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Old 04-11-2017, 01:58 PM   #1
cwilliamrose
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Default Final Assembly -- What Comes First?

I thought I'd start a new thread on this subject since we have at least three airplanes in final assembly right now. Two of those, a Skybolt and an Eagle, are being assembled a little differently than what I have done in the past. The other, an AS2, seems to be being done as I normally did it.

When I was ready for final assembly the wings were completely assembled with ailerons and the wires attached. The fuselage was also completely assembled with all the panels attached, the tail feathers installed and rigged. I also fully install the engine and prop and leave it as it was for last test run. The wings had already been on the airplane and fully rigged with any rigging washers noted and the wires loosened X-number of turns from their fully tensioned positions.

The reason for doing this is that I am lazy. Very lazy actually. I don't want to have to install ailerons after the wings are on the airplane, it's easier to do that with each wing resting on a workbench or saw horses. I can flip the wing upside down or stand it vertically as the need arises. Installing the wires to the wings is easier when the wings are off the airplane and for the same reasons. Once you get ready to hang the wings installing the two mounting bolts and the wire attach clevis pins at the fuselage gets your wing in place quickly and with minimum aggravation. The ailerons, having been previously rigged, just need to be attached to the torque tube and slave struts.

Assembling the fuselage to completion is much easier without the wings being in the way. I always had the fuselage assembled and basically ready to fly when I hung the wings on for the last time. You also put the wing fabric in less jeopardy if all you're doing is sticking the wings on and installing fairings. No need to be dealing with fuselage panels, canopies, etc when all that stuff could be done before the wings are installed.

There are about 100 ways to do this final assembly step and there are many reasons why someone might chose a different approach (like having a three-piece top wing) but from my experience things go much smoother when the sub-assemblies are as complete as possible. I have always done the build off-airport which is one reason to deal with complete sub-assemblies -- it makes transport easier because there are fewer loose parts to deal with.

The sequence of events for an S-1 or S-2 Pitts/Eagle goes something like;

1) Attach the top wing to the cabanes (2 bolts). No scaffolding required, just have someone steady the upper wing until step 2 is complete.
2) Attach the flying wires to the fuselage (4 clevis pins). The top wing now has a limited range of motion.
3) Attach the I-struts to the top wing (4 bolts total w/washers left slightly loose).
4) Attach the lower wing (4 bolts total).
5) Attach the landing wires to the upper wing fittings (4 clevis pins total).
6) Attach the I-struts to the lower wings (4 bolts total w/washers left slightly loose).
7) Snug up all the wires to their previously tensioned positions. Snug up the I-strut bolts.
8) Install the slave struts (previously rigged).
9) Connect the pitot and static lines plus any wiring, fuel lines, etc. If you have upper wing fuel/smoke lines or wiring it might be easier to deal with that stuff before the lower wings are in place.
10) Check the wing rigging. No need to level the airplane for this step as it was already done, you're just looking at tip incidence, the top wing's flatness, confirming wire tensions and checking that the clevis forks have full wire engagement.
11) Check the aileron rigging and confirm there are no clearance issues at full travel.
12) Install fairings and javelins -- both previously fitted and finished.

Notice no fabricating, fitting, painting, etc. All that is already done. After completing step 12 there's not much holding you back from the first flight.


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Old 04-11-2017, 02:12 PM   #2
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That's what I had with my project (flying plane). It was already done so hanging hte wings was a non event. But I didn't think of it of course, that's the way it worked out for me!


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Old 04-11-2017, 03:10 PM   #3
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I actually was planning on installing the engine before the wings, even though the Eagle manual doesn't recommend it. It says that the engine is heavy enough to make the fuselage only tip over forward. I haven't found that to be the case. Plus, I'm lazy too and I didn't want to have to walk around the wings any more than I had to during final assembly.

Anyway, my dad wanted to come down and help a couple weekends ago, so we did what I couldn't do by myself and we put the wings on. I did attach the ailerons prior to installing the wings. I hadn't tried that before on my old ASII, but it is much easier to do that with the wings laying on saw horses, upside down. I did install the wires after we stuck the top wing on. The clevises were still on the fuse and the wing, except for the upper fuselage clevises. The wing and lower fuselage clevises are not easily removable.

But, like you said...many, many different ways to do this. None of them right, none of them wrong, but no matter how we do it, there's probably a better way. All part of the learning experience.
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Old 04-11-2017, 03:29 PM   #4
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Quote:
Originally Posted by Cameron View Post
I did install the wires after we stuck the top wing on. The clevises were still on the fuse and the wing, except for the upper fuselage clevises. The wing and lower fuselage clevises are not easily removable.

But, like you said...many, many different ways to do this. None of them right, none of them wrong, but no matter how we do it, there's probably a better way. All part of the learning experience.
On the Eagle, there are clevis's inside the wing that would be a real trick to remove and re-install and the lower ones on the fuselage are impossible to remove with the landing gear installed. So the ones on the top wing are removable, but I ended up just putting those on the wing first and threading wires in once the wings were on the plane. A little tricky to get them started, but not too bad, but this eliminates any possibility of counting the turns from a previously rigged position. My Skybolt was easier as it had the external attachments, 3 turns and every clevis came out.
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Old 04-11-2017, 06:29 PM   #5
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I don't know about lazy as much as minimalist. When you have put as many planes together as you have, distilled lists are great. First timers, not enough sweat equity in it; has to come apart at least once to pay dues. I figured first and last steps would have been, Sit in cockpit and make airplane noises.
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Old 04-11-2017, 09:26 PM   #6
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Thinking back to a conversation I had with Kevin Kimball a few days ago I think you could still count turns on an Eagle final assembly. Once you fully rig the airplane you can count turns on the landing wires during disassembly. If the top wing was dead straight and you count the turns on one set of wires you can return to airplane to that same state of rig by returning the counted wires to their tensioned position and tightening the other wires until the upper wing was flat again. I'd add tension a little at a time to both sets of wires but always leading with the landing wires until I matched my count, then do the last few turns on the flying wires to flatten the upper wing.

The above is not something I have ever done but I see no reason why it wouldn't work. I don't remember how we did the one Eagle I was involved in during final assembly.

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Here's the only photo I have of the Eagle being assembled. Not sure why the panels were removed from the fuselage but I was just over for the weekend to help with the assembly so I may have been doing the first full rigging from scratch -- I just don't recall after all these years.

I'm taking the wing stands off in preparation for attaching the I-struts. There's still time to put those panels back on before we install the lower wings.
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Old 04-12-2017, 01:11 AM   #7
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CWilliam, inquiring minds want to know. Will those jeans fit around one thigh now?
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Old 04-12-2017, 12:40 PM   #8
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I have bird legs so that would not be the issue. Those are 33" or, more likely, 34" waist and I'm currently wearing 36" (down from 38"). That means it's unlikely I'll ever get in something that size again. I still have some 34" jeans in the closet but I think Goodwill is a better place for them........

Thanks for asking.


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