Rivet Spacing on Ribs

[iKilo]

First time builder here...I've managed to get the mylar drawing converted into a form block out of 1" MDF and I would like to mark out where the rivets would be. I've marked out the main spar and the rear spar and have gone with the 1.5in spacing as called for in dwg #3.

The thing I'm seeing though is the the rivets don't line up the way they should at the rear spar... I'm assuming the "BASIC 1 1/2 SPACING" comment means we don't have to space exactly at 1.5in? Not sure how to proceed here...

Rivet locations on Main Wingform_scale.jpg

I've tried searching the forums for answers but I may have missed something as I couldn't find an answer.

Appreciate any help/advice you folks can give.

[sjt]

r1.jpg r2.jpg
On a patrol from the center of the main spar to the center of the rear spar is 32 1/4 (using a flexible 4 foot ruler)




temp.jpg

[sjt]

We do not actually use all those decimal points

for example the patrol drawing for cap strip is 1.021

What Bob is saying is between ribs centers of 12.25 inches he wants 12 rivets yielding 1.021 rivet spacing (patrol only)
For a lot of places using a rivet fan and only knowing that 23 rivets yield 22 spaces over a distance of 32.25 inches allows for a quick rivet to rivet distance.

I did not own a rivet fan and use a flexible 4 foot ruler.



I wanted to show in the above drawing the reference point of the center of the main and rear spar as starting and ending points

[sjt]

rp1.jpg
I did not own a rivet fan back then - and the rivet fan I now have has 20 holes
I would have pinned the first hole in the center of the main spar web flange

rp2.jpg

[SpruceForest]

1.5" is the target/desired spacing. Going to a smaller spacing adds a little weight and may create issues with riveting close to a flute, while going beyond 1.5" ON A CONSISTENT BASIS runs the risk of exceeding designer's desired/anticipated rivet/skin bearing loads on that part of the structure. The other thing to realize is that the only reason we go through this exercise on the wing ribs is that we need to avoid putting flutes where we need rivets, so having the nose, center, tip, and other forms marked for flute versus rivet gets to be a manufacturing issue. On the ailerons and flaps, we either use a rivet fan (fast and easy - handles both spacing and alignment) or an HP-32SII and a rule (the rule is optional; the HP is essential ) and keep the spacing at or under stated spec...adding an additional rivet to a line on those components is not even an appearance issue, as the metal structure is buried in fabric.

I would not get bound up with something like a single 1.55"/1.45" rivet spacing on a line (because I failed to trim off the free corner of a stiffener that now going to be in the way of my bucking bar); a single small variance along a line of rivets is accounted for in both materials properties and design practice. My personal standard is pretty much in line with older slide rule practice as an engineer... try to keep things within that 10% engineering error bar, don't ever exceed a stated 'not to exceed' value (spacing, loads, etc.), and get a second opinion (i.e., call Bob) when any contemplated variance sets off my spidey sense.

[iKilo]

Thanks for the responses! I believe I understand now...

The distance between the front spart (center of flange) to the rear spar (center of flange) should be 31.75" for the 4-place. At 1.5in spacing between rivets, we should see about 21.167 spaces... so 21 spaces. This will give 22 rivets with the first and last rivets falling on the front and rear spars. With 21 spaces, the actual spacing between rivets will be about 1.51in... about 1% off from specified 1.5in spacing.

[sjt]

I am not familar with the four place. Just take a flexible ruler and curl it against your mylar top surface. I think the mylar shows the spar flanges.


Good is the enemy of great

The above statement is not the moto for a scratch builder. We are not using a cnc we are using a plastic hammer.
h.jpg m1.jpg

I have mdf with notches -without notches -sometimes left -sometimes right -some to hold the top with an angle for smacking with a plastic hammer.

m2.jpg m4.jpg Sometimes we use sticks "wood dowel" to smack flute.
m3.jpg


Instead of Good is the enemy of great:

I recommend "Mary Poppins" "enough is as good as a feast"


For example the rib flanges are indicated as 1/2 inches. That would be great. However, you will have better success and speed of completion if you make it 9/16.

The slightest drill error might result in scrap. With 9/16 less scrap. Yes the airplane is not the lowest weight mathematically possible. If a few ounces saves countless hours do it the easier way - just go on a diet.



p.s.
We all start out with O.C.D.

My personal demaon is leaving the drill chuck key somewhere and not being able to find it when I need to change drill bits. I never got over it. I just bought extra airdrills to hold all the the bits I need.

p.p.s
Do not put things in your pockets. It allows things to get even further from the work area.

[iKilo]

Thanks Stan for the chuckle and the lesson! Much appreciated

[jaredyates]

Stan, thank you for being a consistently awesome contributor to the forum, you make our community better with your words and pictures.