SAILWING ROTOR

[sailwing]

Working on sailwing blades for winmill rotor.  Drawing #1 shows twist, pitch and camber changes due to centrifugally driven mast extension, deflexion and wind load and how trailing edge cabel restrains twist off of tip.  Unloaded tip speed ratio of 8 and unnerving view in plane of rotation indicates no tendencies to luff or twist off in high apparent wind.  Load tests gave poor results as have searches for sailwing reference material but found Princeton's 1976 report "Optimization and Characteristics of a Sailwing Windmill Rotor" website (PDF LINK.) which gives a circular leading edge one fifth the power coefficient of a drooping D section.  My prototype has round golf club shafts, would like to keep the research ahead of construction; any other sources out there?  Any enthusiasts for sailwings in any application, or a good argument against pursuing this further?

"Thus, the amount of tension in the Sailwing's trailing-edge cable controls the important trade-off between CLmax and (L/D)max." from page 22 of Princeton Report, yet the design does not actively control cable tension.  I think some confounding (even to the report's authors) results are caused by changing cable tension due to deformation of supporting structure which gains little stiffness from the flexible skin.  Tension and distortion seem critical design factors for sailwing "optimization".  

"...at lower angles-of-attach (up to approximately five degrees), most Sailwings have a lift-curve slope which exceeds the theoretical maximum for rigid wings.  This occurs because the section is continually varying camber over the angle-of-attack range.  At higher angles-of-attack, the section is unable to deform as much as when it is less loaded.  Therefore, the lift-curve becomes increasingly more like that of a rigid wing when the angle-of-attack is increased to higher values." (page 24) , or sooner by increasing cable tension.  Why no further development after 30 years, was there a dead end?  I would like to know before I bash more metal and fabric.

[thefinis]

There are several problems with fabric but the biggest I think is the fact that it is high maintance. It ages and streaches and needs checking on. A tear or rip can lead to it shredding and then the mill is out of balance. It is also limiting on airfoil designs with many of the ones best fitted for use in the 00xx range. I am hoping to use 0018-91 for a straight bladed vawt. I want to try it for simple design, light weight and its reputed ability to change camber to meet changing air flow. If it fails to perform I will go to a rigid cambered airfoil. If you are relying on cable tension to strech the fabric then you will need to check and adjust tension(it can be springe loaded) regularly at first as the cloth streches and settles in to the wing. Cable tension may be one of the most critical variables to how the blade flies and it will vary some with temp changes.  

Windstuffnow has a hawt blade design that is glued on with a shrink to fit aircraft fabric. I think he said it would need painting. There was also a set of large sailwing blades shown in a recent posting on blade design I think. They used a filler in front of the spar to shape the air foil.

My thoughts on using sail are that if you want to experiment then great especially if the charcteristics fit the design you have in mind but if you need the power now then go for one of the more main stream designs especially for a hawt.  

Fair winds and good sailing

Finis

[hvirtane]

I think that sailwings will work

well, if you'll make a small change

for the leading edge. You need to add there

something to get the shape correct,

the round shape of the tube is not good.

I've been working with a man,

who made sailwing blades like this.

The blades have been in use 6 years

in harsh conditions in Finland.

Not any kind of problems, very good

performance.

- Hannu

[thefinis]

I bow to the man with experience. What type cloth/fabric is used on those blades? Here in west Texas the sun and stress are what I had thought would give sailcloth just a 2-3 year life span. I am watching a couple of auctions for sailcloth on ebay now so would love to know if those blades used a different cloth. I was also wondering what type pipe/tubing was used. Was it just off the shelf or was it a specialty item? I was planning on using tubing conduit. Your thoughts on tensioning the cable as it places a load on the spar but at the same time creates a truss of sorts?

I have wanted to visit your part of the world but not in winter. I will take my Texas winters and drive somewhere else to see snow.

Finis

[farmbo]

in mother earth news they have a sailwing turbine. article is pretty good. chech m.e.n. website for more info...

[hvirtane]

About the blades in my pictures.

The tubes are actually coned

light pillars. At roots there

are solid rods inside.  

The cloth is not any sailboat sail

cloth, but plastic cloth made for

building 'kuplahalli' = 'bubble halls',

big (semi) temporary coverings for soccer fields,

etc. That material is extremely durable,

I will try finding out about the material.  

You can see such a building here:

http://www.kisakallio.fi/resources/Image/ulkotilat/kuplahalli.jpg

- Hannu

[Kwazai]

your post inspired a little research (related to parafoil theory) and you understand the stuff a little more than I do. I ran across some sailing/sail info.

Mike

http://members.aol.com/r7dg/library.htm#Sails

http://home.clara.net/gmatkin/therules.htm

(see "the rig" about halfway down)

[thefinis]

Thanks for the info Hannu

We have a church here that is built of fabric. Looks kind of like a big hersey's choclate kiss. I will do some research and see what is available from building suppliers locally here. The sails on ebay went too high anyway just to see if sailcloth would work.

Finis

[hvirtane]

The sails on ebay went

too high anyway just to see

if sailcloth would work.

You might try with some old

methods to make good cotton

or canvas watertight and durable.

If you'll mix 50 g bee wax with

150 paraffin and one liter gasoline

it should make almost wonders

for the cloth.

You might also try mixing

used engine oil with

5% asphalt bitumen.

You can try tar.

... Or you can try modern epoxy paint...

- Hannu

[greenzephyr]

Sailwing Rotors have been developed and patented for our Energy Storing Wind Dam project (www.greenzephyr.co.nz). These took the Princeton developments and advanced them in novel form for bidirectional flow. Sailwings are the only solution in our case since we have to:

• reverse pitch
  
• reverse camber
  
• reverse blade twist
  
• start a TSR = 5 rotor without power-up
  
  

A "morphing" flexible blade is the only thing that allows this.

Even Starting from where Princeton left off (double surface, shaped leading edge etc) it took 18 months R&D to develop our rotor to do the basics plus the extras for bidirectionality (ie two-way wind flow but same rotational direction).

There are some tricks to the basics that Princeton did not observe or remark. A real curly one is that a double surface blade at highish RPM develops internal pressure due to centrifugal force and wants to blow up the blade tips into balls - destroying the aerofoil shape. Correct fabric orientation is critical to minimise wrinkles.

All this is able to be overcome, but we would recommend anybody interested, consider licencing our technology rather than start affresh. The author-in chief of the final wrap-up paper for Princeton was Mark Maughmer. He is still in aeronautical work as a Professor at Penn State.

There is nothing new or dead-end about sailwing rotors - all windmills before the rigid frame or slatted blades were of this type. The Princeton derivation was to an extent a "solution looking for a problem" and it certainly enabled our technology - albeit with much extra work and development.

Allan McCreadie

[thefinis]

Due to the way this board is set up there may not be anyone see this but me and maybe a couple of others. I have this thread tagged so I can find it again for some of the info so I saw a new post show up. I would love for you to post a new topic with maybe a few more details and some pictures. I doubt that many would be intrested in copying or using the design as yours is the first that I have seen that has a design need for the two way wind flow.

Went to your website. Real neat but it seems a little out there as other types like a vawt or a wall of vawts should have about the same ability but are able to use wind from all directions. I like the stacking and wall effect but being close to the ground it will have poor wind due to disturbances in the flow. Another problem is where this can be done. It might work in a canyon with step lakes especially if the wind tended to blow up or down the canyon.  

It just seems to me that it would be better to make electricity and save the water in the upper lake than try and pump the water back up.

Keep up the good work and please don't think I am saying it won't work it. Each experiment brings us closer to solutions for different energy needs.

Finis