QuickTalk 20 - Q-2 HINTS
- Category: Q-Talk Articles
- Published: Thursday, 28 February 1985 06:11
- Written by Jim Masal
- Hits: 2179
From Mike Sullivan G-BKSK
Three of us built a Q-2 in London, England and after 100 hrs of flying, often from runways which are, by American standards, extremely short, we think we can offer some useful advice to those who have not yet flown or have flown and broken a canard in the process.
The builder who flew our maiden flight ad subsequent test flying has high hours in a variety of types including high wing loading jobs like the Spitfire XIV, Sea Fury and the notoriously tricky Paris executive jet. His first Q-2 landing was a greaser like all his landings since. Riding with him as a passenger, after several high-impact attempts to land the thing myself, I worked out the reason why. He nails the approach speed with great accuracy, right down to the ground, and he FLARES WITH POWER. At gross or over, especially on shortish runways, he uses a strong, though brief burst of power to check the descent.
We think the high number of broken canards reflects a characteristic for which the kit literature leaves the builder quite unprepared. Power off approach speeds set up such a high rate of sink that the elevators up front, already busy providing extra lift, do not have enough authority left to check the descent when it comes to flare-out time. You MUST use power, particularly when there are two abroad. The Q-2's drag-free airframe gives you instant response to it.
The Q-2 is not just a tail first airplane. The canard is not only providing pitch control with its elevator, it is also lifting the greater part of the weight. At approach speeds, the elevators are functioning more like flaps, providing extra lift, and as with flaps, you will sink like a stone if you retract them in the air at low speed. Once you have fed in back stick/down elevator near the ground, you cannot afford to change your mind about it. Hold that back stick, whatever you do, and get yourself out of any difficulty with power. If you are tempted to check forward on the stick near the ground to make up that little bit of lost speed, you dump lift with great efficiency and ...CRUMP! You get the same expensive noise if, at the correct approach speed, you try to flare without feeding in a little power. GREASE UP THAT THROTTLE AND USE IT!
Of course you can postpone all that hassle on a long runway by flying on at well above approach speed and taking a mile to settle and stop, but if you don't develop the right technique your Q-2 will bite you sooner or later. We check the pitch-buck speed on the downwind leg, and add 10 mph and that's our approach speed. We would have broken OUR canard if one of us did not have above average flying aptitude, but now the two remaining low timers know the score we are converting to our Q-2 without tears.
From Bruce Patten #2512
JIGGING THE FUSELAGE: This step usually stops the first-time builder cold, so I'll describe how I did it. There may be a better way, but this will get you started.
Before jigging you will need to rough trim the fuselage shells. You can feel the mold line near the edges with your fingernail; highlight this with a marker pen. Now trim to within 1/8 inch or so of this line. Leave some to allow for match sanding for a good fit of the mating edges. Don't trim for the firewall yet; do this later after the firewall is stuck in its proper position with micro.
When cutting out the fuselage jigs, you can save some waste by shortening all of the jigs by 2 inches from the top right away, as the full height will interfere with glassing of the seams later. By attaching the jigs to a low table (or even a ladder laid on the floor), the WL can be adjusted later. Set the bottom shells in the jigs, and set up a post at the front and the tail with a string stretched between. Locate the front end of the string 2.9 inches above the split line at the firewall, then move the other end until a line level hung on the center of the string reads level. Now check to see if the tail end split line is 1 inch below the string. If it's low, shim the tail end of the table up; if high, you'll have to shim the front end of the table a corresponding amount, then start over. Once you've got it, make sure you're level across the bottom shells, then Bondo everything in place. You no longer need the string at WL 15, but before removing it, mark the WL 15 elevation on the post for later reference.
Now set the top shells in place, and after they fit together well, run the string again, only this time above them. Measure back along the string from the firewall, drop a needle on a thread, and mark the top center locations of all the bulkheads. Drill a small hole at each mark, and stick a small nail through. This provides a positive stop for locating the bulkheads inside.
Now that you know the location of the seatback bulkhead, you can lay the canopy in place and proceed as per Q2BT#39. With the forward extent of the canopy established, Bondo a wide board or piece of plywood to the top forward end of the top shell so it is level in both directions. This will facilitate re-leveling the top shell after removal and makes a handy shelf for tools when working in the cockpit.
This is good time to start on the tail disconnect fittings while everything is jigged in place. Layup a 3-inch and 6-inch BID tape over the tail split seam on the top shells. Stick the top half of the seatback bulkhead in place with micro. Flox the canopy in place per Q2BT#39. I held the back edge in place with a ratchet strap cinched around the fuselage. The front edge was held down with aluminum tabs clecoed to the top shell. The holes are covered by the BID tapes around the front of the canopy after the flox has cured.
After all of this has cured, removed the top shells and set them upside down on your workbench. Install the FS175 bulkhead in the top shell. Leave out FS120 for now. Layup the inside tail disconnect reinforcements on both the top and bottom shells. Do the BID tapes on the back of the seatback top half. Also do the tapes around the front of the canopy on the inside. Install the aft canopy bulkhead. Flip the bottom shells over and layup the 3-inch and 6-inch tapes over the tail split seam. Once all the aluminum tail disconnect tabs are drilled in, the front and tail shells can be sawed back apart, although it might be better to glass the tail top and bottom shells together on the outside first.
Set the front shells back in the jigs and level them up. Measure back from the seatback bulkhead to locate FS94 bulkhead, and attach it to either top or bottom shell. Install the bottom half of the seatback bulkhead, but don't connect the two halves yet. The idea is to avoid permanently attaching the top and bottom front shells until you absolutely have to, as doing the gas tank, canopy lip, header tank, etc., is a lot easier that way. Also, hold off on the firewall until you have your engine, if possible, since the magnetos you end up with may not fit the magneto box on the plans.
The turtle deck can be cut out for final installation now that the bulkheads are there for reinforcement. Refer to QUICKTALK #9 for a hint for making a pattern for the hole. Measure up from the WL 15 mark on your post and make a mark at WL 30. Use a water level to transfer this elevation to both sides of the fuselage at FS 78 and FS 94. Draw a line between the marks to establish a wing level line. Match the level line on your paper pattern with this line and trace. The cutout for the new canard can be done the same way, using WL 1.462 for the level line.
I found glassing the inside seams of the tail shells not as bad as I expected, but then I'm a 98-pound weakling and I left out the FS 120 bulkhead til later. A fluorescent droplight taped against the outside of the top shell just ahead of FS 120 provided plenty of light without a lot of heat. This was done horizontally with the shells in the jigs. After installing rudder cable fairleads through FS 175, install the FS 120 bulkheads.
From Roscoe Turner #?
When I was sanding (scuffing the surface) to put in the header tank, I accidentally sanded too much. It didn't show up until I had the tank in and tested for leaks. I had a leak that went in between the pieces of foam in the shell where they are edge to edge, around and down and back inside the plane 6" below the tank. It was easy to stop the leak, but other than pulling my tank out and coating the shell inside, I am going to carry a teaspoon of gas in between the layers of glass of my shell.
Be careful sanding and as a precaution, coat the entire inside of the shell where it will be inside the tank.
ED. NOTE: Good advice! A buddy building a KR-2 once showed me a nice 3-ply glass layup that passed water almost like a sieve. I also heard about a guy who installed an aux tank over his Q-2's main wing behind the seatback and one day found that a leak had penetrated into the wing and had started eating out the foam core. DON'T SAVE WEIGHT ON THE INSIDE OF YOUR TANKS. SPREAD LIBERALLY WITH EPOXY. I even allowed my epoxy to start curing and then spread the thick goo around with my squeegee.
From Bob Falkiner #2015
LS(1) mod canard construction: It is almost impossible to use the level lines on the slot cores for alignment because they are only 1.5" long, and this introduces a significant angle error/uncertainty. This is more critical than on the old canard because there is no flat shear web to use as a reference point. It would be easy to make a several degree error on elevator attachment angle. This MIGHT not be critical, but I didn't feel like finding out by trial and error. I found it much easier to construct the elevator first, and jig it in place using a female wing template drawn up using the hot wiring templates. The slot cores are added last and treated as a fairing, as per the option in the plans. The two-end elevator attachment points were done in one evening per wing with the elevators jigged with foam scraps, so proper alignment is assured. The center (midspan) hinge was added later. Caution: advanced planning is necessary on the midspan assembly of the elevator to ensure that you can get +/- 17 degrees travel AND BE ABLE TO REMOVE THE ELEVATOR AFTER THE CENTER ATTACHMENT POINT HAVE CURED. Results are good, and I am assured that my wing has the correct planform over the whole span.
From Saylor Milton #2484
1. The old pre-molded wheelpants CAN be re-shaped for the new canard. I used them and they are looking good.
2. Make sure that you can remove the wheel without taking the brake caliper apart.
3. As you would normally make the wheel pants upside-down, make sure that there is enough upsweep at the back so that the fairing doesn't drag on the pavement when taxiing. I didn't and it cost me a lot of extra time.
4. I made the caliper brake cover the following ways: with the brakes assembled and installed. I used Mylar tape to cover the exposed parts of the caliper. Then I poured out a small quantity of mixed X-40 type expanding foam on a sheet of waxed paper and when it expanded enough to be fairly stiff, I slapped it on the tape covered, exposed brake parts. After it cured, I sanded it to the shape I wanted, and laminated 4 BID over the stiff foam. You need to mask the parts of the wheelpant with the Mylar tape so that the lamination does not stick to the pant. After the lamination has cured, pop off the layup, remove the foam, rim and sand to shape. I fastened the cover with AN 525 bolts with nutplates mounted inside the pant. You could make both brake covers at the same time, but I found it hard to make them identical so I made a mold from the first one with X-40 foam and laminated a duplicate.
5. Be sure to roughen up the brake disc pads. You won't get enough friction to stop if you don't.
6. TIPS FOR ARM RESTS AND CENTER CONSOLE IN THE COCKPIT (or the box office, in the case of female pilots): I am going to screw down the top of the center console rather than bond it down permanently. To make the screws hold, I Dremel out some of the white foam from the edge of the pieces and fill with flox. When hard, it can be drilled and screw tapped.
7. RUDDER PEDALS AND CABLES: The plans call for the rudder cables to be directly attached to the pedal. To prevent my feet from getting in the way of the cables, I brazed an L-shaped piece of 1/4" steel pipe to the pedal so that it is much closer to the inside wall of the fuselage. I have dual rudder pedals, so the same was done on both sides. The pedals are made of cad-plated steel, not aluminum, so it's easy to braze or weld the extension.
Also, it is much easier to install the rudder pedals before bonding the top and bottom halves of the fuse together.
8. The plans call for a bulkhead that looks like the letter B on its side, with cut out holes that are much too small to service the battery, adjust linkage, or store any practical luggage. The inside of my seatback bulkhead looks more like the letter C. The middle of the C is permanently bonded to the center console, but the inside of the C is removable for easy access to the back. The top part of this bulkhead is reinforced with a foam ridge with BID laminations over it.
TEMPLATES AVAILABLE: For a small donation, (whatever it's worth to you), I will send a gas tank installation template for the pre-molded gas tank to anyone who sends me a SASE with a sheet of rather stiff paper (like butcher paper) measuring at least 43"x31". This includes a tracing of the baffles, a template of the magneto cutout hole in the firewall, and installation templates for the header gas tank. Send to Saylor Milton, 1100 Cliff Ave., Fillmore, CA 93015.
We have a 3200' runway. Not long enough to liftoff and land. High speed taxi braking was a problem. I tried 2 handle braking, changed to 1 handle, then to toe brakes and back to 1 handle. I finally got in trouble and hit a runway light and ground looped to break off the tail. That did it.
Now I am trying to build a new style canard. I also want to make a three-wheeler this time, or bring the wheels in like the Dragonfly for a tail dragger. I have a design of my own which I am not quite satisfied with and would appreciate knowing what other guys are coming up with.
Cal Hansen, Osseo, MI
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