10 foot to 12 foot

[Mickel]

Ive just started building my first genny and have a question about the prop. Im building the genny designed by the 2 dans and putting it on a 80 ft tower.There isnt a hell of a lot of wind here but enough and I thought I might eek out another 2 ft in the prop. is this a good idea or bad idea?

[nothing to lose]

A larger prop catches more wind, in a larger area there is more power to be gained, however a larger prop turns slower, less speed means less power made.

Ya confusing eh.

Best to stick with the prop size the genny is designed for most of the time. If you want to and don't mind the expense and work it doesn't normally hurt to experiment a bit.

As long as your willing to except failure in the hopes of success.

If you want larger prop size which turns slower, then you may need more turns per coil in wire to get lower cut in speeds where power starts to be made.

I think the Dans have also built 12 foot machines so you may want to look at those?

Often it is not just the blade size, other things may also change.

[Flux]

Don't forget that a bigger prop needs a larger alternator offset.

Using a large prop with a small alternator will mean that you need to furl early, once you mess about with dimensions you may make something that you can't control. OK if you think about all the consequences at the start.

Flux

[Mickel]

thanks for that advice, I knew there was more to it than meets the eye, I just wasnt sure what that was!

I think I may experiment a bit with the size although Im saving a lot of my experimenting for the 80 ft tower. I have much research to do first and have read some very informative discussion on this site!! Oh for a flat windy site!!!!

Mickel

[seanchan00]

I am in very poor wind area being inland in tropical Malaysia. After 2 yrs of wind mill up and not getting meaningful power I have just put up another stator with 60 turns with AWG 13 wire and I can feel the cut in by just turning with my hand at below 60rpm if I put the airgap at the recommended 5/8 inch. Original stator had 35 turns with double strand AWG 15 wire. Finally opened out to at least 7/8 inch and my cut in is now just around 100 rpm and now I am getting 1 to 2 amps in gentle winds with a 9.5 Ft prop extended from the original 8.5ft TSR 5.5.. I am going to 12 ft next and closing the air gap when the blades are ready. I have an 11 ft set which I will try to test this Sunday weather permits. Its Monsoon now anr raining all day. Will try to put some pics.

SeanChan