Blades from scratch for the AWP

[oztule s]

I thought some may be interested in some more chainsaw fun.

The AWP decided the high winds were a bit too much, and decided to shed it's fibreglass blades... they shattered into fiberglass shards.. it must be the last thing to replace in this mill and it's electronics I think.

The blades broke off, and we decided to make some decent wooden blades and be done with it. We were pretty leisurely about it, as he had a twin lister diesel to supplement the power for the duration the mill was out of commission, and a KW of solar......so we threatened to do something real soon.... but didn't.... Murphy was to have none of that.

After a few days of diesel power and sunlight, the Lister's sump filled up with diesel, and the sun stopped shining.... and the forecast was for bleak and overcast for days to come....suddenly all three power sources were down for the count... something had to be done... and sooner rather than later.

So we selected a decent sized Macracarpa log which looks like this:

We hacked into it with Jamies 28" chainsaw and fashioned some very very rough planks,and lots of offcuts too:

You can see an offcut slab left behind as well as these offcuts:

Unfortunately I didn't take pics of the manufacture of the 10" X 2" planks . We cut squared up and true planks from the the slabs using the chainsaw jig method,.... that method can be found here: http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=1194&PN=2]    and then using the same jig method with a few of Danb's angles we cut the blades out.

As it turned out we were in a hurry to get some power flowing at his place, so the camera was the last thing to remember....Usually he has too much power, ...but suddenly everything was out and we didn't want the Batteries to suffer too much.

So it didn't take long to have the mill flying again. I went back up there today to take pics of them, So now we have fixed the injector pump on the Lister, and built , balanced and installed the blades...... of course the sun is shining brilliantly and the solar is putting out 1KW  instead of a few hundered watts, the mill steadily putting out  another KW. or more..... and the dump load working overtime again...... sigh.... it never rains but it pours.

 []

(and more happy neighbours too)

...............oztules

Note. I had to create another account to post pictures, I just couldn't face the nightmare of all those jumbled files again....

[wdyasq]

They say short term memory is the second thing to go .... still trying to remember the first....

Good job ..

Ron

[tecker]

 Necessity is the mother of motivation or is it just a mother . Well played hole anyhow I like the rip jig rip cuts are a mother for sure . Those are a little easier with a rip chain.

[oztules]

Yes Tecker, a saw mill would have been preferable, but you only got what you got at the time soo....there you go.

We did refashion the saw blades with the trusty file to a more  represent what we thought were ripping teeth. We made them nearly square... mistakenly or otherwise, they worked well.

Cutting 25 or so inches thick of timber along the grain.. it's not so simple to get the rough slabs, but the jig later trued them up without a problem. (plenty of swath though)

.........oztules

[Ungrounded Lightning Rod]

Now that the sun is out and the lister popping away merrily again, why not pull the mill down and paint the blades so they'll last?

That will give you an opportunity to do any cleanups/tweaks to the blade shape that you skipped in your rush to get the mill up.  Also to give us pix of the final product - before and after any tweaks and the paint job.

[domwild]

Oz,

Well done, once again! I wished I could manufacture wooden blades as easily and quickly as you can! Am still stuck with PVC blades, the top end of my skills.

[oztules]

Hi ULR,

The blades got a few coats of hot linseed oil,... second coat still damp on the way up.. so they do have some protection.

The mill will be coming down again to re-adjust the furling. We deliberately made the tail significantly lighter as we didn't know how or if it would furl with the different blades.

As it turns out, fully furled it does 25A@57v. In high winds (like we have today), it seems to be doing better than the original in the fully furled position.

In the intermediate winds, they do about the same, and in the light winds, about the same. In the light to middle, ehay try and furl in the small gusts,so we have made it furl far too early and it hunts about the place in the lighter- mid winds. So it needs a little more weight, and then it will probably out do the glass blades... which is a curious thing.

The AWP blades have a very heavily sculptured root area, and you would need 6" thick timber to follow it. we went for strength but with only 45mm thickness at the root, and barely an airfoil for the first 30%, after that we were more careful, and the last .....more so.

Tweaks.... we didn't sand the tips at the ends, but they are still quieter than the AWP originals.... in fact we can't hear them at all down at the genny shed... inside or out... so may not even do that.... otherwise they are as good as it gets.

Jamie has threatened to send me some pics of the original damage, I will get him to photograph the new blades when they are down.

...........oztules

[oztules]

Hi Dom,

If we had a decent jig... instead of a once off arrangement, we could knock out a set of 4m blades in a few hours with just a chainsaw and a planer... and an orbital sander just for the finish.

If I had had a bandsaw and a tenant saw , then I would not have been forced to think of this technique, and from my 2.4m blade build with those tools in Melbourne a few years ago, It would take me 2 days per set. (I get tired arms pretty quick with a tenant saw... and 4M sets seem an order of magnitude larger than the 2.4m set)

Done with the tenant saw, most of my time is spent checking to see how far I have gone and worrying about going too deep etc, with the jigs, just shut your eyes till the jig ends.... and it's done.

I don't have much talent with woodwork, this makes it childs play .

Buy an electric chainsaw if you must, and have a go.

.........oztules

[Ungrounded Lightning Rod]

1.4 KW fully furled (1.2 KW or so usable after battery storage) is sweet.

Bringing the tips down to an edge may improve the performance by throwing the tip vortex farther out, reducing the depowering of the outer half-foot or so by air running around the end of the blade.

(I'd once thought of screwing a "wingtip" airfoil onto the end of the blade to block the run-around air, ala the "wing keel" used on shallow-draft sailboats to make a short keel act like a long one (as long as you aren't listing too badly)  That would be a piecewise approximation of a ducted fan.  But a NASA design document implies that you can get much of the advantage of that, with far simpler construction, by making the tips knife-edged.  Which brings up the question of why wing keels work better on boats.  B-)  Maybe it's because, with the knife edge, you're reducing the loss of the low-pressure on the downwind side but you still lose the high pressure on the upwind side.  But intuitions about fluid dynamics are notorious for being faulty.)