The most important thing is two things:

(1) Make sure the CG is dead-on!

(2) Do not exceed the recommended Elevator Travel throws until you've flown the airplane for awhile and are sure you really want more throw!

With these two items set correctly, the plane will fly beautifully.

NOTE: We do not recommend Exponential or Differential... Expo will reduce the "instant authority" and make it very difficult to trim/CG. Differential is pretty much useless on a flying wing/elevons, due to the quirkyness you would encounter on turns, adverse yaw, etc.

There are really only 2 causes for hyper-stall: An "off CG" and / or too much elevator input in light lift. In medium to heavy lift, and if the CG is dead-on, it's just a matter of making sure you don't have too much elevator or radical exponential throws. Once both CG and travels are dialed-in, you will quickly find that sweet spot where the plane snaps a turn and rockets out the other side!

Please CLICK HERE and scroll down to the 11/02/03 news post for the latest on Gooping. We rarely use the "Goop Only" technique anymore, so please read the info in the above link. For those that still want to Goop, the procedure is described below, as wriiten way back in 2003, while testing it:

2003: This is an alternate covering method we have been testing and seems to be working well. If you decide to use this method, and haven't yet built your wing, you might do the fuse goop procedure first, and let your fuselage cure in a warm to hot environment while you work on building the wing. This added cure time allows the goop to set up even harder.

Prep: Once the fuselage is shaped and smooth sanded, apply some "Lightweight Spackle" over the entire fuse, to fill all of the voids. When dry, very lightly sand smooth, without pitting any of the spackle. Now, if desired, spray paint the fuse any color you like (standard Krylon works well--nothing eats EPP foam).

Goop Applicaton: Standard "Household Goop" will work, though we prefer the "Marine Goop" (green tube), since it has a UV inhibitor. The Goop must be thinned to about the consistency of chocolate syrup. The thinning agent in Goop is "Toluene", which works best, and should be available at any industrial paint supply (Sherwin WIlliams, etc.). We have heard Xylene or Methyl Ethyl Keytone (MEK) also work, but have not done much testing with these. We usually mix ours in an empty glass "Relish Jar", so it can be sealed between coats, and when finished, to avoid evaporation and air-curing of the mixture.

Once the Goop has been thinned, apply it to the fuselage in long, smooth strokes with a medium sized brush, until both the outside of the fuse and inside of the airfoil cutout are completely covered--try not to go over the same area too many times with the wet brush, or the Goop will begin to bead up. Coats can be applied 1/2 to 1 hour apart, depending on ambient temperature and humidity... as we do more and more of these, we are starting to prefer anywhere between 10 and 15 coats of thin goop. If possible, for added protection against nose wrinkles and stress lines, you can also let the finished fuse cure in the sun, or a hot shed, etc., for several days or more. The goop will become even harder and more resistant to damage.

The entire method above not only allows you to spray paint the fuse any color you want (prior to gooping), but is much cleaner, way stronger and far more durable than strapping tape or Ultracote. For additional strength, we also use the same method on our tips and leading edges, prior to Ultracoating.

We've seen them go from kit to airtime in a day. We have also seen pilots spend a couple of hours a night over a week building their kit, and show up with a magazine perfect, finely trimmed masterpiece. If you absolutely have to be in the air tomorrow, and since "Goop" (which sets in an hour but needs to cure for 16-24) is a dominant glue used in the building, you may want to go through the manual first and kind of plot out drying time, etc. This way, you can be working on one part of the kit while the other is curing.

Also, given the precision of our kits, some of the work has already been done:

~ The wing cores and fuselage (Moth) have been cleaned and sanded to remove all of the wire slag

~ The balsa elevon material has been weight-matched within a few grams so you don't end up having to add a bunch of lead to the tip of one wing when lateral balancing

~ The flight and wing compartments on the Moth & M60 fuselages have already been pre-cut.

~ Everything has been cut to the absolute best tolerance EPP allows. This makes building go very fast, since you won't have to squish, smash, fold, spindle or mutilate, as the parts go together.

When using PU glue, we prefer to cut the balsa spar caps into six, 3" strips, 3 per side, and weight them down with elevated cross-bridges. This allows the excess PU glue to bubble over the top of the wing, inbetween the balsa pieces, without gluing the weight to it, as well as evenly distribute the weights, as needed. If fully covered with the balsa, the pressures from the PU glue can be very strong, and shove the spar AND cap out of the channel, curing above the airfoil, and the wing goes in the trash. It can be done as one piece, but is a bit riskier. BTW: Generally speaking, spar caps are, essentially, aesthetic only. With a properly installed spar system, they merely replace lost foam and allow reshaping of that portion of the airfoil.

Moisture is the standard catalyst to PU glue. It will probably harden without water, eventually (depending on how much ambient moisture there is in the air), but will only slightly expand, if at all, and it is best to mix a tiny amount of water with it.

After masking off each side of the spar channel (PIC 2) and lightly roughing up the carbon spar with sandpaper, test fit everything, including the spar, balsa strips, and bridge weighting system; when happy, remove and set within reach, layed out exactly as it will drop in (PIC 4).

Lightly wet out the channel with the brush* or dampened paper town, and squeeze in about a 3/16" diameter bead of glue, all along the channel (sorry, no pic for this... it's a long story!). Use a small aluminum plumbing solder flux *brush (about 20 cents at Home Depot), dipped in a Dixie cup of water (PIC 3), and mix the glue with the water, spreading it around the channel bottom and up on the channel walls. Dip the brush every 10 seconds or so of mixing; don't make it sopping wet, just enough to turn the glue opaque and get it to flow a little--this system makes for good expansion, yet xlnt strength to weight ratio. Wipe the spar system with a damp paper towel, drop it in, squeeze another bead of glue all along the top of the spar, and mix that with the dipping water brush, too, lightly filling in any areas that look like they may need more (the glue should already be foaming a little). Quickly, add the balsa, bridges and weights.

Keep in mind that, over 30-60 minutes, the glue will expand to many, many times it's volume; what might not look like much, can become huge. If any areas look drastically thin in relation, add a touch more. Ideally, when fully expanded, you want the glue to create a 1/2" high dome all above and along the spar channel, inbetween the weighted wooden spar pieces.

PICS: (5) (6) (7) (8)

Once cured, use a SHARP, serrated kitchen knife to cut it down close, then a plane, if available, then graduating sandpaper grits, finally flush with the airfoil, and remove the masking tape. Spackle fill the air bubbles when filling over the installed wires, Rx, etc. Let dry, sand, maybe repeat, done, strong!

PICS: (9) (10) (11) (12) (13) (14) (15)

Make sure you squeeze the glue to the top of the bottle before capping it, to preserve shelf life.

:)

Derek