Chapter 13 Nose & Nose Gear

Sunday August 29, 2010

This chapter has a lot going on. The nose section of the fuselage is built up which is where the nose gear and retract mechanism reside as can be seen in the sketch from the plans to the right. I am deviating from the plans by installing an electric retract mechanism from Jack Wilhelmson. Almost everyone, including the designer, has upgraded to an electric retract mechanism, because it saves your back. With the manual mechanical system to extend the gear you first need to lift the nose of the airplane up yourself by lifting up on the canard and then manually crank down the nose gear and then you can get in the airplane. With the electric system from Jack Wilhelmson you flip a switch and raise the nose up about a foot or so climb in and then raise it the rest of the way. I've also selected the automatic extend option that will automatically extend the gear down when airspeed drops below 90 knots in case I forget to put the gear down before landing to avoid the embarrassing nose gear up landing. Fortunately for a canard airplane a gear up landing only results in a very fast stop and some cosmetic damage to the nose. With the engine in the back and fixed main gear there is no worry of a prop strike or any engine damage. Also in the nose section are the rudder pedals which are linked to the brake master cylinders and rudder cables. The pitot tube and static ports are also incorporated into the nose section which provide pressure signals to the airspeed and altitude indicators.

The first step in this chapter is to wrap the nose gear strut with two plies of BID at 45 degrees, but before you can do that you need to shorten the strut to the proper length and sand it down in areas where metal hardware is attached to ensure that they will still fit after adding the two plies. I had a cured flat piece of BID that happened to be two plies and cut some strips off of that to use as a feeler gauge so I would sand enough to accommodate the added two plies of BID.

Here is a picture of all the retract parts and checking the gap for two ply clearance. The parts from left to right are; MKNG-6, which is the pivot for the strut in the fuselage, emergency back-up battery to extend nose gear when main eletrical power is lost, Automatic Extend (AEX-1) black box, main jackscrew actuator, instrument panel gear switches/wiring, mounting bracket, nose down support in lieu of hockey puck, and nose wheel. Below, fitted to strut are NG-3 & NG-4 which the end of the actuator attaches to and at the end of the strut is MKNG-15A the hardware that lets the nose wheel caster. To steer the plane on the ground differential braking of the main gear is used by pressing on the appropriate rudder pedal with your foot and the nose wheel simply casters in the correct direction.


Here is a picture of the strut bondoed on nails in preparation for it's first ply of BID layup and then after two plies have been added with the hardware loosely attached, everything still fits!


The next thing to do is create a template for NG-30 with accurate locations of mounting holes for the actuator mounting brackets, MKNG-6 (strut/fuselage pivot) and rudder pedals. There are three holes required for the actuator mounting bracket, which I spent hours to figure out which were the correct ones on the M-10 drawing. I did an email archive search and found that Bernie Siu had the same dilemma. The plans say to use NG-51 as a template to accurately locate the holes but since I'm not installing the manual system I don't have an NG-51 and John Wilhelmson's installation instructions are written as if you're replacing the manual system with his electrical retract system. I should have realized that the dimensions for all the hardware are given somewhere in the plans in case you want to make it yourself and Bernie found it on page 3 in plain view, I guess I just need to open my eyes. So I made a paper template of NG51 and taped that to NG-30 on drawing M-10 and could locate the holes accurately for Jack's mounting bracket. Jack's mounting bracket has hole #1 predrilled and the other two holes are determined when the entire assembly is partially installed on the fuselage to account for build differences. Bernie Siu shows how to identify the location of these holes to ensure that the nose wheel ends up at the correct fuselage station Bernie Siu Chapter-13.


Wednesday Sept. 8, 2010

News letter 86 had a design change for the NG-30's so I incorporated that into the template. With the template made it was time to actually make the NG-30's. I followed the sequence of other builders and first laid up 4 plies of BID on two pieces of 1/4" H100 PVC foam and once cured stuck the fiberglassed sides together with doubled sided carpet tape. Then I stapled the template to one of the foam sides and cut it out on the bandsaw and drilled the holes with a drill press. After cutting through the 8 plies of fiberglass the bandsaw blade was toast and had to be replaced to cut the birch plywood doublers and aluminum inserts. Did the small 2 ply BID layup over the MKNG-6 pivot hole location with peel ply underneath. The glass and foam is later cut out on the opposite side of the peel ply to create room for the MKNG-6 pivot.




Sunday Sept. 12, 2010

So, the birch plywood doubler with the 1 inch square by 1/4 inch thick aluminum insert is floxed in place on NG-30. The three actuator bracket mounting hard points are made from 15 plies of BID that were laid up and cured, then the plugs cut out with a 1.5 inch hole saw resulting in a 1.3 inch plug, the plans specified 1.2 inch so we should be good. The foam was routed out with a Dremel tool and routing attachment in the identified locations and the 15 ply plugs were floxed in place. At the same time 4 plies of BID were laid up over the entire NG-30 and an 1/8 inch thick aluminum doubler was floxed over the aluminum insert and two plies of bid laid up over the entire doubler area, proud by 1 inch. Peel ply was laid up over the entire part and Saran wrap was put over the doubler area to keep the glass down against the beveled edges of the birch and aluminum doublers, the poor man's vacuum bagging solution, it works well in preventing the glass from lifting up which would allow air into the layup. It took Lynn and I about 3 hours to do the layup it was frustrating to get the glass to lay down against the beveled edges of the doublers even though I rounded the edges considerably.


Match drilled all the holes to 1/4 inch except for the two rudder pedal holes, waiting for the parts to make sure they need to be 3/4 inch, not sure how to drill such a large hole without ripping things up. Routed out the fiberglass and foam in the area where the peel ply was embedded. Since the edge needs to be beveled I first routed a 1/4 inch perimeter deep enough to remove the fiberglass and then routed out the area down through the foam to the peel ply. Pulled up the peel ply with a box knife which exposed the birch doubler and square aluminum insert. I still need to bevel or round the corner for a 2 ply BID layup over the area with a one inch overlap onto the existing glass.


Sunday Sept. 19, 2010

Did the two ply layup in the recess over the birch plywood and square aluminum insert. Rounded all the corners and made a micro corner to make the layup easier, yet is was still difficult and needed Saran wrap to get the glass to stick down.


Once that was cured I opened up the holes for the rudder pedals to 3/4" using a wood spade bit, the hole saw made the hole 1/16" too big on the scrap piece I practiced on. Received the rudder pedals from Dennis Oelman which are very nice, now I could confirm the hole size and how everything will assemble later. I also enlarged the MKNG-6 hole to 5/16" and then could assemble the NG-30 box with the actuator brackets and spacers and MKNG-6 pivot which allowed me to flox the strut (NG-1) to MKNG-6 shown in the picture below. The strut is clamped to MKNG-6 to squeeze out the excess flox and shimmed between the NG-30's on the other end to keep it centered as it cures. I used one of the rudder pedals (white rod) to support the other end of the strut. As you can see the clamps provided a good squeeze out of flox.


I also did the 2 ply UNI layup as called out in the design change of newsletter 86, will do the other side after this cures.


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