Hello i am a noob and am trying to assemble my first arf ,i am now trying to install the wing and cant determin best way to center in fusalage instructions say slide in and check to be sure is parralel to stabaliser ? (eyeball?) then use a rule to mea.21in from fuselage on both sides of wing 3in.back from leading edgethen mea.from point on stabiliser to point on wing i dont get how this centers wing? I hope im not in the wrong forum
This will cover some of the same ground that Steve did, so read both replies, and I hope I illuminate more than I obscure:
You want the wing and stabilizer to be centered on the fuselage left to right. You want them to be square to the fuselage from side to side, i.e. when the wings are level you want the stab to be level and the fuse to be straight up and down (get this wrong and your plane will lose line tension in either inside or outside maneuvers, depending on which way things are tilted). You also want them to be square to the fuselage from front to back, i.e. if you look straight down at the plane you want the centerline of the wing and the centerline of the stab to line up, and you want both of those centerlines to be perpendicular to the fuselage.
That's a whole lot of stuff to get right all at one time, so you want to spend some time getting it all fit up 'dry' with no glue, then when you're absolutely sure that everything is as correct as humanly possible you want to put it together with some slow-setting glue so you can check, double-check, triple-check, and fiddle as necessary without having to tear everything apart in a panic and clean off the glue before it sets*. Further, you want this dry-fit step to be done so that if you have to weight or clamp anything the weights and/or clamps don't interfere with your measurements -- when you glue, you'll want to clamp it up,
then measure it at least once again to make sure that nothing wiggled during clamping.
Get things a bit crooked and your plane
will fly, but the better you get it the more your plane will be doing what you tell it to instead of volunteering it's own crooks and quirks to the flying process.
So you need to do this when you won't be interrupted, you need to make sure you're not getting flustered or rushing yourself, and you need to have a firm idea of just how long you're going to spend on it before you decided that good enough is good enough and you start mixing epoxy!
I'm going to describe this process as if you were gluing both the wing and the stab at the same time. There's no reason you couldn't do this in two separate sessions -- sometimes I find that it works better to do everything at one go, often I find that it's easier to get everything right on the wing, then move back to the stab.
So:
Center the wing & stab:
Make marks on each one, the same distance out from center, and measure back to the fuselage. In the case of the stab if you can see the center with it in the fuse then mark the stab center and the fuse center, and line up the marks. In the case of the wing I usually like to make marks right where the wing goes through the fuse, and line those up with the fuse edges.
Level the wing & stab:
Steve uses a reference to a building table. I like using a machinist's level to make sure that my table is level, then I hold the fuselage at 90 degrees to the table the way Steve does, then I use the level to find the tilt of the wings and stab -- his "measure to the table" method works great, too, so this is a matter of preference. In either case you should be making sure that the wings & stab fit into their respective slots in a way that holds them level, or that you can block them up to level without knocking the fuselage sides out of square with the table. Ideally you'll do this in a way that lets you take everything apart to apply glue, then put it all back together and get things level and plumb quickly and without fuss -- this is the "fussing and fiddling" that I was talking about, and you want to do it
before you mix any epoxy.
Don't mix any epoxy yet.
Square the wing & stab:
Remember geometry? The idea behind squaring the stab and wing with the fuse longitudinally is that if you have two triangles with sides that are all the same length, then they must be identical. If those triangles are made with a couple of lines in common -- like a center line on a wing and the fuselage -- then if they're identical then they'll have to be right triangles. So you establish a centerline on the wing and the stab, by choosing identical points at each one -- the stab is easy, because you can use the corner of the hingeline and the stab tip. The wing may be a bit harder, but you can choose the back of the wing tip if it's distinct enough, or the intersection of the spar and one of the ribs, etc.
Now for the stab you just choose a point on the fuselage, say the front tip, and measure back to each point on the stab. I use a tape measure, not a string, but the idea is the same: you measure, you fiddle the stab into place, you measure again. The nice thing about a tape measure is that you can remember the measurement, then when you go to glue for real you can just set that measurement on one side and the other side should be right.
Do the same for the wing, except you probably want to use the back tip of the fuselage (to give you a good long distance to measure).
When you are sure that you can assemble everything and get it to come out right, then mix up some glue (I use 30 minute epoxy, but feel free to use something slower). Have everything set up, then glue your joints, then check everything again. Keep going around checking all of your measurements (centered, level, square) until each one shows as being on the money without you having to touch anything. If you have to clamp or weight anything, make sure you do all the checks
after clamping and weighting, to make sure that the clamping process hasn't disturbed anything.
Once you've gotten everything done as best as you can, go outside and do something completely mindless for a while, to relieve tension. Don't even go back into your shop until the next day. Come back when the glue is dry, and don't measure anything unless you're prepared to rip the plane apart and re do it!!
* And of course, in almost 40 years of modeling I've never,
ever had to do that!
Topic: tower hobbies pt-19 cl (Read 3893 times)