How to Resolder or Glue a Control Horn

[Brendan Eberenz]

I have a control horn (see picture) that came with some wings I bought for a SV-11. The control horn is designed for a full body plane, but we are making our SV-11 a profile (please don't try to talk us out of making it a profile). That means, I need to move the metal tab with the holes about a half inch over. Tonight I took my propane torch (for copper plumbing), knocked out the solder joint, and was able to get the tab to freely move. When I moved the tab and tried to replace the solder joint with solder I use for plumbing, it never took.

It feels like I should Dremel a small groove in the wire and epoxy the tab in place. Is there a problem with this approach? For those that are soldering gurus, what am I doing wrong? I assume it's a matter of using the wrong kind of solder.

[Colin McRae]

FYI

Brodak sells a few new horns that already have the horn offset from center on the wire.

I have also used my Dremel cutting wheel to 'nick up and roughen' the wire surfaces and used JB Weld epoxy to make the bond.

[Air Ministry .]

SHESH .

Wattage , if its a IRON . and theres 40 / 60 Hard solder & 50/50 Soft Solder . if you aint got 80 Watt youre not in the game ,

BUT THAT is a SILVER SOLDER or a BRAZED joint . ' Normal ' solder on anything over a 1/2 a , and your DOOMED . Unless its a Figure 8 hole with two , main & a 3/4 od, bound and SOLDERED .
as a tourque thingo wotsit .

Ya coulda just rebent one enda the wire furver inn . Like an inch . Man . 

[Dan McEntee]

    Hi Brendan;
      First off, you need to get it SHINY CLEAN!! All that black stuff needs to come off. Measure the location and move the horn so that you can put it back where you want it, and clean everything with wire brush, sand paper, steel wool, what ever it takes. You will need your torch and some silver solder and appropriate flux. Did I mention that it needs to be CLEAN!! Don't rely on the flux to do it. Search out some threads here on soldering control horns and read up on the process. Some guys like to cut a little ring of solder that goes 1 wrap around the joiner wire, and that is a good place to start for your first attempt at this. If you can stand it up so that the horn is horizontal and the main wire is vertical, that will help you also. Apply some flux to the joint sparingly. You don't need tons of it. Light your torch and start heating the joint and kind of keep the torch moving a little bit. You will se that little blue cone that comes out of the torch nozzle, put the point of that cone right on the joint. Watch carefully and closely and as soon as you see the little ring of solder melt and flow around the joint, slowly take the torch away. Let it cool for a few minutes, then inspect both sides. If there was enough clearance and enough solder material, it may look the same on the other side. If not you will need to add a bit more in the same manor, but clean the whole joint, both sides, again thoroughly first with the wire brush. Dirt, scale and carbon really can mess up a good solder joint, so you gotta get it clean again. Some guys will double upon the joint with a tight fitting washer to on each side to give the solder more to hold on to, and you might want to keep that in mind. When finished clean it all off again like you are gonna solder it again and see how it looks. The solder should be smooth and flowing all around the joint. Nothing lumpy or bumpy. If you have problems, clean it all off and try again. It does take practice to get proficient at this, and practicing with scrap pieces is encouraged.
  Type at you later,
  Dan McEntee

[Dan Berry]

 Buy a new horn

[Robert Whitley]

Hi Brendan,
Another option is to eliminate the horn  entirely and just use it as a joiner for the flaps, or make a new hornless joiner from music wire.
Then use a nylon control horn attached to the flap.
That works just fine on a profile.

[Brendan Eberenz]

Thanks for all the good info. I did walk into Brodaks a few weeks ago and it was going to be about $25 - $30 for an offset horn. It just didn't make sense to pay that when there are other work arounds and I  already have the correctly sized wire. While I want to go with epoxy, my gut has me worried it will give way at some point and then our most expensive build yet is a bag of balsa. Thanks for suggesting the flap horn Robert. That's a strong contender if I don't think I can pull off the soldering.

[Brent Williams]

Don't solder the horn.  Braze it.
If you can't braze it, then add a pin to the horn, wire wrap and solder that assembly.

[Motorman]

Don't use glue, it will fail. Regular solder isn't trustworthy and silver solder will cost more than a new assembly. Also, you can clean the rod and clean the horn but you have to also clean the hole where the rod goes through. I'm right down here in NJ if you want to mail it to me with a drawing, I can silver solder it for you as I make all my own control systems.

MM

[Ken Culbertson]

If it feel like we are piling on it is because we are!  Don't even think about soldering or glueing a flap horn.  Braze it or silver solder.  It will fail.  I have used several regular flap horns on profiles by simply offsetting them.  Nothing in the rules that says they have to be plugged into the flaps equal distances.

Ken

[Dave Hull]

I went thru something a bit similar recently. An old SV-11 ARC kit. The horns were only partially brazed (about half the joint was filled) and I didn't like the looks of things.

I cleaned the flap horn thoroughly and used a propane torch and silver brazing material--not silver solder! I have done tests on horns with various different solders, including silver solder. Nowhere close to good enough except for a 1/2A, and I wouldn't do it there either. By tests, I mean I made the horn up and then used a force gage to measure the load when the joint slowly began to creep. I don't recall if I posted those tests before or not.

On the SV-11 flap horn I was able to rebraze it. You must use the appropriate flux for silver brazing or you will contaminate the joint, making things worse, not better. The flux for copper pipe will not work.

On the SV-11 elevator horn I had no luck and junked it. It had been plated (likely nickel) and just cleaning it did not allow adhesion. It wasn't worth it to me to try to remove the plating and risk etching or damaging the wire. I just made a new one. I believe I showed pictures of that brazing setup in a recent post.

https://stunthanger.com/smf/open-forum/brodak-prices/msg667365/#msg667365

Forget about epoxy. That would take a different design of the arm to increase the bond area. Truth be told, good bonding takes more skill than this type of brazing. With brazing, errors in cleaning show up by lack of wet-out. In bonding, you hide all your sins and it looks like it will work great--until it doesn't.

The flap joiner-plus-separate-horn idea should work. If you chose to use plastic horns, there is the possibility of getting the left and right pair and mounting them back to back. I've done this on a smaller plane and been happy with it.

Dave

[Leonard Bourel]

I believe that making a proper horn that will not fail or cause lack of sleep wondering if it will fail is of all importance Don't experiment on this Get a good horn or use Robert Whittly's idea

[jerry v]

Brendan,
If the wing, flaps, hinges, belcrank, flaps pushrod was already established for full size fuselage - then simple solution for profile fuselage was to move the new fuselage centerline 1/2 inch or so toward the outer wing tip. You will have longer inner wing and some asymmetry in the flaps position next to fuselage. You will have to make a plug piece anyway to cover the flap gap difference from full fuselage to profile. If you will make the offset horn as your original idea, then you will need to reverse the belcrank 180 degrees to line up the flap pushrod with the new flap horn position. That also requires to switch the leadout cables inside the wing front/rear. After all this frustration the solution will be to find another SV-11 flap horn with joiner wire.

Jerry

[Doug Moon]

I am not going to try to talk you out of it but I am curious why you would make it a profile?

You stated earlier you dont want your most expensive built to end up crashed but dont want to spend the $25 for the horn. It's a crossroads for sure. But purchasing a new horn is your best bet. If that is one of those chinese ones that comes with the ARC kits good luck ever getting anything to stick to it.  I dont know what they make that stuff out of but its not normal, cheap, and brittle.

Any horn you buy for a full sized stunt ship is brazed. I have made a few. Plumbing torch will not work.

Best to buy a blank and make the bends yourself. Then you can set the upright where you want it by making the bends at a certain spot.

What size horn do you need and what offset are you looking for?

Doug

[Howard Rush]

I'm wondering if the airplane will still be controllable when the joint fails.  Elevator control wouldn't change, would it? 

[Howard Rush]

Have you considered using kratom for the joint?

[Brendan Eberenz]

Have you considered using kratom for the joint?

Howard, that is a hilarious response.  I like how that question got slid in the other night on the video hangout and no one blinked.

[Brendan Eberenz]

I am not going to try to talk you out of it but I am curious why you would make it a profile?

We are going with a profile because my son (age 13) is putting this together as his NATs plane to be BOM qualified. We live near Brodaks and lucked out when the shop told us they had a pair of ARC wings they would sell us. This helped us avoid buying an entire kit where we would have had a leftover fuselage. since to be BOM eligible my son has to make his own fuselage (or wings). The only plane he constructed from scratch before was a Twister. A full body is beyond are building level at this time, so we decided to run with a profile fuselage. We also like that the model will be multi-event eligible as PAMPA and Profile. This gives him more opportunity for contest entry and practice.

[Brendan Eberenz]

I appreciate the one guy in NJ that offered to redo the joint for me. However, I have a lot of people sharing that redone joints go bad all the time. I basically have the  right size joiner wire once I take the tab off, so getting a nylon horn for the flap makes the most sense. One responder suggested buying two horns that can go back to back on the flap. Is this a good approach? We are relatively novice flyers/builders, so I don't know if one horn is good enough, or the double horn is a better idea.

[Robert Whitley]

I’ll pm you pics of how I did it on my Vector 40 profile which used a salvaged ARF wing.
I used a large heavy duty RC horn and RC car ball ends.
The controls are very smooth.
If you’re on hangout tomorrow night I’ll show you live what works for me.

[Colin McRae]

One issue some modelers don't like with a flap-mounted (or split elevator mounted control horn) is differential flex between the 2 adjacent control surfaces due to the flex in the joiner wire. But the issue is minimized with adequate diameter and stiff music wire joiner. A horn directly mounted to the center section of the joiner wire prevents this issue.

I put together a Brodak P40 ARF a couple of years ago and used the kit supplied joiner wire which was small diameter and not stiff music wire. But I did not know any better at the time being somewhat of a rookie builder. Lessons learned for sure. On my ARF model, if I hold the inside flap rigid, I can easily flex the outer flap like 1" up and down. Same thing with the elevator. Not good!! In flight, the model will roll if I give it hard control input. If I had it to do all over again, I would have upsized the joiner wire to 5/32" or maybe even 1/8" music wire. One of these days I'm going to cut into the model and fix it.

Live and learn.

[Brent Williams]

I suppose it goes without asking, but did you also move the bellcrank mounting location in the wing to accommodate for the profile fuselage?

Good performing profile airplanes aren't always less effort to build. 
A simple box style fuselage can be made for a full body that is in many ways easier to construct and much stiffer overall. 
I have attached a picture of the ultimate expression of a box fuselage.

[Dan McEntee]

I appreciate the one guy in NJ that offered to redo the joint for me. However, I have a lot of people sharing that redone joints go bad all the time. I basically have the  right size joiner wire once I take the tab off, so getting a nylon horn for the flap makes the most sense. One responder suggested buying two horns that can go back to back on the flap. Is this a good approach? We are relatively novice flyers/builders, so I don't know if one horn is good enough, or the double horn is a better idea.

  The only reason for a re soldered/brazed joint failing would be if you did not clean thoroughly . Get it cleaned up nice and shiny and it's justy like the first time. If nothing else it's good practice.
   Type at you later,
   Dan McEntee

[Dave Hull]

Here's a picture of two plastic horns paired up and mounted to the flap. The flap has a plywood pad both top and bottom to spread out the loads and help prevent crushing. This is on a Twister-based plane. Turns out I have two planes done this way. I'm not sure if the horns will be as long as you might like for an SV-11. But, it is an idea you can consider.

What Dan may not be realizing in his comment about proper cleaning ensuring successful rebrazing is that the SV-11 ARF horns may have been nickel-plated; perhaps even electroless nickel-plated. The ones I got in the kit had been plated after brazing to minimize corrosion. They were "fuzzy" indicating that there was likely still swarf on the wire when they were plated. Solvent and abrasive cleaning was insufficient to allow wetout on one of the two horns in my kit, so it went into the junk bin. Not a lot of consistency in the kit--I rebrazed the other horn without issue.

[Air Ministry .]

To save to much blather ;


another ole directly above existing , and a short length of wire . bound & solderd . Duzall acid flux , pre tined .

Id grab a new length of wire for your horn , cut adjacent . Throw on new wire THEN do the second bend .
A good fit I chamfer a end of the short one . Wire in vice , horn vertical . Fit & tap short un down in . Check .

Some nput a flat on BOTH . But if its Tight ( centers close ) a FLAT on the short ones enough , to get it in .
IF you dress the end shafp edge , so itll slide in . Pre Tin ( solder ) the fuse wire BEFORE binding it ,
cleaner job by far . ( String the wire out on a old board & mop it with flux. old brush . solder . remop -
THEN it'll flow out THIN all over . And likewise the wire Horn . ) If yaraint got silversolder .

If you have , it'll save all that bother . But use NEW WIRE .

[Doug Moon]

How wide do you need the horn to be?
how far to you want the offset? Inside or outside?

I may have an old horn around I can just send you.

[Dan McEntee]

What Dan may not be realizing in his comment about proper cleaning ensuring successful rebrazing is that the SV-11 ARF horns may have been nickel-plated; perhaps even electroless nickel-plated. The ones I got in the kit had been plated after brazing to minimize corrosion. They were "fuzzy" indicating that there was likely still swarf on the wire when they were plated. Solvent and abrasive cleaning was insufficient to allow wetout on one of the two horns in my kit, so it went into the junk bin. Not a lot of consistency in the kit--I rebrazed the other horn without issue.

       If these are plated after brazing at the factory ( which I image is done as cheaply as possible with the cheapest materials as possible, considering the country of origin ) that all probably burned and flaked off with the torch when be broke the tab loose, and and could also be removed with a vigorous cleaning and work over with a wire wheel and some sandpaper. I can't imagine a Chinese ARF company going through that expense. Maybe a quick coat of paint, but even if it was plated I can't see not being able to work past that and eliminating it.

  Type at you later,
   Dan McEntee