WING BUILD
#3 rib bracing is pretty straight forward in the manual EXCEPT YOU SHOULD NOT DO IT ALL NOW!
These are just used to keep that rib from pulling/bowing out when you shrink the fabric.
Later, after you have installed all the leading edge skins, you will install the fuel tanks and they won't fit in the fuel bays without having to flex the #1 and #3 double ribs out a little to get them in past the cap strips. So if you do this now but you will need to remove the screws from the braces into the spar web later when you install the fuel tanks and then re-secure them so for now, let's not install the ends of the braces that screw into the front and rear spar. For now......we will have to install the rib ends of the braces now so we can access the little nuts that go on the inside of the fuel tanks bay (inboard side of the #3 double rib) but you can easily later install the screws from the outboard end of the braces into the spar web (or just drill the hole and start the screws now).
The #2 rib false rib is also pretty self explanatory. The position of the rib is with the cutouts facing UP and slide it forward or back until the fabric rivet holes on the bottom line up with the hole when using a straight edge from ribs #3 and #4.
NOTE that Fig 51 says "holes align with other center ribs" but if you look at Section AF-AF it shows that 2.25" of the false rib should extend from the inside of the rear spar to the end of the rib. If you do this, the holes will not align..... so the Figure and Sections are in conflict. I think it's important to align the fabric rivet holes for the final look but it will shorten the amount of rib into the tail rib by about .63" which I don't think matters at all structurally. I think they changed the rib or didn't calculate correctly when doing the Section drawing. So I'm centering the rivet holes and installing the cherrymax rivets into the nose and tail ribs as shown but ignoring the 2.25" measurement in AF.
After you line up the holes on the bottom, just place a mark on the false rib and then install the meth, clamp it and then install the rivets as shown.
Note that there is a difference in how the holes are drilled when looking down into the cutouts in the false spar. When you have it correct you will notice that if you are looking down from the top, into the front cutout (the one closest to the front spar) that the hole drilled in the bottom of the cut-out will be more aft of the center of the cutout and the hole in the bottom of the aft (rear spar) cut-out will be more in the very center of the cutout.
So if you install the false spar, put the end with the hole in the center of the cutout in the aft position. If you align the fabric rivet holes on the bottom of the false spar with the other center ribs on the bottom, you will see that the most aft edge of the cutout will be 2.71" from the false spar.
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(Here you are looking down onto the false spar with the nose ribs to the right side. You can see from the digital compass that it is 2.71" from the aft edge of the front spar to the most aft edge of the cutout. In this position, all the bottom holes should line up with the rest of the ribs.)
So to summarize it again:
The #2 false rib has pre-drilled fabric rivet holes in the bottom. According to Fig. 51 (bottom right side) it says "hole spacing to align with center ribs". So in Star Trek terms.....this is the "prime directive".
So, go to the #4 center rib (I use #4 because it's the first rib pre-drilled by the factory since we have to drill the fabric holes in the bottom of the #3 double rib. If you have already matched the holes in the #3 double rib to the others correctly, then you can use it)......on the bottom and you can hold up the #2 false rib right along side itand you will see that only 1 end of the false rib bottom fabric rivet holes will align with the holes pre-drilled in all the center ribs already (just like they are in the #2 false rib). If you try and turn it the other way the holes will not match up at all.
You will see here in this photo that on this #4 center rib, the first hole back from the front spar ....and the 2nd hole aft is 2.4" and the distance between that hole and the 3rd hole is 3.4", etc.
(#4 CENTER RIB, NOSE DOWN IN PHOTO)
Now if you look at the #2 false rib, one end ONLY has the pre-drilled hole with this exact same spacing and it is as I described in the post. See the photo below and you will see the spacing is the same as the rest of the center ribs on the bottom.
(#2 FALSE RIB, NOSE DOWN IN PHOTO)
So.....THE FALSE RIB HAS TO BE INSTALLED IN THIS POSITION with the end with the shortest distance of 2.4" between the first 2 holes ....towards the nose ribs. There is no other way.
If you install it this way, you will see that looking from above, this forward end of the false spar is the one with the hole offset from the center of the front cut-out area and the hole that is centered in the cut-out area will be on the aft end.
You slide the false rib back and forth until you have the bottom fabric holes in alignment with the other center ribs and then install the rivets connecting it to the nose and tail ribs per the "sections AF-AF and AE-AE) and that's it. No other way to do it correctly.
Now an alternative is what CHUCK AND RYAN did here in his post. He drilled new holes but I didn’t find that necessary as it works fine as it is even though the top cut-outs aren’t perfectly centered.
False Rib
I thought I would post a couple of items regarding construction of the wings, even though it has been a year since this part of the build was done. Perhaps it will be of some benefit to current builders.
The false rib in the number 2 position (used with the extended fuel option only) required a little extra attention if one intends to use fabric rivets rather than stitching.
The false rib, part number SC31048, has a front and rear based on the hole spacing. Compare the spacing of the fabric rivet holes with another rib already in place and it will be obvious. The first and second holes are spaced closer on the forward side.
The manual directs that the cutouts on the top side be centered fore and aft to provide clearance for the short hoses connecting the two fuel tanks. Set the false rib in place and mark a line adjacent to the spar on the rib for future reference. Then place the false rib next to another rib properly centered fore and aft and compare the location of the fabric rivet holes. All the fabric rivet holes were 7/8” too far aft on our false rib. (The use of fabric rivets by CC is a recent change. I suspect the issue regarding hole location in the false spar will be quickly addressed by CC).
The correct location of the holes was marked and drilled with a #30 drill bit. The original holes were marked with an “X.” Note this is only an issue if fabric rivets will be used. For conventional wing stitching this would not be necessary. Indeed this is purely a cosmetic issue since I doubt many would even notice the fabric rivets being off 7/8 inch on this one rib.
Flap False Spar. Once I get the false spar on I take some 2x4 blocks and put them on the sawhorses under the spars to raise it all up so that the flap false spar; nose ribs, tail ribs, etc. won't rest on the sawhorse. Just be sure you put them under all 4 corners including your 1" block on the outboard rear spar until you have all your skins on the leading edge.
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An easy way to drill through the flap false spar (and this also works for the nose ribs into the leading edge skins) is to FIRST take a sharpie and make a good line down the center of the tail ribs ON BOTH THE TOP AND BOTTOM (and nose ribs) before putting the false spar (and later leading edge skins) in place. The holes in the flap false spar are pre-drilled, so to be sure you are drilling down into the center of the tail rib, just move it back and forth until you see the line you marked in the hole and then hold it in place as you drill through it and install the SS rivet.
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On Page 137 DON'T DO IT YET! (Or page 139 on updated manual. It's the page referring to installing the rivets from the flap false spar into the flap/aileron hanger. See figure W53).
Do not drill or install these rivets into the hanger yet! You need to do the alignment of the aileron false spar in the next section before doing this. You can install the 2 cherrymax rivets into the inboard, bottom part of the flap aileron spar into the machined rib but not the top or forward parts that overlap the aileron spar.
Ignore Page 139 where it says to squeeze the joints of the aileron false spar together. They are now making them with a cut-out in that areas.
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(This is a photo of the outboard aileron false spar for the left wing where it overlaps the inboard aileron false spar. You can see it goes on top of the inboard false spar. The latest one I got had a pre-drilled hole in that outboard one. As the manual says, the FLAP false spar outboard end at the hangar will go ON TOP of the inboard end of the inboard aileron false spar.)
On Page 153 it shows the Aileron Hanger Brackets. This is showing the left wing so the XC31404-002 part goes on the right (inboard) side and the -001 goes on the left (outboard) side. Just be sure you have the 51-1/8" from the flap/aileron hanger (outboard edge) to the center of the slot in the end of the hanger before drilling the center holes. Note that the HEADS of the rivets go on the OUTBOARD side.
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(This is looking downwards on the back side of the aileron false spar. The nut is to the outboard side and note the brackets have the ends with the shortest distance from the bolt holes goes downward)
The manual is pretty good for the remainder.
Here is a figure showing where you need to drill a 1/2" hole through the bottom of the flap false spar. This is a view from the bottom looking up at the rear spar between ribs 4 & 5. You can see the location you need to mark and drill a pilot hole with a #30 and then a step drill to get the 1/2" hole. This is so that you can pull that drag wire out that goes from the outboard rear to inboard front spar in the fuel tank bay. You can look through the hole after you drill it and see that the wire will now pass through the hole in the back of the tail rib as well as the hole you just drilled. You'll need to remove that wire when you install the fuel tank and this hole lets you do that. This is now in the manual around page 161, Section 34 on Finalizing the False Spars.
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When drilling the holes from the flap false spar and all the leading edge skins later .... into the spar (I am referring to the lip of the flap false spar and later nose skins that overlap the top of the spars and have to be match drilled and riveted in the spar), you need to be sure you are not drilling into the spar "bulb".
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If you are SURE you have the lip of the part (flap false spar or nose skin) that has the pre-drilled holes in them.....down flush with the bottom of the spar cap, then the pre-drilled holes will be safe to drill into the spar. You can put clamps on them like this to hold them down but check by looking or feeling with your fingers as well before you drill.
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Another option is this Avery spar tool I detailed in the first post of this thread. You just hold it on the bottom of the spar cap and then drill right through the hole in the tool. It has holes for a #40 and a #30 drill bit. You will see here that the holes in the skins/false spar are pre-drilled exactly the same so like I said, if you are sure you have the skin flush with the bottom, then the pre-drilled holes are fine and you don't have to use the tool. The earlier kits did not have pre-drilled holes so this fixture was a must.
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25 hours and 37 minutes into the wing build to this point.
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