Warren Truss how to...
O.K. I posted a question earlier today asking about a "Webber Truss." 
Got lots of views and 2 repies which was kiondly explained by the first responder (Thank you!) whostragitened me out.
I saw a couple of planes recently with diagonal ribs in a truss form for strength and lighter weight.
I am interested in the strengeth part but would like to know more about how to figure it out.
O am guessing that one could take a regular rib, angle it relative to a strong light and trace the shadow to get the shape for an existing plane.
Are there any "rules" to follow or problems to avoid.
I appreciate all the help I can get.
Don't want to build and find out while flying "that wasn't a good idea."
Appreciate all responses.
Stunt Hangar people have been good to me
John Park (again)
Still in Flint MI
29443

There are several ways to do it, some more tedious than others.

1) Starting with the most tedious, you can draw the planform of the wing full size and measure the length of each angled rib, then plot the airfoil out the old fashioned way, which is xy coordinate system like a graph. The only difference would be that you'd use the thickness numbers for the straight rib, while using the exaggerated chord of the angled rib.

2) If you're a moderately competent computer guy, you can get a freeware or buy a software for airfoil plotting. Many years ago, I was loaned "Foiled Again" (and subsequently deleted it after I fooled with it awhile). It was not that difficult to make it work, even tho I didn't have the instruction book, was new to computers, and had some trouble with working my email. I could plot straight ribs for an eliptical wing, tapered, etc., no problem. It didn't put in structural members. I figured out that I could plot diagonal ribs by figuring out the diagonal chord and lying to it about the % of thickness. Profili is a program that is available for download from an Italian aeromodeller. I'm not sure if it's freeware or if it costs a bit, but I've read good things about it, and you can find it with Google. And then, the late Larry Cunningham created a software that would do diagonals and elipticals, specifically for stunt, with thick TE's for flaps, etc.  I believe it was called "Stunt Wing" or something like that, and Randy Powell has used it for a few years. I hope we didn't lose that with Larry's recent passing.

3) Once you get a computer involved, it's usually a short hop to getting laser cut ribs made, whether they be diagonal ribs or not.

4) Often, these Warren Truss wings are created using Bob Hunt's "Lost Foam" system. The foam wing core is simply sliced & diced at the rib locations, and the foam used as a guide for cutting ribs. The "shucks" or excess what doesn't look like a wing is saved and used as the building jig. Seems low tech, but it works very well for many Expert level fliers, as Bill 'splained.    Steve
 

I forgot to mention that you could (potentially) cut out your ribs as rectangles (say 2" high), glue it all together with the LE, spars & TE in the right places and then sand the sucker to shape with a long sanding board. Actually easier with a tapered wing, FWIW.  Steve

Here are two I did years ago using I/Beam construction. NO math,no plotting Just Do It. I have used it a lot on I/Beam wings. Please do not ask how to build a I/Beam wing. There are many threads on it.

Hey Bob,

You make molded leading edges for the Lost Foam wing don't you? I was trying to figure out a way to do it with the Tom Morris Millennium wing but it got to complicated so I just did it the old fashioned way.

Derek

Hi Derek:

Yes, I provide the leading edge mold bucks with all Lost-Foam sets. I can also provide them for wings built in other manners. I also do the custom molding of the leading edges in balsa (for a price of course... ).

Charles, to answer your question, I don't use any files to cut my foam wings and cores; I cut them by hand. Always have...

Later - Bob

The Lost Foam Fixtures are my favorite method of building built up wings, by far!  I have built several wings using the system and they all have come out super straight!

Second on my favorites list is I-Beam. 

BIG Bear
RNMM/AMM

As with anything it takes practice and I know Bob has had tons of practice.   I cut mine by myself and yes I did mess up a few cores.   The problem I have is finding a source of virgin foam locally.   So I go with laser cut ribs from a supplier.