This blog is for entertainment purposes only, and is not meant to teach you how to build anything. The author is not responsible for any accident, injury, or loss that occurs as a result of reading this blog. Read this blog at your own risk.

Saturday, November 05, 2016

Ch 10 - Canard - Part 1

Roncz and canard cores (9.8 hrs)

In January 1985, RAF made available plans for a new canard (CP #43 - page 1) that would eliminate the downward pitch change experienced by some when entering rainy conditions. This trim change required a small aft force on the stick to maintain altitude. 

Roncz canard airfoil

The new canard was designed with the Roncz R1145MS airfoil, and produced considerably more lift than the original GU25-5(11)8 airfoil. This enabled the new canard to be designed with less span, reducing wetted area and thus drag. 

Original GU canard airfoil

The Roncz canard had a negligible rain trim change, and the rain only added a couple of knots to the stall speed, meanwhile the normal stall speed was essentially the same, but max speed increased up to 3 knots. One interesting fact is that the Roncz canard mandated the use of six Vortilons on the main wing.

For these reasons most Long EZ to date have been built with the Roncz canard, and I will do the same.

The Eureka precut cores I have purchased came in 8 pieces for the canard, plus 2 more for the elevators. The first step in the building process is to join the two main cores into one straight 9 foot (2.7m) piece.

Because these two pieces will form the backbone for the rest of the 11 foot (3.4m) canard, it is very important that they line up correctly when glued together. This might seem like a simple task, but due to the shape and size of these pieces, special handling is required. 

Let’s look at how I did this…

Firstly, one needs a big table. Mine has served many uses thus far, but I had specifically designed it with the canard’s dimensions in mind, and while it doesn’t have to be leveled, that always helps, so I spent some time making sure it was

Next, Gina and I purchased two fairly straight 2x4 beams twelve foot in length at Home Depot. 

Picking up a couple of 12 footers

I cut them to 130” length, and screwed them to my table parallel to each other with a 3.5” (8.9 cm) gap.

I stuck my 8 foot level between the beams, sat the left core on it, and put a few nails into the masked bottom area of the left core, then I did the same for the right one, and played around with them for a while to see how they’d align.

2x4s screwed to the table, bottom foam taped

Nails pushed into the sides of the left foam core. Foam core is thus suspended by the nails.

Checking how close the two cores are, after nailing the right core.

Since everything seemed to line up pretty well, I used hot glue to fix the left core to the 2x4s.

Nails are hot glued to the studs. Foam core is facing up.

After checking to make sure that the right core would still line up, I mixed some wet micro and attached the two together. I used every straight device I had to keep them aligned while I squirted hot glue on the nails to finalize this setup.

Foam cores microed together and alined

Checking the top (front) of the cores to see if shimming of the nails is needed

Both cores hot glued to the 2x4s

The next step was making the two inserts (CLI) that would hold the bottom lift tabs (CLT). If you buy these from the Cozy Girls, you need not worry about this step, otherwise you will have to pay attention, since the plans are… let’s just say a little misleading. 

The problem is that the holes drawn in the CLI picture on page 10-2 are spaced 1” (2.5 cm) apart, while the corresponding CLT tabs on page 10-3 call for a 0.6” (1.5 cm) spacing. 

While the holes in the CLT drawing are 0.6” apart…

...the holes in CLI are 1.0” apart

Perfect, so far!

This isn't going to work!

My predrilled CLIs are from Brocks (thanks Walter).

I am starting to doubt the drawing at this point

Ok, so the CLI drawing is wrong, and here's the reference as stated on CP #27 (Builder Hints - canard inserts): “The canard inserts (page 10-2) should be drilled to match the hole pattern of CLT (page 10-3)…”

Thant only took "a few hours" of digging to figure out (sigh!).

Using my ”rivet chooser” spreadsheet, I entered the thicknesses of the CLI  inserts and the K1000-4 nut plates, and got the name of the proper rivet to use and the recommended edge distance. Then I went to work on making two CLIs.

Rivet chooser available in the download section. As always, use at your own risk!

Let's make some canard inserts! (Dykem blue layout fluid)

I started by scribing the "recommended edge distance" from the rivet chooser spreadsheet

The CNC mill makes it so easy to space the holes 0.6" apart

All parts drilled and Alodined

So, the rivets go in from the front, and the nut plates go in the back...

...then, the AN426AD-3-5 rivets (selected by the "rivet chooser" spreadsheet) are squeezed...

...and the completed inserts are ready to be used

With the CLIs made, I cut two depressions into the foam, and built a support structure that I would use to find and reopen the CLI holes after fiberglassing the cores. To keep with my fuselage 2” (5 cm) enlargement plan, I also moved the CLI depressions in the foam outward by 1” (2.5 cm) left and right of centerline, to 9” (23 cm).

Moving the CLI inserts to ± 9" from the centerline (1" further than plans)

"Dremeling" out the CLI recess in the foam

Recess ready

This is how the CLI inserts will sit in the foam. I will fiberglass over them next time.

To help in re-locating the CLI holes after fiberglassing, a hole-finding jig is made.

Dry fitting the jig

The jig will help me find where to drill later on, to open up the CLI holes covered by fiberglass.

Last thing I did was to micro the tabs in place.

Semi-dry micro added to the recesses

I used shims to make sure the jigs held the CLI inserts parallel to each other.

This isn't super critical at this time, but should help later.

I stacked used hotel key cards to shim the inserts to the same horizontal alignment, measured with a level app on my iPhone.

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