Ch 10.6: Canard Top Spar and Skin

The 1st Lifting Surface...for the 2nd Time !...continued


Ok...Canard flipped.

Canard...now right-side up.

After re-jigging the canard and turning it over, it was time to set about prepping it for the top spar and skin.  I removed the fishtail per plans and began to remove the 1" strip of peel ply laid at the trailing edge.  This proved to be extremely difficult and time consuming!  The peel ply did not want to be removed.

If that wasn't bad enough, it was difficult to tell when the peel ply was fully removed and there was only glass remaining.  See a tip on the previous post about a possible way to prevent this.  Perhaps a different peel ply would work better.








Elevator Hinge Hard Points

Hard points in place and curing.  After cure
the excess above contour is cut off.

Next I cut and installed the more dense foam (6 lb / cubic ft) used for the hinge hard points.  I marked the locations and used a Dremel tool to auger out the foam.  The plans were a little vague on the fore/aft location of the hinge hard point foam.  I settled on a position about 1/4" below the spar cap down to about 1.3" from the trailing edge.



Micro Fill the foam gap...

Hinge hard point sanded flush and micro
filling the transition to the trailing edge.
(Note the TE is preserved for glass to glass bond)

When pulling off the peel ply you pretty much destroy the foam just in front of the clean trailing edge.  Since this would have been foam anyway, I went ahead and filled the area with micro and created a smooth transition from the contour to the trailing edge.  I reserved .6" of clean trailing edge glass for the glass-to-glass bond (hash marks).  The FAQs say to leave no less than .5".  After skinning I"m sure this area will need some additional external micro to bring the full contour back to where it's supposed to be.
NOTE:  After assembling the elevators, I believe the B.L. 15.6" dimension for the inboard hard point shown in the plans should be 15.7".  See my post on Ch 11.4 for my explanation.


Top Spar

Ready to roll...or.."un"roll as it were.

Since I laid up the bottom spar, Aircraft Spruce has starting sourcing their spar tape from an Australian company named Colan.  Marc Zeitlin checked it out and gave it a rave review.  I ordered this new tape for the top spar.  I was able to get 13 plys of spar tape into the top spar trough compared to 12 on the 1st canard.  This took me ~9 hrs working alone.  Below are the layer lengths I was able to get.

Layer     Length each side of center
1                        62.5
2                        62.5
3                        62.5     
4                        58.5 
5                        56.5     
6                        50.5           
7                        50.5
8                        46.5
9                        44.5
10                      34.5

11                      30.5
12                      28.5
13                      18.5

A total of 33.7 yards of spar tape was used on the top spar cap.  All total I used 53.3 yards of spar tape for the 2nd canard...about 3.5 more than the 1st canard.  Not a significant difference however my technique was better and I tried do a better job this time of not overfilling the contour too much and having to sand.  Although I still had a few small high spots to sand, it was very minor compared to the 1st canard and thus I'm very happy with canard #2.   I suspect my first canard may have been perfectly fine, but I didn't want that unsure feeling on such a critical part.  I'll call the 1st canard the "practice" canard...although it was an expensive way to practice.

TIP:  The plans call for ordering 42 total yards of spar tape so buy extra spar tape!  You don't want to be in the middle of a spar layup and run out.


Skinning the Top

Placing the 2nd ply (BID) on to the canard.

Skinning the top went according to plans with no issues.  The only added complexity here is that you have to be sure to end each ply in a different spot around the leading edge to properly taper into the bottom and not leave a bump.

When finished, I did find these air bubbles you see in the picture at the right.  These are not in the glass itself but mostly just on top of the glass, between fibers, just under a thin coat of epoxy left by the peel ply.  They are a result of a poor peel ply job done after ~9 hrs of spar cap layup...I was tired.  After confirming this with the experts in the forum, I was happy that this was no issue and has no impact on the finished product.


At long last, this completes Chapter 10.  If you've been noticing the dates on these posts don't interpret those as having anything to do with how long this work took.  1st, sometimes it takes me a while to write a post for something I did a while back.  2nd, I've had numerous breaks in building over the years as normal life and priorities get in the way.  I will say though that I did have some trepidation in getting those spar caps done again which caused me to procrastinate a while.  I now have some momentum and hope to keep that up.

I can finally move on to the ups and downs of the elevators.

Onward.