Aircraft alignment when building

[mlachow]

Anyone have any creative tools for aligning large sailplanes when building? Doing the wing mount is always fun.

I have a real fun one coming up soon. How to align the Jastrzab. It has a double challenge. It is a gull wing and the center panel sweeps forward. One nice feature is the tip LE's are pretty close to straight. Or maybe that is a curse since it will show misalignment more easily. Add to that a really wide wing chord, even mid-panel at the gull break. Can't put a standard robart incidence meter out there since it is too wide for those. Has anyone ceiling mounted a 3D laser?

[SMYK]

FatMAX from Stanley ( Home Depot ) and reference stick
First you do the table then your glider all around
I use it for everything : floors , walls, CNC machines
simple and fairly accurate
Make the elevation points on the crucial surfaces and edges like on the real glider.
They all real ones do have this point mandatory If I find pictures I will post
you probably might use the TI 30 calculator to get the angles right.
better then using incidence meters on local spots.
laser level makes plans global
I remember someone was doing this with big glider on RC group not far ego.
You still have to fly your plane and correct it accordingly Not everything is symmetrical. It is good to have option to correct root wing pins in case not symmetrical incidence crawls in between wings

Mike

[ARUP]

On all of my builds, of which the plans are from my own hands, I create reversible jigs for model component fitment and assembly. One component, say a fuselage, gets attached to the building board then the jigs are secured so as to attach wings or whatnot. Each is a custom fabrication just like the model being constructed! This is usually a tedious but necessary task.

[mlachow]

When I built the wings, I was able to set he dihedral angle in the joiner box since it is a straight joiner. I was also able to get it square to the root ribs and spaced equally between panels for the alignment pin. The joiner is rectagnular and it is not a round rod. The joiner boxes on the outside are not exact sizes and the square holes in the wing ribs and fuselage root ribs and support ribs are cut oversize. Plenty of wiggle room. It all slides together just fine. There is enough wiggle room in the joiner box to help align things.

[SMYK]

joiner box or joiner alone doesn't need to be attached to the fuselage. Actually spar never is, only pivot points and (front and rear) pins are. This is described as a floating spar. Spar takes bending stress only and needs to float up and down. Fuselages in real gliders have a hole in fuse for a spar. The only known model kit with properly executed floating wing joiner was Multiplex ASH 26.
By the way Michael, did you look at the spar joiner in real jastrzab on these vintage pictures? Massive. How it compares to carbon wing joiner

[Tom]

Can't put a standard robart incidence meter out there since it is too wide for those.

Make a incidence meter out of wood that fits your wing that the Robart meter head sits on.....done it a bunch of times.

[mlachow]

I did one better than a wood bar for the meter. I laminated two 3mm x 0.5mm strips of carbon to a pine strip. Fits really nice.

[mlachow]

OK, green cross laser set up from the ceiling. This draws a line down the centerline of the fuselage (and to the bottom keel where that is visible) and also draws a line on the wing panels just behind the LE balsa. You can also see it light up the fin LE. There is a second tripod mounted horizontal laser to the front of the model. You can see the red crossing the LE of the wing.

So if the LE crosses about the same place and I can measure down to the beam at the tips about the same while the fuselage line is vertical up the fin and down the centerline, that is good. If the cross line from the top matches where it traverses the left and right wing panels, then the wing should be good that way. Since it is a 3021ish airfoil, essentially flat bottom. I can attach two long carbon rods to the left and right wing panels the same distance out. Those two rods should also be parallel so the wing angle matches that way.

The ceiling laser is a cheap one from Amazon and it includes a remote control so you can turn the beams on and off when you need to tweak the model. The mount for the laser includes an adjuster to level it to the point where the self leveling works. It also rotates. Between that and moving things on the bench it is not too hard to align.

The beam on the green one is almost 3mm wide. Matches the ply in the model pretty well. The red one is an old Ryobi I had and it has a finer line. But not as bright.

The only thing I found in my building was the front of the nose got twisted a little from the back of the cockpit to the front. Probably when I did the first pieces of sheeting. The bottom of the fuselage is straight.

[mlachow]

The red laser is not self leveling. It has two small levels. When I compare it to how things are visually, it is not good enough. Maybe if it was self leveling, it would be better. It is probably at least 15 years old.

I measured two marks per panel. One just before the mid wing break and the other about 6 inches from the tip. I put a T pin in the tip ones. The green laser has a horizontal beam too. I can measure down with a wood ruler. It's not any closer than maybe 3-4mm but in a 4M wing, I think that is good. I was also able to compare the two vertical beams lining up the LE and the fuselage centerline by measuring from the tip pins to the top of the fin and the center of the fuselage just in front of the stab.