Ch 12.2 Canard Mounting - Aligning the Canard

Can I be straight with you?

Let's hope so.  I don't want my Cozy to fly crooked!
The next step is to align the canard properly so the mounting holes can be located and drilled.  This involved matching the center-line (C/L) of the canard to the C/L of the front bulkhead...which if I've done everything correct so far should actually be the C/L of the airplane.  Wouldn't that be great!

Level

I first carefully leveled the fuselage from side to side.  Since it's sitting in the garage sideways and the floor slopes to the door, I just placed 1/8" pieces of panel board under the starboard tire until level and chocked the wheels.

Level

Next I leveled it front-to-back using a stool, blocks of wood, and some 1/32" hotel key cards until it was level.

Level

Lastly, I had to ensure the F22 bulkhead was level.  This required a small bit of sanding to get the top level...no problem.






Fast forward past installing/removing the canard a dozen times...

119.25"

119.25"

Once level, checked, and rechecked, I now had to align the canard square with the center-line of the airplane.  You do this by measuring from a common point on each side of the canard to the C/L at the firewall in the back.  I haven't built the top portion of my firewall yet because I wasn't yet sure if I was going to enlarge the rear turtleback or not.  So in it's place I used a spare scrap of wood, aligned it where the firewall would go, found the center-line, and placed a screw there to measure from.  In the pic above you can see the wood scrap (stick) at the back.  For my measurement point I picked the inside corner intersection of the canard and the canard tips.  After aligning I found I was going to need about 5 plies of BID added to the starboard side mounting point on the F22 bulkhead to get it square.

Checking the
Incidence

Next I checked the canard incidence...the angle the canard sits on the aircraft.  As predicted in the plans it was a few degrees off necessitating removal of some of the top of F22 and fuselage sides under the canard.  Additionally, the incidence measurement was different depending on where I measured due to some variation in the canard surface.  To solve this I built multiple copies of the E template (bottom of the canard) which when built properly places the canard at 0 degrees incidence.  I sat the canard on the workbench (which is level) in the templates and used templates F & G to find spots along the canard which were at 0 incidence.  This should work in theory because the top of templates F & G are supposed to be be level when properly fitting to the canard airfoil.  I marked multiple places on the length of the canard where I felt the incidence was accurate and used those spots to check my incidence when installed on the plane.  I won't know exactly how this worked out until I do the finish work on the canard and see if canard profile comes out exactly as expected.  At worst it shouldn't be off more than a small fraction of a degree.

Under the canard...Lift tabs
at a slight angle to F22.
A little flox to the rescue.

After finally getting the canard sitting level, centered, aligned and at the proper incidence, I could check the lift tabs to see if they were flat with F22...there were not.  You can see in the pic to the right that the lift tabs are at a slight angle to the front face of the F22 bulkhead.  This goes all the way back to Chapter 10 in the first step of building the canard.  There is no real guidance on how to align the canard cores vertically between the 2x4s when you assemble the cores and that drives the angle of the mounting points for the lift tabs.  Thankfully it's not a big deal to adjust.  

Canard installed while flox pads cure
Definitely looking different than a boat now!

I removed the canard, taped up the lift tabs with box tape, laid down 5 plies of BID on the starboard side of F22 and 1 ply on the port side.  I only put BID on the port side to give a good foundation for a flox pad to fill the gap formed by the angle to the lift tabs.  I set it slightly below the top so it didn't affect the alignment.  After cure #1, I ended up having to sand down the flox pad a bit and redo it...the canard moved slightly during cure and threw off the incidence.  In the end I got it all set, cleaned up the excess flox and set about building the incidence tabs.

Holding the incidence alignment

Incidence tabs epoxied in place

Incidence Tab Front

I built my incidence tabs out of 1/4" birch...remnants from the firewall bottom.  There was so little of the alignment tabs touching the TE of the canard that I doubled the thickness on them.  I cut out and shaped the birch into four identical tabs and then epoxied two each together for 1/2" thick tabs.  I established the proper height using pencil cross marks on the face of the tabs that corresponded to the center of the alignment pin holes I already drilled for the AN3 bolts.

Incidence Tab Aft

Next was two simple layups to add the 5 ply BID running from the canard top up the forward side of the tabs and then the 4 ply BID layup running from the bottom of the canard up the aft side of the tabs.  Once completed I drilled out the hole to the required 1/4" size however I didn't drill it all the way through the tabs.  Since my tabs were 1/2" thick and the CN-2 bushing that gets installed from the aft side wasn't that long, I only drilled out enough to fit the bushing in and left the rest in the front at 3/16" to match the AN3 bolt that will exit.  Also, I chose not the epoxy the CN-2 bushing in place.  They were a nice press fit and can't come out with a bolt through them and if I have to change the incidence later, I won't tear them up getting them out.

(Update 9-15-21) So after being away from the project for a good while I went back and rechecked my work and found that something wasn't quite right.  It looked like my center point at the firewall might not have been quite in the correct spot and a little off the mark can make a decent difference.  I spent time re-locating the center point, checking, re-checking, etc.  Once I did that I found the canard was a bit too far aft on the starboard side.  I added a few plys of BID to F-22 at the lift tabs and everything checked out.  realizing there could also be a slight difference in the location of the canard tips between each other due to simple build precision, I also added another measurement point on the canard by dropping a plumb bob over the leading edge directly in line with the inside edge of the canard tips.  I was able to get all point to match on both sides of the canard so I know now it's square.  

What I couldn't figure out was why one side would need plys of BID to get the canard square when all the bulkheads fuselage location seemed to match perfectly.  Then it hit me that the only way that could happen I think is if all the bulkheads were slightly out of square the same amount all the way down the fuselage. In other words, when I assembled the fuselage bulkheads to the fuselage sides, whichever bulkhead I measured from to align everything had to be ever so slightly off square and that propagated through the other bulkheads.  I'd need to measure relative to an independent point off the fuselage to confirm this, but that has to be what happened.  In any case, that little bit will never be noticed and shouldn't have any affect in the finished product.

Lift tabs (bottom of canard) and alignment tabs (top of canard)
(Notes: At this point I still needed to flox in the incident tab
nut plates and enlarge the lift tab holes to AN4)

Only one more major thing to do to finish the mounting....trim the inside elevator edges to fit.

Onward!