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Forum Index : Windmills : Silent Chinese blades!!!!!

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Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5116

Posted: 10:58am 03 Apr 2007

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Looks like we've stumbled on a fix for those noisy Chinese blades. I read a post on Fieldlines last week about a set of Chinese looking blades, and the authors discovery about a ridge down the back of the blade and noise. The post is here.

I send this email off to David, who has a couple of the Chinese blades under test. One set on a F&P windmill, and another set modified by me on his Chinese windmill......

Hi David

I've been watching the forums on my site and Other Power's site, and I have a couple of modifications that may reduce noise. I've attached a drawing so you can see what I'm talking about.

Mod 1 is to use some sticky take to extend the tail. The idea is to get rid of that horrid rounded tail and create a sharp tip. The tape could extend about 5 to 10 mm past the tip.

Mod 2, which I read about yesterday on this link http://www.fieldlines.com/story/2007/3/28/205619/172.
This guy had a set of blades very similar to the chinese blades, but these had a ridge on the back which he sanded off. They then made lots of noise. So he figured the ridge must have been there for a reason and he made his own ridge with a length of fine wire and some sticky tape. Apparently it made the blades dead quiet!

If you have the time, it might be worth while giving these mods a try. Its only sticky tape, so easy to do. Wouldnt last very long in the weather, but would be ok to prove an theory.

Regards
Glenn

Well today I received Davids reply......

Hi Glenn,

Got a chance today to try the mods��.won�t bother with mod1.

Mod 2 is the answer��..all that�s left is a slight whisper, only audible directly under the mill��..now virtually silent even at 300-400 plus rpm

Bit rough and crude all I had is 2.5 weed eater nylon and cheap duct tape.

The extender hub is now on a 3.2m pole with a decogged standard 100s��sits on a pleasant 5-8 amps all daylight and self starts in low wind

Have also included a picture of a six bladed vawt using the stainless steel drum pieces from an f & p ��goes quite fast and starts when you breathe on it. The drums are awkward to handle with the cheese grate finish but definitely are very strong light and cheap. Will increase to 3 tiers and direct couple a low power f & p to see what I can get.

An interesting thing that Bergey sell a Chinese version and I was surprised at the $ for it The one kw turbine sells here for a lot less than $2800??

Also it appeared to only have a 3 bolt fixing on 2.2 metre blades �.All the 1kw models sold here have 2.9 and 3m blades

As I �ve got 2 sets of my own blades to modify I will be interested in a permanent method of ridging. I assume that fibre glassing something onto the back of the will be the answer ��..maybe if you are talking to Trev , he might have a simple solution?

Regards

David Warren

So it looks like that ridge down the back is the fix for these blades. Just need to get our resident fibreglass guru ( Yeah you Trev ) to tell us the best way to make a permanent modification.

Good news.

Glenn