Chrysalis 2M-E flights this past weekend and a bit of flutter - RC Groups
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Mar 08, 2011, 12:25 PM
Wood Chucker
Lacquerhead's Avatar

Chrysalis 2M-E flights this past weekend and a bit of flutter

I took out the Chrys2M-E on Sunday for a local fun fly after getting a 11x6 AeroNaut and a set of 3S 1800mAh batteries from Esprit. I would have to say that there is absolutely no comparison between the 1300mAh batteries with a 10x6 and the 1800mAh batteries with a 11x6. The 1800mAh batteries are able to deliver 45A vs the 1300mAh batteries being limited to about 18A. While that matches the T-bird 18 ESC I'm using the climb performance between the two is night and day. The 11x8 running full throttle for 30 seconds on the ground still leaves the battery, motor and ESC cool to the touch on a 60F day so I would be comfortable flying them in the Texas summers. I don't yet have an altimeter or ALES switch mounted in my airplane but I would say I am comfortably reaching 50% higher in 30 second than I was previously. I should be able to handily outperform the Radians that are common in the local contests. Of course if Barry Kennedy shows up with on of his hotrods I'll be toast but I'm just out to have fun!

I did have one problem though. I neglected to check my TX before I started flying and on one flight I had just gotten to altitude when the low battery alarm started chirping on the Tx. I pull the power out, popped the spoilers and pointed the nose down. Apparently I pointed it further down than I had in the past and it accelerated fairly quickly, pulled it out, circled a bit and repeated. The second time as I was coming down below about 100ft I saw the tail fluttering madly and basically lost all flight control. This is the first time I've ever seen any flutter on my Chrysalis so I am assuming I exceeded Vne. While I struggled to regain pitch control the plane nosed in at a fairly acute angle, bounced once and came to a stop. A quick control check, hand turn the prop a few times to check for obvious signs of damage but nothing is obvious. One *tough* bird. The fiberglass around the front firewall certainly helped my dumb thumbs.

Now my question. What can I do to minimize the possibility of flutter? Obviously, don't go so darned fast comes to mind. Are there preferred hinge methods to counter flutter?

I did continue to fly with a great deal of caution but had no further incidents. I did get to fly with a few migrating pelicans though. Occasionally some red-tailed hawks came out to play as well. Very, very extremely cool if I do say so myself. At the end of the day there were also several of us that watched a sparrowhawk hunting in the field we fly from. Again, very cool to watch those raptors do their business.
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Mar 08, 2011, 12:49 PM
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Don Stackhouse's Avatar
Biggest thing to check is your contorl linkages to the tail. Tin the cables at both ends (to make them stiffer) where they are outside of the yellow tube casings. Make sure the unsupported lengths are as short as possible, only enough to allow for pushrod travel. Make sure the pushrod casings are firmly anchored at both ends, and that they are adequately supported along their length. The ends of the casings are the most critical, but they should not be free to flop around along their lengths.

Make the horns as long as possible at both the servos and the control surfaces. This reduces the effects of slop, and wear in the horns. As much as possible, use mechanical adjustments (i.e.: control arm lengths) to adjust travel, not just dialing down the throw with programming changes in the transmitter. If you are only using a fourth of the possible travel in a servo, then you are also throwing away 3/4 of its resolution and possible stiffness.

Hinges are important, too, although historically the hinges have not been the worst contributors. However, if you are using covering film or tape hinges, make sure you have at least three places (both ends and one in the middle) where there is a patch about 1/2" long or so on the inside mating up with the primary hinge on the outside, so their sticky sides touch each other across the hinge gap. The gap itself should be about 1/64" wide.
Mar 09, 2011, 12:29 AM
Wood Chucker
Lacquerhead's Avatar
Why does it not surprise me that Don responded practically immediately. Thanks Don!

I'll tin my cables a bit further up. I did notice that it made them stiffer but for some goofy reason I was thinking that wasn't desirable. While I'm at it I'll reinforce the hinges as well. Thanks again Don. I sure to love my Chrysalis!
Mar 09, 2011, 08:09 PM
Registered User
Sailplanes are kind of slick and are capable of picking up a lot of speed in a dive(even with spoilers deployed). I have been lucky so far. I guess it is good to be inept at finding and staying with thermals.
Mar 09, 2011, 10:11 PM
Registered User
Spin it down next time...full rud and
Mar 10, 2011, 08:22 AM
Registered User
Don Stackhouse's Avatar
The other option on an electric is to pop the throttle open just enough to get the prop spinning, then pull it back till it's open just enough to keep the prop from folding again. The windmilling drag of the prop will help keep the airspeed down.

Many gliders, including the Chrysalis, are indeed quite "slippery" and will pick up a lot of speed when headed downhill.

However, there are some that are not, such as many of the old-style built-up models with their too-thick airfoils ("gas-bag floaters"), or planes with a lot of undercamber and/or too much thickness in their airfoil sections, such as some of the currently popular foamie sailplanes. These airfoil features can result in separated flow (particularly on the bottom) at high speeds, and a steep downhill flight path on these will only result in a limited speed increase. This can be a helpful feature for keeping a beginner out of trouble, but in the process it also destroys most or all of the plane's ability to penetrate. That is a serious handicap for practical soaring.

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