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Old Jan 25, 2004, 05:04 PM
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Here's The New AP Plane I'm Building...Would like Some Opinions On Wing Design

Hello,

I've been throwing this thing together for a couple of weeks to accommodate my DV3100. I'm nearly ready to start building the wing and can't decide what's best. The wing will definitely be constructed from blue fanfold foam with carbon arrow spars. Most likely will be in the 60" range with a 7" chord since I am using 7 x 20 baked wing panels. I can't decide whether to make it under cambered or flat bottomed or how the dihedral will be. Looks like the AUW will be about 30 to 32 oz and will be powered with a geared sp 400 for now. I usually like to fly powered up to a high altitude and then glide down while taking shots so good glide capabilities are a must. Unfortunately the shutter speed on this camera is slow like the Pencam so I'll need to be able to slow the plane down as well. Any opinions? Here's some pictures.
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Old Jan 25, 2004, 05:06 PM
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Another.
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Old Jan 25, 2004, 05:09 PM
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Here's my plane that houses my Pencam. Should I make the new wing dihedral like this?
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Old Jan 25, 2004, 05:14 PM
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Or should I make the dihedral more like this Skimmer?
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Last edited by Randy Due; Jan 25, 2004 at 05:17 PM.
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Old Jan 25, 2004, 05:20 PM
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Oops I meant that Skimmer to be a jpg!
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Old Jan 25, 2004, 05:31 PM
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Flat bottom will work as well as anything on that small a wing.
Dihedral, as long as there's enough of, either choice will also work.
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Old Jan 25, 2004, 06:37 PM
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Thanks. I wondered if there would really be much difference. I thought I had read somewhere that the more evenly curved the wing looked (from the front or back), the better it would perform as a glider type of plane. I wasn't sure if this was a noticeable difference in a slow moving design. I failed to mention that the plane will be rudder elevator with no ailerons, but I guess you assumed that. I'm working on the rudder and elevator now and should be able to start the wing in a day or two.

Randy
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Old Jan 25, 2004, 07:50 PM
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I like polyhedral like your first pic because I always feel that I can brace it easier and sturdier than a simple V.
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Old Jan 25, 2004, 10:31 PM
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I bet some others will chime in here but my understanding is that undercambered wings work best for very light wingloading. they generate a lot of lift at slow airspeeds, but also generate a lot of drag. Because the wingloading you are proposing is about 10oz/sq ft that is a little too high for a undercambered wing IMHO. As wingloading goes up, stall speed goes up. to maintain flying speed you will need more power input...

I have made flat bottomed wings that worked very well from fan fold. flat bottomed will give more lift than a symmetrical design..

Dihedral will be hard to make a spar. You might try a high winged flat design first... the high wing should give some positive stability like dihedral will. It might be enough and will be a lot easier to make a strong wing...
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Old Jan 25, 2004, 11:52 PM
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<I like polyhedral like your first pic because I always feel that I can brace it easier and sturdier than a simple V.>

fdisk,

You are right there. That's the main reason I built the wing in the first pic polyhedral. It is definitely easier to brace it. Also, the center section of that wing is flat bottom and the tips are undercambered. It made a very strong and stable flyer. If I use that design on this plane, I will have to re-route my bracing because my camera mount/ball will be in the way, but it can be done.

downeym,

You may be right about being too heavy for the high drag undercambered wing, especially since I'll be a little underpowered for now. I still haven't made the brushless plunge, but probably will soon. I run my other plane on 2s2p lipos with a 6v sp400 geared. It weighs in at about 26 oz and is really about all it can handle. I wonder how long a 7.2v sp400 would hold up with 3 cell lipo? Anyway it may be worth the extra ounce or two I'll gain to make the new wing flat bottomed and try three cells until I change to brushless. My only real concern with that is I'm not sure if I can slow it down enough for the slower shutter speeds.

Randy
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Old Jan 26, 2004, 06:39 AM
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in my experience the speed of the plane is not the major factor with the shutter speed... I have never had a blurry shot from going too fast.. usually the issues are related with vibration and prop balance...

I think a 7.2V motor will be ok with a 3s LiPo, but make sure that you prop it for less than 10A. check your temp on the first flight too. If the motor is not getting hot then you are ok...

if you use a flat bottomed wing you can even use a strip of foam as the spar.. I have dont this in the past and the wing has held up fine... here is a picture of a camera plane I made that used a flat bottomed wing, foam spar (with some strapping tabe), and had a wingspan of 6'!
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Old Jan 26, 2004, 11:30 AM
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Downey, specs on the plane!
NOW!
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Old Jan 26, 2004, 12:54 PM
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Yeah downeyman, what's it powered with. Give us the scoop!

Randy
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Old Jan 26, 2004, 01:40 PM
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Randy Due,

Give us some more details on your fuse and camera mount. It looks nice. Is the fuse fiberglass ??
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Old Jan 26, 2004, 03:10 PM
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Zoomzoom,

The fuse is blue fanfold foam, spackled, one coat of water based pu, and painted with water based acrylic paint. Colored packing tape for trim. The camera mount is 2 floral/craft foam ball halves with the same coatings as above. I carved out the inside to accomodate the camera. The ball is inserted into the socket in the fuse and can rotate to nearly any angle. Friction holds it in place since it's a tight fit. I haven't tested this mount yet, but it feels rock solid and gives the camera good protection. Wiring will exit the ball from a hole or slot in the side. The back has a slot for cf card access. I did remove the camera from it's original casing first. Originally, I had the idea to mount the camera into a can shaped housing formed from foam, but decided the ball would be more versatile. If I had thought of this first, I may have made the plane a pusher and placed the ball more forward and lower so as to be able to take straight on video if I wanted to. Oh well, it still will aim about 15 or 20 degr. from forward. I'll post some pictures later on of the ball mount.

Randy
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