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Author Topic: i mtr solid balsa wing wing dlg  (Read 764 times)
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roxy2
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« on: July 15, 2017, 12:13:55 AM »

i have a whipit micro dlg glider that i enjoy for park flying at leisure and have built a solid balsa wing for it so i can get higher throws and more air time.
I know this has all been done before and yes it works very well. Because i like building and experimenting i have gone ahead and made a 1mtr wing and built a fuselage using a carbon tube. It is a 2 channel with rudder and elevator. I am using guitar B strings for the push rods and have sleeved them on the outside of the boom. so far the weight of the wing and tail is at 72.8 grams. I need to aim for 85-95 grams all up to keep it light.
my problem is finding a receiver that can bind to my DSM2/DSMX transmitter that comes with the Horizon Champ RTF micro.
Is there a receiver out there that can run off  a 3.7 v lipo like the Elite 1S3.7V 150mAh and what could one use for servos?
Any advise would be appreciated Roll Eyes   
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Footloose
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« Reply #1 on: July 15, 2017, 03:06:49 PM »

You could take a look a Micron Radio Control www.micronradiocontrol.co.uk

They will post to overseas destinations

Bert
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Yak 52
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« Reply #2 on: July 16, 2017, 01:54:32 AM »

I use banggood redcon 4 channel rx's for this sort of thing https://m.banggood.com/REDCON-CM421-2_4G-4CH-Full-Range-DSM2-Receiver-Spektrum-JR-Compatible-p-1015760.html although the Orange R410X is very similar. I've had amazing range from these (over 500m) when correctly installed away from servos and motors etc. You can also remove the pins and solder directly to them which gets the weight down to around a gram (the pins and servo plugs are where the weight is.)

I'm not sure if they will bind to the TX you mention - it probably depends on the age. I seem to remember the newer models can rebind to a DSM2/X transmitter so it may be possible. If you intend on building a few models like this it's well worth getting set up with something like a Spektrum DX6i which has model memories and some basic mixes.

All the DSM2/X receivers should run on 3.7V but you need a decent capacity battery to avoid low voltage. The brown out voltage is then avoided. I would suggest 300mah since you will need the noseweight anyway.

Servos depend on the size of the control surfaces, a good servo torque calculator can give an idea (online ones available) but anything from a good 2.5g Emax ES9251 through to 4-5g servos such as ES9051, Gening or Turnigy 1370A depending on the size of the model and budget.

85-95g is a low target weight for a 1m DLG, the Elf is 95-100g and is exceptional. The Strike 2 is 110-115g. My own solid wing 1m came in at 140g but was designed to be beefy Smiley I would also use pull/spring control rather than pushrods and save some weight in the tail.

Look forward to some pics!

Jon
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roxy2
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« Reply #3 on: July 16, 2017, 03:25:57 AM »

Thanks for the info.
Those servos you mentioned will they run on 3.7v lipo and have enough torque? I guess this is where i need to use a calculator.
I made the tail and rudder reasonably small so they would not require too much torque.
Also i might change to pull controls as i feel it may be a tad tail heavy.
On a totally different subject what makes a wing fly faster or slower? Airfoil thickness or where the C/G is on the wing?
Do other things come into play like weight, airfoil profile and length of fuselage.
« Last Edit: July 16, 2017, 04:23:44 AM by roxy2 » Logged
OZPAF
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« Reply #4 on: July 16, 2017, 08:57:01 PM »

The flying speed,or more accurately the range of flying speed from stall to high speed, depends on the wing loading .

The trimmed angle of attack of the wing will determine the exact flying speed within this range as it establishes how hard the wing is working - ie it's operating coefficient of lift.

Airfoil characteristics determine how well that airfoil will work at the chosen wing loading and angle of attack, for those speeds and Reynolds numbers.

The Cg 's main purpose is to establish the model's stability and response  and to a lesser extent it's trim loads.

I have only touched on the subject but a bit of research on the web and here on HPA would help you to understand more about this.

I would suggest for what you are doing would be to keep the airfoil fairly thin (4-5%), about 2% camber or so and preferably use one of Mark Drela's airfoils.

Jon -YAK52, above has a similar design here on HPA.

John
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Yak 52
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« Reply #5 on: July 18, 2017, 04:41:19 AM »

Plus one on what John said but to summarise:

It's not just about the speed of the model it's about how well it goes at a certain speed. A lightweight model with plenty of camber in the airfoil will be 'good' (low sink rate) at slow speed and thermal well but not be so good on windy days. A heavier model with less camber will have a good flat fast glide and be better at getting between thermals (through sink) and getting back to you in some wind but a bit harder to thermal with.

It's not easy to have both of course, which is why refined designs use camber changing flaps. Making some provision for adding ballast will give you the option to add some speed in windier weather.

John's suggestion of 5% thick and 2% camber is a good compromise. The best airfoils for this sort of thing have some undercamber and take some effort to build accurately but a flat bottom (AG03, BE5017FB) can work well. Have a look at http://charlesriverrc.org/articles/apogeehlg/markdrela_apogeehlg.htm for Mark Drela's benchmark design, which is the basis for the Elf.

CG position and tail length don't play a direct role in speed but it is important to get these right for a good design.

Jon
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lincoln
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« Reply #6 on: July 20, 2017, 08:40:18 PM »

I've flown several of other people's Apogees, mostly Mark Drela's. I own an Elf. The plans for the 1 meter Apogee state 120 grams, though it used heavier gear than we'd use now. I recall being impressed with how it flew at that weight. While the Elf is reasonably good, and moderately fast, in many circumstances I think it would be better with a little more weight! It uses D47's and a Tenergy 160mAh lipo with a tiny connector on it. The D47's are overkill, as they'll handle a 1.5 meter DLG, but they work well.  The receiver is, I think, some Spektrum receiver or other. The two antennas stick out in a v which is bad for the aerodynamics, but the fuselage is too small to get two inside at 90 degrees to each other. I hesitate to take the wing off and look at it, because it's a bit tricky getting it back on without squishing something or having a wire stick out. I am using a DX5e transmitter, but I wouldn't use it for anything larger that I might fly further away, or for something more expensive. I've had problems with these when flying at medium (for a two meter RC glider) distances. Once, I had a problem with an electric model at about 100 feet!

Perhaps they've fixed the problem, but I've seen a couple of what I think were those Champs go out of range at moderate distances, perhaps as little as 200 feet.You need more than that, IMHO, for even a 1 meter DLG.
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roxy2
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« Reply #7 on: July 22, 2017, 06:23:04 AM »

 Undecided You do have a point there. Maybe i should just use my Futaba 6EX transmitter with the Fasst receiver.
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