GOE222 /table saw??

[ChrisOlson]

Dave,

I made that draw knife out of a piece of 4140 CRM flat stock.  It's bent to the shape of the GOE222 face except that I straightened out the trailing edge to remove what I call the "wing flap" effect from the blade.

If they work like I want them to I'm going to send the profile to Dave Moller and see if he can whack it out on his CNC machine.

For the four-blade rotor I needed really light weight blades.  With a Douglas Fir core I think they'll only weigh about 8.5-9.0 lbs each (13 foot diameter rotor).
--
Chris

[opo]

I build some modified GOE222's out of Douglas Fir 2 x 6's using the following hand tools - power planer to rough shape the blade, custom made draw knife to cut the face, belt sander to finish it, picnic table for a workbench, pine tree for shade, and Bud Lite to reduce the effects of the 90 degree weather:
--
Chris

Very interesing Chris,

If you haven't patented the new profile  , I would like to take a peek at it. Do you have it as a list of coordinates? If you do, and there is no patent issues please post it so that I can play with it a little bit with the simulators.

Congratulations for another fine job,

Octavio

[ChrisOlson]

\Do you have it as a list of coordinates? If you do, and there is no patent issues please post it so that I can play with it a little bit with the simulators.

I'm afraid this is not patented - it's sort of what you'd call "open source".  I don't have any coordinates but I think I know where you could get them.  How this came about is that I was looking at the wing on my Cherokee 180 the other day.  The PA28-series aircraft use a cambered bottom airfoil section with an enlarged leading edge, as compared to the classic Cessna wing which is a true Clark-Y.  Looking at the wing from the end with the flaps at 10 degrees I'm like, holy crap that 's a GOE222.

The stall speed of the PA28-180 is 57 with zero degrees of flap, 49 at 40 degrees.  The Piper's very thick airfoil assures that lift is lost very slowly up to stall.  The wing's design gives a range of attack angles in the POH instead of one critical angle of attack.  You can enter a slow stall and the plane will rock back and forth instead of pitching forward while at a dramatic sink rate.  Only aggressive pitch will get a sharp break and spin.  The glide ratio at best glide speed of 77 mph is 10:1 with the airplane trimmed and clean.  9:1 with 10 degrees of flaps dialed in.

At any rate, I decided that "cleaning up" the GOE222 by retracting those flaps will give me the same results as what the PA28 wing exhibits in its flight characteristics; less drag at the cost of some lift, but very gentle stall characteristics where the outer stations of the blade that are running at or close to stall at high rotor speeds won't waste as much power just moving the airfoil thru the air.

So if you can find the coordinates for the Piper PA28 wing it is going to be very close to what I have in these blades.  Note that the later PA28's (like the Archers) used a different, more tapered wing.  I'm not sure what year they changed that.  But the PA28-180 was first certified in 1962, so using the early wing design will give you the approximately correct coordinates for these blades I built.
--
Chris

[fabricator]

Or, just take the 222 profile and move the trailing edge down about 1/4" and shorten it 1/4", that looks like it would be pretty close.

[ChrisOlson]

The shortening is optional.  I just did that so the trailing edge of the airfoil is more blunt, for strength, than bringing it to a knife edge.

I wouldn't get all excited over this thing.  I don't even know if it will work.  I suspect it will.  But this is for a four-blade rotor on a geared turbine, which is not all that common of a thing for people to build.  So its applicability to conventional three-blade direct drives may not be very good.
--
Chris

[ChrisOlson]

This is the full four blade set of these new blades


This is what they look like from the end


I didn't use a table saw.  Most of the rough shaping was done with a 3" power planer.  Then take the rough edges off with a draw knife.  Once they fit the profile of the draw knife, then I sanded them out with a belt sander.

This is the draw knife I made - it works pretty good.  But I had to be careful with it so it doesn't remove too much "meat".  I screwed up the first tblade by using the draw knife too much and the blade ended up too thin after I sanded it out.

--
Chris

[windy]

opo,
 I found this website http://www.ae.illinois.edu/m-selig/ads/aircraft.html and looked into the airfoil on ChrisOlsen's Cherokee 180 which uses the NACA 65-415 airfoil, and found the coordinates and the airfoil diagram.
 naca652415.dat (1.08 kB - downloaded 199 times.)

 I also found this pdf file at http://130.226.56.153/rispubl/VEA/veapdf/ris-r-1280.pdf. It is called Wind Turbine Airfoil Catalogue. It shows all sorts of information regarding the NACA 65-415. The book also states that this profile was used primarily for wind turbines. I used the QBlade simulator to look at the profile but all the information that it generates is way over my head. Maybe you could look at it and give us your opinion.

windy

[ChrisOlson]

windy, that actually looks like the later PA-28 tapered wing.  My Cherokee 180 is a 1968 and it has the bulge (camber) on the lower side of the airfoil closer to the leading edge.
--
Chris

[windy]

ChrisOlsen,
 You must know your airplanes.
 From The History of the Piper 235 Aircraft.

Originally all Cherokees had a constant-chord rectangular planform wing, popularly called the Hershey Bar wing because of its resemblance to the flat candy bar. Piper introduced the tapered wing with the NACA 65(2)-415 profile and a two foot longer wingspan to the 235 line in 1979 as a 236. The 236 was named the Dakota. Both wing variants have an angled wing root i.e. the wing leading edge is swept forward as it nears the fuselage body, rather than meeting the body at a perpendicular angle. The Dakota came with the O-540 but a variant that had a higher compression ratio. At this time the 236 has not been STC'd for auto fuel as a result.

windy

[fabricator]

He was a commercial pilot, and still has the license.

[ChrisOlson]

ChrisOlsen,
 You must know your airplanes.

Well, I've flown everything Piper ever built up to the early 90's.  About 4800 hrs PIC alone in the PA-31T, and another 3000 and some odd hrs PIC in PA34-200T's.
--
Chris

[ghurd]

Mr. bcalmed's intentions were not to fish around for completely irrelevant licensing qualifications.
'Table Saw'
'ECM'
Bring this back on topic.

[fabricator]

Ya know what? I'll bet it would naturally move back on track when a new development happens, but if you think it's necessary to get out the moderation club, whatever.

[ghurd]

Lowe's said my new carpet would be $2050, with premium pad and installation.
They needed to send out their guy to verify the room measurements.  $40.

New development.
Today that $2050 turned into $3550 with his tape measure.
Simple math says $4680 per hour to move 4 pieces of 'furniture' an average of 12'.
Simple math says I forgot to measure a room and a half.

My step-kid has a car drivers license and couldn't tell what a spark plug does or differentiate a new Prius from a 64.5 Mustang, ma-in-law has an OH CCW and couldn't tell a 1911 from a Bearcat from Ma Deuce from a 64.5 Mustang.

Do the math since post#58.
We get it.

[windy]

ChrisOlsen,
 I'm still trying to find the NACA number for your  PA28-180, but not having any luck. Would be nice to know what the cordinates are so if the blades you are building work, I could carve a set without guessing how to reshape the profile.
 I found this picture of a 1967 Piper Cherokee. It looks to be the profile that you are talking about. It also looks like it is a little different profile than the 65(2)-415. Would you have any idea where else I could look? Thought about trying to contact Piper, but I don't think that would get me anywhere. Every website I looked at shows the 65(2)-415 profile was used on Piper Cherokee's.   
I'm going to keep looking. If anyone else has any ideas, let me know.

windy

[ChrisOlson]

I'm still trying to find the NACA number for your  PA28-180, but not having any luck. Would be nice to know what the cordinates are so if the blades you are building work, I could carve a set without guessing how to reshape the profile.

The blades definitely work.  Been flying them since July 7.



They make more power from cut-in to about 14 or 15 mph than the three blade rotor with GOE222's.  Not a lot more, but so far about 3.6% more kWh.  After the wind gets over about 15 the GOE222's make more power, and then these modified ones lose ground in kWh generated.  It is not a good comparison since I put these modified GOE222 blades on a four blade configuration.  But they definitely work.

I don't know how that coordinate system for airfoils works.  The way I carved them was to print a page with my printer of the GOE222, cut it out and staple it to the end of the blank.  Then I went to work on it with the planer and built a draw knife shaped to the profile, but I straightened out that trailing edge.  I used the draw knife to take the humps off from the planer.  Then I finished it with the belt sander, and finally by hand sanding.

Then I just build three more to match.

So in this coordinate system they use why can't you just load the coordinates for the GOE222 and straighten out that trailing edge as per my photos?  I don't know if it matches the PA28 wing exactly - I just said the PA28 wing, with the flaps at 10 degrees, looks like the GOE222.  That's how I got the idea to retract the "flaps" on that GOE222 airfoil  But it was a seat of the pants deal - I didn't use no coordinates.
--
Chris

[redtick]

Rounding the trailing edge of the profile may have disrupted the air flow off the blade causing greater drag.

A set of blades with the true profile would be nice for proof of concept.

I'm no expert but I did sleep well last night.

[ChrisOlson]

I'm no expert either.  I just fiddle with stuff until I find what works.

I think that straightening the trailing edge of the airfoil reduced drag.  These modified blades need to run at higher TSR than the true GOE222.  The reason they fall flat on their face in higher winds is because they are not running fast enough due to the gearing in the transmission, and the four blade rotor does not allow the airfoils to run fast enough to take advantage of what they could do on a three blade configuration regardless of gearing.  But in low wind speeds the four blade rotor does make slightly more torque than the three blade, which is a perfect combination for a geared turbine.

So they work good at slower wind speeds, and only make about 75% of the power that the three blade will make in higher winds.

To address the original question - yes they work and they work well.  They need to run faster than the GOE222 - they are least a TSR 6 airfoil.  They were easier to carve than a GOE222.  And I didn't use a table saw - just made them with hand power tools.  I wish I could help with this coordinate issue but I don't know enough about that to offer any information on how.  Sometime when I have the turbine down I would be happy to place a piece of paper over the end of a blade and trace it out on the paper, scan it and post the picture.  Maybe the coordinates could be derived from that somehow.  I don't know.
--
Chris

[Southbuck]

Im willing to bet you have reduced the lift of the 222.

It would be good to have a direct comparison of the 222 profile, un altered.

Feel like making another set? 

I was addicted to making blades for a couple years, I found it amazing how sometimes a small change here or there could make a blade perform so different in the same mph wind.

Have fun

Southbuck

[ChrisOlson]

Im willing to bet you have reduced the lift of the 222.

Oh, I know they make less lift.  They need to run faster than the GOE22 for best performance.  Kind of the main reason I made them is because I have long fought with controlling GOE222's in higher winds.  They are just not predictable for furling.  These modified GOE222 blades are pretty docile in higher winds as compared to the true GOE222.

I'm going to build another set when I get time - a three blade set.  Unfortunately, there is only handful of people I know that have experience with GOE222's, and most of that handful of people that has flown them have had them burn up generators.
--
Chris

[SparWeb]

ChrisOlsen,
 I'm still trying to find the NACA number for your  PA28-180, ..........
I'm going to keep looking. If anyone else has any ideas, let me know.

windy

You need The Incomplete Guide to Airfoil Usage:  http://www.public.iastate.edu/~akmitra/aero361/design_web/airfoil_usage.htm

The Cherokee entry confirms NACA 65-415

Chris:  You say you have a Cherokee?  Airfoil spec is an easy look-up in the manual.

[SparWeb]

The blades definitely work.  Been flying them since July 7.

(Attachment Link)

They make more power from cut-in to about 14 or 15 mph than the three blade rotor with GOE222's.  Not a lot more, but so far about 3.6% more kWh. 

Seriously?  Two weeks of data and you've got the difference worked out down to the decimal place?  When, in any 1 week period, the raw wind energy that can blow can vary up or down by 100%? 

I'm sure you're just basing that conclusion on a couple of cumulative energy meter readings...  but if the analysis is much more detailed than that, then I'd be very keen to see how you work it out so quickly.

Don't be hasty to draw conclusions:  You could find yourself making choices based on an outlier in the data.

[HenryVG]

Much as I hate to post this on topic, I have been fascinated with this idea since summer. Finally today I found a decent jpg of the GOE222, slapped it on a textbox, then rotated it 10 degrees. printed it out, taped it to the end of the 2x4 (ok, a small project) and started making cuts. 1 hour later I have one side of a set of 3 blades completely slotted and a good rhythm down. Tomorrow I'll do the other side and post some pictures. My cuts are not as evenly spaced as the last set of pictures, but I did NO measurements, just started a cut, then kept raising the blade a little until it hit the line of the profile. Then cut the other two blades. Stop, move over the fence a little, Repeat.  Now that I have a system, I bet the other side will take about 20 min.

At long last, action instead of intention.

[windy]

Henry VG,
 Glad to see that someone else is trying the table saw method. I used this technique on my 8.5 foot Clark-Y profile and it also works on the longer blades. A little tougher to make the cuts if the board is bowed or twisted a little bit and I had to extend the table, front and back, to keep the board flat on the table. Using the table saw, you can make any profile you want.
 I'll have to post some pictures.

windy

[windy]

 Not the GOE222, but I used the table saw to cut this Clark-Y profile. 8.5 feet long, 7.5 inches wide, 16.5 lbs each. Once I had everything set up, it didn't take long to make the cuts. It took a lot longer to sand them smooth. I used a scraper to plane the bottom perfectly flat. Now all I have to do is fiberglass them.




windy

[Watt]

Very nice for sure.   

[Norm]

Sounds like a little bit of work smoothing....ever use a planing blade on your saw?
but however end results are what counts....
Nice job....I'm envious !
Norm.

[windy]

Norm,
 
 I used a Rockwell Sonicrafter oscillating saw to cut away the waste wood. Could control the cut right down to the bottom of the saw cuts. After removing most of the waste wood, I used a hand plane to shape the front and back and then lots of sanding and scraping.
 I'm hoping all this is worth it. Only time will tell!

windy

[Norm]

Oh...sorry for the misunderstanding....missed that part thought you were talking about a
table saw....circular type
Norm.

[Norm]

Okay now I get it....used it to remove the waste wood ....gotta start reading
more carefully...
Norm