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Forum Index : Windmills : new build
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| Air Bender Senior Member  Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi all, I havnt been on for a while, but I am about to take down my old vawt and replace it with a hawt. I will be using the FP smartdrive from the vawt and I plan to hand carve a set of 3 blades for it, I am after something that will start producing some power in about 15 kph winds any sugestions on blade lenths would be a big help at this stage. All the best Dean |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I guess you are another who have seen the light that a Vawt was not worth the time you spent on it, welcome to the Hawt converted. As for your blades, well thats a open view. if you have the skill or the sheer desire to carve your own blades then go ahead, but if its a trial and error thing to save a few dollars and you dont know what you are doing than i suggest not, and buy a set of ally GOE222 blades off of Phill, as they are not that costly for the great power they produce. Lets face it a mill is only as good as its blades, so why put cricket bats up for blades when for a low cost you can have the real deal. It be worth you getting a price off of Phill for a set of GEO222 blades before you break the wood chisle out. PM phill here.... http://www.thebackshed.com/forum/pop_up_profile.asp?PF=217 Pete. Sometimes it just works |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi Pete I mucked around with the vawt for a long time. but in the end I just couldn't get enough revs out of it to make any decent power. But I think what drove me on was the challenge to succeed when most people were failing. But then I built a small hawt about 1/4 the size of the vawt and it regularly produces twice the power. I have heard Phils blades are very good, and they are probably cheaper than buying some lengths of good quality wood, but for me I enjoy the challenge of the build, so carving a set for me is the only way to go. I believe there has been a lot of single stator F/Ps built in the past I don't plan to modify the F/P to much so I was hoping that someone could put me in the ball park on blade length to extract the most power out of a basic f/p single three blade set up. All the best Dean. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Dean, Hey, good on you for wanting to carving a set of wood blades, it was just many think they can to and find poor results or the blades let go and destroy the mill. I have a set of GEO 222 blades and i to carved a wood set, but because i had always wanted to. My problem was i had a 5 bladed mill and that meant a lot of woodwork skills to get 5 identical blades. Im not that good so i built a profiling gig to carve them in using a circular saw...... it a pending post one day if i get around to it. But i can offer a few tips, the important parts are to have each blade leading and trailing edge to follow the same path in rotation as the other blades, or you will get turbulence and noise. The bit between each edges is important, but not as much as the edges that cut the air and direct it back together, you are creating an airflow over the blade and around the blade, and then directing each airstream from both sides back together with minimal turbulence that next blade will encounter. If you can visulize this when doing the carving it will help blade design. The tips of the blades need to also follow a identical path in rotation, as most noise comes from tip run out. (a different tip path than the previous blade) If you are doing a taper twist blade, than the tip will need to be almost flat from leading to trailing edges, that is with it in its mounted position. The most important part........ is weight per blade, they will need to be at a MAX no more than 50 grams difference, from the lightest to heaviest blade on final carve/finish, i would aim for 20 grams max if it was me. So keep weighing your timber during carving and final shaping. After assembly you can add weight to the blades for the final 20 grams to balance them to a gram or less, but if you are too far out in weight they will be crap to balance, and crap with lots of dead weight playing chase in the air. I used Western Red Cedar for my blades as its very light and strong for its weight, it also handles weathering, although a good protective coating is required as WRC will also adsorb moisture and may unbalance the blades. Its also a great wood to work with,, but it can cost if you can not find a source to recycle. I was quoted about $25.00 for a 150 x 40 x 1500mm solid rough cut piece, although i used laminated sections recycled WRC form wall paneling. Hopefully some information might help you when it comes to widdling a stick into a blade. Pete. Sometimes it just works |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Thanks Pete I plan to use western red ceder and if I can find a long enough length I will cut them out of the same piece of wood. I found in the past that separate pieces of wood very a lot in weight. I pan to do taper twist. After spending time with slow mills I want to carve a fast set of blades so trying to keep the noise down will be an issue. I feel the need for speed 
All the best Dean. |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
This is the small mill that converted me from vawts to hawts 
It only has 500mm long blades and puts out 100w just before it starts furling, while my Vawt with 2m blades is lucky to make 60w in the same winds. The small hawt has been up for 2 years and given very little trouble. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
You did ask originally what size blades to make and i keep forgetting to answer. At the very largest i would not go more than 2.4m diameter, thats 1.2m per blade Max measured from shaft centre to blade tip. So the actual wood length might be shorter due to the mounting hub etc. Perhaps someone else might have a better suggestion on blade size, as i have not done a lot with the F&P. Pete. Sometimes it just works |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=Air Bender]I am about to take down my old vawt and replace it with a hawt. I know I'm beating a dead horse, but I'm used to the cat calls from the peanut gallery it produces. Remember me? I build windmills that pump air. That being said, There JUST HAS to be a good use for VAWTs other than yard art. Building a ginormous VAWT is still on my to-do list, but winter approaches and I still have to move my wood-burning stove from the barn to my house, so building the VAWT has given way to other priorities. Still, I will do it sooner or later. My plan is to pump air, water or electrons with it. I don't want to hijack nor jack-knife this thread, so, I'll leave it be, but I am positive (dispite public opinion) something good can come of VAWTs!  . . . . . Mac
Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
And we are all waiting ....and waiting to find out what that might be. Perhaps a spin drier for the washing. Sometimes it just works |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Drag/lift type VAWT's like the Savonius, Lenz, etc, have a lot of torque, especially from a standstill. Even better are the pure drag types, like a scaled up wind speed anemometer with buckets out on long arms, can have massive torque. This torque makes them good for applications like pumping. Slow running HAWT's, like a farm windmill, can also work well in this area, but typically need a gear box to reduce the turbine RPM and gain torque. HAWT's do however give more control, you can furl the tail to shut down the windmill, something that's a little more difficult with a VAWT. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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