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mac46 Guru Joined: 07/02/2008 Location: United StatesPosts: 412
Posted: 02:46am 09 Jul 2011
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Air Bender,
Hello Dean,
The wings look like they finished off very nicely, what do you have for a final weight for each, and are you going to seal coat them/paint??
And on another note//"nuts have a bottom and top too!!
Keep up the good work...following with interest.
...Mac46I'm just a farmer
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 08:22am 09 Jul 2011
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Hi Mac46
I sfarted working on weight of the wings this afternoon. I started with weighing all the wing halfs and then mixing and matching till all wing weights were similer, but I still ended up with one wing a bit heavier than the other two. So I started hollowing this one out first.
I ground 1/2 a kg out of this wing with an angle grinder with a sanding disk on it, very messy but it didnt take long to do. The other two wont need as much hollowed out, but i am loooking at a weight of 2.5kg per wing. I am going to glue them together with epoxy so i will probly seal them inside with epoxy resin. On the outside I will probable just paint them with an oil base paint, I am thinking about a camouflage color.
Most of the weight i have hollowed out of the top of the wings which are very light, but the bottom 1/4 of the wings are still solid as i plan to insert metel plate up the centre of the wing at the bottom which will be attached to the rotor arm and then have rod angled down from 2/3 of the wing to the hub. this is similar to i have now but i will also be adding some light rod across the top to tie the wings together as these wings are higher.
I think you could call this a U rotor. This hay not be as structurly sound as the more common H rotor, but I think it allows cleaner wind through the mill. And I am happy with this set up, and the stability of my mill at the moment.
All the best Dean
Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301
Posted: 04:27pm 09 Jul 2011
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Hi Dean,
I"m interested in the considerations that lead to the position and shape of the hollowed sectons.Was it convenience/ease of process or design advantages?Cheers Rastussee Rastus graduate advise generously
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 10:12pm 09 Jul 2011
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Hi Rastas
The tapering in of the hollowed area was done at the points where the braces attach. I think this is a high pressure point and tapering it will ease the pressure over a larger area.
All the best Dean.
Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301
Posted: 04:51pm 11 Jul 2011
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Hi Dean,
Just an after thought,perhaps the V sections in the middle of the picture may have spread the forces better if they were radius curves?Cheers Rastussee Rastus graduate advise generously
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 10:53pm 11 Jul 2011
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Hi Rastus
I beleive You are right that having it curved would be better. I still have more balancing to do. I am about to have a go at balancing them from end to end to get an even distribution of weight over the lenth of the wing, so i dont end up with one wing heavier at the top or bottem than the others so i still have a bit more grinding to go, so they may end up curved yet.
All the best Dean
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 09:30am 12 Jul 2011
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Hi all
We done the same type of tapering to our sailboat masts years ago in areas where they used to brake.
I still have a surviving peice of one of these masts. It has been used as a mast on the kids pirate ship. See the tapered sleeve pop riveted on to the lighter section.
All the best Dean.
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 12:50am 21 Jul 2011
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Hi all
I have put a bit of time getting the ballance of the wings, after I get them to ballance at the same point along the lenth I have to go back and do the overall weight of each wing again, this can go on and on and keep hollowing out untill there is no wing left if your not carfull.
I have hade a jig for welding the rotor arms to the plates that will fit up inside the bottom of the wings. I find that when i need to weld accuatly it is worth taking the time to build a jig as it can take a lot more time to fix a weld that is not straight later on.
I bought some epoxy glue and paid far to much for it, but being out in the sticks I dont have much of a range to choose from and to travel or get some sent in would outweigh the savings made. I have far more than what i need so i will have a good stock in the shed for a while.
The rotor arm with the upright plate welded on will be heavy but i am not to concerned about it as the weight is down near the level of the hub and if they can keep the wings standing straight up and down the weight is worth it.
Welding the plate onto the rotor arm wont give me any adjustment on AOA but if i need to adjust this i can always hold the rotor arm in the vice and twist the plate at the bottom with a big shifter.
I have routed out a slot in the bottom of the wings for the plates to slot into. I am concerned that when I glue them together glue will ooze into this slot so i am going to wax the plates up have them in place when i glue the halfs together. Hopfully I will be able the pull the plate back out after.
So over the next few days the wings should get glued together.
All the best Dean
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 11:50am 21 Jul 2011
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Dean pulling the support struts out after the wing is epoxied together might be tough, even if you waxed them very well. Its a large contact area and the wing is not something you want to clamp in a vice to hold it as you pull.
You might try to heat the steel bit up, a little over 100 deg C will do. Quickest for that is possibly a hot air gun but you need a heat resistant shroud to stop scorching your wood at the exit. Once hot it should slide out much easier though my experience so far is with much shorter joins.
Good luck.Klaus
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 01:10pm 21 Jul 2011
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Thanks Klaus
I think the trick may be to not get to much glue on the plate but i do want to glue the wood right up to the edges of the plate as this may prevent the plate working into the wood over time, so hopfully the glue will only come into contact with the edge around the plate. I am also thinking of putting a coat of vasaline over the wax.
If it does get stuck i will certanly try the hot air gun before I try any heavyier type of extraction.
All the best Dean.
Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301
Posted: 01:26pm 21 Jul 2011
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Hi Dean,
Your project is coming along well,quite professional and precise.If I can throw in a suggestion of using plaster of paris in the truss slot when glueing together.Once cured the plaster can be crumbled away from inside the cavity.I've had success doing this although the cavity hasn't been as long as it appears to be in your pic.It has been years since I've used this method and plaster products have developed so pick one that has a consistancy of gyprock(plaster sheet),it will come out very easily.Cheers Rastussee Rastus graduate advise generously
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 02:41pm 21 Jul 2011
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Hi Rastus
I have thought along those lines but the problem is that the slot is 500mm long. I think i will just have to to be carfull not to spread a lot of glue around it.
I bolted the two wing halfs together the other day and done a bend test on it, and i am quietly confident with the strenth of these wings even with some of the wall thickness being reduced down to 5mm.
I am starting to look forward to having this windmill up in a good strong south westerly which we have had a few of lately.
All the best Dean.
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 04:46am 23 Jul 2011
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Hi all
First wing has been glued together.
Our maximum temperature here during the day is 6 deg so i took the glue inside and heated it up in front of the heater before mixing it. At these temperatures it is recomended not to unclamp for 48 hours, as i only have enough clamps to do one at a time it will take near a week to get them all glued.
All the best Dean
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 12:12pm 23 Jul 2011
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Hi Dean, just as well you used lightweight bricks there, I would not put weight on that setup on the unsupported ends lest it might distort the laminate.
If you had some big C-clamps you could use a straight piece of 50X100 or so timber on top to spread the clamping pressure, it does not require lots of clamps doing it that way. Of course, you'd clamp the C- clamps to your straight workbench as well.
I keep my epoxy in a small wooden crate that I lined with corrugated cardboard. Inside is a heavy duty 15 Watt resistor powered by a 6V transformer via a temperature sensing switch. This keeps the inside at a nice 30 degrees centigrade.
BTW, one can *never* have enough clamps but I also have 10 lead ingots (15kg each) that were leftover ballast of my yacht to put pressure on lamination's like that.Klaus
Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301
Posted: 01:19pm 23 Jul 2011
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hi Dean,
With the slower setting time you could have an advantage getting the strut flats out.Once the epoxy has no more slump you could try to remove it.Having not set completely should not take as much force to break the seal to slide it out.That's if you are game.Cheers Rastussee Rastus graduate advise generously
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 11:14pm 23 Jul 2011
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Hi Klaus and Rastus
I had a slight bow in one end of the wing. This is the end that is hanging out over the end of the table with the brick on it. I just moved the bricks around untill it all sat straightand i only have about 20 min to spread the glue on and get this right. Klause you are right clamping them between a couple of big lenths of wood would be best but unfortunatly i dont have any, and none that are straight anyway.
Rastus I am very tempted to pull the strut out of its slot but i have waxed pins through all the bolt holes that will need to be knocked out first and to do this i will need to move the wing around. I went out and checked the glue this morning and it is starting to set hard but i am still not game to upset any of it yet.
All the best Dean
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 07:38am 01 Aug 2011
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Hi all
The gluing has been a success and the plates puled out easily, they have been sanded and ballanced again.
At the moment I am up to the painting stage which is apart I enjoy as it is a sign that the messy part is nearly over.
All the best Dean.
mac46 Guru Joined: 07/02/2008 Location: United StatesPosts: 412
Posted: 12:48am 02 Aug 2011
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Air Bender,
Good work Dean. The new longer blades look the treat, even better with some paint I'll bet.
How long are they now and what was the diameter of the vawt?
Good work.
with kind reguards...Mac46I'm just a farmer
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 09:05am 02 Aug 2011
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Hi Mac46
The wings are 2m long and the diameter will be 1.7m. It has been a while since I done any spray painting and the first coat was full of runs, But the second coat went on a lot better. While the paint was drying this afternoon I started welding the rotor arms and started asembling a few things and it is starting to look huge, no where near as big as yours but in my small back yard it will be big. the top coat will be leaf green. I am hoping it will blend into the surrounding trees. The final weighing and balancing of the wings before painting they weighed in at 2.3 kg each, if i had have used better quality cedar i think i could have got the weight down quite a bit more. I think that without holowing out the insides I would be looking at a weight of over 3 kg per wing at this point. And hollowing them out gave me the opertunity to balance them very well. The next thing is to make sure I get the rotor built true.
All the best Dean.
Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206
Posted: 08:37am 09 Aug 2011
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Hi all
I have started assembling, which had to be done on the back verandah as the wings were to high to lift up and slide onto the plates in the shed.
The next thing is to add some bracing in to suport the wings, hopfully this will get done in the next couple of days.
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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but I also have 10 lead ingots (15kg each) that were leftover ballast of my yacht to put pressure on lamination's like that.
