FireFlys' Cozy Mark IV, #1500

Dedicated to those that lost their lives on 9/11


Chapter 10 

Building the Canard


Chapter 10 Research Summary (PDF Document) - Please contact me if you have tips/FAQ's that should be added


Pre-Step A - Hotwire Saw  

Step 1 - Trimming the Foam Blocks and Cutting the Cores  

Step 2 - Making Lift Tabs, Inserts, Jigging Cores, Laying Shear Web, and Installing Lift Tabs.

Step 3 - Jigging and Bonding the Canard Sections Together

Step 4 - Spar Cap Lay-up

Step 5 - Applying the Bottom Skin

Step 6 - Installing Hard Foam Blocks, Upper Spar Cap, amd Upper Skin


  • 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.
  • Made two tools that I could use to lay glass during the spar cap layups
  • 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.
  • Make sure that none of the dowels interfere with the lift tabs or the hard foam inserts that will be placed in Step 6.
  • I put clear tape on top of the K jigs to keep foam from sticking if any micro got through.
  • If you're using the MGS, skip the insert jigging.  You can clear the nutholes with minimal work and due care.
  • Made the lift tab build up ahead of time (during a layup in earlier chapter), cut to shape and rounded edges.



Pre-Step A - Hotwire Saw

Hotwire Saw Construction

Hotwire Saw Use/Tips








Step 1 - Trimming the Foam Blocks and Cutting the Cores  

10.1.1 Make the airfoil 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 then 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 to lines with files.  Made two tools that I could use to lay glass during the spar cap layups - they mirrored the curvature of the upper and lower troughs.   Also made straight edge templates at this time.  On the straight edge templates, I put talking points at every 1/2", and nail holes at ~2".  The 2" worked okay, but I would recommend putting a hole at every half inch to give you options on nail placement. 

10.1.2 Cut larger foam blocks to rough canard sections (2 51" pieces and 1 39" piece) - Foam blocks from Wick's came with some corner damage from shipping - there was no padding or spacing utilized.  Needless to say, I was not impressed with the packaging!  Since the Wick's foam parts are just at the specifications, I needed to really study each piece to determine how it would best be used.  I also had one piece that was ~1/2" shorter than the specifications.  Everything worked out for the canard and elevator cores, will have to wait and see about the remaining foam pieces when I construct the wing.  I ordered some extra short foam pieces in case there was a "mishap"...fortunately none had to be used.   Foam cutting is fun...there is crackling, smoke, and the smell of success in the air!  These straight cuts are perfect training to get you familiar with the process - after the first few cuts you'll be a pro!

10.1.3 Hotwire cut the airfoils and troughs for the outer 51" cores - Followed the steps per plan.  Most everything went without a hitch.  However, discovered later when I was getting ready to put down the bottom spar cap lay-up, that I had a slight error on my bottom trench cut.  Determined that when I flipped the core over to cut the bottom trough, I must have improperly weighted the foam causing the foam to bow "upward".  This caused the taper to be more shallow through the center of the outer core.  I had to make a repair to this part prior to the spar cap lay-up.  Tip for others -- pay attention to how the foam is weighted before cutting!

10.1.4 Hotwire cut the airfoil and troughs for the inner 39" core - Per plans.  No issues with this piece.

10.1.5 Carefully remove the leading edge ridge - Per plans.  Leading edge snaps off easily, then a few light passes with the perma-grit block.

10.1.6 Make dowels to align leading edge of canard - Used hardwood dowels I bought at the store, then sharpened each in a pencil sharpener.  Made sure to write numbers on each.  Since no measurement was given in the plans, I just winged it to the placement of each dowel.  If I was to do it again, I would make sure that none of the dowels interfer with the lift tabs(and build-up) or the hard foam inserts that will be placed in Step 6 (measurements provided in plans).

10.1.7 Cut leading edge away from center and inboard sections - Per plans.  No issues with this step.









Step 2 - Making Lift Tabs, Inserts, Jigging Cores, Laying up the Shear Web, and Installing Lift Tabs 

10.2.0 Make lift tabs and inserts - I let the Cozy Girrrls build mine ;-).   Outstanding quality!  Thanks Randi and Chrissy.

10.2.1 Make jig to hold rear sections in straight line - Stole Wayne Hick's idea (sort of), and used 2 stair riser caps from Home Depot (cheaper than angle iron, but I had to drill the holes on one of the sides...) to hold canard sections in straight line.  Just mounted straight edges onto the 2x4's and used the composite clecos (drywall screws) to secure the foam in place.  This worked great.  In fact, I think the slight bullnose edge on the caps were more friendly to the foam than angle iron would have been.

10.2.2 Align canard pieces in jig, check position and secure - check, check, check...I put clear tape on top of the K jigs so foam wouldn't stick to them if micro dripped through.

10.2.3 Micro cores together and confirm alignment - Other than one batch exotherming on me, all went well.  You want a fairly dry mix to avoid a lot of drips.  Once everything was secure, cleaned up micro edges using tongue depressors - cut rounded end to get crisp edge along trough wall.  

10.2.4 Make jig, position inserts, and micro in place - Didn't really care for the plans method here.  Since there is a sizeable buildup over the inserts, you can't really make the jig flush to the top, so you're already "fudging" a little.  Plus the MGS is so clear, that the jig really didn't seem necessary.  I made insert jigs in case I was wrong(you can see part of them in the picture to the left), but did not use them.  What I did: I drew a centerline on the top of the insert and micro'd the part in place (centered fore and aft, and side to side, on the shear web face).  Then I filled the holes with silicone.  Once silicone cured, I colored it with red marker so I could see it after glassing.  I also colored around the dowel holes with red marker.  After the shear web was cured, the silicone filling was easy to see.  Layed the lift tabs over the marks, traced the holes onto the glass, then starting with an undersized bit drill bit, cleared the holes.  When everything was confirmed, finished with the correct size bit, and installed the tabs (step 10.2.8) as instructed.   Everything came out perfect, and it was much easier/faster than messing with a jig!    

10.2.6 Prep surface and glass for shear web lay-up - Per plans

10.2.7 Apply shear web layup and lift tab build up - Per plans (mostly), cut a few extra pieces of UNI than the plans called for - the math just didn't add up!  Other than that, the layup went great.  I deviated slightly from plans by creating my lift tab build-ups ahead of time.  During an earlier chapter, I realized I may have some extra epoxy, so I made a 9-ply lay-up sandwiched between peel ply.  After cure, I cut the lift tab pieces to shape.  I figured this would be much easier than dealing with the small pieces during a wet layup.  I thought this made for a very clean install and would recommend it to others.

10.2.8 Flox and Bolt lift tabs in place - Found and cleared lift tab holes without difficulty.  Used drywall screw to remove silicone, then floxed tabs into position.  Used some Dacron peel ply to conform flox edges and prep them for next step.






Step 3 - Jigging and Bonding the Canard Sections Together

10.3.1 Make "K" Templates - On advise from others, made 12 K templates (vs plans 10) out of 1/2" MDF particle board.  

10.3.2 Align K Templates onto table for jig - Attached each K template to scrap particle board, then screwed each template onto work bench in the proper position.  Centered the 2 extra templates under each outboard core.  

10.3.3 Clear dowel alignment holes in shear web - Found and cleared the dowel alignment holes without difficulty.

10.3.4 Remove interference points from leading edge cores - Used the Roto-Zip and the various PermaGrit tools to clear away the interference points.  Just took my time and checked everything frequently.

10.3.5 Align canard cores, then secure aft center and aft inboard cores in jigs - Used drywall screws to secure aft core into 

10.3.6 Micro leading edge and alignment dowels into position - Once everything was secure, cleaned up micro edges using tongue depressors - cut rounded end to get crisp edge along trough wall.




Step 4 - Spar Cap Lay-Up

10.4.1 Prep shear web for spar cap lay-up - As mentioned in Step 10-1-03, I identified a problem with my left side outer core - unfortunately I did not catch it BEFORE I completed the shear web and reattached the leading edge cores.  I assume that due to improper weighting during the hotwire cut, I created a trough that did not deepen evenly (following a straight line from the deeper interior notch, to the more shallow outer cut) but due to a bow, remained more shallow than intended as the trough moved from the tip to the fuselage.  To correct, I carefully removed the shear web and foam that made up this "bump".  Then I removed foam to create a "wedge" (with approx. 1/2" legs)  for an interior flox corner to tie undamaged shear web (that runs between the top and bottom of the canard) to the repaired section.  Reapplied the plies called out for in the plans, overlapping the undamaged sections by approximately 2", and covered those plies with 2 plies BID at a 45 degree bias and peel ply.  Once cured, checked everything then prepped area for the spar cap layup.

10.4.2 Cut UNI and BIS for bottom skin lay-up if plan to do at same time you do spar cap lay-up - Did not plan to do at the same time, so I cut the cloth per plans prior to Step 10.5.5.  Rolled out glass inside house, on my clean hardwood floors.  

10.4.3 Rig spar cape tape to dispense during lay-up - Rigged up a quick stand using a step ladder and a few clamps.

10.4.4 Complete spar cap lay-up - Nervous about working with the tape, but you quickly become adept at working with it.  After laying tape in position, snip the nylon line (red on my roll) in the middle of the run, and pull out from each end.  Then, once the tape begins to wet out, the cross thread can be pulled out as one continuous piece.  As the trough fills, you move inward on each successive lay-up (~4" each side).  I used the plastic tablecloth material to cover the taped areas that did not need additional layers (especially by the UNI roll), so new tape did not stick in areas I didn't want it to.  Used the tool I made in step 10.1.1to squeegee the tape.  As the build-up grew, I used my fingers to "drum" the tape (imagine lightly tapping on a bongo drum) - this helped disperse and compress the tape into the trough.  I was able to get 12 plies into the trough without overfilling.




Step 5 - Applying the Bottom Skin

10.5.1 Prep spar cap for bottom skin layup - Since I used the plastic tablecloth as the peel ply, I rough sanded the spar car.  Pretty simple, and allowed me to check the contour as I went.

10.5.2 Sand depressions at outboard end to add tip later - Used the Perma-Grit tools to sand the depressions

10.5.3 Tape off leading edge tangent and lift tabs - Duct's best tool!

10.5.4 Apply 1 inch peel ply at trailing edge - Instead of using brads, I used spray adhesive on the peel ply then attached to trailing edge.  This should make hacksawing the tab off much easier.

10.5.5 Complete bottom skin layup - Straight forward.  Completed per plans.

10.5.6 Trim leading and trailing edges - Straight forward.  Completed per plans.












Step 6 - Installing Hard Foam Blocks, Upper spar cap, and Upper Skin

10.6.1 Attach support for trailing edge (PVC pipe and 1"x 3" boards)  

10.6.2 Flip assembly, level, and secure to work bench - remove peel ply from trailing edge -   

10.6.3 Cut fishtail off, remove peel ply, and contour trailing edge -   

10.6.4 Make and install foam hinge point inserts  

10.6.5 Complete upper spar cap layup  

10.6.6 Complete upper skin layup  

10.6.7 True up trailing edge  


Chapter 9    Chapter Index    Chapter 11

N911HF - No 911 Heroes Forgotten