MaJ. Woody

My Feedback: (28)

I would hate to eyeball it. Currently I have the servo arm centered and the push rod connected between the stab and the servo. I need the neutral position of the stab so I can mark the hole locations and bolt the servo down. If I eyeball it and get it wrong then I will have to make that adjustment with trim and then my servo arm will no longer be centered. I cant adjust the length of the push rod too much since it is a fixed length with a threaded end that will only handle a small amount of change.

MaJ. Woody

My Feedback: (28)

Well I moved on and settled for 3/4" below the panel line on the fuse. This gives me some up elevator in the neutral position. I will post all the build notes and pictures right after dinner.

Countryboy

My Feedback: (25)

Dom,

I don't know for sure where elevator neutral will end up on yours, but I had originally put in a couple degrees of negative incidence on my JL F-4 stab and ended up having to use quite a bit of down trim for level flight. In order to keep the elevator trim at neutral, I readjusted the stab and put an incidence meter on the wings to zero them. I then checked the stab with the incidence meter after readjusting and found that it is also at zero. Really surprised that it worked out that way as I would have thought it would have taken some negative for neutral. On the other side of the coin, I would rather have one out of trim and climbing rather than out of trim and diving. Keep in mind that neutral may vary according to where you have the turbine thrust line set also.

MaJ. Woody

My Feedback: (28)

Very interesting. Thanks for the info. I'm with you...rather be climbing than diving. I'll show you where mine is set in a minute. You would think they would put this important piece of info into the "instructions".

MaJ. Woody

My Feedback: (28)

The plate for the stabilizer pivots and the plate for the elevator servos are removable. Here is what it under them.

MaJ. Woody

My Feedback: (28)

All looked good under there. Lots of carbon and the bulkheads were all well glued. I did snug up the bolts on the fin clamp...they were not loose but not tight either.

MaJ. Woody

My Feedback: (28)

I made a change from the removable plates. I feel much better about a solidly glued structure when it comes to my full flying stab and elevator servos. I'm sure it works fine as is but that setup is not for me. The stab pivots were bolted to the plate with socket cap screws and stop nuts. Since my plate will be both bolted and epoxied into position, I installed 6/32 blind nuts to mount the pivots.

MaJ. Woody

My Feedback: (28)

Here is the fit you get when trying to bolt down the pivot plate. The problem is that the tongue needs to be angled properly to be in line with the notch front bulkhead.

MaJ. Woody

My Feedback: (28)

Since I will be using the bolts and epoxy, I decided not to bevel the tongue. That would only weaken the structure. I will let the epoxy take care of things. I needed to fashion a dam to keep the epoxy from flowing out of the joint. I used some scrap ply for this and CA'd it into place.

MaJ. Woody

My Feedback: (28)

Next I mixed up some 30 min epoxy and spread it all over the tongue, front notch and the pivot plate. Now bolt down the plate. I used CA on the bolt threads.

MaJ. Woody

My Feedback: (28)

After bolting the plate in place, I ran a bead of epoxy around the joints using my heat gun to get it flowing in all the gaps. When this all dried, the result is one rock solid platform that I can trust while doing a 199.99999 mph fly by. I have seen flexing in plates that were just bolted in. Not on this F-4!! I then bolted the pivots to the plate with 6/32 socket head screws and washers. I used loctite on all bolts.

MaJ. Woody

My Feedback: (28)

I bolted the stab in place with 8/32 socket head screws and stop nuts. I used loctite on all bolts. The stab is sandwiched between the pivots and the control horns. Since I will be using one servo for the stab, I needed to be able to pass a bolt through the control horns without threading it. To accomplish this, I needed to open up the holes slightly to remove the threads. Using a mic and number drill bits it was easy to get a precise fit.

MaJ. Woody

My Feedback: (28)

I studied how I was going to set up the push rod for a long time before going in this direction. I originally was going to space the ball link between the control horns but you will see why I changed my mind.

MaJ. Woody

My Feedback: (28)

So lets look at my linkage. First I swapped out the SM push rod for the FeiBao push rod. It is hard to tell from the photo but the FeiBao units is much larger and robust!

MaJ. Woody

My Feedback: (28)

Now you will see why I needed to open up the holes in the control horn to pass the bolt VS. just screwing it through. You will also see why I elected to offset my linkage rather than center it.

I was originally planning on using a Dubro Monster ball link. As you know this has a 4-40 bolt pass through it's center. This results in a slight amount of play when you pull and push on the linkage. SM supplies a beautiful aluminum link that has a ball bearing in it. By using a longer bolt that has a shoulder on it it is possible to create a linkage with no slop. If I centered the linkage it would be resting on the threaded section (I actually did this first and had a stop nut on each side to keep the link from shifting) and it too would have a similar amount of slop as the Dubro. But by pushing the linkage over the shoulder of the bolt you get a fit that is so precise and has ZERO slop! Adding a washer and tightening up a stop nut all the way to the shoulder of the bolt left about 2-3 thousands clearance for the linkage to float side to side. The fit it just incredible. On the other side I added a stop nut inside and out. Not only is the linkage fully captured on the opposite end but on this side by using a nut inside and out you will not compress the control horns together as you tighten things down I used locktite of course.

MaJ. Woody

My Feedback: (28)

I forgot to take picture of this next step but next you will bolt the servo to the brackets and then connect up your linkage to the servo. Be sure the servo arm is 90 degrees to the servo. With the servo neutral (I had the radio on for this entire step to keep the servo centered) and the arm at 90 degrees, put the stab in its neutral position (you see why I was asking for that measurement earlier). I went 3/4" below the panel line for my stab neutral point. Next use some Ca on the aluminum, servo brackets to tack then in place on the plate. Presto this is where you will drill the holes for permanently mount the servo to the plate.

MaJ. Woody

My Feedback: (28)

Remove the servo from the brackets. They will stay in place with the CA you applied. Because I will be gluing the plate in place I used 4-40 blind nuts and socket cap screws to hold the brackets in place.

MaJ. Woody

My Feedback: (28)

This will be my first experience with using a single servo on the stab. On my other F-4's I have used two 200 ounce servos. This results in more weight and not necessarily more reliability. In fact if you don't dial them in just right the servos may actually fight each other causing all sorts of problems. So this is a much simpler, lighter install. The servo is a Futaba S9157. This baby puts out 425 ounces of torque @ 6V!!. I bolted this to the brackets with socket cap screws. I used CA on the threads and even topped the upper bolts with stop nuts fro extra security. Never use loctite near any plastic. It will make it brittle and will crack in a matter of hours. The bracket was then bolted to the plate using loctite.

MaJ. Woody

My Feedback: (28)

Next I drilled a hole in the plate to pass the rudder servo wire.

MaJ. Woody

My Feedback: (28)

The servo plate is then glued and bolted in place just like you did for the pivot plate.

The push rod has loctite on both sides. Connect everything up. Don't forget the keeper on your clevis. I set the travel to 2" up and 2" down. that about 50mm as indicated in the manual.

MaJ. Woody

My Feedback: (28)

Next I bolted on the fin. I used a lock washer, washer and loctite on the bolt for the retaining clamp.

MaJ. Woody

My Feedback: (28)

Here is where I "Guessed" the neutral position of the stab. I still needed to work under the tail to run the servo wires, install the tail hook (I am debating making that operational VS just gluing it on) and install the pipe. When that is done I will button up the tail section using the cover and adding the scale pivot details.

MaJ. Woody

My Feedback: (28)

That's it for tonight. I will get more building done tomorrow if the weather is bad. But if it is nice, I'll be flying my Cessna.................

MaJ. Woody

My Feedback: (28)

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MaJ. Woody

My Feedback: (28)

Next I will apply BVM Ceramic Blanket and Aluminum tape (the high temp tape not the cheap stuff) to the complete perimeter of the fuse in the are of the turbine pipe junction. To me this is very critical and often overlooked by a lot of builders. Imaging your at Jets Over KY...the best event in the world...and you are waiting to take off. Taxi tank is on and your waiting for your turn at the runway. All the while there is no air moving through or over the fuse to keep things cool. Blistering paint, loose bulkheads and worse are the result. That does not happen if you properly insulate the area. This is a tedious job that will take time.