Hello gents...long story short:

we had a wing failure and lost one wing in flight on a new 5times flown



VOTEC 50CC from www.2krc.com and www.lindinger.at

too bad no one took any video ..funny to watch but not to the owner see his 3000$ going down on the deck big time surviving only 4 servos

the failure took place while a big loop when the wing broke away from the wing tube

so since thank God no one got hurt we checked the wings and here we go:


in photo 1: we see the balsa wood that connects the tube with the wing skin . wood grains are sideways

in photo 2 : we see the thickness of the balsa estimate 2mm

in photo 3: we opened up the wing that didnt fail and we see the connection webs between the ribs after the tube.
balsa 2mm again with grain sideways and all been broken in the spot on the photo (probably also from engines vibrations)


now the 3000$ question:
IS MANUFACTURES FAULT THE WING FAILURE BECAUSE OF THE WRONG GRAIN DIRECTION??

the manufacturer came back with an email saying there is nothing wrong with there design

my experience say: that web wood grains should be VERTICAL cause they provide way better structural strength

here is a kit manual...not even 50cc ! please notice photo DD19

http://manuals.hobbico.com/gpm/gpma0175-manual.pdf


Thank you all for your time voting and for also leaving a comment in this threat

We work hard for our money and manufactures of giant planes should not do this mistakes risking our money

Best regards
George

web wood grains should be <u>VERTICAL </u>

This is just <u>UNACCEPTABLE</u></p>

Yes, they must be vertical... they are close to useless if horizontal. This is quite a common mistake done in many cheap ARF planes, including the Falcon 120.


Enrique

They must be vertical. No strength horizontal. My vote is vertical.

Vertical is really the wrong term, the grain of the shear webing should run "Perpendicular" to the spar or wing tube

Thank you for voting and sorry for my poor English.

''Perpendicular'' is added to the options!

Scale only 4 me,

Agree with you. Webbing must be perpendicular with main spar to make a solid I-beam type structure. Some ARF's make use of CNC laser cutters to cut ply main spars. Obviously the grain would be horisontal due to the lenght. But these spars should be capped with grain running perpendicular as well...

just my 2c

Morne

Yep perpendicular to the spars is a must. That structure needs shear webs. Normally if I scratch build I would have 2 1/4 (or larger depending on scale) inch spruce spars running the length of the wing with two large 1/4 inch ply braces at the heart of the structure. Something like this is what is needed IMO.

I can see why they did it the way they did. That looks like a sheet of balsa laser cut to make that support, but it is the wrong direction. To do it right, the manufacture would have to make much smaller parts and they cost time and money for them. I don't think webbing is the place to try and save weight by cutting them out like that either. Each section should have it's own piece of balsa and only run vertical, not span ways. The best way is to put it between the spars making an I beam out of it. At least put webs between the ribs with no holes in them and with the grain running vertical. I would have changed that in the build. I know it hurts, but the builder is partly at fault for building it that way. Unless he is new, he should have known better. If he wasn't sure, he could have ask here and found out that it is a bad design. Who ever designed that wing either didn't know or didn't care. Looks to me like they were just trying to save money. In the long run, they could have put a sheet of balsa in the kit and let you cut them out yourself. That would save money too and wouldn't come back to bit them.That is a BIG no no to build them like that. Cutting holes in them takes most of the strength out of them just doing that, but running the grain length ways is way wrong and the manufacture should know better.

Ed

yes, "perpendicular" is the way to go if you want a wing that lasts and can take the type of g forces a 50cc plane generates. if you want cheap, easy, and to pay some chinese factory to build your arfs then there must be some sort of quality control inspection.
to me this is unacceptable!

Ridiculous. They ought to be sued for knowingly making unsafe planes. If they did this unknowingly, they should quit making planes because they obviously don't have the knowledge to build a safe plane. Call your lawyer.

Nuff said.

Except what make and model it is????

I'd sure hate to find out the hard way like George did

it should be vertical . no other word can be said.

In full scale wooden construction it is common practice to use plywood for shear webs. It has been shown by experiments that diagonal plywood [face grain at 45° angle to the edge of the panel] is approximately five times stiffer in shear than square laid plywood and somewhat stronger.

If "single grain orientation" wood such as sheet balsa is used, the grain should be running perpendicular to the beam direction.

sounds like it may be a good idea to use that 1/32 ply or something like that for future projects

grain direction is of upmost importance, In models as in full scale aircraft.
This is a major Blunder and I'd request a free replacement or see you in Court.

Well that looks like shoddy chinese crappy building.  I hope you can get your money back on this one but I doubt it. this is the reason I will not buy a ARF if I can help it, you just do not know if it is built right. I love building the topflight kits, from a box of wood at least I know if it fails, it is my fault

Vertical/Perpendicular

Bob<br type="_moz"/>

The grain must b vertical or perpendicular to the spar !! It also must be a tight fit between the ribs !! Most homebuilts use an I beam type instead of a full box to save weight. The sheer web is only their to stop the bending moments of the spar. The bottom spar is in tention and the top spar is in compression, while positive G loads are in effect. just the oppisite in negative gs
the tip only transfers the loads from the top spar to the bottom spar, and vise versa !!

45 degrees!!

Skip, 45 degrees is ONLY to be used with ply/laminates.  Otherwise, it's PERPENDICULAR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  Horizontal is the absolute weakest way for that thing to be placed.  In fact, it's MEANT to fail when placed parallel with the spar.<div>
</div><div>Some people just shouldn't be trusted with wood and glue.</div>

These are mass produced Chinese airplanes there are many companies who make such type of airplanes... i had repaired a wing of a 3D model few years back & i saw the wing spar was so soft........ that you can break it very easily...... there are many other problems... if you notice with these airplanes this is just a lack of R&D department who test & inspect these manufactured airplanes..

I design & build my own airplanes.

I voted for vertical in fact when you build up a kit the instructions will also sayshear web should be installed vertically but as already been said many arfs dont install the
shear webs properely.

If a beam is loaded such that it is hogging (supported at each end with a downward load in the center) then the upper flange will resist compression and the lower flange will resist tension. The web which is what we are discussing here will resist shear loads. It can be shown that there are both horizontal and vertical shear loads, to resist horizontal shear you would need the grain to be running vertically and to resist vertical shear you would need the grain to run horizontally. Most engineers rarely design in wood so it is never an issue for them but based on the preceeding I would say that ply would be the best solution.