Sunday, January 13, 2013

Ch 7: Prepping the Landing Brake

The landing brake was cut out during the building of the fuselage it needs to be somewhat re-installed before the bottom gets glassed.  The area around it get's routed out 1/16" below the surrounding area and the brake is tacked in place with 5 min epoxy.

Routing out the area around the landing brake
I used a router tool I have for my Dremel to prep the area around the brake.  This worked really well.

The router tool for my Dremel made it very quick
to carve out of the 1/16 depth of foam.
After the brake is tacked back in place and the surrounding area routed 1/16" down, layers of 1" wide duct tape, approximately 1/16" thick, is placed around the brake essentially forming a larger brake door surface. This is temporary as epoxy doesn't stick well to duct tape.  It's hard to see now, but in chapter 9 the brake will be cut back out around the tape, the tape will be removed to make way for glass on the other side, and the whole thing will be hinged in place and the actuator installed.  After that, the remaining area that was routed out (see pic below) will be filled with micro to form a nice seamless blended bottom across the landing brake.

(Deviation) Notice that I decided to extend the hinge all the way across the brake vs the plans shorter hinge.  I'm hoping this will help eliminate any tendency for it to warp like some others builders have seen.

The landing brake ready for the bottom glassing.

Fergelli FA-PO-150-12-4 Actuator
 Since I mentioned the actuator, I plan to install a Firgelli electric actuator vs the manual plans version.  This actuator has been used by several other builders, has a 4" throw, 150 lbs load, limit switches at each end, and a feedback potentiometer so I can wire it to my EFIS and know what position the landing brake is in at any time.  More on that when I install it in Ch 9.

One more step before glassing the bottom...antennas!  Onward, cab

Saturday, January 12, 2013

Ch 7: Contouring the Bottom

Time to turn this box into something with smooth sexy curves !  After sanding down the NACA scoop and sanding the foam to shape around the rear bulkhead area, the next task is to shape the aft end around the firewall so it smoothly flows into the forward fuselage.

The first step is to remove the foam covering the longeron and LWY from 5.5" ahead of the FW aft.  This is where the main spar will fit and you will need this area to tie in the glass when it's installed.  You also need to bevel the edge of the remaining foam into the longeron and LWY so glass from the fuselage can smoothly tie into those parts.  Some builders beveled the entire length of the foam edge but indications are that this is only needed where the foam leads to the longeron or LWY.  The pics below show my interpretation of how this is supposed to be done.

Aft fuselage side before foam removal
Aft fuselage side after foam removal

Aft fuselage side after sanding the transition
from the fuselage side to the firewall
Next, per plans, I sanded a smooth transition from the FW to approximately 25" in front, and at the bottom of the fuselage (top in pictures since it's upside down).  This is kind of a nerve racking task because it's a little hard to know if you're sanding enough or too much to get to the shape you need.  The FAQs give a pretty good description of what you're looking for and I also consulted multiple other builder sites for pictures of their results.  You'll likely start to uncover the electrical channel...if you do it's time to stop.  Here is what I ended up with.

Corner after the initial 45 degree shaping cut w/ a saber saw
Now I worked on shaping the squared corners of the bottom from front to back.  As the plans recommend, I used a jig saw to cut a 45 degree cut along the edge but I didn't cut all the way down to the longeron.  Instead, I cut a little shallow and used a belt sander to get down closer (although I still didn't get to the 1/4" exposed longeron...but close).

Here you can see my shaping tool
with center marks and my corner line.
Very smooth and even results
(Tip)  Using the template from the plans, I built a sanding tool and began the back and forth until I got a nice rounded shape.  I marked the side of the tool so I could keep it centered on the longeron.  I also ran a line down the center of the corner with a sharpie.  That way, when the line started to disappear, I knew the corner was filling the template tool and I was almost there.  Be sure to make long consistent strokes.

After the front half is sanded to shape to about the middle of the landing brake, the area starts to change so that it blends nicely into the aft shape at the landing gear bulkheads.  This was the hardest part to get correct and make sure both sides match.  I over sanded a bit in some areas and had to go back and fill/sand with micro to get it correct.  Here's how it ended up.


Sunday, January 6, 2013

Ch 7: Gear Area & Rear NACA Scoop Prep

There are 4 birch pieces that get cut and then installed in the aft section.

Parts A & B are simple triangular pieces that provide a solid backing for exterior foam.  Note that the craft sticks were great to hold the pieces straight up while the flox cured.

Parts C & D are polygons that form bracing between the firewall and aft landing gear bulkhead.  I had to adjust the dimensions for parts C & D a bit to fit properly between the FW and LG bulkhead.  It's not real clear in the plans but the firewall drawing shows part D to be installed horizontally.  When I did that, I ended up with a small gap where the vertical and horizontal pieces come together.  Other builders have had this same issue and it is noted in the I filled the gap and moved on.  

Backside of Parts A & B (left) and C (right) while curing

Front side of A, B, & C showing the space where foam fills in.
Also, you can  see the NACA scoop to the left
before it was sanded to final shape.

Parts C (vertical) & D (horizontal) installed
w/ flox  filling the gap between.  The open
space gets filled  w/foam and shaped
 to match the bulkhead/firewall.

Closing out the scoop:
Next the foam for each of these areas was installed along with the PVC foam lining around the aft portion of the NACA scoop where it leads into the cowling.  This was then sanded down to match the outline of the firewall and aft landing gear bulkhead.

Rear bulkhead area completed and ready for glassing.
Between the bulkheads is where the landing gear will be installed.
An access panel will be formed to cover the gap in Chp 9.

To Joggle or Not to Joggle?
The plans call for cutting a 1/8th inch joggle into the edge of the NACA scoop at each of the landing gear bulkheads and the installation of some threaded aluminum slugs.  In fact, the bottom is installed with this joggle already in mind.  This is to allow for the future installation of the landing gear cover.  Getting glass to lay down properly on these joggles is notoriously difficult.  I decided NOT fact I filled in the gap formed on the installation of the bottom with a sliver of PVC foam.  I plan to follow Wayne Hicks landing gear access door plan as it's easier and looks to be a better fitting part when complete.  

Onward, cab