Wing Assembly on Table

[sjt]

(bearhawk patrol)

It was mentioned once before on the forum, but I did not understand at the time. This may be model specific. I am working on the Patrol.
I thought that building on a table would be similar to builing in a wing stand. I have seen plumb bobs used between attach plate holes when wings are assembled completely in a wing stand.

In the case of assembling on a table - the attach point holes are not meant to line up.
The main and rear spars are parallel. The main spar will be on table surface. The rear spar is to be maintained parallel but has freedom to be moved up off of the table.
There are only two choices for the vertical distance. You could make the attach holes concentric. Or, you could choose the height to have the cord line parallel with the table.

Either the cord line or a line thru the attach holes could be made parallel with the table. The two possible choices are not parallel.

The dashed line in the drawing is the cord line for the wing section (there is no holes in attach plates they are drawn to make locating the wing cord between spars

[svyolo]

I think either would work, but I think a stand is probably better, both structrually, and ease of use. Structurally the weight of the table is fighting the structure in the direction that the structure is weakest, making the structure more likely to deform an unacceptable amount. Ease of use, you can stand or bend and access both sides of the wing if you use a stand. If you use a table, you only have access to one side.

[sjt]

(bearhawk patrol )
When I started I had assumed the attach holes would line up. That is the general result from using a plumb bob.

When assembled on a table I can force both spars to be parallel. I have only one free choice. I can choose the blocks of wood under the rear spar.

My choice of blocks might be different then someone else. I used about 1.33 inches of blocks - I have not settled on that number.

I mocked up the two spars in solidworks and guessed the number to be about 1.33. If I then run a mathematical plumb bob (sharpened drill rod) I can see it misses the attach hole by about 0.5 inches. Upon reflection it had to be off by 0.5 since a line between the attach holes, and a the cord line are not parallel. They are not parallel by 0.5 inches over the distance of 32 inches between spars.

If I go to the garage and mock it up I find that the attach point holes are not concentric. The point of intersection with my mock up is about 1/2 inch away from attach hole. My numbers might be completely wrong but I would have to shove a lot of spacers under the rear spar to raise it up to intersect the attach hole.

My table is level, and my drill rod is level.

I only thought they would line up. The real relation is completely due to the geometry of the wing foil.

[sjt]

One picture is a drill rod through the main spar attach hole. The spar is square to the table.
I found that the distance from the table was 2 calibrated 2x4 and another chunck of wood and a 3/16 lathe bit.

I used the same set up on the sharpened drill rod side.



The other picture is a level on the drill rod and a level on the table.

Referencing a picture from the previous post, I think 1.33 is about the number required to force wing cord to be level with the table also. That would not be suprising because the 1.33 number is the difference from the wing cord to master wing foil template distance.
{2.7 = 1.37 +1.33}
{masterspar/cord = rearspar/cord +1.33}

[svyolo]

My kit wings and fuselage attach points were really close. Concentric. not perfect, but very very close.

[sjt]

Drawing 4 - master rib on the patrol:

I use the line bob calls "center line" as a reference. The spars are 32 inches apart. I am relatively sure that the center line is at right angles to both spars.
The distance I measure on my drawing from the projected location of a concentric main attach to the rear spar is about 0.5 inches away from the rear spar attach.

If I call what bob labels as the center line the "wing cord", that would mean that if the fuselage attach holes were level the wing cord would be about 0.9 degrees down. ((0.5) / 32)
I have not built the fuselage. If I had to guess the fuselage attach locations are angled 3 degrees up.

If all that was so, then my wings would eventually be about 2.1 degrees up from the datum line. Bob's drawing specs 2 degrees.


If anyone could confirm that the fuselage attach location (relative to the datum) is about 3 degrees I would appreciate it.

[jaredyates]

Hey stinger , is this the same thing you were running into?

[stinger]

Yes, I have been preaching For over three years now but don't seem to get it through . The booklet is depicting a four place or old Patrol wing. I don't know if the Patrol or the LSA always had a Riblett wing or not. I do know that I started building my wing according the the booklet it was Not looking correct. I had seen many pictures showing the plumb bob string dropping dead center at the spar attach points. I started over and went by the Mylar sheet. My wings aligned correctly and angle of incidence was correct.One might and I suspect some have built the wing by the booklet I was once told it would fly fine I am not so sure. My fuselage spar attach brackets were positioned as per plans.My plane is quite fast for only having 100hp. Riblett wing. Stinger

[Chewie]

No stinger, your advice got through, at least to me. There are several threads on this topic. I plan to frame up per the mylar.

[sbmurphey]

So I am going at this from the other direction with the LSA. I have welded my fuselage and have a set of factory wings I need to mount. According to my measurements, I have a 1.5 inch drop compared to center line on the fuselage over my specified 31" spacing. This would yield a 2.77 deg angle of incidence on my fuselage. Looking at the spar mounts per plans, and it look very close to the same on the actual wing, which is offset 3/8" from the cord line creating a negative .69 deg. angle of incidence. Once mounted, they will cancel each other out and I should end up at 2.08 deg.

I am expecting my bolts to be out of alignment by aprox. "half" of the 3/8" of an inch the wing attach fittings are offset from the cord line. With a little rounding, it works out to be aprox. 1/4 deg. off on average of the two bores.

SJT: Thanks for the post. I have been fretting over the welding of my attach fittings and needed this exercise to firm up what I needed to do.

Thanks,
Stephen

[stinger]

Jared, sorry I left out picture that worked for me. Stinger 2016-08-21 2016-11-03 001 003.JPG2016-08-21 2016-11-03 001 003.JPG

[sjt]

i think that these are the two choices, a block of wood , or an offset plumb bobTABLETOP.jpg

[sjt]

I am building on a table with a block of wood, for my mylar patrol wing I would have used a 1/2 inch offset.
The line bob labels as the center line is parallel with a table, or is vertical with a plumb bob.

Unfortunately, there is no marking on a completed spar to indicate off of.

If I was clever I would have made a rivet hole at the location where the center line intersects the spars. And then If I was even more clever I
would not have filled it with a rivet when I was doing all the others.

I could have used it as a vertical reference if I had chosen that approach.

offset.jpgPLUMB.jpg

[sjt]

One last thing,
can anyone confirm that I am to use AD3 rivets at the main and rear spar at the location shown in pic
AD4 are clearly called out going into spar, and as far as I can tell AD3 are called out going into rib.
image_7832.jpgimage_7833.jpg

[geraldmorrissey]

On the Patrol the -4's are common to the attach angles and the upr & lwr capstrips on the main spar. -3 c/t the attach angles and the spar webs. -3 c/t attach angles and rib webs. -3 c/t attach angle and upr & lwr rear spar capstrips.
Gerry
Patrol #30

[sjt]

Gerry,
If you have attached the wing, I have a question. Can you confirm that -when you drill out the attach holes to the final size - the goal is to make the Main and rear attach locations concentric. From the above drawings, I am pretty sure that they are not concetric -by design-, when first made , hence they need to be made undersize at first.

Later, when it is time to attach the wing to the fuselage, some effort is made to "file", "drill", "ream" the hole all the while making it larger and hopefully somewhat concentric with each other.

My thinking is that the spar sets the dihedral. Also the spars will be drilled to make the dihedral match for both wings.
But, for the spar to be used to set the dihedral the attach holes have to be concetric to pivot about.

The attach holes on the fuselage are concentric, and after some monkeying around - the wings attach holes can be made somewhat concentric. The end result is that the attach holes will no longer be square with the attach plate. The hole is distorted in the necessary direction to line up.


When building on table, I do not have gravity to use as a reference. I had to lay out a grid on my table. I marked a 32 inch by 172 3/4 rectangle using a tape measure and the pythagorean equation.

I then line up the main spar along the long end, and the attach holes along the short end.

Using a square to line up the attach hole with the rectangular box I drew on table.
f.jpgr.jpg



The last picture is a drill rod that is square and concentric with the attach hole in the main spar. Consitent with the above calculations. it ends up being
a half inch above the rear attach hole. I made the holes undersize, and plan on enlarging them - trying to make them concetric with each other -
later when it is time to hang wing on fuselage.

d.jpg

[sjt]

This is my double check that the 1.34 inch blocks of wood supporting the rear spar are correct. I confirmed that the my ribs are square with spar.

I originally made all of my rib blanks (32 - 0.032) long. All of the rib blanks can be made to have parallel edges with this length. Only on final assembly are the notches sanded out. I found that the rib blanks are square with the main and rear spar. The edge that I left as a reference edge is still useful for spacing the spar centers 32 inches apart.

a.jpg
b.jpg