NitroModels Yak 54 3D 50 Stab Failure (Full Version)

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Wing-Ding -> NitroModels Yak 54 3D 50 Stab Failure (5/21/2007 2:04:56 AM)

Well, I maidened the NitroModels Yak 54 3D 50 today. The first flight was uneventful and the plane handled nicely. The second flight, however, was not so uneventful. I did a four-point roll and then a nice, large loop with about 2/3 throttle on the O.S. .55AX. Then was going straight and level at near full throttle when all of a sudden, I watched in horror as I could see a control surface come loose and fall to earth.

I throttled back, brought the Yak around and unbelievably, was able to land. Upon inspection, I saw that the horizontal stabilizer had fractured on both sides of the fuse and that one of the elevator halves was missing!!

I read about problems with a weak horizontal stabilizer in other forums. So, before purchasing the Yak 54 3D 50 ARF, I called and talked to a guy at NitroModels and he assured me that the new ARF's had a reinforced horizontal stabilizer. I was a bit suspicious and even had a flying wire kit on order before I flew today. I thought that if I only flew some easy pattern stuff today that there would be no problem. Was I wrong! It is clear that the problem with the weak stab is not fixed! Can you please send me a replacement stab free of charge? My Order Number was: 177450.





opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (5/21/2007 2:54:18 AM)

I have a Nitroplanes CMP Passion 3D which came with the weak horizontal stab problem.

The wood used on the stab cross-member was soft balsa.

My left and right stabs ripped out in flight w/o any hard moves, one week after the other.

Since I was able to get the plane back down w/o damage I uncovered the stab and replaced the soft balsa with hardwood.

I haven't had a problem since.

You may want to uncover the cross brace where the hinges go into.

See if it's hardwood/basswood or soft balsa.

If the latter, PM them for a replacement, then UNCOVER the replacement.

If it still is soft balsa, you may be forced to fix this yourself.

IMHO this is an oversight, or design flaw.

The large control surfaces should not be held into the softer balsa.

No matter how much CA you wick in, it will NOT be enough.


PM them here as well.





Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (5/21/2007 3:26:27 AM)

I just uncovered it and there it was. Yep, in fact it is just soft balsa. I agree- it's definitely an oversight / design flaw to use soft wood at a high-stress point. Thanks for your suggestion. I will PM them to see if I can get them to replace the stab / elevator. I will beef up the replacement appropriately.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (5/21/2007 7:27:32 PM)

The advertising says "re-inforced tail".

Either this area was not beefed up, or you received the older model.




Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (5/21/2007 7:33:12 PM)

Not sure. I do have the updated color scheme which I thought indicated the new model. The tail is definitely not reinforced in any way. I PM'd them. Still waiting to hear something.



nitrostaff1 -> RE: NitroModels Yak 54 3D 50 Stab Failure (5/22/2007 12:23:28 AM)

Guys,

Yes it is true that the tail horizontal stabalizer was reinforzed but i guess the material choice was not adaquate. Problem noted!



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/4/2007 5:00:18 PM)

A quick fix for this which I would advise to anyone purchasing the plane, is simply to add additional CA hinges.

In other words you want to spread the load out a bit more.

Cut a couple of thinner CA hinge strips to make two 1/4 to 3/8 inch wide strips and insert them as well in addition to the provided hinges.

Hand drill out a small center hole to provide for better CA adhesion then cut and install the provided and the two additional hinges.


That should eliminate the minor problem.




Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/4/2007 5:45:11 PM)

John from NitroStaff support said he told the factory about the weak stab problem and that it would be 4 weeks before he could send me a reinforced one. I want to get back into the air sooner than that so I opted for an identical replacement stab that I will reinforce. Since they were out of the red color, he was only able to send me the older color scheme (mostly blue).

I received it last Friday. I will uncover and reinforce with hardwood and ply. Think I'll use either robart point hinges or Dubro heavy duty hinges. I also have a flying wire kit that I plan on using.

I noticed the threads on the small-diameter machine screws that hold the control arms on don't really have enough bite and that they loosened a bit on the rudder (stripped out of the backing plate). Maybe the primary failure mode here is flutter causes by loose control horns. I plan on replacing the stock control horn hardware that includes nylon lock nuts.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/4/2007 6:25:27 PM)

Yeah, that would be another reason to also advise more hinges if you are using the CA ones.




Jerry Sigur -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 12:42:48 PM)

My elevator halves are thicker than the stab, this will cause flutter probs
at higher speeds and structual failure. I plan to build a stab to match the halves.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 4:36:06 PM)

Why not seal the hinges?




Jerry Sigur -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 5:20:24 PM)

Sealing the hinge gap will help but not fix the prob. The elevator halves
should not be thicker than the stab, this causes problems.



Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 5:31:25 PM)

I wasn't aware of that. I'll make sure they're not larger. Thanks.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 6:42:58 PM)


quote:

ORIGINAL: Jerry Sigur

Sealing the hinge gap will help but not fix the prob. The elevator halves
should not be thicker than the stab, this causes problems.


I agree, but at the same time it is also ok ( of course not in this case ) if the elevator follows the stab airfoil shape too... for those planes equipped with airfoils instead of flat balsa.




Jerry Sigur -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 7:00:10 PM)



I agree, but at the same time it is also ok ( of course not in this case ) if the elevator follows the stab airfoil shape too... for those planes equipped with airfoils instead of flat balsa.


[/quote]

Umm, sure, why not? An airfoiled stab and elevator should provide
smooth transition for the airflow.



Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/8/2007 8:14:22 PM)

What do you have your elevator throws set to? The instructions call for +/- 40mm, but that seems like a lot. I guess maybe not for 3D- but I'm not sure this plane can handle 3D.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (6/9/2007 6:45:51 PM)

With an "unknown" plane I set the high rates to the recommended, and then the low rates to about 50% of that on the elevator and ailerons...

Rudder I always leave at 75% on the low rates.

That way if the plane is unresponsive at take off I can quickly flip to the high rates.

Once in flight ( at altitude ) I then can check out the recommended rates and see if they are enough or too much.




Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/2/2007 2:04:57 AM)

I flew the NitroModels Yak 54 today after having rebuilt the stab. I'm quite pleased with the way it flies. The replacement stab that NitroModels sent me was the old color scheme (as I requested since I didn't want to wait weeks for the newer color scheme and reinforced stab). It must have been a reject for cosmetic reasons as the checkerboard pattern and trim was really peeling off. Not a huge deal and at least they are the same colors- only the red and blue are reversed. I reinforced the stab with hardwood at key locations and put in DuBro nylon hinges instead of the CA hinges. It doesn't show in the pictures but I also added hardwood to the leading edge. It balanced fore and aft perfectly without adding weight (O.S. .55 w/ Jett Engineering in-cowl muffler) although I needed to add 35 grams of weight to the left wing for lateral balance.

Marl



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/2/2007 3:32:06 AM)

I flew a brand new Ultrafly Reactor 3D EP yesterday.

On it's first flight a radio "hit" caused the stab to pull up hard during level flight at mid throttle.

The stab self destructed.... it split at the root on both sides!


The problem seems to occur with many planes from many different manufacturers...


The stabilizer on planes with big control surfaces needs to be pretty durable... Bassword or Balsa just doesn't cut it.

Morale of the story... re-inforce with CF support struts whenever possible!





McCoy -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/8/2007 2:14:00 PM)

I Flew my yak for the first flight yesterday the stab came apart. The only problem here is poor constuction and cheap balsa in the stab. They should test some these kit to see wants going on. Some is going to get hurt with there carelessness.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/8/2007 7:38:00 PM)

As posted above NP is aware of the problem.

In the mean time, it is advisable for anyone buying the ARF to put in CF support struts, which is cheap and easy to do.

I regularly do this with most of my large control surface planes.





Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/9/2007 9:57:17 PM)

I flew the Yak 54 twice this last Saturday and both flights were quite enjoyable. I did have one scare when I heard a fluttering sound while flying by. Turned out it was just some trim coming off the right wing. Here are a couple more pics of my modification.

Marl



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/9/2007 10:02:21 PM)

Don't you want the wood grain to run 90 degrees to where you have it?

I'd imagine that as is the torsional forces will be along the wood grain... though ANYTHING that adds stiffness is going to help a lot.




Wing-Ding -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/9/2007 11:05:33 PM)

There are three hardwood pieces which run roughly 90 degrees to the fuselage. They provide the main structural reinforcement. The rest of the wood shown in the pics is either supports for, or are thin balsa sheeting.



opjose -> RE: NitroModels Yak 54 3D 50 Stab Failure (7/10/2007 12:35:26 AM)

Gotcha...

Nice job.




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