FireFlys' Cozy Mark IV, #1500

Dedicated to those that lost their lives on 9/11

 

Chapter 11 

Elevator Construction

 

Chapter 11 Research Summary (PDF Document) - Please contact me if you have tips/FAQ's that should be added

 

Step 1 - Cutting Foam Cores and Bonding to Torque Tubes

Step 2 - Installation of the Bottom Skin

Step 3 - Installation of the Top Skin

Step 4 - Installation the NC-6 Inserts and the NC-3 Hinges in the Canard

Step 5 - Checking Elevator Travel and Installing Tip Fairings

Step 6 - Installing Pitch Trim Belcrank and Elevator Mass Balance Weights

TIPS / WHAT I DID...

  • On the straight edge templates, I put talking points at every 1/2"; I would recommend putting a nail hole at every half inch as well.
  • Check all foam pieces for damage, and determine best use for each piece (determine what areas will be discarded).
  • Pay attention to how the foam is weighted before cutting.
  • Use the foam cutting sequence per plan, but cut the top and bottom working from trailing edge to the leading edges
  • You need MIRROR copies of the torque tubes, so be attentive to the placement of your NC-2 inserts
  • Use a 1/8" drill bit for the NC-2 pop rivet
  • Like some others, I skinned the tops of the elevators before the bottoms
  • If I did it again, I would have sanded a depression to allow for the balance weight (CS10) 2 ply UND, before glassing the skins
  • Mounted L jigs to table before bonding elevators into position - allowing gravity to help hold everything in position
  • Make sure you position tip fairing foam at enough angle to account for the line extensions called out for in Fig. 21
  • Used a scrap piece of wood as a backer to stabilize the canard tip during the shaping of the top
 

 

 

  

Step 1 - Cutting Foam Cores and Bonding to Torque Tubes  

11.1.1 Make the airfoil templates - Did this when I made the canard templates.  Traced the M drawings onto plain paper, then used spray adhesive to attach template tracing to masonite.  Since the spray adhesive gets everywhere, I covered the entire masonite board with thin paper towels (it's what I had available).  This allowed me to still see the tracing, but prevented the jig saw from gumming up and staining the template drawing.  Rough cut templates, then finished shaping to lines with files. Since so many builders have trouble fitting the cores to the control tube, I would consider making the tube notch slightly larger by using the actual tube as a reference.     Step Done 

11.1.2 Rough cut foam pieces to proper lengths (4 - 27.5" pieces) - My hotwire saw was long enough to cut a single 55" core, but the plans recommend cutting smaller pieces for improved accuracy.  I stuck with the plans method.     Step Done

11.1.3 Hotwire cut the airfoils - Followed the cut sequence per plan, but cut the top and bottom working from trailing edge to the leading edges.  This seemed much easier by allowing us to set the hotwire one the extended tip of the template before moving into the foam.  First core had a few joggles on bottom, but was certainly usable.  However, decided to make two extra core since I had extra foam.     Step Done  

11.1.4 Cut the elevator torque tubes to proper length - Plans have you do this because the original canard was shortened to improve CG properties.  Bought my tubes from the Cozy Girrrls - they already took care of it.     Step Done

11.1.5 Check NC-2 fit, adjust, and secure in place - Like many other builders, I found that the NC-2 inserts would not fit into the tubes without filing the tube cutout corners. I ran into a few questions at this point.  First, I'm sure it said it somewhere, but I had no idea what size a #30 hole was.  So I simply checked the size of the pop rivet and found that a 1/8th" hole was a perfect fit.  Secondly, when inserting the NC-2, which direction should the small hinge pin hole face.  After a little thought, and study of Fig. 4, I ended up securing the NC-2 with the hinge pins forward.  I understand that direction is a little confusion, since the hinge pin hole will be "rotated" and centered downward when installed in the core.  But for now, think of the tube as if it were the finished elevator (leading edge, trailing edge, outboard end, and inbourd end), you want the hinge pin hole to be on the "leading edge".  Remember too, that you need a MIRROR copy for the opposite side elevator so be attentive to the placement of your NC-2 inserts.      Step Done

11.1.6 Prep the cores, then micro elevator cores in place - Plans have you do this because the original canard was shortened to improve CG properties.  Bought my tubes from the Cozy Girrrls - they already took care of it.     Step Done

 

   

Step 2 - Installation of the Bottom Skin - Changed Sequence, did this after Step 3

11.2.1 Check contour of elevator with templates, then prep for glassing - Per plans, just go slow and easy with the shaping.  Since this layup was done after the top skin, I prepped the trailing edge on the BOTTOM for a glass to glass bond by removing some foam and rounding the remaining foam so the glass lays more easily.     Step Done

11.2.2 Glass with 2 plies of UND - Per plans, 2 crossing plies at 30 degree orientation. The goal is to have a very light lay-up. Once cured, trimmed edges.     Step Done

11.2.3 Fill trailing edge depression with dry micro - Per plans, 2 crossing plies at 30 degree orientation.     Step Done 

 

Step 3 - Installation of the Top Skin - Changed Sequence, did this before Step 2

11.3.1 Check contour of elevator with templates, then prep for glassing - Per plans, just go slow and easy with the shaping.     Step Done  

11.3.2 Glass with 2 plies of UND - Per plans, 2 crossing plies at 30 degree orientation.      Step Done

  

 

 

 

 

  

Step 4 - Installation the NC-6 Inserts and the NC-3 Hinges in the Canard

11.4.1  Clear NC-2 openings - Fairly straightforward, but the plans don't specify how far aft on the elevator to "clear".   I cleared the entire area that extended aft along the line created from the "floor" of the NC-2 insert.  This way I could install the elevators without restrictions.  During finishing I will fill any area that does not interfere with the rotation of the elevator.

11.4.2  Prep and cover outboard ends of elevators - 1 Ply BID per plans, with flox corner.  Taped elevator surface and stood elevators on their outboard ends during cure to prevent any overflow from getting all over everything.      Step Done

11.4.3  Insert NC-6 inserts, secure, and clear hinge pin lock holes - Per plans.  Like most, the BSPQ44 Cherry rivets are a little long for the hole.  Some have used the shorter 43's, but since I had the 44's, I just advanced the rivet while squeezing until the rivet was fully seated.  Before securing the inserts, I made marks on the outside to help identify the "blind" holes once they were in the torque tubes.  The plans don't say which side of the hole to clear (the hinge pin set screw hole is drilled all the way through the NC-6 insert), but it seems intuitive that the hole facing the bottom of the elevator is the side to be cleared.

11.4.4  Cut, fit, and secure the spool piece to the offsets - Per plans.  Nothing too difficult here, however, I had slight issue with the parts I received from the Cozy Girrrls.  Their parts are beautiful, but I had some trouble advancing the hinge pins through the offsets - at one point the pin even became stuck in the offset.  I think the pin was slightly oversized.  Cleared all holes and cleaned pin until fit was improved.     Step Done

11.4.5  Install elevators to spool piece - Per plans.  Most time spent making sure that elevators are flat and that everything lines up correctly.   Step Done

11.4.6  Install elevators to canard - Since I was working alone, I needed an easier way to set the elevators in the jigs than the plan method.  To do this I attached tabs onto the "L" jigs so I could secure them with screws onto my work bench.  Then I set all the jigs into position - keeping them perpendicular to bench and offset equally over the edge.  Once that was done, I could easily attach the elevators with a few dabs of 5 minute epoxy (mixed with some micro).  Once this was cured, I was able to unscrew the jigs and flip the assembly into position to test fit.  The nice part (besides being able to do this alone) was that I didn't need to bondo the assembly onto the canard.  I was able to hold everything in position by lightly weighting the jigs.  This was helpful, as you may need to remove the assembly several times to tweak the trailing edge.  NOTE - remember that the "L" jigs have been changed to insure a full 15 degrees up-travel so you should have ZERO gap between the elevator and canard.   Step Done

11.4.7 Mark and cut slots for NC-3 hinges - Once the elevators were set correctly, I marked the area where the slots would need to be cut.  The plans only say to use a 1/4" drill bit as a "router".  However, I cut and removed the skin using my Fein saw and a razor blade so the drill bit wouldn't grab at the fibers.  Then I used a combination of the drill bit and files to finish out the holes.     Step Done

11.4.8 Set NC-3 Hinges into canard with wet flox - Wet flox helps mix flow easier into holes, but is more prone to ooze out of the bottom of the slots and possibly onto your elevators.  I ended up mixing my flox a little thicker, then filled only to the lowest point of the slot.  Once cured I finished filling the slots with flox when the elevators were out of the way.

 

 

 

 

 

 

Step 5 - Checking Elevator Travel and Installing Tip Fairings

11.5.1 Check elevator travel with Template G - Template G was revised (NL#80), unfortunately the revision comes in the form of a photocopy that is not at actual size.  You must first find the right enlargement percentage and reprint it (using the reference marks at 8" and 10.5" to validate), then piece together the two parts.  Would have preferred that they just provided a revised M drawing. Regardless, flipped canard over and checked elevator travel.  Still have slightly less than -15 degrees, so I will need to do a little work on the canard trailing edge.  

11.5.2 Micro foam cores onto canard tips - Plans have you position canard back into the "L" jigs to get the elevator into the 0 degree cruise position.  However, since the L jigs have changed that is not an option.  Instead, I secured the canard and elevators in the proper position using blocks and weights.  The plans also have you secure foam blocks onto the canard tips, but don't specify much as to the actual position.  I placed the right side canard tip in the position I wanted, then drew a line where the canard met the foam.  Then, using locations from this core, I measured reference positions and transferred them to the left side core.  Mixed up some stiff micro, then secured cores in place with pins during cure.   Step Done

11.5.3 Transfer shaping guidelines to rear of foam - I was too focused on providing holes for the hinge pins and making sure that the bottom of the canard was covered, that I failed to provide enough forward pitch on the foam to allow for the line extension shown in Fig 21.  Not too big of a problem, just required tacking on some additional foam.    Step Done    

11.5.4 Carve top of canard tips to shape - Per plans; I used a peanut butter jar covered with sandpaper to shape the curve.  In addition, I also tacked a small piece of wood on the exterior (using drywall screws set into the foam that will be carved from the bottom when the canard is flipped) to offer some stability when sanding the thinner trailing tip.   Step Done

11.5.5 Glass top of canard tips - Plans states to use 2 plies of BID or UNI (UNI being recommended).  I went with the BID since it shapes better around bends than the UNI - otherwise, nothing special here.  Removed the elevators and hinge pins to prevent any epoxy from getting on surface or pins.   Step Done

11.5.6 Carve bottom of canard tips to shape - Before starting to cut, I made templates (one for the bottom, and one for the side) to provide a guideline for the curve, then transferred these to each tip. Rough cut the larger portions with a hacksaw blade, then slow and steady sanding with various tools soon yielded the desired shape.     Step Done

11.5.7 Glass bottom of canard tips - Plans states to use 2 plies of BID or UNI (UNI being recommended). Again, I went with the BID since it shapes better around bends than the UNI.  Before glassing the bottom, I made reference marks to depict the centerline position of the hinge pin to aid in the placement of the conduit.  Used saranwrap to assist in holding glass to rounded edge during cure.   Step Done

11.5.8 Micro hinge pin conduit into canard tips and glass interior surface of tips - ...

11.5.9 Cut and shape hinge pins to fit - ...

11.5.10 Install set screws - ...

 

  

Step 6 - Installing Pitch Trim Belcrank and Elevator Mass Balance Weights

11.6.1 Position and secure the NC-5A trim belcrank - ...

11.6.2 Install the outboard elevator weights - Made jigs and located per plans.  Used Rick Maddy's method of wrapping leading edge of elevator with sandpaper to match the contour in the foam...several passes back and forth and I had a perfect fit.   After epoxing foam spacer and weight to each elevator, I sanded the spacer to create a smooth transition from the weight to the elevator.

11.6.3 Install the inboard weights on the CZNC-12A assembly - The plans say to bolt the weights to the inboard side of the assembly, but it does not specify what hardware to use.

11.6.4 Verify nose heavy balance of elevators - ...

11.6.5 Cut out pocket in canard to house outboard balance weights - ...

11.6.6 Fill and contour finished canard - ...will be done during "Finishing" chapter

 

Chapter 10    Chapter Index    Chapter 12

N911HF - No 911 Heroes Forgotten