http://www.rcgroups.com/forums Physics, Aerodynamics, Engineering, Circuitry, and other scientific discussions. en Sun, 22 Nov 2009 18:04:16 GMT vBulletin 60 http://www.rcgroups.com/forums/images/misc/rss.jpg http://www.rcgroups.com/forums http://www.rcgroups.com/forums/showthread.php?t=1146184&goto=newpost Sun, 22 Nov 2009 01:45:18 GMT I have been reading up on Scalloped wing. The question I have is how would you go about building a Scalloped wing? Any suggestion on how to start? Thanks! I have been reading up on Scalloped wing. The question I have is how would you go about building a Scalloped wing? Any suggestion on how to start?

Thanks! ]]> Modeling Science leadingedge http://www.rcgroups.com/forums/showthread.php?t=1146184 http://www.rcgroups.com/forums/showthread.php?t=1142825&goto=newpost Sun, 15 Nov 2009 20:08:39 GMT Hi, I'm trying to design a flying wing that can stay in the air at very slow speeds. My goal is a basic flying wing platform for UAV development that is also reasonably easy to fly when necessary for those without much rc experience.

I have run a few designs through XFLR5 using the MH45, MH61 and PW75 airfoils and have found the PW75 to be the best airfoil but all these designs seem to have trouble at very low speeds (The best I can do is around 5m/s while remaining stable).

Anyone have pointers for how to make a slow plane? I've found most of the flying wing airfoils are designed for faster flight and I can't seem to find one that matches what I want.

At the moment my design has a 1.4m wingspan, 30 degrees sweep and 7.2 degrees of washout. ]]> Modeling Science r691175002 http://www.rcgroups.com/forums/showthread.php?t=1142825 http://www.rcgroups.com/forums/showthread.php?t=1141374&goto=newpost Thu, 12 Nov 2009 23:05:59 GMT I have several different Nitroplane models. As you may be aware sometimes the instructions in a manual aren't always clear to us. Maybe because of mis-interpretation, incomplete sentences, or the "Chinese" logic barrier. I know that if you follow incorrect instructions or if you do not understand what is meant in the instructions, you'll be sure to get incorrect results. I've made a few mistakes myself.

I have The Ultimate 40 ... Is the C/G to be performed on the upper or lower wing? My guess is the lower wing. If my guess is wrong that means my first flight may leave me with a tooth-pick collection. I would be interested in any pre-flight set-up techniques and advice for this plane. If you have this plane ... how did you set it up? I'm not looking to go out and rip open the sky, but I don't want to rip open the ground any more than absolutely necessary either. I'm a casual flyer and would like to land in the same condition as I take off. I'm going to use the E-Flite power 46 w/Thunder Power-3850. Any ideas on the prop-size? This planes comes as a Nitro kit and I have a Super Tigre 40, and a Super Tigre 45 These aren't ready yet but it does take me back to another question about C/G ... When we install the fuel tank in the nitro application as designed by the factory. Does the C/G change when we fill the fuel tank? If so ... do we check C/G with a full tank or empty tank? Do we need to allow for this or change the location of the fuel tank. What is the rule here? Thank you for all help given. ]]> Modeling Science screilly http://www.rcgroups.com/forums/showthread.php?t=1141374 http://www.rcgroups.com/forums/showthread.php?t=1139807&goto=newpost Tue, 10 Nov 2009 01:00:56 GMT For this question allow me to give some data. Lets say that in still air and while using a constant power setting (on a powered aircraft of course ) in level flight the 5 lb airplane will fly at 60 mph. While going downwind in a wind of 20 mph we enter a turn from level flight into a bank of 60... For this question allow me to give some data. Lets say that in still air and while using a constant power setting (on a powered aircraft of course ) in level flight the 5 lb airplane will fly at 60 mph.

While going downwind in a wind of 20 mph we enter a turn from level flight into a bank of 60 degrees and turn 180 degrees in 3 sedonds, We have a G-meter in the plane that records the G-forces.

We repeat the same manuver but this time we enter the turn on the upwind leg. We turn 180 degrees in 3 seconds using a 60 degree bank.

We know that the ground speed upon entering these turns will be different.

Will the recorded G-Forces be different in the downwind entry from the upwind entry? ]]> Modeling Science Texas Buzzard http://www.rcgroups.com/forums/showthread.php?t=1139807 http://www.rcgroups.com/forums/showthread.php?t=1138277&goto=newpost Sat, 07 Nov 2009 01:42:43 GMT I am designing a scale 54" Tipsy Trainer. The airfoil is close to the Clark Y so I'll be using it. The scale aircraft uses a positive six degree insidence at the wing root and a 6 degree washout leaving the tip at 0. Is this to much for an R/c aircraft. what should I use? Also I am using a NACA 0009 for the tail. Scale is set a 0 degrees. Is 0 degrees good with a Clark Y or should I go to, say, plus one or two degrees? Thanks.. ]]> Modeling Science 170flyer http://www.rcgroups.com/forums/showthread.php?t=1138277 http://www.rcgroups.com/forums/showthread.php?t=1137360&goto=newpost Thu, 05 Nov 2009 07:13:15 GMT Greetings all, I have been searching this site as well as everywhere else I can think of trying to find some sort of calculator or equations relevant to a three-lifting surface configuration aircraft. I have plenty of info on a conventional and canard aircraft, but I do not think it would carry... Greetings all,
I have been searching this site as well as everywhere else I can think of trying to find some sort of calculator or equations relevant to a three-lifting surface configuration aircraft. I have plenty of info on a conventional and canard aircraft, but I do not think it would carry over to a three surface as far as tail moments, tail area etc.
If it would, my logic says to use the basic equations for a canard aircraft, then split the area between two two surface (fore and aft wings) as well as the moment arm.
Is this logical thinking or has all the Mountain Dew finally gone to my head? ]]> Modeling Science plane_tech http://www.rcgroups.com/forums/showthread.php?t=1137360 http://www.rcgroups.com/forums/showthread.php?t=1137137&goto=newpost Wed, 04 Nov 2009 20:48:48 GMT Does anyone know a realistic value for a typical bipe ?? I am looking for the total model drag coeiffient. I understabnd it varies a lot, but I need a starting point. Any ideas ?? Marion Does anyone know a realistic value for a typical bipe ?? I am looking for the total model drag coeiffient. I understabnd it varies a lot, but I need a starting point. Any ideas ??

Marion ]]> Modeling Science Marion http://www.rcgroups.com/forums/showthread.php?t=1137137 http://www.rcgroups.com/forums/showthread.php?t=1137100&goto=newpost Wed, 04 Nov 2009 19:52:54 GMT Hi everyone, ive just joined the forum as I am masters year aerospace engineering student building a UAV as part of a small group. My background is more closely related to computational design and optimisation, although we do have structures specialists, aerodynamicists for the respective design... Hi everyone, ive just joined the forum as I am masters year aerospace engineering student building a UAV as part of a small group. My background is more closely related to computational design and optimisation, although we do have structures specialists, aerodynamicists for the respective design areas and several lab technicians to handle the construction.

I am ofcourse, not very practical - my degree is almost entirely theory! Until now...Which brings me to my question!

I am currently in the inital design stage for this UAV. It currently looks like it will be a 3m wingspan, high wing, conventional tail, around 8kg mass (fueled), petrol pusher engine, experimental tiperon wingtip controls...

Id really like to get my hands on a ballpark figure for mass moment of inertia for an 8kg UAV with a 3m wingspan, with the engine close to the roll axis. It does not have to be accurate. Just a ballpark figure...

Further into the project, the model will get CADed, with true weights etc etc and then we will have an exact figure. But I have to specify the components before I can get the weights, and for that I need to know what kind of roll performance I can expect or would like.

So - can anyone help me with a really rough ballpark figure for the mass moment of inertia for a 3m wingspan, 8kg UAV?

Cheers,

Patrick ]]> Modeling Science alephnull http://www.rcgroups.com/forums/showthread.php?t=1137100 http://www.rcgroups.com/forums/showthread.php?t=1136882&goto=newpost Wed, 04 Nov 2009 06:11:52 GMT I am currently in the process of designing an aircraft for a project, and am trying to figure out whether or not it would be more advantages to run a single or twin engine setup. I havnt decided on whether or not it will be two in a pusher/puller or conventional twin engine. Anyway, sorry if its... I am currently in the process of designing an aircraft for a project, and am trying to figure out whether or not it would be more advantages to run a single or twin engine setup. I havnt decided on whether or not it will be two in a pusher/puller or conventional twin engine. Anyway, sorry if its beating a dead horse but search did not pull up too much for me. ]]> Modeling Science flyinazn10 http://www.rcgroups.com/forums/showthread.php?t=1136882 http://www.rcgroups.com/forums/showthread.php?t=1135749&goto=newpost Mon, 02 Nov 2009 08:34:53 GMT Hello, The fuselage drag is quite difficult to estimate, I guess due to its three-dimensional nature, flow separation, absence of Kutta condition (no trailing edge) etc. I read somewhere that one way to estimate fuselage drag is by wetted area, but is it a reliable procedure? I have this... Hello,

The fuselage drag is quite difficult to estimate, I guess due to its three-dimensional nature, flow separation, absence of Kutta condition (no trailing edge) etc. I read somewhere that one way to estimate fuselage drag is by wetted area, but is it a reliable procedure?

I have this question because on my sailplane the ratio of fuselage area to the wing+tail area is about 1:10, but increase in drag in comparison with XFLR5 calculations is 1:3. I think that XFLR5 results for wing+tail are quite reliable, as x-foil wing polar, used by XFLR5, is almost identical to the measured polar in the range of Cl I use.

Truffaldino ]]> Modeling Science truffaldino http://www.rcgroups.com/forums/showthread.php?t=1135749 http://www.rcgroups.com/forums/showthread.php?t=1135213&goto=newpost Sun, 01 Nov 2009 09:14:38 GMT Hi,

i am currently building a Fi-103 with an 72mm EDF unit.

Does anybody have an idea of how to make it "buzz"???
I want it to have this deep (and maybee loud??? :D ) sound of a original Fi-103/V1.

I was thinking of some plasit-strip that is vibrating inside the airstream of the EDF....

Any ideas??? ]]> Modeling Science HugePanic http://www.rcgroups.com/forums/showthread.php?t=1135213 http://www.rcgroups.com/forums/showthread.php?t=1133552&goto=newpost Thu, 29 Oct 2009 03:13:01 GMT http://www.youtube.com/watch?v=CPe1kk8A65g

So, golf balls have dimples to reduce drag.
My question is if RC's would benefit from this. Would dimples reduce drag enough to make a difference?

I apologize if this was a repeat thread. ]]> Modeling Science msim http://www.rcgroups.com/forums/showthread.php?t=1133552 http://www.rcgroups.com/forums/showthread.php?t=1133226&goto=newpost Wed, 28 Oct 2009 16:02:25 GMT Are there any rules of thumb for the ratio of fus length(tail) to wingspan? Joe Are there any rules of thumb for the ratio of fus length(tail) to wingspan?

Joe ]]> Modeling Science JoeSantora http://www.rcgroups.com/forums/showthread.php?t=1133226 http://www.rcgroups.com/forums/showthread.php?t=1132350&goto=newpost Mon, 26 Oct 2009 23:09:51 GMT The concept is this... We are undergrads at CSU building an airplane around new battery technology that will be hand launchable. The trouble is... none of us really know, or can find, the modelers rule of thumb for hand launchability... What we do know: The hand launch velocity is the... The concept is this... We are undergrads at CSU building an airplane around new battery technology that will be hand launchable. The trouble is... none of us really know, or can find, the modelers rule of thumb for hand launchability...

What we do know:

The hand launch velocity is the velocity required to lift the weight of the plane.

v = sqrt(m_flying*g/.5/rho/s/C_l)

Where m_flying is aircraft mass, g is gravity, rho is air density s is wing area and c_l is our lift coefficient.

Knowing velocity, we can then find wing area by varying mass.

Any ideas?

Nick ]]> Modeling Science CSUFCUAV http://www.rcgroups.com/forums/showthread.php?t=1132350 http://www.rcgroups.com/forums/showthread.php?t=1131686&goto=newpost Sun, 25 Oct 2009 20:59:43 GMT I'm designing a R/C model. How can I calculate the spacing between the ribs in the wing?

I'll appreciate your answers. ]]> Modeling Science Marcelo MA http://www.rcgroups.com/forums/showthread.php?t=1131686