Dec 2010

3 Dec 2010

More work today on cleaning up nose pant air dam. Sanded slurry I'd applied to fill pinholes and low spots. Then added some glass on the bottom aft of the dam and added some more slurry to shape the aft portion.

Began work on smoothing the air flow at the main pants/gear strut intersection. Months ago I discovered that there is lots of turbulence near the intersection so I'd made cleaning up the air flow one of my "to do" items.

	Left: After flight, oil drops indicated air flow separation aft of the wheel pant split with the air flowing inward. At best, the air was turbulent in this area. Right: Aero guys recommend obtuse angles to minimize interference drag. The wheel pant/strut intersection is obviously acute. So, my idea is to use the current screws to attach a fairing that will increase the angles and reduce interference
	I taped up the pants and squirted on 'Great Stuff' insulating foam. It expands except for the part that is not exposed to air. I should have punctured some holes in the tape to allow air contact. The foam protected by tape stayed uncured until exposed to air.
	Then I used a serrated edge knife to initially trim the foam.
	Then I used sandpaper to clean up the shape. Next I'll add Bondo to fill the crevasses and form the shape before putting on two (maybe three) layers of glass. The new fairing will attach with current fasteners except for the trailing edge which will be pulled tight with new fasteners.

9 Dec 10

After reviewing my nose shimmy video, I'm having second thoughts about installing the nose pant air dam just yet. The air dam is much closer to the runway and it appears it may contact the runway when the nose strut begins it's shimmy. If the dam were to hit the runway it would likely be shoved backward into the pant and destroy the pant. So, I need to attack the shimmy issue. I think loosening the torque on the nose tire may help, so that is next on the agenda.

View Nose Wheel Shimmy Video

I thought the nose wheel was shimmying left and right, but the video shows it is fore-aft. I clamped the digital video cam to the tiedown ring. With fore-aft movement, the nose of the air dam is likely to jam on the runway.

COOL. Nelson has returned to FL for the winter. So, now we'll get to do some flying together.

19 Dec 10

Even though he's not here to work, Nelson and I have worked on the RV and we have several issues resolved. Most important is the nose wheel shimmy. Bought a Grove magnesium nose wheel and axle and the nose wheel shimmy is gone. The problem was the tightness of the Van's Matco wheel design. The Matco wheel had rubber seals that added a lot of drag. That combined with the tightness of the torqued axle bolt caused the nose tire to rotate with lots of friction - only 1/4 turn when attempted to spin with weight off. That was causing a harmonic vibration to begin as the nose wheel touched down - due to the springiness of the nose strut. With a freer rotating wheel, the harmonic was never started. If I was able to figure out the problem, then I'm sure Van's has known about this problem and the solution for many years. Puzzles me why he doesn't pass along solutions to problems.

The new Grove wheel has an internal axle spacer that is intended to allow preloading the bearings. That results in a more free wheeling tire (1 revolution instead of 1/4) and the harmonic in the nose strut is not begun at nose wheel touchdown. The Grove wheel is made of magnesium and is one pound lighter than Matco. It is more expensive than the Matco, but worth every penny.

We also got the strobe light problem figured out and removed the power supply for overhaul. I asked Whelen about the power supply having sat on the shelf for several years before being used and they said "No problem. Just mount it, plug it in and it will be fine." Well - not true. So, now I have to get it overhauled.

Also laid the glass for the main wheel pant fairings. Nelson wetted glass while I laid it. The cured fairings look very nice and I'll get them sanded and shaped in time for the January Spruce Creek 100 race. Now that the nose wheel shimmy problem is solved I can move on with the nose pant air dam and I will use it during the race also - if I proves to increase speed.


After shaping the foam I covered with Bondo and sanded	It took three coats of Bondo plus glazing	These photos show before sanding the third coat

We laid three layers of bid glass overlapped at the leading edge for strength	The trailing edge was droopy but didn't matter since it is to be cut away	Peel ply soaked up excess resin and make a nicer finish

I made paper templates of top and bottom of pant and used them to make outlines on glass	Trailing edge trimmed and removed from aircraft	The fairings look rough, but will trim up and sand out nice

After initial trimming and attachment using existing screws	The lower portion mirrors the bottom of the pant and exists mainly to provide someplace to attach the upper portion	I'm using three screws to attach the fairings and I'll add 2 or 3 fasteners in the trailing edge to hold the upper and lower together

I made a streamlined weight for the tail. Aero guys tell me that any downforce on the tail (such as weight) will reduce the induced drag on the tail since it must produce a downward force. I bolted lead weights on a tiedown ring and added foam to shape the streamline. I'm adding fiberglass over the entire thing and then will split it to make it removable and attach it with screws. Will flight check it after the first of the year.

Upcoming Flight Testing

- Test tail weight

- Test main pant fairings

- Test nose pant air dam

- Test exit air fairings

- Test sump fairings

- Test winglets

- Test gap seals

For Racing

- Polish leading edges

- Make hinge fairings

- Add gap seals

- Remove all extra weight

- Tape NACA air scoops

31 Dec 10 Today - 0.8 Total - 128.2

I finally got to take Nelson flying in the RV. We only flew a half hour or so due to fuel venting from the right tank. But, we'll have lots of opportunity for more flights.

Nelson's experience was a big help today. He reasoned through two problems I've been having and came up with solutions to both. The engine has always idled too low and had a tendency to die so it took constant attention and jockeying of the throttle to keep an even engine and moderate taxi speed. He changed the idle setting on the injector body by "one flat" and the problem was solved. The engine idles between 700 and 800 RPM with only light surging. I'm anxious to fly it and see how the idle is after landing. That is when the most problem occurs.

Two months ago, and occasionally since then, the left tank feeds faster than the right with the both selection on the fuel selector. I've had occasional fuel venting from the right tank. His logic was that when the fuel lid vented (leaked due to looseness - it needed adjustment), then the pressure in the right tank was lower thus drawing fuel from the left tank. I'm sure his theory is correct as the imbalance problem began occurring in conjunction with the fuel venting. I tried to tighten the locking nut on the fuel lid but apparently broke the tiny 1/16" rolled pin that holds it all together. He took it apart, devised a stronger pin, and put it together again. It now fits with a solid sounding thump as it locks in place. Should you encounter the same problem, be aware that the way to tighten the fuel lid is not to tighten the locking nut on the inside of the fuel lid - it is to LOOSEN it, then turn the circular aluminum fitting clockwise, then retighten the lock nut. The circular aluminum fitting is threaded onto the bolt through the middle of the cap and turning it adjusts the "tightness" of the fitting.

Made good progress on the engine mount fairings, nose pant air dam, main pant cuffs, and tail weight - all involving fiberglass and resin. I'll post photos of all when they are finished. The tail weight weighs 1.9 pounds, so I need to do a W&B check on it before flying. I'm also making some fuel tank sump fairings that may provide good access and fair the sump nicely.

Today's Engine Readings

OAT

RPM

OilP

OilT

2506

23.3

11.8

177

EGT

1440

1432

1434

1363

CHT

327

341

369

341

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