View RSS Feed

qsmx440

Wing 1: ideas

Rate this Entry
2 Comments
by
qsmx440
, 12-03-2010 at 08:18 PM (564 Views)
Wing 1: ideas
I have spent the last month or two searching wing building ideas. I have been through hundreds of posts and pictures here at SC.org and also else where on the web. I think I have familiarized myself with the Piper L-21A drawings fairly well.

What I think I know:

1. A 13 rib wing is adequate for a light super cub.
2. The original design is the lightest and adequate for a light build.
3. For low speed, wing tips could be left off with a 10 knot penalty in cruise.
4. Spars normally fail first by "twisting".
5. Lifting is done by rib stitching, transfered to ribs, then spars, lift struts and finally fuselage. Wing hinge bolts may experience "downward" pressure due to cantelever action of wing tips on lift struts.
6. Wings lift because of down wash (hope that is correct term) from rear of wing, ie basically a verticle force from wing rear and equivalent to the weight of the aircraft. (this was a suprise to me as I was taught differently but it makes sense)
7. Extended leading edges add 10# and not much low speed lift.
8. To take advantage of many high lift designs requires advanced piloting and is not for me this build.
9. A wing mechanism consists of: fuselage attach points, spars, lift struts, compression members and attachments to spar web, drag/anti-drag wires, ribs, stitching, covering. The fuel tank is also a major consideration when planning a wing build but not technically "structural".

Submit "Wing 1: ideas" to Google

Tags: None Add / Edit Tags
Categories
Uncategorized

Comments

  1. Roger Peterson's Avatar
    If #6 was true, are we not doing weight and balance all wrong. Also I thought they added more ribs to the wing when the max speed was increased. If this is not true, flying my plane at 2000# with a 13 rib wing would be considered dangerous.
  2. qsmx440's Avatar
    Rodger . Sorry I took so long to see this. If air is not accelerated down or perpendicular to the lifting surface then why does the air flow (for the most part) backwards behind a propellor (just a wing)? Some goes off of the ends but most flows straight back. I spent some time looking for the original article which had some really good photos of a Boeing jet skimming the top of the clouds and it was really obvious the "downwash" and even the tip vortecies. The article stated that the lifting surfaces had to generate the equivalent of twice the weight of the aircraft to sustain level flight. I may be off a little about my recollection that the downwash is aft of the trailing edge and that would square with your weight and balance observation. I don't understand why a heavier A/C wouldn't need more ribs? I accept that it doesn't and that the number of ribs somehow is related to the VNE and not weight.