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maaca
Newbie

Joined: 21/11/2006
Location: New Zealand
Posts: 22

Posted: 02:23am 30 Jan 2007

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Hi Guys, Can someone advise me if a four foot prop of Hugh Piggotts design {3xblade} will drive a F&P old
Model 100, configured in series and star. Cut in speed is very low and output up to 300 odd revs is 50 to 60 watt, which is ideal for my application. I will de-cogg it or try to, {and while Im on that subject what do you guys use to do that operation?}which should help in start up. Your thoughts much appreciated.Regards, Maaca.

FandPwithPVC
Regular Member

Joined: 09/09/2006
Location:
Posts: 64

Posted: 11:28am 30 Jan 2007

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Hi Maaca The answer is no.The 3 blades with an overall diameter of 2300mm will lack sufficient torque to overcome cogging. They will sit without moving for long periods. Decogging will help but any output will be comprimised. Generally speaking you need blades 1400 to 1500mm long.However we made a 5 blade Piggott with a picture of it on this site page 6 THE BACK SHED TO OPEN.It does not have any hint of cogging and runs in very light breezes seemingly waiting for more wind. We use a 24 volt system with a 100s in delta. See page 4 Test Result Surprise. Up to 15 amps occurs in strong winds on this tower which does not furl.(Simple As) Before racing off to get some secondhand Oregon consider this.To get 3 blades all to weigh and be exactly the same is very hard. We have all the best equipment and expertise and 5 blades is nearly impossible. It took 10 days with 2 people working on and off.Fibreglass is looking better and we are working on blades about 1400 long with the same airofoil as Piggotts. Regards Dennis L

maaca
Newbie

Joined: 21/11/2006
Location: New Zealand
Posts: 22

Posted: 06:51pm 30 Jan 2007

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Thanks Dennis,all points taken.Can these fibre glass blades be purchased some where and are they expensive?. Thanks Maaca.

Bernie the Bolt

Regular Member

Joined: 26/10/2006
Location: United Kingdom
Posts: 45

Posted: 03:47pm 31 Jan 2007

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Hi Dennis , Like Macca I have a series 100 I wish to put up. Can you give me more specs on suitable rotor sizes please ?

Bernie the Bolt

I'd rather be sailing!

Trev

Guru

Joined: 15/07/2006
Location: Australia
Posts: 676

Posted: 12:27pm 01 Feb 2007

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Hi Guys,
I have looked at these piggots and I don't believe they have all the angles correct, thats why you need a longer blade. Longer blades also have slower rpm.

My F/g 1m (2.1m diammeter x 3 blades) composite blades start up with very little wind (3-4 mile/hr) when I have them on the hub that produces the tip angle of 5 degrees. Currently I have a set on a hub that the tip angle is 1 degree, and the startup speed is 8 mile/hr, but they do spin faster, and give lots more power.

My longer, 1.4m (2.9 diammeter) drives 2 x F&P motors. Tip angle of 5 degrees, start up wind speed is 3-4 mile/hr.

I have not decogged any motor, that just reduces your output.

It all depends on what wind you have, what rpm you can get, and wire the motor to suit the kind of voltage you want. You want the shortest blade possible to keep the rpm up, but to start at what you see as acceptable wind speed, that is according to your average or most common wind. You need to set up for the best overall. 2amps for 12 hrs is better than 5 amps for 2hrs.

Trev @ drivebynature.com

FandPwithPVC
Regular Member

Joined: 09/09/2006
Location:
Posts: 64

Posted: 10:59am 03 Feb 2007

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Hi All Standard 3 blade wood Piggotts have been around for a long time. Then F and P started appearing and try as we might we can,t get them to match properly.So forget about carving them.Trev,s comment about Piggotts angles got me thinking. The blade angles are very similar so what is causing A MAJOR DIFFERENCE IN PERFORMANCE Notwithstanding angles, T.S.R Betz, blade width and the length of the blades at this time .The amount of blade face surface which is producing energy or extracting it from the wind is TWICE AS MUCH ON TREVORS,S as it is on the Piggotts. My own PVC blades also suffer from this lack of blade face.I ruined there performance just before going to Mackay.Making the tips narrower was wrong when I should have been making the blades wider.Regards Dennis

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