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Old Jan 14, 2013, 07:20 PM
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smokey point, wash.
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Your fin/rudder is partially hidden by the sloping aft deck of the body, so it might want to be even taller. Might also try to bring the foward point of the fin back 10%, and ask for input as to the slanted hinge line -vs.- verticle hinge line.
I even drive myself nutz at times.....
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Old Jan 14, 2013, 07:31 PM
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haiduk's Avatar
Marysville, WA
Joined Oct 2008
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I adjusted the height of the fin and enlarged the rudder a bit. Puts the area slightly over 13% of the wing area. I am including the area within the fuselage.
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Old Jan 14, 2013, 07:38 PM
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Omaha Nebraska
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Duk,

I'll post the document later, busy helping cook dinner (my bread just went in the oven, ). Looking good.

Fred
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Old Jan 15, 2013, 02:47 AM
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Marysville, WA
Joined Oct 2008
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I sat down with pops this evening and we talked about the vertical fin on this aircraft. He didn't like the looks of any of them! We ended up stretching the fuselage about 3/4" to increase the overall tail moment. We also increased the rudder area. This makes for a more sleek look to the vertical fin. Bottom line, pops likes the way it looks now. That's important.
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Old Jan 15, 2013, 07:32 AM
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Omaha Nebraska
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I akso like the look. I do see what you are saying about the horizontal. I;d say make it a bi t larger, after all it is important for the designer to like what he sees! I shoot for around 20% area on the horizontal, but not as critical since your tail moment is good.

Fred
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Old Jan 16, 2013, 11:09 AM
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Marysville, WA
Joined Oct 2008
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I have been working on the horizontal stabilizer considering different ideas for fixing a looped tail skid (for streamer combat) or, as an option, a tail-wheel.

No "build photos" this time. I've been kinda not in the mood for dinking around on the computer. Just had half my toe removed. I'll get back up to speed in a few days I'm sure. Waiting for the Vicodin fog to clear.
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Old Jan 17, 2013, 01:38 AM
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Marysville, WA
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I've really got nothing better to do while waiting for my foot to heal but work on this design some more. Slowly but surely it's taking shape. Finally my pops and I see eye to eye on the shape. Now to finish the landing gear and tail wheel/skid.
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Old Jan 17, 2013, 02:08 AM
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Everett, Washington
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It's better looking than an Ugly Stick, love the tail shape,.. Good job! It sorta looks stealthy.
Streamer combat? Weather forecast for later next month,.... Raining balsa

Heal fast.

Fred
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Old Jan 17, 2013, 07:27 AM
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What the heck! Lost half of your toe? I do hope that you are doing OK, and that it's nothing serious, Take good care of that! Your design is looking great. I will still post the documents discussed, but I was helping one daughter move and building furniture all day while she was at work.

Fred
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Old Jan 17, 2013, 03:20 PM
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Marysville, WA
Joined Oct 2008
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Thanks guys, I should be fine. I'm just dealing with an antibiotic resistant infection. They had to cut away some of my toe to clean out the green stuff and remove dead flesh to save my foot. Hopefully, they got it all. Will be watching it over the next couple weeks. Diabetes sucks.

Anyway, I think these 1.75" wheels are just a bit small for the average park. I found some 2.5" dubro park wheels. I modeled those up. I think they are a more appropriate size for this plane.

I'd like to know how many of us have a copy of RealFlight G5 (or newer) and might be willing to help test the sim model when I get it to that point.
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Old Jan 17, 2013, 04:35 PM
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As promised, RC aircraft design parameters

Sorry Duk, I only have RealFlight 3.5. Got tired of buying the same software over and over......

Now...........

I promised to try and upload these documents on R/C design paremters. They work great. Do not let the high wing aircraft drawing fool you, the paremters work with mid and low wing aircraft also. I did not create these files but I do reference them often. Believe me, they work well.

If you want more control authority for say a 3D aircraft, change the control surface areas accordingly. Substitute your favorite electric motor in place of the IC motors shown, but he wing areas are good reference also for those starting their own designs.

Last in the text, the 600 SqIn wing they use is for examples. Use you own cord width, wing length, and wing area measurements as the starting point for your own caculations. Give it a try, you will forever have a better understanding on how all the parts of an aircraft relate to each other.

Fred

Here it is, but I also attached a Word Document if you want to download and save the file, or even print it out for later reference.. It is easier to read as the Word Document, so you may want to do that anyway.

Practical RC Model Design

Radio controlled model aircraft can be designed using some basic rules of thumb or more appropriately, design parameters These basic design parameters can be applied to a trainer or sport model. There are no complex or magic formulas to solve. These parameters have been proven to work by a multitude of sport models that have been developed using these rules. A modeler who has built a few models and has gained some knowledge of common structures can design a plane that suits his individual needs.


The design begins with selecting the size of engine that will be used. This will become the determining factor for the entire design. The wing area is first selected from the table.
**Electric motors can be substituted for IC engines shown. Many sources are available to help you decide which electric motor best matches a given IC Engine range.


Engine/Wing Area
ENGINE WING AREA
.049 200 - 250 sq. in.
.10 250 - 350 sq. in.
.15 300 - 450 sq. in.
.25 400 - 500 sq. in.
.40 500 - 700 sq. in.
.60 600 - 850 sq. in.

After selecting the engine size and wing area, the next step is to determine the wingspan and wing chord that will give this wing area and an aspect ratio between 5:1 and 6:1. If .40 size engine is selected, the wing area will be 500 - 700 sq. in. To make things simple, and area of 600 sq. in. and a span of 60" is chosen. This will give a chord of 10" and an aspect ratio of 6:1. The rest of the design will be based on the chord length.

The next step in determining the configuration of the wing is selecting the airfoil according to the purpose of the model.


Airfoil Type
AIRFOIL SHAPE CHARACTERISTIC
Flat Bottom Slow, docile, forgiving, poor inverted flight
Semi-symmetrical Good lift, penetration, aerobatic, and inverted flight
Symmetrical Best aerobatic and inverted flight

Programs can be downloaded that will draw one of a multitude of airfoils. Airfoils can also be plotted manually using the coordinate dimensions to draw points on the airfoil and drawing the curve of the airfoil using a French curve or flexible rule. The airfoil that is selected should have a thickness of 15% - 18% of the chord at 30% - 40% from the leading edge and should have a blunt leading edge for gentle stall characteristics. The wing incidence is normally set to 0. The dihedral will be 0 - 3 with ailerons and 3 - 5 without ailerons. Finally, the type of ailerons that will be used is selected and the size determined according to the chord.

The fuselage length is now calculated using the 10" chord. The nose will be 10" - 15" and the tail will be 20" - 24". Taking the median dimension of these, the fuselage length will be 44 1/2" (12.5" nose + 10" chord + 22" tail). The engine thrust is usually set for 0 - 3 down and 0 - 3 to the right. The landing gear is selected as a matter of preference. A conventional landing gear is set even with the leading edge of the wing. The main gear of a tricycle landing gear is placed 1 1/2" behind the center of gravity. The width of either main gear is 1/4 of the wingspan.

The stabilizer area will be 20% - 22% of the wing area. The area for the 600 sq. in. wing would be 126 sq. in. nominal. The aspect ratio for the stabilizer is 3:1. Using a stabilizer chord of 6 1/2", the length of the stabilizer would be 19 1/2" and the area would be 127 sq. in. The elevator is 20%; of the stabilizer area or 25 sq. in.

The fin is 1/3 of the stabilizer area and the rudder is 1/3 - 1/2 of the total fin area. For the current example, the total area of the fin would be 42 sq. in. and the rudder would be 21 sq. in.

The type of structure that is designed will depend on the use for which the model is intended and the personal preference of the builder. The slab sided fuselages are easier to build than the truss work structures but are also heavier and stronger in most cases. Foam wings are easier to build than built up wings but are heavier and more accurate. A little knowledge of structure goes a long way in the design of a model. In many cases, a modeler will design using the structural configuration of another model and simply change the appearance or the size of the model.
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Old Jan 17, 2013, 06:53 PM
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Everett, Washington
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Same here,,.. Just an old version of RealFlight
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Old Jan 17, 2013, 08:28 PM
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haiduk's Avatar
Marysville, WA
Joined Oct 2008
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Quote:
Originally Posted by Freddie B View Post
...
I promised to try and upload these documents on R/C design paremters. They work great. Do not let the high wing aircraft drawing fool you, the paremters work with mid and low wing aircraft also. I did not create these files but I do reference them often. Believe me, they work well.
...
Fred, Thank you for that document. It will help.

Quote:
Originally Posted by No Step View Post
Same here,,.. Just an old version of RealFlight
No worries there, you can hold the camera for the maiden flight videos! LoL

Oh yeah, as a side note, I've been talking with folks at the Y in Marysville about using the gym for indoor flying once or twice a month. Haven't got permission yet, but I am making progress there. Chances are very good we will be able to fly there soon.
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Old Jan 17, 2013, 10:10 PM
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smokey point, wash.
Joined Dec 2003
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I have done indoor rubber power there before....before electrons were invented, I think....
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Old Jan 18, 2013, 05:51 PM
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haiduk's Avatar
Marysville, WA
Joined Oct 2008
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I finished with the geometry of the initial 3D RealFlight model. Next step is to set up the texture map, the pivots/hinges, and build an object heirarchy tree that RealFlight can use.

Posting this link for reference:
Knife Edge Aircraft Tutorial
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