Tuesday, March 26, 2013

Ch 7: Glassing the Sides (1 of 2)

Sorta like cooking chicken...only different...
It would be difficult and messy to glass large vertical surfaces like the sides so the plans have you build some A-Frame pivots to aid in putting the fuselage in a position that makes it easier to work on.
Cozy builders call this...The "Rotisserie."

The plans don't give you many specifics about how to do it but they do give you enough basics to figure out your own solution.

Firewall Attachment
F22 Attachment
The plans suggest using the hole in F22 that would be used for the gear crank shaft but I don't know if I'll have one so I haven't drilled it.
They also suggest drilling a hole in the firewall but you would have to repair that.

For F22, I used clamps to hold my A-Frame between two boards.  For the firewall, I used two small holes that I had already drilled to locate the control rods and I bolted a 2x4 to them.  Then I put a hole in the 2x4 for a 5/16th pivot bolt.

You'll need to make the pivot points about 24" off the ground to be sure the fuselage clears the floor when turning.  (UPDATE (3/29/13):  You'll notice I made my A-Frames with a 45 degree angle.  I suggest making them more like 30 degrees between them.  At 45 degrees the feet are quite a bit wider than the fuselage and I keep tripping on them.  Maybe I'm just clumsy :-).

Right side up
Roll it around for glassing the
sides or working on the inside

The "Rotisserie" in Action

Time to glass the sides, cab

Saturday, March 23, 2013

Ch 7: Contouring the Fuselage Top

She's back upright again and now it's time to get the sides ready to glass.

No...not the saw...
First I made room for where the canard will go by cutting out the the fuselage forward of the F28 bulkhead and across to the cutoff tabs on F22.  Cutting on your fuselage is a little nerve racking...it just doesn't seem right.  :-(    I used 3 different saws for the process...my big crosscut saw, a mitre box saw, and a small drywall saw.

Ready for a canard now.  Note the square top edges
 of the fuselage sides as compared to the pic below.

It was actually much easier than expected and it came out great.  It will really look great when there's a canard mounted there!

Sanding forms for the
3 templates

Shape it up...
Next is the contouring of the top sides.  Just like I did on the bottom, I built a sanding form for each of the templates used on the top.  I started at the back with the D-D template then focused on the C-C template which is used from around the IP all the way to the seatback.  Once the C-C work was near perfect, I moved up to B-B and then to A-A.  I think doing it this way (back to front) helped me blend the curves along the sides pretty easy.

After getting A-A, B-B, and C-C  blended well, I then went back to the aft section between the seatback and the firewall.  I thought blending this section was going to be much harder than it was.  It's a long distance and the two templates are very different.  I first picked a point at the back where I wanted the shape to match the D-D template completely.  The plans say just ahead of the spar cutout...I chose a point a few inches aft of where the doubler starts.  Then I drew a line from the blue/white foam join line at the seatback to the D-D point I chose.  This forms a bit of a long triangle on the side.  Then I simply used my 22" aluminum Perm A Grit sander lengthwise to gently sand nice blended corner using that line as a guide for the blue/white foam join line.  I think it looks great.
A gentle blended shape from the seatback to the firewall

Port side complete...now rinse, wash, repeat on the starboard side
 Onward, cab

Monday, March 18, 2013

Ch 7: Glassing the Fuselage Bottom

Here we go again...
This is another large layup.  Don't believe the plans that say it should take you 3 hrs.  Remember, Nat had built at  least 2 other Aircraft before building the Cozy IV.  Even with that, I find it hard to believe he did this in 3 hours.  Plan on making it the day's activity and don't set yourself up to have to be somewhere at a certain time...you'll rush...and make mistakes.

A couple of thoughts...
Layup Map
- Make sure the shape and surfaces are what you want.  If it's not right before you glass, it won't be right afterward either and you'll just have to add micro to fix it anyway.  Glass is not a filler.

- Pre-cut the glass and mark which is which on the cloth.  Also make a map to follow just to make sure you don't forget which piece goes where in the middle of your work.
- Use longer pot life epoxy so your not rushed.  I use Aeropoxy so I used their 3665 hardener which has a 90 min pot life...worked great.
- Wet out only as much glass as you can reasonably work with at one time then move on to the next section.

Only 11.5 hrs later...done.  I was very pleased with the results...only a few small dry spots found that were easily fixed.  The slightly off colored piece of  glass on the left front was from using the last\bit of some older hardner.  It colors more and more rusty red with age but still works the same.

Glassed Bottom.
Onward, cab

Sunday, March 17, 2013

Ch 7: Bottom Antennas

About Antennae
Electronic navigation and communication require antennae.  The great thing about composite, or plastic, airplanes as they are called, is that you can embed many of the antennae under the skin of the aircraft.  Since ATC radar can see right through foam and fiberglass, it doesn't matter that the antennae aren't mounted on the exterior like they need to be for metal aircraft.  The benefits are a nice sleek looking airplane with no unsightly antenna protrusions and less drag since there's nothing hanging out in the air stream to slow this bad boy down.  It's certainly not much drag but you would be amazed at how all the small sources of drag can really add up.

RST Antenna Kit
Per the plans, I'm installing RST designed copper tape antennae except instead of using RG-58 coax, I'm using RG-400 throughout the entire aircraft.  You can find several recommendations in the archives for it.   RG-400 is similar 50 ohm coax that has replaced RG-58 as the standard for aircraft antenna feed lines   It has a stranded center conductor and is double shielded which is needed for the transponder and GPS transmit lines...oh yea...and quite a bit more expensive.  The best price I found was at B&C Specialty at $2.55/ft or $2.35/ft if you buy more than 50ft.

I'm installing the following systems that will have antennae "buried" into the structure.
- Dual radios - 1 antenna in each of the vertical winglets at the end of the wings
- Dual Navs - 1 antenna in the canard, 1 antenna in a wing
- Marker Beacon - 1 antenna on the fuselage bottom
- Glide Slope - 1 antenna on the fuselage bottom
- APRS - Automatic Position Reporting System used for flight tracking via the internet - 1 Ant in the wing

Other non-copper tape antenna that will be installed...
- Transponder - Installed in the nose
- GPS - probably in the nose

Fuselage Antennae
MB Solder Joint
On the bottom of the fuselage, I'm installing the marker beacon (MB) and glide slope (GS) antenna.  After determining where to install them, I oogered out the channels in the foam for the coax keeping in mind RSTs guidance on proximity and size of metal objects.  You need to pay attention to where the nose gear will retract and the landing light if you're using the plans design...which I'm not.  Then soldered the coax to the copper tape of appropriate length based on RSTs instructions.  After everything is installed, I potted the solder joint and filled the channel with micro.

MB & GS Antennae trial installed just before
permanent install and fill.
GS Solder Joint
To the left is my antenna layout before final install.  The marker beacon is on the right and glide slope in the center.  I punched the coax through at a point just fwd and to the pilots side center of the instrument panel.  Be sure avoid the wheel well area.

Note the oogered channel running diagonal back to the front of the IP...I changed the routing of the MB coax to keep the appropriate distance from the tip of the GS antenna and any metal.  I'm not sure if I had to do this with feedlines but I figured I would play it safe.  You can see the re-routed coax now comes toward the front more and then over to the punchdown.

TIPs:  You'll need some tools.  Based on a recommendations from an RV builder site, RST, and other internet locations, here are the tools I purchased.  Coax stripper: I bought a Paladin 11255-LC CST and it worked great.  BNC crimper: I purchased an Eclipse Lunar 300-054 crimper frame and the 300-038 die.  For soldering supplies I got Kester 44 63/37 solder.

Now for the fun...time to glass the bottom.  Onward.  cab