How to install Horns into balsa sheeted foam core rudder?
08-30-2006, 09:02 AM
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How to install Horns into balsa sheeted foam core rudder?
I am planing to install dual Sullivan Control Horns into the rudder for a pull-pull.
http://www2.towerhobbies.com/cgi-bin...?&I=LXFV36&P=0
Question is how do I install these so it becomes strong enough? There will be 4 screws going thru the first horn into the second horn on the oposite side of the rudder creating a lighter weight pull-pull horns. This will be a lighter weight option than that of the heavy steel bolt that is included in Durbo's dull-dull kit. However, I am worried that if I don't reinforce the rudder, where the horns are going to be instaled, the rudder structure will soon be weakend. How do I install and stenghten this part of the rudder? If I would have only a wood structure I would put some CA into the drilled holes where the screws go, but now the core is foam wich prevents me using CA as I understand will eat the foam instead.
http://www2.towerhobbies.com/cgi-bin...?&I=LXFV36&P=0
Question is how do I install these so it becomes strong enough? There will be 4 screws going thru the first horn into the second horn on the oposite side of the rudder creating a lighter weight pull-pull horns. This will be a lighter weight option than that of the heavy steel bolt that is included in Durbo's dull-dull kit. However, I am worried that if I don't reinforce the rudder, where the horns are going to be instaled, the rudder structure will soon be weakend. How do I install and stenghten this part of the rudder? If I would have only a wood structure I would put some CA into the drilled holes where the screws go, but now the core is foam wich prevents me using CA as I understand will eat the foam instead.
08-30-2006, 09:47 AM
#2
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RE: How to install Horns into balsa sheeted foam core rudder?
It's easy to reinforce that type structure.
Very thin plywood works great. I don't remember if the stuff I have is 1/64" or what, but I can cut it with scissors. I cut a "plate" that I figured was about 3-4 times the area of the horn's base. I traced around it on the rudder and then lifted the covering within that area. I wanted to look at the balsa anyway, so pulling the covering wasn't extra work. Gluing the plate down, you could use any glue, they'd all work well. I have found thick CA to be almost weightless and easy enough when positioning plates where you could be assured to get it right the first try.
After the plate was down, I covered it. The plane was white Ultracote, and I got some.
I only put a plate on one side. Depending on the size of the airplane, you could cover both. You could make the plate larger or smaller. Use a larger on one side and a smaller on the other if you want graduated strengthening. Don't cover, paint it, if you prefer. Don't pull the covering, just pin-***** the existing a lot. whatever...........
Very thin plywood works great. I don't remember if the stuff I have is 1/64" or what, but I can cut it with scissors. I cut a "plate" that I figured was about 3-4 times the area of the horn's base. I traced around it on the rudder and then lifted the covering within that area. I wanted to look at the balsa anyway, so pulling the covering wasn't extra work. Gluing the plate down, you could use any glue, they'd all work well. I have found thick CA to be almost weightless and easy enough when positioning plates where you could be assured to get it right the first try.
After the plate was down, I covered it. The plane was white Ultracote, and I got some.
I only put a plate on one side. Depending on the size of the airplane, you could cover both. You could make the plate larger or smaller. Use a larger on one side and a smaller on the other if you want graduated strengthening. Don't cover, paint it, if you prefer. Don't pull the covering, just pin-***** the existing a lot. whatever...........
08-30-2006, 09:49 AM
#3
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RE: How to install Horns into balsa sheeted foam core rudder?
There is foam safe CA.
And you don't have to paint wood to fuel proof it, you can also CA it and get moderate fuelproofing. A tail usually won't see much raw nitro, just oil residue and the CA handles that just fine.
And you don't have to paint wood to fuel proof it, you can also CA it and get moderate fuelproofing. A tail usually won't see much raw nitro, just oil residue and the CA handles that just fine.
08-30-2006, 09:55 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
And epoxy would work with foam. As little as you'd need, it wouldn't add much weight.
BTW, canopy glue can be applied to the bottom of horns when they're installed. It gives a bit of insurance to the strength of the attachment. It sticks to the horn's material and bonds it more securely to the airframe than screws might. You won't have to tighten the screws until the horn's foot is crushing the balsa to be sure that the horn is securely fastened. It also sticks to the covering securely. If you pin-***** the covering where the glue will go, the glue will also serve to strengthen the balsa it penetrates, but only after it has dried. So you wind up with a stronger installation and stronger wood underneath that installation.
BTW, canopy glue can be applied to the bottom of horns when they're installed. It gives a bit of insurance to the strength of the attachment. It sticks to the horn's material and bonds it more securely to the airframe than screws might. You won't have to tighten the screws until the horn's foot is crushing the balsa to be sure that the horn is securely fastened. It also sticks to the covering securely. If you pin-***** the covering where the glue will go, the glue will also serve to strengthen the balsa it penetrates, but only after it has dried. So you wind up with a stronger installation and stronger wood underneath that installation.
08-30-2006, 10:14 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
darock,
Thank you for all these tips. It does not sound difficult at all. I will use one of your methods.
Thank you for all these tips. It does not sound difficult at all. I will use one of your methods.
08-30-2006, 11:13 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
Mike, what kind of wood would you use on a dowel to be in a rudder pull-pull instalation on a 1/4 scale Extra?
08-30-2006, 11:14 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
for Pull-pull.. you might consider this type of horn
http://www2.towerhobbies.com/cgi-bin...?&I=LXEMF5&P=7
Yeah, they're a bit 'heavier', but where i used them in the tail of a Hog Bipe, I was planning on using a saito 100, so i could use a bit of weight in the tail. As it turned out, it balanced perfect!
anyways, what I do is:
once you've got the rudder sheeted, use a sharpened brass or steel tube to drill a 1/2" to 3/4" hole through the rudder. Install a poplar or other hard-wood dowel to match the hole, sanding it flush on either side. install the dowel with epoxy. Then drill a hole through the dowel that fits the through bolt on the control horns. this will never pull out, or get loose. this is what i've used in the past, and it has never given me a bit of trouble, on everything up through giant scale stuff.
http://www2.towerhobbies.com/cgi-bin...?&I=LXEMF5&P=7
Yeah, they're a bit 'heavier', but where i used them in the tail of a Hog Bipe, I was planning on using a saito 100, so i could use a bit of weight in the tail. As it turned out, it balanced perfect!
anyways, what I do is:
once you've got the rudder sheeted, use a sharpened brass or steel tube to drill a 1/2" to 3/4" hole through the rudder. Install a poplar or other hard-wood dowel to match the hole, sanding it flush on either side. install the dowel with epoxy. Then drill a hole through the dowel that fits the through bolt on the control horns. this will never pull out, or get loose. this is what i've used in the past, and it has never given me a bit of trouble, on everything up through giant scale stuff.
08-30-2006, 11:19 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
I like this idea of using a dowel as well. Sound rigid and easy to install too.
The Dubro horn you are suggesting is too heavy for me. I am trying to go ultra lite of this baby and I don't need extra weight in the tail because I would like to have rear mounted elev servos. This without having to add weight to the front to get it in balance. I have used the pull-horn as you are suggesting on my previous model and they worked very well but was unfortunatly too heavy in my opinion.
The Dubro horn you are suggesting is too heavy for me. I am trying to go ultra lite of this baby and I don't need extra weight in the tail because I would like to have rear mounted elev servos. This without having to add weight to the front to get it in balance. I have used the pull-horn as you are suggesting on my previous model and they worked very well but was unfortunatly too heavy in my opinion.
08-30-2006, 11:22 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
The only really heavy part of that horn is the screw itself. I've thought about substituting an aluminum or (!) Titanium screw to get rid of the weight. The dowel idea adds a bit, but the piece of mind, especially on the elevator and ailerons, is worth it. Whacha building?
08-30-2006, 11:25 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
Mcmike, Titanium sounds too dear to me but I wish... I agree with you, the steel screw is the only heavy part of the Dubro pull-pull kit and it is too heavy to be used. I am about to start build the Lanier Extra 300S 1/4 scale kit 72" as soon as I recive the delivery (hoping next week). While waiting for this I am brainstorming the outline including hardware, equipment, replacements such as CF gear + wingtube, and material for covering... The rudder pull-pull installation is just one of these things.
Minnflyer, ok I guess finiding pine sounds easy enough. Thanks guys.
Minnflyer, ok I guess finiding pine sounds easy enough. Thanks guys.
08-30-2006, 11:45 AM
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RE: How to install Horns into balsa sheeted foam core rudder?
Minnflyer has it right. That will be the strongest mount for the horn be it bolt through or screw to. Personally I would go bolt through. You will not save enough weight to be worth the extra hassle and possible failure when the screws work loose and pull out.
Bob
Bob
08-30-2006, 12:09 PM
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RE: How to install Horns into balsa sheeted foam core rudder?
Bob, I will go for the Sullivan type, URL at top of this thread, wich has 4 screws to it. These screws will go through the dowel and the opposite horn on the other side of the rudder and then nylonthread nuts + locktite. This sounds plenty strong and lite weight to me. I am very happy with the help I recived.
08-30-2006, 12:34 PM
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RE: How to install Horns into balsa sheeted foam core rudder?
I used to like the Rocket City style horns, or anything resembling a threaded rod fixed in a dowel, until I also came around to the line of thinking that these pieces of steel in the tail really are too heavy. That's when I started cutting my own horns from sheet phenolic. It's a little trouble, but not a lot if you have a power bandsaw or jigsaw to do the cutting. A drill press for the holes also helps the precision, which is important in getting the linkage holes aligned with the rudder hinge line. Here's a pull/pull tail horn I just made up for a quarter scale Edge. Sheet phenolic from Aircraft Spruce is inexpensive, tough, light-weight, durable, easy to work. Width between linkage holes here is 3". Install by cutting a slot in the rudder and glue in with epoxy or polyurethane. The little notch at the rear helps me line up the horn in the slot so it's perfectly centered.
Other pics are a pair of elevator horns for the same project. Aileron horns are similar. Push/pull horns are doubled, and ball link goes in the middle so as to avoid any twisting strain on the connection. These are cut and drilled in a stack of four to ensure same throw on paired control surfaces. I've done my last couple years worth of models with these, and like them more and more.
Other pics are a pair of elevator horns for the same project. Aileron horns are similar. Push/pull horns are doubled, and ball link goes in the middle so as to avoid any twisting strain on the connection. These are cut and drilled in a stack of four to ensure same throw on paired control surfaces. I've done my last couple years worth of models with these, and like them more and more.
08-30-2006, 12:42 PM
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RE: How to install Horns into balsa sheeted foam core rudder?
Very nice gear... Very ambigious, I bet your horns will be very light and strong.
08-30-2006, 01:16 PM
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RE: How to install Horns into balsa sheeted foam core rudder?
ORIGINAL: majortom-RCU
I used to like the Rocket City style horns, or anything resembling a threaded rod fixed in a dowel, until I also came around to the line of thinking that these pieces of steel in the tail really are too heavy. That's when I started cutting my own horns from sheet phenolic. It's a little trouble, but not a lot if you have a power bandsaw or jigsaw to do the cutting. A drill press for the holes also helps the precision, which is important in getting the linkage holes aligned with the rudder hinge line. Here's a pull/pull tail horn I just made up for a quarter scale Edge. Sheet phenolic from Aircraft Spruce is inexpensive, tough, light-weight, durable, easy to work. Width between linkage holes here is 3". Install by cutting a slot in the rudder and glue in with epoxy or polyurethane. The little notch at the rear helps me line up the horn in the slot so it's perfectly centered.
Other pics are a pair of elevator horns for the same project. Aileron horns are similar. Push/pull horns are doubled, and ball link goes in the middle so as to avoid any twisting strain on the connection. These are cut and drilled in a stack of four to ensure same throw on paired control surfaces. I've done my last couple years worth of models with these, and like them more and more.
I used to like the Rocket City style horns, or anything resembling a threaded rod fixed in a dowel, until I also came around to the line of thinking that these pieces of steel in the tail really are too heavy. That's when I started cutting my own horns from sheet phenolic. It's a little trouble, but not a lot if you have a power bandsaw or jigsaw to do the cutting. A drill press for the holes also helps the precision, which is important in getting the linkage holes aligned with the rudder hinge line. Here's a pull/pull tail horn I just made up for a quarter scale Edge. Sheet phenolic from Aircraft Spruce is inexpensive, tough, light-weight, durable, easy to work. Width between linkage holes here is 3". Install by cutting a slot in the rudder and glue in with epoxy or polyurethane. The little notch at the rear helps me line up the horn in the slot so it's perfectly centered.
Other pics are a pair of elevator horns for the same project. Aileron horns are similar. Push/pull horns are doubled, and ball link goes in the middle so as to avoid any twisting strain on the connection. These are cut and drilled in a stack of four to ensure same throw on paired control surfaces. I've done my last couple years worth of models with these, and like them more and more.
09-03-2006, 08:41 PM
#19
RE: How to install Horns into balsa sheeted foam core rudder?
Drill a hole in the foam BEFORE you sheet it.
Cut your wood dowel to a length thats just a bit wider than the thickness of the foam. Now sand the ends of the dowel so that it matches the taper of the rudder. Install the dowel and glue in with epoxy or polyurathane glue. When the glue dries, you have to sand a little bit.
NOW sheet your rudder. Sheet right over the hardpoint.
Mark on the plan where the hardpoint is located on the rudder. That way you can be sure to hit the hardpoint when you install the horn.
Cut your wood dowel to a length thats just a bit wider than the thickness of the foam. Now sand the ends of the dowel so that it matches the taper of the rudder. Install the dowel and glue in with epoxy or polyurathane glue. When the glue dries, you have to sand a little bit.
NOW sheet your rudder. Sheet right over the hardpoint.
Mark on the plan where the hardpoint is located on the rudder. That way you can be sure to hit the hardpoint when you install the horn.
09-04-2006, 09:12 PM
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RE: How to install Horns into balsa sheeted foam core rudder?
Rcpilot's method - whether using a dowel or a rectangular piece of hardwood - depending on the type of control unit you will be using -is what I believe to be the best and the technique I use for ALL control surfaces.
09-05-2006, 08:40 AM
#21
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RE: How to install Horns into balsa sheeted foam core rudder?
If you're planning to use a pull-pull system, then drill through your hardpoint and run a threaded rod straight through so that you've got threaded rod projecting on both sides of the rudder. There are a couple of different fittings available that thread onto rod and would give you connecting points out on the ends of the rods.
BTW, you need to consider the strength of the surface you're trying to reinforce or strengthen. If the structure isn't very strong, then whatever you use to strengthen it should cover a lot of area, as the only real strength that results is going to be out where your stiffener ends and that structure begins.
Since you plan to drive all the rudder movement force through that reinforcement, it's worth considering how strong the rudder is out where the reinforcement is going to end. Strong reinforcement is great for holding horns, but doesn't do a thing for the rest of the rudder. And is the rudder going to be seeing a lot of force? Is it big? Is the airplane heavy? Are you going to try and use the rudder in fairly high speed maneuvers? like do you use full rudder in snaps like most guys do? and are you one that doesn't bother to slow down much when you snap the sucker? and...... I've run out of breath......
BTW, you need to consider the strength of the surface you're trying to reinforce or strengthen. If the structure isn't very strong, then whatever you use to strengthen it should cover a lot of area, as the only real strength that results is going to be out where your stiffener ends and that structure begins.
Since you plan to drive all the rudder movement force through that reinforcement, it's worth considering how strong the rudder is out where the reinforcement is going to end. Strong reinforcement is great for holding horns, but doesn't do a thing for the rest of the rudder. And is the rudder going to be seeing a lot of force? Is it big? Is the airplane heavy? Are you going to try and use the rudder in fairly high speed maneuvers? like do you use full rudder in snaps like most guys do? and are you one that doesn't bother to slow down much when you snap the sucker? and...... I've run out of breath......
09-05-2006, 09:01 AM
#22
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RE: How to install Horns into balsa sheeted foam core rudder?
BTW, I just noticed two things.
My suggested threaded rod was suggested by mcmike back in post #8. Sorry, but I get excited to help and overlook stuff.
And it dawned on me that the threaded rod could be a carbon fiber rod. That'd be light. The fittings would have to be bonded to the rod, but we're modelers, right? we can make anything....
My suggested threaded rod was suggested by mcmike back in post #8. Sorry, but I get excited to help and overlook stuff.
And it dawned on me that the threaded rod could be a carbon fiber rod. That'd be light. The fittings would have to be bonded to the rod, but we're modelers, right? we can make anything....
09-06-2006, 07:42 AM
#24
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RE: How to install Horns into balsa sheeted foam core rudder?
Oh hey, I didn't know the goal was to spend exorbitantly.
Forget my idea of using scrap plywood. That won't cost nothin'.
However, the carbon fiber rod is more expensive than the other suggestions. You do plan to use gold thread for the pull cable, right? [sm=wink_smile.gif]
Forget my idea of using scrap plywood. That won't cost nothin'.
However, the carbon fiber rod is more expensive than the other suggestions. You do plan to use gold thread for the pull cable, right? [sm=wink_smile.gif]
