IDS install

[Wayne]

Recently I did an IDS install and I tried to document the process with a ton of photos. Hopefully I remember some of the things I "learned" along the way. Please feel free to make corrections if I screw up. I am no expert and thanks to the folks that took the time to teach me the tricks. Sadly, I'm not aware of any thread or instructions that really go into the full details of these installs. There are a lot of little things to watch for, and I think I have forgotten some already. Yikes!

For this posting we will be using the Servorahmen IDS Mono for KST X08 servos. But it is the same for all of these plastic systems.

First up we will start with the servo tray as it has a little work for us to do. Since we are using a wing servo, we will be using the 4 small parts on the right. The parts on the left side would allow the use of the non-wing servo.. I guess, never done that.

The parts on my kit needed a little sanding to fit, you want this snug, so don't over do it. Hopefully Servorahmen will clean up their tooling. (p.s. I think they have a newer kit then shown here.) The larger part in the upper right has a little extra plastic from molding that can be trimmed off. In the photo below I am sanding a bevel onto the side that allows the servo to actually fit in. This was required on my parts for the servo to fit.

After sanding the little parts are pressed in and pushed flush with the bottom of the tray. The flat face points up to the servo.

Here is a view from the bottom:

Secure the little parts with some CA glue and let it cure. While waiting I prep the other trays.

Onto the Spoon (control horn). Locate this little thing.

Clip it out and assemble like this. The little tabs pointing up can be cut off, they are just part of the injection process. It is a good idea to sand off all of the other tabs, especially at the end where the linkage installs.

 

[Wayne]

OK - That was all pretty easy, but now we are going to get into the bread and butter of this install.
Let's figure out what pushrod length we are going to need. Just set the tray in your wing where it should be located. And you can measure or just try out the different pushrod lengths and see what is going to work.

In the photo above the servo tray is forward in the wing towards the spar web, and the plastic lip of the tray is under the wing skin. I can still get to all of the screws to remove the servo should it ever need to be replaced. The sample pushrod is being checked for length. In this photo the pushrod is far too long, we want it to be pretty close to the hinge line. Shoot this is the shortest that came in the kit!! Yikes, what to do? Well, Servorahmen offers shorter pushrods. Here are the medium and the mini lengths shown for comparison.

Notice the longer pushrods feature a slight bend in them, and the shorter do not. But there are servo and spoon ends to these arms, notice that one end has slightly more plastic around the pin. This is where my memory goes fuzzy, but think the smaller ends go to the spoon.

Now for the fun! Selecting the correct servo arm. The kit comes with a generous selection but how the heck do you know which is right?

Well, a good rule of thumb is start with the shortest one for ailerons, let's call that #1, and then go up #3 for flaps. Ideally we want to use as much of the servo resolution as possible. If we end up with too large an arm and have to cut servo travel down to 50% in the mix, it is basically throwing away a lot of the servo performance we paid a bunch of money for. Don't worry, it is not too hard to swap to a different arm length even after things are fully installed. (If you like a lot of roll rate, maybe #2 for the ailerons.)

The above arms will be pretty close for most composite models that have thin wing sections at the hinge line. If you have a thicker section at the hinge line, it has the effect of making the flight surface control horn taller, so a longer servo arm may be needed to get similar throws. In this case I'm building a smaller 2 meter plane with a rather thin airfoil.

I don't have a good picture of this, but the larger end of the pushrod will fit into the servo arm, but if your parts are like mine, they will need a good amount of clean up to fit nicely and not get stuck. Here is what this will look like after some clean up.

Please note that the pushrod has a reinforcement spline that helps keep it nice and stiff, but for full servo travel it fits into a matching groove in the servo arm. I had to sand both the sides and the spline to get a smooth fit here.

I have a very small pair of channel locks that made pin installation easier. But you can just push them in with a table edge, etc. I ended up installing and uninstalling several times as I figured things out. This photo also shows the pushrod spline nicely, but I have the wrong end of the pushrod installed into the arm!!

 

[Wayne]

OK - Onto the fun part, cutting up our model. I actually find this part more enjoyable. Our goal is to fit the spoon into our flight surfaces, and make a passageway for the pushrod through the trailing edge of the wing.

On this build I came up with a very useful tool to hold the wing, let me tell you, this is so handy to have, and while it will take a really long time to build it, it is worth doing. Here is a picture of this helping tool:

It is a cardboard box. LOL Just put some heavy stuff inside it to keep it from flipping over. I use some masking tape to hold the flight surface at about a 90 degree angle. If your plane has tighter hinges, then whatever angle you can get, but, if you don't think that is enough for how you fly, you will need to loosen up the hinge at this time. This is not uncommon with some brands of planes, the trick is to get a small file inside the gap and sand the hinge line down some. Do a little a time. This plane did not need any of that, so no photos to show you. Many planes will not allow the aileron to flex 90 degrees as shown in this photo, and that is fine, they don't need this much travel, but it sure makes this install easier for me.

We start with locating where the pushrod will be coming out of the wing. Take your time, get this right. I then use a dremel and trim the gap seal in that area. The tape marks the total width I would like. This is the width of the spoon we will be installing.

We can test fit the spoon to see how we are doing. I like to keep this cutting to a minimum. I screwed up on this first one. Do better than me!

With the spoon removed you will see that I have also made room for the spoon to slip into the flight surface.

When you look at the spoon, notice that the pin hole is offset to one side, this is important geometry, we want this offset to point away from the hinge. This gives us a longer arm and more effective control. (again the little plastic bits pointing up should be cut off.)

Small hobby files are very handy for cleaning up your cuts. In this photo you can see that I have opened up the sub trailing edge to allow the pushrod with the spoon installed to pass through. Don't be shy with the tape, it will keep your plane nice and clean while you are working on her. A slip of a file, or some extra glue really can make a mess quick.

See, that wasn't so bad was it?

 

[Wayne]

Here comes the part where we take our time and get things really fitting.

First up a little trick that worked well for me was to use a hobby file to secure the spoon during the test fitting. The teeth of the file helped hold things securely while checking over everything. Later when we are gluing in the spoons I used the file to lock them into place while glue cured.

We still have clean up in the flight surfaces to get the spoons just right. Using a hobby file I have filed away the balsa to reach the composite top skin of the flight surface. (Your model may have foam or nothing instead of the balsa.) again this gives us a little better geometry to control the flight surface. I did mess up one flight surface when I used a dremel for this process, a file is much easier to control.

Here you can see the spoon is in full contact with the top of the flight surface skin, and our linkage pin is parallel to the flight surface hinge. (The servo tray will probably not be square to the opening in the wing, the trays final position is dictated by the spoons orientation to the flight surface hinge. Not the other way around.)

With the pushrod coming from inside the servo pocket, untape the flight surface and see how well the pushrod is clearing the skin (in this picture the top skin) a little file action will gain you some space, do not be afraid to sand away the spline on the pushrod if you are not too worried about the pushrod bending or breaking, I have not heard of anyone breaking one.

Another picture from testing. You can do most of your testing like this, no need to come from the inside of the wing until the very end.

The process for testing the entire assembly is to set up your tray and parts something like this. Making sure you have the correct orientation on all of the parts. It is easy to mess up orientation on these parts.. I did it several times.

Then slide everything in from the servo pocket on the wing starting with the spoon, it passes through the sun trailing edge, and then you guide it into your flight surface. Sorry I do not have a photo, but it is easy to do. (Note, I did not have to modify the trays during the test fitting, but in a future step I do grind some of those spikes down for best fit in my wing. You may need to trim some of these during the testing phase depending on your wing.

 

[Wayne]

So all spoons have been fitted and all is looking good. Lets prep the parts for final install. Here is a picture of the spoons, pushrods and servo arms prepped and ready for final install. Everything has been tested to move smoothly, extra flashing has been removed, this includes making sure the servo arms will not hit the wing skins due to some odd plastic flashing. You can see much of the spline has been sanded away as my pushrods are very close to my wing skins. And finally the spoons 2 halves have been glued together with a bit of thin CA, but don;t get any on the hing pins.

Not shown, it is a good idea to sand a tiny amount on the bottom of the servo tray. We want our glue to have a clean contact. Do not sand too much, the trays are very thin. We will also sand the servo pocket where the tray will be getting glued. Use some sandpaper and sand away, then wipe it out with a clean damp cloth with some warm water and let dry. Yes water.

OK, get your servo tester or use your radio and we are going to set the servo arm position. For flaps servos, we want the linkage "locked" in the full down position. My my install that looks like this:

In this position the gears are protected should the flap take a hit during landing. (Always lift your flaps up right before touching down!)

For my install the neutral position looks like this:

Slip the servo into the tray and install the screws. We are now ready to mount the spoons. We are not going to glue the trays, just the spoons at this time. Slide the trays in and get everything setup. Using files, wood wedges, whatever you like, we want to lock that spoon in the exact correct position. The servo needs to be free to allow us to position the spoon just right, I use a little loose masking tape to keep the servo in the pocket, but still free to move about.

Here is my spoon locked into place, 2 files and a small screwdriver are used to wedge it into place.

The correct positioning for the hinge pin on the spoon is right over the aileron hinge line, but on a flap we want to bring the hinge pin about 2mm towards the servo. This extra 2mm helps keep the flap under control at its much larger throw angles. As this pin moves towards the servo, we are adding extra leverage, but also some mechanical differential and it will place the pushrod closer to the wing skin. So you only want a small amount here.

The trick here is to get both aileron servos as close to the same as possible, and same for both of the flaps. With modern radios we can tune out errors, but still best to be as accurate as you can be. I have see some folks make jigs for this, I eyeballed as I was trying to speed things up, it worked out fine.

I used some black CA to tack these into place. You can also use epoxy if you prefer. Once all were glued I called it a night and left them to cure.

Here are my results:

Waiting for the glue to dry.

Congrats, that was the scary part!! The rest is easy.

 

[Wayne]

The final bit!!

With the servos centered, we can glue the trays in. For the ailerons, nothing tricky, tape the ailerons into their neutral positions (of 5 degrees up if you would like to be more centered for your aileron differential) and then glue the servo tray into position.

A word about glues and servo trays in composite wings. MANY glues will continue to shrink as they cure. This curing can take weeks for some glues, and as the glue shrinks it will deform the skins on your wing! Yuk. For the reason I do not suggest any foam glues, you know the clear glue that slowly cures, but is slightly rubbery. Most all of these will mess with your wing skins in about a month. Avoid medium and thin CA, they are known to do the same. What does this leave? According to 2 very experienced builders this leaves SLOW (thick) CA (no kicker!) and or a good epoxy. Some of the normal 5, 10 or 15 minute epoxies may have bonding issues, so a higher grade than hardware store is a far better option. For me on this build I tried the BSI IC-2000, this is a black medium CA. I had mixed results, one of my wing skins has some small deformation, the others are fine. I thought it was worth a try and had a bottle open. I like the black CA for high stress areas as it is not as brittle a joint. I'll probably use thick CA next time.

The CA loves plastic and carbon fiber, epoxy does not love plastic in the same way. If you use epoxy, you want to get a little over the brim of the servo tray, this way you have captured the tray in the epoxy so the tray can not peel away from the epoxy. You will see the trays have a brim just for this reason. (brim is a thin tapered later that extends past the main part.) Hope that makes sense.

Now for the flaps, setting the flap to a 30 degree angle with the servo in the neutral position will be right around the half travel point of the flap. To this end I made up a little tool. We can offer these on the web site if anyone would like a set. Here is my setup with this tool:

Again put down a lot of tape, especially is using epoxy!! That dang epoxy always seems to make a mess, if I was using epoxy I would have covered everything. I have some metal slugs holding the servo down while the glue cures, again I let this cure over night.

OK - I bet you thought I forgot that the spoons are only tacked in.. Nope. But they should be solid enough that you can cycle the servos and see how things are looking. Don't worry if you need a little more or a little less throw, we can deal with that after the spoons are fully glued in. But if you have some major issue, now is the time to sort that out. All should be smooth if you spent the extra time in fitting.

Ok, lets glue in the spoons forever. This is a good place to use epoxy, get enough into the control surfaces to make contact with both skins. Thick CA can also be used. The thick CA may be easier to control. Both glues may well wick to places you don't want while they are curing. Keep that in mind and down get any glue on your spoon hinge for the flight surface hinge. It can get a little tricky. Optionally you could go for final glue earlier in the build instead of tacking. As I think about it, that is probably what I'll do on my next IDS install.

If you need to adjust travels more than your radio will allow (more or less throw) then you can swap out the servo arms, it is not as bad as you might think. I swapped my flaps to a longer arm as I actually screwed up and ended up with the aileron arms on my flaps. It was pretty easy to do.

From here you can finish off any wing wiring and install your covers and enjoy. For servo covers i like a rubbery glue like E6000 or one of the clear foam glues. This will allow removal should any service be needed.

I then like to wipe the model down with a mix of alcohol and windex. It gently wipes away a fair amount of the finger prints and glue residues, etc. Then maybe a little wax before the first flight.

Hope this helps you all, and by all means if I messed up, please call me out so I can edit these pages.

Thanks

 

[Wayne]

still more? I hope not.