Rib Pattern Inaccuracy

[JohnS]

All

I taped the rib patter and found it to be way to large. Where I to build the spars to fit each would be 3/8" larger than shown on the plans. The front spar would be 7 1/4" according to the rib pattern. I am looking to get the iron design drawings anyway but I'm just curious what you'd do otherwise. Maybe shrink the copies until they measure correct and use that percentage for all pieces......then assemble?

[Tom XL-7]

John
I pulled my original set of drawings,  which is pretty much untouched other than having been fed through a copier. I measured  the front of the rib on the drawing where it would attach to the front spar.  I am actually a hair short of 6 and 7/8 inches which if I remember right is the target.  
If you are @ 7.25 I agree you are 3/8 ths too tall.  Are these copies or scanned and printed or some process like that that could have distorted them?
If so make new copies on another machine. If originals it would be best to get new copies whether you request them from Leonard or someone can scan and send you a set that you have the ability to print. Or order the full size drawing or Scott's set. If you have available a good copier; 95% should put you back-but-
 Regardless there are critical dimensions that should be held. The spar heights within reason and the distance between the spars.  A few other points.
 The ribs, spars and nose ribs must match up and will most likely require some adjustment on your part. I read and hear about the 10 degree bevel on the front spar and that may work out but I will make the top of my spar match up with the ribs and nose ribs. My nose rib was too short so I added to the top line until it matched up with what looked to yield a fair curve through the spar cap to the rib. There is also a an aileron end rib that once my rib jig was made was too short . I had made a template but have not cut any plywood.  I added to the tail of the template so it matched my rib jig.  


 Keep asking until your comfortable, sorry you ran into a snag. 
Tom XL-7

[JohnS]

These are the copies, but I measured the originals and they're the same. So my copies stayed true. I'm going to get Scotts drawings and maybe call Leonard to make him aware. I think it would be good if the dimensions were part of the plan set. Its really not that hard to draw curves. At least I found it easy with boat plans.

Thanks for the reply

[Tom XL-7]

Well now, If you can deal with boat building you can deal with this. I have not drawn this and it is for the legal eagle not the XL .  Someone may be able to confirm that they are all the same. This is from the yahoo group , in the files section forgotten and lonely near the bottom. "airfoil xls"

https://xa.yimg.com/df/EaglersNests/airfoil+coordinator.xls?token=5FYVyK__Y3nBdT3BK2LPYCrIAqB1djLGvXB8YD0OzcBne6JHJFt-D7oOkAmlqwewpudXFXUOBfo1jwdNyNrndq6_Bl0DiuPm6iqUUc1DqTtj7y2y4H3EAg&type=download

tom XL-7

[Tom XL-7]

That last message should have said I have neither drawn or checked that data. I guess it would be easy enough to check  but I don't have any 54" long paper. 
Oh that's right just tape a bunch of little ones together.
Tom XL-7

[Dan_]

This is from the yahoo group , in the files section forgotten and lonely near the bottom. "airfoil xls"

https://xa.yimg.com/df/EaglersNests/airfoil+coordinator.xls?token=5FYVyK__Y3nBdT3BK2LPYCrIAqB1djLGvXB8YD0OzcBne6JHJFt-D7oOkAmlqwewpudXFXUOBfo1jwdNyNrndq6_Bl0DiuPm6iqUUc1DqTtj7y2y4H3EAg&type=download

tom XL-7

Tom,
Yahoo will not let you link directly to them.  Direct links on yahoo turn out to be short lived "dynamic" links.  That is to say, if you put your link in your message at say 11:00, it may be good for an hour or so.   If you go back in an hour and copy the same link it will have a different "token".

Here is the same link just now:
https://xa.yimg.com/df/EaglersNests/airfoil+coordinator.xls?token=WCRQeIsO3PaVL7UxOZYAwoLxf2gHjM8Bl5V0La7RUSPqLiPdfMp7UbTdFjiFFAPN_r4YT5rlPbFB0UZ_XUKWOhWo9QvO59pTo28Rs91IqDRIurRVfxoSMw&type=download

I just downloaded to my box and included it below as an attachment...

Thanks for running it down for us.

P.S.  If you tried to attach it and could not, it was because the file type extension .xls was missing in the allowed attachments setting...  I just fixed that.

BTW: If anyone gets an error with an attachment give us a squawk about it...

[scottiniowa]

Hello folks, have read the various replies on the Rib Pattern question. And thought I should verify/quantify what I did.

In helping another several years ago, with the same question (or very similar) I decided to take the guess work out building a rib jig to supplied patterns. Am not saying what is  supplied is wrong, but just saying I decided to create a computer generated FULL scale  pattern-Full length as well.  I used published generation plot points for the airfoil ( you  may have seen these before as +/- position points above or below the cord line)  With these in hand, in CAD terms a spline line was created, thus the profile was generated as smooth as possible. 

What I gained for myself and others is simple.  10 minutes out of the box, one could lay the pattern down (there are two of them, so use either one) and could be making your rib building jig.  Or you could be making anyone of the full scale rib parts, knowing if  you later build the jig, the parts will fit perfectly.

Again, I did not change any part of the design, rather I just made things pretty clear, easy to use and cleared a path for progress.  If others that have the supplements, want to chime in, I guess this is the spot.

thanks,
Scott

[Tom XL-7]

I printed the airfoil coordinates this morning and placed them on the back side of a sheet of  waste 24x36 construction drawing.  One tape seam.  I do have a nice Starrett metal rule which measures in 10ths and 100ths. Too bad I don't have Starrett eyes to go with it. It is finer than my pencil marks anyhow. What's a sagging half millimeter here and there ? I used a nice straight 1/4 x 1/4 piece of wood using the "fair curve" technique common in wooden boat building. Clean straight grain to deliver a good shape is required. I actually used my nose rib template to connect the dots on the front. I cut it out and dropped it into my rib jig which was made from the plan sheets. 
 What did I learn. Frankly my rib jig is good to go. The only deviation was in front of the spar as my nose rib when placed against the drawn front spar needs to have the nose raised a bit. A slight cut on the top leg of the nose rib jig is all that is needed, the shape was good. 
 All in all, didn't take much time and I feel more comfortable with the confirmation if you will. 
 Tom XL-7

[Dan_]

Interesting tools here.  http://airfoiltools.com/

You can plot to your own printer...  25.4 MM to the inch.

Attached is one ready to send to a printer... 

Chord is 54 inches, grid is quarter inch square, paper size is landscape 8.5X11.

[JohnS]

I'm sure Scotts drawings will work well for me but these are nice too. Doesn't look like the bottom is as flat as I thought. I'm going to try to develops a table of offsets for it.

[Tom XL-7]

Hi John, But actually group.
Having just drawn this by hand but  in a quick and dirty method I have to say the legal eagle rib is flat bottomed.
While my methods were for the purpose of just seeing what the data produced I feel it is within a 1/16" everywhere. 
 The line you see in the plot is the chord. It is the longest line in the rib. It has absolutely nothing to do with wing incidence or the relative wind as it hits the flying wing. When you receive your one piece drawing please correct me if I am wrong.  That is actually the most important task of a group like this. Keep everyone safe and encouragement is always good too.
Tom XL-7

[Mrbill]

7 1/4 is what my patter comes out to as well.  I have tried a couple of times to see if I could get clarification from Leonard, but I haven't received any.  However the way I see it is, you just build the front spar to whatever height your rib is.  The plans are not CAD drawings and you have to adjust as you go.  Anyone care to weigh in on this?
Thanks,

[CHARLES DEBOER]

My drawing shows 6 7/8 inches for the rib and the front spar hight.  I built my jig to reflect the design dimensions.  The nose rib is dimensioned at 6 3/4 inches.  When you rap the .8mm ply (top and bottom)( 3mm = 1/8 inch aprox.) onto the nose ribs it comes out to 6 7/8 inches (allowing for some glue or epoxy) which blends smoothly up to the front spar hight.  This is a build to fit airplane design.  Just adapt your rib jig to the drawing dimensions and make adjustments. As you said these are not CAD drawings.  If you try to build to three decimal places you will be very frustrated trying to build this airplane.  Most of the time if you are within 1/16 or 1/8 inch you will be within the requirements to build it.  Your drawings were reproduced too many times.  Have Kinkos shrink them down or buy an accurate full size set from Leonard for $10 (read note on front page of your drawing set and on page #43).

[Mrbill]

Too late, already made 4 ribs... wish I had done that.  I'll just have to make adjustment to the nose and spar height as I go.  I would hope Leonard would make the correction for future builders!

[JohnS]

Mrbill

I was the one asking questions just before you, so I don't claim to know any more. But a 3/8 adjustment seems kind of big. I have no idea how it will affect things. No doubt you have to get comfortable with stretching a 1/16 or so but I'd say you'd want to limit adjustments. I think you'd do better to shrink the rib pattern to follow the stated spar dimension rather than the other way around. One is a solid dimension the other is subject to change during the copying process. Make sense?