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

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.

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

Ken,
Other option is to find a ship that is close enough for the wing style you want and order a set of laser cut ribs (Brodak has them for all their kits), then design around it for the ship you like. I have ordered several rib sets and it is well worth the money and time saved. Also could look at Bob Hunts lost foam approach as I think he could offer the core cut for the warren truss to give you rib templates.

Best,    DennisT

To do geodetic ribs you need the paid program, with the $21 lofting option add on.

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.

Is the $38 product stand-alone or is it an add-on to something besides a basic Windows 12 operating system?

If you use the sandwich method, try adding sacrificial spacers between each rib pairs. You will have much less bevel and less size variation.

For the spacers, I use two pieces of 6mm depron between each rib pair and you can use these for riblets to save waste.

Steve

   I think it was Charlie Reeves that advocated just making two sets of blanks for two sets of ribs, and store or sell the extra set. That solves the taper issue and if you decide to build another model or need to repair the wing you are one step ahead of the game that way.

    Type at you later,
     Dan McEntee

... The old sandwich method which usually ends up with some tilted cap strips. ...

This works if you're using a rod-type jig that makes it easy to flip the assembly before it's all built:

Cut the ribs any old how (sandwich, stack of templates, whatever).  Don't worry about a bits standing a bit proud.  Get the wing framed, then take a long sanding board and sand the tops & bottoms of the ribs flat.

Finish the wing.

For ribs with to much curve , or a curve at the end , rolling a dowel , round knife handle , or pencil , along the inside of the cap strip , with the palm of your hand , or suchlike , will ' pre curve ' em .
If its to soft it'll crush . So thicker sheet sometimes used , before  the big long sanding sticks applied  . But generally you get away with it .  Test a few before  you settle that dodge , stops em tilting
or droping the edges on real soft wood . Really wants something with grain , for cap strips .

Nuther dodge is ' pin stripeing ' brush - a little thing with say 1 inch bristles , from the art store , for pre doping ( fitted ) cap strips - as it tends to dope the outside & not the edges , wotcher dont want .

A old trick is last step to run sandpaper ( block ) along the cap strip etc EDGES . I think it was Bob Gieske , so as the tissue dosnt ridge / droop along em . Seems to work good .
Your just knocking the ' hard edge ' off . Bearly discernable , not ' radiusing ' the edge .