ez2bgman

My Feedback: (4)

How many people have experienced an inflight horizontal stab failure with their Aresti 40? It happened to me today on only it's 3rd flight. Luckily I had plenty of altitude and greased the landing (although she came in a little hot). I was inverted and on the down leg of an approach when the left horizontal stab and elevator broke off cleanly at the fuselage and floated back to down. At the time, none of us knew what came off until I rolled upright and saw the whole left half comepletely gone. I was at approximately 75-100 ft. I instinctively flipped on high rates and flew the down leg. Chopped the throttle and began a steep banking dive to the right to line up for final. I thought I was going to lose her on the dive, but I was "flying ahead" of the plane and anticipated it wanting to roll to the right as I inputted up elevator. I counteracted it with left aileron and leveled her out just a few feet above the weeds at the edge of the runway. Due to the steep dive, she was coming in fairly fast. I continued to hold up elevator and left aileron and flew her all the way down. Touched the mains and let her roll out. She finally stopped at the other end of our grass field. During the turn to the pit area, the tail wheel hit a bump and she nosed over in the grass. Other than the horizontal stab, nothing else was damaged. I am extremely fortunate to still have her in one piece. I think I can attribute my quick reflexes to many, many hours of Real Flight G2. The very experienced pilots at the field commended me on an outstanding job bringing her down with only the right horizontal stab and elevator.

I am definitely getting on the phone ASAP with Horizon Hobby about this horizontal stab. I was extremely carefully removing the covering when I epoxied it in. I used my professional soldering iron to cut the Ultracote instead of my exacto knife. I know I did not weaken the structure in any way. Any input on this is greatly appreciated. Thanks.

Gary

Tall Paul

I had a similar failure on my Wacky Waco... but the horizontal parted right on the line I'd scored in the outermost fibers of the wood when removing the covering.
I've other such collapses, due to a failure by the builer to use a reasonable spar across the fuselage in the horizontal.
The down-load can be quite high, and improper material/ construction can fail in flight.
Like you I didn't notice the loss of the right side.. fortunately the pushrod connected to the left half.
When I did observe it looked odd, I made a -gentle- approach to the landing.
The fix involves an aluminum tubing brace on the bottom of the horizontal to the bottom of the fuselage on both sides.

jettstarblue

Hey, at least it didn't look like this, which was caused by radio failure, and there was no chance for heroics.

ez2bgman

My Feedback: (4)

I think I'm going to make another Hor. Stab myself and beef it up in the leading/trailing edges and the make a solid center section to glue into the fuselage. Other than this failure, the plane flew great. I am very pleased.

Gary

jettstarblue

BTW,
What engine are you running? Mine flew really well with a .52 FS- Not overpowered, just nice.

ez2bgman

My Feedback: (4)

jettstarblue,

I am running an O.S. 50SX. Not overkill, but a perfect balance between vert. and speed. I am thinking about building my own solid horizontal surface or making another one like the original but more beefed up. Any ideas?

Gary

jettstarblue

Yes, just like the original, but with a pine L.E. instead of balsa. Should be more than sufficient.

ez2bgman

My Feedback: (4)

jett,

Should I make the trailing edge out of pine also? And since I am going to build my own hor. stab, I am thinking about using flying braces on the tale. What can I use to make them with? I don't wnat to go to heavy duty and add a tone of weight. I just want/need a little extra insurance. Thanks.

Gary

jettstarblue

A pine or spruce L.E. should be more than sufficient. I pine or spruce T.E will be no fun to hinge, and more than likely overkill as will the flying wires.

The failure you had is very uncommon as far as I can tell with these planes.

Tall Paul

If you add a sub-spar behind the leading edge, and at the trailing edge a few inches out from the center on each side, the stab should take any flight loads.
I'd do the outline in 1/4"x1/2" balsa, with an overlap at the leading edge.. one half goes all the way across to where it hits the other leading edge front, and trimmed to the angle.
Behind that would be another 1/4"x1/2" sub-spar tapered to the angles of both leading edges.
At the trailing edge, more 1/4"x1/2" stock, going a few inches out from each side.
Then some 1/4" sq. stock for diagonal ribs.
The elevators should be built-up, not slabs.

ez2bgman

My Feedback: (4)

Tall Paul,

Do you think you could post a diagram of what your are desricbing? I have already removed the other half of the hor. stab and getting ready to clean out the hole on the fuse. Thanks for the help.

Gary

Tall Paul

Here's two versions...
The low-wing horizontal needed braces added when I changed from a Saito 65 to a 91.
It is somewhat enhanced beyond requirements in elevator area.

CafeenMan

Build up a real airfoiled stab. On that size you can use 1/16" ribs with 1/32" sheeting and 1/8" square balsa spars (top and bottom) and it will be more than strong enough. It will probably be lighter than a slab of balsa as well. On a .40 size ship about 5/8" thick symmetrical section is good. No hardwood needed.

jimcork1

My Feedback: (4)

I have blown the stab off of at least two planes in the last 30 years. From the photo it looks like the balsa just fractured. Vertical loading would be the most likely cause. This could be up or down. This loading comes from deflection of the elevator, coupled with speed (or air loading) and the strength of the material. If you were operating at a speed within the design of the airframe I would conclude the balsa was too light for the job, or the design was flawed. The solution is to reinforce the balsa, (pine spruce etc) on the leading and trailing edge and/or adding flying wires to the tail.

Engine size is really a function of vibration and airframe speed. If you had a oversized engine but were operating in the speed range the engine should not cause the failure unless the vibration was excessive such as in out of balance prop. This vibration probably did not cause your problem because fortunately you had 1/2 of the stab remaining.

However speed is critical. Even with the correct engine if you were in a power dive you might exceed the strength of the stab. (you should read between the lines on this one as words from experience X 2)

If I were to have this plane new after seeing yours I would add flying wires to the tail and insure to not overspeed the aircraft.

Good luck and it would be interesting to hear the response from the supplier. Have a nice day... Jim

ez2bgman

My Feedback: (4)

jimcork1,

My engine is within the .40-.58 2 stroke range. I am using an O.S. 50SX on the plane. I was in level, inverted flight at a little more than half throttle when the failure occurred.

I contacted Horizon Hobby and they are sending me out a new Tail group as well as wheel pants. I want to reinforce the new H-stab prior to installing it. Where should I reinforce the new H-stab and what wood to use? I have no hesitation in removing the covering and adding the necessary reinforcements and then recovering.

Thanks in advance for the help.

Gary

ez2bgman

My Feedback: (4)

Well guys,

Got my new tail group and wheel pants in from Horizon yesterday. I went to my LHS and bought a spruce spar to reinforce the H-stab. I think I may add two new spars: one from the rearmost portion of the leading edge across the entire span and the other about an inch in front of the trailing edge along the entire span. These 2 spars should be more than enough to battle any flutter. For added safety, I may add hollow aluminum tail braces. It may seem like overkill, but I'd rather be safe than sorry. I really plan on putting this plane through the paces. I know with my style of flying. I will be putting a lot of stress on the airframe. I would much rather add a few ounces by "beefing" her up than have another failure. Besides I know my O.S. 50SX has more than enough power to do what I want. I barely flew more than half throttle on all 3 flights last time out.

Any ideas on what would the best, lightest method for adding the tail braces? And should I brace the top and bottom? Thanks

Gary

CafeenMan

If you brace top and bottom then you can use stranded fishing leader. It's not just weight but where the weight is. The farther from the center of gravity the weight is, the less responsive the airplane will be and the longer it will take it to stop moving. I wouldn't think that adding a couple spars and some bracing should add more than an ounce though.

ez2bgman

My Feedback: (4)

Cafeen Man,

Do you think that wires would be better than the hollow aluminum tubes I was planning on using? Would I set up the wires like a pull pull set up? I converted over to pull pull on my Aresti 40, so I understand how to thread the cables using the crimps. I am apprehensive of using the wires due to the tension. I don't want to warp either surface from improper tension. I know I could get an accurate measurement and trim the aluminum tube down and easily achieve the proper length/tension.

Gary

CafeenMan

With either aluminum tubes or cables, you can use a clevis on one end of each piece so that it can be adjusted. For pull-pulls I actually take a piece of threaded rod and use a micro drill bit to drill a small hole about 1/8" from the last thread. I cut it off and thread the cable through and put a clevis on it.

For tube, you just plug the end with some balsa and glue in a piece of threaded rod and put a clevis on it. Either way works.

BTW - A lot of companies make the threaded piece for pull-pulls, but I think they're over-priced and I can make a set of four in about 20 minutes.

ez2bgman

My Feedback: (4)

Well I modified the new tail group. I put a spruce spar just behind the leading edge, spanning the entire width of the h-stab. I also added tail braces that I made out of hollow aluminum tube.

Here are a few pics. Btw I put three flights on her today and she handled great.

jimcork1

My Feedback: (4)

The tail support looks good and should help the failure problem. I noticed you fly in the cresent city.. I live just across the pond on the North Shore. Happy flying.. Jim

ez2bgman

My Feedback: (4)

jimcork1,

What field in Slidell do you fly at?

I mainly fly at New Orleans East RC Club (off Almonaster) or St. Bernard Aerospace Club (in St. Bernard Parish). I occassionally go to Kelly Field in Avondale with my best friend.

Gary