2 blade /stable?

[adelaide]

wondering if any 1 had good idear for 2 blade slow furl (i think less tip loss from 3 blade)i got bit scerd on early expermenting on 2 blade wow the wobbbbl when furling /turning. at moment herd of fan tail (complicated)and smalll tail (hard to make furl) so any idears and is it better than 3 blade prefomance with apropriate corde to mach?

[TomW]

adelaide;

Well, I am very far from any kind of "expert" but my opinion on the 2 blader and any benefit it may have is they are completely and utterly offset by the fact that the yaw shudder will more than likely destroy the mill in gusty locations.

The blade root takes a helluva beating every time it does it as do the bearings, shaft, bolts and damned near every part on it. Not to mention the horrendous Noise.

Some folks find them to work OK but for me I will stick with 3 blades or more and always an odd number.

Just my experience and observation.

Cheers.

TomW

 

[ghurd]

Tom,

Any idea when or why it is better to go from 3 up to 5 blades?

(Always being oposite of most people, I've got a PMA or 2 with low cutin, and higher than I can use output.

Wondering about 5 slow undersized blades that would stall at higher speed, limiting output, but enough torque for startup in lower winds.)

G-

[TomW]

G-

Well, I really think i made that less than clear.

My true preference overall is 3 blades. I guess the point i wanted to make was even numbers of blades will all suffer more yaw shudder than an odd number.

There probably are reasons to go for more than 3 like startup torque or others but I can not say for sure. I actually have never personally used more than 3 so no experience.

Sorry for the confusion.

Cheers.

TomW

[adelaide]

i like 3 after starting with 2 but is their a % they peform beeter thasn 3  (less tip los?) as for start up add some hub extenshons near root worked for me on f/p to start early, they are hard to start, if was big % better  ,2 blade was thinking of some thing to turn it slower eg try fan tail or flap with 2 swiches on tail and geard elec motor to pol (furl bit slow to respond thow?(another reason to ezperament haha)

[ghurd]

I do not think the tip loss is much compared to everything else.

I would be concerned the root extensions will drag back the blades at operational speed.

Is the f/p decogged?  (De-cogged?)

G-

[adelaide]

no none of my 6 up are de coged but they are usles without the hub etenshons i get 100a 12v chaging reglaly and dont have cog prob any more (fixed on outher side problem  more talk)as far as i can tell thay add power all the way? have blades from 1.6 m to 3.3 all 3 blade 1 has 2 fp for lower rpm chage,used tin screwed and glued and perspex(tin is 1.5 year tested plastic only 8 months tested  woriied about uv thow .have had tail swing losse on 1 which broke all blades and alll hub bits still atached ,makes it harder to eletric break using all phases join relay befor rectafier thow.i think turbo may be simular/? does any 1 know how much %los think i herd plane winglets(up cuved bits at tips) give 5 to 10 %better peformance ? i also find u can gett away with less angle on blade to start so may go faster?

[ghurd]

I am no expert, but I find less tip angle and starting to charge not always very related.

[adelaide]

it depends on altenater and prop sise alot,  blade calculaters are a help 4 me, makes diff from being able to have bigger prop and still a wire wind for speed better amps out eg 12 v f/p 80sp around 20 a charge/ and faster to cut in, same alt just wire 80p makes around 40a but needs speed that 1

[TomW]

adelaide;

I am confused by some of your abbreviations?

12 v f/p 80sp

I assume your talking about a fisher and paykel used at 12 volts but what does "80sp" and  "80p" mean?  Spelling I can get past but those i don't get.

Thanks

Cheers.

TomW

[adelaide]

hi sorry f/p 80. fisher and pykle .8 wire. as in standard they are 1 big star total 42 coils i think, P is  in parallel we chop the links and make 14 stars in parallel. (hi rpm hi amps 40a 12 v charge)

80sp is series parallel which is 7 stars in parallel with 2coils on each leg (medium  cut in medium amps around 20a.   A S  is series non re wound so lowest cut in low amps .sorry about my spelling   then u can series or deta them

[hvirtane]

I think that by using

weights to balance

2 blade rotors they

would be OK. The balance

weights can be used

as starting wings, too.

That kind of arrangement

has been quite common

in Germany with small

scale wind turbines.

- Hannu

[adelaide]

have put 2 small on a bigg 2 blade befor still was bit wobly(may have helped ) ,prop cos weight still out ?was considdering doing a 1 blade like that. do 1 blade big 1 small experament 1 day like that , u got any pics of that prop? sonds intresting