Boss

I have been in R/C Airplane Modeling for 15 years and really
enjoy building kits. However, I need some professonal advice
on Control Horn Installation. Somebody please reveal the
secret to me as how to drill those little holes through control
surfaces and be in line. I have to know this secret before I
die. Thanks in advance for all of your "Professional Advice"..

Chuckr53-RCU

My Feedback: (40)

Take a look at this thread...http://www.rcuniverse.com/forum/m_31...%2Chorn/tm.htm

I like the solution in post #20

J_R

The secret is to get the hole perpendicular to the surface. Use something like a GP dead center hole locator to mark the holes. Then either use a drill press or a Higley Tap and Drill Guide to drill holes perpendicular to the surface. If it is a tapered surface, the Higley tool works better than a drill press.

http://www.members.aol.com/harryhig/Tools1.htm

JR

CafeenMan

Use a pin vise and carefully eyeball. I wouldn't buy specialty tools for this. If the surface is tapered and you use a plate on the other side, it's not going to be mechanically correct no matter what you do. After drilling the holes and making sure it works, put some thin CA in the holes to harden it all up. Let it dry thoroughly before mounting the horn again.

J_R

I beg to differ. If you drill a tapered surface the holes line up perfectly. It does, however, move the plate a little forward. If the surface is thick enough, you may have to remove a small amount of the plate to keep it out of the bevel.

Tapping the plate before you start helps too. You won't have to fight to start the threads. Using socket head cap screws keeps holes in the covering to a minimum.

I used a pin vise forever and NEVER had the holes line up correctly without enlarging the holes. The jig was under 10 bucks last time I looked and it works for wing bolts and any other holes you want perpendicular to the surface you are drilling.

Hardning the holes, or the entire area under the horn is a good idea. If you put several pin *****s under the horn, the CA penetrates deeper. You may have to re-drill the holes after the CA cures.

If the surface is thick enough, I inlay 1/64 ply to support the horn and plate.

CafeenMan

J_R - Think about it mechanically. If the surface tapers, and the bolts are perpendicular to the horn base and the plate they thread into, then there's no way the horn and the plate can both sit flat on the surface. Something has to give - usually the balsa.

The BEST way to do it is to inlay a piece of plywood on the horn side and use wood screws. Toss out the plate. Then there are no problems and you save your $10 for something else.

J_R

OK, think about it. If the surface is say, 1/2 inch thick, and you drill the holes perpendicular to it, the horn is going to sit flat. When the surface is that thick, I don't think too many are going to use the little 40 sized horns. Much more likely they will use the triangular shaped base ones with much longer bolts. The base will flex as the bolts are tightened, and it does not tear through the balsa. On surfaces on smaller planes, there is less taper and it becomes a non issue if the plate is overtightened into balsa that has been hardenedby the tiny amount envolved. In any case, the horn will set flat, which is my concern, the plate may be at an angle. If it is really a big deal, you can shim under the plate with a tapered shim.

If you have not tried it, try it.

It works great. I do not use wood screws for anything on the outside of a plane. Sooner or later, they are coming out from vibration, fuel, exhaust residue and just cleaning the plane. I will take bolts every time.

CafeenMan

Right - the horn will be flat against the surface, but the plate on the other side is going to be off quite a bit.

Ok, but geometry is geometry and a triangle is a triangle. If the surface is 100 miles thick there's still the same problem. Plus finding a drill bit long enough.

Personally, I think flexing the base isn't a good thing to do. I didn't know this discussion was specific to a certain type of control horn and a certain thickness control surface.

It may not "tear through" the balsa, but it will certainly crush it a fair amount if it's tightened properly unless rock hard balsa is used. CA is only marginally effective hardening a surface. As long as we're talking about surfaces this thick, I wouldn't ever trust a control horn through balsa on anything over a .60 size plane.

No, it's not a big deal at all which goes back to my original post. I don't see the point in buying tools - even only $10 tools - to make an easy job just as easy as it was already.

I do put plates under the horn to rotate it forward so that it aligns properly with the hinge line when necessary. But as I said, if the control surface is tapered, I'm not going to use a plate. They're ugly anyway and putting a shim under it will just make it uglier. My method is very secure, looks good and has never been a problem for me or anyone I've built planes for.

I don't have problems with wood screws coming loose. For landing gear, engines, engine mounts, etc, I use real bolts. For control horns, a wood screw going into a hard point works fine, lasts for years and has never given me any problem. Plus, I can tighten down the screw more securely than I could if I had a plate on the other side of a piece of balsa which would crush - even when flooded with CA.

Anyway, do whatever works for you. My whole point was that it's not that big of a deal. I've found ways of doing things that I feel secure with and my planes only die on impact or from movers, but not in the air due to any type of structural failure. Last time I had a plane break in the air was in the early 80's where I took a very light plane with way too much power in a terminal velocity power dive and cracked the elevator due to flutter. That wasn't a building or design problem - that was a stupid pilot.

Here's what I'm talking about. If these were solid wood I would still inset the hard points. The points would be smaller, but in this case they had to be long enough to span across to ribs to anchor them too. Also, these ended up weighing 2.25 ounces for all four of them.

http://www.airfieldmodels.com/inform...ruction/08.htm

J_R

In looking at your page, I will say this. We sure don't use the same building techniques

I thought the initial question was how to get the holes lined up. Like I said, and I suspect Boss has the same problem, I used to use a pin vise, freehand, and the hole never lined up. If you assure that they are perpendicular, they will line up if the holes are marked correctly before they are drilled. When I used a pin vise, freehand, the holes would invariably have to be "opened up" so that the screws or bolts would go into the holes in the plate.

When you use a pin vise, freehand, on thicker surfaces, the problem in lining the holes up gets worse. You can still use the pin vise with the jig, but, the holes align when your done. If you have an old spinner adapter, and a drill press, you can make the jig for nothing more than a few minutes of work.

The same is true of wing bolts. If the holes are perpendicular to the surface and drilled into the hold down block using a jig, with the wing clamped in place, you don't have to enlarge the holes to keep the bolts from binding.

CafeenMan

J_R - I made that plane as complicated as I possibly could. I don't normally build up ailerons like that on a .40 powered ship. Tapered solid balsa works just fine. But, because of the inlays I wanted to save weight wherever possible, and I'm sure the built up flaps and ailerons are lighter than comparably sized solid ones would have been.

Anyway, in re-reading I agree with your assessment. Personally I don't mind opening the holes slightly if needed because the strength is necessary in the wood under the horn, so a slightly bigger hole won't affect it any. But it will allow the horn to shift if it's not tightened securely. On a larger surface, I would probably ship up the aileron and use a drill press, but then again, I'd use the hardpoint so it wouldn't be necessary. I can eyeball a pin vise close enough to not matter. But if I had to ensure the hole was aligned all the way through, then yeah, something better than my eyeball would be needed.

Boss

Hey guys, thanks a million for all the replies, and websites to turn
to for study on this problem. I have decided after reading all of
your replies that I am not alone in this problem. Just finished
installing horns today on an Edge 540 and faced my usual frustration
while doing the job, but just as all my models in the past finally
got all of the horns installed. Evidently there is really not a "FOOLPROOF"
way to do this...THANKS AGAIN FOR ALL THE ADVICE....

aimmaintenance

I've read over this thread a couple of times to see if I misunderstood the question.
You are talkin about putting the little plastic horns on ailerons, rudders, elevators, etc. right?
You are WAY overcomplicating a simple thing.
Stick your pushrod out. Plop the horn down where it looks good. Run the little screws through it and into the back plate. hook it up. go fly.
Ok I might harden the holes if I remember to.

Boss

Okay Crashedafew...I am proud to hear someone does
not have a problem with this...Okay on the pushrod
but a little more difficult with pull-pull cables etc...and
even with the pushrods I seem to make it difficult...

CafeenMan

Boss - You said you've been building for 15 years. What have you been doing up to now? It must be working although obviously not to your liking or you wouldn't be asking.

If you want it to line up perfectly, then put the side you are mounting the control horn on UP on a drill press. Shim up the trailing edge until the side that is up is level. Drill your holes and you've got it.

Umm... in case I didn't mention it, if you put hard points in the surface, you can do away with the nylon plates and the hole alignement isn't nearly as critical.

aimmaintenance

Sorry bout that.
I wasn't thinkin about pull pulls.
I had pushrod method stuck in my brain I guess.
Pull pulls aren't really any more critical. (IMO)
Unless I'm missin out on something.
just eyeball em in and commence a screwin.

CafeenMan

Well, here's another way of doing pull-pulls - it's what I'm doing on my latest project. The method is lighter, more secure and stiffer than nylon horns. And - no drilling required.

Chuckr53-RCU

My Feedback: (40)

Boss asked for a simple solution on how to drill straight thru a surface to precisely hit the holes on the backplate. It's complicated because you could be mounting the control horn on a flat or tapered surface.

For the flat surface, there are many "easy" solutions, a fair number have been mentioned above.

For tapered surfaces, it's complicated, because of the angles. Drilling holes perpendicular on one side of the surface results in holes closer to the LE of the surface on the opposite side. If you're mounting a predrilled plastic backplate, the edge of the backplate might extend beyond the edge of the surface and cause binding. I've attached a rough drawing to illustrate. I'm not an expert myself, but I'd like to hear how to deal with this, using the plastic backplate usually provided with the control horn if possible. What I've done in the past is to toss the plastic back plate, and glue a small piece of lite ply the matches the shape of the control horm base to the control surface before covering, then just drill through the lite ply. This doesn't work out totally since the nuts won't lie flat on the lite ply side, but a little drop of lock tite on the nut holds just fine.

Boss

Well Cafeenman thanks for the hard point idea...I have been building
for about 15 years, the first five or six I simply played with Trainer
Type planes, then got out of hobby for couple of years...Now lately
I found a club to belong to and found there were things other than
trainers...But this mounting control horns has always been a problem
for me, especially tapered surfaces...I have never been able to
figure out how to get the angle correct on a tapered edge...but
think the drill press idea may have solved my problem...On the hard
point do you replace the ole base plate with just a nut on the back side..???

CafeenMan

Get a piece of hardwood or aircraft plywood 1/8" x 1/2" x 3/4" and inset it so it is flush with the control surface. Then drill pilot holes in it, harden them with thin CA, cover it and use wood screws to mount the horn.

SST

My Feedback: (2)

I just locate the horn, and glue it down, chuck up a small drill in the ol' Ryobi and drill thru, using the horn as a guide, and drop the screws through. Engage and tighten the backplate. The glue joint to the horn is not very durable, as the glue doesn't stick well to the nylon, but it's generally good enough to hold the horn in place to locate the holes.

Jerryfwiw

My Feedback: (2)

I agree, the only way to mount a control horn is to place it where you want it, using thin CA glue it in place. match drill the holes and use servo mounting screws instead of the bolts. A ball wrench is the only safe wa, without slippage, to install the screw. The point on the screw will find the hole in the plastic nut plate easier than the bolt. If the screws stick out too far on the opposite side use a Dremel cut off wheel to trim them off.

Jerryfwiw

Boss248

Ha CafeenMan...is that an Ugly stick in the pics.???
I usually install the controll horns before I cover the plane if it is a kit but I almost always do a fair amount of cussing if I am trying ti do the normal horns on a taper surface. No matter what I do the little back up plates will not catch but 1 screw...I think there is a little gremlin moving the hole as I try to stab it, hold the plane, drink some coffee and hunt for the tiny always not where I left it screw driver.

I really like to use the hard point method if it is possible...I just don't like that nylon plate on the top of the ail., elev.

CafeenMan

Sort of - it's Rustik

DaveGell

I too can never seem to get the holes drilled properly for the nylon control horns, especially on tapered control surfaces. I never seem to get the holes drilled so that the screws line up with the nut plate. I've two solutions.

The first is on that I got from a hint in RC Report a couple of years ago. Drill the three holes, using the control horn as a template. Enlarge the holes so that pieces of inner ny-rod fit snuggly in them. Glue nyrod pieces into the holes, cutting them off flush with the surface. Use sheet metal screws to attach the horn to the surface. The ny-rod acts as a screw anchor to prevent the sheet metal screw from pulling out. I use the button head screws so that they can be tightened with a hex wrench.

The second method is to replace the nylon horns with the type that uses a through bolt, so that you need drill only one hole.