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4*120 Build Thread

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4*120 Build Thread

Old 04-11-2016, 07:59 AM
  #926  
lamarkeiko
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It's taken me awhile, but I have finally completed all the painting. My final weight of all the painted components without anything else installed except Robart hinges is exactly 90 oz. That was a gain in weight of 15.5 oz from bare wood. The Koverall and Minnwax sealing added 11.4 oz and the Rustoleum paint job only added 4.1 oz of weight. I was really expecting more weight added from the Rustoleum. 90 oz = 6lb 4oz. I'm hoping my final weight after everything is assembled will be in the 10.5 - 12 lb range as stated on the Four Star 120 specs range. It is just assembling and balanceing left to do.
I'm working on reinforcing my landing gear now, before I install them. The supplied lg in the kit seem very weak.

Lamar
Old 04-11-2016, 03:33 PM
  #927  
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Are you referring to the mount or the aluminum gear itself? It does weaken over time if you slam it down on landing(not mentioning who) It is splayed out on mine now, but still lands fine.
Old 04-12-2016, 08:58 AM
  #928  
lamarkeiko
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I'm refering to the landing gear. I think it will splay out very easy. I'll post a picture of what I've come up with when I'm finished.

Lamar
Old 04-13-2016, 05:49 AM
  #929  
FlyerInOKC
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Originally Posted by lamarkeiko
I'm refering to the landing gear. I think it will splay out very easy. I'll post a picture of what I've come up with when I'm finished.
Lamar
The splaying out is to absorb the impact of a too firm landing to prevent damage. Make the gear to rigid and something else absorbs the energy either by breaking or tearing out the gear or at the least by some serious bouncing and possible flipping of the aircraft. Just my 2 cents.
Old 04-14-2016, 09:57 AM
  #930  
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Originally Posted by FlyerInOKC
The splaying out is to absorb the impact of a too firm landing to prevent damage. Make the gear to rigid and something else absorbs the energy either by breaking or tearing out the gear or at the least by some serious bouncing and possible flipping of the aircraft. Just my 2 cents.
^this^ Its built in suspension, however, a few too many said hard landings eventually will cause a permanent splay, at which point it calls for replacing the gear.
Old 04-14-2016, 10:36 AM
  #931  
FlyerInOKC
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Originally Posted by acdii
^this^ Its built in suspension, however, a few too many said hard landings eventually will cause a permanent splay, at which point it calls for replacing the gear.
I know my old LT-40 trainer has had to have the gear bent back in a time or two because the nose was getting a bit high! That was why SIG designed it that way. I love the Robart Cub gear it makes the most beautiful landings.
Old 04-14-2016, 12:28 PM
  #932  
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The 4* has an aluminum gear,


Problem with hardened Aluminum is once the original shape is lost, there is no way to get it back without retreating it.

You can get a 3rd party 3/16" thick gear for $45 from tntlandinggear.com.

My LT-40 is a tail dragger, and has a nylon gear with lots of spring to it. I don't think I have ever had a hard landing with it, except the one time I missed the runway and plowed into a plowed row of mud, ripped the gear right off. Good example of why nylon bolts are a must. Had new bolts in and flying 5 minutes later.
Old 04-17-2016, 06:51 AM
  #933  
lamarkeiko
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Got the LG reinforced. It is much stiffer than original. I used some 3/32" control rod stock I had and soldered terminal lugs on the ends for attaching to the LG. Flying and landing will tell how well they work.

Lamar
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Old 04-17-2016, 07:30 AM
  #934  
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Looks good, hope it works out for you, but don't be surprised if something else cracks on a hard landing. Mine tends to land hard at times, and if it weren't for the give the gear has, pretty sure something would have cracked or busted by now.

My SIG Cub on its maiden flight landed hard, and its gear is not as giving as the 4*, and when it hit I heard something crack, sure enough the wing mount on the fuse busted right where it joins to a former. The worse that can happen with my 4* is the prop clips the ground and kills the engine.
Old 04-17-2016, 02:12 PM
  #935  
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Get it in ground effect and hold it off like a butterfly with sore feet, you will never have a problem.
Old 04-18-2016, 08:18 AM
  #936  
lamarkeiko
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Originally Posted by kmeyers
Get it in ground effect and hold it off like a butterfly with sore feet, you will never have a problem.
That's the plan. I think if I do have an extra hard landing, that my support braces will give out before the LG tears off the bottom.

Lamar
Old 04-18-2016, 08:51 AM
  #937  
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Originally Posted by kmeyers
Get it in ground effect and hold it off like a butterfly with sore feet, you will never have a problem.
If you have enough runway and a good approach that doesn't require a drop of 7' to clear the corn, this works quite well. I run out of runway long before it settles down.
Old 05-21-2016, 08:54 AM
  #938  
lamarkeiko
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I've finally finished my Four Star build, so I'll post some final figures and pictures. I actually finished about 3 weeks ago, but my computer was in the shop for repair, so I couldn't post. I am pleased with the final finish, but I haven't gotten it into the air yet. Between the weather and getting the new engine tuned well, I'm slow to maiden. This is my first gas engine, and the biggest plane in my hanger. Too much time invested, so I need conditions as good as possible. a lot of my build has already been posted on this thread, but I'll give a basic list of my build.

Final wing span with one rib bay removed: 72"
Final weight, ready to fly: 11lb 10oz
Engine: Valley View 20cc
Covering: Sig Koverall, applied and sealed with Minwax Polycrylic
Final paint: Rustoleum Sail blue and Rustoleum Sunburst Yellow

I was always concerned throughout the build to keep the weight as forward as possible so I wouldn't need to add any nose weight. As I turned out when finished, my CG came out at 4 1/4" from leading edge without any weight added. This is right in Sig's recommended range.

Lamar
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Old 05-21-2016, 09:26 AM
  #939  
Super08
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Congrats, it turned out beautiful. I hope all goes well on your maiden flight.
Old 05-21-2016, 10:50 AM
  #940  
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It is a beautiful plane...

But, I don't like the long unsupported golden rods in the radio compartment. Actually I don't like the golden rods and rudder and elevator horns at all. Lets just call this a 12 lb plane. I wouldn't use that stuff on the biggest plane in my fleet.

Put my mind at ease by holding the elevator still and applying full up elevator while you observe that linkage inside. If it bows out easily instead of the servo stalling, you may need some beefier stuff or at least a brace in the middle.

If not I guess you will be ok.
Old 05-21-2016, 10:57 AM
  #941  
Super08
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I have used those HD ones before and they are extremely stiff and strong. He shouldn't have any problems with them. They are twice the diameter or so of the regular red or blue ones. I would imagine they are braced in the rear fuselage as well. The horns could be an issue though in time.

Last edited by Super08; 05-21-2016 at 11:19 AM.
Old 05-22-2016, 07:12 AM
  #942  
acdii
 
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Originally Posted by kmeyers
It is a beautiful plane...

But, I don't like the long unsupported golden rods in the radio compartment. Actually I don't like the golden rods and rudder and elevator horns at all. Lets just call this a 12 lb plane. I wouldn't use that stuff on the biggest plane in my fleet.

Put my mind at ease by holding the elevator still and applying full up elevator while you observe that linkage inside. If it bows out easily instead of the servo stalling, you may need some beefier stuff or at least a brace in the middle.

If not I guess you will be ok.
This is why I put my servos in the tail and use pull-pull for the rudder. Those long pushrods are a PITA. I do use Golden Rod in my Cub though, but it is supported at every frame so its stiff, but the rudder is also pull-pull. I do that on every plane I can.
Old 05-23-2016, 03:58 AM
  #943  
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I use that black Sullivan rod in most of my giant scale applications. It's easy to install and to set up. In my opinion, if problems occur, the builder is to blame, not the product.

These models all have Sullivan pushrods. All are over 100" wingspan. I have complete confidence in them.
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Old 05-23-2016, 04:05 AM
  #944  
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I do agree that Lamarkeiko needs to alter his installation. The metal rod should be inserted at least 3-4" into the inner rod, well into the area covered by the outer rod. The installation, as it is currently, will not sufficient to sustain safe flight.
Old 05-23-2016, 05:38 AM
  #945  
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I have re-read my post and need to walk back or clarify my comments.

I love Sullivan products. I use "golden rod's" in a 17 lb plane. They are supported to every former they pass and have extra supports created where long runs or exits out of the plane create unsupported lengths. I also have the metal ends go as deep as needed into the rod to go past the first brace out of the servo and before the control horn.
Old 05-23-2016, 07:34 AM
  #946  
lamarkeiko
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Thanks everyone for the replies back on my control rods. They are the stock kit rods, and are much stiffer than Sullivan Golden rods. I did do as kmeyers suggested, by holding the elevator and rudder to see if there was flexing with servo input. There was big time flexing. I added another brace and tested again, and there was no flexing. I could still do more by inserting a 4-40 rod into the inner pushrod hole on the servo end as far as I could go to help stiffen up even more. The control horns for rudder & elevator are the stock horns as supplied in the kit. It has never occured to me that they should be heavier duty.
Thanks again for spotting the weak spots in my build.

Lamar
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Old 05-23-2016, 07:38 AM
  #947  
lamarkeiko
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Forgot to mention, that the rods on the rear do have 4-40 metal rods in the inner rod extending into the fuselage.

Lamar
Old 05-23-2016, 08:19 AM
  #948  
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There is a discussion on the FB Balsa Builders page RE: the 4*120 and clipping the wings. Irks me when others ASSume you dont know how to land a plane. The 4*120 is a floater, and if you have a short runway, especially one that is boxed in by corn like mine, landing one is a real challenge, no matter how good you are. Clipping the wings one bay doesn't 100% resolve the problem, but helps quite a bit, while also enhancing axial performance. Had a few others agree with me on this one too. Even with flaperons active, it is a challenge to get it down from at least 15' altitude, drop to the ground in 20' and then slow enough to land it while having room to stop without going into the crop at the other end. It's one of the reasons I haven't flown it much, it has to land at some point, and unless I am at a place with enough runway, I don't fly it.

I flew it at the SIG flyin last year and had a dead stick(Dummy me forgot to top off the tank after tuning it!), and it was far up and out and I did not think I would make it back, but It did, barely, it came in between some trees and just brushed the tall grass at the side of the runway, and touched down on the strip.
Old 07-10-2016, 05:47 PM
  #949  
the Wasp
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hey Guys, for along time now I have been wanting to show you my plane,, while yes it's only a 60, it is still a 4-Star,

it was crashed around 10 years back, gave it to a friend, he never fixed it so I got it back, and while I have a thing for things different, and for open cockpit planes I decided to bash it to look like an old open cockpit racing plane, I'm thinking about calling it "Charley Horse 17" LOL

the first thing I did was to move the Cockpit back (maybe to much, what do you guys think ??) and make it an open Cockpit, at that I had to do something with the upper front deck, and rounding the top of the front deck didn't seem correct because the side of the plane are flat and square, so I angled the upper front deck, while surely it is different I think it looks neat, what you think,,

I plain to shorten and round the tips of the main wing, round the top of the rudder and the tips of the tail wings... from the cockpit back it will be covered yellow, the first 5 or 8 inches of the fuse (and including the full engine cowl) will be covered in large B/W checkered, the middle around the cockpit will be covered in a soft red or an orange to blend into the yellow,, the main wing's bottom will also be covered in large B/W checkered, but I am also thinking the whole main wing would look good completely covered in large B/W checkered (what do you guys think ??)

Engine; I would really like to put a 4-St in it, a 91, 95 or even a Saito 100,,,,, but I want it fast, so I am also thinking about putting a 2-St 91 in it with a larger than stock muffler or a tuned pipe, and I do have a Mack quiet tuned pipe setting on the bench,

I know some of the hard core guys wont like it, but hey, it's my plane..

tell me what you guys think

Jim

PS, see my photos below

Last edited by the Wasp; 07-10-2016 at 06:11 PM.
Old 07-10-2016, 06:10 PM
  #950  
the Wasp
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photos of my 4-Star 60
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