Chapter Log

Step 0 -
Status: Completed 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 444.55, Actual: $ 0.00
Date Completed: 00/00/0000

Step 1 - Turtleback Form
Status: Completed 
Est Time: 6.00, Actual: 8.00
Est Cost: $ 50.00, Actual: $ 120.00
Date Completed: 07/15/2007

Building the jig wasn't that big of a deal, but it was fussy work that took some time. I made one change from the plans, on advice from other builders, and lifted the "top" of the turtleback shape 1.5". This will give more inside headroom and hopefully a pleasing curve when it comes time to do shaping. But this step also required me to make new templates, so I started by tracing the templates on new paper and extending them to make the additional room.

The jig pieces themselves were cut and assembled per plans, more or less (I used some scrap wood to assemble it so some of the side supports were slightly different sizes. No big deal.) For side support, John and I found some thin aluminum flashing material at the local Home Depot (fortunately there's one right around the corner from the hangar!) and used tin snips to cut long, narrow strips out of it. These we laid into the form to support the pieces of foam.

Step 2 - Turtleback Construction
Status: Completed 
Est Time: 14.00, Actual: 22.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 07/20/2008

Wow, this was a pain. If John wasn't there to help me I'm sure I'd have walked away for a week, frustrated. Laying the foam into the form was definitely a pain, and getting it all to fit nicely was very tedious. We ended up spending a lot of time fussing with drywall screws, trying to hold the foam into the form correctly. To make matters worse, I didn't have time to do the layup by the time everything was set up, so I left it overnight. By morning, the dabs of 5-min I had used to hold the foam down had let go, and I had to spend another evening repairing them!

If I had to do this step again, I would definitely adjust a few things:

1. Install more slats. The plans setup is just barely acceptable, and raising the height 1.5" put me over the edge support-wise. I would recommend installing at least 2 additional slats per side, and packing them more closely as you go up the curve. It doesn't take long to install them, and it's cheap insurance.
2. Make sure the flashing is installed VERY firmly at every spot, especially at the top where the curve is most complex. I had used a roll of aluminum tape John had lying around, and while this was great at first it didn't stick very well, so it gave way at the top and allowed the foam to buckle.
3. Don't put your joints at the ends. You want them even so you don't get a noticeable line on one side, but that doesn't mean they have to be at the lip. Instead, cut each foam strip in half in its middle and add the extension piece there. There's not much flex in that section, so you don’t have stress on the joint. If you're careful to use very little glue, you won't get a joint line (it's easily sanded, anyway).
4. Use twice as many foam strips. It sounds time consuming, but if I had used 3" strips instead of 6" strips, they would be easier to shape for a good fit and install. Make sure to install extra flashing, of course, but I think this extra setup effort is well worth the result.

Step 3 - Turtleback Bulkhead
Status: Completed 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 01/01/2009

My turtleback doesn't have a bulkhead because it has a spar inside it where the bulkhead would normally be. See pictures and comments above and below.

Step 4 - Outside of Turtleback
Status: Completed 
Est Time: 14.00, Actual: 14.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 07/12/2006

The outside of my turtleback has a spar cap laid into it, with a metal hardpoint at each end. This will provide some extra rollover protection, because my head rests are from a car and probably won't do as much. The hardpoints serve two purposes. First, if the plane is upside down, pressure on the top of the canopy will make it try to spread. The hardpoints extend below the bottom of the canopy into slots just inside the longerons. This will prevent the canopy from spreading and then collapsing. Second, they'll serve as a mounting point for bolts that I can use to set up my canopy latches.

Step 5 - Installing Windows
Status: Completed 
Est Time: 18.00, Actual: 22.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 01/01/2009

My canopy and turtleback windows are larger than per plans. In other Cozies I've noticed that visibility is excellent IF you are in the front-seat, but the back seat was almost an afterthought. I have two sons whom I'd like to be involved in this aircraft as they grow up, and I'm hoping bigger windows will make the rear seat a more enjoyable place to fly.

Step 6 - Installing Hinges
Status: Completed 
Est Time: 0.00, Actual: 0.16
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 00/00/0000

10/17/2005:
I deferred the installation of the hinges until I was actually in this chapter, so I could use the turtleback itself as a jig to make the hinges as hidden as possible. However, one of the nuts for the hinge screws is hidden behind the shoulder support bar. To avoid having to cut a hole in the shoulder support later, and to allow complete removal of the hinges of necessary, I installed a nut plate here.

There are a few recommends methods of doing so, but I wanted to keep it simple. I drilled the hole for the screw, and marked the nut plate's position. I then drilled two tiny holes where the nut plate's ears are, and filled them with flox. I then installed the nut plate, using a small scrap of plastic wrap to protect the screw threads (but keeping the screw inserted a bit, to correctly position the nut plate. I then covered the area with two scraps of BID. The nut plate is well potted in flox - it would take a miracle to make this thing spin. (I think both ears would have to break off.)

Update:
This later turned out to be irrelevant, as I've installed a forward-hinged canopy. See Step 15 below for pictures of how that turned out. This nutplate is just a useless part lost forever. =D

Step 7 - Installing Upper Firewall
Status: Completed 
Est Time: 4.00, Actual: 3.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 06/28/2008

Installing the upper firewall was pretty easy, with one minor setback. Because I made my turtleback 1.5" taller than plans, my upper firewall (which, following the plans, I had made WAY back in Chapter 4, several years earlier) was not the right size and shape. Rather than remake it, I just shimmed it out and filled it in with scrap material.

My upper BID tape from the spar to the firewall slipped a bit in alignment, but it was a bit oversized anyway so it will still do the job. I trimmed it a bit around one of the engine mount hardpoints, but otherwise it's ready to go.

Step 8 - Installing Turtleback
Status: Completed 
Est Time: 3.00, Actual: 8.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 06/30/2008

My turtleback 1.5" higher than plans, and it is also installed higher than plans. Specifically, at the front end it's lifted another inch above the longerons, and it's spread at bit at the front edge so it doesn't produce as much of an internal overhang above rear passengers' shoulders. This area is normally hidden under a fairing anyway, and it makes the interior feel a bit more spacious for tall passengers.

Some fill-in was required with foam and plywood, but otherwise the installation was per plans.

Step 9 - Engine Mount Reinforcements
Status: Completed 
Est Time: 10.00, Actual: 10.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 10/29/2007

There are a variety of reinforcements involved here, and I've done them over a wide period of time (5/3/2007, 6/6/2007, 10/24/2007, 20/18/2007, and 10/29/2007) but they're all done now. In some cases I used plastic to hole the plies in place. I also tried aluminum foil, which some builders seem fond of. Not my favorite - I'll stick to plastic. It worked, but it was a bit touchy to remove in some spots.

Step 10 - Canopy
Status: Completed 
Est Time: 12.00, Actual: 12.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 01/01/2009

As mentioned earlier, the turtleback (and thus the canopy) is lifted a bit. We sat everything up on blocks to get it all to line up properly. The Texas Canopy that I got is actually a bit oversized, including in the front. To get all the angles to work right, I had to cut notches where the canopy met the instrument panel.

Here are some details you can see if you look carefully:

1. I messed up the inside glass a bit around the rear of the canopy. To fix it, we cut out the warped section, adjusted a bit with micro, and re-glassed the area. It's just an example of how easy it is to fix errors in composite construction, even with complex shapes.
2. My canopy has carbon-fiber reinforcements along its lower lip, running from the front back to the midpoint. I have a forward-hinged canopy and this will provide some reinforcement against crushing while it's being lifted/lowered, as well as added stiffness to prevent it from twisting as it's moved.
3. I have a spar section made of wing spar cap tape running around the outside, in a band, about where the head rests go. This provides some added rollover protection, since my headrests will be car seat headrests, and can't be relied on completely for rollover support.
4. To prevent the canopy from spreading in a rollover condition (and thus collapsing), and also to provide an attach point for left- and right-side latches, I installed two aluminum brackets in the outside edges of the canopy. They're quite strong, and run up into the spar cap, so they can distribute the lateral load if the Cozy is rolled over.
5. You can just barely see the bolts that attach the canopy to the forward hinges peeking out at the front end of the canopy. There are support blocks here with additional reinforcements to provide a strong attach point.

Step 11 - Canopy Frame
Status: Completed 
Est Time: 35.00, Actual: 38.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 11/11/2007

Gawd I hate urethane. I know it's supposed to be inert, but I still seem to react to it anyway. Thankfully John did the shaping here. He's got quite an eye for curves. Maybe that says something...

Step 12 - Carving Inside Foam
Status: Completed 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 01/01/2009

Step 13 - Canopy Hardware
Status: Completed 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 01/01/2009

Step 14 - Removable Top
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete

Step 15 - Canopy Hinges
Status: Completed 
Est Time: 8.00, Actual: 12.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 08/01/2008

My forward-hinged canopy uses automotive trunk hinges (from eBay) that have a built-in gas strut. They're designed for a luxury car (it's been a while, but I think it was for a BMW) with a fairly heavy metal hood, so the gas struts are quite strong. Two hinges together easily support the canopy.

There are tapered blocks underneath them that are glassed onto the longerons. These blocks hold the bolts that attach the hinges to the fuselage sides. The hinges themselves then have bolts through their upper brackets that the canopy attaches to. It's a nice system, actually, because the whole canopy can be very easily removed if major maintenance is being done.

Step 16 - Fuselage Top
Status: Completed 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: 01/01/2009

Step 17 - Instrument Cover
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete

Step 18 - Access Door
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete

Step 19 - Canopy Latches
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete

Step 20 - Safety Catch
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete

Step 21 - Canopy Handle
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete

I plan to make three changes. First, I removed one of the struts to measure its force. The easiest way to do this was to use a bathroom scale - the strut "weighed in" at 35lbs. I found a pair of gas springs on eBay that were about the same length and were rated for 60lbs. Hopefully that's not too much! I may only install one.

I will also machine new stop blocks and a safety latch. The hinges already have a mounting point for the stop blocks, I just need to make them accurately and install them. For the safety latches, I'm thinking about a sleeve of some sort that fits over the gas strut and drops into position when the canopy is open, preventing it from closing again. To close the canopy, you would lift the sleeve back off the strut. I just want to make sure it's easy to do, so I need to play around with different configurations.

The new gas shocks arrived and I installed them today. The new ones are slightly shorter than the old, which may actually be a good thing because it will act as an additional stop to keep it from opening too far. But I still want to work out another stop method so the gas shock doesn't have the take the whole load in tension. I had to epoxy a fitting onto the end of each to get them to attach properly, and I don't want to strain that joint too much.

One nice thing is that the new gas shocks are about half the weight of the old. I'm saving almost 250g with this (over half a pound!)

I couldn't test them, though. I didn't have any JB Weld to attach the fitting, which is what I wanted to use, so I used a high-strength epoxy I had. It'll test to 2000psi, but only after a 24-hour cure, and I didn't want to mess with it prematurely. I left the canopy propped open with a board to keep it from moving accidentally until I can get back out next week.

Step 23 - Cockpit Ventilation
Status: Not Started 
Est Time: 0.00, Actual: 0.00
Est Cost: $ 0.00, Actual: $ 0.00
Date Completed: Incomplete