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Old Dec 06, 2004, 07:10 PM
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Joined Mar 2004
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I picked up a can yesterday. Tried it on some Arcel and EPS and neither was affected. So WTF knows what formulas are where?? MM also suggests in the build guide that the solvent melting the surface a BIT actually helps the bonding. Anyway, the scraps in the box make good R&D.
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Old Dec 06, 2004, 07:58 PM
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SF Bay Area, California
Joined Sep 2004
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When in doubt, always test. The 3M77 will melt some types of foams but not others. Just because it does not melt one foam does not mean it's going to work on all other types of foams. Good idea on testing it on the packaging scraps.
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Old Dec 06, 2004, 09:08 PM
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Portland, OR
Joined Nov 2004
414 Posts
The Build Begins...

Preparing to assemble the wing

The first step of the build as per the builder's manual is to assemble the wing by gluing the two halves together. The wings have been cut with the angle necessary to create the right amount of dihedral, so you don't need to worry about any cutting.

The first thing I did was prepared a place for the wing to rest while the glue sets. One wing needs to be supported while the other can lie flat. I used stack of books, staggered to produce an angled support.
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Old Dec 06, 2004, 09:11 PM
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Portland, OR
Joined Nov 2004
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Aligning the wing halves and gluing

Having decided how I was going to support the wing while the glue sets, I was ready to get my fingers sticky. I frst applied some strips of masking tape to the underside of one wing half, leaving extra tape hanging off the end. I then pressed the other wing half down onto the tape while aligning the wing as it will be joined. Having done this I now didn't need to worry about getting the wings lined up at the same time as gluing them together.

I used masking tape because it doesn't stick too much, but that was a double-edged sword, as I found that when I positioned the wing on the edge of the table with one half hanging (see pic 2), the tape began to come away. Next time I'll use regular Scotch tape instead - it's stronger but will still peel off easily when I'm done with it.

The second pic speaks for itself - you can see how I applied the epoxy.

Pic 3 shows the wing being supported while the glue dries. I placed a weight on the flat half to apply some pressure to the join.
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Old Dec 06, 2004, 09:26 PM
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Portland, OR
Joined Nov 2004
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What, not perfect??

Having used 5 minute epoxy for the join, I was able to handle the wing after 15 minutes. With a critical eye I began scrutinizing my work.

There were gaps!

And the wing halves weren't perfectly aligned!

OH NO! I thought this was going to go so smoothly! Mountain Models kits are meant to be top notch! How could there be gaps? I must have done something wrong!
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Old Dec 06, 2004, 09:35 PM
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Portland, OR
Joined Nov 2004
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Calm down. Breathe. It's not that bad.

Okay, so maybe I was being overly critical. The alignment is fine - I can fix the slight difference at the front of the join with two strokes of the sanding block. And the gaps at the front and back? Probably not a big deal, but I decided to wick some foam-safe CA into them anyway. It put my mind at ease.

Turning the wing over, you can see (last two pics above) that the whole joint is open slightly. I was a bit miffed about this. My fault, no doubt - I must have made that stack of books just a tiny bit too high. Is it going to be a problem? Hopefully not, because I decided not to do anything about it. That epoxy is strong stuff, and there's plenty of it in there.

So let's move on to the strapping tape!
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Old Dec 06, 2004, 09:52 PM
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Flemington, NJ
Joined Oct 2004
56 Posts
Quote:
Originally Posted by PilotOne
Very good build thread so far!

I would just like to caution everyone that 3M changed the formula of Super 77 over a year ago. The new 3M77 will melt styrofoam if you are not careful. Please read this thread in the foamies section for more details:

http://www.rcgroups.com/forums/showt...highlight=3M77
If you are worried about the different 3M formulas, someone in another thread mentioned that Michael's sells a special spray adhesive just for foam. Look for it in the foam section (not the glue section). I picked up a can for my build - which must wait until Christmas.
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Old Dec 06, 2004, 10:36 PM
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Portland, OR
Joined Nov 2004
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Applying the strapping tape

The next step is to glue a strip of plastic strapping tape to both the top and bottom of the wing to provide strengthening. There are grooves in the wing for the tape to lie in, so you don't need to worry about getting it straight. The tape is first sanded to help the glue to stick to it. I used a 150 grade sandpaper for this, and went over the whole strip about 8 to 10 times - enough to make a noticable difference but not enough to remove the crosshatch pattern on the plastic.

To make sanding and applying glue to the tape easy, I affixed the strip to my workbench (over a piece of wax paper) with scotch tape. I cut each strip an extra couple of inches longer than the wing, so that when I taped the ends down to the bench, the scotch tape didn't get in the way of where I need to apply glue. This also leaves the ends dry so you don't get such sticky fingers when handling the glued tape. (I still got plenty of glue on my fingers, hands and forearms though!)

For this I decided to use 30 minute epoxy, since I was in no hurry.

Applying the strapping tape to the wing is a bit of a messy job, since the tape wants to curl up on you while you're trying to line it up and press it down. But a bit of juggling and some packaging tape to hold it down, and it's done. I held the strapping tape down by applying packaging tape over the whole length of each strip. After the glue had cured I guess I could have removed the packaging tape, but I decided to just leave it there. I'm not going for any light-weight record with this plane.

I waited the recommended two hours for the glue to cure on the first side before doing the tape on the other side of the wing. In hindsight, I don't think this was necessary because I could have done both sides inside the half hour it takes for the epoxy to set. However, if you use 5 minute epoxy for this, I would definitely do one side at a time.

The first pic shows the strapping tape ready to be sanded and glued. The manual is underneath the wax paper. The second pic shows that extra inch of tape waiting to be trimmed after applying it to the wing.
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Old Dec 11, 2004, 01:33 AM
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Portland, OR
Joined Nov 2004
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Okay, if anyone has been waiting on the next chapter, sorry about the wait. I was too busy building the plane (and occasionally working) to write. The plane is all but finished now, so I can write some more.

Designing the color/pattern scheme

I ordered three rolls of wing tape from MM: white, dark purple, and orange. I wasn't sure which colors I would ultimately use.

As fate would have it, my decision was easy: MM was out of orange, so I ended up with purple and white.

I settled on making the fuselage purple and the wing white underneath and white & purple on top. But it was difficult to visualize a wing design in my head. So before I began, I came up with a quick & dirty method of previewing basic designs. I drew the outline of the wing on a sheet of white paper and covered it with packaging tape so I could stick more tape on it and pull it off again without tearing the paper. I then put some of my purple wing tape on some more paper and cut out the outline of the wing (actually just half of it; I was lazy). I decided to keep my design simple: I would just have a series of lines running fore-aft across the wing. So I cut my purple wing-half into strips which were the equivalent width of a piece of wing tape proportional to my wing drawing. I then shifted these strips around on the wing drawing until I found something I liked. When I was happy with a design, I put a strip of scotch tape over it to hold it in place.
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Old Dec 11, 2004, 01:50 AM
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Portland, OR
Joined Nov 2004
414 Posts
Before covering the wing, the manual suggests reinforcing the area where the rubber bands will press on the wing edges, by applying four short strips of wing tape to each edge. Instead wing tape, I decided to use 3M Extreme Applcation tape. This stuff is pretty heavy duty (whereas wing tape is extremely thin), so I went for 3 pieces on each edge. Heavier than wing tape, no doubt, but it should be very strong.

Covering the wing

I'd have to say this was my least favorite part of the build. It isn't too hard to apply wing tape, but it's very hard to apply it perfectly. This took me something like 3 - 4 hours. But I certainly learned a lot in the process and developed some methods. Next time I'll be a lot quicker, and hopefully do a better job.

I decided on a white and dark-purple color scheme for my Maggie. I could have just usd clear packaging tape for the white, but I wanted to have a smooth look rather than be able to see the texture of the EPS. So I used white wing tape.

The first thing I learned was that my white wing tape wasn't completely opaque, and every speck of dust and dirt that got stuck underneath it could be seen. If I were building a model with immaculate presentation in mind, I wouldn't use this white wing tape again.

The 3M77 spray adhesive has a 'tack range' of 15 minutes. I assume that means that you're supposed to join the parts you're gluing within that time frame. I doubted my ability to cover the whole wing in 15 minutes, so I decided to spray only the top to start with. Well, I think I got about two strips of tape down in that time. However the wing still felt pretty sicky (it's impossible to avoid touching it), so I forged ahead and got one half of the top of the wing done.

At this stage I realized that not having sprayed the whole wing was a disadvantage. It meant that the tape I was applying to the edges, which wrapped around to the underside, was required to stick on the bottom of the wing without the added help of the spray adhesive. As it turns out, without the 3M77, the tape doesn't stick to the EPS very well. So after my first quarter of the wing was done, I decided to spray the rest of the wing. Another disadvantage to not having sprayed the whole wing was that I now had to try to spray the rest of it without getting the adhesive on the wing tape I'd already applied.

Finishing the wing of course took a lot longer than 15 minutes, but the glue still seemed to have a reasonable mount of grab even as I was finishing. Having said that, there are parts of the wing where the tape isn't sticking well, but it's not enough to be a problem.

Other things I learned:
  • A very clean work surface will be an advantage. The sticky wing will pick up bits of grime and you'll end up having to get them off, or you won't notice them until they're a lump under the wing tape.
  • When you touch the sticky EPS, sometimes some white foam dust will get stuck to your fingers. Then when you touch your wing tape, the white dust will sometimes transfer to it. On anything but white tape, this looks bad. Fortunately it's easy to get off. I used the sticky side of a piece of scotch tape to 'dab' it off.
  • If you mess up a piece of tape and decide to pull it off, it will take some of the 3M77 with it, leaving you with a worse chance of the tape sticking well. So there's extra incentive to get it right first time.
  • If you need to peel a piece of tape off, it will come off the foam easily, but it sticks really well to itself, so it will try to pull any tape under it off too.
  • There is an excellent tip in the manual: keep your scissors and knife clean by wiping off the adhesive that builds up on them from cutting the tape. This is essential. I had to stop and clean my scissors every 10 cuts or so.
  • Compund curves are a bitch to tape. Don't be afraid to make several strategic slits in the tape for each piece. Without slits, you will have big ugly creases. You will become a master are wielding your hobby knife like a brain surgeon.
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Old Dec 11, 2004, 02:04 AM
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Portland, OR
Joined Nov 2004
414 Posts
Wing covering part II - the decorative taping

As you can see from the images above, I decided to cover the whole wing with white, then apply the purple stripes on top. This, I supposed, would be much easier than trying to do the whole thing in one pass.

The challenge now was to neatly apply the tape to only the top of the wing, with nice neat edges. Thankfully I did find an easy way to do this. With the wing flat on the table, I would apply a piece of tape with a couple of inches of excess on the both ends. The excess I would stick down to the table itself, while keeping the tape taut. I could then place a steel ruler along the wing edge and, while applying downward pressure on the ruler to keep the tape taut, make a quick cut along the ruler edge with a sharp blade. As long as I carefully positioned the ruler so that the cut was where I wanted the tape to end, I would get a nice straight line.
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Old Dec 11, 2004, 06:57 AM
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Alpharetta, GA
Joined Sep 2004
460 Posts
Lookin Great! I am a little bit farther along than you on my Magpie. This is my first real plane build.
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Old Dec 11, 2004, 02:58 PM
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Joined Jul 2004
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I know this is a little late in the game to be bringing this up, but do you have a scale that you could measure the weight as you're building ?. I always weigh my parts before and after the build to see how much weight I'm adding. Would be good info for people interested in buying the kit or experimenting with finishing options.
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Old Dec 11, 2004, 04:03 PM
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ToyBoy's Avatar
Portland, OR
Joined Nov 2004
414 Posts
Usta, that's a great idea and I would love to do it, but no I don't own a scale yet. And I'm not allowed to buy one because it's on my Christmas wishlist.
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Old Dec 11, 2004, 06:33 PM
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Portland, OR
Joined Nov 2004
414 Posts
Assembling the fuselage

Assembling the fuse is fairly simple matter of gluing the two halves together, and gluing a piece of strapping tape to each side for strength. I did have some trouble though. When I first placed the two halves together, I noticed that the fuse wasn't straight. I was a bit worried about this, but made the dubious decision to forge ahead anyway. Not sure what I was thinking. So I glued the two pieces together, and then had second thoughts. I found that the tail was significantly off center. It ocurred to me only then that I could have avoided this by sanding the join surface to a slightly different angle. Too late now.

There is a thread about this here.

The good news is that you can straighten a crooken fuse by pulling it into shape when you glue on the strapping tape. The important thing to remember is that you want to pull the fuse into shape, and you don't want to be pulling an already-reinforced fuse, so make sure you straighten the fuse with the first piece of strapping tape you apply, not the second. The manual actually suggests the opposite to this, saying you only need to worry about straightening when you apply the second piece of tape. Obviously I disagree.

See the photos in the thread mentioned above for how I set up the fuse to straighten it. Basically, I just used a combination of props and weights. After applying my first piece of tape, I was pretty happy with the result. I'd gotten the tail to within 1/16" of being centered. Unfortunately, being a perfectionist, I tried to improve on this while applying the second piece of tape -- only to end up with the tail off by 1/4 inch! I was reassured, however, that this would not be a problem.

The strapped fuse is remarkably strong. I feel like I could wack a burglar in the head with it and it wouldn't break. (Of course, it wouldn't hurt the burglar either)

To hold the fuse on the table while I was gluing on the strapping tape, I taped some folded paper to the table with a loop big enough for the nose to squeeze into. I also cut and placed a piece of scrap balsa into the motor housing hole so that I wouldn't risk bending the nose inward and breaking it. See the first picture.

I used 30 minute epoxy to attach the tape. Once the strapping tape was glued on, I covered the whole strip with packaging tape to hold it down, just as I had done with the wing. When the glue was cured, I removed the packaging tape.

The second picture shows the arrangement for holding the fuse straight while the glue was setting. The third shows the end result. You can see that it isn't quite straight.
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Last edited by ToyBoy; Dec 11, 2004 at 06:40 PM.
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