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Model Forum / Radio Controlled / Air Models / September 2006My First Design...
Howdy Folks, I've been building and flying for a few years, and have a few ideas for a scratch design and build project. I'm looking for some help for the process though. Any websites regarding designing and building (and flight testing) a new design would be greatly appreciated. Basically, I've got a few sketches with what look like the right proprotions, but want to save myself some grief by learning from others' mistakes as it were. TIA Steve Depends how much you want to experiment.. if a pizza box will fly, I guess most things will work if it looks like any kind of airplane... I know people who have taken mismatched fuse, tail, wing, and cobbled them together (parts from previous 'mishaps') to make a plane that flew quite nicely...... all you need are the basics.. az21 . > Howdy Folks, > [quoted text clipped - 11 lines] > TIA > Steve > Howdy Folks, > [quoted text clipped - 11 lines] > TIA > Steve www.rcgroups.com Hi, > www.rcgroups.com Yeah, been working through that site a lot, but to be honest, it's so full of stuff, it gets to be daunting at times. Thanks Steve >Any websites regarding designing and building (and flight testing) a new >design would be greatly appreciated. I don't know of an all-in-one site. I've collected lots of articles on design from magazines. I'm maybe 1/3 of the way through designing and building a utility/trainer/sport plane. The fuselage is framed up and very partly planked; the empennage is done; the wing cores are cut. Still a long way to go, however. I want to fiberglass it and paint it with latex. My theory is to use features from other kits that I've built and/or flown and liked. I'm more or less vamping off a plane I crashed (a Road Runner), except I'm using foam-core empennage, a foam wing, and an airfoil that I picked out of an airfoil drawing program (Profili). The landing gear is the same. Marty You'd do well to read [i]The Basics of Model Aircraft Design[/i] by Andy Lennon, available through [i]Model Airplane News[/i], or possible at your local library. It gives a good basic understanding of model aerodynamics and design criteria. However, just copying the basic moments and areas of an existing successful design, but playing with shapes can provide you with a highly individualistic looking plane that's pretty sure to fly decently. Hi, > You'd do well to read [i]The Basics of Model Aircraft Design[/i] by > Andy Lennon, available through [i]Model Airplane News[/i], or possible > at your local library. It gives a good basic understanding of model > aerodynamics and design criteria. Got one on order, thanks for the pointer. > However, just copying the basic > moments and areas of an existing successful design, but playing with > shapes can provide you with a highly individualistic looking plane > that's pretty sure to fly decently. Good point too. My first design is pretty basic, a low-wing, inverted Gull wing to be exact ala an F4U- Corsair, so I'm building and flying a GWS Corsair as my next model so I can see how that type of wing flies. One of my questions (hopefully answered in the book) is the tail section. How big (compared to the wing), how much vertical tail, and rudder response (travel) will I need etc. The other big question, is that the fuselage itself is somewhat airfoil shaped, so I'm trying to determine how much that contributes to the lift vector. Should I consider it another wing section and work things out, or am I over complicating things just a bit? Thanks for any and all input. Steve >The other big question, is that the fuselage itself is somewhat airfoil >shaped, so I'm trying to determine how much that contributes to the lift >vector. Should I consider it another wing section and work things out, >or am I over complicating things just a bit? You can answer that question by building a small balsa glider that is a scale model of your design. Set the glider's CG for just the wing only. If that doesn't seem to work well, then it may be an indicator that the fuselage is, in fact, contributing lift as well. Marty > You can answer that question by building a small balsa glider > that is a scale model of your design. > > Set the glider's CG for just the wing only. If that doesn't seem > to work well, then it may be an indicator that the fuselage > is, in fact, contributing lift as well. Good idea Marty! Steve >Good point too. My first design is pretty basic, a low-wing, inverted >Gull wing to be exact ala an F4U- Corsair, Interesting! I'm building a little electric sport model with an inverted gull wing too! It's based on the Supermarine 224, not the Corsair. BTW, the 224 was the first "Spitfire," but the one we all know by that name was Supermarine's type 300. The 224 was a dog, but kinda neat looking from some angles. >One of my questions (hopefully answered in the book) is the tail >section. How big (compared to the wing), how much vertical tail, and >rudder response (travel) will I need etc. "Scale effect" is the term that deals with the tail's area compared to the wing area between the full sized airplane and a model of it. Generally models need a bit more tail surface for proper control. You'll also find that a very slab-sided fuselage (hence more surface area) needs less vertical stabiliser, and flys knife edges better, since the fuselage does act as a lifting surface when on its side. Marty's suggestion is right on! An aeronautical engineer told me the same. Since they do it at NASA, we may as well do it too! :-) Rough rule of thumb is to make the horizontal tail 25% of the wing area and the vertical tail 15% of the wing. Forget about predicting the lift of the fuselage. Remember to extend the wing panels to meet at the fuse centerline to estimate wing area. You can take the following link for a trainer design and modify it to your unique design. http://sky.prohosting.com/air2/design.htm > Hi, > [quoted text clipped - 25 lines] > Thanks for any and all input. > Steve Hi Marlowe, > Rough rule of thumb is to make the horizontal tail 25% of the wing > area and the vertical tail 15% of the wing. Forget about predicting > the lift of the fuselage. Remember to extend the wing panels to meet > at the fuse centerline to estimate wing area. You can take the > following link for a trainer design and modify it to your unique > design. http://sky.prohosting.com/air2/design.htm Thanks for the post, and great link. The book I ordered arrived, so I'm now slogging through definitions of Reynolds numbers etc. Hopefully I'll be able to build a small foamy toss glider of the basic design soon to see if it'll work. Steve > Hi Marlowe, > [quoted text clipped - 12 lines] > > Steve Reynolds numbers do not scale properly and are nearly meaningless for most model sizes. Sorry. However, it is good reading if you are into full scale aircraft. IIRC, the B-26 flew with a wing loading of 58 lbs. per square foot. This is an impossible figure to achieve in model flight. No wonder they called it "The Widow Maker". From what I understand, this title was also shared with the F-104 Star Fighter and several other high wing loading aircraft. Ed Cregger You never seen Major Brothers fly the F104 apparently! Roy >> Hi Marlowe, >> [quoted text clipped - 27 lines] > > Ed Cregger  SignatureUsing Opera's revolutionary e-mail client: http://www.opera.com/mail/ > You never seen Major Brothers fly the F104 apparently! > > Roy Maybe not, but I saw and heard my share of F-104s at Luke AFB in AZ between 65 and 69. I can still recognize them by sound only. Ed Cregger He was one of the first Air Force pilots to be assigned to the "missle with a man" 104's at Lockeed. I swear that he know more about how that aircraft would fly then the engineers. His favorite take off pattern was to start his roll from the end of the runway lift up about 20 feet, clean the plane up then go verticle to 60 angels at about the 2000 ft marker (opposite end of runway). Yes the 104's had a distinct sound to them and Major Brothers had a unique way of handling the throttle so you could always tell it was him that was taxing out to the runway. If someone would have made a bet on how long you could keep the nose of a 104 up during landing I would have lost the bet. Major Brothers brought one in with the nose wheel up he touched down (gingerly) and kept the nose of the plane up almost the entire runway. One of the maintenance men told me that the only damage was to the nose wheel door when it scraped the runway! Roy >> You never seen Major Brothers fly the F104 apparently! >> [quoted text clipped - 5 lines] > > Ed Cregger SignatureUsing Opera's revolutionary e-mail client: http://www.opera.com/mail/ An interesting Skunkworks project used the F-104 as the base design of the glider-winged U2. Bill(oc) Also used a modified B57 at Eglin AFB wings were about 60% longer then a normal B57. At the time didn't know why they had done this until the pictures for the U2 came out! Roy > An interesting Skunkworks project used the F-104 as the base design of > the glider-winged U2. > Bill(oc) SignatureUsing Opera's revolutionary e-mail client: http://www.opera.com/mail/ |
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