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Old Yesterday, 02:25 PM
The earth sucks! Thankfully.
United States, OK, Tulsa
Joined Jun 2003
429 Posts
Older Mk II Kit and Changes

Don S. and all of you 2m Chrysalis fans:

I starting to build my 2m Chrysalis Mk II. It's an older kit ordered from DJ Aerotech 6 to 8 years ago. I see the V tail parts have holes in them now. What other changes do I need to be aware of? Do I need a newer copy of the plans or instructions?

- Jim
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Last edited by JimHSoars; Yesterday at 02:27 PM. Reason: Added a title.
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Old Yesterday, 02:37 PM
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United States, MN, Buffalo
Joined Jan 2007
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I would glue those holes in place, as i removed the holes,and the structure factor on the feather end needs the extra rigidity. opened my "baby" C- I need a straight line progress bar!
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Old Yesterday, 04:38 PM
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United States, OH, Bradford
Joined Jun 2005
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I have a call in to Joe about your tail. We have always shown the lightening holes in the tail (including on the original version), but AFAIK, we have NEVER pre-cut them, and we do not recommend putting them in. They are strictly optional. We only show them on the plans at all because some old-timers insist they like the look of an open framework tail, and as long as they were going to chop holes in the tail anyway, we might as well give them some guidelines to avoid chopping too much. They do not save enough weight to be worth the trouble or the loss of strength, and we do not recommend them unless you're dead-set on having a tail you can see through.

If you have the MkII version (easy to spot because it has the diagonal bracing on the inboard wing panels, and the bolt-on option for mounting the wing to the fuselage), you should have everything you really need in the way of plans and instructions. There have been some tweaks and corrections here and there since then, but not enough to be worth replacing the set you have. It is worth browsing through the various build threads here on RC Groups, there is a lot of good info and worthwhile hints, as well as discussion of things that folks thought might be good, but turned out to not work so well in practice.

The big thing is to check with me if there is anything you don't understand, or if you are considering a mod to the kit. Most of the proposed mods turn out to be a bad idea, but a few good ones have shown up over the years. However, there are reasons for most of the details in the way the plane is designed, and you could end up painting yourself into a corner or worse if you change something without knowing those details. The only truly dumb question is one that you should have asked, but didn't!
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Old Yesterday, 05:46 PM
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Joined Feb 2009
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I thinking about the Hyperion motor for my Chrysalis: http://www.soaringusa.com/Hyperion-G...P-2213-14.html

It took a while to run down the specs but it looks to make around 300 watts depending on prop and weighs 68 grams. Any advice?
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Old Yesterday, 06:52 PM
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United States, OH, Bradford
Joined Jun 2005
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That's about half the motor weight the plane was designed for, with a higher Kv than optimum. You would need to run it on 2 cells in order to get a decent sized prop and reasonable prop efficiency, and you would need to extend the nose, or you will probably have C/G problems.

Saving weight in the motor means adding a greater amount of ballast further aft than the motor to get the C/G correct (unless you stretch the nose, which can create other problems). The net result is that a lighter motor makes the plane heavier.

We've been getting excellent results from a Himax 3522-0700 on three cells, with a 12-7 prop (or thereabouts). We get those motors from Radical RC, although other folks should have them as well. Weight is 5.7 ounces, almost identical to the MP Jet 28/20-7 we originally designed the plane around.

Esprit Models has Aeronaut folding props, also excellent.

We avoid APC folders, we've had serious structural problems with them, cost us a UAV prototype worth several thousand dollars. Brand new prop failed in flight after 10 seconds total running time, due to an internal manufacturing defect in a blade ( hidden cracks inside the blade root due to differential cooling patterns in the mold). The resulting unbalance shook the airplane apart. The power and RPM were well below what the prop was supposed to be good for. YMMV
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Old Yesterday, 09:42 PM
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O'Fallon, Mo.
Joined Apr 2010
541 Posts
Progress Report

Spoilers repaired and functioning properly. I am getting 45-degrees of deflection at full deployment; sound about right?
Mounted rudder/elevator servos today, just about mid-wing cord. ALES aft and Rx ahead of RE servos. ESC and 3S-2200 under the hatch. With battery as far forward as I can get it, the CG is mid-range. AUW=36.66oz.
Getting close now!
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Old Today, 12:03 AM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
3,290 Posts
If the plane is nose heavy, can't you just move the battery pack back?
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Old Today, 07:04 AM
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O'Fallon, Mo.
Joined Apr 2010
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That is true Tri.
In my case I can get CG into mid-range with the battery full forward, and shift it aft moving the battery aft. That is most likely what I'll do as I get familiar with the plane.
But I can't move it forward without weight, and I'm not sure where I would put it! Fortunately, that is less likely to be necessary.
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Old Today, 09:47 AM
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Joined Feb 2009
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Thanks for the reply Don. I do understand the problem as I am building an eSupra that has a really long nose and a heavy Neu motor upfront. Could you advise the issue with extending the nose on the Chrysalis?
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Old Today, 10:03 AM
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For intermediate/experienced fliers, the plane seems to handle best with the C/G about 1/16" in front of the aft limit. Blulls, you could probably get away with moving the C/G aft a bit from where you have it now. Static stability will be weak but positive, and the plane will hold thermal turns better.

Randy, there are theoretical issues (static and dynamic stability in particular, due to the stability effects of props mounted ahead of the C/G) with making noses longer, although in actual practice in this case they are not particularly significant.

I've put together some guidelines for extending the nose if you plan to use a motor significantly lighter than the plane was designed for. Doing this does complicate building, and potentially can weaken the nose. It's more of a compromise for contest fliers, one reason why we did not just make the nose longer in the stock kit.

The plane was designed for a motor weight around 5-6 ounces. If you're going to use something half that weight, you will probably have an easier time getting the C/G if you lengthen the nose. The fuselage doublers need to be lengthened, but the kit already has extra length in the balsa sheet for the fuselage sides and bottom (we use the same balsa for the electric that we supply for the pure sailplane fuselage), so no changes needed there. Basically, it involves making a scarf cut in each doubler per the attached diagram, gluing in a 1/8" Lite Ply section (make the grain direction the same as the grain in the doubler), then applying glass tape and epoxy to the splice joints on what will be the inside surface (no reinforcement needed on the outside surface of the doublers, the balsa fuselage sheeting there will provide enough reinforcement).
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Last edited by Don Stackhouse; Today at 10:23 AM.
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