Elevator joiner horn, bearings critical?

[Matt Brown]

I’m assembling another glow SV11 arf. I made the mistake of epoxying the horn too deep into the elevators. I made up some brass support bearings but because the horn is rather deep in the elevators, the bearings are not on same centerline as the hinges. As I move the surfaces, I’m getting a bit of binding. If I remove the brass bearings the surfaces are extremely free, zero bind like I want. Considering it’s an arf and only a back up, can I get away without them? I’m sure many have been built without them as they aren’t included but only shown in the manual. I was thinking I could sink the hinges deeper into the elevators to better match the bearing centers but probably won’t be perfect. I’m also considering using a soldering iron to heat the wire to soften the epoxy enough to pull it out into the correct position.

What would you do?
Thanks, Matt

[Brett Buck]

I’m also considering using a soldering iron to heat the wire to soften the epoxy enough to pull it out into the correct position.

What would you do?

  I would pull/cut it out until it lines up.

   Brett

[EddyR]

Just sand back the edge of the elevator   until it is inline with the horn

[Jim Svitko]

I can confirm what Bob Hunt said is true.  I left the center bearings out of the elevator horn once, about 20 years ago.  Within ten flights or so, the innermost hinge on each side loosened and total failure was imminent.

It pays to do it right and then you never have to worry about it.

[Matt Brown]

Hi Matt:

Yeah, they are critical if you intend to fly more than a handful of flights. If you do not use them you will be putting inordinate strain on the first hinge, and it will eventually give.

As Brett suggested, cut the horn out of the elevators and redo it. Small price to pay for longevity of your plane.

Attached are some photos of the method I use to anchor the horn bearings to the trailing edge of the wing and stab.

Later - Bob Hunt

I love what you did there Bob! I wasn’t liking relying on glue joint on brass even though I dinged it up with a punch. I’ll make up a few of those for this build in the morning.
I did end up using my big soldering iron and melting out the horns the Re gluing them in the correct location. Everything thing is much freer now. Both flaps and elevators flop under their own weight easily to the throw limits. 
As I was working on jigging up something to align everything I found my setup from my last SV11 assembly!

Thanks to all again!
Matt

[ericrule]

Bob Hunt:
Sir I am always amazed at the "neat" ideas you come up with.

First your dad and now you! I would love to get a short look inside your mind to see how in the world you keep coming up with this stuff!

[Brett Buck]

I love what you did there Bob! I wasn’t liking relying on glue joint on brass even though I dinged it up with a punch. I’ll make up a few of those for this build in the morning.

     You don't want to rely on gluing to brass, although it's probably OK with epoxy or (interestingly) model cement as long as you rough it up first. But generally you want to at least fiberglass over the tube to hold it.

   Bobby's method is preferred, because you also wind up with a doubler to reinforce the hole through the side of the fuselage, which is a common place for the fuse side to crack. You can do the same thing with a profile, with the doublers on the outside, and feathered out to a knife edge so it blends in.

     Brett

[George Grossardt]

Hi Matt:

Yeah, they are critical if you intend to fly more than a handful of flights. If you do not use them you will be putting inordinate strain on the first hinge, and it will eventually give.

As Brett suggested, cut the horn out of the elevators and redo it. Small price to pay for longevity of your plane.

Attached are some photos of the method I use to anchor the horn bearings to the trailing edge of the wing and stab.

Later - Bob Hunt

This is exactly the type of detail that makes this site worthwhile.  It may seem like a little thing, but what Bob has done providing a wide range of details to models is a wonderful gift.  And it’s not just Bob - so many of you provide us low level modelers tips and suggestions that make our work more enjoyable - Thank you!

George

[FLOYD CARTER]

Many commercial control horns are supplied with brass tubing installed for bearing.  I consider bearings important because the horn part converts linear motion into circular motion (torque).  In the conversion, a force fore and aft is also generated, causing the horizontal part of the wire to move.  The brass tubing is meant to be fastened to the structure to prevent motion fore and aft.  A retrofit of tubing is better than none.;  This can be done by cutting away half of the tubing so it will slide over the wire.  Then, the tubing can be fastened to the structure.. 

[Brett Buck]

If that close fitting tubing isn't perfectly aligned it will make your controls stiff.

    Exactly, which is why you do something positive to hold it in the right place.
   
     Brett

[Matt Brown]

I did the elevator hinges the other night with bearings and came out beautifully. Did the flaps this morning. Just checked them and they came out great too. The way I initially installed the horns wasn’t going to work with the bearings. I’m going to cut a set of the support pieces like what Bob showed and I’ll install them after the wing and tail are epoxied into the fuse.
Learning slowly. This is my third SV11 arf, second glow powered. As soon as I finish this one, I have another electric SV11 and an electric Vector arf. I wish now I’d have gotten the glow Vector.

Thanks,
Matt

[Brett Buck]

I’m going to cut a set of the support pieces like what Bob showed and I’ll install them after the wing and tail are epoxied into the fuse.
Learning slowly.

      You're getting there, keep up the good work.

     The general rule that applies - you will never regret doing it better. You will frequently regret doing it half-assed.

     Brett

[Jim Svitko]

Many of us have worked in industries and on programs with tight schedules and critical deadlines.  I heard this years ago:

"Why is it that we never have the time to do it properly the first time, but we always find the time to do it over again?"

[Brett Buck]

Many of us have worked in industries and on programs with tight schedules and critical deadlines.  I heard this years ago:

"Why is it that we never have the time to do it properly the first time, but we always find the time to do it over again?"

  Exactly.

     Brett

[Dan McEntee]

      You're getting there, keep up the good work.

     The general rule that applies - you will never regret doing it better. You will frequently regret doing it half-assed.

     Brett

     In my personal experience, I have ALWYAS regretted doing things half assed!

   Type at you later,
  Dan McEntee

[Matt Brown]

     In my personal experience, I have ALWYAS regretted doing things half assed!

   Type at you later,
  Dan McEntee

But the first few times you do it, you don’t know it’s half assed till you get it done! Gotta learn from those mistakes. I just don’t have all that much time left to make that many mistakes. Not like I’m starting this competition stuff in my 30’s.

Matt

[kevin king]

Doing things better vs. half assed is good advice. I remember a supervisor at Boeing asking me when I'd be finished the part I was working on, So I asked him, Do you want it done fast or do you want it done well? He paused and walked away.

[FLOYD CARTER]

[, So I asked him, Do you want it done fast or do you want it done well? He paused and walked away.
[/quote]

That smart-alec answer seldom gets a favorable response,  Better have your resume handy.

[Avaiojet]

Matt,

If you used only Epoxy, just heat that area up carefully.

The epoxy will soften and allow for you to pull the wire out to where you would like it to be.

The epoxy will harden again.

Charles