost effective way of making sure the anchors will be strong enough to handle the load?

[ChrisOlson]

Lots of concrete.
--
Chris

[windme]

oh great your my hero!   

[artv]

Hi windme,......"8" 12 guage" ,I don't think it is possible, maybe fly a flag but not a wind generator. If you do I hope it is out in the middel of nowhere...don't take my word for it, I'm not an engineer..........the max you could go up the tower (for guy wires to do any good would be maybe 40 feet)......that would still leave ~50 feet free standing ........... but like I said I'm not an engineer ..........personally I wouldn't trust it.........artv

[windme]

Maybe I stated that wrong the tower is made of 8” OD X .109 WA steel tubing. The tower itself is designed by Dan B
I'm just don't know exactly how wide or deep I need to concrete for the anchor since I only have 35 feet form the base of the tower to where the anchor will be. Not even sure what angle that will work out to be. Math has never been my strong point.
The fourth guy wire up will be at approx 85 feet high.
thank you, any other thoughts?  

[SparWeb]

Math is my strong suit, and I think you're taking a risk.
What is so unmovable and so close to the proposed base of the tower that you cannot space out the anchors?
Is it of such value that you can risk damaging it?  How will you work and build with such tight constraints?
Why is there room to tilt down the 90 foot tall tower but no room to fit a 90 foot guy-anchor stance?
Anyway, the stresses on the tower compound very rapidly when the angles get so steep.
The measures required to make up for these stresses make all materials heavier and more expensive.

You should consider a completely free-standing tower instead.  It costs more but you will spend a lot of money to make that 90' tilt-over tower safe anyway.

There are free-standing tower that can be tilted down, too.  Look up Venterra for an example.

[windme]

Thank you sir, what should the 90ft tower stance be?
the gin pole is going to be 50 feet long.
How many feet should the anchors on the sides be away from the base?

Update just went back outside and if I move the tower back to a new spot I can get 45 feet from the base to the anchor
Is that putting me back into a safer range?

[ChrisOlson]

oh great your my hero!   

Well, that's cool because my grandson says that too.   

But I'm not kiddin' ya'.  When you got the guy anchors that close you're looking at close to the foundation specs for a free standing tower.  Which means a lot of concrete.  I have built several 72 foot free-standing towers and they have a 8 foot stance at the base and the foundation has 20,000 lbs of concrete in it.
--
Chris

[Seekscore]

I had my tower certified by an engineer. 12ft turbine.

My tower is the same size tubing and 65ft tall. 20ft Gin Pole. My guy wires are 20 foot from the tower in footings 10ft deep, 2ft round, 5/8" anchors buried 4ft. I'm using 5/16 cable. Center footing is 24x24x36 deep. 4000# concrete with fiber. Almost 6 yards of concrete. I'm using two sets of guy wires.

Mike

[B529]

Thank you sir, what should the 90ft tower stance be?
the gin pole is going to be 50 feet long.
How many feet should the anchors on the sides be away from the base?

Update just went back outside and if I move the tower back to a new spot I can get 45 feet from the base to the anchor
Is that putting me back into a safer range?

That's putting you in a safer range. A 45' gin pole is big, would take a hard look at the load put on the gin pole.

Is a guyed latticed out of the question?

[DanB]

This board gets me in trouble sometimes 

towers are troublesome, especially those that tilt up and the opinions out there are all over the place.

8" diameter 12 gauge tubing is very rigid stuff and very much up to the job of supporting a 12' wind turbine if properly guyed.  (6" would do it fine too so there is some safety factor here)

a 45' gin pole, for a 90' tower is reasonable, and the longer the gin pole is... the less the forces are actually.

I've seen towers of this type with as little as a 20% guy radius (they require large anchors) - here we started out talking about perhaps 35% and now it looks like he can do almost 50%.  It'll be fine I expect.  I might be a 'hillbillie' ;-) - this tower is almost the same as mine (mine is from 10" tubing but has a 20' turbine perched on it, it's very rigid)  (we beat 100mph winds up here last week with the machine running... everything is fine)

We've put a few 12' machines on 6" tubing and they've been fine (they are also very rigid)
I've seen some very heavy proven 12' turbines perched on 4.5" sched 40 pipe.. some of those towers failed.

This place is a great forum to share information but sometimes the 'misinformation' and 'bad ideas' I see put as 'facts' scare me....

[SparWeb]

This board gets me in trouble sometimes 

...While some of us go looking for trouble!

towers are troublesome, especially those that tilt up and the opinions out there are all over the place.
8" diameter 12 gauge tubing is very rigid stuff and very much up to the job of supporting a 12' wind turbine if properly guyed.  (6" would do it fine too so there is some safety factor here)
a 45' gin pole, for a 90' tower is reasonable, and the longer the gin pole is... the less the forces are actually.
I've seen towers of this type with as little as a 20% guy radius (they require large anchors) - here we started out talking about perhaps 35% and now it looks like he can do almost 50%.  It'll be fine I expect.  I might be a 'hillbillie' ;-) - this tower is almost the same as mine (mine is from 10" tubing but has a 20' turbine perched on it, it's very rigid)  (we beat 100mph winds up here last week with the machine running... everything is fine)
We've put a few 12' machines on 6" tubing and they've been fine (they are also very rigid)
I've seen some very heavy proven 12' turbines perched on 4.5" sched 40 pipe.. some of those towers failed.
This place is a great forum to share information but sometimes the 'misinformation' and 'bad ideas' I see put as 'facts' scare me....

I can't help but look at towers, now that I'm addicted to this wind energy stuff.  What I usually check first is the apparent ratio of height to guy radius.  Plenty around here are 1:1, some are 50%.  That's enough to tell me that the pro's aren't comfortable with a radius less than 50% of the tower height.  The guy radius on mine is about 50%, too.  I wouldn't debate anyone on it: increasing the weight of the anchors and the size of the wires makes up for the difference when necessary.  I guess if I was going to strike a tone, I want to start with one of caution, at least until there is more information.  It's a balancing act.

[halfcrazy]

We have a 4 inch tower 85ft tall with a 50% guy radius local to me with a 17ft machine on it. I would prefer bigger pipe or more guy radius. My 10ft machine is on a 80 ft tower with a 50% guy radius the tower is 3 inch and that one is solid as a rock. My 100ft radio tower has 3 guy points instead of 4 and that is guyed at 95%.

If i where designing a tower today for a large machine i would go for larger diameter tubing like Dan I would be tempted to open up my guy radius as well but I guess it is not needed with a strong tower.

[DanB]

I can't help but look at towers, now that I'm addicted to this wind energy stuff.  What I usually check first is the apparent ratio of height to guy radius.  Plenty around here are 1:1, some are 50%.  That's enough to tell me that the pro's aren't comfortable with a radius less than 50% of the tower height.  The guy radius on mine is about 50%, too.  I wouldn't debate anyone on it: increasing the weight of the anchors and the size of the wires makes up for the difference when necessary.  I guess if I was going to strike a tone, I want to start with one of caution, at least until there is more information.  It's a balancing act.

Hi Spar.  I agree with you a large degree.  I guess I'd just argue that perhaps 50% is not only safe as you say - but also done for economic reasons.  It get's exponentially more expensive as the foot print gets smaller.  I do think we have to be *very cautious* however some folks have to work with what they have.  If it means a smaller foot print, then cables must be heavier... anchors larger etc.   Hopefully, that stuff has been accounted for in this case (I did consider it).

Mick Sagrillo has a 80' tilt up on his place, the guy radius is 25%.  It's built with that in mind though, and it works fine with heavier machines than this perched on it.

With all things, I guess we have to weigh caution against actually getting it done with the resources available.  To be completely safe... we should probably never do anything at all.  In this case, I think the tower is going to be overbuilt for the job.  Just my opinion though, based on a bit of figuring I've done and past experience with similar tilt up towers.

I guess I am just re-wording and hopefully agreeing with what you've already said.

[Ungrounded Lightning Rod]

It get's exponentially more expensive as the foot print gets smaller.

Inverse linear, actually.  (Approaches infinite as the footprint approaches zero.)

Cut the footprint in half, double the weight of the anchor and strength of the guy cables.  (And the excess is added to the downward load on the mast, too.)

[imsmooth]

I've done a lot of static engineering calculations when I made my tower.  The tension forces get amazingly high if the guy distance is to close to the tower.  I would not go any lower than 45% base to height ratio.  It would be a shame to see the whole thing come tumbling down in some bad winds.

[SparWeb]

Dan, that's what I thought, too.  Given the same set of facts, two people will see things differently based on their own experience.  Mentioning Mick Sagrillo's design sure made me sit up straight and pay attention!

[B529]

Mick Sagrillo has a 80' tilt up on his place, the guy radius is 25%.  It's built with that in mind though, and it works fine with heavier machines than this perched on it.

One of Robert's towers built for a ARE turbine?

I have to say seeing that short of radius in person looks scary, apparently it works. Guessing Robert designed it based on the use of a short gin pole for manageability and size of the pipe not so much space? A 45' or longer gin pole has to get a little wild to deal with.

[DanB]

Dan, that's what I thought, too.  Given the same set of facts, two people will see things differently based on their own experience.  Mentioning Mick Sagrillo's design sure made me sit up straight and pay attention!

I believe Micks is a Lake Michigan Wind and Sun tower of his design - probably suitable for 12' machines or less.

I don't believe he is a fan of the short radius, just that on that particular site - he had no more space (inbetween a building and a property line).  So the anchors and cables are appropriately designed.

Ungrounded...  yes, thank you for correcting me earlier.