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Apr 07, 2012, 09:31 AM
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phil's diamante -16"double delta for 6400 brick‏

double delta (diamond shaped) for 6400 brick or similar ultra-micro equipment. 16" ws, 192 sq in, 50 gr auw.
8mm brushed motor and 5.1" prop from 9 eagles; 1x160 cell. quick release for prop (kind of prop saver). prop is similar to hh's.
the idea is to have a compact, simple, light weight and maneurable airplane, with the shortest wingspan and largest area. diamond shape gets more area than the regular delta, with same span.
1st version is flat planform (no dihedral).
styrofoam is 3mm main and keel, 2mm elevons, 1mm front top and fin, .8mm cf pushrods.
elevons have air dams to channel air so it does not drift towards the center.
the keel serves several purposes: aerodynamically it provides directional stability, acting as an underfin. structurally it is the backbone that gives rigidity and links the front to the back. it also helps to launch it and protects it at landing. it is 1 of the factors that contributes to the stability of the plane. the others are the fin (vertical stabilizer), sweep back leading edge, step, and air dams.
second version has dihedral to add stability, a further forward cg, and a regular hh gearbox and 5.1 prop and rubber spinner.
the idea is to compare for stability and maneurability. later added a small stab.
got some short videos:
see more details on comments here
Last edited by phil alvirez; Apr 21, 2012 at 02:04 PM.
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Apr 07, 2012, 02:51 PM
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managed to get my son to film this early this morning near freezing. tried the diamante flat wing first. stable and maneurable, did loops and rolls with down input. next flew the dihedral version with further forward cg. i was expecting more stable flying but was not so. flies fine but seems more sensitive than the flat wing version. i have to try both more to reach conclusions.
Last edited by phil alvirez; Apr 07, 2012 at 03:02 PM.
Apr 17, 2012, 05:54 PM
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t tail

next added a small t tail to #1 with the purpose to improve stability. it is 2mm foam and weighs 1 gram.
as the fin is sweept back it has a long moment arm, and at the top clears the wing wake.

tested it and is more stable. did the same to #2 and improved too.
Last edited by phil alvirez; Apr 18, 2012 at 06:27 AM.
Apr 27, 2012, 03:45 PM
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testing dihedral

2nd version had 1" dihedral under each tip, to compare with #1 that is flat.
finally i was able to fully test both, with and without wind.
to my surprise, the flat version is more stable, so i removed the dihedral from #2 and tested again: now both fly the same, and even can handle some breeze.

still i have to find out why dihedral not only did not improved stability, but the flat version is more stable.

never faced anything like this.
that's why is necessary to do whole field tests to see how really things work.

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