Blades 3.0 suggestions

[Ungrounded Lightning Rod]

Great idea using the engine hoist for hanging a carcass of whatever, too.

[SparWeb]

Dang - my deep-freezer is full of lamb, now.  I'll get ya next time.

Back to the blades - stain, varnish, or paint?
Why wait?  Is your shop heated now?  Seems to have some heat from that last post about the shop.
Control the moisture in the wood through the inevitable seasonal changes (heat and humidity) to prevent warping.

[bigrockcandymountain]

The blades are already painted with about 6 coats of glossy white paint.  Ya, I'll be putting this rotor up as soon as the snow melts.  We are finished the dark days of winter, so now i can afford to tweak the turbine a bit.  I like to leave it alone in the winter because it makes half of our power.

Im going to try 3 layers of the cheap leading edge tape that i have.  Ill put it on with the heat gun.  I got thinking about it and decided that i put the last stuff on after the blades were already worn.  It worked ok where it stuck, but peeled off the rough spots and they continued to wear.  I wanted to do a metal leading edge, but maybe on the next set. 

The shop is 2 degrees right now.  It was up to 7 degrees, so i left the big door open to get it cooled off for chilling the beef.  It will slowly creep back up from now on.  There is no heat, but with the super insulation and south windows, it heats itself quite effectively.

[kitestrings]

Those look great.  (And, steak sounds good too.)

I think the extra effort on balancing worth the effort.  We sweated this a bit more this last round, and I've noticed the difference.

We used 3M blade tape from place Spar recommended...aircraftspruce I think.  Seemed to be good stuff, and a roll is a lifetime supply.

The old Winco's used a thin copper flashing on the leading edge.  I always liked it, but couldn't figure out a method of attachment that I was happy with.

[Jason Wilkinson]

What I don't understand is why people still make tapered and twisted wooden blades which is a lot of work and uses a lot of wood.

can you provide a method where one can MAKE (untapered  straight blades  other than of wood ?
 we sure would love to have such a method

[SparWeb]

Hi Jason,
I won't knock the KISS principle.  Twist and taper just look better (IMO) and I have to look at my machine for a decade or more (the last blades lasted almost 10 years).  So they ought to look nice, shouldn't they?  Carving blades is also a relaxing task for me.  So why make it go so quickly that it's over too soon?

A simple hack on the twist and taper is to mount a straight blade with a wedge on the hub, giving the blade a 5 or 10 degree angle.  You can either cut the wedge into the root "grip" end, or just stack a separate wedge between the blade and the hub plate.

I've seen this done once or twice, and given its simplicity, I wonder why it's not done so often.

[bigrockcandymountain]

There was a guy selling aluminum extrusion blades that were straight.  They were goe 222 profile. 

You could easily hotwire some foam straight airfoil shaped and lay up glass or carbon fibre on it. 

I disagree that tapered wood blades use a lot of wood.  I just use a single 2x8 the length of the blades.  These were even cull lumber that i paid $4 per 16' board so my cost is $2 per blade. I also enjoy the carving stage, and being that blade carving is maybe 5% of the entire build process, it isn't worth saving time on in my opinion. 

Another reason to do tapered blades is for structural reasons.  They just end up way more sturdy where you need it and thin and aerodynamic where you don't need the extra weight.  And yes, they look great and my turbine is straight out my picture window and i spend a lot of time staring at it. 

The hill is a sheet of ice and the loader is cracked pretty bad that i use for laying down my tower, so it will be awhile yet before i get this unit up.

[kitestrings]

There are two that I recall.  One is a fellow named PhillM (fillm) on the back shed forum.  I think his site is called Oz Engineering, he offers (or did) AL extruded blades.  There also is an entity, IIRC, it is Royal.  Dave or DaveB?  He was selling CNC, non-tapered, goe222 profile blades I believe.  You could search for him here if interested.

Because most are building one set, and not replicating (except maybe every decade for so) the effort, there's probably little or no saving to garner.  I believe twisted blades, with a larger profile near the root, also start easier/sooner.

[bigrockcandymountain]

[ Specified attachment is not available ]
Shameless vanity picture of the new rotor ready to go up. 
The old blades are pretty worn.  They were still making power, but noisy and they never did balance like I wanted them to. 

[MattM]

Are you perhaps going to add foil tape where your blades have been wearing?  Dust particles will eventually chew throw aluminum-based foil tape, but at a very reduced rate.

[bigrockcandymountain]

MattM yes leading edge tape is definitely one of the upgrades this time.  You can see on the old ones what remains of the tape.  The problem is that I didn't apply it to the old blades until they were rough, and so it didn't stand up because it didn't have a smooth surface to stick to.  Hopefully this time it holds up better. 

The new blades are based on the GOE288 profile.  They have a slight dish in the windward face.  They are up there spinning now.  My goals for this upgrade were as follows in no particular order.

1. Better balance.
2. Better startup
3. More power
4. More durable
5. Quieter


The balance is definitely improved.  They balanced with only a small piece of steel instead of a 10 lb block like the last ones.  They also run WAY smoother.  The guy cables used to dance like crazy.  Now they are quite still.

The startup seems a bit better, but still not quite slightest breeze.  I'll have to observe a bit more but I'm happy anyway.

The power should be a bit higher since these are nice and smooth.  I also tightened up the furling a bit so it will almost definitely make more power.  I'm hoping for about 2kw in normal type winds.  It was about 1200w before.  I haven't watched long enough to tell but it looks promising.

As i said, i did a better job on the leading edge tape.  I also did a better job of paint on these.  Hopefully i can get 5 or more years out of them. 

They are definitely way quieter.  Still not silent, but definitely improved.  I did a very thin trailing edge following kitestrings advice.  I also did a pionted profile on the tips as opposed to flat.  Some of the noise is generator whine, so its hard to say how much noise the blades are making.  The better balance also helps the noise a lot.  In low winds the tail used to bang against it's stops and that was very annoying. 

Other things i did were just normal maintenance.  The bearings on the generator are greasable and have drain plugs.  So you pump grease in one side and the old grease pushes out the other.  I think of it like an oil change for the bearings.  They feel great with no roughness or play. 

I greased the main swivel and tail pivot, and the furling linkage. 

Hopefully it is good for awhile now.  The only thing I'm not 100% confident about is the rotor hub.  It isn't as beefy as the last one so hopefully it doesn't fly apart half way through the winter.

[SparWeb]

Looking real good!

Vanity pics:  Keep 'em coming!

[kitestrings]

Agreed.

Regarding the hub, it looks pretty solid to me, and you have the upwind plates tied together if I'm seeing this right; with welded gussets? Often the blade plates are independent (like ours) and the downwind rotor has to be stiff enough to absorb any flex from the rotor.

Jim Sencenbaugh, who designed turbines in the 70's-80's had a clever idea I thought.  He used the inner two blade plate holes (6-holes) to fasten a thin, hex-shaped plate that did two things: 1) tied the three blades together (taking some of the tensile forces), and 2) gave a means of securely attaching the nose cone.

Hopefully Jim will excuse my reuse of his photo (since I speak highly of him still):





Your new rotor looks great!  Good luck.

[kitestrings]

How are the new blades do far?

[bigrockcandymountain]

They are a bit different than i predicted, but also very good. 

The balance is the greatest improvement.  They hardly vibrate at all at any speed.  This helps the noise as well.  They are also way quieter.

As for more power, I'm not exactly sure.  They might have a bit more power in the slow speed range.  They start up well, and get to 500w very easily.  The top end power is still only about 1500w, and then they fully furl and in a gale, the power drops off to maybe 200w. The old ones never did that. The more wind there was, the more power they made up to 2kw at times.

I reversed the rotation on these, so I am thinking that is the difference. 

I'm thinking the thing to do is tighten the furling springs quit a bit more to delay furling.  It now acts exactly like i originally hoped.  It furls all at once.  I'll watch it for another few weeks, and then tighten them up to hopefully get to 2kw continuous. 

The manual furling cable system should last way longer now. It was mostly the imbalance that was causing it to move up and down a bit every rotation of the rotor.  That is gone, so likely 95% of the wear is gone too.

I've had it turned off for a few days, just to make sure it stays parked like the old one did without shorting the wires and it does. 

I guess to sum it up, it is incrementally improved in lots of ways.  The old one kept us in power no problem, so this one should be just a little bit better. 

That design on the Sencenbaugh is quite elegant.  Hopefully my hub is as solid as those were.  The outer plate is 1/8" steel with about 1-1/2" gussets tying it all together.

[DamonHD]

That is good to hear!

Rgds

Damon

[SparWeb]

If you're comfortable with the furling point it's at now, and you've watched it long enough to be comfortable it's really only operating in a full-on or full-furl mode, then it does sound like you can adjust the springs.  I don't know your winds, but the high winds that I COULD extract more power out of don't add up to enough energy to be worth the wear and tear.  If you're confident that your blades will last for years running true to winds up to 50-60 kph before furling, then there's no reason not to.  That protective tape should help.

One thing with incremental improvements (and I do the same) is that when anyone asks you "how many wind turbines have you built" the accurate answer is something like "two and a half".  You mentally add up the changes here and there and it's never a whole new machine all at once!

[kitestrings]

It sounds to me like you hit 4 1/2 of the 5 goals, and with a bit of tuning can probably get the production where you you're comfortable.  The balance and noise are big.

Jim got a lot of things right.  You'd be interested to know that he also had a manual furling cable that came up through the center of the tower, thru a swivel, then through a short section of metal-flex conduit that made a sweep-like transition around the generator.  This changed the pull direction from vertical to horizontal.  The cable connected to a bracket near the tail-hinge, and a hand-winch at the base.  The problem was that 1) the cable was too heavy (on a tall tower), and 2) the cable resistance was hard to get right.  If you didn't lube it, it could wear into the conduit.  If you lubed it, it was good for a while, but then got dirty & dry/sticky.  We ended up shortening the cable and raising the hand-winch up the tower.  So you had to climb, but were safely below the turbine.

Good luck with it all.

[bigrockcandymountain]

Quick update on these blades.  The controller logged 20kwh yesterday with a peak of 2300w.  The peak was at 120vdc which is way above my diversion load setpoint of 72vdc.  That means the real production was probably something like 3500w for a second or two counting the power that got diverted and not counted. 

It's going to be windy all week, so we should have lots of power. I can't help thinking how these blades could be better.

I think they are a design tsr4 or 5 or so.  They are also a very thick airfoil.  About 20% if i remember correctly.  They are designed to turn fairly slowly, but my generator only cuts in when they turn rather fast. 

At least tsr7 at 5m/s wind speed.  I could fix this by using the series Y connection, but then i would limit amperage to half of what they are now.  The nameplate says 8 amps. Rectified to dc that would be 13a which at 150vdc would give 1950w continuous.  That is higher than what i am seeing now for a top production.

I'm thinking at some point i will try this.  The way they are set up now, the mppt is mostly useless.  They would behave the same way directly connected to a battery. 

I'm not sure i will mess with it until spring.  We are in the season when we really depend on the turbine, so i don't want to mess with it when it is working fine.

[kitestrings]

Sorry, but you lost me on this one.  I think you figured that you'd recently peaked at 2,300 watts, plus your upstream diversion load, or about 3,500 watts.

Is the alternate wye config. on your diversion load?  I'm not following the 1950 being higher than your "top production".

Regardless, 20 kWh on a 13' rotor is awesome output; serious winds, huh?!

[bigrockcandymountain]

Ya, very steady wind the past couple days.  The forecast was 40 gusting 60 km and thats probably what it was.

Sorry about the confusion but thanks for pointing it out.  I normally see about 1200w max continuous right now.  Only the odd gust runs it up over 1500w, so 1950w would be ok for a continuous rating.  I guess I'm just chasing a bit higher efficiency at low wind speeds.

It is totally gut feeling with no data to back it up, but the first set of blades i carved were very flat pitch and thin airfoil, and i remember them making more power at low wind than what i am seeing now.

I could build another high tsr set of blades, but i would rather not. They were really loud and flimsy.  They flexed enough to hit the tower and grenade.

That's why I am contemplating the wiring change.  Maybe it's just the human condition or mental illness or something, but I never seenm to be 100% satisfied. 

[SparWeb]

...but I never seenm to be 100% satisfied.

Oh I thought that was just my bugbear.

Well, if you and I are both running mis-matched blades this winter, we can't complain too much.  While you're getting 20kWhr in a day, on the same day (since I'm just 300 km upwind of you) I got 10kWhr in one day with 10' blades, which by comparison of disc areas is a pretty similar.

Do you have anything measuring RPM?  We could nail down more certainly what TSR they're actually at.  Have you noticed in the charts I post that TSR varies with wind speed?  I bet yours does that, too.  So it may be TSR 7 at startup and drift down to TSR 4 in strong wind.  Or maybe something different - it depends on your blade/generator combination.

Does your generator have "all 12" wires coming out?   Put differently, can you configure the wiring for both star and delta, and series and parallel?  That many options may get you a closer match than just a simple half/double by connecting series-Y, if you can connect in Delta instead.  There is also "Jerry" rigging which I found works nicely, too, but needs another bridge rectifier.