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#35 Model Airplane Building Clinic >> DJAerotech Chrysalis 2m Electric Sailplane

Old 10-29-2012, 01:45 PM
  #101  
Don Stackhouse
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Yes, we've been fighting that problem since right after the original Chrysalis went into production. It took a lot of detective work to find out that the $10,000 digital plotter used by the folks who print our plans for us has a calibration problem. Apparently none of their other customers use their prints as a building template. We ended up giving them a piece of trailing edge stock as a calibration standard, and training their operator to check for this, and for a while the problem was under control. Unfortunately they have things like employee turnover, moving to new facilities and corporate mergers complicating things, and the problem kept coming back. It's like trying to nail jelly to a tree.

Make the ribs parallel to the lines on the plan, but use the shear webs and trailing edge notches to determine their location.
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Old 10-29-2012, 09:04 PM
  #102  
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I had seen this mentioned in another thread somewhere, so I was aware of it and wasnt surprised when i seen it and doing as you described it wasn't a problem at all. The wing is going together nice.
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Old 10-31-2012, 03:49 AM
  #103  
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More progress the last couple of days. Some trial fits of the tail went well. When the tail is the same height on each side it also sits straight as measured with string from the center of the rear wing area. So I glassed the tail joints then mounted the tail to the fuselage.

Tonight I added the filler pieces on the bottom of the tail and applied the last of some fiberglass/epoxy tape for strength. This completes the major structural build of the fuselage. Next is figuring out the location of all of the electronics so everything balances.

Steve
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Old 10-31-2012, 04:12 AM
  #104  
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It's looking great Steve.
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Old 11-01-2012, 03:01 AM
  #105  
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I put a piece of blue tape on the fuselage to mark the recommended CG range according to the plans. I then used a string to find out where it balances. With nothing installed, the plane balances at the rear of the wing. (See pictures 1 and 2)

With the components installed and the servos towards the rear, it balances perfect. There will be some more weight towards the rear when covering is added and the control horns and connectors are added.... So the servos will probably end up in the forward compartment. Final placement will wait until after things are covered.

The fuselage, motor, spinner, speed control tail servos, receiver, and push rod wire weigh 14.5 ozs. So hopefully the completed fuselage will be well under 20 ozs. The wings are big, but shouldn't be too heavy, so hopefully I'll hit my target of 30 oz without battery.

Next... Building the wing!

Steve
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Old 11-01-2012, 12:49 PM
  #106  
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Looks real nice Steve. Watching for the wing.
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Old 11-01-2012, 09:25 PM
  #107  
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You have done this a lot haven't you Steve ?
George
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Old 11-02-2012, 03:28 AM
  #108  
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Originally Posted by Dimeflyer View Post
You have done this a lot haven't you Steve ?
George

Actually no... The planes in my signature are the only RC planes I have. (Well some combat foamies too...) I have only been really into RC planes for 4 years now. There are others here (like Paul (pd1)) that are "real" builders. I used to build rubber-band free flight planes growing up with my dad and did some Cox 049 control line planes when I was 13 or 14. I always wanted to get into RC planes and have always loved planes in general, but I haven't made the plunge until recently. I'm now hooked!

One of my goals is to try at least one plane of every type there is.. So this is my first glider.

Steve
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Old 11-03-2012, 04:55 AM
  #109  
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Verry interesting guy
I still build stick and tishue rubber powered planes between the rc planes but just realy got into the all foam building but am not good at it so I fell like a new builder at this type of construction .
You seem to be verry good at the sailplane building guy , if I can get 1/2 as good
at the foam I will fell good !
George
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Old 11-03-2012, 09:28 PM
  #110  
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Default 1/16 Sheeting Question

I am just starting on the wing. I switched out the floppy movable 1x1 ft cork tiles for a 2x4 ft ceiling tile. This is straighter and allows me to pin the parts down better.

The first step on building the wing is to label the laser cut ribs.... Done with a red thin tip sharpie.

Now, a question for all who have built a Chryslais....

The 1/16 x 3 in sheeting that is for the wings is short for the middle piece if I make sure the grain is the direction shown. So I assume that I'm supposed to splice two pieces together. There is no mention of this, so I thought I should ask... See picture number 2.

Steve
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Old 11-03-2012, 11:29 PM
  #111  
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Yes, just cut two piece's and glue together. You will find this typical on most kits. I did the smaller areas first and used the extra that was trimmed away to make the middle areas longer.
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Old 11-03-2012, 11:34 PM
  #112  
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Steve there should be a joint at the polyhedral break.
One sheet from the root to the break line and another sheet from the break line to the tip.

Are the supplied sheets too short to do it that way?

Paul
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Old 11-04-2012, 02:58 AM
  #113  
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The Chrysalis is intended to be a building trainer, as well as a sport flyer+flying trainer. There are a number of construction features that are fairly standard details in wooden airplane kits. Sheeting center sections and poly breaks is one of those items.

I like to make up a long strip (15" long or so, any longer than that gets a little awkward to handle) of cross-grain wood. Measure the width of the area to be covered, then cut a bunch of pieces just a little (about 1/8") longer than that. Splice all of those together into a long strip, and sand the glue seams so the strip is all smooth and uniform, ready to go. It's a lot easer to do that now than when the planking is already on the wing.

Start fitting at the trailing edge and work forward. Fit the aft end of the strip in position, then mark the forward edge and cut it just a hair oversize, then adjust the forward edge for a perfect fit, before applying the glue and sticking it permanently in place. When you get to a spar, the cut for the forward edge of the balsa will be at the correct angle for the trailing edge of the piece that goes on the other side of that spar. o as much as you can in a continuous process like that, so you minimize waste. When the sheet gets too short, cut some more pieces and splice those on, so you don't waste anything.

You will find that making a long strip like that really speeds up the process.

Note also that the balsa sheeting on the bottom goes underneath the edge of the ribs, and across the top edges of them on top. Some folks tried to butt the sheeting up against the side of the rib, which is incorrect. It's also a lot more difficult to fit that way.

Leave out the last piece of sheeting for now, between the main spar and leading edge. That gets added later, when the leading edge dowel is in place, and when the wing is off the board so you can see what you're doing. The key there is to trim the forward edge of the sheet to lap over about half the width of the leading edge dowel, then bevel the underside of the sheet for about 1/2-2/3 the thickness of the sheet, to get a lap joint at the leading edge. Once glued in place, you can sand the outside surface of the sheet to get a smooth blend from the sheeting to the dowel.

Last edited by Don Stackhouse; 11-04-2012 at 03:18 AM.
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Old 11-04-2012, 03:09 AM
  #114  
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Paul, not sure what you are referring to. Are you thinking the wing is supposed to be fully sheeted, or have "D-tube" sheeting between the main sar and the leading edge? That's something a lot of beginners have trouble with, so we designed the Chrysalis to not need it. The only sheeting is for one rib bay on both sides of the root, and on both sides of each poly break.

D-tube sheeting does two things: it adds torsional stiffness, and it eliminates the covering sag on that critical forward portion of the airfoil, between the spar and the leading edge.

The diagonal bracing provides enough torsional stiffness to eliminate the structural need for D-tube sheeting.

To eliminate the aerodynamic need for leading edge sheeting, we realized that roughly 80-85% of the surface in between the ribs is at a nearly constant shape, it just isn't the same shape as at the ribs. I built some test sections, measured the covering sag in each section of the structure, and developed correction factors for each of the different sections of each rib. I then bulged out the individual sections of each individual rib, to lift the covering in between the ribs up to the desired nominal airfoil shape. It was a HUGE amount of work (and I have not heard of anyone else going to this much trouble), but it paid off in the end results.

I have heard of one or two folks trying to "improve" the plane by adding D-tube sheeting. Their planes still flew well, but not as well, and with some interesting new handling quirks. Do NOT try to D-tube sheet a Chrysalis!
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Old 11-04-2012, 03:21 AM
  #115  
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Thanks all, That's what I thought but I was not sure. And Don, I do like your idea of cutting and glueing a long piece, then using that. It would seem that you would waste less wood that way, but would have more seams to deal with.

Tomorrow I get to rake/mow up more leaves and there's a few other things around the house to do. (According to the boss) But.. I plan on making time for some building as well. I also have next week off from work. That means building and flying!

Also, Paul, the other spar on the plans is only on the top. Maybe that's what you were talking about?

Steve
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Old 11-04-2012, 03:31 AM
  #116  
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Originally Posted by Don Stackhouse View Post
....Note also that the balsa sheeting on the bottom goes underneath the edge of the ribs, and across the top edges of them on top. Some folks tried to butt the sheeting up against the side of the rib, which is incorrect. It's also a lot more difficult to fit that way.

...

I did notice that. The thickness of the spars that are over the sheeting are a little narrower. And on the plans it looks like the sheeting is over the ribs. That much I could tell as well. Hoping to make more progress soon!

Steve
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Old 11-04-2012, 12:59 PM
  #117  
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I looked at the first picture in the first post of this thread. From looking at that picture alone, I thought the wing structure was a standard D Tube.

If I looked ahead at the second picture I would have realized I had mis-interpreted the wing construction.
That's why I had the confusion in my post. Sorry about that.

Paul
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Old 11-04-2012, 01:30 PM
  #118  
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Nope, no D-tube, for a number of reasons in addition to the ones I mentioned. Besides being a problem area for beginners during construction, a D-tube also locks in whatever warps you happen to build in. With no D-tube, it's easy to reset the washout to whatever you want or need, just by re-shrinking the covering. More washout tends to make the plane easier to fly, but at the expense of performance. The settings shown in the instructions (1/8" on the inboard panels, none on the outboard panels) are just about ideal for both beginners and sport fliers, but you can experiment with a little less if you want after you get used to the plane.

There are two things this feature does require. Since the washout can change, it can also shift on its own due to weather changes, storage (make sure you don't store it in a way that tries to twist the wing), etc. Get in the habit of checking the washout periodically, and resetting if necessary. After a while it will tend to settle at the setting you keep it at, just like the way a new set of guitar strings tend to stay in tune after they have settled in. However, checking things like washout periodically is a good habit to have with ANY airplane, and part of what the Chrysalis is about is to teach good habits.

The other factor is that the wing relies on the covering for some of its torsional stiffness. For this reason, do not use ultra-lightweight coverings on the wing, use regular weight coverings, such as Monokote (including transparent), or regular weight Ultracoat or Oracover (same thing, just different labels, and my personal favorite). Monokote is slightly stiffer for its weight, while Ultracoat/Oracover is tougher and more dimensionally stable, and with less tendency to get gas bubbles under it over time. It's also easier to work around complex shapes (such as wing tips and noses) without wrinkling.

If you want to save a little weight, you can get away with lightweight coverings on the fuselage and tail, although if you added the lightening holes in the tail, I would use regular-weight coverings there.
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Old 11-07-2012, 02:51 AM
  #119  
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ve made some good progress on the wing today. Pages 3-6 of the wing instructions are now complete (for the right wing.)

I laid out everything on the plans and did discover like vicrider that the plans donít quite match the laser cut parts. The plans are about 1/16 too short for each wing section. Like Don mentioned earlier, use the parts as the guide.

The first picture covers Page 3 of the instructions. Some 1/16 sheeting, the lower spars, training edge (already notched) and two ribs per wing section. You use the shear web laser cut parts and the notches in the trailing edge as guides for the ribs.

Picture 2 is the additional pieces for the 3 piece wing. Before moving on to the next set of instructions you need to laminate the additional ply rib doublers to the needed balsa ribs. Play close attention to the sides that they get glued to!

Picture 3 and 4 show the ribs getting glued in and the shear web being used as a guide.

Picture 5 shows the hardwood ends to the spar that are laser cut with the correct angles. The 3 piece wing kit has special pieces because the ribs are thicker with the additional ply doublers added earlier.

Picture 6 shows the rear ply web pieces glued in with the front piece just sitting on top getting ready to be installed.

Picture 7 - the main spar is a square tube. Seems strong already!

Steve
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Old 11-08-2012, 04:16 AM
  #120  
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More progress...

I glued the leading edge dowel to the wing. This takes a while because it needs to bend quite a bit. You start at the wing tip and glue that down first. After that dries, you bend it the rest of the way and glue and pin to hold. See the first picture. After this has dried, you move to the diagonal braces. You first add some washout to the center wing section. (A total of 1/8 in at the end) then glue in the diagonal braces. The outer wing is supposed to be completely flat. All washout is in the center.

Slow but sure, it's begining to look like a wing.

Steve
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Old 11-08-2012, 06:15 PM
  #121  
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Don and vicrider,

I just made a trial fit of the wing halves and the carbon tubes seem too short. Is there something I'm missing? Mine are 4 in long which seems a little short.

Steve
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Old 11-08-2012, 07:29 PM
  #122  
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Good question. I'm checking with Joe on this. To the best of my knowledge we haven't been having problems with this.

The key criterion is that both ends of the joiner must stay engaged with the ply doublers on the ribs at all times.

Worst case would be to make some oversize joiners, but I would like to verify how the problem occurred to begin with.
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Old 11-08-2012, 09:20 PM
  #123  
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Steve, Sorry I dont know what to tell ya cause I made my wing 1 piece.
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Old 11-10-2012, 12:33 AM
  #124  
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I finished mine.
Came out at 35oz with a 1800 3 cell battery. I used a eflite 480 motor with a cam 12x5 prop and a 40 amp esc, futaba 3114 servos on th R/E and 2 cheap 5gr servos for the spoilers. Im using a futaba 6J radio with the spoilers on channels 5 and 6, 6 being slaved to 5.


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Old 11-10-2012, 12:48 AM
  #125  
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Here is another. Will have to wait to fly it, winds are up, weather is going to be crappy for a few days.

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