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HS-902 amd HS-904 fit...

llavalle

Well Known Member
Alright, me again...

I'm having trouble with some fitting between the HS-902 Spar and the HS-904 ribs. The 3 holes that are side-by-side through the spar are fine. Its the top and button holes that don't fit at all.

DSC03047.jpg


To make sure I was not missing something I took couple of measures. Note that none of the measured holes were enlarged.

Measured the spacing on the HS-901 skin, it was 0.814"
DSC03048.jpg


Measured the spacing on the HS-904 rib, it was 0.812"
DSC03051.jpg


Measured the spacing when both(HS902 and HS904) were attached together, it was 0.861... it's almost 0.050 too wide.
DSC03052.jpg


As you can see on the last picture, the rib is firmly touching the spar... the fit is good for those 3 holes (filled with clecos)

Do I need to bend something to make it fit?? Or maybe the the HS-902 Spars are mis-punched? I checked both of them and they have the same problem. Unless I'm seriouly missing something :confused:

What do you think?
 
Philippe,
You might have misspunched parts. But what I found when building my 9, if the holes didn't match I was doing it wrong:confused: In fact I did not have a single bad part in my kit. (standard build) lucky?:)
 
Mispunched parts are a possibility - I've got a couple of punched ribs for my right leading edge that were mis-punched from the factory, but as I'm converting it to a fuel tank I won't be using those ribs anyway.

For that offset, I think I would be very tempted to matchdrill them to -4 and keep going.
 
Do I need to bend something to make it fit??

Philippe-

I agree with the comment above. If a part does not line up perfectly, it has meant that I did something wrong. However, with that said, I had a few tabs on the end of ribs that were just a wee bit off, like yours above. Bend it in just a bit, and consider it fluting work. If the rest of the part is aligned with all the holes, this is just a matter of not being bent or fluted to the proper spot. Since it is fitting inside the spar, the cut out notch changes it's shape slighlty.
 
Just got an answer from Rob@Vans

He said they looked at it and that I should drill as-is, elongating the hole in the rib. I don't think it's a good idea. If I do so, the skin holes won't line up when I put it on.

Tonight, I'll try to fit the skin to see where exactly is the problem... it can be 2 things

1-The spar is mis-punched... the holes are too far from the edge
2-The ribs are mis-bended, the bent section is too small on the edge so the actual length of the rib is larger than it's supposed to...
 
Spar or not

Philippe,

if it's the spar all ribs would not fit correctly. what I would do is try to figure what all is suspect and bad.

1. First I would try all the ribs to see if the problem is on one rib or all or just a few.
2. I would play with 1 rib to see if i could get the holes to align.
3. Try putting on the skin and see how all 3 holes align on the spar.

is the problem only on one side or both?

if you determine the problem is with the spar I would get a new one. if only 1 or 2 ribs I would follow vans instructions and drill it. I suspect the little tab on the ribs is not providing much strength to the HS.

Just my sugestions.

Hope you get this resolved quickly and get back to building bliss.
 
I would be cautious about drilling as is, if you want to maintain proper edge distance. That rivet hole is already quite close to the edge of the tab.
 
1. First I would try all the ribs to see if the problem is on one rib or all or just a few.
That, I did. All the rib are off by what seems to be the same amount

2. I would play with 1 rib to see if i could get the holes to align.
I did that yesterday, there was no way I could get a cleco in there
3. Try putting on the skin and see how all 3 holes align on the spar.
I intend to do that tonight... I have the feeling that if the problem is that the ribs are too long (bent at the wrong place), all the holes aft of the spar will not fit on the skin...

If it's the spar that's mis-punched, then only the spar holes will be offset..

To be really sure, I'll put the nose ribs in place and try out the skin... If the hole on the spar aligns with the skin, then I can assume the spar is OK and the problem is from the ribs... I'll see tonight...

is the problem only on one side or both?
Both

Btw, thx all for the feedback.. so far, Vans was not as helpfull as you were :eek:
 
Mismatched holes

Punching errors can occur, but the machines that do this are inherently very accurate if programmed correctly. My own personal experience with these parts suggests that location of bend lines may vary.
1. Check the skin fit in multiple areas - esp top and bottom. See if you have an equal but opposite error some where else.
2. Check to see if spar flanges, top and bottom are of equal length.
3. Check the vertical line up of left and right spar halves as well when clecoed to the center doubler. Looking for symmetry of fit. It may help you convince yourself, and Vans' that you need a new part if things vary more than in this one spot.

If only this one spot is off, follow Van's advice.
 
Alright, got a second anwser from Vans...

Apparently, the gap, 1/2 hole, is within tolerances

Gus@Vans suggested to try the skin on. He's convinced that the punching are OK and it's the bend in the rib that's not ajusted properly. He told me :
Clamp the rib to a bench with a wood block inside the bend, with the appropriate .040-050 gap between it and the flange. Use a light plastic hammer to gently tap the flange onto the block to move the bend the small amount necessary to get the holes to line up

I'll try that and get you back on this.
 
Don't drill as-is

I've had a couple instances where the little tabs at the end of the ribs were 1/2 hole or so off. At the suggestion of someone here, I drilled the holes in the spar and rib tab to final size out of assembly to prevent elongating. Then dimple and "adjust" the rib tab fore/aft by hand as needed to align.


Alan
RV-9A Wings
N984AW Reserved
 
Alright. I squeezed the rib in a vise and reworked the bend on the ribs. That worked fine.

This is the shim I made to hold the rib in the vise :
DSC03064.jpg


Worked the bend a bit and it ended up fitting quite well ( I still need to straighten up the flange a bit...)

DSC03065.jpg
 
Alright. I squeezed the rib in a vise and reworked the bend on the ribs. That worked fine.

Worked the bend a bit and it ended up fitting quite well ( I still need to straighten up the flange a bit...)

DSC03065.jpg

The flange is fine just as it is, that is if you're reffering to the slight warp at the web of the spar. I have had some flanges warp that little bit when riveting.
 
The flange is fine just as it is, that is if you're reffering to the slight warp at the web of the spar. I have had some flanges warp that little bit when riveting.

Yep, I was using the wrong term... it's the web that is a bit wrapped. I thought this was an issue then I remembered about the fluting :p
 
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