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3 Feb 10        Today - 1.6        Total - 55.0                Fuel Burn 15.38  L 8.27  R 7.11   Fuel Comp 15.9

Decided to move closer to full up IFR ops so took it out today to do AP work and ILS approaches.  Neither worked well, but my fault.  I need to learn more about how the AP works.  The plan was to track victor airways to KSGJ and fly ILSs there and then back to 7FL6 VFR.  The AP tracked well to SGJ and held altitude reasonably well.  But, making the transition from GPS guidance to ILS guidance is clumsy on the EFIS One.  Will try again tomorrow.  Low altitude was very rough today and made the flying less fun.  It's also cold - for FL.

Fuel Readings are still off a bit - made a tiny adjustment.  I'll sneak up on the correction.

Engine Readings

6 Feb 10        Today - 1.1        Total - 57.5

Flew in the Gaggle to KTIX today for breakfast.  Rally was planned today but it was too windy.  Took an Embry Riddle student in the RCP and flew formation on the RTB.

Planned an afternoon flight to do TAS and wind checks as well as VOR and ILS ops checks, but when I tried to start the engine - nothing happened.  Oh, the fun of experimental airplanes.  Well, back in the hangar and pull the cowlings.  I found the nut on the starter heavy wire stud missing.  I have no idea when it came off, although it had to be on today's return flight or while taxiing in after landing.  I couldn't find a new nut to fit because it appears to be metric.  Why the hell do American manufacturers insist on using metric.  We don't want it!!  So, I had to jury rig a fix for now using the single nut I had that would fit.  While the cowlings were off, I checked other things and found some more problems.  I decided to remove the fairings I added to smooth the cooling exit air because they were loose and rubbing the exhaust pipes.  I'll improve them and reattach later.  As I did that I noticed the left exhaust hanger was missing.  Sometime the attach bracket broke and fell off.  So, I have to make a new bracket and hanger.

The small oil leak is still there, but I haven't discovered the source.

I'm also looking at airflow at the wingtips.  I'm still trying to discover the source of the aerodynamically heavy wing.  So, I tufted the wingtips and flew and took some photos.  It appears there is a lot of separation along the aft third of the wingtips.  So, I'm thinking about adding small winglets to maybe smooth the airflow at the tip.  I'll make one for one wing and tape it on and see the results.  Who knows - I might find an improvement.  I'm going to ask an Embry Aero student to help me with the analysis.

15 Feb 10

During recent flights, I decided to do some tuft testing on the wingtips as part of my goal to gain 8 knots by this time next year.  Even though I'm quite ignorant about aerodynamics, I know just barely enough to make guesses about things.  The tuft test indicated to me that the airflow at the wingtip trailing edge is turbulent.

So, I decided to try out some winglets to see if I could improve the airflow and maybe reduce induced drag.  From what I've read, everything in aerodynamics is a tradeoff.  You can improve airflow and reduce induced drag, but add weight and parasite drag in the process.  Any weight addition will be minimal, so my attention was on adding winglets without increasing parasite drag.  That meant I had to keep the winglet frontal area very small.  My thought was to keep the winglet thickness very small and the amount of winglet exposed above the wingtip high point to zero.  So, measuring the deck angle sitting on the ground indicated the airplane sits at 3.4 degrees nose high in comparison to level flight.  So, the top of the winglet needed to match that measurement in relation to the wingtip.

I shaped a piece of .032 to tape for the wingtip that could be taped on and I could analyze the flow pattern.  At the trailing edge, the winglet was 4.75 inches high and gradually got smaller toward the front to 60% of chord.  Studies indicated that the optimum winglet position is at no more than 60% of chord.  As I now inspect the new "winglet" it appears to me that the winglet can be brought farther forward than 60% chord without adverse effects.

Flight tests indicate that airflow at the wingtip trailing edge is improved when compared to the unchanged wingtip.  The tufts are lying straight on the "winglet" wingtip while the turbulence still exists on the unchanged tip.

So, now I need to decide if the change is worthwhile and how to make such a change.  I think it will be best to make the winglet itself out of carbon fiber for strength with very small width.  But, carbon fiber will interfere with the signal received by the internal mounted wingtip Archer VOR/ILS antenna.  However the winglet will be behind the antenna, so interference should be minimal.

I'll do some more flights and then try some yawing to test the ideas.  I'll try some top speed testing also.  Although, I guess they would look cool even if they don't reduce induced drag.

17 Feb 10

My goal with adding winglets is to gain the most reduction in induced drag for the smallest increase in profile drag.  Therefore, the winglet form must not project above the highest point on the wingtip in level flight.  That will keep the frontal area of the winglet near zero.  There will be some increase in skin drag due to the greater wetted area.  Since skin friction increases with the square of the velocity and induced drag decreases by the inverse of the square of velocity, finding the right balance is the challenge.  The goal is to minimize the overall drag, so the profile and skin drag must be very low to make the winglet addition worthwhile.

My "winglet" will be more of a fence than a true winglet, as a winglet normally has a camber whereas mine will be mostly flat with no camber.

18 Feb 10        Today - 1.9        Total - 61.7

Today's flight was to gather more GPS tracks and GS for TAS and wind calculations on the computer.  I also did two ILS approaches and did some tuft testing on the aft canopy and more on the wingtips.

It is obvious from the TAS and wind calculations that the Blue Mountain has some errors in it's calculations.  The BMA TAS is good - with +_ 2 knots.  The wind direction and velocity is accurate only when the actual wind is 90 degrees to aircraft track.  When on the nose or tail it is erroneous.  On the nose, it is 22 degress and 21 knots in error.  On the tail, it is 27 degrees and 16-18 knots in error.  I'm going to fly with another aircraft to check winds and TAS.  FYI, some of the TAS calculators available on the web are poorly designed and produce erroneous results.  I've found only one that is reasonably accurate.

I did some stalls with the "winglet" and took short videos to record the tufts.  The airplane normally does not drop off on one wing during stalls, but with the winglet on, it drops the left wing.  So, that makes sense since the winglet is delaying the right wing stall slightly.  They're going to be a lot of work, but I think I'll go ahead with the winglets - just for fun.

The ILS glide slope was erratic, but I think it was the fault of the ground equipment and/or interference from a King Air waiting for takeoff.  I need to try an approach at another airport.

I decided to tuft test the aft canopy to see if there was any turbulent or reverse flow as some guys have claimed.  There is none.  The flow was smooth and exactly as one might expect it to be.  Maybe not as aerodynamic as a turtle back, but certainly not turbulent.

23 Feb 10        Today - 0.8        Total - 62.5            Fuel burn 33.35   Left - 15.5   Right - 17.85  FC read 36.1  Adjusted to 705

Another flight to check TAS using GPS track and GS as well as watching the tufts so as to decide on a definite change to add the winglets.  Additionally I wanted to check and adjust the fuel flow computer again.  I also made a vortelator from metal tape to try on a gear strut.  A manufacturer of vortelators claims a speed increase when they are used.  I'm reserving judgment until I can independently find the answer.  So, I decided to cut a 5 inch strip of vortelator tape and apply it to the right gear strut and put oil on it and see what the air flow pattern shows.

The BMA EFIS wind readout is erroneous.  It appears to be reasonably correct in azimuth when the actual wind is on or near 90 degrees to track whereas it appears to be reasonably correct in speed when the actual wind is on or near the nose or tail.  However, when wind is on the beam, velocity is in error by about 20-25 knots and when wind is aligned with the longitudinal axis, the directions is in error by about 40-45 degrees.  One can interpolate from the EFIS wind readout to estimate the actual wind, but that should not be required.

Ground Track = 344        GS = 156        EFIS wind = 348/23    EFIS TAS = 180

Ground Track = 120        GS = 201        EFIS wind = 248/37    EFIS TAS = 179

Ground Track = 221        GS = 171        EFIS wind = 308/47    EFIS TAS = 178

Calculations   Actual TAS = 176            Wind Dir = 304            Wind Velocity = 25

The winglet mod still indicates that the addition of a winglet will reduce turbulence at the wingtip trailing edge.  Someone suggested that I make a winglet separate from the wingtip and attach it with nutplated screws.  That way I can easily remove it if I decide I don't like it.  So, I think I will approach it from that direction for now and see if I can make something worth using.

The test of the vortelator tape was unrevealing.  I'm going to try another test.  Apparently I flew too fast or too long because most of the oil was gone as was most of the vortelator tape.  I guess it wasn't intended to go 203 KIAS.

Next update 19 Feb 10