FireFlys' Cozy Mark IV, #1500

Dedicated to those that lost their lives on 9/11


Chapter 19 

Wings and Ailerons


Chapter 19 Research Summary (PDF Document) - Please contact me if you have tips/FAQ's that should be added


Step 1 - Building the Wing Jigs

Step 2 - Setting up the Jigs

Step 3 - Cutting Foam Cores

Step 4 - Assembly of Foam Cores and Layup of Shear Web

Step 5 - Bottom Spar Cap

Step 6 - Bottom Skin

Step 7 - Top Spar Cap

Step 8 - Top Skin

Step 9 - Wing Ribs

Step 10 - Ailerons

Step 11 - Controls

Step 12 - Attachment, Wing to Centersection Spar



  • Step 1 - I recommend that you allow for all of the jig links to be removed (don't flox) - this is important when you are skinning the cores.
  • Step 2 - I built a platform to lay out my jigs, rather than bondoing them to the floor.
  • Step 3  - 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.
  • Step 3 - Take time to trim each foam block so sides are straight/plumb.  This will make for cleaner butt joints
  • Step 3 - I added a 3" block between the two outboard blocks, and raised the height of the leading inboard block by 1.5" to avoid ugly surface seams.
  • Step 3 - On the back of page 19-11, you should be able to see the drawings through the paper.  Trace these onto the back page for a "left wing layout".
  • Step 3 - Draw accurate waterlines on all the cores, and along shear web cuts.
  • Step 3 - Recommend adjusting templates for aileron torque tube and electrical conduit cutouts to allow for side entry, this makes for cleaner surface prep prior to skinning.
  • Step 4 - "Re-roll" half of the UNI pieces to flip the orientation of the fibers.  This makes it easier to unroll the pieces during the layup.
  • Step 5 - Packed shear web "dip" at forward edge with flox before laying shear webs.  
  • Step 6 - Slightly recessed foam in areas that will be reinforced so I won't have "build-ups" to blend on the final finish
  • Step 8 - Rather than use a Dremel tool, I used my Permagrit tools to carefully sand the rudder cable channel (Care is needed when working near the ailerons).
  • Step 8 - I made recesses on the surface where the aileron hinges attach so I can use ClickBonds and maintain a flush finished surface.
  • Step 8 - I did not use peel ply on the leading edge of the ailerons, and "sealed" the cut lines with pour foam.
  • I cut the right wing first, then completed the left wing.



Step 1 - Building the Wing Jigs  

19.1.1 Cut the 5 rectangles shown in Fig. 1 from 1/2" plywood.  Mark the 7" horizontal lines (which will align with the 17.4" W.L.) and 4" trailing edge line. - Per plans.  However, I used 5/8" particle board instead because it is what I had available.  5/8" is also the minimum dimension that many other builder's recommended.        Step Done 

19.1.2 Glue the jig templates (from drawings M-20, M-21, and M-22) to the boards. - I traced the drawings to preserve the originals, then glued them to the boards.  To do this I aligned the 17.4 W.L. on the drawing to the ones on the borads.  Then I weighted down one side of the drawings, lifted the opposite side and sprayed some adhesive on the board, then glued that side in place.  Once set, I repeated the process on the other side.  NOTE - Like many others, I agree that the M drawings leave a little to be desired when it comes to accuracy.  I just took my time and made sure that each jig template was aligned as best as possible.       Step Done 

19.1.3 Saw each jig along the 17.4" W.L. and the designated centerline. - I did this step after 19.1.4 to make sure that everything would line up exactly as intended.       Step Done 

19.1.4 Use 1" x 8" boards (4 ea. for Jigs 1-4, and 1 for Jig 5) to "link" disassembled pieces using wet flox on permanent side and bolts on the sides that will be removed during the various build stages. - I did this step before 19.1.3 (see note above).  Rather than using wet flox, I used bolts/liquid nails at the fixed points, and bolts only at the removable points.  NOTE - I would recommend that all of the links are bolted/screwed in place, so that they can be fully removed (The "fixed" links end up getting in the way when you complete your top skin layup..  Make sure that you mark each piece so everything goes back correctly.       Step Done 



Step 2 - Setting up the Jigs

19.2.1 Draw a straight line 125.6" long and set the jigs leading edge up along the line as depicted in Fig.5.  Assure jigs are square to each other and level in both planes.  Then bondo jigs to floor. - Like others, I made a small platform.  Using angle brackets, I was able to then line up the jigs correctly, and assure they were level in both directions.  Only thing I would have changed is the "stoutness" of my platform.  I used particle board for the top and cut in 2.5" strips (stood on edge) as the base.  Turned out that there was still some flex to the unit, which required careful shimming.  If I were to do it again, I would build a more rigid platform and add lag bolt legs (like others) for easier adjustment.        Step Done - Right wing / Left wing


 Right Wing:





Left Wing:



Step 3 - Cutting Foam Cores

19.3.1 Transfer M drawing to formica/masonite to make templates - I traced my M drawing in order to keep the originals intact.  Otherwise, per plans, just go slow and easy with the shaping.  Note - Recommend changing the templates for the torque tube and electrical cutouts. (see 19.3.7 for details)    Step Done  

19.3.2 Stack foam cores together (per page 19-11) and attach with sticks/5 minute epoxy - This takes a little longer than you may think.  I have yet to receive any foam without some type of damage to it.  So spend some time looking at each piece to make sure damaged foam will end up in the scrap pieces, and not on the finished part.  It is worth taking some extra time to trim each piece with the hotwire, as necessary, to assure the pieces are square to each other and all lines are straight.  I did not bother with the epoxy sticks, finding it is just as easy to work with tape/drywall screws to hold everthing together for all the cuts.  I added a 7"H x 3"W x 54"L (min) block between the two outboard cores, rather than use a scrap piece on the leading edge.  This gave me a nice clean leading edge.  On the inboard planform, I sliced the leading 7"x14"x41" block in half (giving me 2 - 3.5"x14"x41"), then sandwiched a 1.5"x14"x41" (leftover from my canard work -- I purchased an extra piece in case of mistakes) between the two halves.  This prevented me from having a seam on the top surface that comes from using the scrap on top.   Step Done - Right Wing / Left Wing

19.3.3 Measure and cut each planform - Per plans.  Make sure to "measure twice, cut once".  Pay special attention to the 28" and 42" dimensions used to create the proper angle (your blocks may be wider than the 14" specification, or like me, you may have added pieces).    Pg 19-11 gives you the planform layout for the right wing only; everything is reversed for the left.  A simple way to make sure you don't get confused is to create a "left wing layout", by tracing the images on the back of Pg 19-11 (On my plans, I could easily see the drawings on Pg 19-11 through the paper).  This will give you a mirror image to work from.     Step Done - Right wing / Left wing

19.3.4 Attach templates, and cut cores - Some builders have made little bridges to span the shear web cut outs (like was done with the canard).  I planned on doing this, but in the end decided to just cut as is.  This worked fine for me, but does require some decent coordination with your cutting partners.  First talk through all cuts, before you start.  When cutting, slow down your pace as you approach the corners to shorten the wire lag.  Make sure both people are comfortable so they can hold the wire steady at the point.  When you reach a pause point, begin counting only when both of you have reached the point.     Step Done - Right wing / Left wing

19.3.5 Cut cores in half at shear web - Cut per plans, assuring that cut was perpendicular to waterlines.     Step Done - Right wing / Left wing  

19.3.6 Bond the cores together to create the 5 pieces - Per plans, except I waited until I completed all the cuts (torque tube, ailerons, aileron control access, and electrical conduit) before microing the pieces together.  Pay attention to speading excess micro slurry so you don't have oozing onto the surface.    Step Done - Right wing / Left wing

19.3.7 Cut torque tube cutout in FC1, then modify FC1 core for control installation - Followed plans on 1st wing, then varied sequence from plans on second.  First I placed the templates in position (the hole at 9.2" and the BL 67.5 template) and drew a line between the two entry points.  Then I made the 1" TE & 6" LE cut per plans.  Then I put the BL 31 template in place, using the reference lines for proper positioning, and cut the holes.  NOTE- To make surface preparation easier, I also change my cutout procedures on the second wing (wishing I had thought of it when I did the first).  First, I cut off one of the "tabs" on the BL31 hole template.  I placed the template in position per plans and drew the cutout onto the foam.  Then, I rotated the template 90 degrees so I could use the remaining tab as a stop, and enter the hole at 90 degrees rather than from the top (see picture to the left).  I also had to modify the BL 67.5 template to allow for a similar entry.  I did this by cutting an entry on the leading edge, and "closing" the designed entry by taping a small stick in place (making sure that it will not intefere with the hotwire).     Step Done - Right wing / Left wing

19.3.8 Trim the interior of the FC1 control access cutout - (Did this step before 19.3.6)  Drew the .6" outline on both sides of the cutout.  Since I had not bonded the pieces, I clamped the hotwire on it side and rotated the piece along the wire to make the cut freehand.  This worked fine, and I left some "wiggle room" so I could sand to its final shape.  If I did it again, I would have someone guide one side, while I guided the other, to make a slightly cleaner cut.     Step Done - Right wing / Left wing  

19.3.9 Cut aileron cutouts - Per plans.     Step Done - Right wing / Left wing  

19.3.10 Cut electrical conduits - Located per plans, but used the "side entry" method described in 19.3.7 on the second wing.  This allows me to fill the "entry cut" with micro and avoid dripping through to the cutout channel.     Step Done - Right wing / Left wing  


Right Wing:






Left Wing:






Step 4 - Assembly of Foam Cores and Layup of Shear Web

19.4.1  Confirm all foam cores fit together in jig - Because you have to cut the outboard cores as close to the top of the planforms to save foam for the winglets, you will end up with a "non-flush" edge between the outboard and middle cores.  When put together, I had ~ 1/8" gap on the top side when the bottom was flush.  All I did was transfer this 1/8" gap to the bottom side, and carefully sand off the this corner to the top until I had a flush surface.    Step Done - Right wing / Left wing

19.4.2  Set aside leading edge cores - On my second wing (after verifying that all the cores fit properly in 19.4.1.), I went ahead and microed the leading cores together out of the jig.  To do this, I drew a straight line on my workbench.  I secured FC4 in place with the WL aligned to to my guideline.  Then, microed FC5 in place assuring that the leading, top, and bottom edges were flush, and the WL at the outboard end was aligned with my guideline.     Step Done - Right wing / Left wing

19.4.3  Micro FC1, FC2, and FC3 together - Per plans, being careful not to get micro too close to the edges, or in the cutouts.  You don't want excess micro getting to surfaces.    Step Done - Right wing / Left wing

19.4.4  Cut out the wig-attach depressions and notch for LWA4 & LWA6 - For the bolt access cutouts, I just fashioned a quick hotwire tool using heavier gauge wire shaped to fit the desired cutout.  Using drywall screws, I just sandwiched this wire between two boards so I had a handle.  After testing on a scrap piece of foam, I then carefully freehanded the cut.  Worked great.  On the second wing, I held a 2x4 up along side the wing to make the freehand cut a little steadier.  My plan was to wrap the scrap piece with tape and wedge it back into the bolt access cutouts while the 2 ply BID cured, but I didnt bother doing this.    Step Done - Right wing / Left wing

19.4.5  Glass a 2-ply BID liner in the wing-attach depression - Per plans, although I did 3 plies on each.  Also, rather than making "tapes", I just worked in dry BID into the curves.  This worked fine for me.    Step Done - Right wing / Left wing

19.4.6  Fabricate, fit, and attach W18's in place -  I made a "redneck metal bender" by clamping a piece of angle iron along my bend line.  I cut the aluminum bridge per plans, but left the lip a little long to be sure it would clear the finished spar cap layup.  Once the spar cap layup was complete, I just used my Fein saw to cut the lip flush with the surface.  I also made flox corners at all the locations that LWA4 and W18 made contact with the 2 ply bolt access cutout.    Step Done - Right wing / Left wing

19.4.7  Complete the shear web layup - Per plans.  I cut the 12 UNI pieces as directed and rolled them onto cardboard tubes so they didn't lose shape.  I then took 3 each of the 13" and 14" rolls and "re-rolled" them onto a second tube to "flip" the cloth.  This allowed me to just unroll each tube directly onto the wing during the layup to insure the proper fiber orientation.  On the second wing, I just went ahead and left my platform on top of my worktable to glass and used stools and the table to stand on (my table is VERY strong - so no problem standing on it).  This made it easier to work on the top/bottom sides.  For me, I would do it this way again -- your results may vary...   Step Done - Right wing / Left wing

19.4.8  Add 3-ply BID pads and LWA2 & LWA3 at attach points - Per plans.     Step Done - Right wing / Left wing

19.4.9  Square the corner of FC4 - Per plans.  However, I forgot to do this step on the left wing while it was still standing on its trailing edge.  To correct this, I squared the bottom and top side before skinning each, respectively.    Step Done - Right wing / Left wing

Right Wing:



Left Wing:


Step 5 - Bottom Spar Cap

19.5.1 Lay wing (resting on 1/2 jigs) on table bottom side up - Per plans, except used angle irons and screws to secure jigs in the correct poition.   Step Done - Right wing / Left wing

19.5.2 Build dam to contain spar cap - Per plans.  .   Step Done - Right wing / Left wing

19.5.3 Glass the 9 layer (+/- 1 layer) UNI tape to fill the spar cap trough. - I needed 9 plies.  Before I added the UNI, I packed the area along the top cores (where the shear web was rounded) with dry flox to prevent a "dip" in the finished spar cap.   Step Done - Right wing / Left wing

19.5.4 After cure, round spar cap edge between BL31 & BL67.5  - Per plans.   Step Done - Right wing / Left wing

Right Wing:


Left Wing:





Step 6 - Bottom Skin

19.6.1 Prep surface and peel ply at designated area - I added the 65" peel ply piece at the aileron joint, but not along the trailing edge.  Based on my experience with the canard, I decided it would be easier to carefully sand the trailing edge area before adding the top skin (Step 8), than to remove the peel ply and foam as the plans suggested.  I removed material aroung the wing-attach access holes to allow for a cover plate to be added that will be flush with the finished skin.  In addition, I sanded slight depressions at each area where reinforcements were added (wing tip and around BL 67.5) so I wouldn't end up with a "build up" in those areas.  On the left wing, I added a NAV antenna; routing the cable so it would run through the existing wingtip light conduit.   Step Done - Right wing / Left wing

19.6.2 Glass the 2-ply BID and reinforcements - Per plans.   Step Done - Right wing / Left wing

19.6.3 Add dry micro to trailing edge - Per plans.  For a little cleaner look, I ran a strip of masking tape ~1'' in front of the trailing edge, laid down micro, then removed the tape before micro cured.  After cure, replaced tape to protect surface while sanding.   Step Done - Right wing / Left wing

Right Wing:


Left Wing:



Step 7 - Top Spar Cap

19.7.1 Lay wing (resting on 1/2 jigs) on table top side up - Per plans, except used angle irons and screws to secure jigs in the correct poition.   Step Done - Right wing / Left wing

19.7.2 Build dam to contain spar cap - Per plans.  .   Step Done - Right wing / Left wing

19.7.3 Glass the 12 layer (+/- 1 layer) UNI tape to fill the spar cap trough. - I needed 13 plies on both wings.  As in Step 5, I packed the area along the top cores (where the shear web was rounded) with dry flox to prevent a "dip" in the finished spar cap.   Step Done - Right wing / Left wing

19.7.4 After cure, round spar cap edge between BL31 & BL67.5  - Per plans.   Step Done - Right wing / Left wing


Right Wing: 





Left Wing:







Step 8 - Top Skin

19.8.1 Create a channel and install Nylaflow tube - I installed the tubing using the placement required for the hidden rudder bellhorns.  This required a reroute vs. the plans.  The primary difference is that the tubing exits the wingtip at 1.2" ahead of the trailing edge and runs back parallel to the trailing edge as far as possible.  The tubing then runs as near to the forward/outboard aileron corner and continues to the same wingroot position specified in the plans.  Be very careful working near the ailerons as the cutouts below are FORWARD of the surface cut.  If you get too aggressive you will go through...ask me how I know.  Not too hard to fix (I made a little shelf of foam below the conduit), but it was avoidable.   On the second (left) wing, I just used some of my Permagrit tools to sand the channel rather than use the Dremel tool.  This ensured that I wouldn't be too aggressive.   I partially filled the channel with dry micro until cured, then used InstaFoam to fill the remaining area.  Once set, I sanded the InstaFoam flush with the surface.  On the left wing I repeated the process, but used only the pour foam to set the Nylaflow tube.   Step Done - Right wing / Left wing

19.8.2 Prep surface and peel ply at designated area - After my experience on the canard, I decided I would avoid using the peel ply on the aileron cutout areas.  I'm comfortable that I can carefully prep those areas without using the peel ply.  However, to keep excess epoxy out of the cutouts, I used pour foam to "seal" them.  I was very careful to use very small amounts so I didn't fill the channel below that was carefully hotwired earlier.   I also made recesses in the surface where the aileron hinges will attach.  My plan is to use click bonds here - the recess will hopefully allow me to maintain a flush finished surface.   Step Done - Right wing / Left wing  

19.8.3 Glass the 3-ply BID and reinforcements - Per plans.  On the right wing, I forgot to add the 3-ply UNI reinforcement over LWA2.  So I had to prep the area and add it after the other layup was cured.  I used Wayne Hick's straight edge and clothes pin technique on the trailing edge.   Step Done - Right wing / Left wing

19.8.4 Attach a 2 foot reference board to wing surface - Per plans - parallel with waterline.   Step Done - Right wing / Left wing




Step 9 - Wing Ribs

19.9.1 Remove foam (.7" depth) at BL 67.5 and prep attach depressions-     

19.9.2 Lay up 2 ply UNI and 3 ply BID per Fig. 43 -     

19.9.3 Remove foam at inboard end, and prep foam as detailed -     

19.9.4 Lay up 3 ply BID over rib area, 3 ply UND over LWA6, and clamp LWA7 in place -     

19.9.5 After cure, cover LWA7 with 1 ply BID -     



Step 10 - Ailerons

19.10.1 Lay out dimensions and cut ailerons from wing -   

19.10.2 Jig wing leading edge down and prep foam -   

19.10.3 Lay up 3 ply BID in trough, and 1 ply BID at hinge area -   

19.10.4 Notch wing top skin for hinges -   

19.10.5 Fabricate metal parts from pg. 19-17 -   

19.10.6 Prep LE of aileron, and bond 7/16" (A13) steel rod in place -   

19.10.7 Prep area, and micro A10, A2, and A5, then cover with 1 ply BID -   

19.10.8 Remove .4" depth from aileron ends, and cover with 2 ply BID -   

19.10.9 Align hinges on wing, then drill holes per Fig. 51 -   

19.10.10 Temporarily mount ailerons to secure hinges (with Bondo) in place -   

19.10.11 Secure hinges in place with pop rivets (24) and flox -   

19.10.12 Verify ailerons are properly balanced (if not rebuild) -   

19.10.13 Mount ailerons and check proper movement -   




Step 11 - Controls

19.11.1  Fabricate parts and bolt together per Fig 23. - 

19.11.2 - remove the glass at the torque tube cut out -

19.11.3 Flox phenolic block against glass rib -

19.11.4 - After cure, layup 1 ply BID over phenolic block -

19.11.5 - reinstall the aileron and the belhorn - 

19.11.6 - Assemble bracket and adjacent parts, assuring 20 travel from neutral position -

19.11.7 - bolt the assembly onto the shear web and hookup pushrod




Step 12 - Attachment, Wing to Centersection Spar

19.12.1 Mark pilot points on top of the center section spar and on top of the wing, verify they match -

19.12.2 Using a #10 drill, drill pilot holes on aft and forward faces of the center section spar

19.12.3 open these holes using a 10" long 1/4" diameter drill, drilling from forward face to the aft face - 

19.12.4 - jig the right wing topside up ensuring level board is level -

19.12.5 position the center spar, to ensure top and bottom surfaces lineup with the wing, then bondo center section spar to the wing - 

19.12.6 using the 10" long, 1/4" diameter drillbit clear all 3 holes. Make sure you clear the drillbit every 1/4' or so. - 

19.12.7 now using the 5/8" spot facing tool carefully open the 1/4" holes -

19.12.8 Secure level boards to the top surface of the center spar section at points A and B

19.12.9 Fill the inboard hole of the forward face on the spar with foam and cover with 2 plies of BID

19.12.10 Fit LWA9 bushings to fit holes, then epoxy into place for cure -

19.12.11 Complete the wing installation using the hardware specified in plans. Record in your plans and aircraft logbook the number, thickness, and location of any washers used.



Chapter 18    Chapter Index    Chapter 20

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