Wood is good until .....

[Dave B]

  I know what happened here and I'll wait for some posted replies on your opinions on these 3 photos before I post an explanation. If anyone has thoughts I think it will be interesting reading of your ideas. If you would rather email me that's fine at   bruggelog(at)netsync(dot)net   My 16' turbine here is listed in the classifieds if you want a full description of the machine. It's price just dropped $400.00.   Dave B.

 

[ChrisOlson]

Ok, I give up Dave.  What happened to it?
--
Chris

[boB]

Looks like a damn bird got in the way of the blade.

Big bird.

[tecker]

looks like the trailing edge let go

[Harold in CR]

 Looks like all the trailing edges are broken. Harmonics from runaway ?

 We had a 2 bladed 4 KW machine that didn't furl, go runaway and pieces of the blade were scattered up to 200 ' from the tower.

[ChrisOlson]

Well, I'll throw my guess in the pool then.  The manual furling cable got hung up when it furled and the weight didn't keep the cable taught.  So one or more blades clipped the manual furling dangulator chain.
--
Chris

[midwoud1]

High wind. Wagling tail.  Tail hit propeller.

- Frans -

[Flux]

I am with Chris on this one, I suspect a loop of cable. If not the effect is the same.

Flux

[kitestrings]

Nice to hear from you Dave.  Wish it were to share better news.

My thoughts - I would have expected to see damage on the leading edge if it hit something.  I had one strike a poorly located juntion box once, when the blades flexed into it.  It was pretty clear what happened.   This looks to me to be more a stress fracture (I sound like a doctor here) - just too much flex in a high wind event?  Glue failure along a laminate?

Anxiously waiting...

~ks

[ChrisOlson]

My thoughts - I would have expected to see damage on the leading edge if it hit something.

Not when something comes up behind and hits it - it will get the trailing edge of the blade.  The reason I came up with my guess is that it looks like in the second photo I can see some damage on the trailing edge of the blade at the 2 o'clock position as well.  That looks to me like something that was moveable got hit by the first blade, which knocked it out of the way a bit before the second blade clipped it.

I've seen closeups of that turbine when Dave had it in the shop and he's got a heavy duty stop on the tail with a hydraulic damper, so I can't see how the tail would come around that far and clip a blade or two without having something bent on the tail assy.

The manual furling mechanism, to me, is highly suspect because if the drop cable freezes in the guide so the weight can't keep it taught you have a dangling length of chain up there when the tail goes to the fully furled position that could swing over into the prop arc and get hit.

I have pretty much the same manual furling mechanism on my geared 3.75 meter machines with the same blades.  I had to put an extra guide (consisting of a coil spring that takes up the slack) on the manual pull cable because I found the weight didn't always keep the cable taught and the blades clipped it a few times.  One one of my turbines it knocked one of the laminations loose on the trailing edge once but didn't break it.  I was able to repair the blade, and then modified them with the anti-slack spring so that wouldn't happen again.
--
Chris

[Dave B]

  Well, here's the deal. I've had dramatic crashes before but this was not one. I was in the house in the evening and we had nice winds at 15-20 mph things were fine until I started hearing a buzzing that sang a tune in pitch up and down. I was positive I knew what it was and thought it was a a floor broom I have resting on the solar thermal panel racks right against the house. Sounded exactly like it was spinning, it's done it before. It got louder so I went out to move it. It was obvious the noise was from the turbine.

  No big drama, the trailing edge lamination(s) of the one blade had pulled apart (no blade strike of anything ) and the blade was like a reed in a harmonica, singing happy in volume and pitch with the wind but it got ugly fast. By the time I got back inside to shut it down the blade tore apart and the trailing blade (2:00) caught the debris and ripped off the trailing lamination of that blade as well. Things got a bit flung around for a very short time while I shut it down and the furling cable got into the mix a bit then as well. No overspeed, no tower crash, no fire. I think just plain stress over time finally did them in.  It will be interesing to see everything up close when I get this back down and find some pieces, maybe. That may be a while but I'll report back on it then as well.

  Wind is fun and very little drama in solar, I'm liking less drama all the time.

  Thanks for the feed back.  Dave B.

[kitestrings]

Dang, I should'a bet someone some beer on this one.

Dave, what type of wood is it, and long've they been up?  I remember you posting on it...can't be more than two years ago, or we're they maybe used on your earlier water heating unit(s)?

~ks

[birdhouse]

i'd be curious to know what type of glue was used in the laminations! 

[kitestrings]

Dave,

I realized, after the fact, that my 'beer' crack was entirely too casual, given the situation and the work ahead. Don't know what I was thinking.  Wasn't. My apologies.

Hopefully it's repairable?

~ks

[Dave B]

 I've run 3 different sets of blades on my 2 different turbines. My first were my own I carved 12' and these were on a laminate single rotor machine I built and heated water with. These blades were of the twist. taper type and had a large drop at the root. They ran very fast and I eventually burned up 2 stators with that machine and it went into mothballs and was parted out.

  Modified versions of my dual rotor machine here have been flying for about 7 years. The first set of Got 222 blades were 18' and Poplar wood. These were too flexible and crashed the tower in high winds during yaw. I don't know for certain the manufacture of the glue for the blades at that time.  I have learned much about the 222 profile, furling, loading etc. for use with the standard type dual rotor axial alternator. They can run like a bat but do not be discouraged if you bolt them onto a standard book version dual rotor and then have to work with it to get decent performance and control. That's no fault of the blades but just confirms the fact that a wind turbine system is just that - a system of components that all need to work together.

  This second set of Got 222 blades were Ash wood, heavier than Poplar and stiffer besides. I also cut these down to 16', rotation direction was counter clockwise, I tweaked the furling several times, weight, angles etc. and designed my own load controller. Part of my design way back then is what they are now calling a clipper circuit.

  I have other plans for wind and that is why this machine is listed in the classifieds. $400.00 less now and I will be taking it down when the weather breaks or any time before if a purchase is made. This machine is not your ordinary book version axial.

  I have broad shoulders and not shy about working. Any comments are welcome. Back in the day this forum was filled with projects, photos, successes, failures and we all learned from it and looked forward to those stories. Things have changed some I guess, maybe that's progress.

  Thanks for all the comments.  Dave B.

[gww]

dave
If i would have took more pictures I could still fill this site with some projects and many great crashes and if my stuff was looked at closely,  probly more crashes to come.
Thanks for posting
gww

[Royalwdg]

DaveB How could the second blade get it's trailing edge ripped off from flying debris from the first blade. There is no apparent leading edge damage.  You know as well anyone how fast a tail wagger will come around in a hard wind. The flexing of both the tail structure in a sideways direction and flexing of the blades when it all comes to the stop can be much more than expected.  The arched back side of these blades will put the point of contact near the middle of the blade.  Tail strike?  Very possible.  More likely it was a tower strike.  Same point of impact on the blade.  You have had tower stikes before.  The tail waggers' constant turning away from the wind, as they are designed to do, keeps the blades traveling through a warped disc similar to a taco.  That is one of the big reasons that I got away from that design.  I live near DaveB and a week before his discovery we had 60 plus winds.  I t is very possible that the blades received some damage then and the next windy day finally came apart to be noticed.  A mutual aquaintence of ours also had a tower strike that with blades that looked exactly like these.  When he first noticed them he called me and let me know that he thought he had a delamination issue.  He came to see me to order another set of blades and gave me one of his damaged blades. No laminations coming apart. Just torn apart wood. Not many blades will survive hard strikes like this no matter what the material.  Dave Moller

[ChrisOlson]

I'm convinced, from what I can see in the photos, that the blades contacted something at the rear of the blade.  You don't get trailing edge damage on two blades from debris off one.  The one blade took the brunt of whatever was contacted and that deflects the blade circle so the next blade coming around doesn't hit as hard.

Seen it so many times it's classic - especially with Jacobs 23-10 turbines with the small 1.25" governor.
--
Chris

[Dave B]

  Stress and time finally took it's toll on these wooden blades and they delaminated. No fault of the blades just Mother Nature wearing things out  They were very good while they lasted and went down singing, we should all be so lucky.

 Dave B.

 

[clockmanFRA]

Blades only 5 years old. ?

Holy Smoke. !