John is right, you want to maximize L/D. Drag is composed of Profile (skin friction) & Induced (generating Lift).
Profile drag is reduced with high speed, wide chord and zero thickness of a cambered plate (maybe 4%).
Conversely Induced drag declines with higher aspect ratio or large span and narrow chord.
Put the 2 together and you get big and heavy.
Don't know the restrictions, but an F1A size would be 10' span, 4" chord (30:1 AR) and weigh a pound or more.
Wing on low pylon, with skinny fuse & maybe 10% stab. Generous dihedral (ideally curved) and good sized rudder should help keep it going straight. Molded Carbon Fiber best for getting sufficient stiffness.
Doubling the size & jacking up the weight should be even better, and get you tossed out even faster for not only violating the spirit of the competition, but also the hole in the wall.
Good luck,
H
To: Indoor_Construction_at_yahoogroups.com
From: john_kagan_at_hotmail.com
Date: Fri, 27 Aug 2010 21:10:39 +0000
Subject: [Indoor_Construction] Re: Indoor towline?
Having some experience with F3B (multi-task r/c gliders), I'd point out that you are seeking max L/D (distance), instead of the min sink (duration) that most other indoor glider designs are going for.
Built up and light might not be the way to go. Molded / solid surfaces, with more mass, might be better.
A built-up Gentle Lady sailplane might out-duration my molded F3B ship in dead air (assuming similar launch height, which isn't a good assumption), but it sure isn't going to out-distance it :)
Unfortunately, that's about the extent of my sailplane knowledge. Maybe one of the aerodynamicists here can chime in.
--- In Indoor_Construction_at_yahoogroups.com, Manuel Cisneros <macs8953_at_...> wrote:
>
> Over the last couple of years I have built a couple of specialized
> gliders for a friend of mine who's company has a yearly contest that
> involves tossing a glider off a 20' platform inside a large atrium and
> awarding a prize to the glider that goes the longest distance. The
> atrium is ~250' X 80' and about 40' tall. No, the atrium is not open to
> the public and is only usable for the glider contest as it involves
> flying a straight line across the length of the atrium, anything that
> circles doesn't do too well, I've tried.
>
>
>
> The gliders I've built are based on Oldenkamp's Zweibox, I think the
> lines (curves?) of this glider are aesthetically superior to most other
> HLG/CLG/DLG designs I've seen. I stretch the wing to 22" but otherwise
> the planform is per the original plan from MAN. The wing is 1/8" sheet
> with molded in undercamber and polyhedral, the tail feathers are 1/32"
> thinned at the tip to near translucency, and the fues is medium 3/32".
> This results in a glider that flies the length of the atrium and
> consistently hits the opposite wall at about 5'-6'.
>
>
>
> The first year one of these gliders was flown at the contest the 2nd
> place glider flew about halfway across the atrium, as I mentioned above,
> my glider hit the opposite wall. The next year someone entered a glider
> that made it almost all the way across the atrium, landing about 5'
> short of the wall. Last year another glider hit the wall about 3' below
> my most recent glider, I took this as a slap in the face and am about to
> start building a new glider for this year's contest.
>
>
>
> What I am shooting for is building a glider that will hit the opposite
> wall at around 10' (25:1 glide ratio). I'm not sure if this is
> possible, but I'm going to try.
>
>
>
> I think an indoor style, built-up design is the way to go. Does anyone
> have any pointers at indoor towline designs I can take a look at? Since
> these gliders are suppose to be tossed rather than launched (the spirit
> of the contest is such that the glider never goes above launch height)
> the model only has to be sturdy enough to survive gliding, not launching.
>
>
>
> Any ideas?
>
>
>
> Manuel.
>
Received on Sat Aug 28 2010 - 03:07:57 CEST
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