Building a vertical spar in a foam wing.

Ok, so, one of the method to put a spar in a foam wing for gliders, is to insert a vertical spar, usually made of plywood. A long time ago, we use to cut the wings in foam, then slice them all the way and glue the spar to "re-join" the wings halves together. Then, sheeting etc, the usual.

The problem doing it this way (well, not really a big problem, but still!)was that most of the time, filler was needed along the spar to have the profile being smooth again. Heavy, and the profile"rightness" was hard to achieve.

With cnc machines, profiles are even more accurates, so here is one of the way to insert a vertical spar in a wing, without losing much of the profile rightness.

Images are worth a thousand words, so here you go. 5 simple steps, easy!

And that's it.

 Of course, you can add some carbone / fibreglass to create a T or I spar.

Note that at the root, you can then glue the wing joiner box to the spar directly, or even integrate the box to the spar itself... But that's another story!