oldbassard

I can't count the RC airplanes I have heard people say the tail structure is weak. I am getting ready to build a 4 star 120 and put a OS GT 22 gasoline engine on it.

Someone told me the tail structure is weak, Is there a better wood I should replace the balsa with, Should I just glue in extra bracing, or maybe webbing. Maybe get my welder out? LOL kidding about the welder


Any suggestion will be appreciated


Bassard

wcmorrison

My Feedback: (2)

I glue extra wood inside the structure.  For instance, if I install servos in the fuselage close to the tail, I use popcycle sticks insde cross wise so the servo screws have some substantial to bite into.  The installation also sort of strengthens the area.  I have also added 1/4 angle stock where I can.  Let's face it, there is a lot of load, sideways, up and down inside the empanage area.  I have even flibre glassed the outside.  And I have added angle stock between the fuselage and where the vertical tail fits into the fuselage, that stiffens up the rudder.  Does it add weight, yes, does it make it stronger yes.  Your choice, a bit of weight for longevity.

wcmorrison

My Feedback: (2)

I glue extra wood inside the structure.  For instance, if I install servos in the fuselage close to the tail, I use popcycle sticks insde cross wise so the servo screws have somethiung substantial to bite into.  The installation also sort of strengthens the area.  I have also added 1/4 angle stock where I can.  Let's face it, there is a lot of load, sideways, up and down inside the empanage area.  I have even flibre glassed the outside of the fuselage in that area.  And I have added angle stock between the fuselage and where the vertical tail fits into the fuselage, that stiffens up the rudder.  Does it add weight, yes, does it make it stronger yes.  Your choice, a bit of weight for longevity.

wcmorrison

My Feedback: (2)

I glue extra wood inside the structure.  For instance, if I install servos in the fuselage close to the tail, I use popcycle sticks insde cross wise so the servo screws have somethiung substantial to bite into.  The installation also sort of strengthens the area.  I have also added 1/4 angle stock where I can.  Let's face it, there is a lot of load, sideways, up and down inside the empanage area.  I have even flibre glassed the outside of the fuselage in that area.  And I have added angle stock between the fuselage and where the vertical tail fits into the fuselage, that stiffens up the rudder.  Does it add weight, yes, does it make it stronger yes.  Your choice, a bit of weight for longevity.

speedracerntrixie

My Feedback: (29)

flying wires add a ton of strength without a buch of weight. Pictured is a classic example

eddieC

My Feedback: (2)

Quote:

flying wires add a ton of strength without a buch of weight. Pictured is a classic example

ARUP

PA-12 conversion from a SIG J-3 Cub kit. See the extra balsa to support the dowels? The dowels are the hard points to mount the wires.

N1EDM

My Feedback: (2)

When I built my 4*40, I don't recall the tail being a weak area. The area that I would be concerned about would be just behind the cockpit where the aft cockpit former meets the aft fuselage framing. On a hard landing, this would be the area that would 'give' first. A few gussets would help to reinforce this.

Just my $.02

Bob

FlyingPilgrim

My Feedback: (26)

I don't think there is any problem with the 4* tail as designed. I have one I built with a Saito 1.20 on it, and built it stock except for enlarging the rudder for better knife-edge flight. They have alot of wing, and once I was trying to taxi a little too fast. It went airborn and my first reaction was to cut the throttle (naturally, right?). It dropped and hit the spinner and wing-tip, flipped and then the tail section hit hard. The tail covering on the fuse was split at the front of the verticle fin straight down the sides of the fuse a couple inches on both sides. When I removed the covering to inspect the integrity of the fuse, I discovered that the small piece of plywood in front of the tail feathers had split all the way where the layers of ply were joined. All I had to do was wick some thin CA into the piece of ply to repair it and re-cover.

BillS

For extra strength I like to face the Lite ply with 1/64" ply which stops most of the Lite ply cracking.

Bill

Gray Beard

My Feedback: (-1)

As Bill I keep a big sheet of 1/64 ply and use it as a doubler in stress areas. I also add hard points then add flying wires if I think it will be needed. I had the YS 120 in the big 4* and didn't add the wires but I did install doublers and hard points during the build.

RICKSTUBBZ

Here is a direct link to post 391 I made in the Sig Smith Miniplane thread back in 2009 where I added wire braces top and bottom of the stab.
[link=http://www.rcuniverse.com/forum/fb.asp?m=9216307]POST 391[/link]


Picture below is one of eleven in that post to show how it was done.

FlyerInOKC

My Feedback: (6)

In my opinion most kits with so call weak tails fly just fine if built as design and flown as designed. The "weak" tail is only weak when the pilot flys it a little too hard or lands a little too hard. I have an old LT-40 which if you look at the design could be considered very weak in the way the vertical stabilizer is mounted. I had no problems until the day I parked it in a 100 ft tree canopy. My Eagle scout son went up to retrieve it and the Vertical stab was all he could reach. He pulled the vertical stab off getting the airplane out of the tree. I added triangle stock on each side when I reattached it but I paid a premium in doing so in the form of added ballast in the nose to restore it to the correct balance. I have seen a number of airplanes that ended of way too tail heavy by adding strength and weight to the tail. In my opinion added material for strength in the tail puts more stress on forward sections of the fuselage in a hard landing causing fractures behind the cabin in some cases. To summarize adding tail strength to a proven design is a two edge sword. I'll shut up now I can here the snoring from here!