Chapter 10 Chapter 10 is where we make the first flying surface; the canard


Practice

My first attempt at hot wire foam cutting. Not a disaster but I am glad that I practiced.
We had a little burn in at the joint between the whale tale and the airfoil
Canard foam core

We decided to cut the center core of the canard first. The logic being that any mistakes would not be to penalizing since this piece is not exposed to the air but is more contained within the fuselage. We learned a lot with this piece about correct wire temperatures, correct cutting speeds to avoid wire lagging, how to avoid burning in holes. It wasn't perfect but it wasn't bad either.

Here we have a slight misalignment of the cap spar recess between top and bottom. This will be corrected before putting in the spar plies. There is also some evidence of wire lag on the leading edge of the airfoil. Again, not a problem, because this part is not exposed to airflow. For the spar cutout, we went slower and it seemed to work just fine.
Actually, after making some horribly embarassing mistakes and ending up throwing away five (yes 5!!!) canard cores, I started making things correctly using a new set of templates. This was my practice and it was the best yet.
A typical cutting session. Lots of weights on the foam core to keep everything level and immobilized during cutting. Here I am following the plans to the "T".
Here are the core pieces after having the spar cap trough cut out and the leading edges cut off. I was slightly lazy in that I didn't redo the center section even though it wasn't exactly perfect. In fact, it was slightly oversize which should allow me to sand it back to size using the correctly sized outer sections as templates.

Best to make sure the table is straight before starting the process of joining the canard cores. With four measurements all giving 0.0°, I think it is close enough!
Here I have set up the aluminum sheets to properly locate the canard tab holes and nut plates beneath the tabs. I followed the plans exactly and didn't have to many problems. I didn't have a drill stop so I had to be very careful not to let the drill bit grab and pull its way into the nut plate and ruin the threads. In the end, I used maximum drill speed with minimal pressure to avoid the problem of the drill bit grabbing. Getting the silicone caulk out afterwords was not so easy. I must be starting to do things right because all six bolts went in without any problems whatsoever.
Here are the recesses I made for the nut plates. I purchased the nut plates from the cozy girls. Once again, excellent quality. I made the recesses using a rotozip tool. Seems like a pretty nice tool.
The nut plate mounted is flush and you can also see the joint for the middle and outer canard aft cores.
Shear Web
The passenger leading edge canard core. You can see that the reference lines on the leading edge of the shear web and the leading edge of the canard core are well aligned. For reasons best not revealed (!), I epoxied the outer panels on and then the inner panel a day later after the outer panels had cured in place. I used the bottom of the outer panels to serve as a secondary guide for the bottom of the middle panel. I of course also had the dowels which piered the shear web to line up the forward middle canard section.
Pretty much the same thing but for the  pilot side.
This is the end of the passenger side after the leading edge has cured in place. The reference line is very straight so I think I got these pieces on correctly. Lots and lots of time was taken to get these pieces done accurately. I hope it pays off in the future.
Lower canard skin
This photo shows where the canard extension has been added to the passenger side. I have also marked the +-45° angles so that the BI will line up well. Because my table was a little shorter than the canard (but still built as called out for in the plans!!!), I ended up having to support the canard caps with tongue depressors and nails.
Same thing as above but for the pilot's side.
This photo shows the end result of the lower skin application. It really didn't take that long to do this layup; approximately three hours. I peel plied the entire surface.

Almost all of the time was spent in making sure that the canard was well aligned with as little twist as possible. Even though the plans say that the canard has to be perfectly without twist, everyone knows that this is an impossible goal; one of the major deficiencies of the plans is the lack of tolerances in my opinion. In the end, the pilot side was nose down by 0.3° and the passanger side was nose down by 0.7°. Some rough calculations based upon comments of the Zeitlin mailing list show that this should produce approximately 6 lbf lift force differential between the two sides if I make no corrective actions.
Instead of the PVC tube for trailing edge support, I elected to use a long piece of fiberboard which I ripped using my table saw. The quality of PVC tubing that I could find in France was nowhere near as good as what could be made by ripping a support as described. I then went back to the plans and made blocks of wood to lift the canard off the table and give support once it is flipped over. This worked out pretty well. I also made an adjustment in the blocks to match the offset in the canard. In other words, the angle of the blocks ranges from 0.7° to 0.3° so that when they sit flat, the canard will have "zero" twist. I am trying to be careful on these angles but maybe a little to careful. If I raise the nose by 1mm, that causes approximately 0.2° angle change. Trying to keep to 0.1° implies an accuracy of 1/2 of a mm over the length of the canard. Compare this to the surfaces on a cessna which has no where near this level of precision on the outside skin. Not an excuse for poor work but at some point you to have to give up on perfectionist tendencies.
Just a slight closeup showing my substitute for the PVC. The long line in the front corresponds to 2 inches from the leading edge.
Here I have flipped the canard so that the top side is up. You can see my tongue depressors which I used to hold on the canard tips. You can also see the protective duct tape and the shear web. I was very happy to see all the supports seat nicely on the work table.
One of the problems that I have been dreading. As I showed earlier, I changed my technique slightly in order to get more repeatable canard cores. The center section shown in the upper left of the picture was made using my old technique which resulted in imperfect cores. Here there is a misregistration of about 1mm. This should be easy to sand to the correct profile but thank goodness the majority of the center section in non-aerodynamic. In fact this is the reason that I decided to use the imperfect center section. Of course, this registration error is there from the leading edge all the way to the trailing edge. The outer cores are "perfect." At the other juncture between the outer and center cores, there is no registration error. 
Another little thing to watch out for, underfilling of a joint. Here, I did not apply enough dry micro to completely fill the joint. There is about 1-2mm of underfilling. Easy enough to fix but it would have been nicer to do it correctly the first time.
Here is Olivier helping to remove the misregistration between the middle canard core leading edge and pilot canard core leading edge. The pilot's side is correctly contoured, the middle is a little thick on the top side. Most of the middle of the canard is covered by a fairing so its precision is not so critical. Nonetheless, no one likes to work for years on a plane and be embarassed by poor quality workmanship whenever an access panel is removed. Soooooooo, we decided to work on it until it was right.
Here we are cutting off the famous whale tail. This was complicated by all the retaining tacks to hold in the peel ply. I also became a little impatient and broke a hack saw blade by bending it.
The whale tail has been removed and is no being contoured. I constantly used the contour template to make sure that it was correct. The long permagrit sanding block was absolutely essential in this operation. Made sure that there were no dips in the contour. Fixing the contour later would be a real pain in the tuckus so we took our time and made sure that it was done correctly. Nonetheless, some of this will have to be recontoured when I remove the peel ply so that I can establish a glass to glass contact. Removing the peel ply will also remove some of the foam which will be filled in with micro later on after all the glassing has been done. (don't want micro between the glass layers; the goal of the peel ply use was to allow a glass to glass contact)
Just a picture of one of the better tool purchases that I have made. The permagrit sanding block and fein multimaster in the background are worth their weight in gold.
Most of the contouring has been finished. I used duct tape (although this is supposedly really called duck tape according to the philologist on hot for words) to protect the foam. I am being as careful as possible to avoid putting big nicks in the foam.
The registration problems have been solved!
Pilot's side of the canard showing the whale tail has been removed and properly contoured.
After the whale tale has been removed and the canard profile verified, I put in the upper spar cap. Really not much of a story to tell, went exactly the same as the lower spar cap. All in all a pretty easy operation. The only problem is that it is practically impossible to get the profile correct. I definitely did not want to overfill and then try to have to sand the profile to shape. I preferred to have an ever so slight underfill (1mm or less) and then get the correct profile using micro but only after the upper skin was applied. I DID NOT WANT MICRO BETWEEN THE UPPER SPAR CAP AND THE UPPER SKIN!!!!! I ended up having some very slight sanding to do anyway and I put on a bunch of duct tape to protect the foam so that i wouldn't dig a depression in the foam next to the spar cap since the foam is so much softer.
Before putting on the upper skin, you have to remove the foam from the trailing edge to ensure a glass to glass bond. This was kind of scary because you are ripping away something which already has a very nice profile. In fact, there is a lot of foam which gets ripped away; a fact which in my opinion is not emphasized enough in the manual. After this is done and the foam core/upper longeron combination has been checked for a correct profile, there is not much left to do except put on the upper skin. This is a pretty simple operation but having two makes ensuring the correct angles a lot easier. Wrapping the leading edge around the bottom was about the only hard part since that had to be done almost blind.
Of course, you may want to have an antenna on the canard which usually is installed before the upper skin. I did the fairly normal installation. Some have been suggesting making a channel and lining it with waxpaper so that the antenna "floats" and is not subject to mechanical loading as the canard flexes up and down. This is bunk and should be avoided. The small stretch in the canard during maneuvering is insufficient to cause an antenna failure. On the other hand, making a channel is an invitation to an unfavorable stress redistribution. Probably not enough to cause a problem but why make a lot of work to solve a non-problem and in the end introduce a potential problem? You can also see the high density foam (little yellow square just behind the longeron) to anchor the elevator hinges later on.
Here I am verifying the profile just prior to putting on the upper skin. Looks pretty good actually.
Here the upper canard skin is in place. The correct profile has been achieved by putting micro on after the upper skin was in place. The blue foam piece at the trailing edge was to make a small dam to keep the micro in place as I filled the trailing edge glass to glass joint to achieve the correct profile.
The trailing edge profile has been achieved. Just have to knock off my dam and move onto chapter 11 which promises to be a very short chapter.