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General control line discussion => Open Forum => Topic started by: Mike Quinn on May 28, 2025, 02:54:10 PM
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First time I’m using ball links on the flap horn. I can’t get them on the same side of the horn as they jam each other up. Is it ok to have them on opposite sides with standoffs. The holes are tapped and i’ll use JB weld on the nuts to seal the deal. They do clear each other fine mounted on opposite sides.
This must be a common thing using balls links right ?
Common sense tells me its fine but thought i’d ask in case of any gotchas.
Cheers
Mike
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That looks like a VERY robust vertical member on that horn. There should be no issues with that offset.
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First time I’m using ball links on the flap horn. I can’t get them on the same side of the horn as they jam each other up. Is it ok to have them on opposite sides with standoffs. The holes are tapped and i’ll use JB weld on the nuts to seal the deal. They do clear each other fine mounted on opposite sides.
This must be a common thing using balls links right ?
Common sense tells me its fine but thought i’d ask in case of any gotchas.
Cheers
Mike
Hi Mike....
I have done it this way on 3 Vectors and 2 SV11 and it works great with no trouble.
I don't use plain nuts....I use the stop nuts that come with the links.
The screws have to be shortened slightly to be almost flush with the nuts but everything fits just fine.
You might have to grind a flat on the standoffs to clear the nut.
I'm using 4-40 hardware and links.
One thing....the rod to the bellcrank should be on the outermost hole...so just swap the positions and you'll be good.
JB weld is good but I've never used it on this application where there was no access after the airplane was completed.
I use a stop nut on the elevator horn too but no standoff...and...use the middle hole here for the pushrod link.
I don't thread any of the horn holes....I drill them to right size for the bolt, then when the nut is tight...there is no slop.
This will....as you have likely found out....will make it a LOT easier to assemble.
Select the links for minimum slop....I just went through this last night to find the tightest links.
Also...I use an old ARF pushrod with links to install in the airplane, set the flap/elevator relationship, then you use the old pushrod as a tool to get the correct pushrod length, then make up a new one with carbon tube and new links.
Cut the head off 2 4-40 bolts then Get a board, drive in a 4-40 bolt partway, then slip one end of the old pushrod over the 4-40 bolt, then drive in another 4-40 through the other link so you can make up the new pushrod length using this tool.
I usually hit the new pushrod length within 1 turn of the link.
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Dubro also makes a 2-56 / 4-40 ball link that is smaller. 2-56 size ball and 4-40 size for the pushrod.
Might this work as the link itself is a bit smaller?
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your title reminded me of an incident that happened yesterday. I was in a doctor’s office. On the counter was a jar labeled “balls”. (It may have said “cotton balls”. Something was in the foreground covering the left side of the label). I thought that since the knee replacements worked, I might as well give it a whirl, but then I was distracted by drawing a clock.
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Common sense tells me its fine but thought i’d ask in case of any gotchas.
Cheers
Mike
Do it all the time. Never had an issue.
Ken
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Hello
Thanks for the feedback chaps. Good to know i’m not making a total ‘Horlicks’ of it.
The horn is 2mm steel but I think I’ll use 1.5mm next time. It certainly feels beefy 😂!
Mike
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Medical advancements are incredible Howard.
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Medical advancements are incredible Howard.
I'm just going to leave this here....https://neuticles.com/ (https://neuticles.com/)
Steve
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First time I’m using ball links on the flap horn. I can’t get them on the same side of the horn as they jam each other up. Is it ok to have them on opposite sides with standoffs. The holes are tapped and i’ll use JB weld on the nuts to seal the deal. They do clear each other fine mounted on opposite sides.
This must be a common thing using balls links right ?
Common sense tells me its fine but thought i’d ask in case of any gotchas.
Cheers
Mike
If I'm seeing straight, your BC > Flap pushrod isn't going to the top hole on the flap horn. It should, because the load of the flaps is much more than elevators. More leverage, so more control at low line tension. Remember that line tension is what really powers your control inputs, not your wrist wiggles. D>K Steve
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Hi Steve
I see what you mean. How come so many plans show it one way or the other. Doesn’t seem to be a hard and fast rule per se, although I’m not arguing with what you’re saying.
Chers
Mike
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To expand on what Steve said, I think one should maximize the ratio of leadout travel to flap deflection. That maximizes leverage over flap hinge moment. A tall flap input control horn would then minimize the effect of control linkage slop.
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Hi Steve
I see what you mean. How come so many plans show it one way or the other. Doesn’t seem to be a hard and fast rule per se, although I’m not arguing with what you’re saying.
Chers
Mike
As to why plans show it ***wrong*** is because 1) a lot has been learned and understood about CL Stunt since the 1950's and 2) a lot of times those drawings were done by somebody who was trying their best to draw and ink a drawing fit for publication. Which is based on some pencil sketches that the original designer had used to build 1 >? number of models from. Could be a lot of drafting errors in any of them...like the CG location on a Flite Streak plan. H^^ Steve
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For what it is worth, it is all about leverage. We all have our own ways of getting there. The flaps are key, and you have to have enough force to deflect them to the maximum required plus a little margin. If you have a tall flap horn, you need either a lot of bellcrank movement or a long drive arm on the bellcrank. Couple that with a "small" bellcrank and you have a lot of handle force. Move the pushrod closer to the bellcrank pivot and you have more leverage but more bellcrank movement. Basically, the larger bellcrank is the solution. We started putting 4" bellcranks into 70's size planes and things got better but as planes got bigger (and heavier) bellcranks stayed at 4". Now add the lightweight hardpoint handle. You start learning to fly by varying the tension on the lines with very little wrist movement - "finger flying". So, unless you want more line tension you need more leverage which means a larger bellcrank. I have gone to a 5" and it works, for me, better than I expected. I can use less movement to get the leverage I need.
So, what is the point - every plane and every pilot is different. Does weight matter, of course it does. Once you have developed a handle style, your bellcrank and horn heights need to conform to it. Most designs reflect the preferences of the designer and the stock horns of the time. They may be completely opposite of what your style needs. A CLPA plane is a gigantic collection of compromises and trying to find the set that lets you shine is half of the fun in this sport. I prefer the top hole, but I will use whatever hole I need to get the ratio I want. Anyway, making sure the horn is solidly mounted to the wing and perfectly in line with the hinges is just as important.
Fresh out of soap - Ken