A fellow I met on RCSE (Jerry) just finished a Chrysalis Two Meter and it has standard covering on the wings and weighs in at 32.5 oz a little over the 26-27 oz advertised weight.

This is not a problem but what concerned me is his comment "I suspect the standard weight is useful for added strength, because the wing does flutter when launching into a good headwind." I have seen Chrysalis HLGs have a flutter when used with a mini high start unless you keep the nose up to almost popoff angles. I am concerned because the wind does blow here. Ideas?

From : Don Stackhouse

The Chrysalis 2-meter is quite a bit different from the HLG version, particularly with regard to torsional stiffness. The 9/16" wide full box spar of basswood and 1/32" birch ply is in a different league altogether from what we have in the HLG. That said, it still isn't a D-tube, and so it doesn't have a huge surplus of torsional stiffness. It was designed to compete with the likes of the Gentle Lady, the Riser, the Kestrel and the Spirit, flying mostly off of a hi-start. If you try to treat it like an F3B model, it will start trying to discuss the matter with you in no uncertain terms!

Like the HLG Chrysalis, we wanted to keep it easy for beginners (thus the specification for a dowel leading edge and no leading edge sheeting). The torsional stiffness is adequate considering its intended purpose.

The choice of covering material has a large influence on torsional stiffness. The best we've found in this regard is good old fashioned transparent Monokote. It's a little lighter than Ultracote and Oracover, and noticeably stiffer as well. Of course this does make it a bit more brittle, so if you plan to do a lot of lawn-dart landings it might be better to give up a little flutter resistance and use regular weight Ultracoat. We do not recommend the lightweight Ultracoat or Oracover for the wings, although you could probably get away with it for the outer panels. The lightweight coverings should work OK for the fuselage and tail. Considering the beatings and abuse that 2-meters seem to get routinely subjected to, we don't recommend Varathane alone for the fuselage and tail. With 5.02 square feet of wing area, the weight savings isn't that significant.

32.5 oz. is quite portly for a 2-M Chrysalis, my guess is he used too much glue, or beefed up something that didn't need beefing up, or put too much paint on the tail and needed extra lead in the nose. In any case, the wing loading is still quite low at that weight, it's total weight is still lighter than most 2-meters, and it should fly quite well. Joe Hahn had his at a local RES contest Sunday ballasted up to almost that weight, and found that he had quite a bit of additional searching ability with very little tradeoff in thermalling ability. We fly the Speed 600 electric prototype at between 41.5 and 46.5 ounces (depending on battery size) with very good results. Wing loading in that mode is from 8.27 to 9.26 oz./sq.ft.. Needless to say, penetration is not a problem (I have no trouble at all penetrating 20 kt. winds at 26 oz. with the sailplane version), but it still thermals fine at that weight.

As far as hints and mods, you do have a lot of wind out there so it is definitely a valid concern. So how exactly do we go about transforming this simple, all-wood sport model into an armor-piercing, gale-force winch rocket?

If you want to add some serious extra durability and stiffness to the fuselage and tail, a number of folks have reported good results from applying 1/2 or 3/4 oz. glass using Varathane instead of epoxy. If done right, it adds very little extra weight, but a huge amount of strength and stiffness. If you add it with a +/- 45 degree fiber orientation to the tail boom and tail surfaces, it will help their torsional stiffness (and therefore their flutter resistance) tremendously.

If you're planning on a lot of winching in gusty conditions, I would be concerned about both flutter and sudden high bending stresses in the wing. You might consider adding some carbon to the inboard main spar caps (probably about .014" on top and .007" on the bottom), then wrapping that with some 1 oz. glass, preferably on a +/- 45 degree orientation. This will help both the bending and the torsional properties. Don't forget to use carbon instead of the 2" spanwise glass tapes over the main spar caps at the center section joint. For additional torsional stiffness, you might try adding some 1/64" ply shear webs to the rear spar as well. Diagonal struts of 1/16" x 1/8" spruce or basswood top and bottom between the leading edge and the main spar, and the main spar and the rear spar could also help. Lots of extra work, but it would add a lot of stiffness for a small amount of extra weight.

One other wing option, you might find it easier to put a small servo on each spoiler out in the wing, rather than running linkages from both spoilers to the single spoiler servo in the center section. With no spoiler in the middle, you can close up the notch in the bottom of each "A" rib, leave the bottom sheeting in the center section intact, all of which makes the forward part of the center section stronger. You then also have the option for differential spoiler to assist roll control, in case you need more roll authority in turbulence. Illegal for RES contests, but perfectly OK for sport flying or regular TD contests, and it's not much trouble to switch back to pure spoilers only if necessary.

As long as you're adding all this to the wing, you probably should add some .007 carbon to the tail, diagonally from the leading edge at the fuselage to just ahead of the hinge line at the tip, on both the top and bottom. This will help the torsional stiffness of the stabs, another flutter prone area. Of course if you tried the 1/2 oz. glass and Varathane on the tail, the surfaces might be stiff enough already. Depending on your taste in C/G and towhook locations, you may also want to add some extra reinforcement to the joint at the roots of the stabs; a well-aft or well forward towhook or C/G can subject this joint to some very high bending loads.

Use .032" music wire for the tail surface pushrods. You'll need to make a splice under the wing to make the pushrods long enough to reach servos in the nose, make sure you keep the pushrods very straight in the vicinity of the splice. Use the outermost hole on the control horn, and make the arm on the servo longer if you need more travel.

You will aslo probably want to use a bolt-on wing attachment. We've heard one or two reports of folks with heavy feet on the winch peddle pulling enough line tension to overcome the rubber band tension, causing the wing to lift off the saddle and slip aft a little bit! Of course a few extra rubber bands and some wing saddle cushion might also be a good solution.

Those are all the mods that come to mind for now. The 2-meter Chrysalis isn't a silk purse, but neither is it a sow's ear. It's a good, basic, fun model. It works very well for its intended purpose, still works surprisingly well for some unintended purposes. With a few good mods it is possible to make it better suited for some extreme applications.

Don Stackhouse
DJ Aerotech