mesaflyer

Well, a few months ago my son was flying my/his 4 Star 120 when he had a couple "heavy landings". I guess that after a few of these, the tail section must have cracked, and I did not realize this. Because a few weeks ago, I was out flying it and after a couple laps, I made a hard left turn and the complete tail section snapped off in the air. The plane has a CRRC 26cc gasser, and I could still hear this loud BANG, followed by the plane slowly spiraling to the ground. I killed the engine before it hit. Since it went straight in, the nose broke off as well. The wing did not get hurt. At first, I was going to trash it, but instead, I brought it home and put it up on the shelf for a project someday. So now I have have epoxied all the pieces back together, and added some extra ply to the tail. One mistake that I made was not making sure that the tail section is not twisted in relation to the fuse. In other words, the elevator is slightly angled in relation to the wing, and the fin is not 90 degrees to the fuse or wing. I would say it's off by about 2-3 degrees. I did not notice my mistake until I was about completed with the re-covering.

So I was wondering what effect this will have on it flying? I figured it will be a little out of trim, and will probably corkscrew on the loops?

Anybody have any experience with this?

I attached a few pics, one of what it used to look like, and a couple of the repair job. Once I get it all back together, I'll post a pick of the tail in relation to the wing.

Mr67Stang

Yes, you will likely get cork screw loops but might be able to trim it out. It will be different. I had one that was worse than yours and loops would result in about a 50 foot latteral drift or just a spiral if I pulled to hard on the elevator.

I too have a 26 cc gas powered Fourstar 120 that has cracked in the same location. Imediately in front of the rear stabalizers. So I too need to make this repair. I discovered the stress crack before flying it again so fortunately I will not be doing a rebuild. These are great airplanes and worth the effort though. Keep the pictures coming I will be interested in following your progress. Maybey it will motivate me to start on mine.

mesaflyer

Now that I have it all back together, I see how much I really did not pay attention to how crooked everything is. I have a lot of personal issues going on right now, so I'm going to blame it on lack of sleep. That's my story and I'm stickin' to it.

Here are a few pics of it finished. The tail section is twisted in two directions. Should make for some interesting flying. Unfortunately, when the plane went in nose first, it bent the prop shaft and I did not know this until I tried using my starter on the engine. Looking into getting the parts to fix that. If I get the engine fixed, I'll post an update on how it flys.

Seems like I read somewhere that several guys have had the problem of the tail section cracking or breaking. If I had it to do over, I would probably take the time to "rebuild" the tail section so that former F-6 (I think) is a little narrower allowing for some plywood stiffeners on the inside of the rear of the plane. Or at least, square up the pieces on the outside to make it easier to cover. Those round pieces were a son-of-a gun to make look decent. You can see that I just used the pieces that were punched out of the fuselage side pieces from the kit.

I just used scrape pieces of covering that I had left over from other kits that I built.

A couple things I changed: the front bottom ply piece broke out in one piece, so I ended up cutting it in half and making a hatch for the batteries and ignition under the gas tank. This also allowed me to remove the 4 oz lead weight that it had up front. The golden rods that came with the kit worked good, but every time the plane went in the air I had to adjust the trim because they shrink and expand with the weather. They were bent in the crash, so I replaced them with 4-40 control rods.

I'll post an update when I have one.

Mr67Stang

I attached pics of my 4 Star 120. I used two servos, one for each elevator half, relocated to the rear of the fusalage. I am hoping I might be able to get in through the servo cut outs and weld my stress crack with epoxy and triangle stock. I bet the crack though is on the back side of that last former. I realy do not want to peal up this covering[:@]

mesaflyer

Yea, I hear ya. I wouldn't want to remove that nice covering job either. Beautiful plane.

But as the saying goes, better safe than sorry.

The plywood sides and bottom was "torn" apart at the last former.

I think that is a real weak spot right where the last former is. With those large cut outs, there just isn't very much wood back there.

Of course it's only weak if you make hard landings on asphalt. [X(]

mesaflyer

Well, got to fly the 4 Star this weekend. I can't even tell any difference from before the crash to how it flys now. Just a great Sunday flyer.

It is a lot nicer with regular 4-40 control rods instead of those golden rods that it came with.

I did several loops, and although they were not perfect, they were perfectly fine for this plane.

One other item that I had to change was the prop shaft on the CRRC 26. It had a slight wobble to it, so I asked Jody at VVRC if he had one. He said he did not, and to contact Jim at Agape Racing and Hobbies. Jim had one and sent it out right away, hand gave me a few pointers on how to change it out. Nice guy. Thanks Jim.

oskartek

What kind of problems did you have with the Golden Rods?
Would you do the 4-40 rods inside tubes?
I am presently building a 4*120 and have not yet installed the control systems.

Many thanks.
Happy flying, Oscar

mesaflyer

Oscar,
The Golden rods expand and contract (get longer and shorter) with the cold and heat. Some days when it's real cool in the morning the rods have changed several clicks of trim from the last time it flew, especially if it was warm the last time out. They will even change a couple clicks from one flight to another. It's really just a minor inconvenience to have to re-trim almost every time the plane goes up.

I installed the tubes that came with the 4-40 rods because they are smaller in diameter than the ones for the Golden rods, and the original Golden rods were bent in the crash. This is what installed. http://www3.towerhobbies.com/cgi-bin...3718&search=Go

mesaflyer

Oh, and just because I thought this was kinda funny. I ordered the 48" rods, a prop, and some epoxy from Tower. I did go to 3 of my LHS, but no one had 48" 4-40, which is understandable.

Not sure what the person who packed my order was thinking, but they did not know what the rods were for. They bent them in order to make them fit into the box in the picture.

I called Tower, and they sent my a new package the next day. Really good customer service at Tower.

foodstick

I am not surprised your four star still flies well. They are some pretty stable fliers ...and can be very forgiving.

mesaflyer

Yea, funny thing is, one of the guys at my club suggested that I get a large plane that flies well with no cowl for my first gasser. So that's how I ended up with the 4 Star. Now it's one of my favorite planes.

oskartek

mesaflyer,

Thanks for your info, I thought this was the case as I have heard of the temp problems somewhere before.
I'm planning to go with a pull pull cable system for the rudder and probably the 4-40 rod for the elevator.

Built a 4*40 when I was doing RC back in the mid eighties to mid nineties, it was one of the best planes I ever flew.
Just got back into the hobby a couple of years ago and decided to fly stuff around 80" wing span.

I remember the 4* was a real floater so I am adding Dauntless style air brakes/ flapsto help spoil some of the lift
when landing as I am no longer flyingfrom a dry lakebed and have to focus on using a runway.

Also sheeted the upper and lower leading edge of the wing back to the main spar, that really stiffens up that wing!

Many thanks.

Happy flying, Oscar

noveldoc

My Feedback: (2)

Friend did a neat thing with the 4 Star.

He set up the flaperon mix and then centered aileron on middle switch.  That way he could switch down for take off flaps and up for landing spoiler.

Tom

mesaflyer

I just might have to try that.

Flew it again today. My plane will float, but not forever. I think part of it has to do with the gasser up front. A little extra weight, low rpm's, and a bigger prop can make for some really slow flying, if I want to. I can cut to about 1/4 throttle and just do really slow fly-bys as long as I don't turn too sharp.

The size of the plane along with this slow flying is what kinda got my son in trouble. He kept landing slower and slower and eventually just stalled it about 3 feet above the runway. Made a for a few pancake landings.

mesaflyer

Oscar,
Your welcome. I taught myself how to fly off of a dry lake bed, and some days I really miss that. Sure made for some interesting landings when my son and I joined a club and we had to land on a run way!

I almost did the pull-pull rudder just for the experience, but decided to just use what came with the kit.

The Dauntless had split flaps/air brakes, so you are going to loose some of the ailerons and replace them with flaps?

If that's the case, keep in mind that this plane does not have a real high roll rate, so you might loose some real maneuverability.

Just a thought.

noveldoc

My Feedback: (2)

You should still keep full aileron function with flaperons.  They are mixed.

But your Dauntless setup would do much more flap or spoiler.

Tom

oskartek

noveldoc,

I plan on keeping the full length ailerons, the airbrakes will be 16" X 3" with two rows of 9 one inch holes separated by a row of 8
one inch holes along the center line.The trailing edges to be at the trailing edge of the wing just before the leading
edge of the aileron.
Am using the Nelson Hobbies miniature piano hinges to aerodynamicaly seal the leading edge of the airbrake to prevent flutter.
Being that the wing has two servos I could still mix in flaperons although I'm not sure of the effects or effectivness.
Who knows, it may not work worth a crap. But ya don't know till ya try.

Here's what I have so far,

Happy flying, Oscar

mesaflyer

Oscar,
Sounds like you have a good plan there for the air brakes. Let us know how they work out.

I learned to fly with a Nexstar, which has those plastic air brakes (similar to your design) that just screw onto the bottom of the wing. They definitely slow the plane down. I flew my first three flights with them on, and then removed them. I never re-installed them after that.

Nice looking build you have there. What engine are you using?

oskartek

Tom,
The engine is a YS FZ 140 Sport, I'll be running that with a Dubro 20oz tank.
Been flying glow engines since I was a kid and kind of like that way.
Aso went with the Sullivan tail wheel.
I have a good idea on the colors and graphics, havent decided on the brand of covering.

Happy flying, Oscar

Mr67Stang

After reading this thread, I hope you reinforce the fuse at the last former. I wish I had

mesaflyer

Plus one!

I know that I read somewhere that some guys were not removing the last cut out, and then just using epoxy to fill in the cut lines. Not sure if that would do much, because where you have the red circle is where mine broke.

oskartek

I have also read of a weak area in the fuselage right behind the trailing edge of the wing.
Will reinforce these areas while adding as little weight as possible.

Am also going to taper the elevator and rudder, removing material equally from both sides.
The ailerons will be tapered on the top thus keeping with the semi flat bottom wing.

Thanks for the tips guys.

Happy flying, Oscar

nobodytwo

The "stress fractures" may be caused by excessive vibration from the gasoline engines. After all the fixes, the next thing that may fail could be the hinges on the rudder or the elevator. Hopefully, ya'll have used nylon hinges and pinned them.

Certain props can set up vibration harmonics and really shake the fuse. The harmonics may show up on the lower end of the rpm range. Others have found that lengthening the prop and reducing the pitch are helpful in reducing the shake.

I've had six incidents of vibration damage: 1) lost one elevator, 3 &4) same rudder twice (robarts came loose first time, then sheared off the second time). 5 &6) Both GP giant stiks; the tail feathers completely coming loose. (Preflight caught the problem).

Happy Landings!

stevenmax50

My Feedback: (1)

Does the 120 have a 2 piece wing?  I'd like to know due to transportation issues.  I am deciding between the 4* 60 or 120 for my next build.

stevenmax50

My Feedback: (1)

Good to know. I am thinking of building the 120 as my first gasser. Obviously, after reading this thread there should be some stiffeners added in at least two areas. Just forward of the aft stabilizers and just aft of the wing.