|Mar 03, 2013, 11:51 AM|
I have been working on Pat Tritle's C140, which is a close replica of a Cessna 140 without actually being called a Cessna. This is for legal reasons I suppose. Cessna didn't want to allow the rights to their name to be used on models. So it's not officially a Cessna.
The initial superstructure built up quickly. I got the barebones photo done in a week. It's a little hard to see it in the hotel room, with similar colors to balsa wood surrounding it. I took it with me to work on it during a recent business trip.
I tried to keep it as light as possible, although I did have to reinforce two things. The wing tips and the tail circumference are laminated balsa strips, a method that works well and usually is pretty strong while still being light. However, my choice of wood was pretty poor and it turned out to be punky balsa, so mine was too fragile. More on that in a minute. I also needed to thicken the wing root on both sides where it meets the fuselage because frankly, 1/16" sheet balsa was just a little too weak. I don't think that would have even held up in flight. So I laminated a second 1/16" sheet piece in a few spots where I thought it needed strategic strengthening. Finally, the fuselage was supposed to use 1/8" square balsa strips, but the notches laser cut into the fuselage formers were actually exactly 3/32" square. All I had available at the time was 3/32" basswood and I hated to use it, but I was too impatient to wait for my shipment of balsa to arrive. (Local selection of balsa is almost non-existent, living in small town-America. Everything has to be shipped in, which can get a little ridiculous sometimes). So the fuselage is actually pretty strong. Here's a barebones pic...
I covered the airplane in white Microlite film and then painted it. I first cleaned the surface of the Microlite film with rubbing alcohol to remove any possible mold release or any other surface contamination that could compromise paint adhesion. Then I bought Valspar silver metallic rattlecan paint (enamel) and started off with a light dusting, and then a second heavier coat. It really does look like an aluminum surface.
You'll notice the control surfaces are covered in a beautiful corregated metal. That is actually corregated aluminum foil, which cost $10 for 2 packages of the stuff at my local Hobby Lobby. It is much lighter than it looks, being foil. But boy is it fragile. You have to REALLY be careful handling the stuff so as not to crush it. I glued it right to the surface of the Microlite on the rudder and elevator to strengthen them because of the extremely fragile punky wood that I made my laminations out of. It looked so good that I couldn't resist, so I applied it to the ailerons and the faux landing flaps. Here are 3 pics from different angles...
(I like this one because the yellowish interior light really reflected well on the skin surface).
These are taken outside, and it was almost too bright for the camera.
I don't have the windscreen on yet because I am waiting for the decals before I glue that on. You see, I'm having a "dashboard" decal made for inside the cockpit, and I really need to be able to get my fingers in there to apply it. The windscreen and side windows are cut from 0.007" clear plastic and will be glued with canopy glue. (You don't want to use CYA glue on that!)
The wing struts are not on yet because I'm still working on those. The prop is a 10x6 and it's mounted on a Supertigre 370 brushless outrunner. It's painted silver in the front and black on the back, which I believe was what Cessna used. The prop tips should be white but are not yet painted.
This airplane weighed in at 13.28 ounces, with paint and corregated control surfaces, with receiver and servos and fully rigged, and with the motor and ESC. However, I am using a 1350 mah 11.1 V 3 cell Lipo, which just by itself weighs a whopping 3.5 ounces, tipping this airplane's weight at about 17 ounces.
The wing loading is 7.1 ounces per square foot, so the stall speed should be about 13.5 mph. So it'll do well.
I have heard of some of these C140s weighing 32 ounces, but at that point, it is no longer Pat's design. I tried to hit Pat's target weight of 12 ounces but I missed it by 5 ounces. Still not bad and it'll still fly well. I used the battery as ballast, and on this plane the way I built it, the battery tray ended up being underneath, in front of the main landing gear.
|Mar 04, 2013, 09:44 AM|
Wow. Not much interest here. I'm surprised. Maybe it's because there just aren't that many builders anymore. Maybe Pat's right, but I didn't want to believe it.
Well if I can get some flying pics, I'll post them.
I got my wing struts completed and placed yesterday. I also tried spraying some clear coat on some inconspicuous spot and that was a bad idea. It turned the silver into a dingy gray. So don't do that.
I was just looking for a way to prevent getting finger prints in the paint from handling the airplane. But there's another way I can maybe do that. I can apply clear packaging tape to any areas of the plane that I handle routinely to try to keep fingerprints down. I have to keep that to a minimum because that all adds weight.
|Mar 05, 2013, 01:55 PM|
The parkflyer forum has become more geared toward ARF and foam as of late. It seems a bit hidden but the new Balsa Builders forum is the place to hang out now for balsa specific builds. Because it is so new not everyone has found it yet but it already has a huge membership. You may want to post it over there as well. Looking great so far!
|Mar 05, 2013, 03:53 PM|
I dunno if I want to type all that again. I'll remember next time I'm building a balsa plane...which will be soon, considering I just got in Pat's latest plane kit, the AJ-404 Interceptor.
I'm on hold for a few days waiting for my decals to come in from Callie Graphics. I managed to scratch the top of the wing on something when I had the plane upside down working on the wing struts, so I'll have to do a little bit of spot painting there.
So except for the decals and then the window gluing, I'm pretty much done.
Nice job on this kit, Pat. I really do like it.
|Mar 08, 2013, 09:33 AM|
I've got a few problems. First of all, paint adhesion on even Microlite is inferior. I had better results getting the silver paint to stick on the doped silkspan skin of my XP-55 scratch-built plane. It's spooky how easily the paint peels off when I try to pull the backing off the decals. And of course, that ruins my beautiful paint job.
There are a couple of things that do seem to work, however. Absolutely clear packaging tape or celophane tape, for example. Or CYA glue. On the decal that covered the nose, it simply didn't stick. It stuck to the paint, but the paint did not stick to the Microlite film and it came off. However, with CYA glue, I got the nose to stick. Problem is, the CYA glue also melted the dried silver paint a little too. So I needed to do some touch up with some similar blue paint. So much for my perfect finish on this plane.
What I will have to do to keep the decals from coming off in flight is to cover it in tape. Hopefully that will work. Because if that fails too, then I will rip off most of the skin off of this airplane and start the darn thing all over again. I am not pleased with how this is turning out and I am just trying to salvage it.
Whoever said paint sticks to Microlite was wrong.
Now, I haven't even STARTED on the wing decals yet. I really don't know what to do. I can't use packaging tape first on the wing surface because it doesn't follow the curve of the airfoil. I can maybe use thinner strips of clear celophane tape to follow the airfoil and then stick the decals to the taped area. That might work.
Now I have another problem with the windows. Apparently, canopy glue will not dry if you seal it off from air. Now I've got some sections of the side windows that won't dry.
Can you say "ARGHH!"?
|Mar 08, 2013, 07:45 PM|
Okay I came home to assess the damage and decide how to salvage my project after my decal disaster. The nose, where I glued the anti-glare decal looked fine last night but looks as wrinkled as the surface of a walnut shell now. I cannot salvage that part of the skin, and it needs to be cut completely off and start over. Since paint will adhere to Microlite as long as you don't try to stick decals to it, I bought a very similar can of Valspar blue spray paint and will mask off the new nose skin and paint that.
I touched up the silver on the sides where the backing paper (slightly adhesive) pulled off that silver.
I have only one idea that might work on the wings without destroying the painted surface, and that's if I cut out the numbers perfectly, separate them from the backing paper beforehand, and then carefully apply it by hand and hope I get it straight.
The canopy glue behind the window plastic that won't cure, is very slowly curing, 24 hours later. But I might need to trim back the plastic where it's excessively wide.
I've learned a lot of lessons here.
The main lesson is, never attempt to apply decals to the painted surface of microlite. If you're gonna do that, you're better off sticking with silkspan tissue. Either that or don't paint the Microlite.
|Mar 09, 2013, 09:58 AM|
As far as the wing numbering goes, this is what I'm going to try to do. I'm going to get those vinyl self-adhesive numbers/letters kits from Hobby Lobby and then spray paint them blue. Once dry, I'll hand-align them the best I can and stick them. Maybe with no backing paper, they won't pull the paint up.
|Mar 10, 2013, 11:32 AM|
I decided against vinyl self-stick numbers or vinyl decals of any sort. It's already caused enough damage to the paint on the fuselage. I've discussed this with Pat and I think I've decided that if I'm going to paint the Microlite, the only decal that will really work well are water-slide decals. So I'm looking at seeing if Callie can remake my decals that way.
And as far as painting an airplane goes, if I ever have to paint an aircraft again, I think I am going to go back to old-school silkspan tissue and dope. Because I've NEVER had such issues with decals when I used tissue. Iron-on plastic and mylar films were supposed to make things easier, not harder. It's just paint that seems to be so incompatible with iron-on films. As long as you avoid using paint, decals do fine.
I've got a Spad XIII that I've been wanting to build for a long time. That almost has to be a painted surface. So after this experience, I have definitely decided to dust off my silkspan skills and go back to tissue and dope.
As far as this project, I'll replace the skin on the nose and salvage what I have. It won't be perfect like I wanted it to be, but will still be very pretty.
If I had it to do over again, I'd have used silver microlite and then Callie's vinyl decals and would have just gone with that. Or else I would have used tissue.
I have had much better luck using vinyl decals over silver paint on doped silkspan skin in the past. The paint adhesion was much better on silkspan.
Oh well, this is all a learning experience, right?
|Mar 13, 2013, 09:22 AM|
This photo is a little dark. But I was able to actually apply the numbering decals to the wing. I had to come up with a method that works. So what I did was to make tiny sharpie marks on the skin to align the numbers, then cut the numbers out exactly and VERY carefully hand-apply them. Only one shot at this is possible, because wherever it sticks, it will pull up paint if you try to lift it back up. Then using the exacto knife, I carefully pulled up a corner of backing paper enough to grab it, and then held the decal down with the knife blade and pulled back at almost a 180 degree angle with the backing paper while holding down the decal with my fingertip, at the same time being careful not to touch the skin with the backing paper, because that pulls up paint too.
And it was successful.
In this photo, you can see the nose skin that I replaced. I'm going to redo that.
So it looks like thinking it over to come up with a strategy was a good idea and this project is salvaged.
|Mar 26, 2013, 12:26 AM|
Just finished the battery hatch and it works great.
Nose area is repainted and looks good.
I still have troubles with the way the wing struts attach to the wing, but for now it'll be okay. I may have to readdress that one of these days.
The 140 is ready for test flying.
I plan to meet up with the airplane's designer, Pat Tritle, here in a couple of weeks and maiden it with his gang of flyers in Albuquerque. I just hope I don't embarrass myself.
It's night now, but during the day, I'll try to get a good final pic of this plane loaded up here.
|Mar 26, 2013, 08:13 PM|
This airplane is officially finished. I've taken 3 photos of it.
Of course, right after this, I had a minor incident trying to walk back inside the front door as one huge black labrador retriever and 3 cats rushed me trying to force their way outside. The dog and one cat made it out, I soccer blocked a second cat, and the third wisely changed her mind.
During all of this, naturally, the elevator sustained some damage as it bumped into the wall. I'm lucky it wasn't worse. But one thing about Pat's planes. They are light, but a little fragile. The elevator is glued and clamped back into place as we speak.
The real fault, however, lies with the punky wood that I made the elevator out of when I laminated it. Make it out of the right wood, and it would be a lot more durable.
Would it have survived the rush by 4 animals at the front door? I doubt it, but still would have been more durable with better balsa.
Still, I love how this plane turned out.
Do try the metallic silver Valspar spray paint to simulate an aluminum skin.
But DON'T try it on ANY kind of iron on plastic skin unless you don't plan on using decals.
If you're going to use decals, I'd recommend silkspan tissue. The adhesion still isn't excellent, but it's a lot better than it is on plastic skin. This won't always look this good either. As it gets bumps and bruises, the silver will simply flake off.
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