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Cozy Mark IV

Cozy Mark IV : Time and Expenses

Chapter 14: Center Section Spar

In this chapter you will build the center section box spar which joins the wings to the fuselage.


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Chapter 14

# Desc Date Cost Time (hours) Details
1. Centersection jig 11/10/07 67.00 4 The cost is for the lumber and other materials to make the jig.  Cut out section D from three separate pieces of 3/4" thick particle board and joined with bondo.  Cut as per plans.  Bondo'd to table, then cut part A and bondo'd to pieces E and D.  Cut the remaining jig pieces.
2. Centersection jig 11/11/07   2 Finished making the jig. Cut pieces F and G, and bondo'd to table with parts B and C on top.  Carefully double-checked 90-deg angles, let dry.
3. Chapter kit 11/12/07 710.15   Parts and supplies from Spruce.
4. Foam parts 11/17/07   2 Started cutting out foam parts for spar
5. Foam parts & LWA 11/18/07   5.5 Finished cutting out foam parts and built the box in the jig.  While that was setting I made all the LWA inserts.
6. Interior layups 11/19/07   9 Sanded LWA1's.  Cut out CS6 & CS7 to fit (5-13/16 x 5-10/16).  Cut BID for CS6 & CS7.  Micro and 1 ply BID inside spar.  Installed CS6 & CS7 with micro, and added 1 ply BID over both sides, lapping 1" on the outboard side and 5" on the inboard side.  Added 3 plies UNI over hardpoint sites.  Installed LWA1s with flox, 1 ply BID and weighted down.  Added reinforcements over CS5 & CS8: 1 ply BID, 3 plies UNI, LWA1s @ BL 65.5, 1 ply BID, and weighted down.  Added center section bulkhead with 1 ply BID on both sides.  While this was all curing I cut out the BID for CS4, micro'd and epoxied.  Added peel ply, 1" around all edges, and left to cure.
7. Forward face 11/20/07 5.98 2 Trimmed CS4's and box, made sure there's a good fit for the forward face.  At this point I cut a 1-1/2" hole through CS6 & CS7 and installed a plastic grommet ($2.99 ea) with 5ME.  This will be used as a conduit for cables and wires coming from the wings.  (Later I'll make similar cuts in CS5 & CS8.)  Installed CS4 on the spar with micro, and weighted and taped down for cure.
8. Outside hard points 11/21/07   1 Prepared templates for the spar cap trough.
9. Outside hard points 11/22/07   2.5 Removed spar from jig.  Measured out points on CS1 and cut the sliver of foam off.
10. Outside hard points 11/23/07   14.5
  • Cut troughs for spar caps using templates
  • Cut out 1"x1/2" angles
  • Sanded four LWA4s and 2 LWA5s
  • Sanded out foam from CS1 using dremel for 1/4" aluminum inserts
  • Floxed aluminum pieces in place
  • Radius'd CS1 edges
  • Applied newspaper & duct tape to protect the sides not in the shear web
  • Wet out with wet micro and applied 4 plies UNI
  • Peel ply
  • Collapse after 14.5 hours of work!!!
11. Spar cap layup 12/8/07   7.25
  • Removed peel ply & cleaned up shear web layup.
  • Measured off BLs for top spar cap layup
  • Set up dispenser for spar cap tape
  • Installed the plywood dam with bondo
  • Newspaper & duct tape
  • Sanded
  • Top spar cap layups
12. Spar cap layup 12/24/07   4.5 Bottom spar cap layups.  I've been lapping the tape over the edge by about 1/2".  Over all these plies, this adds up.  It turns out that I was short spar cap tape on this roll by so much that there was no tape left for the last four plies.  Fortunately I had some left over from the canard spar cap, and I was able to add two more plies (the 4th from last and the last).  The plans specifically state that you can leave off two plies for the appropriate thickness, so I'm not going to worry about it.  Now I wonder if I was shorted some tape!!
13. Spar cap layup 12/29/07   2 Cleaning up.  Cut off ends of spar caps, etc.
14. Outside layups 12/30/07   10
  • Finished prepping surface
  • Cut & installed 4 spruce pieces
  • Cut out all glass for 4 plies UNI.
  • Outside layups.
15. Hardpoint reinforcement 1/1/08   2
  • Installed LWA2, LWA3 with flox.
  • 3 plies UNI, 1 ply BID, peel ply
16. Access for wing attach 1/1/08   3 Trimmed glass from the outside layup.  Cut out a template for the inboard access holes, traced onto top and cut out holes with dremel.  Sanded away foam for a 1/4" glass overlap, and beveled the rest.
17. Access for wing attach 1/3/08   2 Cut out glass for spar fore, added 2 plies UNI
18. Access for wing attach 1/6/08   6
  • Layup
  • 1 ply BID on ends
  • Knife trimmed
  • Cut 2-1/4" dia holes for access to wing attach bolts
19. Access for wing attach 1/19   1.5 Cleaned up spar and cleaned up workshop.  Set spar aside to make room for wings.

Chapter total: Time 80.75, Cost $783.13

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Last modified: Sunday, February 10, 2008