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Whats the best way to realign vertical fin

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Old 06-19-2003, 01:06 PM
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Default Whats the best way to realign vertical fin

We have recently diagnosed the problem with my Eagle 63 Trainer (that hooks right on takeoff) to being a misaligned vertical fin. It is noticably cocked to the right. Should I use a dremmel tool and cut it off at the fuselage and then CA?

I have it CA'ed and epoxyed on. Is there some product that dissolves those glues?

How would you approach this problem?
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Old 06-19-2003, 01:29 PM
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bearmech
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Default Whats the best way to realign vertical fin

I noticed that in the other thread that it flew fine before. Was this before the flight fence, in other words what caused it to be off in the first place? Just curious. You can cut it off flush with the fuselage with a razor saw, mark the center line on the fuselage then drill a small holes (3 or 4 should do it) on the center line and insert round tooth picks and then align the vertical stab on the tooth picks to mark the location for matching holes to be drilled on the stab. Drill the stab and cut the tooth picks to the length you want. Dry fit everything then epoxy in place and add fillets at the joint for extra strength. I hope this explanation make sense, It's easier to do it than explain it. LOL
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Old 06-19-2003, 02:30 PM
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Default vertical fin

I believe this was the problem all along and it was made worse with the repairs when I hit the safety fence as I needed to reglue the vertical stab and redo some monokote. It flew OK but need way too much rudder and aileron trim to fly straight. A long time ago I flipped the Eagle and snapped off the vertical fin and reglued it. I suspect I did not get it straight then ...

thanks for the advise.
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Old 06-19-2003, 02:41 PM
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Default Whats the best way to realign vertical fin

You might also PM Minnflyer here on RCU to see what he suggests. He's always got good advise.
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Old 06-19-2003, 04:33 PM
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Default Whats the best way to realign vertical fin

The suggestion by 'bearmech' is very good. That combination of toothpicks and fillet should be more than adequate.

I start by temporarily securing the fin and rudder 'in alignment' with a piece of balsa near the top using clothes pins or whatever. The important thing is that the two parts are exactly in line (in one 'plane' so that your eyes are not mislead when viewing from the front of the plane).

To align my fin/rudder I generally place a few pieces of masking tape across the top of the fuselage and mark the center of the fuselage (I assume the fuselage is straight). Then you can place something on those marks to stick up if you like (maybe building pins). Then I stand in front of the plane and using one eye I sight along those marks or protruding pins. Then I glance at the rudder and make a rough adjustment to the fin/rudder. I then realign my eye with the center of the fuselage and then move my head to the left XX inches and note the amount of fin/rudder I see. Then I go to the middle of the fuselage again and then move my head the same XX inches to the right. I look for the same amount of fin/rudder to be visible on each side of center. Then I make any small adjustment and sight again. Once I am satisfied I try to mark the fuselage so that I can return the fin/rudder to that same position if I remove the assembly. I then remove the fin/rudder.

When replacing it you will have to make sure the items are vertical and straight forward. So you have two concerns. If possible you can make a 'jig' that rests on the top of the fuselage that has a slot cut in it to slide over the front bottom edge of the fin and one for the rear bottom. The rear bottom jig can be made stationary with tape. The front jig is moved until you align the fin/rudder. Then tape the front jig in place. The idea is to be able to remove the fin, apply adhesive then return to fin to the same place where it is aligned properly.

To make sure it is vertical you can use three building pins. Place one in the very top of the fin. Place another at the left side tip of the horizontal stabilizer and the other on the right side tip of the horizontal stabilizer. Tie heavy thread or dental floss to the top pin in the rudder such that there are two ends left dangling that reach past the horizontal stabilizer tips. Apply adhesive to the fin that will give you a few minutes of adjusting time. Place the fin on the fuselage. Pull the loose thread ends to the tips of the stab and wrap the thread around the pins to keep the fin upright and perfectly vertical. You can hot stuff the thread rather than 'tie' it at the ends of the horizontal stab.

The idea is that the 'blocks' return the alignment down the center of the fuselage and the thread is used to make the fin/rudder vertical. The adhesive should now be allowed to set completely. Then remove the fixtures and install any further fillet material to strengthen the already aligned structure.

Remember that if you had made throw adjustments to compensate for the previous misaligned surfaces you must now change the linkage to allow the rudder to be in line with the fin.

Also, if you find that straightening the fin/rudder did not seem to make a difference in the air then start looking into your engine thrust as the next possible source of concern or maybe the wings are not 90 degrees to the center line of the fuselage.

If you still have the center line markers you can check the alignment of the engine and the wing to one point on the center line of the fuselage near the fin using the dental floss (something that does not stretch). If you use the tip of the prop make sure you use the same tip one both sides in case the prop tips are not in line with each other. If the prop is good then you can use one tip on one side of the plane and the other tip for the other side of the plane. The distance from prop tip to center line point near the tail should be the same on both sides. You can secure the dental floss on the center line with tape while you move the floss to the prop tips. If you want any sidethrust then compensate accordingly. Test the wing in the same manner. Test the distance from the trailing edge of the wingtips to the centerline point near the tail. Adjust the wing accordingly.
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Old 06-19-2003, 05:04 PM
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Default Whats the best way to realign vertical fin

Scrap it and get a new one
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