Go to Otherpower.com Home Page Go to Forcefield Shopping Cart Go to Wondermagnet.com Home Page
Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Reviews - Diaries - Our Products
Another furling question


By Hank, Section Wind
Posted on Fri Mar 09, 2007 at 05:21:53 PM MST
Furling

This may be a stupid question but here goes.

I want to reduce the speed at which my PMA furls.
I know I can accomplish that by reducing my tail weight but in order to do that I either have to:

  1. Build a lighter tail boom assembly
  2. Make a smaller, lighter vane
  3. Cut off some of my tail boom to make it lighter.
My PMA set up is dual axial 9/12, 8ft dia rotor with a 6ft tail boom having a 4 sqt-ft vane of 3/8 ply wood.
Given the above, which would be my best option.

It appears to furl at about 30 mph winds producing 50 amps. What I do hear in larger gusts is a very loud helicopter noise.

This has me concerned for two reasons.

  1. My charge controler is a C40 which will take an occasional 80 amps but rated at 40 amps.
  2. After reading some comments by Flux it would appear my set-up may be incorrect. I always thought that the helicopter noise was due to blades rotating obliquely to the wind with the oncoming blade seeing a higher wind speed then the trailing blade.
The unit has been flying for about two years but only used on weekends with no problems.

Thanks,
Hank
Another furling question | 6 comments (6 topical)

Re: Another furling question (3.00 / 0) (#1)
by Flux on Fri Mar 09, 2007 at 10:38:59 AM MST

I would try cutting off a strip from the vane, reducing its length but not height and I would remove it from the edge nearest the hinge, that would reduce weight and have little effect on stability.

Flux



Re: Another furling question (3.00 / 0) (#2)
by Hank on Fri Mar 09, 2007 at 11:30:27 AM MST

Thanks for the suggestion Flux but the only question I would have is that the amount of weight removed using this approach would be quite small (vane is 3/8 plywood). Which actually begs another question:
 What is the relationship of the % of weight added/removed to the tail boom have on furling speed. I'm sure this is not an easy question to answer as moment arms, etc. come into play, but a ball park estimate would be great.
Any weight added or removed would have to be at the end of the boom to get the "biggest bang for the buck".

Hank

[ Parent ]



Re: Another furling question (3.00 / 0) (#3)
by Flux on Fri Mar 09, 2007 at 12:10:37 PM MST

Much depends on the weight of the vane compared with the boom, I assumed that the main weight was in the plywood vane rather than the steel. As you said you had a 6ft boom I thought that the vane was well out towards the end. You are right that removing weight from the end would be more effective but you will also affect the stability if you reduce area and length together.

Without knowing the various dimensions and weights it is difficult to advise.

I think you can manage with less than 4 sq ft as long as your vane is well back.

I would have thought that removing 4 " or even more would have reduced the weight a fair bit.

In theory you can calculate these things but there is an unknown seeking force from the prop that makes this rather pointless. Comes back to trial and error in the end.

Flux

[ Parent ]



Re: Another furling question (3.00 / 0) (#4)
by Flux on Fri Mar 09, 2007 at 12:24:01 PM MST

The shape of the vane also makes a big difference, I have no idea of the shape, I was thinking it was nearly square.

In general a tall short vane has more stability than a shape that is long and lean.

Flux

[ Parent ]



Re: Another furling question (3.00 / 0) (#5)
by Hank on Fri Mar 09, 2007 at 01:43:28 PM MST

Thanks for your comments Flux.

I tried the formula method before but it never worked quite right for me.
Unfortunately in my enthusiasm I never recorded weights and things like that....drat.

The tail is your classic triangle, 4 ft. top to bottom and 2 ft on the boom. Most of what I had read here on the board is that folks were making their booms about 1/2 the rotor diameter, that would give about 2 ft of steel pipe I could potentially remove.

Trial and error it will be and whatever I remove will only lower the furling speed. Adding weight is always simpler.

Hank

[ Parent ]



Re: Another furling question (3.00 / 0) (#6)
by Gill on Sat Mar 10, 2007 at 03:06:12 AM MST

G'day Hank,
Is it possible for you to add a tension spring to the furling side?
Or possibly a torque spring around the furling pivot?
Even a cord and weight pulling the tail towards furling would do the job.
I guess it all depends on your setup.
 


Another furling question | 6 comments (6 topical)
Display: Sort:
Menu
· create account
· How to use the board
· FAQs
· search the board
· Google search the board

Login
Make a new account
Username:
Password:

Total Views
  121 Scoop users have viewed this posting.

Related Links
· Also by Hank

Powered by Scoop
You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest © 2009 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!