phil alvirez's blog View Details
Archive for January, 2016
Posted by phil alvirez | Jan 27, 2016 @ 04:10 AM | 8,800 Views
i want to talk about another source for lift, that i have learned recently. it is a narrow band across the wind.
more specifically:
corridor: a stationary invisible narrow band across the wind, that generates lift.
this happens to me at a flat field with no elevations in sight (the only obstacle is a row of trees), located at 5km from a large lake. there is no wind blowing at the band mentioned; it is clear air all around; the invisible band does not drift (stationary for a long time). i know is there because the vario sends beeps that let me pinpoint its location; the wind does not penetrate it, and the band generates lift; i know this because i can keep my plane at that level forever. i have to keep the plane doing s turns within it to stay on the lift. if i turn the plane across it (facing the wind that is found below and above) the plane flies away of the band and sinks. the area is a narrow band across the wind (but wide enough to let my 2 meters sailplanes do full turns) that blows down here, and is present only at certain level (some 200 meters). ahead, behind, and below it, there is wind and the plane sinks no matter which way i turn, but drifts with the wind. and above, there is wind and sometimes i catch a thermal and drift with the wind.
i have been using 'wave' as it runs across the wind, to diferentiate it from 'streets', that run along the wind, but maybe this makes things confusing, as waves are generated near elevations.
at the end of the day, maybe '...Continue Reading
Posted by phil alvirez | Jan 20, 2016 @ 05:45 PM | 14,152 Views
when i studied aeronautical engineering in the 60's, i took meteorology. 1 of the things we had to learn was how to make a report of the direction of wind at several levels, with the purpose to tell pilots what direction of wind at different heights they could encounter. it is critical, as when climbing you may meet wind from the north and suddenly it changes to the south. it may be particularly critical for light planes. wind may flow at different direction depending of the level, and runs in layers, like blankets. if you have light models you may experience these sudden changes in direction. anyway, in those days we had to go to a small isolated room at the airport and inflate a large red balloon with hydrogen, as helium was not available. we connected it to the tank with a valve and let it blow to the point when the amount of gas made the balloon become buoyant while supporting the weight of the valve. this gave it the buoyancy to climb at certain rate. then we prepared a transit theodolite, pressed a switch that started a timer and released the balloon and aimed at it and pressed a button every minute. this punched a hole in a paper disc and as the timer activated a spring, each hole was punctured further from the center. it ended up as sort of a spiral, if the wind changed a lot. this way the experts could decypher it and make the chart of superior winds. the thing was that we had to do this in an isolated room because hydrogen is explosive, and we had to be extremely careful doing this as it could explode in any moment. some times the balloon just blew, and was a shocking experience because at that moment you felt that you were going to die in flames. to make things worse, there were moskitos around, and the silly beasts took the red balloon as something that they would like to pierce and then it blew.
a horrifying experience i would say. thankfully now with satellites and computers all over this routine belongs to the past.but it was something that you will never forget.
Posted by phil alvirez | Jan 18, 2016 @ 05:23 PM | 8,861 Views
once my plane disappeared in sudden dense fog and lost it. i never expected something like that. i never saw anything like that, or heard about it. there is a post somewhere down in this blog (page 4, Aug 03, 2013 ) where i mentioned it in detail.
it was not until now i found an article that mentions the situation. it says:
Coastal fog and low cloud can come in very suddenly. Cliff soaring can be full of hazards! I was amazed recently when on the east coast to watch a bank of sea fog reduce the visibility from 10 kilometres to around 100 metres in less than a minute (although this was not in fact a sea breeze effect)

this is taken from here: http://www.weatherjackwx.co.uk/tutor...20breezes.html

as i was flying inland, also found this in the same article:

A strong sea breeze front could move up to 50 kilometres inland
so now i understand what happened to me, although it is a rare event.
Posted by phil alvirez | Jan 14, 2016 @ 09:54 AM | 7,482 Views
1 of the most valuable things i have learned, now that am dealing with electronics and having to program everything, from the answering machine to the range, and of course our radios, is that, if when programming something it does not work, is trying again.
don't know why, but it works many times.
don't get scared, just try again.
maybe won't everytime, but it's worth trying it.
Posted by phil alvirez | Jan 11, 2016 @ 01:41 PM | 6,870 Views
conclusions (revised)
based on the opinions from very knowledgeable people, am compiling the data about charging lipo cells in parallel.
this is what i have learned from all the comments from experts:
regarding the installation:
use cells spot-welded (or with tabs and then soldered)
if soldered in parallel you can't check the condition of each cell;
if is series you can, but you have to add 1 extra wire coming from each cell (this is the common way we find in lipos).
with this extra wire each cell is also charged and balanced.
with cells installed in a battery box and connected with springs, there is the risk of having false contacts, but you can charge them individually and keep the pack balanced.
you use parallel connections when you need to keep single cell voltage for the pack, and series if you need to increase voltage to the sum of all.
when using nicads or nimh you can live without checking their condition, as they are tolerant to disbalance.
in the case of cells in parallel, as you can't check volts of each cell, i heard from dickw that you can get an idea of the pack condition by measuring the charge they take and keeping records, so you can see if the pack is going down and needs to be dismantled and you can check each cell and replace the one(s) gone bad.
for this you need to have a charger that measures the charge.
but could be that i did not get it right in something, so i would like to hear your comments about this
the reason for this quest was that i learned that the radio am using has the option to use lipos in the transmitter, and this works for some guys. see their comments; https://www.rcgroups.com/forums/show...3#post33698877