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Posted by phil alvirez | Sep 18, 2016 @ 12:57 PM | 1,149 Views
i have built 3 identical wings for my 2 meters sailplanes.
they look alike and the only difference is that the last 1 has spars of carbon fiber instead of spruce.
i can use them in several fuselages.
with 2 of them i have found that some times they flutter and worries me because the plane can loose its wings in any moment.
when gave them a closer look the only difference i could find was that the 1 that does fine has a turbulator at the leading edge (a piece of thread that is about 1/16" and runs at the neutral point of the leading edge).
so i added a thread at the leading edge to the 2nd and 3 threads at several positions along the chord to the 3rd and tested them today.
the 2nd with 1 string at the leading rdge still had the flutters.
then tried the 3rd with 4 turbulators. no flutter!
then to the 2nd with 1 i added 3 more turbulators: again, no flutter!
so seems that turbulators not only improve the efficiency and stability but get rid of flutters too.
more tests to come, but it was so clear the change that i think will just confirm this experience. will tell.
edit: just to tell that more tests are confirming it.
(by the way, near the end of page 11 of this blog there is more on turbulators, if you want to see all that i have learned about it).
Posted by phil alvirez | Aug 27, 2016 @ 06:27 AM | 2,571 Views
all began with the Radian, a 2 meters (80") electric powered sailplane from horizon hobby. i learned about it when i watched it flying. it impressed me so much that same day i went to the nearest hobby shop that stocked it and purchased 1 and was flying it next day. no gyros nothing.
but then they released the 29" UMX, that has gyros (electronic stabilizer), that makes it fly in some wind as if were a way larger plane.
and i got 1 too for flying at the backyard or nearest park.
then came the Pro, that has ailerons and lower dihedral, for aerobatics. that i dont have 1 because my goal is thermaling.
and now we have the largest 2.6 meters (102") XL that comes with a receiver with gyros, for windier weather. and i have 1 too.
all excellent design and manufacture. congratulations to the designer (or designers, if more than 1).
this is just the start. i will keep bringing comments on my personal experience with them, so keep posted and get into the end of this. see ya.
i will start with the impressions i got on each 1, then details and then what i have done to improve it or make my life easier.

#1: the 1st:
http://www.e-fliterc.com/Products/De...D=EFL4750#home

#2: the micro:
http://www.e-fliterc.com/Products/De...#quickFeatures
1.-loosing signal: if sometimes a few seconds after launching, motor stops and you cant control the plane and crashes, may be due to the esc disconnecting. this happens to me when i plug a...Continue Reading
Posted by phil alvirez | Aug 21, 2016 @ 08:06 AM | 1,590 Views
modifying anything depends of our point of view of things.
there are those who think that 'if it works, dont mess with it', and do fine. and there are the others, the adventurous, who are always looking for something to 'improve'. and frequently get into trouble.
things are not only not improved, but get messy.
but not only there is room for both; it depends of the personality and goals. both are right, even if at opposite ends.
if it were not for those who want to try a new idea, we still would be living in caves. on the other hand, the conservatives make life safer.
so, after all, we need to understand the others point of view and live in harmony.
live and let live!
Posted by phil alvirez | Aug 12, 2016 @ 05:47 PM | 2,121 Views
i started a thread and shortly after that, on a moment of lucidity, noticed that it made non sense, so immediately erased it, but later went back and noticed that it has become a subject of the funniest non-sense i ever saw.

http://www.rcgroups.com/forums/showthread.php?t=2718449

so, if you want to laugh out loud as i did, peek in and have a good time.
you may even participate. nobody is going to tell you that you are out of topic.

feeling sick, and with the weather horrible, i havent been able to fly for a long time, but this made me forget all.
Posted by phil alvirez | Aug 09, 2016 @ 05:58 AM | 2,704 Views
it is great to have theory as starting point.
but it is worthless if we dont confirm it at the field.
and if we dont provide all the details.
sometimes is better to start with results and then develop the theory to explain it.
but it happens that, even if we have a nice theory that makes sense to us, or if we get some results at the field, some1 will disagree and start a discussion where will not reach an agreement.
and this may happen with fellows that are well known, or that have good education.
why this happens?
as Don Stackhouse said: "the devil is in the details".
problem is, if we dont get together and show our planes and study and analize them and all the details, and do the testing together, at same place and time, it is impossible to have all the details and reach the right conclusions.
i will bring an example where this could be understood:
suppose 2 fellows get an identical plane ready made. as i am into 2 meters sailplane i will suggest the radian, that is an excellent thermal plane and comes with everything, ready to fly. that is, we only need to charge the battery, do the binding, test for range and go. both guys watch each others plane and confirm everything. cg, decalage, whatever. then fly both planes and exchange them so everything looks all right. then 1 of them makes a change like moving the cg. and so on. only 1 change at a time. they are flying the same plane on same weather conditions. then it is possible to reach same conclusions. if this is not done exactly this way, there is the possibility of discrepancies. that is why there are so many discussions that lead nowhere. so it means that 2 or more fellows may be right on what they say: because the devil is in the details.
think about it.
Posted by phil alvirez | Jul 29, 2016 @ 06:06 PM | 2,759 Views
or should be the ecstacy and the agony? let me explain and you will decide:
today was another of those wonderful days when the weather cooperated at its full extent. no wind, puffy clouds, no moskitos, so i could fly my 2 meters sailplanes. so i began to fly my planes. the light 1 (650 gr) got light thermals at low level and thanks to the vario catched them effortlessly and remained there until i decided it was enough and turned the vario off. but then the plane didnt descend. kept sailing back and forth for a long time. ecstacy!
then the standard (860 gr) went up. this time climbed higher. all seemed o k. thermaling great. ecstacy again!
then i got enough again so again, turned the vario off thermaling. but as i changed the vario to height (tells the height) i noticed that it was climbing at an alarming rate. soon was above 400 meters, and couldnt bring it down! spin, dive, whatever, but no. i have to be careful because if i bring it down too fast it may fold the wings, so the only thing i could do at that height was to listen to the voice how fast it was descending. it took a long and agonizing time to be at a safe height. then i just landed it and went home. no more fun for the day.
so, was the agony and the ecstacy or the other way around?

Posted by phil alvirez | Jul 24, 2016 @ 06:25 AM | 2,611 Views
just got this answer from a fellow to whom i asked something:
" I'm a bit of a practical guy when it comes to modeling. If it works then that's good enough for me and if it works well then that's a even better:-) It's a shame people feel like they cant contribute in an open forum. For me I like to hear as many options as possible. That way you can consider all of them and go with what is best for you"
it sounds so good that i just cant resist to show it. i couldnt agree more.
Posted by phil alvirez | Jul 19, 2016 @ 02:25 PM | 2,652 Views
weather vane effect on sailplanes

if a plane has too much side area behind the cg it may have the tendency to point at the wind and resist going any other way.
just like a weather vane. resisting to change direction.
Frank Zaic mentioned a method to keep this in balance by a very simple method without calculations. he called it center of lateral area.
from cardboard he cut a profile of the model showing all the components viewed from the side, including the side of the wing with the dihedral. then pinned it at the desired cg and saw if it balanced. i tried it with all my models and it worked.

if any1 has some experience with this, please bring it.
please only comments polite, positive and to the point.

i started a thread on the issue here:
http://www.rcgroups.com/forums/showthread.php?t=2701818
Posted by phil alvirez | Jun 21, 2016 @ 08:38 AM | 3,257 Views
a child asked his grampa: what is better: to be a dreamer, or to be a realistic?
and the grampa answered: well, could be that you can be both:
giants walk with their heads in the clouds, and their feet on the ground.
so, you can be a giant. it is up to you.
Posted by phil alvirez | Jun 18, 2016 @ 12:59 PM | 3,431 Views
Oscar Wilde said that "the only thing worse that not getting what you want, is getting it".
i never thought much about it because i thought it was 1 of his jokes.
that is, until today.
weather good, flew some of my new 2 meters sailplanes for calm for evaluation, and when the wind began to blow, i pulled 1 for windy weather, that has the vario that sends tones or tells the height.
tried to find a thermal but nothing. climbed 3 times to 200 meters (some 640 ft). the sky had just a few thin strips like veils. not the best conditions for thermals i know. the plane didnt sink, but no beeps.
i sure wanted thermals.
and then the vario began to sing. and up she went. up and up. 200 meters, 240, 300... then i began to worry. the plane looked smaller and smaller even if i did nothing. so i moved away, but no matter where, the vario kept telling higher. tried to trim it down. then dive. then the wings began to flutter. so dont put so much down. eventually began to drop. 300, 270, and so on. took over 10 minutes to land. by then i didnt want to fly anymore. i kept telling to myself: so you wanted thermals, didnt you? the flight was over 30 minutes.
so think carefully what you want: the gods of the air may be watching and decide to please you.
Posted by phil alvirez | Jun 13, 2016 @ 10:54 PM | 3,757 Views
recently purchased 2 pods and booms from here:
http://www.clm-pro.com/fuselage-pods...to-2m-wingspan

this is the story:
i contacted them about certain pods, and asked if they could use 28 mm motors and they said yes.
so i ordered them.
but when trying to install a 28 mm motor it didnt turn due to the inside too small. the motors i use are outrunners with the wires coming from the front.
see examples: https://www.hobbyking.com/hobbyking/...dProduct=25075
http://thebuildrc.com/eurgle-rc-plan...ess-motor.html
i tried to remove plastic but to no avail.
then cut openings at the sides to let the wires: still not enough on 1 of them. so i contacted them but they said that as i did not specify for which motor i needed the pods, they could not replace them.

so if any1 wants to buy anything from them, you need to be specific on what motor are you going to use, and include link to the product so you will not find yourself in my situation.

but still i think that when i asked if these pods were good for 28 mm motors and they said yes, they should add: "but not for motors with the wires coming from the front". then i would not buy them.
the pods are very good quality still.
end of the story
Posted by phil alvirez | Jun 12, 2016 @ 09:03 AM | 3,140 Views
since i remember, i have been fascinated with art and technology. went into tech by need but still liked art. now i can practice both, with my model airplanes, and with painting. when i got into painting i realized that as there was so much to learn in order to achieve what i wanted, i had to concentrate on it, so i quit planes for several years. but now i understand that painting is pasive; more like meditation, and feel like as if i were in the painting am doing, and i spend way more time just watching the paint than painting. this is great for me for relaxing, but does not help to keep my brains active. on the other hand, planes do. designing, building, requires an effort to understand all kind of problems and find the best solution. and flying means action. instant reactions constantly. facing the problem of keeping track of how the plane is flying; searching for a thermal; making sure that the plane does not drift away too far... and landing, with the turbulence increasing near the ground, needs all my concentration and fast reactions. it is fun, but dinamic fun! so i have reached the point where that, even if both are extreme opposites, practicing both gives me a balance that helps me feel young and alive.
Posted by phil alvirez | May 27, 2016 @ 08:41 AM | 3,415 Views
am in the process of evaluating lifting stab on 2 meters sailplanes. my goal is to use them for thermaling. not competition; to be able to stay up longer with less effort.
but above all, if it is easier to detect thermals and if a plane can be trimmed so if it senses a thermal stays there, like the free flight planes do.
also, i am trying to stablish a comparison: how a lifting stab influences the flight? stability? under power? does it help make the airplane more thermal efficient? easier to detect thermals? does it increase drag too much?
all of this will be tested in a future.
if you are interested, keep looking into this post. will be updating it at the end.
r/c models of all kinds use flat or symmetrical stabs that do not generate lift at zero degrees of angle of attack.
in ancient times, guys that flew free flight duration began using flat stabs. until some1 'discovered' lifting stabs, and from then on, all the planes use it. even to this day the indoor free flight power (rubber) use them. all of them.
there was a guy who collected plans from all over the world, together with comments of their designers, and published them. even wrote a detailed study and showed it on his books of 1951/52 (pages 5 to 20), and 1953 (pages 3 to 18). his name is Frank Zaic, and all of this was widely discussed and used by everybody-including all the experts and those who won all the competition for many years.
these books still can be reached by google.
...Continue Reading
Posted by phil alvirez | May 11, 2016 @ 09:41 AM | 3,619 Views
yesterday when i looked from my window at the trees nearby checking the wind, i noticed some movement on the grass. it was covered with yellow flowers, but some seemed to be in motion. so watching more closely i saw 2 canaries: 1 with the head and wings of dark color, the rest bright canary yellow. the other with just a few dark feathers so it was mostly yellow. nice sight. they were picking something (seeds?). then the darker found a puddle where took a bath. funny the way they do that. suddenly both took off. i never saw canaries flying free, only in cages. and with winter so cold here this was the last place i could imagine seeing them. perhaps came from the south as the temperature is now above freezing and are becoming sort of migratory birds too. perhaps escaped from their cages and learned how survive in the wilderness. grown in cages, most birds if get free often die as dont know how to find food and water. so it was a pleasant surprise i would say. it is 1 of the wonders of this spectacular land of the north, always full of surprises. (although some are not very welcome, like tornados and storms).
Posted by phil alvirez | Mar 06, 2016 @ 06:21 AM | 5,273 Views
once there was a boy sitting with his grampa at the porch when a dog happened to pass by. the other dogs at their homes barked at it when he passed by, but he didn't bark back, neither stopped to fight with them. just kept going...
them his grampa told him: that is a wise dog.
and the boy asked why?
he said: if he had stopped to bark back and fight, he wouldn't ever reach as far as he was intended for, or even reach anywhere.
never waste time barking at the other dogs. you will not be able to reach your goals. there will always be dogs barking at you, trying to stop you for an unproductive fight.
Posted by phil alvirez | Mar 01, 2016 @ 02:45 AM | 5,504 Views
recently when i went to my son, he showed me a new game to play with his daughter. it is called apples to apples. they post a card with a subject and give you 5 cards that have different subjects, and you have to make as many as possible to match as close or as different as you can with the 1 on the table. no matter how silly the excuse you have.
i couldn't play it. i found it as stupid as it could be.
i have spent my whole life doing what it takes to make sense to all that i do and think, to be logical, and with matters of science, to use data to reach conclusions. but i also realize that people play apples to apples everywhere. and sometimes even here at the forums, i find some that play that too, and am unable to communicate for that reason.
luckily there are few.
Posted by phil alvirez | Feb 13, 2016 @ 02:59 PM | 5,938 Views
my experience
i have been into sailplanes for many years (i enjoy catching thermals).
at the beginning, they were free flight (there was no radio control at the time). from 18" hand launch, to about 60" (1.5m) towline.
then, when radio control became practical and affordable, i got into that.
planes from 1.5 m to 2.5mt. then electric motor to assist climb.
the 1.5 seemed easier to handle and store, so worked with them for some time.
then went into 2 mt. 1st with 2 pieces wing. then 1 piece.
eventually i settled to 2 mt. and 1 piece wing-no ailerons, flaps, spoilers-nothing. just clean simple 3 channels. learned that don't need ailerons for thermaling.
learned that larger required 2 pieces wing, and made things more complicated than i needed-and couldn't see any improvement in flight, and also thermaling required larger size thermals.
am beginning to understand why the 2 mt is the most popular.
but that of course depends on each 1.
Posted by phil alvirez | Jan 27, 2016 @ 03:10 AM | 6,543 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 @ 04:45 PM | 12,187 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 @ 04:23 PM | 7,417 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.