Nov 2010

11 Nov 10 Today 3.9 Total - 124.6 FC is set at 740 FC read 43.6 actual 41.4

Flew to KECP (Panama City) to pick up Kevin. Had a 12 knot tailwind going over and had 190 knot ground speed. Paid the price on the way home though with a 168 knot ground speed. Got a surprise approaching Gainesville when the engine hesitated and surged. It was after dark and the nearest airport was GNV and it was not within gliding distance. Selecting the right tank returned power. For some reason the left tank fed completely dry while the right one was still mostly full. I should have recognized the symptoms, but I had previously had such even feeding from the tanks that it didn't cross my mind that only one tank was feeding. One wing was heavy and the autopilot was struggling to hold heading. I was also having to add aileron trim - something I never have to do. I should have caught the symptoms - but didn't.

The fuel system performed exactly as designed and as expected - the engine lost power and switching to the full tank restored power. The left tank took 20.82 gallons at fillup, so my unusable fuel is exactly as previously determined during a ground run - 0.18 gallons - or 23 ounces of fuel.

The real puzzle is why the left tank fed out while the right one didn't. The tanks have been feeding evenly on previous flights, so I need to figure out what happened.

Today's engine readings

OAT

RPM

OilP

OilT

2489

24.2

12.7

171

EGT

1432

1423

1429

1365

CHT

360

357

403

368

OAT

RPM

OilP

OilT

2490

24.3

12.8

172

EGT

1431

1422

1429

1366

CHT

360

358

404

369

OAT

RPM

OilP

OilT

2405

21.6

11.7

75.1

180

EGT

1354

1343

1357

1292

CHT

348

350

391

359

OAT

RPM

OilP

OilT

2398

23.4

11.9

177

EGT

1394

1381

1399

1333

CHT

345

347

388

354

OAT

RPM

OilP

OilT

2395

11.4

177

EGT

1416

1403

1418

1355

CHT

340

347

386

361

13 Nov 10

Kevin and I changed the main tires today. Several months ago I ordered a pair of the Van's Aero Classic 5x5.00 tires and tubes. I got 127 hours on the original tires and could have gotten a few more hours, but it was a good time to change the tires while I had Kevin to help me. We cleaned and repacked the wheel bearings and inflated the tires to 50 PSI - per the manufacturers recommendation. The nose tire I ordered from Van's was grossly out of round so I sent it back and I'll order a Goodyear Flight Custom III for the nose. I want a stiff tire on the front that is round and can be balanced well. The nose strut is till shimmying on landing and I believe a balanced tire will help. I'm also going to back off on the torque used on the nose axle. I took a video recently and it appears that there may be too much friction as the tire touches which sets up the vibration. I had previously assumed the vibration on landing was due to left-right movement of the nosewheel, but the video reveals it is fore-aft movement.

19 Nov 10

Well let's update things a bit. I've done a lot of work over the past few months but haven't updating the web site with all of the info.

Exhaust Pipes


The original Vetterman exhausts turned down just past the engine mount/nose strut support. The pipes moved enough that the right one was hitting the mount and wore a hole in it.	So, with the help of Bob Bean, we reshaped the pipes and made them straight. I also added stainless steel to protect the fuselage from heat.	That would have been fine except that the exhaust was hitting the bottom of the airplane - creating a mess and making the cockpit noise level much higher.

So, I got some scrap pieces of pipes from Bob, made them fit as good as possible, and he rewelded them for me	The extended pipes are now well clear of the fuselage so exhaust gas does not hit the fuselage	The latest pipes are not well matched, but they are acceptable. They have reduced cockpit noise significantly and seemed to have "tuned" the exhaust a bit.

Upper Gear Leg Fairings

The upper gear leg fairings have always bothered me. On original installation, I didn't use enough fasteners on the outboard leading edge and there was a gap. I use tape to close the gap for awhile until I couldn't stand the sight of the tape any longer. I added some fasteners along the leading edge but still had a gap. I mixed up some resin with micro and filled the gap and sanded it back down. I've still got some work to do on them, but they are a nice change.


Original fairings were not tight enough	Which left a gap around the top	While working on the fairings I discovered the upper strut fairing fiberglass attach point had broken so I repaired with carbon fiber (no after photo)
	The fairings after filling and adding fasteners are much tighter. I'm going to do more work on them to close all the gaps and smooth out the exposed exterior.

I pulled the cowling the other day for a non-related issue and found one of the reed valves on the Bowers intake had been blown outward. I don't know how or when it happened but it must have happened with a kickback or backfire during start.

Today I began making the air dams for the wheel pants. I'm going to make one for the nose pant first and do some tuft testing to see what the airflow looks like. Then I'll do some speed runs to look for any improvement. If worthwhile, I'll move on to the main pants.

	Left: I used 1" particle board and drew an approximate tire opening outline. It turned out I had to squared off on the front too much. Right: Laid 3 layers of standard bid glass.
	Left: Since I wanted the option to add a streamlining fin to the dam, I made a vertical support out of 1/8" veneer that will be the foundation. Right: I cut out the tire opening and filed it to shape.

Here are the support pieces in place	The vertical support is aligned with the trailing edge and the center of the tire	The particle board support is inclined 3.8 degrees because the aircraft sits at that angle on the ground. When airborne, the bottom of the air dam will be parallel to the relative wind

24 Nov 10

Got the glass work done on the nose pant air dam. Had to shape some balsa then added modeling clay to get the basic shape of the dam. I laid four layers of glass over the clay. That is a bit too much glass (and weight) but I'm not concerned about the weight and I want strength to withstand 200+ speeds. Since the dam will only be on during races, I won't have to carry the weight around all the time, so weight is not a big issue. Besides, it's only going to weigh a half pound or so.

	Left: I completely covered the nose pant with tape. There are some wrinkles in the tape due to the curvature of the pant, but I will just have to deal with them later Right: I taped the vertical support to the pant
	Left: I pushed the particle board against the tire and adjusted it to be laterally level with the airplane and at a 3.8 degree angle. Right: In order to get an initial shape, I made a balsa leading edge and added clay around it
	Left: The clay gradually began to take shape as I added clay and worked it. Right: Then with the clay reasonably smooth, I added four layers of bid fiberglass
	Left: Another shot of the freshly laid glass Right: A view of the aft fin

27 Nov 10

The nose air dam turned out reasonably well. I trimmed it some and did some sanding. I'll make the attachment fittings next so I can remove the wheel pant and work on the bench instead of the hangar floor.

	Left: After removing the particle board support and after a bit of initial trimming Right: After removal and trimming the lower dam some. The modeling clay (dirt) and balsa haven't been removed and the top is not trimmed
	Left: Removed most of the dirt and trimmed away the excess. Right: This shot shows how close the air dam is to the tire. It is much tighter than the wheel pant opening. This also shows how little of the tire is exposed to the air flow. As a result of using the particle board for the initial layup, the dam is flat on the bottom. The bottom will be within 0.1 degree of alignment with the relative wind when at top speed.
	Left: My original plan was to leave very little lip on the lower portion of the dam, but I think I will trim and sand it just a bit more and leave the lower lip larger than planned for now. I'll fly it and tuft test using video camera. Then I can decide whether to remove more of the lower lip. Right: The aft fin will be cut down dramatically. I'm leaving it large for now and I'll trim it last. The transition underneath from the tire to the dam will need some work - probably adding some glass to smooth the flow.

Here's a before shot of the nose pant	This shot gives an idea of how the dam will control the air flow around the tire. The bottom of the dam angles upward 3.8 degrees in relation to the floor because the aircraft sits at a positive angle compared to the inflight attitude.	I'll add some slurry later and sand it to make a smoother transition from the front portion to the aft fin.

This addition may make no difference in speed, but it is fun to experiment. Even if I gain no speed, I'll go ahead with making some for the main gear because the combination of all three may cause a speed gain.

I'll attach these only for racing. During everyday operations I'll fly with the naked pants.

The better solution would be to make some narrower, pressure recovery pants, but it would be too much work to make all new pants and then get them to fit. The original ones were difficult enough and they fit perfectly.

Next update in Dec