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Old Jan 06, 2015, 01:05 PM
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Ambitious Project (From a beginners view)

Hi I'm in an high school Aerospace engineering program and my group and i have decided to design create a scale fixed wing ultra light from scratch. We haven't ironed out any of the details quite yet (constraints\criteria, materials, budget, etc), but from some of our discussions i can make an assumption that we want a gas or glow engine, aluminum or carbon fiber(probably just aluminum or a mix) frame, and budget is probably about 800$ max (and that's shooting a little high), and the wing span anywhere fro 6~8 feet. Like i said before all of that is an assumption, but hopefully it will be enough to help you answer some of my following questions. Also i should mention while we built a balsa rc with about a 4 foot wing span it was electric and we haven't touched gas or glow so the more very basic and more advanced information the better.
- What type of motor (gas\glow) would likely be best?
- What problems should we expect?
- Where can we get lots of information in one place? (other than forums)
This is likely my first post of many so what other questions should i be asking and what other information should i be looking for?

Also if you are fairly knowledgeable about scratch builds and gas\glow engines and would like help us out (mostly answer questions)and watch our project unfold say so in your response.

Thanks!
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Old Jan 06, 2015, 02:19 PM
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If you go carbon fiber you will need a special receiver. I don't know what equipment you already have, but you might easily go over budget , especially if you don't have a radio yet.

Where can we get lots of information in one place? (other than forums)
That's easy, go to your local rc club. You might even get some inexpensive or donated gear.
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Old Jan 06, 2015, 02:59 PM
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For short-term budget reasons, I think you'll need to go with a 2 stroke glow engine in the .60 size range. Used, will save you a ton of money over gas. For an Ultralight, you'll appreciate not having to accommodate the ignition of a gasoline engine.
If you're using aluminum, how are you expecting to form it? Tubular aluminum and solder? I'm interested in how you plan to do this. Not because I think you cannot, but because I want to learn something.
As mentioned before, visit a local hobby shop that has lots of wooden airplanes on the shelves or ceiling. There will likely be someone who is familiar with scratch building and will appreciate what you are trying to do. Also, local flying fields. If the first field is filled with grumpy guys telling you it won't work, go to a different field!
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Old Jan 07, 2015, 10:25 AM
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If you're using aluminum, how are you expecting to form it? Tubular aluminum and solder? I'm interested in how you plan to do this. Not because I think you cannot, but because I want to learn something.
Thanks for the replies guys!

As to how we plan to form the frame, one of our mentors is very good with metal work and said he knows of a way to weld the aluminum which surprised me! So we know that will be part of it, but i'm sure we will need to use other methods as well.

Also if you could suggest some engines and places to purchase them that would be awesome!

How different is a gas Tx/Rx system than and electric system? Will we be able to use our spektrum 8ch?
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Old Jan 07, 2015, 11:21 AM
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Originally Posted by Kickero View Post
Thanks for the replies guys!

As to how we plan to form the frame, one of our mentors is very good with metal work and said he knows of a way to weld the aluminum which surprised me! So we know that will be part of it, but i'm sure we will need to use other methods as well.

Also if you could suggest some engines and places to purchase them that would be awesome!

How different is a gas Tx/Rx system than and electric system? Will we be able to use our spektrum 8ch?
The classifieds here are a great place for engines at good prices. To be fairly sure that you're getting something that won't be a headache, look for something NIB (New, in box). Here's a winner: http://www.rcgroups.com/forums/showthread.php?t=2315892
Get some 10% nitro glow fuel with a synthetic/castor blend of oil and go learn about engines!
If you'd prefer to purchase from a retailer, Tower Hobbies is a reputable source. Alternatively, Hobby King is a souce that is significantly cheaper but quality and service can be hit-or-miss.
So, my recommendation for that particular engine size is based on trainer airplanes with that kind of wingspan that fly well on anything from a .46 to .65. I'm assuming that an ultralight design would be a floater, similar to a trainer. Wing area and other factors go into this. A popular 60-class trainer has 890 square inches of wing area with a high-lift semi-symmetrical airfoil. That plane weighs around 8 lbs.
Your TX/RX will work fine. You'll just have to add a battery pack and on/off switch for the RX. Since you probably already have a multi-chemistry charger, I'd recommend a LiFe battery in the 800mAh range. LiPo batteries could be made to work with a voltage regulator, but I'd recommend keeping it simple. Your requirements for battery capacity could change if marathon flights with lots of servos are a goal, but otherwise it should be plenty. I know someone mentioned needing a special RX for a carbon fiber framed airplane. I don't know anything about that, so hopefully they can clarify.
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Old Jan 07, 2015, 11:49 AM
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I know someone mentioned needing a special RX for a carbon fiber framed airplane. I don't know anything about that, so hopefully they can clarify.
If you go Carbon fiber vs aluminum, it is known to block the signal. They make special rcvrs for it.

This is a link to spektrum's CF receiver.
http://www.spektrumrc.com/Products/D...odID=SPMAR6260

Of course if you go aluminum you should not have that issue. Just be certain to get a receiver with a satellite. It is an extra little piece that you put as far as practical from the main receiver with its antenna oriented differently from the main unit's. It will give another path for the signal to get to the receiver in-case something blocks the main receiver.

I had one concern from los's reply and I admit I'm not sure if it is a factor or not. You say it is an ultralight, but what exactly does that mean. Are you modeling off of a full scale (non rc) ultralight, or do you intend your model to BE ultra light.

I say this because I do not know if a 60 size engine will be enough if you use aluminum. It might work if you only use it for certain parts, but if you sheet the fuse and or wings it may be too heavy. I know there are others here who can chime in there.

Edit: +1 on a LiFe (or called LiFePo4) battery. All my nitro models now use them.
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Old Jan 07, 2015, 01:06 PM
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it will be more similar to a real ultra light's design.
we may look into a carbon fiber rcvr because weight has been a concern of ours...
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Old Jan 07, 2015, 01:23 PM
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Like this:
http://www.aopa.org/images/lgf/Ultralight.jpg
Or like this:
http://upload.wikimedia.org/wikipedi...kemble_arp.jpg
?
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Old Jan 07, 2015, 01:46 PM
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more like the first one crossed with this
http://www.ultralightnews.com/ssulbg...eronautics.jpg
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Old Jan 07, 2015, 01:59 PM
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Will be an interesting build! In the bottom picture, i see a conventional wing vs. A simpler undercambered wing. Perhaps build the wing out of wood for weight?
Keep the overall dry (no fuel) weight under 10 lbs and around 900 Sq in of wing area and you should be good ... I'd think.
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Old Jan 07, 2015, 09:35 PM
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What a great project!!! Where are you located? There may be some builders locally that could steer you towards help/donated supplies in your area. I have to second the recommendation of contacting your closest RC club. you can look them up on AMA's website http://www.modelaircraft.org/
Most clubs have the email of the officers listed and they are a great resource if needed. Also, having someone local would give a chance for an experienced modeler to lay eyes on your project if necessary.

Good luck with your build and I look forward to seeing progress.
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Old Jan 08, 2015, 01:54 PM
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We're part of a school program that focuses on helping students venture into industries they think they maybe interested in wether its engineering, buisness, law, medicine, etc. We have a lot of freedom as far as what project we chose and where we decide to go with it. As far as where were located I can say that were in the Kansas City, KS area.
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Old Jan 25, 2015, 09:25 PM
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This sounds like a very interesting project. Please keep us informed on your progress. I have subscribed to this thread.

Glenn
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