elevator horn hatch?

[Curare]

Hey guys, I'm just thinking about my current build, and I'd like to have the ability to adjust the elevator horn, both for ratios and for adjustment of neutral. Obviously this means that a decent-ish hole needs to be cut into the tail area, but I'm not sure how big is enough, and what the best way to go is.

I'll be using ball links on the tail, so I assume that I'll need a slot on one side to tighten the locking bolt, and a hole where I can remove the ball link and twist it to adjust.

Just wondering if anyone has a good way of doing this?

Cheers

Greg

[Perry Rose]

I use a 4-40 metal clevis with a half inch hole under the stab on the side opposite the exhaust and a 1/4 inch hole on the bottom under the first hole. Stick a screwdriver through the bottom hole and look through the hole under the stab to unhook/re hook the clevis and turn the clevis through the half inch hole. I made a cable tool to do the turning.

[Randy Cuberly]

I use a 4-40 metal clevis with a half inch hole under the stab on the side opposite the exhaust and a 1/4 inch hole on the bottom under the first hole. Stick a screwdriver through the bottom hole and look through the hole under the stab to unhook/re hook the clevis and turn the clevis through the half inch hole. I made a cable tool to do the turning.

I would definitely recommend against using the typical 4-40 metal clevises on a stunt plane.  The control loads can go too high in the wind and they will definitely break, especially after time from fatigue.  I've personally seen it happen many times.
The best solution in my opinion is the adjustable control horns from Tom Morris with a slider coupled with the aluminum clevises from Ultra Hobby Products.
I'm in a hurry to attend a meeting right now, but will supply some pictures later of a typical installation of mine, unless someone else gets there first.

The first picture below shows My Tempest II before covering.  The second picture shows the Tempest II elevator horn access hole with the aluminum clevis and single horn from Tom Morris.  The third picture shows my Collossus after covering before painting.  The fourth picture shows the access hatch and double control horn from Tom Morris with a Tom Morris Ball Link.  The fifth photo shows the Collossus hatch cover installed.  It has a tab on one end and a screw with blind nut on the other.
The fuselage sides are reinforced with 1/64 plywood on the insides with the hole in the plywood sized smaller than in the balsa to provide a ledge for the balsa cover.  The balsa cover has a ply tab and insert where the screw rests as does the fuselage side.

One thing to note is that using these horns and the clevis requires that the fuselage be widened a bit beyond what most stunters usually are for clearance for the horn and clevis, but that's acually structurally stiffer and a plus structurally.

Randy Cuberly

[FLOYD CARTER]

The threads on a 4-40 metal clevis is about 1/2" long.  Using all or most of the threads should be much stronger than needed for flight loads.  These things are formed from one piece, so the threaded barrel has a seam.  I always solder that seam with silver solder.

F.C.

[EddyR]

What Randy said is true. Some will come on here and tell you it is OK to use them as they have improved a lot. Why take a chance when people have seen them fail. I have seen them fail over and over. If you solder them they are no longer adjustable.

[Tim Wescott]

I've never had a clevis failure.

But then, I changed to ball links before I stopped crashing all the time...

[tom brightbill]

On my latest build, a Shark 45, I put a hole/cover that is .75 x 1.5 with a full radius at each end fore and aft. There are 2" pieces of 3/16 sq. aligned with the top and bottom of the hole to help reduce the chance of stresses.  I put 1/16 ply , .75 x .5, on the inside fore and aft extending into the hole about 1/4" to stabilize the the cover and give something to put the hold down screws through. The cover is 1/32 ply with balsa laminated to a height above the fuse surface then sanded to contour.  Hope this makes sense.  I also use Tom Morris parts now as the time and money invested is too high for me not to.  If that's not do-able for you, at least do as Floyd suggested. Good luck.

[builditright]

Hi
Once you decide on your control type; check out the access hatches I offer. 


http://www.builtrightflyright.com/MiscPgs/AccessHatch/hatch1.htm

[Trostle]

Two variations of an elevator horn hatch cover.

These hatch covers give access to something else beside the elevator horn, but that function is not in the scope of this thread.

Keith

[Randy Cuberly]

Just as a note I added photos and explanation to my original post above showing the installation of the double horn with a ball link and a single horn with the aluminum clevis.
I've used this construction on half a dozen airplanes and never had any problems whatsover.  It is very stiff and functional and very adjustable.

I would reiterate...Do not use R/C clevises...they will fail!!!

Randy Cuberly

[Kim Doherty]

Hey guys, I'm just thinking about my current build, and I'd like to have the ability to adjust the elevator horn, both for ratios and for adjustment of neutral. Obviously this means that a decent-ish hole needs to be cut into the tail area, but I'm not sure how big is enough, and what the best way to go is.
Greg

Greg,

For all the trouble of making a hatch you could just as easily make the rudder and rearmost part of the fuselage removable. Join the rudder to the fuse and cut down ahead of the stab on top and right at the rear edge of the hinge line down below. Hold on with plywood tabs and small bolts down below and a small dowel on top . This provides quick and easy access to any adjustment you need. (including adding or subtracting tail weight).

Kim

[Curare]

Kim you may have just given me an idea. The model is a super chipmunk, which if you know them has a small tail cone between the elevator halves. I think I could make that removable and have access to the horn and the ball link. Thanks for the idea!!

[Allan Perret]

Just as a note I added photos and explanation to my original post above showing the installation of the double horn with a ball link and a single horn with the aluminum clevis.
I've used this construction on half a dozen airplanes and never had any problems whatsover.  It is very stiff and functional and very adjustable.

I would reiterate...Do not use R/C clevises...they will fail!!!

Randy Cuberly

What advantage if any does the aluminum clevis have over ball links ?

[john e. holliday]

It straddles the control horn and the one I have is beefier.  They also take up less space.

[Randy Cuberly]

What advantage if any does the aluminum clevis have over ball links ?

Hi Allan,
The aluminum clevis has a couple of advantages over the Ball links.
1.  They are very free in operation and never tighten up in cold weather as ball links have been known to do sometimes.  This is of course the most important factor.

2.  They are easier to deal with during adjustments.  The hardened pin and screw arrangement is very easy to remove and never requires any access to the other side of the horn.  While it's true the Tom Morris horns have sliding inserts that will stay in the horn slot if treated very carefully when the ball link is removed to make adjustments to the pushrod length, they can and do fall out sometimes and are a royal PITA to get back in the slot through a small access window...I know and this is the main reason I went to using the Aluminum clevises.

3.  The aluminum clevises are very well made and come in different throat lengths (long and short) and are very strong and flex free and I've never seen the slightest indication of wear on the pin (very hard) or the slider in the horn in literally thousands of flights on several airplanes.

The Tom Morris double horn arrangements with the slots is my preference if ball links are to be used.  I always use these double horns for the flaps. with ball links but have had two instances in the past where it was necessary to cut into an airplane to replace a ball link that tightened up in colder weather.  On my next build I'm going to use clevises there also with single horns.

Randy Cuberly

[Allan Perret]

Greg,

For all the trouble of making a hatch you could just as easily make the rudder and rearmost part of the fuselage removable. Join the rudder to the fuse and cut down ahead of the stab on top and right at the rear edge of the hinge line down below. Hold on with plywood tabs and small bolts down below and a small dowel on top . This provides quick and easy access to any adjustment you need. (including adding or subtracting tail weight).

Kim

I did just what Kim suggest here after trying 3-4 different hatch designs, and not being totally happy with any of them.  I made the lower section of the fuse from the hinge line aft removable.  Two 4-40's hold it on.  Comes off easy and gives full access to horn connection.  I also have two 3/8" holes on either side of fuse at the flap horn to disconnect front end of elevator pushrod and remove it out the back if I need to adjust length of rod.  Little more work than just a hatch but finally had something I was happy with.

[Allan Perret]

Hi Allan,
The aluminum clevis has a couple of advantages over the Ball links.
1.  They are very free in operation and never tighten up in cold weather as ball links have been known to do sometimes.  This is of course the most important factor.

2.  They are easier to deal with during adjustments.  The hardened pin and screw arrangement is very easy to remove and never requires any access to the other side of the horn.  While it's true the Tom Morris horns have sliding inserts that will stay in the horn slot if treated very carefully when the ball link is removed to make adjustments to the pushrod length, they can and do fall out sometimes and are a royal PITA to get back in the slot through a small access window...I know and this is the main reason I went to using the Aluminum clevises.

3.  The aluminum clevises are very well made and come in different throat lengths (long and short) and are very strong and flex free and I've never seen the slightest indication of wear on the pin (very hard) or the slider in the horn in literally thousands of flights on several airplanes.

The Tom Morris double horn arrangements with the slots is my preference if ball links are to be used.  I always use these double horns for the flaps. with ball links but have had two instances in the past where it was necessary to cut into an airplane to replace a ball link that tightened up in colder weather.  On my next build I'm going to use clevises there also with single horns.

Randy Cuberly

Yea, I sometimes run into a ball link that is tight right out of the package.  But I work on it a little to see if I can free it up or it doesn't go into the plane.  I have never had one tighten up on me after its service.  To free up a tight one I will pop out the ball and do some very minor trimming of the the 2 outside edges of the plastic housing with #11 blade.  If that doesn't work I put a long 4-40 screw in the ball with a nut tightened to it.  Chuck the screw in a drill motor to turn it at slow speed and put some fine lapping compound on the ball to lap it into the plastic.  Works sometimes, if it don't I throw it away.

[Kim Doherty]

Yea, I sometimes run into a ball link that is tight right out of the package.  But I work on it a little to see if I can free it up or it doesn't go into the plane.  I have never had one tighten up on me after its service.  To free up a tight one I will pop out the ball and do some very minor trimming of the the 2 outside edges of the plastic housing with #11 blade.  If that doesn't work I put a long 4-40 screw in the ball with a nut tightened to it.  Chuck the screw in a drill motor to turn it at slow speed and put some fine lapping compound on the ball to lap it into the plastic.  Works sometimes, if it don't I throw it away.

Alan,

I posted this some time ago:

If you are going to use ball links you will most likely need to adjust them as well. You will need two tools for this. The first are ball link pliers to remove the link from the ball and reinstall it afterward. The second is a ball link resizer of the appropriate diameter to adjust the amount of friction present in the link. The resizing tool is adjustable in diameter to enable you to remove just the right amount of material. You will only need to rotate the tool a couple of times before you retry the ball. Both of these tools can be purchased at almost any hobby shop.

Kim.

[Allan Perret]

Alan,

I posted this some time ago:

If you are going to use ball links you will most likely need to adjust them as well. You will need two tools for this. The first are ball link pliers to remove the link from the ball and reinstall it afterward. The second is a ball link resizer of the appropriate diameter to adjust the amount of friction present in the link. The resizing tool is adjustable in diameter to enable you to remove just the right amount of material. You will only need to rotate the tool a couple of times before you retry the ball. Both of these tools can be purchased at almost any hobby shop.

Kim.

I see the pliers at Tower but not the sizing tool.  There are sizing tools at the heli sites but they are specific to the size ball links used for heli's.  Could not find one to fit the 1/4" balls we use.

[Randy Cuberly]

Alan,

I posted this some time ago:

If you are going to use ball links you will most likely need to adjust them as well. You will need two tools for this. The first are ball link pliers to remove the link from the ball and reinstall it afterward. The second is a ball link resizer of the appropriate diameter to adjust the amount of friction present in the link. The resizing tool is adjustable in diameter to enable you to remove just the right amount of material. You will only need to rotate the tool a couple of times before you retry the ball. Both of these tools can be purchased at almost any hobby shop.

Kim.

Kim,
I have those tools and have used them, but with the extreme thermal cycling we experience here in AZ, it's necessary to get them so loose as to be unusable to insure that they won't eventually tighten up.  We see temperature varaitions as high 150 degrees F. from night to storage shed temperature in the summer time.

I'll stick to metallic components just like the military specs do!!!

I never want to cut into a finished stunter again!  And I don't want to build take apart airplanes!

Thanks,
Randy Cuberly!

[Kim Doherty]

 And I don't want to build take apart airplanes!

Thanks,
Randy Cuberly!

They are all take apart airplanes Randy, just a matter of when and how.

Kim.

[Randy Ryan]

What Randy said is true. Some will come on here and tell you it is OK to use them as they have improved a lot. Why take a chance when people have seen them fail. I have seen them fail over and over. If you solder them they are no longer adjustable.

I quit when I found ball links. I never had one fail but I always worried about them. The thread fit is very loose and the jam nits would always come loose leaving the clevis totally bearing on the threads alone. The threads wore and got looser with time.

[john e. holliday]

Jam nuts with nylon insert work well for me.  Have never had one come loose yet.

[Dick Pacini]

They are all take apart airplanes Randy, just a matter of when and how.

Kim.

Keep them long enough and they are fall apart planes.

[Randy Cuberly]

Keep them long enough and they are fall apart planes.

Unfortunately very true, Dick!   I usually give mine away and let someone else experience that phenomonen!LL~

Randy Cuberly

[Dick Pacini]

You know they are old when the only thing left hanging by the leadouts is the bellcrank and pushrod.