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Saturday, May 27, 2017

Ch 10 - Canard - Part 13

Top skin (12.5 hrs)

Now that the VOR/LOC and GS antennas have been permanently mounted on top of the canard, I can finally apply the top skin consisting of 1 UNI, 1 BID, and 2 UNI.

As usual the manual is overly optimistic about how long this process should take. It specifies 2 hrs for 2 people. So, I took it to mean 4 hours for one person. From prior experience I learned to at least double that to 8 hours, a long day, but doable. 

I was very disappointed when I was nowhere near finished at the eight hour mark. Twelve hours after I started, I finally rested squeegee and paintbrush on the table, and went to bed with enough aches to keep me awake most of the night. Getting old sucks!

Let’s see how it went down…

In Part 8 I showed how I was able to get a very clean 1/2” (1.3 cm) of bare fiberglass at the trailing edge. This is a structural requirement and it is very important to the overall strength of the canard. I marked an half inch line along the trailing edge to make sure I would not encroach on this limit.

The trailing edge had been peel-plied, but it got sanded anyway as a precaution.

I then masked off every bare fiberglass surface that I did not want to contaminate with the micro-slurry I’d be using next, and started patching up dents and holes in the fiberglass with dry-micro.

Masking to keep micro balloons at bay

The process of removing the trailing edge peel-ply described in Part 8 left a step in the foam that needed to be smoothed out. I made a popsicle tool for this job which worked okay, though not perfectly. Nevertheless it proved sufficiently useful to be pressed it into service.

A little dry-micro fillet is needed near the trailing edge (hence the tape).

I had high hopes for this popsicle tool

It was designed to extrude the perfect fillet

Popsicle tool in action

Before and after popsicle tool use

Then it was slurry time!

Nothing new here, if not for the amount of surface to be covered.

It’s amazing how much surface there is on a canard. I bet the wings are going to be a real tough job!

Anyhow… I removed the tape, and revealed a perfectly preserved trailing edge and spar-cap just begging for some pure-epoxy, but first a little more masking would be in order to keep epoxy off the metal pipe, and from running back under the bottom of the trailing edge.

Trailing edge and spar-cap peel-ply removed

More trailing edge masking

After obliging the bare fiberglass requests for epoxy, I started laying up UNI. Glassing solo, the UNI laid up nowhere near the way I had intended, so I had to straighten up every individual fiber by tugging at it from other ends of the canard, and did my very best to keep the cross-fibers in line as well. This necessary attention to details ate up a lot of time.

First ply of UNI

Fibers straightened and edges trimmed

Seen from the other side

Next it was BID time! Laying BID solo made me wish I was back doing UNI again. This stuff really has a mind of his own, but I eventually wrestled it straight again. However, I had to do this four times due to the small pieces that get laid at a 45ยบ bias.

BID took forever to straighten back up

This stuff gets skewed just looking at it!

Piece #2 of 4

The front edge gets wrapped around the leading edge of the canard

Working the far end pieces of BID

To avoid a surface bump, these BID pieces are butted not overlapped.

Even then, I did get a tiny bump that I'll have to take care of during finishing.

I was glad to get back to UNI again, and worked on layup #3 and #4 next.

Approaching hour 9 I'm back to UNI (ply #3 of 4)

Hour 12, (ply #4 of 4) declaring a truce.

Mostly finished canard

After the last ply of UNI I peel-plied the ends since some tips will be added at a later date. I then copied my buddy Wade, and applied some dry micro to smooth the small kink on the trailing edge my popsicle trick hadn’t completely eradicated.

Dry micro fillet over the still wet fiberglass

Peel-ply will help when the tips get mounted.

I was pleased at how the cables exit from the canard turned out.

This spot is not aerodynamically active since it is buried into the nose

All fiberglass cloths were wrapped around the bottom of the leading edge of the canard for a distance of about 2” (5.1 cm). This effort was helped by the clear directions on the plans to overhang the canard off the bench, but hindered by having to be on one’s knees for a long time, working a paintbrush loaded with warm epoxy uphill, while the stuff runs over one’s gloves and onto the arms.

Time for curing at last

The last hour was certainly the hardest, and when it was over I left the shop without even cleaning anything up. A first on this build.

As I had to go to work early the next morning, it wasn’t until a week later that I was able to rip the canard off the jig, and trying it on the fuselage for a photo op. 

Canard pulled off the  jig
Trying the canard on for the first time
It's amazing just how big the canard really is

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