Chapter 18
Turtleback/Canopy

Okay. So now we move on to some more stuff which will make this boat look more like a plane. After much agonizing, and asking everyone I thought might have an opinion, (Except for Nat. I already know his opinion.), I finally came to the decision to make the canopy significantly higher at the front AND rear. Also, I plan on having a front-hinged canopy. Alot of builders have raised the front, no big deal. Even Nat has placed his blessing on that mod. But the rear turtleback mod decision came from my sitting in the back seat of a number of Cozy's, and no matter  what, I found I had to sit with my head tilted inboard. I'm 6' even, and I just HAD to have the option of carrying a full sized passenger in comfort on long hauls. The lines are going to be more along the AeroCanard design, (BLASTPHEMY!!), without using an AeroCanard top. I found very little detail in the Archives as to the specifics regarding aft Turtleback mods. Luckily,  I stumbled across a fellow named Simon Ramirez. As luck would have it, he was building an AeroCanard. I was able to borrow his firewall and make a tracing, from which I made Jig #5.

Here you see the Plans firewall superimposed over the Aerocanard tracing.
For you builders who would like to make the same modifications that I have, here is the recipe for modifying the cozy drawings to the Aerocanard dimensions:
1. Add 1 3/4" at the 12 o'clock position.
2. Add 1 1/2" at the 10:30 position.
3. Fair a nice arc from the 12 o'clock, through the 10:30, down to the outermost aspect of the existing firewall tracing.
WARNING!!!  Do not try to be too exacting, or agonized over it being exactly right .  Let the "artist" inside you come out and "just wing it".  Next, I explain how to modify the individual  TB jig stations to get the right shape.
That being said, if you absolutely have to have a drawing, I bet you could probably get Al Aldrich of Aerocad to send you one if you make a hint that you might be buying a upper cowling from him.

 Then, after raising the front of the canopy 1.75" and making it 2" wider, I made Jig #1. From there, it was just a matter of measuring the differences of radiuses from #1 to #5 at numerous points along the drawing, multiplying by 0.8 &0.4, (which I got from the plans drawing. This will give me the "aesthetically pleasing shape.), and placed marks accordingly. I then just connected the dots, and Voila!. I had a drawing like the plans with dimensions of the new canopy.

                 Sorry for the poor quality picture.

(This is a shot of the partially assembled jig.)

 I then began assembling the jig. Taking a cue from Wayne Hicks, I used drywall screws. MUCH mo betta' than waiting for Bondo to set up! To keep the 90 degree angles. I used shelf brackets from the Depot. Assembly went pretty smoothly.

One day, while I was minding my own business, I was waiting for the 5 min epoxy to set up in the joints between the hoizontal foam and the rounded part. I had just finished placing the foam longitudinally, ( as opposed to the plans athwartships method). Next thing I know, one of the clamps came loose and fell onto the foam, along with a 5lb weight. (See resulting hole at right.)
 I immediately went into my "Saturday Night Live's Mr. Peepers the Monkey Boy" mode, and tried desperately to fit my fist in my mouth.
Fortunately, the foam that came out stayed pretty much together and I was able to repair the spot with out too much trouble. Also, this spot will eventually become a window, so. no real damage done. Here's a shot of the after. No one will ever know.
Here's a shot of the "plans" Cozy Firewall laying on a tracing of the modified drawing, laying on a piece birch. I'll be cutting this out and floxing it ot the firewall. (Picture to follow.)
After glassing and placement of the drip rail. No big surprizes here. I plan on floxing that piece of plywood at the aft end to keep things nice and round during glassing of the exterior Turtleback.
I made TB1 &TB2 different from the plans. Hope this won't bite me later on. I plan on using a layer or two of carbon BID for extra stiffness need for rollover protection

Heres' a shot of TB1 and TB2 installed. If I haven't already mentioned, and you haven't already noticed, I'm doing the infamous "Forward Hinged Canopy".

I've heard numerous stories about how the canopy "mutates" at temperature excursions. So, I thought I'd substitute a layer of carbon fiber for added stiffness.

Before removing the TB from the TB Jig, I took the radiuses, (radii?) left over from the "Making of The Jig" and floxed them into each end.... thereby maintaining the correct arc and width.
3/25/03

12/20/05

It's been quite a while since I last laid hands on the turtle back.  At left you can see where I cut out the windows.  I'm using the Aerocanard measurements, so my windows are little larger than the plans version. This step took a lot of measuring, and about six hours of work.  You really want to make sure these windows look right and achieve the effective you are looking for.  I gave serious thought to adding a bunch of curves and what not over the past six months or so, but in the end, I went with the standard look.

1/10/06
I used the Fein Tool to trim the windows. It seems to melt/cut the plexiglass very well with a minimum of dust and chopped-off fingers.

I used wedges made fron stir sticks to uniformly press the plexiglass against the outer skin of the TB. I got this trick from visiting the Velocity Factory a few months ago. Worked pretty good!

The finished product. Haven't nicked any of the windows.... yet!

Next, I glued the turtleback to the fuselage in preparation for fitting of the canopy.

As you can see to the left, there's a good 6 inches of material extending beyond the forwarded to the turtle back.  (Sees noticed the black tape on the inside of the canopy but over the turtle back.)

Trust me.  If you decide to modify the turtle back as I did, the Texas canopy from Todd Silver at Todd's canopies will fill the bill.

After what probably was 30 or 40, 000, or so iterations of fitting the canopy, cutting the canopy than fitting the canopy again, I finally got it right. I hope!)

Rather than using the Plan's method of using micro to hold the various box of urethane foam together, I decided to try a product called "Great Stuff".  This suggestion was courtesy of Dennis Oleman in a post he made a couple of days ago. He stated he uses it to quite frequently to join blocks of foam for hot wiring with great success.

My results were nothing short of spectacular.  The "Great Stuff" sets up enough in about 35 minutes and you're ready to start contouring.

After floxing the canopy to the turtle back, I made the tape lines rivers in the plans that would delineate where the frame would meet the canopy.  I then super glued some very small quarter round plastic stripping to the tape edge.  I'm hoping this will give me a nice clean edge to the finished product.

It took me about four hours from the time I started to fit the first 2 inch block of foam to the canopy to what you see at left.

 

I firmly believe the "Great Stuff" should be submitted for consideration as a mandatory change to the plans.  No waiting for the micro 24 hrs. to cure, and it held the foam blocks perfectly! It also didn't brake off in the joint while sanding and leave those unsightly gashes that I, (and others) have been privileged to go back and fill with micro.

Here is what the canopy looks like after the top layer of glass is applied. Really no big deal.  The hard part is getting the glass to a nice edge on th canopy.  One thing I did as a departure from plans, was to extend the glass 3/4" over the side of longeron in an effort to prevent future leaks.  Make sure to put 2 or 3 layers of duct tape on the longerons to allow for the underside layups of glass.
I took a tip from someone on the web and tried some 1/4 round edging used in miniature train scenery construction, and super glued it on the line I wanted to achieve where the glass meets the the glass.. so to speak. It seems to have worked pretty well, but I haven't tried the fine trimming which Wayne Hicks has already done, (that b**tard) done.

The next step, is to build a frame to remove the canopy from the fuselage.

At right is a shot of the canopy with the frame I made for it.  It's important that you make this frame sturdy, because the frame has to maintain shape until you can get the inside coat of glass applied.  After the frame is made, you make the cut line where the canopy separates from the turtleback and remove the canopy from the fuselage. (Please excuse the snow in the pic.)
After marking up the proper measurements, you dig out the foam in preparation for laying the hard points.  If you're using Uli Wolters plans, make sure you extend a hard points for the hinges further inboard than what he says in the plans.  (Ask me how I know)
After making the necessary hard points, add foam locally to make smooth transitions, and apply the glass as per the schedule in the plans.  No real surprises here.
Here are couple of shots of my hinge installation.  It seems I made those hinges eons ago.  No special "tricks to the trades" to impart here.  Although, I will say it is extremely important that you take extra special effort to insure the hinge pads are perfectly level and in line.  If you don't you will have trouble with hinge binding in the future.  Also, it is important when mounting the hinges to F-28, to move the hinge point up as close to the outer skin as possible.  If you mount the hinges as per Ulee Wolters plans, you'll end up with pinching problems in the future.  Also, make sure you build the hinge attach-point hard points high enough (low-enough, right-side up)to allow vertical travel in relationship to longerons before any lateral travel.  (Clear as ketchup, right?)  Good luck in this endeavor.
And here's a shot of the finished product.
And now, all I have to do is figure out how I'm going to raise and lower the darned thing .