Design > Stunt design
Making Rib Sets
Ken Culbertson:
I have time on my hands so I know that either of the options I am asking about are not the most efficient approach but, I need to make a rib set for my own airfoil. It is basically the Thundergazer with an additional 1/8" thicker TE to house recessed flaps. I have two options.
1. Draw and cut out each rib individually which I can do but I would really like to find a cheap CAD program to draw them so that I can find someone to laser cut a set.
2. The old sandwich method which usually ends up with some tilted cap strips. Should I select this option, and it is looking like I will, I would like an opinion on something I have done once n the past. When I stacked the blanks, I did both sides at the same time then alternated the ribs inboard/outboard. This resulted in the inboard wing being approximately 1/32" thicker. To compensate I did not offset the centerline. I didn't notice anything different about how that plane flew compared to others with unequal spans but the same thickness.
Ken
Ken Culbertson:
--- Quote from: Motorman on June 09, 2021, 03:13:10 PM ---If you're making a true Thundergazer wing with the Warren truss ribs, stacking won't work. Also, it is very critical to line up the leading edge perfectly straight which is hard to do without the lost foam system.
Motorman 8)
--- End quote ---
No, it will be a classical "C" tube build with a molded LE. The Airfoil I have used since the 60's, with minor tweaking, is very close to the Thundergazer.
Ken
pmackenzie:
Have a look at Compufoil.
It is not that expensive, and simplifies a lot of the tasks involved in doing a set of ribs.
http://www.compufoil.com/product_cf.shtml
You can get the free version and play around with it to see if you like it.
Ken Culbertson:
--- Quote from: pmackenzie on June 09, 2021, 05:12:42 PM ---Have a look at Compufoil.
It is not that expensive, and simplifies a lot of the tasks involved in doing a set of ribs.
http://www.compufoil.com/product_cf.shtml
You can get the free version and play around with it to see if you like it.
--- End quote ---
Thanks, this looks like exactly what I want.
Ken
John Miller:
I've used Compufoil" for over 20 years now, and believe it's one of the best. There may be a bit of learning required but there are popups available, built intro the program. Over the years the program has gotten stronger, and more capable. The program comes packed with a huge airfoil selection. It also has a NACA generator that will allow you to generate nearly any NACA based airfoil.
With the help of the program you can modify any airfoil, almost any way you desire. I tend to use one of 4 airfoils for stunt use. a NACA 4 digit, a NACA 6 digit that I've modified, a Pathfinder "Ice Cream cone" Combat style, and an Eppler 169 symmetrical foil that seems very good. I can change almost every possible feature and can usually come within a pencils line width of matching most any airfoil. It is possible to enter in your own airfoil.
There are several very good options when it comes to lofting the wing. My most favorite lately has been the ability to create wings with the Warren Truss style ribs. I've lofted several true elliptical warren truss wings for a design I've been working on.
Getting the free version for learning on may be a good idea. If you begin to understand how it works, you'll want the fully loaded version I use. It is always update-able for free.
John Miller
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