Author Topic: wind flex on bigger props help (Read 5435 times)

adelaide · « **on:** October 29, 2005, 11:25:27 AM »

Hi have been making bigger and biger props but bigger 1s seem to bend at least 1 blade bit earler, then become un balanced/noiser . i chose simular wood on latest(was amased at same sise wood flexing difrently at hadwars shop,) but still have some of this. prob is 10foot 3 blades ,only foot above 2 story bilding flatroof,outher 6/7 foot perfect next to it(near town so dont want to atract to many nerds hahah), i tryed gyde wires to help on pole out front blade to 3/4 way down each blade, helps but do i just need to make thicker blade or are their some tricks?also is the ply wood beems better for longer prop 4 this? is ply bad with elec plane? would prefer to stay simular specs for speed if i can helllp.i have alt tilted up slight so prop ferther away from pole can this contribut?gess prob is 3/4 way out by looking .works pefect till medium wind then gets medium wooooble any sugestiond pls?

Norm · « **Reply #1 on:** October 29, 2005, 06:28:46 AM »

You should be able to make it a little bit

wider and thicker near the root of the blade...

got any picture or a sketch of the blades shape?

or at least dimensions of the blades?

I wouldn't recommend plywood ...even marine

plywood ...laminate some real good grades of wood

....ah ah NO! Leave that particle board alone...

Drop it!....and Step Away !

Don't even think about it! LOL !

( :>)Norm.

IntegEner · « **Reply #2 on:** October 29, 2005, 07:54:26 AM »

A stupid nerd like knucklehead me says things like they are. Don't they talk English in Adelaide? Blades bend back, the faster they go, the more they bend back, because they are stopping the wind, just like a sail or a big sign board. But blades need to be thin so they can go fast. Solution: get to work and make maybe another blade a foot (30 cms.?) behind each blade, directly behind and just as thin or thinner. You get doubled blades, OK? Then put something between them to help them support each other against the force of the wind, something also thin. Go ahead then and make them as long as you want. Typical nerd answer that makes sense. Ha Ha Ha.

Anthony "Knucks" Chessick

IntegEner-W

See my website for something that looks like this: www.integener.com

phil b · « **Reply #3 on:** October 29, 2005, 09:26:12 AM »

I think you will have better performance if you get your prop higher above the building. You need 'clean' air without the turbulence.

Straight grained wood is best for props. No doubt. In my area, I could not find any without paying a high price. I have been using birch plywood for my blades. After breaking 2 sets in strong winds, I am now covering the plywood in 3 layers of fiberglass on each side. Without the fiberglass, this is what happened: http://www.otherpower.com/images/scimages1110100_0036.JPG

They are very strong and seem to work well.

wdyasq · « **Reply #4 on:** October 29, 2005, 10:10:30 AM »

Phil,

Once the glass is applied the blades become a cored fiberglass structure. Strip-plank canoes are a very common example of the structure.

If one wants to get really techinical the proper way would be to cut the ply in 45 degree diagional strips and laminate where the end grains shown were on the face and back of the blade. The blade would then be given layers of 'S-Glass' or maybe carbon fiber.

Contrary to the thought of blades needing to be 'thin' to go fast, the tips are flying at close to 100 mph. Those speeds are considered very low in aircraft and aerodynamic terms. As the wind speed goes up there is more than enough power to overcome the small drag increase of a 'fat' airfoil. If one care to challange this thought they should look at some data first and show me where to find it.

IntegEner's post reminded me of some aerodynamic principles that were laid to rest when Monoplanes took over the airplane industry. I will probably do some drawings and models of these thoughts - and may even test them before I claim the hole-y grail of blade design.

Ron

Experimental · « **Reply #5 on:** October 29, 2005, 12:16:45 PM »

Hi Adelaide,

If your blades are the Hugh Piggeot design, the easiest way of takeing flex out of the blades, is to permanitely glue the blades together, at the prop hub,with the plywood plates !!

I have done this, and it makes a big difference -- and going even further, I make my blades, from several laminations, insted of one thick board -- this makes them , extremely stiff !! (look at my post on the blades I made a while back)

The biggest problem with glueing them together, and to the plywood plates is, you can,t replace, just one blade !!

Another thing that helps is to put an aluminum or steel round plate, under the bolts, holding your blades to the generator, and check the bolts often, as the wood blades, shrink and swell, with the changing weather !!

Also, check the balance, but it sounds like you will really need to go to the laminated blades -- hope this is helpful.. Bill H...

adelaide · « **Reply #6 on:** October 29, 2005, 06:58:26 PM »

thank u for some advice still bit unshore about lamanated wood thow ? i have very strong hub aria glued to ply circle with wedj inbetween each then screws from ply to blade then washer on screws from f/p hub all way threw blades and ply (f/p hub cos easy off on/and some times have 2 f/p alts on each front and back).this 1 wired 100 series delta good for only 200w 12v (ushaly 2 alts on this 1)but makes power from 100rpm and furls early ,is my lo wind power experament works 2 x better than outhers in lo wind ,outhers give me over 111amps (around 1500w)in hi wind all close to factory roof cos im close to city. will send pic (roof cam)it most have plastic inner bits bent after ovened. pole is 2inch and bottom is heavy lath rail which i still cant belive flexes when the resont wobble sets in ,gyde wire from center pol in middle prop help but not good enuf ,could it be cos say top gets more air flow /1 blade has more lift??.sort of looks like 3/4 way may flex or all prop blades follow woble ?,outher four next to it are perfect but 2.2 meters diameter av. sorry about spelling, wood is pine i think .can it be tail needs to be reenfoced so it cant flex as well? will prob try dif balancing random weight then move to see if helps and next one thicker,any enginear idears like gyro powed by it ?hahah<(like the power of big prop when outhers are still in lo wind)

whirlybird · « **Reply #7 on:** October 29, 2005, 09:19:12 PM »

Hi Adelaide.

I take it that is where you are as well,I am not to far from the CBD in Adelaide and would like to contact you re blades etc. I have an old f/p ready for conversion and a lot of other projects on the drawing board.

If you are interested you can contact me on the form provided at whirlwindaustralia.com.

cya mate.

whirlybird.

IntegEner · « **Reply #8 on:** October 29, 2005, 09:30:37 PM »

Maybe a picture will help. This shows a structurally sound configuration whether the blades are thin or not.

Airplane wings and wind turbine blades have differences. Other posts are giving me the encouragement to continue supporting thin blades.

Knucks, B.S.Eng.Sci.,M.S.Physics

IntegEner-W

Tehachapi, CA

www.integener.com

rotornuts · « **Reply #9 on:** October 29, 2005, 10:01:21 PM »

Anthony, I think without a set of struts in the center a thin blade may just buckle and allow a similar amount of deflection to occur.

My real question here is how are a set of struts, as depicted, allowing for the use of ultra thin blades supposed to fit into a system that is supposed to reduce parasitic drag? Is it not true that the same structural members caused the demise of the bi-planes and tri-planes?

Mike

adelaide · « **Reply #10 on:** October 29, 2005, 11:58:52 PM »

hi just put on lighter tail (blue 1)and seeing if still wobbles when wind picks up ,so far looks better exept pole needs more gress to turn better now.i have a suport simular to that at front is thin pole out hub aria to 3 thin ropes which goes to all blades /tringal ,helped ,dident want to lose lo speed preformanc on this 1 with extra blades but good idear if i had to many rpm/more tip loses and at gess is eqivlent to wider cord ?slower more talk. my e mail is aaron32gtr@hotmail.com (have webcam on pole if any 1 wants to see add me on msn aaron32gtr) ,for the fellow ozzze?tryed ur email dident work? and yes they are close but work well and i like to experament/compare wind ushaly hits right way so no overlap 90% time(black triangle heats air with pespe/wood/car vent fan/drill on thread for traker($30 to make ) enginer freind and me estamates 2000w of hear /

Experimental · « **Reply #11 on:** October 30, 2005, 01:04:37 AM »

Hi Again Adelaide,

Looks like you are getting a lot of turbulance, from many structures on the building -- that will cause lots of problems !!

Other than that, I was once looking at the F&P conversions myself, and as I recall -- the shaft was very small in diameter, and the hub, made of plastic !!

You could very possiably be getting a lot of "flex", in both the shaft, and hub-- along with long blades --- that would set up a lot of FLEX problems

The lamanated blades, will definitely, take a lot of flex out ,but you still may have a problem with the shaft and hub !!

The other fellow, that wrote you, sounds like he is near you, so perhaps he can help you -- I,m in the USA, so I can,t drop by, and take a look ( would love to though)

I wish you good luck with your project -- and maybe it,s time to go to a dual rotor !!??? Bill H.........

wdyasq · « **Reply #12 on:** October 30, 2005, 06:40:14 AM »

Bill,

I don't care to start a war on this subject, just state a fact. Lamination will NOT increase stifness by itself.

Lamination WILL alow one to avoid areas of 'bad' wood such as knots, compression grain and runout. One can also orient the grain better. Cutting a board into squares and orienting everything as close to vertical grain is an example of that.

In short, lamination alows one to use less desirable wood, orient grain direction better and use less expensive material. One can also build much larger chunks of material than mother nature provides through the lumber suppliers. It will not increase the stiffness of the material itself.

Several woodworkers and I were discussing lamination of aircraft main spars in aerobatic planes one day. The subject of lamination came up. Jon Staudacher, who is fairly well known, made the observation, 'I never could get as good a joint as the original manufacturer'.

Ron

IntegEner · « **Reply #13 on:** October 30, 2005, 08:04:07 AM »

"i have a suport simular to that at front is thin pole out hub aria to 3 thin ropes which goes to all blades /tringal ,helped ,dident want to lose lo (wind?) speed preformanc on this 1 with extra blades but good idear if i had to many rpm/more tip loses and at gess is eqivlent to wider cord ?slower more talk. my e mail is aaron32gtr@hotmail.com "

Oh, yes, I see the 3 thin ropes now that I look closer at the pictures. I give you credit. Adding blades behind other blades can actually help performance because the apparent wind the blades see when moving faster than the wind comes from the side and not so much the front. Look at www.tlgwindpower.com in Kansas of the States for a success story on using very thin aluminum blades. Send me updates on your work or start a website of your own. Contact info is on the lower left corner of my website.

Knucks

Experimental · « **Reply #14 on:** October 30, 2005, 11:21:24 AM »

I really have to disagree with you on that Ron -- Laminations are much stiffer, and if you look at any aircraft propeller of wood, you will see, many laminations..

I had a formula 1 raceplane, and built many propellers for same -- the more lams, the stiffer the prop-- we also tried putting carbon fibre, between lams for the same reason ( when a prop bends, it changes the pitch) We tried using that fact, and tried to orient the carbon fibres, to change the pitch, when the prop bent !!

Look at large buildings, with long spans -- those glue lams are made to support the weight, with out bending !!

The spars in the race planes were three laminations of 1' thick spruce -- not because we could not get the lumber, but to take 9G+ loading !!

Staudecher also used laminated spars, but as I recall, he used a boxed spar beam and cable struts -- can,t really recall, as I was into raceing, more than aerobatics --- BUT one thing I can state, with absolute certainty -- laminated props are much stiffer !!!

NO offence intended Ron, but if you need further proof, just test it in your own shop !! Bill H........

wdyasq · « **Reply #15 on:** October 30, 2005, 07:23:57 PM »

Well Bill.

I guess you and I will have to disagree. If so, the data I read from Gougeon Brothers is a lie. I have tested it in my own shop. I do laminate. Laminates are more flexible. I am familiar with Simitar props and the twisting. In fact, Wittman used that to his advantage.

The aerobatic planes Jon Staudacher built had cantilever wings. Like many small planes the tail surfaces were rod-in-tension braced.

I stated, 'Lamination will NOT increase stifness by itself.' I stand by that. In thin laminations the glue itself can lock the fibers and cause things to get more rigid. I mentioned other things that casue lamiantions to be more acceptable. Wooden structures are quite complex. I do not believe I will ever fully understand them.

I have seen a few interesting things in mixing Glass-strand or Carbon-fibre in epoxy and wood - and other substrates. There has been very litle published on fatigue of mixed composits (wood/modern-stuff).

Wood and laminated wood are the superior materials for fatigue resistance. As a structual material, it is difficult to beat.

Ron

Experimental · « **Reply #16 on:** October 30, 2005, 09:05:16 PM »

Well HECK Ron,

One thing I think we can sure agree on -- "West systems epoxy resin", by Gougen bros, is the best there is -- espically when used with 403 thickning agent!

Other than that, we can cheerfully agree to disagree about the stiffness of laminated prop blanks, and I will read Gougeons 002-545 tech manual, again.

Good evening to you, and all.. Bill H

windcruiser · « **Reply #17 on:** October 30, 2005, 11:34:44 PM »

<html>

<head>

<title>Blades</title>

</head>

<body>

Hallo,

I have tried making hollow fiberglass blades and they surely perform better.

The prop hub however has to be very strong. see pictures

Simon (WindCruiser from CRAFTSKILLS, Nairobi)

Foot of blade is 14" with 8 bolts for the hub

prop is 14 feet diameter

This high

for more info visit the following sites:

Tala KN

Machakos KN

Morogoro TZ

</body>

</html>

ghurd · « **Reply #18 on:** October 30, 2005, 11:48:05 PM »

A big beautiful windmill!

Off topic, but if it is not too much trouble, would you please enter your location in the user map. Many people have great curiosity in such matters.

http://www.fieldlines.com/story/2005/10/26/18139/300

G-

wdyasq · « **Reply #19 on:** October 31, 2005, 05:52:42 AM »

WEST system is a good epoxy. I actually prefer some other brands for certain aplications. I think there are only two actual manufacturers and what is consumed are 'formulations'.

Most boat fourmualtions of epoxy are good. As I never had the luxury of a heated and cooled shop I drifted to System3 epoxy. I have another friend who swears by MAS. I have used many gallons of WEST, which doesn't saturate wood even if the acronym claims that.

Adhesives are another thing 'taken for granted' by most woodworkers. In reality there is a lot of science and techinique to use them. As I have gotten older I have tended to stick to adhesives I know and avoid research. I am going to try some 'Titebond 3' this week. Always interesting to me one has to find the data sheets to find out temperature requirements and other critical data.

Ron

Julio · « **Reply #20 on:** October 31, 2005, 08:15:56 AM »

Would this be on any help?

TomW · « **Reply #21 on:** October 31, 2005, 09:06:03 AM »

windcruiser;

I would very much like to invite and encourage you to write up a story on your turbine and how you built it.

It really looks very nice and I am sure many of us would really enjoy learning more about your machine.

Thank you for considering it.

Cheers.

TomW

Experimental · « **Reply #22 on:** October 31, 2005, 12:25:46 PM »

Wow, Windcruiser,

That is really impressive!!

I have built a few blades, with a foam core -- but over the years, my respitory system has become so fouled, with dusts and solvent fumes, that I now avoid the use of fibreglass and such!!

But, I,m not sure the wood dust is any better for me, and I still use epoxies to glue the lams together !!

Anyway, very nice and like the others, I would like to hear more about them..

One thing I noted, looks like about 6 degrees or better,at the tip -- is this so??

Again,very nice, Bill H....

hvirtane · « **Reply #23 on:** October 31, 2005, 12:50:04 PM »

I think that those blades

are quite thin at the roots.

If you'll make them wider

and thicker at the roots,

they will stand well, I think.

- Hannu

windcruiser · « **Reply #24 on:** October 31, 2005, 11:52:24 PM »

Thanks guys for the nice words. Building these blades (I will have to compile the story later) -- but simply you start with your best wooden blade as your male mould (work on it -- circular saw mid section farrow from tip to abot 4inch to the base, sanding and smoothing, fill farrow with putty). Then make two female covers (top and bottom or A and B). After making the female moulds remove putty from the farrow and reduce the male blade by a few milileters - to allow fiberglass thickness required.

Guys this is beter when you have a CNC Plasma machine doing this to a higher accuracy on some alluminium blade. I had to do all this by hand.

apply release paste or grease on all inner surfaces, mould your blades within 30 minutes, 3 layer fiberglass, resin and hardener -- remover the male mould first then the covers and let the hollow blade harden on level ground.

NOTE: The final product blade is hollow with a mid rib running from the tip to 4" short of the base -- this gives it more strength.

Make blade base using flat metal with eight bolts. flat metal has tubes going into the blade base wraped with fiberglass and resin - press till flat and let it set. The prop hub has coresponding holes with the blade base bolts -- arrange them in such a way that they only go one way making sure the airfoil is facing the right direction for the three blades.

My generator is a 3 phase, 12 magnetic pole, 16 coils double rotor.

Thanks for the map details. I will place my details on the map ASAP.

pics later.

WindCruiser.

Vtbsr · « **Reply #25 on:** November 07, 2005, 08:40:27 PM »

One other glue the board should look at is , Unibond 800. This is a step up from the west. I like the west for its gap filling ability but it is flexable. The Unibond is a stiffer glue. The unibond is a powder and resin mix. You have to keep the temps. up to get a overnight clamp time. I would use the unibond for the blade lams. and the west for the blades into the hubs. Then i would use the west to seal the blades completly from any moisture before painting. If the wood changes moisture content all the carving time may be lost by warping. You can get glue creep over time with the west or titbond where the glue can let the wood move slightly. Just my two cents on lamination.

News:

Author Topic: wind flex on bigger props help (Read 5435 times)