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phil alvirez's blog
Archive for October, 2012
Posted by phil alvirez | Oct 31, 2012 @ 09:46 AM | 5,726 Views
have you wondered what shape a thermal has? a bubble? a cylinder?

i found an article in a model airplane's magazine (american modeler-august 1961-page 42), where the author (Bill Winter) provides a link on the thermals shape and behaviour, from an article from Soaring magazine, by Clarence Cone, issues april/may/june 1961.
this is the link: http://soaringweb.org/Soaring_Index/...61_Apr_08.html page 8

the link was lost, but managed to retrieve it.
Posted by phil alvirez | Oct 08, 2012 @ 09:21 AM | 6,050 Views
october 8, dawn, near freezing, some frost; no wind on the ground, some up there. plane: stock radian 2 mt sailplane; 1400x3 pack; dx6i tx. i didn't notice any change in trim with the extra 16 grams of the quanum tx. ran motor for 5 min total for 6 flights (some 50 sec each). programmed for 11.5v alarm, which is about 3.8 per cell. watching the screen now and then, i could predict when it was going to hit. i didn't hear the 1st 2 beeps, as my hearing is not so good, but when i heard the 4 beeps repeating, landed at once. it was showing 11.48v, which is about 30%. at home the charger showed 50% at 11.54 when started charging, and took .575 ah to charge to 92%. i guess the pack recovers after a rest-the time it took to get home. my experience is that it is not difficult to glance at it occasionally, and the readings are helpful, once you know what figures to target. in my case i was aimimg at 3.8 per cell, so i was ready when the figures were getting close to that.

to me, it is a practical approach, so the quanum works fine with these basic readings, even without the amps device installed. as i said, once you know what figures to program to stop flying. i hope to test the amps meter when i get it, and the weather brings a chinook (indian summer), otherwise i will have to wait until spring. am getting too old to handle cold. today i had to wear my mask (balaclava they call it) that covers my nose to prevent me to catch a cold again (am just recovering from the worst flu...Continue Reading
Posted by phil alvirez | Oct 04, 2012 @ 09:40 AM | 5,384 Views
turbulators:
1.-stability increases;
2.-speed increases;
3.-drag is reduced;
4.-glide is more flat;
5.-duration increases;
6.-the most effective location is at leading edge;
7.-if using only 1, place it at the leading edge;
8.-when using more (besides the 1 at leading edge), placed at certain % similar to birds, all of the above increases even more than when using only 1;
9.-thickness has to be small (like thread).

steps:
1.-stability increases a lot (more than with turbulators);
2.-drag increases a lot;
3.-speed is reduced;
4.-glide is not as flat;
5.-duration is reduced;
6.-location (% of chord), thickness, and adding more steps does not change performance noticeably;
8.-thickness has to be large. i mean, about 1/4" and up.

conclusions:
1.-turbulators: increase stability and efficiency; drag is reduced; speed increases; reynolds increases;
2.-steps: increase stability enormously and efficiency is reduced. drag is very large; reynolds is reduced.

june 17, 2013: i have been using turbulators for a long time. most of them with spars at the surface, as part of the structure, an also threads glued along several positions of the wing, running parallel to the span, over the covering. in recent times i built 2 identical wings, 1 with turbulators, and another without them (on the surface) and compared the plane's performance, even measuring its speed. now am working with sailplanes around the 2 meters (80") wingspan.
what i do with all...Continue Reading