Ch 11.5: Canard Tips

Canard Tips...as in the tips of the canard, not hints for building.

Eureka cut foam tip micro'd in place

With the elevators in place, the canard can now get tips to finish out the ends.  The plans version have a swoop up at the ends that some people don't really like.  A simpler version just rounds off the tips to blend directly into the airfoil.  Unless you do something really weird, it's really about aesthetics here and not aerodynamics.  I think the plans tips give it a little character so I kept to the plans here.



Since I'm using the Eureka cut foam cores, I already had foam cut to dimensions.  Recall that when we installed the hinges, the L template had changed to hold the elevator at a 15 degree up angle instead of zero degrees.  Well your supposed to use that old L template again here again to hold the elevator in place at the zero degree angle.  The new L template isn't designed for that so you either have to make one or find some other way to hold the elevator in the right location.

Looking at trailing edge forward.
Using the plans template with sticky back sand paper
to carve out the tip shape.  Duct tape protects the canard and
elevator as you move it front to back. 

Sand to a "pleasing" shape
After attaching the foam blocks with micro, it's time to shape the top side.  I found it very easy by turning the curved template from the plans into a sanding block.  On the shaped end of the template I put sticky back sand paper past the point marked as the edge of the elevator.  On the flat end of the template I put duct tape to the same thickness as the sand paper to prevent the sand paper end from going too far into the foam.  By slowly moving the template front to back on the canard, while keeping the tape line at the edge of the elevator, I could let the sandpaper do all the work.  As I got closer to the elevator, I taped some craft sticks to the top of the elevator so that my sanding would flow straight back to the trailing edge and not create a drop down at the canard trailing edge to elevator junction.  Then I removed the craft sticks and gently faired the slope down to better match the trailing edge of the elevator.  I did the exact same thing on the other side and they both came out exactly perfect.

I also had to decide on how the leading edge of the tips would curve to the sides.  I randomly chose a big roll of tape I had as the template for the curve.  I did my best to mark a matching curve from the leading edge around to the side, sanded it to my liking, and then made a template of it to help me match the other side.  Worked like a charm.

Perfectly shaped canard tip - top side.

The top was then glassed with 2 ply UND glass turned 90 degrees from each other and left to cure.









Bottom side
I flipped the canard over and began shaping the bottom of the tips.  This is when I realized I probably didn't interpret the plans correctly when shaping the top side at the leading edge.  The plans are somewhat vague, but apparently I should have rounded the top edges near the leading edge so that the glass will conform around it and the bottom can overlap it.  I rounded the corner, looking at it from above, but did not round the top down to the side.  However, I think I like my way better.  It leaves a hard edge on the topside that blends into the swoop nicely.  Since I couldn't overlap the glass except on the very front, I had to make some flox corners along where the two glass edges would meet to ensure strength and durability...no big deal.  Just another way to do it.

Elevator hinge pin wrapped with
box tap and packed with micro.

Before glassing the bottom I had to decide what I was going to do with the hole where the hinge pin goes through the tip.  The plans call for putting some tubing there.  I thought I would use an appropriately sized straw.  I had some that were a good size but they were all neon colors.  I needed either white or clear just in case it showed.  As I'm writing this, the world is in the COVID-19 pandemic.  Restaurants are closed for inside dining so I can't just run into the nearest fast food joint to see what size and color straws they have.  I tried the grocery store but every one had the same thing, colored or colored stripes.  Nobody sells plain white or clear straws.  I did find a clear straw from a local Mexican food place we like that turned out to be a perfect fit, BUT...after installing it I realized the straw wouldn't stick well to the micro and ended up coming loose.

So, my plan B was just to wrap the hinge pin with thin box tape, wipe it with some Vaseline to keep it from sticking, and pack micro around it.  That worked pretty well.

Completed Canard Tips.  Yo can see the hard
edge running from the front all the way
back to the swoop.  Should be a little
unique out on the ramp.

The last thing I needed to do was to drill a hole near the end of each hinge pin so you have a way to pull them out, shape the end of the hinge pins to match the tip curvature, and then grind an area in the pin where a set screw is used in the elevator to lock the hinges in place.  This was all done without much drama. 

Now we have finished the canard tips.  Only one more thing to do to call it complete.

Onward!