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thefinis Regular Member Joined: 23/08/2006 Location: United StatesPosts: 53
Posted: 05:54am 10 Nov 2006
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Hey Glenn
Looks good and I think that the al will be fine as you are not making a real tight bend. It will ding easy. The only area that looks kind of iffy is the large open span middle flat section but if tight and snug should be okay.
Are you going to put winglets on it? I am in the process of building a test version that I will post pics of after it is put together. I have been cutting and painting all day. It has ends with winglets that extend 2 inches on the edges. (sorry guys I don't have the conversion tables handy on this computer) I am making it out of 48x96 inch sheets. It is 30 inch wide 48 inch tall 64 inch length which takes a 48x96 inch skin. Makes for a 160 inch diameter swept area. I had several false starts while trying to find material that was light cheap and easy to work. Each time I changed materials the support structure changed. If it works well I will build a taller version on a real tower with a speed increaser 6.5-1
Take care down there.
FinisTexas born and bred
windstuffnow Newbie Joined: 30/06/2006 Location: United StatesPosts: 31
Posted: 03:29am 11 Nov 2006
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Finis, That's a big one! Diameter wise... 13.3 ft.. that thing is going to have one heck of alot of torque in a moderate wind! post some pictures when you get it up, love to see them!
windstuff Ed
thefinis Regular Member Joined: 23/08/2006 Location: United StatesPosts: 53
Posted: 06:02am 11 Nov 2006
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Ed I wondered where you were hanging out these days. I started out trying to design for a 20 ft dia vawt so have been keeping all the test models at around 12 ft. But I may give up on the anything that big because the rpms are just so low. This baby might fit on that silo of yours. The skin may only be good for a test model but we will see. I think that everyone here will get a kick out of it. I expect to have to use something better and more expensive when it goes up on a bigger tower.
I had looked at plastic barrels, metal barrels. drain culverts, old water tanks and even cotton gin parts(found some 36 inch sheet metal tubes over 6 ft long in their throw away pile). Most of it ended up too heavy or too expensive or too much trouble to fit with other materials. Then I found some reasonable 4x8 ft waterproof sheets that looked like they might work and after some figuring and drawing and research decided that it was a good starting point/building block.
My last test set of sailwings has been a big flop. Not sure why. Designfoil's wind tunnel program seems to think that they are high lift with reasonable drag. Reality says they must be almost even on the lift and drag. They will self start in light winds but in a good wind they will slowly go one direction then stop and go the other for a turn or two. Tear drop shaped with about 30 percent thickness at around 15 percent of the chord. They were supposed to develope chamber with rpms but never got there. Tried all kinds of angles even tried starting my angles with them lined up with the inside flat edge at 90 basicly like a small covered lenz. Oh well will take it down and try again with more chord and less thickness.
The failure gave me an excuse to build and get some figures on your lenz2 in my location. With luck will post some construction pics first of next week. I am not going to try and put it up till we get a clam day too much wing area to fight in a good breeze.
Finis Texas born and bred
windstuffnow Newbie Joined: 30/06/2006 Location: United StatesPosts: 31
Posted: 08:44pm 11 Nov 2006
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Hi Finis,
Sounds fun, can't wait to see it! I've been sticking to smaller diameter units to keep the speed within a reasonable rate. I did come up with some nice barrels that would work well for a larger diameter about 9.5 ft but will only make a 6ft tall unit. When you see something like that laying around and your mind wonders through possible uses, you simply can't leave them behind. So I've added them to my pile. I have 3 piles that I work with... The scrap "goodies" pile from anyplace I can find it, the second is stuff from the goodies pile that was made into something but didn't work - still useful as premade parts, and lastly the pile of shavings from making stuff - usually gets swept up and tossed unless its aluminum then it gets a chance to become new parts after its melted and poured back into blocks. Very little gets wasted around here.
One thing I'm considering on a large unit is cloth covered L2 wings. Basically a frame with cloth covering stretched tightly then sealed. A stits cover would work very nicely although the nose would still need to be a bit more solid. I built quite a few experimental aircraft using the stits method and they held their shape in 150+ mph winds, I'd bet that method would work very nice for large L2 wings. Although, I don't think I'd do them in the 35ft version I was on the airplanes... what a machine!
Have Fun and keep us posted on your progress !
Windstuff Ed
vawtman Senior Member Joined: 14/09/2006 Location: United StatesPosts: 146
Posted: 11:14pm 12 Nov 2006
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vawtman Senior Member Joined: 14/09/2006 Location: United StatesPosts: 146
Posted: 11:34pm 12 Nov 2006
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Finis
I have a hard time understanding why you want to use wide diameters vs height with the vawt unless your prepared to make many blades.
Im lost with the reasonings.Seems too many losses.
Please explain
V......:<?
Anywho just trying to get acclimated to this nice sight.
Ride Em Cowboy!
thefinis Regular Member Joined: 23/08/2006 Location: United StatesPosts: 53
Posted: 03:54pm 13 Nov 2006
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It is a nice site so try to behave and not scare Glenn again.
When I first started I expected to build a 20x20 ft vawt with a 4 tsr. Much of the sizing was due to the materials I had on hand both for building the turbine and the tower. The blade speed was scary even in moderate winds but I thought that it was needed for efficient use of the wind. Now with experience I see that you can achieve good efficiency in normal wind speeds with a slower large winged vawt. This has caused me to reduce the design diameter due to really only being able to increase the rpms in a ratio of 6-1 to about 8-1 without going with double speed increasers.
Why am I trying to go big. Most folks here and at fieldlines are wanting to make their own electricity to use. Their objective is much different than mine. I farm and ranch and want to build my own wind farm both for myself and as an example for others. It seems silly to me to sell your wind rights to a big company for pennys on the dollar when most farmers have the shop and the construction ability to build their own units if they just had a good working design that they could use. Here in Texas, in much of the land down under and in many other places there are areas where the prevailing winds would make a line of turbines feasible. It just makes sense to make them as large as possible so that the number of machines is as small as possible.
I will go higher/taller but first I have to get the building blocks designed right. I really wanted to go with 8 ft tall so I did not have to cut my 8 ft 1x2 inch boards. Last time I had to bolt a piece of plywood to the top of my JD tractor and then put a step ladder on that to reach the top of my wings. It will be shorter wing sets from now on till I make a tilt up tower.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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