Folding The Wing

NEW ADDITION : We have now begun using a heat gun or blow dryer to form the airfoil section.  You can quickly and easily form a beautiful airfoil by bending the top of the wing over an object while applying heat.   If you don't have access to one of these, then use the method below.

As I mentioned earlier, treatment of the top of the wing is important to getting a smooth airfoil.  Not that a slightly diamond shaped foil seems to matter on a good slope day, but it does in light lift.  So, to get the smoothest foil shape, open the wing panels so that you can lay the top flat.  Draw the same line you used to locate the former on the top panel (3" at the root 1-1/2" at the tip).  This will be a guide to let you know how far to go.

Using a yard stick along this mark, scribe, or crease the foam using a Bic pen top or some slightly pointed but round implement.  Space the lines 1/4" apart from that line to the crease of the leading edge, so that the entire length looks corrugated.  This will allow the foam to curve rather than bend at the high point of the former.  It does help to "exercise" this area a bit to loosen it up before joining the trailing edges.

With everything in place, test fold the section.  You will see that the leading edge tries to lift up as you fold over the former.  You must hold the leading edge down as much as possible when joining to get a nice flat wing with trailing edges that meet nicely.  If necessary, get two more hands to help you.  If the top and bottom trailing edges don't meet exactly, don't fret, because minor variations between my dimensions and yours will cause some variance.  You can either sand them smooth or use a sharp knife to get them to line up.  Either way, I bet she still flies!

I have used 5 minute epoxy, hot glue, contact cement, and poly glue on this joint and all work great.  Again, my vote goes to the hot glue gun because of its' ease of use and quick set.  Which in this step is a bonus.

NOTE : The top panels will most likely not meet in the middle, but don't worry about that.  You'll probably end up cutting the top all up to get your radio gear in anyway.

A note on wingtip washout and the dreaded "Death Spiral"

You can use this building opportunity to add in some washout to your wingtips if you like.  To do so, place 1/2" block under the wingtip (bottom) as you join the trailing edges.  The top will overlap the bottom but just trim it off even and it will stay in place.  This is ostensibly to prevent tip stalling and entry into the dreaded "Death Spiral" that wings are prone to.   WOW! Death Spiral…. that sounds bad?  Why YES it does!  But that's why we build 'em tough right?  RIGHT!

Well, you can reduce tip stalling several ways, one of course, is the "washout" method listed above.  We've also found that the following helps--in order of significance.

  1. Drooped Winglets-- First, what the heck is a DROOPED WINGLET?  I'll 'splain later on in this plan, but this is the single most effective thing we've done to kill tip stalling.  What does it do?  It's all highly technical stuff having to do with vortice generation and laminar airflows over abruptly terminating lift surfaces, pretty boring.  How do I know?  I spent A LOT of my parents money becoming an "aeronaut" in college and flying the real deal for several years.  So what do I do for a living now? I'm a computer geek… go figure!
  2. Round the leading edge of the last third of your wing--the relatively sharp bend of the fan-fold foam tends to cause the airflow to break away quicker from the surface causing a stall….. Oh geez.. Here I go again… sorry.  Anyway … a rounded leading edge helps the aiflow to "stick" to the wing out there.
  3. A combination of all these things.  Personally, I just crank through getting all my wings built and

ALERT! Oh Noooo… not AGAIN!

Oh C'mon… it's not THAT bad.  Besides, the next page has lots of pictures and they take up lots of room and just wouldn't fit here.  And this is more about y'all  folks out there anyway.  I've found for the most part, that R/Cer's are a pretty good group of very knowledgeable folks.  I never cease to be amazed about the amount of information that you guys are willing to share about all manner of different things,….. Electronics, airframes, motors, whatever…..   It's been really nice to be able to give a little back with posting these plans on the Web.

Granted, there are a few Putzes out there that complain and bitch about little things you left out or misspelled or mis-quoted or somesuch.  Oh well, it takes all kinds to make the world go 'round and I guess we gotta put up with the bastards sooner or later anyway…...