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Archive for March, 2013
Posted by phil alvirez | Mar 30, 2013 @ 05:49 PM | 7,409 Views
radios with nicads or similar.
i came back in 2006, just at the time when 2.4 was released. i got a DX6 and soon realized that the battery in the tx (8 nicad cells) didn't last long. then some1 released a 3 cells lipo for txs and have used it for 6 years, and since i have had no problems-with that radio.
last year i got 1 DX6i, that comes with 4 nicads, and used it with them. last season began to experience power failures. i had several planes crashing. i began exchanging rxs, then escs, replaced connectors for larger, also larger packs. nothing helped. then began to suspect the towers nearby were the cause. or the windmills that were installed not far away (they operate with microwaves). then 1 day when i landed, walked to my plane and at the moment i was going to switch the tx off i noticed that the screen was blank-and the switch still was on. i thought that my tx was history.
but at home i decided to check, starting with the easiest thing. and when pressing the cells i noticed that the screen came back to life: it was a false contact! i decided to install a 2 cells lipo (the largest that fits is the 2x610-and i had it), so i did the mod similar to the way of the orange tx . (see last picture on the right). melted a rectangular hole and fitted a male connector, and adapted the pack to match. as i have a lipo charger that charges and balances at the same time, and am familiar with lipos, i didn't have to get anything else. now the radio operates flawlessly. i strongly recommend to do this to all radios that use batteries of single cells, as are prone to have false contacts unexpectedly, as happened to me.
Posted by phil alvirez | Mar 30, 2013 @ 12:20 PM | 9,321 Views
(see conclusions at the end)
Lynx was developed to find out if a sailplane with 1.5 meters wingspan and same weight and wing area than a 2 meters (like the Rex) can get into smaller diameter thermals.
the 460 sq in wing that sits on top of the fuselage and is held in place with 1 nylon bolt, has an undercambered airfoil with 8" constant chord and tips tapered to 5", 4 polyhedral panels. over/under 1/8x1/4 spruce spars with 1/64 ply webs, 1/16 'v' shaped trailing edge, 1/8 carbon fiber tubing leading edge and 3-1/16x1/8 spruce turbulators. covering is ultracote transparent orange; the auw is 510 grams with a 2x1000 pack.
the fuselage is made from the foam remainders of the 1st fuselage from the Thermal Rex, that was replaced with a spare that i was lucky to get when i got the asw28.
the nose section was badly damaged, but from the wing trailing edge aft was in good shape, so i adapted a balsa and ply front section that runs from the trailing edge of the wing to the nose, using a foam insert between the trailing edge and leading edge so that section is solid foam. the sides and bottom are 1/8 balsa with 1/64 plywood, and i added a plastic canopy from sig mfg. motor/prop/spinner/esc/pack are the same as the Rex. when checking the elevator pushrod i learned that there was too much drag, due to the 's' shape trajectory, so i replaced it with a servo near the top of the fin. now i get a smooth, precise response.
i still have to have good weather to compare both, but from the preliminary short tests they are stable and perform well. it is going to be an interesting evaluation in thermals.

conclusions. fall, 2015
it was until now that i was able to fully evaluate this plane and compare with the way more popular 2 meters class.
and now i understand why: although it flies fine, the performance of the 2 meters is so much better that this size is hard to justify-unless you have space limitations.
Posted by phil alvirez | Mar 27, 2013 @ 06:23 PM | 6,697 Views
when i was doing indoor free flight i met some of the greatest folks ever. and got advice from the best. besides the technical, some gave me a point of view that is worth considering. Steve Brown, world champ, once asked me: are you having fun? i said 'yes', and he said 'good'. that was all.
another of the greats, Walt Van Gorder, when advising me about a plane said : 'it ain't easy. if it were, it wouldn't be fun'.
so there you have it. all about this hobby is making it fun, having fun doing whatever. nothing is easy or difficult: it's fun.
Posted by phil alvirez | Mar 27, 2013 @ 12:21 AM | 6,852 Views
the idea started when i was considering getting a fuselage of a sailplane similar to the ask 21 that i like very much, and design a wing/tail for thermaling, even if this means not looking scale-like. i just like the shape of modern sailplanes fuselages. so this means engineering the whole thing to match the fuselage, and it is not an easy task. after shopping for a suitable fuselage, i ended up buying first a 2 mt ask 21 from hobby king, and later an asw 28 from same source. then i decided to give them a try as they are, before discarding the wings and tayloring new sets for thermaling, with larger area and higher lift airfoils. the result was that both planes crashed several times due to strong tendency to tip stall. i tried improving them by adding dihedral to the '28, and then enlarging their wing area, but even if showed some improvement, still they were not pleasurable to fly, to say it mildly.
i have been able to work on the '28 wing. the new wing, that has more area, also uses a naca 6409 high lift airfoil that i have used extensively through the years, and polyhedral, and the results were a great improvement, and no more tip stall tendency. with this i even managed to get rid of the ailerons, so now i am able to do all that i need with only rudder and elevator.
see my blog. i will add more as i finish-and fly test-them.
Posted by phil alvirez | Mar 09, 2013 @ 11:08 AM | 7,381 Views
Maverick started with the availability at the time, of the fuselage/canopy/prop/spinner of the Dynamic-s, a hotliner with v-tail
i used the prop/spinner that come with it, and found a motor that looks close enough to the stock.
but the main difference is that i designed it for thermaling, with a larger wing, and t-tail instead of the v-tail.
as the v-tail comes with a wide base that works well for a t-tail, and the wiring for the servos, it made my life easier. mounting the wing on top, too.
the tail instal is similar to the Thermalis, except that there are no belcranks, and the elevator servo sits up near the stabilizer, with a direct-and short-pushrod that provides precise commands. the rudder servo sits at the bottom.
the wing is 8" chord and 5" tips, undercambered airfoil, and uses an over/under spar of 1/8x1/4 spruce with 1/64 ply webs, and 3 turbulators; the leading edge is 1/8 cf tubing with 1/8x1/4 balsa, and the trailing edge is 3/16x3/4 balsa. ribs are 1/16 hard balsa, has 1 center section flat, and is held in place with 2 nylon screws that fit into the stock mounts in the fuselage. the covering on top is transparent orange solarfilm and transparent red ultracote lite tips, the bottom is clear microlite.
i found the motor 35-36/910 kv, that weighs 117 grams, the closest to the stock, and it works fine. it delivers an enormous amount of power.
with 600 sq in and 830 grams auw, the wing loading is similar to the Thermalis, and the glide is good for...Continue Reading