Re: Building the EX3 - Tips & Hints
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).
Note that you may need to move the measurements around a little on the double ribs so you don't hit around a nutplate (front side) or a rivet where they put the 2 ribs together to make the double rib. It really doesn't matter as again, this is just a brace to keep the fabric from pulling the #3 rib away from the opening.
THE MANUAL IS WRONG WHERE IT SAYS IN RED NOT TO INSTALL IT ONTO THE RIB. You WILL install it on the rib now because you will not be able to do it after the fuel tank is in. For NOW, do NOT install the screw into the SPAR and DO install it at the rib.
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 W90 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 front 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. W90 (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 beside it and 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.
Flap False Spars
I added a short Youtube video here at this link about this https://youtu.be/sD3tc-RqnBQ
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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FOR THE AILERON FALSE SPAR, SEE THE NEXT POST FOR DETAILS AND PHOTOS (Not enough room on this post).
OK. So here is the order of what to do:
- First, install the big FLAPS FALSE SPAR. Fit it into position, clamp the turned down edge part that goes into the fuel bay so that the bottom of the lip is flush with the bottom of the spar there. The outboard tab goes on top of the machined rib/hanger and should be flush with it.
- Line up the pre-drilled holes with the tail rib centerlines we marked. Drill the very top row of the holes (up closest to the fuel bay) and install those SS rivets. Then move down towards the outside of the false spar and drill and rivet the next row of holes....then go UNDER the tail ribs and install the first, most outboard holes and then the last holes on the bottom of the tail ribs.
-Square the machined flap/aileron hanger again to be sure it's square and then match drill the 2 holes in tab that is on the BOTTOM of that hanger and install the 2 HDW-CR3213-4-3 rivets through the pre-drilled holes into the machined hangar (NOTE: The manual W92 calls for a 4-2 rivet but that is too short. Use a 4-3). Just look at the pre-drilled holes in the parts to see where they go. The pre-drilled always go to the outside so you can match drill through them.
- NEXT drill a single hole from the topside of the hanger through it and through the false spar tab that is there in that little triangle area and install an SS42D rivet from the topside. The tab of the spar goes inside that triangle area and on the bottom side of it. See W92 where it says "Install rivet from this side" in red.
- NEXT, we will install the inboard aileron false spar and fit it per the manual. The lip/tab on top of that spar will go under the tab there from the flap false spar. DON'T DRILL OR INSTALL THIS TOP 2 TABS DOWN YET UNTIL AFTER YOU HAVE INSTALLED THE OUTBOARD AILERON FALSE SPAR because you will be moving it back and forth getting it to fit properly out at the end hanger. This is in the following section so DON'T DO IT YET!
- Set the outboard aileron false spar with the tab with the pre-drilled hole that is on the inboard end, over the top of the outboard end of the other inboard aileron spar and line up the inboard edge of the machined hanger. Pay attention here to the pre-drilled holes on each end and make sure any of those tabs and ends are on the TOP of other false spar parts. So for example, looking at the OUTBOARD AILERON FALSE SPARE, on the INBOARD END of it, you will notice the TOP tab will go on TOP of the INBOARD FALSE SPAR (it has the pre-drilled hole) but on the bottom tab at that same location, you will notice it will go on the INSIDE or UNDER the tab end there on the INBOARD FALSE SPAR.
- Put the 3 fixtures in place on the 3 hangars per the manual.
- Follow the manual and drill #6 & #7 rib and then go back to where the INBOARD AILERON FALSE SPAR overlaps the FLAP FALSE SPAR and install the rivets and screws shown in W92 on page 36.5. You don't really need it a "Marson" rivet gun as shown in photo 158 Page 40.9. (as I said, it won't pull cherrymax rivets anyway) as you can use your modified (ground down) puller.
These rivets ARE NOT HARD LIKE CHERRYMAX RIVETS ARE. You are using all pop rivets here, so you don't have to have the tip of the rivet puller perfect to pull these rivets. Note that on the top rivet of the overlapping pieces on the machined rib that you are using the longer HDW-97525 pop rivet into the hanger. They have changed it now so they are using screws and nuts in place of rivets per the diagram.
The Figure W102 on Page 40.10 is wrong. Go back and see W92 since they changed this figure to add screws in place of a couple of the rivets.
- Then follow the manual and drill #8 rib holes and then go back and put in the rest of the rivets on the side and bottom of the tail ribs. I just install the rivets. I don't put in clecos and then go back later. Also, you can go ahead and rivet the intermediate tail ribs there between ribs 6, 7 & 8.
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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 40.12 and W103, 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. (note the figure shows the heads on the inboard side but that is wrong and the RED sentence above notes that.
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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)
Note that the aft edges of the flap false spar and the aileron false spars may not align even where they overlap. This doesn’t matter because later you will be installing “flap gap seals” over the flap false spars after installing the flaps and will not see the aft edge of the flap false spar.
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 42.1. NOTE: The last several kits I have received already had this hole drilled.
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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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