The first step was to cut the outline of the speed brake recess. Recall that the outline had already been drawn before in Chapter 7 prior to glassing the outside fuselage with the area taped so that the glass would not stick to the foam.
Good thing the tape was there... the panel slid right off.
After removing and discarding the panel, I removed the tape and proceeded to mill out 0.6" of material. Notice how I left a 0.5" border inward to allow for a nice 45 degree transition.
The edges were then sanded round giving a nice transition. I also cut the 1"x2" hole all the way through the fuselage floor.
It was now time to cut the groove where the LB23 gets installed. The LB23 piece is a 1/4" plywood panel used to reinforce the area where the piano hinge gets attached to. I used the dremel to clear the foam - being careful NOT to go through the fiberglass floor on the other side.
I then removed foam 2" around the perimeter of the actuator hole.
Using a knife, I made a 50-60 degree transition - looks like a miniature football stadium! Notice how I removed some of the foam that transitions the LB23 piece. After discussing this with some of my mechanical engineering friends, I had a big "ah-ha" moment where I realized the LB23 panel acts like a giant washer to distribute the load from the piano hinge, over to the plywood which then distributes it to the fiberglass - so the more contact the fiberglass has with LB23 - the better; however, it is important to have a smooth transition between the two so as to NOT create stress risers.
And then sanded the transition smooth.
Here is a close-up...
Notice how I transitioned the LB23 with the foam such that the piano hinge will later clear - as marked by the dotted line.
I then cut the LB23 to final size... notice how it sits flush with the fuselage bottom waterline.
It was now time to prep LB23. I started out by cutting the piano hinge to size. I then measured where I wanted to place the LB22 pucks (these are cut from 1/4" 2024-T3) that will later be match drill and tapped to install the piano hinge. The plans has you install 3 of these, but again - since this is a bigger flap, I figured I would go with 4. I drew out the location of the bolt pattern and cut the LB22 pucks to size (1"x1" squares).
Using 5-minute epoxy, I installed the LB22 pucks in place.
Notice how I spaced the center ones apart to allow proper clearance of the nut heads that will install the other end of the piano hinge to the speed brake flap.
Using the dremel, I made a recess to allow clearance for the LB22 pucks.
Time to install this LB23 sucker in place! Although the plans say to use micro, I decided to apply a bead of flox.
So far so good...
I then mixed up medium-dry micro and painted the town with it on all corners! I've learned my lesson with this in the past and realized that the more micro you lay under the first layer, the less chances there is of getting air bubbles - what happens is the micro conforms to the shape of the corners and the fiberglass gets 100% adhesion to the micro - giving a beautiful, smooth, bubble-free transition. I then slurried the rest of the area in preparation for the first layer.
I want to point out that I added a bead of flox on top of the micro on the edges where the foam transitions with LB23 - in the end, this worked out PERFECT - giving a beautiful transition between these edges.
Before applying the first layer of glass, I taped off approximately 2" around the perimeter of the recess. The plan was to wet out all the layups, and then scissor trim the perimeter. The tape was put in place to help lift the layup up while scissor trimming. I then used a brush to paint plain epoxy onto the fuselage skin - this helps bond the layup to the fuselage skin.
First layup applied! I decided to apply the reinforcement layup (the third layup according to the plans) first to avoid transition lines. I paid close attention to all the transition edges. The micro and flox worked great at assuring a smooth transition. All glass is BID at 45 degree bias.
Using a brush, I made sure everything was wetted out and that no air bubbles were present.
Last layup applied, scissor trimmed 2" from the perimeter and peel plied all around.
Not such a "depressing" job after all!!