Magpie Build Thread and Review from a Beginner's Angle - Page 3 - RC Groups
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Dec 11, 2004, 08:34 PM
2 Mistakes Downwind
ToyBoy's Avatar
Rounding the fuse and mounting the wing supports

The next task is to round the edges of the fuselage by sanding. As recommended by the manual I started off with a 220 grit paper. I found even this grade of paper had a tendency to grab at the foam beads and rip them out, leaving some small holes. I went to a 320 grit which was better, although there was still some catching.

One thing I did wrong was to round the top of the tail where the fin is to be attached. You need that area to remain flat in order to glue the fin on straight. The worst part is that I had already been warned about this by pinecone in this post, but completely forgot about it. Not a big problem though; I just carefully sanded the tail section flat again and hopefully didn't put an angle on it.

Next I wanted to attach the wing supports, which are thin strips of ply. Unfortunately mine were warped and I wasn't completely confident that it would be wise to glue them with the warp. I didn't know if they would pull away or at least weaken the glue with potentially bad results. So I put this task off for a couple of days while I straighted the wing supports. I did this simply by wetting them and placing them on the flat table with a heavy weight on top and leaving them there for a couple of days. There's a "before" picture below; I thought a took an "after" pic too, but I can't seem to find it. Anyway, I didn't get the warp out completely, but enough to assuage my concern.

I chose to use 30 minute epoxy for this. Lining up the supports correctly was a bit fiddly, but not overy difficult. I attached both sides at the same time and used some clamps to hold them in place. Doing one at a time would certainly have been easier. I used my metal ruler to line them up evenly with the forward edge of the wing saddle on the fuse. (see pic 2)

If you use clamps as I did, be careful not to clamp too tight, as EPS foam, if crushed, does not bounce back.
Last edited by ToyBoy; Dec 11, 2004 at 08:37 PM.
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Dec 14, 2004, 03:22 AM
2 Mistakes Downwind
ToyBoy's Avatar
Covering the fuselage

After gluing the wing supports and servo mounts to the fuse, it's time to cover it with wing tape. This was fiddly but not too difficult. Again, the compound curves are nearly impossible to do smoothly. My worst part was the nose. The rest I was pretty happy with.

The right side of the hole for the receiver will be permanently covered with wing tape. Since wing tape is very thin and thus could puncture easily, I decided to cover this hole with a piece of clear packaging tape before starting with the wing taping. Packaging tape is probably twice as thick as wing tape, so you end up with with 3 times the strength of covering over that hole than just 1 layer of wing tape would give.

A picture is supposed to be worth a thousand words, so I've tried to use pictures to give some hints as to how to neatly tape the trickier areas. Basically, as I mentioned when taping the wings, you just need to put strategic cuts in the tape as you apply it. Generally a cut goes on the apex of every curve that would cause a crease in the tape. Sometimes it works best to cut along the curve (see first pic), other times (usually) perpendicular to the curve.

As one of the pictures shows, I sometimes use a sock worn over one a to smooth down the tape as I apply it. The other hand holds the tape away from the fuse, controlling the application so no creases/bubbles get in.

Please keep in mind that this is my first build. Anything I recommend or suggest is subject to being later shown to be completely idiotic. It's just what has worked for me as I've muddled along.
Dec 14, 2004, 03:24 AM
2 Mistakes Downwind
ToyBoy's Avatar
A couple more shots of the fuse covering progress...
Dec 14, 2004, 03:31 AM
2 Mistakes Downwind
ToyBoy's Avatar
When cutting out the covering over the receiver hole, I cut a hole in the covering smaller than the hole itself so that I could fold the covering into the hole. Unfortunately, tape doesn't stick at all well to EPS without the help of some adhesive, and I didn't spray any 3M77 into the hole, so my tape keeps coming unstuck from the inside of the hole. I put some packaging tape over it to hold it down and even that comes unstuck. I'm going to have to glue it with something.

Pics of the process...
Dec 14, 2004, 03:38 AM
2 Mistakes Downwind
ToyBoy's Avatar
Similar story when cutting the servo holes. I cut the hole in the tape smaller than the actual servo hole would be. This allows a little tape to fold into the hole, which looks good and also aids a snug fit for the servo.

In the second shot the bottom hole cut been cut/dug out but the top one hasn't.
Dec 14, 2004, 03:42 AM
2 Mistakes Downwind
ToyBoy's Avatar
The motor mount

Not much to say about this. It was a cinch to put together. At first I was doubtful about the use of CA as mentioned in the manual. I don't like using CA much because it sets so fast that it can be hard to get your joins straight. Also I thought it seemed wiser to use epoxy on the motor mount for strength. But when I put the motor mount together without glue, I realized why CA would be fine. It fits together like a jigsaw puzzle. Those pieces aren't going to come apart due to stresses. The wood will break first. Also, the pieces fit so tightly together that you can build the mount and then wick the CA into the joins. I didn't do it like this, but I think it would be fine to. (I did use this technique to glue the MM camera mount for the Magpie -- more on that later)

I did need to sand a few of the interlocking tabs a tiny bit to get them to fit together. I also needed to sand the stick a little in order for the motor to slide over it, as suggested by the manual. After that it was a perfect fit.

In the second picture below the motor mount is put together without any glue. It takes about 30 seconds to build.
Dec 14, 2004, 10:18 AM
Registered User
Did you spray the sides of the fuse one at a time? Also, if you would have done the rx side first, you could have wrapped inside the rx hole all the way through to the other side and then sealed it.

I intend to test some water contact cement on EPS for covering soo - will post when done. That may work for the little tape tags that don't stick.
Dec 14, 2004, 12:36 PM
2 Mistakes Downwind
ToyBoy's Avatar
Yes, I sprayed the whole fuse in one go. Good point about taping right through to the other side - that'd work nicely.

Look forward to hearing about the cement.
Dec 15, 2004, 10:15 AM
2 Mistakes Downwind
ToyBoy's Avatar
The vertical stabilizer

The first thing I noticed about the fin was that the bottom edge, where it would connect to the fuse, was not cut perfectly square. I tried to stand it up on the table and it leaned over at a considerable angle (and of couse fell over if I didn't hold it). If I didn't fix this it was going to be a challenge to glue it on to the fuse straight. It was easy to fix though -- I just sanded the bottom until it could stand up on the table without any support.

I couldn't think of any practical way to support the fin and keep it straight while the glue set, so I just tried to get it as straight as possible by sight, and hoped for the best. The now-flat bottom edge obviously helped a lot in this repect. I think I did pretty well -- if there is any angle on the fin, it should be no problem to counteract with a bit of trim in flight. I used 5 minute epoxy.

While cutting the covering tape away from the top of the fuse where the fin will go, and while attaching the fin, I put a piece of balsa into the slot in the fuse for the horizontal stablizer. This prevents the top part of the fuse at this slot from flexing while pressing down onto it.
Dec 15, 2004, 10:17 AM
2 Mistakes Downwind
ToyBoy's Avatar
The horizontal stabilizer - uh oh!

This is where I hit my next stumbling block.

When I slid the horizontal stabilizer into the slot in the tail, which is pre-cut at the factory, I discovered that the slot was too short. The stab should have been flush with the end of the fuselage, but insead it stuck out 30mm. This was a manufacturing error. I cursed myself for not having noticed this sooner. If I had discovered it earlier on, I could simply have cut the slot to the correct length myself, and gone ahead with the build unperturbed. However, by now I had glued on the servo mounts, covered the fuselage and cut the servo holes. The servo mounts/holes are positioned about a quarter inch from the end of the slot for the horizontal stab! So I had put them 30mm too far back on the fuse.

So, after cursing for a while, I regained my calm, sat back and considered my options. I could peel back the covering, remove the servo mounts, fill in the holes with something and then make the new holes in the correct place and cut the slot to the right length. I really didn't like this idea as it would be very messy and I might even ruin the fragile fuse trying to get the servo mounts off. Plus I'd probably have a weakened tail area. Second option: cut the stab to be 30mm shorter. I guess the plane would still fly okay, but I have no real idea how much this would affect it. Third option: cut a slot in the front of the stab so I can slide it all the way forward. The top servo was going to be in the way a bit but I could cut around it. I liked this idea best.

I emailed Doug and asked for his advice. He agreed that the third option sounded best. Naturally he also offered to replace the whole thing if I wished, or if my work-around didn't work, but I had done a lot of work on this fuselage so I really didn't want to start again. So option 3 it was.

I made the necessary measurements and cut away just the right amount of the stab to allow it to slide into its rightful place.

Lesson learned: CHECK THAT EVERYTHING FITS TOGETHER PROPERLY BEFORE STARTING THE BUILD! Even a quality company such as Mountain Models can have manufacturing glitches.

Almost everything is done now. I'm still waiting on my radio to arrive, but I have tested the control surface action by hooking the servos up to the receiver from my T-Hawk, and everything seems okay. The incorrectly positioned servos lead to shorted push rods, but to no detriment that I can see.

I'm also still waiting on the battery, so I still have one final task, which to mount the battery and ESC and set the center of gravity and the lateral balance. (Okay, so it's more than one task...)
Last edited by ToyBoy; Dec 15, 2004 at 07:05 PM. Reason: Typos galore
Dec 15, 2004, 10:19 AM
2 Mistakes Downwind
ToyBoy's Avatar
The elevators and rudder

There were a couple of sections in the build where the wording in the manual wasn't entirely clear, at least to me. Generally I was able to figure out what was meant by looking at the pictures. With the elevators, it took me some trouble to figure out which side I was supposed to cut the bevel into. But eventually my brain cleared and I understood. I then cut the bevel into the wrong side. I'm still not sure how I managed that. Anyway, no great problem. I probably could have left it like that and it would have worked, but I decided to try to stick to the plan, so, after gluing the elevators together with the dowel, I flipped them over, cut a hole for the control horn in the new left (formerly right) elevator, and put some white wing tape over the hole in the new right elevator. As far as I know that was my only real blunder in the build.

When it came to mounting the elevators to the horizontal stabilizer, the manual says that they should just "kiss" the stab. I found that I actually had to put about a 1/16" gap between the stab and edge of the elevators. Without this, the tape hinge was preventing smooth deflection of the elevator. I did the same with the rudder.

I found that the dowel which joins the two elevators interfered with the rudder. My dowel is slightly warped and so it sticks out a little further than it should, so this accentuates the problem. To overcome this, I cut a notch in the rudder where it crosses the dowel. Picture below.
Dec 15, 2004, 10:30 AM
2 Mistakes Downwind
ToyBoy's Avatar
The push rods

I happened to have some green heat-shrink tube of the right size, so I swapped it for the white stuff that came with the Magpie, just for fun.

When shrinking the heat-shrink tube, I put some aluminum foil behind it to deflect the heat and help prevent the wing tape from shrinking. Even with this there was still some slight-but-noticable shrinking of the tape behind the rod. I used a mini blowtorch to shrink the tube. A heat gun would work too.
Dec 15, 2004, 10:30 AM
Registered User
Great info. BTW, isn't that motor pointing down quite a bit?
Dec 15, 2004, 10:36 AM
2 Mistakes Downwind
ToyBoy's Avatar
Originally Posted by rutat
Great info. BTW, isn't that motor pointing down quite a bit?
It does seem like quite a lot, now that you mention it. But the angle is controlled by the slot in the fuse that the motor mount slides into, and it's a very snug fit, so there shouldn't be any variance -- I assume that's the correct angle...
Dec 15, 2004, 11:54 AM
Pro Bro #1442
W'rkncacnter's Avatar
Very Nice so far. Will have to look out for the Tail thing. BTW, a cigarete Lighter also works fine for shrinking the Heat shrink, but you'd have to turn the plane upside down for the Bottom servo linkage, wouldn't want to melt the Depron would we?

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