RANDALL

I RECENTLY PURCHACED A HOBICO AVISTAR ARF FROM TOWER HOBBIES DURING ASSEMBLY I HAD TO PURCHACE SOME ITEMS THAT WAS SHORT CA HINGE WHEEL COLLAR ETC UPON COMPLETION MADE 4 FLIGHTS AND MY VERTICAL STAB BROKE JUST ABOVE THE FUSALODGE AND WAS IN A FLAT SPIN COMING DOWN BEFORE I KNEW IT LUCKILY I PULLED IT OUT ENOUGH TO LAND W/O DAMAGING THE NEW MOTOR OR ANY THING ELSE BUT I THINK HOBICO SHOULD MAKE IT GOOD OR TOWER HOBBIES ANY ONE HAVE ANY INFO ON HOW TO GO ABOUT THIS OR WHO TO TALK TO

THANKS RANDY

Stick Jammer

Just out of curiosity, how were the landings on flights 1, 2, and 3? Seems odd for the vertical fin to break in flight on a trainer.

RANDALL

EVERY THING WAS PERFECT UP UNTILL THE FOURTH FLIGHT NOT A NEW PILOT I OWN 7 PLANES BUT IT SEEMS VERY ODD TO ME ALSO

jucava

first call tower and the hobbico

4*60

My Feedback: (41)

And quit shouting!

RANDALL

And quit shouting


did not mean to shout wasn't aware that i was thankyou for the help
randy

doccimmer

Randall...I replied to a previous post...had the same problem as you did. I called Tower and Hobbico, asking for them to send a replacement. They gave me some line about how I'd need to send them the broken stab, they'd then make a determination as to what caused the break (don't know how'd they'd tell the difference between a structural failure due to manufacturing or an inadvertent building error) but it seemed to me I'd end up sending them the part with nothing in return. In the end I bought a new stab, and made sure I attached it more firmly this time out.

In the end, I wouldn't expect much from contacting the manufacturer...seems like more trouble than it's worth and in the meantime, you'll be grounded while they make their determination...to me, it's just easier to pay the 30 bucks and get airborne again.

doccimmer

Also,

I saw in a previous post that cutting away the excess monokote with a hobby knife scores, and thereby weakens the vert. stab. Not sure I agree with that, unless you've got a heavy hand on the blade. Given the design and instructions for assembling the stab, I'd suggest this: A good amount of the glue squeezes out of the joint when inserted, this probably doesn't provide a good bond between the fuse and stab. As I mentioned before, I did a better job of attaching this time around. First, I cleared the monokote away from the top of the elevator visible through the vertical stab slot. I bonded the bottom of the vert. stab to the elevator, used an ample amount of epoxy this time, and in addition to this, cleared away the monokote along the top of the fuselage and bonded the vert. stab to the bare balsa there too.

My guess is that the construction method creates instability in the vertical stab. Look at it this way: The stab is held in place only by the tonge of balsa that is inserted into the fuselage, and only then by whatever amount of glue DOESN'T squeeze its way out during insertion. This weak bond can cause flutter in flight, which will cause the elevator to break at the fulcrum point...the place where the stab meets the fuselage. Think of all the forces applied to the rudder in flight, then consider the explanation I've provided...which do you think is more likely candidate for causing a failure of this type...a millimeter cut on either side of the tongue, or a weak bond that could lead to flutter?

Certianly scoring the stab can cause weakness, but in this case I think the problem lies in the assembly method, particularly that it's too weak as directed. You can also add triangle stock across the top of the fuse-stab joint to add strength.

Hope this helps!

KidVermin

My Feedback: (3)

Randy:

You didn't mention if you used epoxy on the tail section or that the nut and bolt system vibrated loose, causing the vert. stab to shear at the fuselage ? The Avistar is my plane of
choice to train new pilots except for the bolting system at the rear. Most of these that crash,
it happens after several flights and I think the Thunder Tiger trainer uses this method too.

Randy

vicar

At my club all instructors have agreed not to fly any trainner that has been put together with that bolt and nut system. They are making students go back and glue all the parts. This decision was made after several of this screw-them-parts (pun intended!) had early uncontrolled landings. Sometimes they look like they are correctly and securely attached but an out of balance prop can loosen everything really fast.

lslewis

My Feedback: (2)

I followed the tech manual and applied RTV to the tail feathers. Worked for me. My Avistar has been flying for a year with many a hard landing. I epoxy the wing together and I check the entire A/C every so often. The motor mount screws loosen.

RANDALL

Randy:

You didn't mention if you used epoxy on the tail section or that the nut and bolt system vibrated loose, causing the vert. stab to shear at the fuselage ? The Avistar is my plane of
choice to train new pilots except for the bolting system at the rear. Most of these that crash,
it happens after several flights and I think the Thunder Tiger trainer uses this method too.



I GLUED THE TAIL SECTION WITH EPOXY THIS UNIT WAS AN ARF NOT RTF THE ONLY THING I CAN THINK IS THAT MAYBE I CUT TO DEEP WHEN CUTTING MONOCOTE OFF OF TAIL SECTION I WAS VERY CAREFULL BUT STRANGER THINGS HAVE HAPPENED THESE ARE REALLY GOOD FLYING PLANES AND OTHER THAN THAT I HAVE NO PROBLEM WHAT SO EVER WITH IT I THINK I WOULD PREFER TO LEARN ON A SIG LT-40 RATHER THAN THE AVISTAR BUT THAT IS JUST A PERSONAL PREFRENCE THANKS FOR THE RESPONSE RANDY

DBCherry

My Feedback: (4)

Randy,
Sorry to hear of your problem, and you may never know what caused it. You've gotten some good advice though.

When 4* said you should quit shouting, he was referring to you typing IN ALL CAPITAL LETTERS. All caps is harder to read, and is considered SHOUTING, like when trying to make a point.
Dennis-

rik756

My Feedback: (12)

It is perhaps possible that you accidentally cracked/broke it some other time and it just happened to come off in the air while flying?

Spaceclam

when you go cheaper, it sometimes becomes more expensive

randy41

If its the bolt on system i would use locktite(blue color) when you put
it back togeather.

As far as the gluing method and the triming of the monokote when gluing.
You would have to cut pretty deep and not have enough glue for it to
cause problems. Any time you have to cut away monokote to glue
it togeather make sure you have enough glue that there is excess
squezing out. This will cover and bond any cuts you have made
in the balsa do to cuting the monokote away.

Make sure you dont use OLD glue. I have seen many planes fail do to old
glue problems.

R/C Foolish

My Feedback: (6)

You guy's have to be a little more tolerant of Tower Hobbies. I have had nothing but good experiences with them and Horizon. Yeah they want the piece back, so what. I cut up a Taylorcraft once and got a whole new plane and motor. Samething with a Kyosho AT-6. They usually will replace anything if you follow their instructions.

As far as the vertical breaking, did you put a triangle stock on either side where it meets the fin or fuse?
Always a good idea to reinforce that area on any trainer.

JMO

John