TOPGUN WINNER

My Feedback: (27)

Are you guys designing your own aircraft or do you just want to know what washout is?

When i design a new wing, i use second generation conics for several reasons.
1. I machine my molds on large cnc machines. Therefor, to make it simple i use straight line cuts point to point.
2. Explanation: Draw your root airfoil with the low pressure point at 27%. The lpp is where the main spar is located, the thickest section of the chord and the cg of the wing. Stop and understand what i just explained.
3. Now, starting at the leading edge move aftwards and make marks every 1/4 inch back to the trailing edge.
4. Explanation: If you placed this drawing on a zerox machine and reduced it to say 70% of the size of the root tip we would have an exact drawing of the outboard rib.
5. Stack the two ribs togeather exactly on the cg and chord line.
6 draw a line between the same 1/4 mark on the root rib and the reduced 1/4 " mark on the outboard rib. They are always straight lines.
7. This wing has zero washout.
8. I want the wing to stall inboard first and remain flying at the wingtips to give me stall warning, no tip stall and better control at low speed.
9.if i took a straight pin and pinned the two rib drawings at the cg / chord intersection point i can rotate the outboard airfoil downward.
10. That is called washout.
I can make it whatever i want...2 degrees to 5 degrees. Depends on what flying characteristics i am looking for.

That is as simple as washout can be explained.

Been designing aircraft for 74 years...trump that "old card" if you can.

Hope this helps. Don"t get so technical...fly for fun...if you want wash out just grab the wing and twist it...twist the tips down...lol

good luck and enjoy. This is how aircraft and helicopter blades were designed for 50 years.. The s-76 helicopter has 27 different airfoils in making the blades. Laminar flow wings and low observable s are a different story altogether.

Quote: The cg is at 27% and not 33% as most people believe. That is for 98% of all aircraft in the world, both military and civilian. 33% is for radical freestyle competition only.

alex5

my original question was so to properly build in washout,in a plane that has been built before,but I wanted to do it from scratch.This is a simple airfoil,that can be prone to tipstalI,so that is why I wanted to build it in,as with hundreds of builders making the same model design, using cad. The actual build is traditional.I wanted to come up with a solution that I could use for rib placement in general,and how to transition along the spar with laser cut ribs.Since washout is easy to put in,in a traditional build ,there should be a way to incorporate it in the ink and cad. It turns out that you cannot twist an in line array,or use guidelines other than the path to do so.The washout exists.The replies were helpful from some contributors,and so many said,why bother?(not helpful),if not downright argumentative and directing the discussion away from the original.I came up with a solution(right or wrong) based on helpful ideas from 2 contributors.I have the plane modeled in Cad,and am refining the little parts, hoping to get it laser cut,as I did with a DHC2,which went together perfectly.

TOPGUN WINNER

My Feedback: (27)

Wish this was 15 years ago. I used to have one of the most advanced cnc shops in the world. I am 80 years old now so...
I would have invited you over and offered you a job. I have made a lot of wings and helicopter blades. 146 prototype aircraft and helicopters. Then built the tooling and production parts.

Second generation conics is the easiest way to design a wing that i know. The x-29 had wash out, so did the williams v-jet.

Send me a pm with e-mail and i will send you photos.

Chad Veich

My Feedback: (60)

It may be a moot point now Alex but I would be happy to provide an explanation of the method I use in CAD to figure out how much each rib along the span of the wing needs to be rotated in order to achieve the desired wash out. No math is involved, I use the CAD tools exclusively. I used to use the Compufoil software to do this automatically but found small errors in the results so returned to figuring it out myself in CAD.

alex5

The numerical amount of rotation I gave,did not have a great deal to do with the fact that I simply aligned my airfoil to that of the rotated trailing edge line,connecting the root base and outboard trailing end ,and my dihedral line.What might your method be?I am sure any method is an improvement over no method.Slicing the extrusion of the loft gives the same end,but I use lines,for the laser cutter anyway.Alex

Chad Veich

My Feedback: (60)

I simply stack all the ribs, rotate the tip rib however many degrees of wash out that I want, connect the root and tip rib trailing edges with a line, and then rotate each of the intermediate ribs until their respective trailing edges touch said line. I have made it a habit of rotating the ribs at the leading edge to ensure that the leading edge stays perfectly straight.

alex5

mine varied so slightly in that very technique,I chose the chordal max as the point of rotation.It only made a difference of 1/32 of the tip location,at the tip of the wing,on a 48 inch wing half