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Jack Stafford Cessna 120/140

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Old 03-01-2014, 12:17 PM
  #51  
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http://leisurercmodels.com/jack-staf...dels-kits.html
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Old 03-03-2014, 07:46 AM
  #52  
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Thanks Terry!
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Old 02-22-2015, 08:24 AM
  #53  
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I bought a short kit from the current supplier in 2009, and hope to begin my build sometime later this year. I have bought all the wood and created a "full kit" having fabricated all the parts. Power will likely be a VVRC 40 cc twin. May be a bit over powered, but that is what throttles are for!

I am doing a bit of re-engineering to the wing. The airplane as designed uses the Sig aluminum wing joiners. I am NOT a fan of these. They are heavy, fussy to install and align, and the bolts are easy to strip after attaching the wings multiple times. The ones in this plane are at an angle, losing some of their strength in effect. Wing load will make the wing want to angle forward a bit. Not good. Also, the load bearing spar and the Sig joiners are WAY forward on the wing, at about 15% of chord, or only 2 1/4" from the leading edge. When the wing loads, it will want to twist to a washout position. This is made worse by the lack of torsional stiffness of the wing due in part to there being no top rear spar. The rear has only a bottom balsa spar. As noted here somewhere, the struts are very functional as designed. They are needed for strength of the wing in bending, and would hopefully prevent washout from twisting under load.

To get around all these problems, I have ordered a carbon fiber wing rod with phenolic outer tube. It is 36" x 1" with .042" wall. I will mount it at the CG position. The ribs will be drilled for the rod on a drill press as a stack, with the dihedral set by offsetting the stack. The first two balsa ribs outside of the 1/4" ply ribs will be replaced with more ply ribs. The added ply ribs are spaced just right to use the entire 36" rod. I am also adding a top rear spar of 3/8" x 1/4" (identical material to the front spars) above the large balsa bottom spar.

The effect of all of this is (1) torsionally stiffer wing and (2) stiffer wing in bending, with forces at the center of lift through the rod. The greatly stiffer wing could fly with no struts at all. I will of course add them for scale fidelity, but don't have to worry about a strut failure causing loss of the aircraft. The plane will build faster this way, be easier to assemble at the field, and weight gain from all this will be very little if any. The CF rod is very light. I will add a couple of nylon bolts through the cabin root rib to the first wing rib to hold the wing in place on the rod.
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Old 03-09-2015, 01:41 PM
  #54  
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Hello littlera. Just wondering if you started your cessna 120 yet. I have one on the work bench right nown . Fusage halve done. Right wing started. If all possible could post some photos. Thanks hank ....
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Old 03-09-2015, 02:20 PM
  #55  
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Hot Coals,

I have not started building my kit. In fact, I need to finish three other planes first, which I should be able to do this year. My plan now is to start construction of the Cessna next winter, maybe around Christmas.

I get this kit out occasionally, which is what I did recently, discovering I needed to make some more wing ribs. This is when I did the wing redesign. My CF rod and outer tube arrived Saturday. This was from TNT Landing Gear products. Nice set, but was not really happy with the clearance between the rod an tube. I wrapped a layer of clear tape around the CF rod, and the resulting fit is much better now.

One thing I did about 6 months ago was to make scale wheels with wheel covers. I used Sullivan Sky Lite wheels (4 1/2") and cut scale flat aluminum wheel covers. These were screwed to thin plywood rings glued to the side of the wheel hub. I had to grind down the hub some to enable the wheel collar to be hidden. It is just a few thousandths under the wheel cover. These look fantastic! I was very pleased with the outcome.
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Old 03-09-2015, 03:38 PM
  #56  
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Here is the wheel with wheel cover.
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Old 03-16-2015, 08:52 PM
  #57  
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Hi, littlera. Looking at the wheel, is that a aluminum insert?. Look's good. I havent done much on my cessna 120. Since brother suffered another stroke in n.j. . Ill try to seen some photo's of what i did so far. I have a new saito 182 twin going in. And a o.s. Gt 33 going in the other.
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Old 03-17-2015, 03:16 AM
  #58  
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It is a piece of flat aluminum sheet metal cut in a circle. This material was bought at a hobby shop. I think it is about .020 thick, made by K&S. It is screwed to a plywood ring that was glued to the wheel hub with P.F.M glue.
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Old 03-25-2017, 03:13 AM
  #59  
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Not sure if anyone is still reading this thread, but thought I post some pictures of my friend and my build..

We changed the wing design to a one piece wing for strength and ease of mounting. We have 1.25+ incident also. Yes... it's a very long wing for transportation... The fuselage has a lot of wood and we've done many changes to it also.. we build for light weight...

A question for you all... why does the stab/elevator have a negative angle to the fuse center line? How have you found the flight characteristics?

Thanks - Grant

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Old 03-25-2017, 04:46 AM
  #60  
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Grant, the simple answer about the negative incidence for the horizontal stab is that this is the angle found to be correct for working with the wing at its angle of attack. I can tell you that this negative incidence is scale. The real C 120/140 has the exact same. There is a drawing floating around the internet that shows the incidence angles.
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Old 03-25-2017, 04:59 AM
  #61  
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Originally Posted by littlera View Post
Grant, the simple answer about the negative incidence for the horizontal stab is that this is the angle found to be correct for working with the wing at its angle of attack. I can tell you that this negative incidence is scale. The real C 120/140 has the exact same. There is a drawing floating around the internet that shows the incidence angles.
Thanks... We kind of figured that was the case.. What have you found to be the flight characteristics to be?
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Old 03-25-2017, 05:17 AM
  #62  
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Unfortunately have not really started building it. Have two projects to finish first. Maybe next winter.
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Old 03-27-2017, 07:20 AM
  #63  
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Keep at it Grant we're still watching!

Mike
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Old 04-20-2018, 08:44 AM
  #64  
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Is anyone still building this kit? I just purchased this kit.
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Old 04-20-2018, 09:04 AM
  #65  
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Walter, the original thread started left the forum. Grant has a friend building this airplane for him and last I heard littlera hadn't started he had two other project going. (A lot of that going around on this forum). I think if you are willing start your build here and maybe we can get it going. I have other projects so I won't be posting a build here but I will chiome in when I see an update or question.

Mike
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Old 07-31-2018, 08:36 PM
  #66  
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I am scratch building Burnis Field's version of the Cessna 140. I started this in 1991, when the construction article and plans first became available through RCM. 27 years later... I have returned to this project!! I finished the wing panels, and am in the process of hanging the wings.

Last edited by ExtraCGScott; 07-31-2018 at 08:39 PM.
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Old 01-31-2019, 11:43 AM
  #67  
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Anything new here?
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Old 02-16-2019, 09:30 AM
  #68  
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Default Some progress

It has been a while, but am thinking about where I left off last summer. Here are a few pictures of current progress


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Old 02-16-2019, 09:36 AM
  #69  
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After hanging the wings, I went on to begin planking the fuselage.
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Old 02-16-2019, 09:40 AM
  #70  
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Default fuselage




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