US35b Full size print out
- Thread starter tcraft128
- Start date
D.A.
FRIEND
Free America
You probably already know this but the Wag Aero airfoil is different than the Piper airfoil. You are correct, the Wag airfoil is the US35b, while the Piper is "Modified".
Your project is awesome!
D.A.
mike mcs repair
Registered User
chugiak AK
and WHICH version of piper rib sizes/shapes do you HAVE to repair?
bothering to make a print that's 3/8" different from your ribs you got might not be to useful for you.....
D.A.
FRIEND
Free America
That's why I bought a Dakota rib. Nice crisp line to lay the jig airfoil out with. I had an original Piper rib for the trussing.
Bugs66
Registered User
Spokane WA
I was able to scale the rib drawing full size using Photoshop. I attached here but will put a copy in my drawings site soon. The drawing size is now 36x72 so you will need a plotter for sure. Make sure you turn off any scaling when printing this PDF. If anyone prints this let me know if the dimensions are ok. As far as I know they are.
View attachment 13814_rib_full.pdf
View attachment 13814_rib_full.pdf
D.A.
FRIEND
Free America
I did the exact thing Bugs. I attached the 12183 drawing from your website to an email and sent it to our local OfficeMax. I called them, asked them to print it on their 36" printer and it was done when I got there. Thanks for having the resource available!
MainlandCub
Registered User
New Zealand
You're really heading off in the wrong direction. Never scale off drawings. That is a hard and fast rule from those of us from the pre-CAD age.
Bugs' drawing has the co-ordinates on it. Plot that out on the piece of board or whatever you're using for your rib jig. If you can't do that, buy a rib from Dakota or Univair and build your jig around it. That's all I did with a good Piper rib.
Seriously if even if the Piper draughtsmen drew that profile out accurately and without error, the scanning will have distorted it for sure, no matter what machine was used.
I hope that helps.
Cheers,
Andrew.
Bugs' drawing has the co-ordinates on it. Plot that out on the piece of board or whatever you're using for your rib jig. If you can't do that, buy a rib from Dakota or Univair and build your jig around it. That's all I did with a good Piper rib.
Seriously if even if the Piper draughtsmen drew that profile out accurately and without error, the scanning will have distorted it for sure, no matter what machine was used.
I hope that helps.
Cheers,
Andrew.
canopyflier
Registered User
Minnesota, MPLS area
Is there and advantage to having the "Modified" airfoil over the US35b?
Dave Calkins
Registered User
Anchorage, Alaska
I like the straight '35B better, I think.
Would love to hear what the smart-guys have to say about the "advantages" of the "modified".
.....? DAVE
Would love to hear what the smart-guys have to say about the "advantages" of the "modified".
.....? DAVE
D.A.
FRIEND
Free America
I'm not an expert by any means, but I don't think there is a standout advantage to either airfoil. Here's a link to the thread where I compared them one on top of the other:
http://www.supercub.org/forum/showthread.php?39427-Chris-amp-D.A.-s-SC-Build/page2&highlight=chris
If anything, with the higher camber, I'd say the Wag airfoil is probably a higher lift airfoil. The airfoils are very close, but they're "Just different enough" that you can't mix and match them. Chris and I went with the Piper version because of all the research and support and ready replacement parts that are available. Other than that, I wouldn't think there would be much difference. Just my 37 cents worth.......
SpainCub
Registered User
Hi,
Here is a files I picked up somewhere (I can´t recall where) but it was nicely drawn by Keri-Ann Price.
I will be emailing her soon to see if she could come up with the 613.5 Airfoil fully drawn as this file...
BTW Bugs file measures out if you print, but this file will give you better lines to work from.
http://www.j3-cub.com/forum/attachm...-usa-35b-modified-piper-dwg-13814-airfoil.pdf
Ok, so I could not find the file on this computer, but I did find the link where I had gotten it.
http://www.j3-cub.com/forum/f88/some-small-progress-my-j-3-wings-21816/index12.html
We should try to get her to build a PA-18 or a Wag Areo 2+2, she could be very resourceful.
All the best,
Here is a files I picked up somewhere (I can´t recall where) but it was nicely drawn by Keri-Ann Price.
I will be emailing her soon to see if she could come up with the 613.5 Airfoil fully drawn as this file...
BTW Bugs file measures out if you print, but this file will give you better lines to work from.
http://www.j3-cub.com/forum/attachm...-usa-35b-modified-piper-dwg-13814-airfoil.pdf
Ok, so I could not find the file on this computer, but I did find the link where I had gotten it.
http://www.j3-cub.com/forum/f88/some-small-progress-my-j-3-wings-21816/index12.html
We should try to get her to build a PA-18 or a Wag Areo 2+2, she could be very resourceful.
All the best,
Darrel Starr
Registered User
Plymouth, MN
Here are some great references to airfoils. Covers just about every plane built.
http://www.ae.illinois.edu/m-selig/ads/aircraft.html
http://www.ae.illinois.edu/m-selig/ads/coord_database.html#T
The web site has the USA35B but not the "Modified USA35B" as used in Pipers.
http://www.ae.illinois.edu/m-selig/ads/afplots/usa35b.gif
http://www.ae.illinois.edu/m-selig/ads/coord/usa35b.dat
http://www.ae.illinois.edu/m-selig/ads/aircraft.html
http://www.ae.illinois.edu/m-selig/ads/coord_database.html#T
The web site has the USA35B but not the "Modified USA35B" as used in Pipers.
http://www.ae.illinois.edu/m-selig/ads/afplots/usa35b.gif
http://www.ae.illinois.edu/m-selig/ads/coord/usa35b.dat
fobjob
MEMBER
Salt Lake City, Utah
Here's the wind tunnel data, anyway.. http://www.supercub.org/photopost/showphoto.php?photo=28113&title=usa-35b&cat=500
skywagon8a
MEMBER
SE Mass MA6
This is very interesting. It shows that the stall angle is just below 20 degrees. I would not have suspected that it would have been that high. My guess was that it would have been nearer to 16 degrees. I think that I shall make a angle of attack indicator on a pole mounted on the wing. Perhaps I'll also fit a floating pitot tube to the same pole? The results should get us into some interesting conversation.
The AOA of the USA35b and USA35bMod were referenced to the bottom of the wing, not the chord line as is done now. That's the reason for the seemingly high stall angle.
The coordinates of the USA35b are screwed up at the leading edge radius. There are also discrepancies between different Piper rib drawings (false rib and full rib noses are shown different -- they aren't). There are quite a few mistakes in the Piper wing drawings.
The coordinates of the USA35b are screwed up at the leading edge radius. There are also discrepancies between different Piper rib drawings (false rib and full rib noses are shown different -- they aren't). There are quite a few mistakes in the Piper wing drawings.
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Any chance of naming those errors or at least the ones you remember?
SpainCub
Registered User
Please share which drawings you are referring to and what errors you have found? I am reviewing and redrawing some of the wing parts based on both Piper and Wag Areo drawings, so your feedback would be greatly appreciated.
I think that one of the many issues with the Piper drawings are the revisions, they are not all there... what I am trying to do is get the latest rev, then used that as a base for parametric relationship of the parts, ad you stated the false rib is something I was looking into.
BTW, can you clarify your comment of high AOA? I am not following you there... (I know it's me... so can you be so kind to please explain this further with a bit more detail? :roll
+1 Caught me typing and walked away thinking I had posted, then saw your post!!!
Longwinglover
Registered User
Charlotte, NC
OK 25 posts of people giving their best guess. Let's go to "the" source, Clyde Smith, Jr. - The Cub Doctor. Quoting from the Sept/Oct 2005 Cub Clues newsletter A Study of Piper Ribs Clyde says in part:
"All fabric Piper ribs employed one airfoil design, the USA 35B, but were modified by increasing the upper coordinates by 4%. Thus the terminology "USA 35B Modified" was the typical description of the Piper rib and the chord was 63 inches. All the ribs were similar from the J2 through the PA-25 Pawnee.
...
In my weekend siminars, I divide the wings into two classes, the "Cruiser Wing" and the "Cub Wing". The Cruiser wing was used on the J4, J5, PA-12 and PA-14. The Cub wing was used on the J3, PA-11, PA-18, PA-25 and all the short wingers. The differences here were that the Cruiser wing had the "S" or "Sloped" type of false spar and had a stamped nose plate rivited into the leading edge or nose section of each rib, rather than the individual truss type bracing.
...
The Cruiser wing panels did not have the short nose rib sections between each main rib either
...
The Cub type wing had the concave type false spar and the nose of each rib had the individual brace members. These wings also utilized the short nose rib sections, forward of the main spar, between tha main ribs."
John Scott
"All fabric Piper ribs employed one airfoil design, the USA 35B, but were modified by increasing the upper coordinates by 4%. Thus the terminology "USA 35B Modified" was the typical description of the Piper rib and the chord was 63 inches. All the ribs were similar from the J2 through the PA-25 Pawnee.
...
In my weekend siminars, I divide the wings into two classes, the "Cruiser Wing" and the "Cub Wing". The Cruiser wing was used on the J4, J5, PA-12 and PA-14. The Cub wing was used on the J3, PA-11, PA-18, PA-25 and all the short wingers. The differences here were that the Cruiser wing had the "S" or "Sloped" type of false spar and had a stamped nose plate rivited into the leading edge or nose section of each rib, rather than the individual truss type bracing.
...
The Cruiser wing panels did not have the short nose rib sections between each main rib either
...
The Cub type wing had the concave type false spar and the nose of each rib had the individual brace members. These wings also utilized the short nose rib sections, forward of the main spar, between tha main ribs."
John Scott
behindpropellers
Registered User
NE Ohio
I would be interested in milling out some jigs for you guys.
I'm not sure what the demand is but if people wanted 10 or so Jigs built I would do it.
Thanks
Tim
I'm not sure what the demand is but if people wanted 10 or so Jigs built I would do it.
Thanks
Tim
I'm installing tile in the washroom today. Will get back in more detail later. In the meantime, as just one example, on different Piper drawings, the leading edge radius varies between 1.00 and 1.39 inches, and the radius point moves around. Just aft of the radius point on the top surface there are mistakes in the listed coordinates that make the upper front surface too flat. This has adverse effects on the stall characteristics of airfoils built to the coordinates shown (Piper didn't always build to the drawings).
fro
Note the zero reference line in Post #20. In modern wind tunnel work, the aoa is referenced to the chord line (a straight line drawn through the trailing edge and the radius point of the leading edge radius). In older airfoils like the 35b and 35b Mod, it was referenced to a straight line drawn from the trailing edge tangent to the lower surface of the wing. That makes the stall aoa of these older airfoils seem to be several degrees higher than it would be in modern usage. just subtract the angular difference between the two reference lines to adjust the old wind tunnel data to modern usage.
fro
Note the zero reference line in Post #20. In modern wind tunnel work, the aoa is referenced to the chord line (a straight line drawn through the trailing edge and the radius point of the leading edge radius). In older airfoils like the 35b and 35b Mod, it was referenced to a straight line drawn from the trailing edge tangent to the lower surface of the wing. That makes the stall aoa of these older airfoils seem to be several degrees higher than it would be in modern usage. just subtract the angular difference between the two reference lines to adjust the old wind tunnel data to modern usage.
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Thank you Jim. Probably 20 people looked at your original post and twenty different worries came up. In my case I was worried that some hole location in the spar was off or a bracket was called out in the wrong place or missing. The thread is about rib design and I forgot that for a moment. There are so many types of builders from "order a kit" to Marty 2+2 (the only thing he didn't do was chop the trees down and brew the glue). We draw from various sources and are willing to spend different amounts on "plans" and parts. For some reason I'm determined to use strictly the free plans from Buggs site so those are the ones I worry about. I finally bought my ribs from Dakota after the pedigree of my "garage sale but new ribs" came into question.
