QuickTalk 18 - QUICKIE HINTS
- Category: Q-Talk Articles
- Published: Wednesday, 31 October 1984 06:11
- Written by Jim Masal
- Hits: 2070
From Norman Howell
1. (page 7-12) In order to have a smooth transition from the canopy to the aft fuselage, the area just under the wing at about FS 78 must be carefully faired into the carving and contouring at the longerons. The thing is to avoid the fuselage sides extending very far outboard of the seatback bulkhead or FS 79 at WL 30.
2. (page 14-6) I built a female mold to make my forward and aft fuselage covers in the same manner as Dragonfly builders make theirs. Heat forming is more difficult and results are not uniformly great. I laid up the interior glass on my foam/mold first then laid up the outside with the cover in place on the fuselage. Worked great.
3. (page 14-4) The plans show the CS 5/CS 12 rod end bearings attached to the CSA3 bellcrank with the bolt heads on the opposite side of the bearings from the bellcrank. This is wrong! NEVER cantilever a rod end bearing off a nut - the threads can fail. Reverse the bolt so that the head is forward. See also CANARD PUSHER #30, pg 9, LPC #81.
4. (page 15-3) I did not have any trouble with the Bondo and stick method of bonding the canopy to the stiffners and aft canopy bulkhead. However, resist the urge to use 5-Minute to "help" the Bondo. Bondo chips and sands off easily, but 5-Minute will cause glass debonds when you remove the wood.
5. (page 15-3) Plan ahead on your hinge placement and stiffner length if you plan to mount the instrument panel to the fuselage rather than canopy. You don't want a wood insert to wind up forward of the panel.
6. (page 15-6) Watch out! If your forward canopy hinge screws are under the cockpit cover instead of protruding through the stiffner, you may wind up with bumps on the fuselage as you attempt to fair in the nuts.
MS 20001 P4 hinge is extruded and is stronger than the rolled hinge in the kit, but it's about $8 a foot (yipe!).
7. (page 15-8) You can make pretty nice bends in the stainless secondary latch if you use something flat to bend the metal in your vise. I used a piece of 2" wide aluminum bar. Stainless is a bummer to drill; don't let the bit rattle in the hole or heat up...keep it cutting.
From Will Hubin N142WT
Terry and I have made a number of changes to 142WT that may be of interest.
1. We were getting a belly full of oil for every hour of flight recently (starting at about 175 hrs. of flight time); a new gasket and sealer on the bolts for the rear cover seem to have cured the problem.
2. We had our engine spacers significantly more compressed than suggested in QUICKTALK #16. We replaced them with new rubber as per spec. and found the in-flight vibration levels considerably reduced; specifically, the instrument panel now has negligible visible shake at cruise.
3. We finally found a prop which does a better job in climb than the stock 42x30 Cowley that we had. Recall that we tried QAC's 44x27 climb prop earlier and recorded poorer climb and cruise performance. The new prop is a 44x22 Ritz and it gives about 160 rpm more and perhaps 30% more climb rate at 70 mph IAS. It was about 100 rpm lower on static, however, indicating stalled blades. Full throttle with this new prop gave us 3660 rpm and 110 mph indicated vs. 3350 and 110 mph on the Cowley...although I think we are closer to 18 hp than 20 hp right now (Ed. note: Ritz died not long ago in the crash of his Ritz Special so these props may no longer be available).
4. We have sanded our canard as Gene Sheehan recommended at last Oshkosh with the hope of reducing pilot stress in rain. Unfortunately we haven't had a chance to try it out yet, but I'm not too hopeful (Terry prefers "glistening" to "satinized" but yielded to my pleas for mercy).
5. We raised the ailerons 2 additional complete turns (about .2" above neutral) and found that the machine's flying behavior was amazingly altered. For one thing, on the landing flare it became a normal taildragger; it would abruptly quit flying when it got to the fully three-point attitude, and transition to a solid-feeling landing roll. Unfortunately, climb and glide performance also was noticeably reduced; evidently the higher angles of attack for both airfoils is causing a significant decrease in L/D.
(The lift distribution between the wings is determined mostly by the CG location, which hasn't changed, but the increased angle of attack of the GU gives it a greater negative pitching moment - according to fig. 4 in Report No. 6802 by the U. of Glasgow - which will cause the canard to be MORE heavily loaded than before. But the negative deflection of the elevator in cruise has an OPPOSITE effect; I don't know which is stronger so I really am not sure which way the lift distribution changes. The L/D of the GU seems to be very sensitive to loading; I've always noticed how strongly the speed is reduced in a steep bank, for example.)
The aileron reflexing resulted in a steep nose up trim change and a distinctly higher location for the elevators in cruising flight, as before. The Quickie is amazingly sensitive to the relative angles of incidence to the two wings! If this tiny change in aileron position makes so much difference, it is no wonder that Quickies and Q-2's fly so differently. The Dragonfly must have similar sensitivity and an even greater tendency to boomerang down the runway, based on the story in the last Homebuilt Aircraft magazine and the new landing gear location that premiered at Oshkosh.
The propeller/speed date given above were with the aileron reflexing as above. Since then, we have backed off one turn to about 1/8" above neutral and found what seems to be a suitable compromise between landing and climb performance for our machine. We are going to see if we can fit an in-flight reflexor, for it seems certain we could use it.
For a couple of years we have been using a bastard tach composed of a Westtach tach minus its galvanometer movement replaced by a digital voltmeter integrated circuit and a liquid crystal display. The combination worked beautifully for quite awhile but then changed its calibration. Now we have installed a new digital tach that I'm really happy with...The present unit is thoroughly digital as it merely counts the number of ignition pulses over each second and displays the count after multiplying it by the proper number to yield rpm. Since the counting time is crystal controlled, there is every reason to believe the unit will retain accuracy equal to its + - 10 rpm resolution.
The above circuit appeared in my article "Digital Autotach" which appeared in the summer 84 issue of HANDS ON ELECTRONICS, published by Radio Electronics. IC #3, a 4027, is replaced by a 4018 to use the circuit with the Onan, as shown in fig. 4 (mislabeled as fig. 3) in the article. The circuit in fig. 1 is for a 4 cyl. engine such as the Revmasters; I have checked it only on a 4 cyl. car engine and a magneto powered motorcycle engine. Electronic tachs can be dangerous if not wired properly or if they don't have the proper input circuit, since any short between the two signal terminals - coil and ground - will stop the engine.
I will send a copy of this article for a stamped, self-addressed envelope. Also, I can supply the smaller 0.3" 3+digit LCD's which are not easily found for $17.50 ppd. Write: Will Hubin, 719 Cuyahoga St., Kent, OH 44240.
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