CHAPTER 21       STRAKES
 

3/31/05

I've decided to incorporate the CozyGirrls Strakes . This mod is probably the one significant departure from plans which every builder should consider. It makes the cockpit feel soooooo much more roomy, without significantly changing the structure or adding significantly to the complexity of this ordeal.

This is the section where get to actually make the "boat" look like a plane with stubby little wings on the sides. I had a heck of a time getting the main spar mounted correctly, but with the assistance of the Smart Tool I was able to get it placed correctly.

To begin with, to make the ribs, I glassed both sides of two sheets of the blue Divinicell foam.  I then cut the square pieces out according to the size I needed, and then traced the templates onto the pieces for the ribs. 

On the CozyGirrls website there's a diagram for efficient use of foam (Click this)http://www.cozygirrrl.com/chapter21a.htmhttp://livepage.apple.com/shapeimage_2_link_0

I then took a straight piece of lumber, glued another piece of wood precisely at 33" from the centerline of the fuselage. This was my reference from which I mounted R33 in the vertical plane. For the level plane, I turned on the  laser and placed the 17.4WL line on the rib in line with the laser line and clamped it into place. I used R33 as my reference from which I placed R57 across the horizontal plane. I used a small work table to jig it to the correct level. Clear as ketchup, Right? Hopefully, the above pics will help.

Due to the fact I have a relatively unstable floor (wooden decking), and the plans method was written before the availability of cheap lasers, I decided to depart from the Plans method for setting the ribs.

After accurately marking the 17.4 W.L. on the Spar, Fuselage, and ribs, I setup my laser level to paint a line on the marks I first made from a point about 45 deg. from the fuselage. This effectively eliminates any parallax errors, IF the line matches the laser across the entire fuselage AND spar.

Here's where I made numerous changes to the screen viewing hole.  It turns out you'll need to move the hole 3" forward from the plans dimensions.

I directly sighted the area I'd need to look at , if ever, to see the screen.

At left, you can see how I used some aluminum shower railing, instead of wood to hold the upper firewall in place while the layups for caring.  Presently, I've no excuse to NOT mount the turtleback.  I just can't wait!

You can also see the difference between the AeroCanard and the Cozy firewall profiles.

Here I am cutting two of the strake skins from a single 4x8 sheet of PVC.

If you have access to a fiberglass supply store... this is the only way to do it. The plans method has you piecing foam together. The 4x8 sheet (you'll need 2) was about $50. About the same as Wicks/Spruce, only not cut up for shipping.

This is the spot where I break with tradition (again)  and install the "Cozy Girrrl Strakes" modification.

I used 1/2" slices in the foam for the traditional bend in the Strake and @1/3" slices for the more severe curve forward of R33. (Fuselage is to the right.) As you can see, you will get a few little gaps here and there, but those be filled with foam and micro, so no one will ever know.  At this point, I'm really excited about putting these in.  I truly feel they're going to add so much more creature comfort to the cockpit with a minimum of design change.  I plan on carrying the 60° UNI through the inside of this modification and on the outside of this modification to maintain as much structural integrity as possible.

Here is a view of the underside of the top skin inplce for the creation of the  "T-Hat flanges". I just feel I'm getting a better bond/seal than with the plans method. They were constructed of 2ply BID.

I have a REAL tough time 1ply BID-ing anything. They just feel so flabby. It was a real pain the butt working overhead like that, but I feel, in the long run, I should get a better seal and less chance of leaks.  Time will tell.  As you see in the picture to the left, the depressions and made way back in chapter 6 or so soon to be a little below the bottom of the strake tank.  I'm not sure if I just made them both wrong or if there should be a change in the plans, but at present my plan is to grind out the half-inch of foam above the depression, re-glass it, and then install Vance Atkinson's fuel gauges and be done with it.  

At right,  I'm creating the flanged surface which mates with the angled area of the Main Spar. Once I decided exactly where the flange need to be, I cut the aft end of the top skin 0.1" long, took out an angular piece of the foam along the bend line (@.2"), then took a piece of the shower door hardware I saved when I renovated my bathroom (7 yrs. ago... which just happend to fit the foam/glass width just right.) and slid it onto the skin.

Next, I put the heat gun, judiciously, on the bend line of the glass. Just when the the glass became soft, I bent the end of the skin up and held it there @3 minutes, and Voila'! Flanged end. Not sure how the plans say to do it... if at all.

Here is one of the 300 or so times of trial fittting the bottom skin. Note the extra rib I added between  R33 and R57 to prevent the dastardly sag we've all read about in the archives.

Note: You can see the "t-hat" flanges in this shot as well.

Somehow, I managed to install both lower skins without managing to get a picture of how I did it.  Basically, I took a small table that I had laying around and place it underneath the strake.  I made a couple of jigs of the same curvature as the ribs, and use those to hold the lower strake and place while the flox was curing.  

I decided to augment the plans fuel gauges with some electric gauges which I will be able to view on instrument panel.  After talking with Wayne Hicks, I decided to go with the Princeton Electronics fuel probes.  They are little pricey, ($195 each), but I feel they'll give me the reliability I need.  The advanced model has a calibration procedure which uses five different set points to give you linearity of readout of fuel quantity.  I mounted them in the same manner in which the Cozy Girls mounted theirs.  The difference in my installation though, is that because my turtle back is wider than the plans version, my probes will will not interfere with the turtle back.

The first step to getting the probes mounted was to obtain some thickwalled aluminum tubing.  Then, thread the end to accept a 1/4" NPT fitting.  It took me about nine tries to get the threads to be straight enough so that the probe won't touch the tubing.

Second, dimple the heck out of the tube so the flox can grab it.

Third, drill a half-inch hole at an angle so that the probe would be between an 1/8" 1/4" from the bottom of the tank.

Next, flox it in.

At left, you can see the final installation.

Also, you can see how I installed in the dual vent lines, which takes care of the nose up nose down venting problems you'll someday cross in the archives.

Also, I suppose I should make a comment about the venting tubing.  As others have mentioned other web sites, the plans amount of tubing is nowhere near enough unless you do it as I have.  My plan is to bring the two lines out of the tank as you see at left, then join the two and run a single line to the top of the turtle back in and run the lines as I feel necessary later on to complete the venting system.

You can also see the screen dome cover in the fuel supply hole which I picked up at Wal-Mart.

At right, you can see, if you look real close, but I have kind of augured-out about 1/4" of the foam of the fuel tank bulkheads between the t-flanges.  The reason for this is that I may, at some point the future, want to switch to a nonconventional engine like a Mazda which can run on mogas which has been known to contain solvents that the blue foam we use to make our fuel tanks out of to dissolve.  I also did the same thing to cut outs for fuel sloshing in the window to view the fuel strainer from the fuel.  This should eliminate any and all contact of fuel with the bulkhead foam material.  As you'll see later, I'm also coding the interior of the tanks with Jeffcoat.

7/12/05At left is a shot of the port strake sealed w/Jeffco sealant. It's a part epoxy/resin product which has been designed as a tank sealant, a garage floor coating, and a dessert topping!!! Really though, it comes highly recommended by others in the group and I also understand it's being used by Lancair....Good enough for me. If you going to use it, the ratio is 100:50 resin/hardener by volume and 100:40 by weight. I decided on this for 2 reasons. It's impervious to all chemicals, which would leave me open to other fuel choices in,the future.(Rotary??) (4/09 Update: Apparently not so impervious. See Chris Barber's tribulations. Yechhh!!!) I ordered a 1 gallon kit directly from the company. Spruce only sells the 3 gallon kit, but you'll only need the one. ($100) It goes on like thick paint, tacks up in about 2 hours enough to apply a second coat. I first squeegeed 1 coat of MGS to the interior, waited for tack-up, then did the 2 coats of Jeffco. Hope it works!!!

7/17/05

Here's a shot of the strake top skin prior to placement. I've gotten pretty good at this Jeffco stuff. I takes about 1.5-2.5 hrs. to tack-up, depending on ambient temp, and then it's ready for another coat. The 2nd coat can wait for up to 24hrs. and still get a molecular bond.

7/17/05

Here is the Port Strake top in place w/clamps and weights. Can't wait for the leak test. I haven't felt this kind of stress sing the landing gear tabs! If you look close, you can see the strake vent tubing bend around in a weird fashion. After I had the top down, I plugged one vent with my finger and blew on the other, hoping for some resistance. NOPE! Now I've got a helacious leak, right?  Well, while blowing/sucking on the vent, ( get your minds out of the gutter ), I was in a position to feel a slight breeze on my forehead. Turns out I forgot to plug the mount for the fuel probe. Once I did, I was able to draw a vacuum! No major holes..(Whew!) Next, checking for pinholes.

7/30/05
Well, seeing as how EVERYONE is at OSH, (except for Wayne Hicks), I guess I'll just have to work on my plane.

Good news! No leaks in the port strake. I then, with utmost confidence, proceeded to place the top on the STBD strake.  Everything went pretty smoothly.  Except for the fact that the starboard strake would not hold pressure.  It seems like every time I try something new, I get it right the first time, but when I try to do the second time, I somehow mess it up.  To make a long story short, I ruminated over different ways to detect the leak.  I thought about stealing a Freon detector from local garage, but at the last minute I went and got some soapy water and sprayed it on the most likely sites for leaks.  I found it in about the first 3 1/2 minutes.  It was coming from the top of the Princeton fuel gauge probe I had installed earlier.  Boy, was I happy about that.  I promptly removed the probe and replaced it with an NPT plug and re-pressurized.  We'll see if that fixes the problem. Later note: Yep. No Leaks!!!

Here's a shot of my pressure testing set up.  Pretty simple, but functional.  The latest consensus is to use an altimeter to monitor for pressure differences.  I would have to agree.  Although, you have to make sure to allow for temperature changes, and to not get too excited if after 24 hours a show a pressure decrease.  Let it go for at least two to three days

And here, is the first shot of my CozyGirrrl strakes from the interior.  I have to tell you all, this is the most significant change you can ever make for the pilot's/copilot's comfort.  Give serious thought to this!

And yes, that's my dusty hand you see in the foreground.

8/13/05 After some confusion as to where to deliver my epoxy, I finally  was able to continue work on the strakes. At right, I'm stippling the peel-ply on the right strake. Same for the left, with an additional layer of carbon BID for reinforcement.

After getting the plane flipped over, and glassing the outside of the strakes, I carved a piece of blue foam to dimensions listed in the plans, covered it with electric tape and glassed it.

Above, you see the finished product.  By the way, the fuel line was installed as per the plans as well.  They went in much easier than I thought they would.  Just make sure you have a tubing Bender, as the aluminum tubing is soft and kinks very easily .

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