Lessons learned - Flap Horn

[ray copeland]

Excited to continue trimming my Fancy Pants build from a Brodak kit, i put up the sixth flight yesterday! After a few insides and outsides i encountered some wierd behavior, big time hunting and i had to hold full up to keep level flight. I was able to run the fuel out and land, barely!!  Loaded up and went home to find the flaps not connected so i cut open the bottom side. That danged flap control horn with the plastic post was broken !!! I admit i was a little skeptical to use this in the first place, but it was included in the kit and i "assumed" it would be fine. Never again!   Another lesson in building learned the hard way, one good thing about these hard lessons is you don't tend to forget them.    Included is the before pic, i'm sure the after one won't be as pretty!

[Dennis Holler]

At least you got it down in one piece!

Thanks for posting as it backs up what I remember reading a few weeks back on here about those darn  plastic arm horns..... I'll stay away!!

[Clint Ormosen]

I've got one of those horns in my Mustang. It was installed long before I started reading this forum, but I worry about it every time I fly the plane. I know better now.

[Annette Elmore]

I crashed my Ukey 40 the second flight - loose elevator horn.

Annette

[Will Davis]

Ray,

Glad your Fancy Pants survived, where did the  control horn break?,  did it turn on the wire or did the plastic break. Good idea to stay away from the plastic control horns  

[ray copeland]

Thanks Will,  it is a clean break right on the line where the hole is that was not used. I will post a picture when i cut it open more. May be awhile, trying to get the Vector finished and trimmed for the May contest.

[Dan McEntee]

    Congrats on making the save. Here is a suggestion on how to fix it. I'm assuming you have already cut a hole in the fuse to trouble shoot the problem. Cut away all the plastic from the horn. Make a new horn arm from brass or steel, and after you drill the hole for the horn wire, cut a slot to one side so it will slide over the wire. Take two flat washers and do the same thing. Try to make things so that they are a friction fit and will stay where you put them. Wire wheel everything nice and shiny.Install the arm with one washer on each side, and stagger the slots. Use Stay Brite sikver solder and flux, and solder everything in place with a 40 watt iron, making sure everything flows well around all three pieces. If it all looks good, that should last the life of the model. Hook you flaps back up and re-trim the controls and replace the piece you cut off the bottom and you're done.
   Good luck with it,
   Dan McEntee
   Florissant, MO

[ray copeland]

Dan, that sounds like a great idea !!!  Thanks, when i get around to it i am sure that is the method i will try. A lot better than what i was originally thinking. 

[john e. holliday]

If you do this in the plane remember to have a fire extinguishr close.   Years ago one of the guys in the club did that soldering job inside a plane and started smelling smoke.  He thoght it was the solder until he saw flames.  I never would have shought a soldering iron would get that hot.  

[Jim Kraft]

Great idea Dan; I built a plane of my own design about 15 years ago and used one of those horns for the flaps. After about a 100 flights it started to get the funnies and was not solid anymore. My problem was the plastic was slipping on the wire. I cut a hole in the bottom of the plane and got the flaps to neutral, and drilled a small hole (1/16") in the plastic. Then I used a small sheet metal screw with the point ground off in the hole as a set screw. Then the whole thing was soaked with CA. It has worked OK for about 50 flights, but every time I go to fly it I worry it is going to slip again. Maybe I will cut it open and do your fix.

[Jerry Leuty]

  I lost a plane just yesterday due to a flap horn failure. I built this particular plane some 7 years ago and had lots of flight on it. It was sort of windy and the loops tend to get fast and tight on windy days. One the second outside loop it went in at about a 30 degree angle. I just assumed that the handle was a little out of adjustment since I tend to use the same handle and lines for several different planes. With making everything equal on the lead outs you can use the same lines without too much adjustments between planes. I didn't think too much of the crash until I was washing the broken plane for disassembly and I found the plastic control horn snapped right off. Since it was an old plane and I have some dozen or so ready to fly I just scrapped it out. Funny how much extra stuff that you suddenly have after a plane scrap. I am thinking that it is time to make some all steel control horns. Is there anybody out there that offers all metal horns for sale?