Studying the Plan

[Dan_]

Ken,
Here is your last one superimposed...  How about plotting the Clarck YM 15 in that sofware and let me put it on top of your mini-max rib drawing..?

Attached.

It appears to me that if you put the blocks into your rib jig for a Clark Y between the front and rear spars, and bent a rib stick around them, you would have it...

[dz1sfb]

Don,
Here's the plot of the Clark YM-15. The nose rib area looks closer, but with more variation in the upper surface and of course quite a bit taken off the bottom.

I am thinking that the Minimax rib profile is a great choice. Looks like it will tolerate a higher AOA before stalling.

[Dan_]

The nose rib doesn't count of course, because it is built separate.  The lower rib stick doesn't count, because we know it is modified to be flat.  

That only leaves bending the rear portion of a rib stick over the rear spar, and you would have it.

W2P evidently means, "I know what I did, but I am going to my grave without telling what it was...

So if you want to compare airfoils, you will just have to accept that the nearest published performance you are going to get is the Clark YM-15, and go from there.

Attached.

[dz1sfb]

I am going to build the wing using the supplemental drawings supplied by scottiniowa. I am really not up to experimenting at this level. Someone once wisely said, "don't fix what isn't broken". We have a stable working platform here and this is my first full scale project.

[azevedoflyer]

  - NACA 4412 up to 4418 have convex tops and bottoms, even if ever so slightly. Thus, the wing section used in our Eagles are NOT true NACA.
Section thickness, per full rib drawing is (204/1397)*100= 15% and this % depends on your trust on the drawing! Copies may not be scaled equally on the horizontal and vertical axis. Case in point, using the stated dimensions from full rib drawing and working out a scale, they are different for Y-axis and X-axis!
If the scaled vertical dimension is used, thickness the section comes up at ~18%! These facts have pushed me out of my comfort zone.
Therefore, my DE wing will use a Harry Riblett's GA30A418.
azevedoflyer
 

[scottiniowa]

- NACA 4412 up to 4418 have convex tops and bottoms, even if ever so slightly. Thus, the wing section used in our Eagles are NOT true NACA.
  These facts have pushed me out of my comfort zone.
Therefore, my DE wing will use a Harry Riblett's GA30A418.
azevedoflyer

I shouldn't even go into this can of worms and most of you know there are entire books and many of them all about airfoils...That being said, there a few but important things to remember. 

• At the speeds of this/these aircraft will attain, if the airfoils are close, the c.g. very close,  and known plots for building are done in a easy to follow format (i.e. smooth and repeatable) Then the likely hood of being able to discern between two of them will be tough to judge on performance.
• Harry Riblett's book on GA airfoils is very interesting and he "talks about" other airfoils at great length.
• The angle of the cord line to datum line and the H stab have perhaps a greater effect on performance than anything else, but you hear very little of folks changing these figures (I am not saying you should) but some airfoils allow the tail to be drug through the air 1-3% different than other airfoils. But again,  at 60 mph, vs 61 mph, it gets hard to know what did what as often the case that the builder changed more than one thing at a time. (creates an impossible task of knowing what results changed, and what actually did the changing) 
• Drastically changing an airfoil on a 180 mph plane vs a 60 mph plane, can have huge effects on one, and little effects on the other, depending what changes were made. But....... as we have seen over the years, some airfoils really work, and some have scared the heck out of a few test pilots. (maybe alarmed would be better stated) 
• Having the ability to know exactly how your wing is going to be built, before you build it, and a pretty good idea on how it will fly is a pretty big battle already won! 

Best of success to you all!

[azevedoflyer]

ScottinIowa,
Agree with your arguments, specially about "...a major battle already won".
In defense of my choice, the GA30A418 is not much different from the well behaved NACA 4418, as stated by Harry Riblett himself. However it incorporates a few corrections worth the + effort in my opinion. We shall check it out when I get my DE done. Besides, this is what EAA is all about, is it not?
Cheers,
azevedoflyer

[scottiniowa]

ScottinIowa,
Agree with your arguments, specially about "...a major battle already won".
In defense of my choice, the GA30A418 is not much different from the well behaved NACA 4418, as stated by Harry Riblett himself. However it incorporates a few corrections worth the + effort in my opinion. We shall check it out when I get my DE done. Besides, this is what EAA is all about, is it not?
Cheers,
azevedoflyer

Oh yes, I would never say a bad thing about any of Ribbletts airfoils.  Harry really worked the numbers.  And certainly is what homebuilding is all about.

[Dan_]

ScottinIowa,
Agree with your arguments, specially about "...a major battle already won".
In defense of my choice, the GA30A418 is not much different from the well behaved NACA 4418, as stated by Harry Riblett himself. However it incorporates a few corrections worth the + effort in my opinion. We shall check it out when I get my DE done. Besides, this is what EAA is all about, is it not?
Cheers,
azevedoflyer

How are you going to figure out where to put the spars and diagonal / vertical brace strips..?

[Pradeep ks achary]

Hello XL Builders
  About once per year, sometimes every other year, I get a bit into why I created the sheets I did. Have not done for awhile so thought this would be a good time to cover it again.  So take this as a explanation of only what I did. Absolutely not saying this is the only way- (we all know it has been done many ways) nor that anyone else's way is wrong.  Simply a way to quickly move fwd with the project. So the details.

• We have all heard that the full length rib drawing and the rib drawings in the plans 8.5" x 11" pages are not exactly the same, but certainly let it be known at the speed of the aircraft, both will work fine. I simply took the closest coordinates (computer generated) that I could find, and created the full scale wing rib drawing. I clearly mark the estimated  cg line on this drawing, and the estimated one for the drawing in the plans. I guess to be fair, I should have three lines on it.  But clearly they are all so close that if you have big feet vs little feet,  lean fwd or back in the seat... at these speed,  none to worry.
• With these drawings, I created full scale templates, (included in the drawings) to match the wing rib that I have drawn. This should cut down your time to make parts by 70-80% And certainly one of the main reasons I did this.
• The just mentioned parts are for EVERYTHING on the wing rib.  NOSE-AILERON- what I call a K BLOCK for the cove-any any other PART required. All for time savings, NOT a correction to your plans. But these are for what I drew, not to make parts for the plans drawings. (they won't match exactly)  But mine will match my drawing.  NO mix and match intended.
• With the full scale drawing, of the rib, you should be able to have your rib jig built in 2 hours or less, with parts on hand.  Just a huge time saver as intended
• I drew all the gussets, simply to make best use of the .8mm ply.  Remember, this was all intended to let high school kids-learn the basics of building project and gently  guide into the art of waste reduction and planning.
• I drew for those that like building but don't really care to calculate every last part of the wing, or study in depth of "how to build-and in what order"
• I did not change how the wing attaches - the strut attach locations -nor how the wing is built.
• I did simplify how to view during the build process.
• I did price this at my  printing/shipping cost to help keep folks going fwd in their project.
• I do not- supply CAD files on what I drew... as I find those without associative CAD file systems- soon make changes to one area, without it then changing the next affected area- thus soon becoming Scott's fault that something did not work out... I'm sorry, but presently don't have time, to delve into "what was done wrong, to find what to make right"  This can quickly develop, and if I was retired, maybe...but presently simply can't do this detective work.  Just presenting a " do this and it will all fit " set of drawings.
• I never intended, nor intend to do plans for the whole aircraft. They are supplemental only- and 90% for the wings. There are things here and there that are perhaps improvements to various areas of the aircraft, but NONE are intended to dramatically change the bird. My background is in far larger aircraft, with gross weights of 1700 to 2500, so this is a treat to me.

Hope this helps explain- Great fun helping.  As always, I have said, that if you don't like, I will return your funds less shipping, when I get the plans back. To date, none have been returned. Enough said.

Best of success all!

[Pradeep ks achary]

H, Can anyone help me, Rear wing strut notch cutting, is this really need ? Or can I use same as the front wing strut ? I am building XLC95...

[scottiniowa]

H, Can anyone help me, Rear wing strut notch cutting, is this really need ? Or can I use same as the front wing strut ? I am building XLC95...

I'll bite, what is a " rear wing strut notch" I must be losing something in translation?

[Chuck in Indiana]

I'll bite, what is a " rear wing strut notch" I must be losing something in translation?

Scott, I'm pretty sure he's talking about the 5 degree angle on the rear strut fittings, and the notch that needs to be cut out to do that.

[scottiniowa]

Scott, I'm pretty sure he's talking about the 5 degree angle on the rear strut fittings, and the notch that needs to be cut out to do that.

I see, well, without going into to many finite details there are some things that just have to be. Not many years ago, a fellow designed from scratch what he thought would be the  perfect ultralight engine. Gets down to the valve push rods, and decides the only way it will work is with bent push rods...  
I didn't know what to say to him...But as the saying goes, two wrong things don't ever make a right thing.