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Author Topic: Wing ribs  (Read 12350 times)
Luis Strufaldi
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« on: June 22, 2015, 07:06:44 AM »

Hello

I'm trying to draw the intermediary ribs for a wing, having the root and tip profiles drawn.

I tried some LISP procedure that supposedly would interpolate between to curves, but since the procedure was designed for topography, the result looked like a doodle and not a rib.

How do you guys do it? Is there a simple process?

Thanks!
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Luis Strufa

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Avaiojet
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« Reply #1 on: June 22, 2015, 04:41:33 PM »

Hello

I'm trying to draw the intermediary ribs for a wing, having the root and tip profiles drawn.

I tried some LISP procedure that supposedly would interpolate between to curves, but since the procedure was designed for topography, the result looked like a doodle and not a rib.

How do you guys do it? Is there a simple process?

Thanks!

LCVS,

I'm told that this free CAD program will probably do what you're looking for.

The program that I was told to get, or the one that was recommended, is called, PROFILI.

Nope. I never elected to try it because my graphics program works quit well for any wing or ribs that I need to design.

I designed this wing in a short period of time with my program. Wasn't completely perfect, the placement on a few ribs were a tad short, but not all that shabby for a wing that has no two ribs the same in length or height.

Please let me know how you make out?

BTW. Many suppliers sell rib kits. You might find one that fits your needs.

"Good luck."

A line from the movie Taken.


* DSCN8727.jpg (75.5 KB, 783x588 - viewed 317 times.)
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Luis Strufaldi
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« Reply #2 on: June 23, 2015, 05:00:34 AM »

Thanks!

Indeed, there are a lot of "rib sets" on the market, but recently a friend came across a place with a laser cutter and we are trying our hand at making our own "laser cut" parts.

I long for the day where we will have a "lightsaber" model knife and will be able to just stack a bunch of balsa sheets between two templates and laser cut them the "old way"!  Layingdown Layingdown Layingdown

Will try the software you recommended and I'll let you know!
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Luis Strufa

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« Reply #3 on: June 23, 2015, 05:50:16 AM »

Thanks!

Indeed, there are a lot of "rib sets" on the market, but recently a friend came across a place with a laser cutter and we are trying our hand at making our own "laser cut" parts.

I long for the day where we will have a "lightsaber" model knife and will be able to just stack a bunch of balsa sheets between two templates and laser cut them the "old way"!  Layingdown Layingdown Layingdown

Will try the software you recommended and I'll let you know!

LCVS,

Please be advised, this program was recommended to me.

I'm actually not recommending the program at all, in fact, I'm just passing this information on to you.

"Ya got it!"

A line from the movie Galaxyquest.
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"I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King."

Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."

"I'd like to build a reputation, not be given one."
X-Files quote

"Ya gotta love it when a plane comes together."

Proverb 11.9  "With his mouth the Godless destroys his neighbor..."

"So popular, they named a television series after me."

"Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane."
David McCellan, 1980.

"If you can't rise above, you destroy."
Rush Limbaugh, 2015.
Luis Strufaldi
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« Reply #4 on: June 23, 2015, 09:11:47 AM »

Don't worry.

I'll try it and let you know how it works. As far as I could see, the program seems to be able to do what I need.
I'm just not too crazy about the price, it is a bit steep for a one time gig.

What really bothers me is that AutoCAD doesn't seem to have any tools to do it. Such a powerfull software and I can't find a way to just interpolate curves.

Oh well, back to the drawing board (literally!)
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Luis Strufa

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« Reply #5 on: June 23, 2015, 09:40:05 AM »

LCVS,

I thought that program was free?

 I must have the wrong program? There's a free program that's being used, so I was told.

Check some of the CAD Threads, you might stumble onto something interesting and useful.
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"I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King."

Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."

"I'd like to build a reputation, not be given one."
X-Files quote

"Ya gotta love it when a plane comes together."

Proverb 11.9  "With his mouth the Godless destroys his neighbor..."

"So popular, they named a television series after me."

"Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane."
David McCellan, 1980.

"If you can't rise above, you destroy."
Rush Limbaugh, 2015.
Luis Strufaldi
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« Reply #6 on: June 26, 2015, 06:41:17 AM »

Stil no luck, but I got in touch with Taniq and she is going to try to help me.
I'll let you guys know what the outcome is.
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Luis Strufa

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John Miller
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« Reply #7 on: July 21, 2015, 06:20:25 PM »

There is a method, used for years by hand draftsmen, before CAD.

At least one CAD guy I know uses it, with his CAD program to generate ribs for his drawings.

I believe the best, and most accurate lofting occurs when using one of the lofting programs, such as Profilli, Stunt Rib, or my personal favorite, Compufoil Pro. In spite of dedicated programs, the old lofting system. can create some reasonable rib sets, with a little practice.

You graphically use your drawing tablet like you were building an "I-Beam" wig.

You first generate your root curve. This curve represents the shape of the rib, on one side. The foll.owing can be accomplished either in CAD, or on the standard drafting table. It sort of represents the curved balsa strip rib used to construct the I-beam wing.

Next step, is to lay out the top view of the wing. You want to define the back side of the leading edge, with it's length, and 1/2 height . we also need to accurately locate the trailing edge piece, with it's 1/2 height.

Layout the rib locations, including any ribs located at odd lengths, such as supporting landing gear mounts. You'll need to loft.

We're basically looking to have an end view at each rib location.

Cad makes these steps easier, and more accurate, but most especially since the parts are in vector format, laser cutting files can easily be made that allow laser parts to be cut.

While all these operations can be done with hand drafting techniques, using Cad swill save time and effort.

Back to the process; Number each rib, and sub-rib location  before going any further. It will help keep track of things.

In CAD, You can grab and move the curved line.

Use the copy command to make a copy, grab it at the front end, move it, and attache to the front high point of the leading edge. You can repeat, make another line, and attach one to each rib sub station.

After all the rib sub stations have the line attached, you can take them one at a time, and use the command, rotate. Pick the end of the curved line where it intersects the back of the leading edge, anjd rotate the line until it intersects at the intersection of the trailing edge, and the 1/2 thickness. Trim the excess, and there you have it. a half rib split at the center line. Use the command mirror, and now you have the complete rib outline. A little more work, and you now have the complete rib set, lofted, and accurate.

Virtually  anyone, with a bit of practice can loft out a decent set of ribs, either using CAD or hand methods.
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Luis Strufaldi
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« Reply #8 on: July 23, 2015, 07:16:21 AM »

Quick update

First of all, thanks for all the info and software suggestions. Much appreciated.

I went the "low cost" road and employed a lot of elbow grease. Let me try to explain what I did.

First of all, I drew splines (curved poly-line) for the root and tip ribs (only the top half as they are symmetrical). Then I positioned then as they would be on the wing, i.e. aligned by the trailing edge. Next I used the divide command to place markers (50) on each rib and connected the corresponding points on each rib by lines. At this point the drawing began to look a by psychedelic.

Next I divided each line into 13 equal segments (again, divide command) because there were 13 ribs per wing panel. I color coded each of the 13 points in each line so as not to get lost.

The final step was just to connect this color-coded point with a new spline. If you don't make any mistakes, you end up with a set of perfectly spaced ribs.

I had to do this instead of the "i Beam" method that John suggested because the root and tip profiles were not scales down versions of the same airfoil, so in order to achieve a nice transition between then, I had to "average" the difference by using my "crazy lines method".

The results were the same, but next time I won't be so stubborn and shell out some cash for a nice rib software.

Thanks again, one and all!
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Alex Rillos
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« Reply #9 on: October 04, 2016, 08:47:06 PM »

Quick update

First of all, thanks for all the info and software suggestions. Much appreciated.

I went the "low cost" road and employed a lot of elbow grease. Let me try to explain what I did.

First of all, I drew splines (curved poly-line) for the root and tip ribs (only the top half as they are symmetrical). Then I positioned then as they would be on the wing, i.e. aligned by the trailing edge. Next I used the divide command to place markers (50) on each rib and connected the corresponding points on each rib by lines. At this point the drawing began to look a by psychedelic.

Next I divided each line into 13 equal segments (again, divide command) because there were 13 ribs per wing panel. I color coded each of the 13 points in each line so as not to get lost.

The final step was just to connect this color-coded point with a new spline. If you don't make any mistakes, you end up with a set of perfectly spaced ribs.

I had to do this instead of the "i Beam" method that John suggested because the root and tip profiles were not scales down versions of the same airfoil, so in order to achieve a nice transition between then, I had to "average" the difference by using my "crazy lines method".

The results were the same, but next time I won't be so stubborn and shell out some cash for a nice rib software.

Thanks again, one and all!

Thanks, Luis! Testei e funcionou muito bem. Parabens! Paulista e' bom mesmo! Grin Grin Grin
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dave siegler
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« Reply #10 on: October 05, 2016, 07:32:53 AM »

profili2 about $30 will do all this and put ribs in a dxf file and add all the LE, TE and spars.  You ought to look at that. 

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phil c
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« Reply #11 on: January 08, 2017, 07:34:21 PM »

I kind of use a combination of Luis' & John's methods, especially for complicated wings.  I've had trouble with both Compu-Foil and Profili handling spar layouts.
I lay out the desired airfoil.  Locate the spars, usually in pairs, but sometimes single ones top and bottom.  Separate all the curved sections either as splines or polylines.  The layout a front view of each spar location to ge the correct thickness at each rib.  I usually key off the front edge of each spar for consistency.
Then start at rib one.  Set the length.  Scale the airfoil to the correct thickness and length. locate the leading edge if used and the spars at each location.  If you haven't already, break the airfoil into pieces between the spars.
Repeat the process, starting at the front locating each spar, expanding the adjacent airfoil curve for the correct length and thickness.

I've had better luck using polylines this way than splines for curves when setting up foam cutting templates or laser cutting.  The laser cutter program(OEM) occasionally would decide to jump around on a spline or cut across it from end to end.  Polylines also let you make minor adjustments at corners and other fussy spots more easily.
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Alex Rillos
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« Reply #12 on: January 09, 2017, 08:32:00 PM »

Hello

I'm trying to draw the intermediary ribs for a wing, having the root and tip profiles drawn.

I tried some LISP procedure that supposedly would interpolate between to curves, but since the procedure was designed for topography, the result looked like a doodle and not a rib.

How do you guys do it? Is there a simple process?

Thanks!

I have a simple process which I have used for years. Works for ribs similar to NACA profile. I am attaching a PDF with an example and a spreadsheet to calculate the points for the trailing part. Any question just PM me. Alex

* airfoil-trail.xlsx (10.96 KB - downloaded 17 times.)
* Airfoil.pdf (47.33 KB - downloaded 24 times.)
« Last Edit: January 13, 2017, 07:05:49 PM by Alex Rillos » Logged

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