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Posted by phil alvirez | Jan 12, 2013 @ 02:12 PM | 5,618 Views
Phil's Thermal Rex, or Phil's Rex for short, is a hybrid from a fuselage of the scale ASW 28 sold by hobby king. see
http://www.hobbyking.com/hobbyking/s...ider_PNF_.html
and the full size: http://www.easternsailplane.com/east...hleicher/ASW28
the reason why i choose this fuselage is because the looks are like science-fiction but it is very much like the full size. although i did not use the wing shape (especially the wing tips).
(i will be adding data at the bottom of this thread)
the new balsa wing it is a 2mt wingspan, 460 sqin, 543 gr auw w/2x1300 lipos; naca 6409 airfoil.
i used the foam fuselage and tail, and avionics, and designed a woody wing with larger area and an undercamberer airfoil for slower flights.
i got the whole plane and decided to try it as is, before discarding the wing. and boy, was i for a surprise! it falls into a stall and a spin unexpectedly, and i crashed it several times, breaking the nose and reinforcing it, until i throwed away the wing and started my own. fortunately with it the plane is now stable and predictable. originally it comes without dihedral, contrary to the full size, that has some. as the stock was too unstable and prone to snap roll, i added dihedral as per the full size and this helped a little bit; then increased the chord, adding area to the trailing edge, which helped more-but still was a handful. then it was when went into the balsa wing. it has a planked leading edge, polyhedral, and is covered with...Continue Reading
Posted by phil alvirez | Dec 16, 2012 @ 06:57 AM | 5,417 Views
t tail
conclusions
aerodynamically keeps the horizontal tail clear of the wing wake, and this means no turbulence (and only 2 corners), so it is the cleanest of all, and there is a better reaction and sensibility. based on my experience, as i have 3 planes with it, i can confirm this. full size planes, especially sailplanes, use it extensively, and passenger planes like de havilland dash 7 and 8 too, so must be a strong reason for that. another thing is that it can be placed with the leading edge slightly ahead of the fin's leading edge, getting a cleaner entry-and improving even more its efficiency. an example is the ask 21. see http://www.alexander-schleicher.de/p...k21_main_e.htm
installing it, the cleanest way is placing the servo at the fin. or you can use a cable, but this means some drag to the servo. to eliminate drag you can install a linkage with 2 belcranks, but it is more complicated.
also, it is heavier than conventional, as the fin has to be built stronger. but that could be very little if you do a good job engineering it.
and is more prone to damage if you fly competition and do those landings (crashes) to get to the spot-or if your landings are not smooth.
i have a 2 mt sailplane radian that has conventional tail (really it is a low 'x' tail) and it also behaves great, so at the end of the day it depends of what you like best.
i like better t tail for the aerodynamics reasons, and now i do smooth landings, but i must admit that you can live with any way that provides you good results, as long as you do a good installation with as little drag as possible and land smooth.
Posted by phil alvirez | Dec 01, 2012 @ 06:39 AM | 5,416 Views
from the beginning of time, man has dreamed of flying. the wildest of all dreams. and for those who are into this, flying is an adventure. the final frontier. just being able to fly an airplane is all that it is. and for models there are several ways to do it: starting from the easiest, to get an rtf (ready to fly) plane, to an arf (almost ready to fly), to build it from a kit, to build it from plans, or to design your own, the goal is the same: to be able to fly. to experience that thrill of controlling it if it is radio or control-line, or to watch it flying, if it is free flight. of course, having total control in 3 axis that radio control gives us is the ultimate experience of fully controlling it (that is, if-or-when you are able to do so). but even if you are not having total control of it due to being learning, is still a wonderful feeling. i know, sometimes things may go wrong, but that is another thing that adds to the fun. if you could count that everything is going to go right for sure, it wouldn't be the same. the unexpected is the key factor that adds to the feeling of adventure.

but, oh what a glorious feeling, don't you think?
Posted by phil alvirez | Nov 20, 2012 @ 03:04 PM | 5,798 Views
Thermalis is an idea of an electric sailplane for soaring in calm to moderate wind. it has 80" wingspan and 10" chord almost to the tip, and 764 sq in; weighs 926 grams (32.5 oz) with a 3x1400 mah pack. i just started evaluating it and will provide comments whenever i get enough flights, but so far am flying in cold weather with no thermals. am also playing with cg and trim.
nov 21-the concept: a simple sailplane for rudder and elevator-no ailerons, for relaxed flying and getting into thermals (hence the name), in moderate wind conditions. the wing is 1 piece polyhedral and the fuselage is box type, 1/8" solid balsa, like the horizontal tail and rudder. still, as i wanted to try spoilers and flaps for the 1st time, i decided to add them. the flaps are of the split type (similar to the 1s used on the full size douglas dc-3). another feature that i added was the t tail, that is not as simple as conventional tail, i must admit (i will comment on this later).
>>>will be adding details. check at the bottom.
testing the Thermalis‏
21/11/2012
i started with the cg a little bit forward from the point for which i designed it. the launching went fine, with a strong climb at half throttle. the motor is very powerful and with the 10/6 folder it has lots of power. the climb is at about 70-80 degrees without tendency to tip stall, that was haunting me with the other sailplanes before. the glide is the best i have got compared with the other...Continue Reading
Posted by phil alvirez | Nov 14, 2012 @ 11:19 PM | 5,623 Views
at the beginning i posted a link to an article where it stated that thermals are like horizontal donuts that climb, with the wind going up at the center and down at the edges.
we all believed that article (it was back in the 60's), but recently i found another approach. http://www.xcmag.com/2007/07/thermal...rt-1-thermals/ where he brings an explanation that comes very close to how cumulus nimbus grow, including the same shape, so am beginning to lean towards this idea.
so this way thermals don't turn left or right, just wind goes up inside and down outside-and this matches with the other theory in that sense, so you turn any way you find is better to stay put.
and the idea of trimming the planes to glide to the left from those days could be to balance the torque of the motor, be rubber bands or engine-and somehow it became customary and we did gliders that way too. just a guess.
Posted by phil alvirez | Nov 02, 2012 @ 05:02 AM | 5,649 Views
on shape of thermals



i found this, providing data regarding the shape of thermals:

http://www.xcmag.com/2007/07/thermal...rt-1-thermals/

which looks very much the way cumulus nimbus behave.

by the way, i just started a thread in the forum "thermal":
http://www.rcgroups.com/thermal-36/
and still another view:
http://www.soartech-aero.com/Thermals.htm
and 1 more: http://www.rcgroups.com/forums/showt...64#post4966743
Posted by phil alvirez | Oct 31, 2012 @ 09:46 AM | 5,926 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 | 6,241 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 | 5,594 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
Posted by phil alvirez | Sep 20, 2012 @ 12:07 AM | 5,696 Views
i consider this subject of extreme importance, hence i bring it here for all to know.
i asked master David T ( http://www.deltang.co.uk/) his opinion. this is what he said:
" Hi. I've done some flight tests with aerial orientations and I've been asked to comment on the 90' thing. Signal strengths are greatest out of and into the sides of aerials. So the Tx aerial should be 'side on' to the model. Personally I find horizonal easiest.
The Rx aerials receive strongest signals when they are 'side on' to the incoming signal. So orientate and place them where that is most likely. If you have two or more you can maximise coverage by using different positions in the model and different angles relative to each other. The model keeps changing orientation in flight so I guess this is where the 90' idea comes from.
Signal strength reduces over distance so if you fly gliders very high you probably want the Rx aerials horizontal to the ground at the bottom of the model to get most exposure to signals.
I believe signals reflecting off the ground cause problems for radios at low alititude. Coming in to land at low altitude towards you from a long way off is probably quite challenging for radios. If your Tx aerial is horizontal then at least one Rx aerial probably should be too. Having that aerial behind a big lipo or engine won't help!
So as already mentioned, there is no perfect layout. The objective is simple though. You want Tx and Rx aerials parallel as much as possible and this is more important in the difficult scenarios I've mentioned.
Regards, David".
(just in case: when he says 90' he means 90 degrees)
Posted by phil alvirez | Sep 18, 2012 @ 04:39 AM | 5,471 Views
i asked master Lucien Miller from innov8tive what are these. he said:
They are all BEC circuits. The BEC and UBEC are both generic terms referring to a Battery Eliminator circuit. This is any device that will set the battery voltage down to 5 or 6 volts to run the Receiver and Servos. Typically, a BEC is a linear type circuit used on speed controllers designed to be used on 2, 3 or 4 Li-Po cells. The term SBEC means Switching BEC. This type uses a switching type voltage regulator instead of a linear type regulator. The switching regulator is much more efficient, and can be used with higher cell counts, some as much as 12 Li-po cells. Standard BEC circuits take the excess voltage and convert it into heat. Switching type BEC circuits chop the incoming voltage up into little pieces and only take as much energy as they need to create the output voltage required. By doing it this way, there is no wasted energy, and the circuits can be up to 95% efficient in converting voltage from one level to another.
good to know, isn't it?
i am also learning that sbecs are available-and needed-from 40 amps up.
Posted by phil alvirez | Sep 09, 2012 @ 01:19 AM | 5,723 Views
there is another (and cheaper) way to get telemetry (maybe this is the cheapest), by using this system:
http://www.hobbyking.com/hobbyking/s...dproduct=10343
it includes the sender that goes into the plane, and the receiver, that is bolted to the radio.
in this case, the sender (transmitter) that is installed in the plane weighs 16 grams, that has to be added to the plane's receiver weight, in comparison with the other system that i mention in my blog (in which the receiver has telemetry included so it also sends data to the radio, and you don't need the additional transmitter in the plane).
but for planes that are medium to large size this is not much of a handicap, and there are some savings with this.
(the price for all is $49.99 to this day, +sh) or you can use a flexible antenna (lighter, easier to install) that is 4.95 + sh
and for more planes, an aditional transmitter ($29.99 + $6.95 sh) http://www.hobbyking.com/hobbyking/s...mp_Amp_V2.html http://www.hobbyking.com/hobbyking/s...dProduct=10896 is 4.95 + sh
am learning that is very convenient to add a temp/amp sensor ($19.79) http://www.hobbyking.com/hobbyking/s...dProduct=11251
so altogether we need: basic system: 49.99; flex ant: 4.95; plus amp sensor: 19.79=$74.73
there is a thread that analizes all with great detail: http://www.rcgroups.com/forums/showthread.php?t=1267361
Posted by phil alvirez | Sep 05, 2012 @ 03:11 PM | 5,579 Views
this is my view of sailplanes:
recently i have been flying 2 meters (some 80 inches) electric powered sailplanes and have reached the conclusion that they are in need for telemetry, as there are no signs of when the pack is going to be exhausted and the plane will crash-or get lost.
with electric powered planes, when the motor slows down, that means 'land as soon as possible', but with a sailplane there are no warnings.
still, i was reluctant to invest some $450-or more-until i learned from a friend another way:
getting a 9x tx from hk, and the other components from aloft hobbies, the total initial investment is $153.78, and after that, all that i need per plane is $34.01.
details are as follows:
9x tr: 53.95 http://www.hobbyking.com/hobbyking/s...idProduct=8992
sh 23.59
http://www.google.ca/search?q=aloft+...OMnd0QGZ9YDwBA
FrSky DJT - JR Transmitter Telemetry Module DJT $22.76
FrSky FLD-02 - LCD Display FLD-02 $20.47
FrSky D8R-II Plus - 8 Channel Receiver w/ telemetry D8R-II plus $25.71
Battery Voltage Sensor FBVS-01 $2.55
s h 5.75

total (tx and parts):153.78

after this investment, all that i will need for each plane that follows will be:
8 ch rx 25.71
volt sensor 2.55
s h 5.75
total 34.01
that is it: 34.01 per plane!

(the tx is from hk, the rest from aloft hobbies)
Posted by phil alvirez | Sep 01, 2012 @ 02:40 AM | 5,566 Views
folks: i see that both terms are sometimes misused.

from wiki:
Decalage angle:
difference in angle of the chord line of the wing and the chord line of the horizontal stabilizer.

incidence:
Angle of incidence is a measure of the angle at which the wing or horizontal tail of an airplane is installed on the fuselage, measured relative to the axis of the fuselage.

just in case...
Posted by phil alvirez | Aug 17, 2012 @ 05:34 AM | 5,614 Views
i like to think of ideas as if they were swallows, swarming at my window, trying to get in. so many of them.
but i can let only 1 in, otherwise they will drive me crazy, so i watch them, until the 1 i want gets close and suddenly i open the window and let it in and close it. then it's time to work with it. sometimes there is a delay due to problems that i have to solve, be by thinking or trying, or asking for help at the net, or by ordering some materials, so i keep it inside until i can resume my work, and bring another in and start working on it.

but there are so many waiting for me to open the window...
Posted by phil alvirez | Jun 03, 2012 @ 03:10 PM | 6,496 Views
'smart is he who learns from his mistakes.
wise is he who learns from others' mistakes'.
when Gutemberg brought his idea of the printing press, people who knew something began to publish manuals about how to do or make something. and this was a giant step for learning faster, and humanity became more and more knowledgeable. our learning keeps growing exponentially. we learn way faster by watching others doing something-or reading about it, so we don't have to make the same mistakes that they did. humanity, like the most advanced species, learns from others. that's why we gather. wolves, elephants, lions, baboons, dingos, live in close proximity-and learn from each other. our advantage is that we are able to communicate better-the language-so we are able to tell with more detail and faster, whatever we want. then we learned to read and write-then, as i said, the press. now the internet. we exchange ideas. whatever we know, we let others know. so the others don't have to make the same mistakes we did. we invest time and money trying to learn something, and then we talk about our findings, so the others don't have to go through the same to learn that. of course, sometimes we want to try something that others couldn't make it work, and we are willing to try a different way. then, sometimes it does not work. but we have the knowledge of the way it does work, so we can go back to it. and now with the rcgroups, here we are, having fun and living like wizzards, just pressing a few keys and talking to everybody, wherever he is, and getting back his input in no time, to enjoy more and more this magnificent hobby of ours.
Posted by phil alvirez | Jun 03, 2012 @ 05:23 AM | 6,411 Views
switch guard to prevent accidental activation?
with so many switches all over the transmitters, it's easy to flip 1 inadvertently.
i was wondering if there is a way to install a guard to prevent this. or design the tx's in such a way that we can add them at will.
for instance, on full size airplanes that have an ejection seat, the switch that activates the ejection has a cover that has to be lifted, to avoid going away unexpectedly.
or perhaps an enterprising fellow can come out with an add-on that does not cost an arm and a leg?
i hope manufacturers see this and think about it.
and that they not only bring the expensive versions with them: all should have it.
it's safety-just safety.
i got a suggestion to google on ebay and found this: http://www.ebay.com/itm/FLIP-UP-COVE...-/250800634875
and this: http://www.summitracing.com/parts/PCO-5568PT/
i already ordered some of the 1st. just got them.they measure 5/8x1-5/8". too big!
they are great, but too large for our tx's. we need something-if it exists-no larger than 3/8x1". will try to get others and see.
Posted by phil alvirez | Jun 01, 2012 @ 06:58 PM | 6,389 Views
an old sage once told me:

it's useless to try to explain what human quality is.
if you have it, there is no need (to explain). you know what it is;
if you don't have it, you will never understand what it is.
Posted by phil alvirez | May 28, 2012 @ 06:30 AM | 5,774 Views
i have been doing ultra-micros for quite some time, and have enjoyed exchanging comments-and learning a lot-with all of you guys. i enjoy flying my um's by walking a few steps to my backyard, or to a park nearby, and so will keep doing it, but i can't find anything else to try. i have done motor/gearbox tests on all that i could find; i have designed conventional-all my Elf series in several sizes, including the slowest plane, the Snowflake. 3d-the Snowstang; canards-the Snow Fox, Snow Goose; bird-like-the Snow Owl; flying wings-Rondine, in 2 versions; and lately double deltas-the Diamante, and am having a ball flying them now and then.
but i can't bring any more contributions to the thread.
i am now doing 2 meter electric sailplanes, and again, learning a lot by designing, flying, testing, buying, and asking in the internet, and that is a new start for me. you can find me there anytime. http://www.rcgroups.com/scale-sailplanes-122/ http://www.rcgroups.com/electric-sailplanes-19/
so, thank all of you for your help and friendship. i will never forget the great times we spent talking about so many things.
Posted by phil alvirez | May 25, 2012 @ 09:54 AM | 5,718 Views
now that i have started several projects using hybrid components i have become more aware of the differences between wood and foam; their advantages and disadvantages; their limitations. i want to build some sailplanes with modern lines, hence using some fuselages already made of foam or glass, but with wing and stab of my own design, with open frame, made of balsa, and iron-on covering.

the main difference is that with foam/glass the stress is spread uniformly, whilst with wood it is concentrated on joints. there are modelers who, like me, have been building long before any other material than balsa was known, but i have been interested in the development of new ideas and materials. at the beginning there were some attempts to introduce molded plastic, but it was too heavy if was strong enough. now with the advent of eps, epp, epo (and who knows what is around the corner), things have changed. and with so many planes ready (or almost) to fly, some of wood and others from foam, it easy to see why foam wins: it is made to survive crashes way better than wood. and if you want to build something new, foam allows you to do it way faster-and requires less parts, in general less precision-and survive impacts much better. besides easier to repair. in recent times i have designed and tested so many planes that if made of balsa would take me 10 times longer.

so, there is a place for everything and every1: if you want to build that scale plane with all the details, and you no...Continue Reading