I'd like you guys' opinions on these blades

[makenzie71]

https://www.ebay.com/itm/324082219339

I'm going to be doing a little review of these...the cost is too intriguing to me.  I'm just curious what your thoughts are just from the information in the listing.  There were some points that I thought were rather amusing, but still worth looking closer at.  My goal is to test them with an iSta Breeze Heli 2.0.  I already have iSta Breeze's upgraded blades for mine, but they're pretty damned expensive to buy and the turbine just doesn't perform great with the standard blades.  I'm hoping these might be a viable option for upgrading the to a more appropriate rotor without having the double the cost of teh turbine.

[Adriaan Kragten]

If I look at the picture of this blade, I see that the reduction of the chord from blade root to blade tip is much too strong. The chord at the blade tip is very small which results in a very low Reynolds value at moderate wind speeds and therefore in a high drag/lift ratio of the airfoil. In chapter 5.4.1 of my public report KD 35, I give an example of a 3-bladed rotor designed with the optimum lift coefficient and a design tip speed ratio of 5. The theoretical chord is given in the seventh column of table 5.2. The chord is linearised and the linearised chord is given in the eighth column of table 5.2 and in figure 5.3. So there is a rather strong reduction of the chord but not a strong as for the blades you want to buy. Design of the rotor for a higher tip speed ratio than 5 results in a strong reduction of the chord.

In chapter 5.4.2 of KD 35 I give an example of a constant chord blade with a design tip speed ratio of 5 which is designed with a low lift coefficient at the blade tip and a high lift coefficient at the blade root. This results in a much larger chord at the blade tip and therefore in higher Reynolds values and in a lower drag/lift ratio. As about 3/4 of the power is generated by the outer half of the blade, better conditions at this part of the blade have a positive effect on the maximum Cp of the rotor. This is especially important for small rotors running at low wind speeds. In 2012, two rotors have been compared in the wind tunnel of UT-Delft by Nienke Hosman. One rotor had tapered blades and one rotor had constant chord blades. The measured maximum Cp of the rotor with constant chord blades was higher. The Msc thesis presentation of Nienke Hosman is given as an attachment.

 Nienke_Hosman_p.pdf (4772.07 kB - downloaded 30 times.)

[bigrockcandymountain]

They have been selling blades for a long time.  After a first failed attempt to build wood blades, i almost bought a set of 13' diameter from them.  They were a very high tip speed ratio, and i didn't think they would work for me, so i tried again and made wood ones. 

The hub looks too light and small to my eye, but you could always beef that up. 

CMS magnetics is the seller, and that's where i got the magnets for mine.  Very nice packaging, good communication etc. 

[makenzie71]

good communication etc.

Lost me there lol I have not gotten a single response from them.  I've been trying to reach them for a couple weeks, decided I'll just have to buy a set of blades to get my answers.

[Mary B]

Typical heavy fiberglass Chinese blades... total crap shoot if you get good ones or ones that will fail in the first high winds

[bigrockcandymountain]

Do they still sell on their website? Thats how I contacted them, not through ebay.  Might be a little cheaper not going through ebay.  Less buyer protections though too.

[SparWeb]

The sale is over so it's either use their website (or Mackenzie went ahead and bought them!)
We'll know soon enough...

[makenzie71]

I did not see any blades or turbine accessories on their site, only magnets.

The blades are indeed heavy and very "rudimentary" but I think they'll be okay.  I'm still working on getting a hub put together...I'm trying to get a CAD file from the seller for their top plate (they suggest these would bolt to a circular hub but that won't work, the root of the blade drops below the mounting area).  Hoping to maybe get these slapped on the Heli 2.0 in the next two or three weeks.

I'll try to get some more pictures of them here shortly showing more of how they're made.

[bigrockcandymountain]

I'm not sure what you paid through ebay but here's a link.

https://www.magnet4sale.com/wind-turbine-blades-8-5-commercial-grade-blades-only/

[makenzie71]

$170 after taxes...now I feel a little ripped off.  eBay blades are going back lol

I went all over their site before buying on eBay and couldn't find a link to any wind turbine gear :/


edit ~ never occurred to me to use their search feature.  Having products you can't actually navigate to seems...silly...

[bigrockcandymountain]

They have 2 websites.  One is cms magnetics.  The other one is magnets4sale.  That always seemed....silly to me too. 

The blades are bottom of the drop down menu on the magnets4sale website. They have up to 16' diameter available.

It's also funny that they brag about the quality and smooth finish of their blades, but from what you say that might be a bit of a stretch.  Anyway, the price is right.  I don't blame you for returning the ebay ones. 

[Mary B]

Set I got needed sanding, body filler to fill pits and sags... quality was poor!

[makenzie71]

This finish isn't awful but it's obviously a "quantity vs quality" thing.  They'll probably work fine but the surface finish is almost "unfinished".  Feels like coarse overspray all over it.  Some parts aren't even coated, just raw polyester.  They should get at the bare minimum a good coat of paint before they go up but since it's me that's not going to happen lol.  The bolt holes are also not very clean.  The fiberglass is VERY thick which I suspect is the bulk of their weight.  They are very thick and fat even toward the tips.  My iSta blades have a really aggressive pitch to them and these just kind of "go" with little variation in profile.  They say "we will do the work, but we will do it slowly and not look pretty while doing it."

I got a template made for the hub, I love having a little laser.  I'll be able to take the file to my shop of preference and have them cut it out easy enough.  I'll weld an iSta Breeze hub to back of the plate for this particular exercise, but it occurred to me that it would be very easy to just cut these for type W or type X weld-a-sprocket hubs.  Could be a pretty easy offering.  I wish I could afford a fiber laser to cut them myself.

I have sent 11 messages to CMS through eBay and by emailing them directly and have received thus far two responses...so I think ordering anything from them with the hopes of being able to talk to these people is not a great idea.  I have learned that they do not sell the hubs that match these blades because...they don't have them.  They have no way to make them and no files to build them from.  I have asked if they could swapsy between the eBay blades and their store blades (I'll buy off their site and they refund the eBay purchase) and have received no response.  I've offered to design and even provide them with either files or manufacturing for the hubs for all their blade tupes and have received no response.  I tried calling them and got nowhere that way also.  Not a very communicative bunch.

[Adriaan Kragten]

On the third photo you can see that the blades have almost not twist. This isn't correct for a tapered blade. Only constant chord blades can have no twist because the increase of the lift coefficient at decreasing radius requires an increase of the angle of attack. If the angle of attack alpha  increases with about the same value as the angle phi in between the direction of the relative wind and the rotor plane, this results in about a constant blade angle beta. Thick airfoils are much more sensible to stalling at low Reynolds values than thin airfoils. So I am afraid that a rotor with these blades will have a rather low maximum Cp, especially at low wind speeds.

[makenzie71]

Yeah there's very little twist, most of teh variation is down close to the hub, angle of attack is pretty low.  I expect them to have a hard time starting in low wind and be pretty slow in anything but a gale. 

[Mary B]

They used to offer a hub, but then everyone complained it didn't fit xyz motor they were trying to use... and they were THIN, nothing I would have flown in the winds I get.

[makenzie71]

That seems like an easy solution, though...just make the hub with a Type X or Type W flange and people can run it on whatever motor they want.  Thin is a different matter...I'm going to run 3/8" plate front and back and I think that's more than it needs, but it'd probably be easy to have all but the largest made form 1/2" plate.