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Help me please

kilroy07

Legendary member
#21
For balance it in relation to the wing, just looking at your design I would put it somewhere between the front of the servo and the servo horn (white part.)
A little nose heavy is better than tail, and increasing the elevator surface area as @JTarmstr suggested would help control while you find where it flies best for you.
Watch this;
 
#26
You could mashup a Mini Scout. That could help to see where they placed the servos in it. I know it is accepting of moving the wing up higher or down lower. You could change the wing tip (square them off even with the trailing edge position) and trailing edges (remove the scallops.) You could change the vertical and horizontal stabilizers (as long as you didn’t make the smaller or too much bigger.)
 

Vimana89

Legendary member
#27
Should a trainer have ailerons, or is that too complicated for a beginner, cause I'm still kinda learning as I go along
A trainer could have ailerons and be ok if it were a nice fine tuned kit trainer or retail plane. Ailerons, and even more so elevons, are not good for most beginner planes or definitely not a first scratch build or home design. Use basically the same design you have in that picture, with a larger tail plane as others have recommended. Instead of upswept wingtips give the entire wings a bit of dihedral, or maybe double dihedral. Eliminate the ailerons and use only a rudder and elevator for control surfaces. Get the CG about 1/3 of the way into your wing going back from the leading edge. Make sure with a tractor prop that's it's mounted and spinning properly and that you have a slight down and right thrust angle. That should fly👍
 
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#28
Ok so no ailerons, also i have my battery with tape around it then hot glued to a oeive if foam board that slides into a slot is there a better way to secure it
 

Vimana89

Legendary member
#29
Ok so no ailerons, also i have my battery with tape around it then hot glued to a oeive if foam board that slides into a slot is there a better way to secure it
A lot of people including myself use Velcro. One side on your battery one down in your battery compartment or electronics bay or wherever it goes on your build.
 

Vimana89

Legendary member
#30
With your RET build(rudder, elevator, throttle), make sure your wings have some dihedral but no too much. For best control, put your throttle on the left stick and your rudder on your right stick horizontal axis that would normally be your ailerons, and have elevator on right stick vertical axis. That way only throttle is on the left and everything you need to control the direction of your plane is on the right.
 

Hai-Lee

Old and Bold RC PILOT
#31
It is difficult to assist in the design of a RC model aircraft without effectively designing it for them/you.
My impression upon looking at your design is that the first rule of plane design was broken!
WING LOADING rules! Your design has big and relatively heavy wheels and a similarly heavy motor with a large area in the nose of the fuselage which I assume is designed to locate a rather large and heavy battery, when combined with small area wings the combination becomes flightless!

The wing design is definitely not one for high lift and the tail control surfaces are minuscule for the estimated weight of the plane. The Ailerons are inboard where their effectiveness is lessened due to their proximity to the planes Centre of Gravity.

Finally any aircraft design is to lift a set maximum load and carry the load a set distance. The speed of the travel should be considered as part of the design. Many here can provide advice and even ideas to help you in your task but the information you have supplied is really scant.

Have fun!
 

Vimana89

Legendary member
#32
Wing loading if definitely important.I didn't look close enough to see the size of your motor at first until @Hai-Lee mentioned it.I like the look of the first design you posted with the funky wide wing that tapers back. If you scaled that up to proper range of your motor and took away the ailerons and gave it the RET control scheme and modest dihedral, as well as larger tail plane, I think you would have a smooth flyer that looks really cool.
 

Merv

Legendary member
#33
Wing loading, CG and power to weight are critical. Here are some rules of thumb. Let us know if this is what you are looking for.

The nominal size of a conventional RC airplane should follow this rule for a good and stable flight.
(Flying wings and other designs do not follow this rule)

All the size ratio start with the wingspan. Determine your wingspan and start calculating the other sizes as follow.

The fuselage length should be 70% - 75% of the wing span:
• Example: If the wing is 36" long, then the fuselage should be 25" - 27" long.

The ratio of the wing span to wing root chord should be 5 or 6:
• Example: If the Wing span is 36"then the wing root chord should be 6"
Note: The wing root chord is that portion of the wing that attaches to the fuselage, measured from the leading
edge to the trailing edge of the wing.

The wing thickness should be 12% to 14% of the wing root chord:
• Example: If the wing root chord is 6" then the widest part of the wing should be 3/4" thick.
Note: Foam profile planes do not follow this rule of thumb but still fly.

The aileron surface area should be 10% - 12% of half of the wing surface:
• Example: If half a wing is 6" x 18" then the wing surface is 108 sq inches. The aileron shape should
equal 11 - 13 square inches of surface area.

The distance from the leading edge of the wing to the back of the prop should be 15% of the wingspan:
• Example: If the wingspan is 36" then the distance from the back of the prop to the leading edge of the
wing should be 5.4".

The leading edge of the wing to the stabilizer should be 3 times the wing root chord:
• Example: If the wing chord is 6" then leading edge of the wing to the stabilizer should be 18".

The horizontal stabilizer should be 25% of the wing area:
• Example: If the wing is a rectangle, 36"L x 6"W, it has a wing area of 216 sq inches. 25% of 216 = 54
sq inches. The shape of your horizontal stabilizer should equal 54 sq inches.

The elevator (attached to the horizontal stabilizer) should be 25% of the horizontal stabilizer surface
area:
• Example: If the Horizontal Stabilizer is 54 sq inches then the elevator surface area should equal
13.5 sq inches.

The vertical stabilizer should be 10% of the wing area:
• Example: If the wing is a rectangular 36" x 6" shape it has a surface area of 216 sq inches. 10% of 216
= 21.6 sq inches. The shape of your horizontal stabilizer should equal 21.6 sq inches of surface.

The rudder (attached to the vertical stabilizer) should be 25% of the vertical stabilizer surface area:
• Example: If the vertical stabilizer is 21.6 sq inches then the rudder surface area should equal 5.4 sq
inches.

The plane should balance at 25% - 33% of the wing root chord:
• Example: If the wing root chord is 6" from the leading edge to the trailing edge of the wing then the
Center of Gravity (COG) should be located 1.5" - 2" from the leading edge of the wing.
 
#34
Ok so the cg is roughly 1.5 inches behind the wing. I currently have a 2 cell 2000mah battery, 2 9 gram servos, a spectrum 4 channel receiver, and a 2000 kv motor and a 15 degree dihedral.it knid of looks like a red bull air racer so ya. Also no landing gear on this one.
435A66AF-ADCA-40BE-B09F-2757D16F8352.jpeg
17ADA93F-0402-4A74-AC9F-D1161BBC0B5D.jpeg
 

Merv

Legendary member
#35
Ok so the cg is roughly 1.5 inches behind the wing.
Thats about right, if your wing cord is 6 inches. Your CG should be about 1.5 inches behind the leading edge of the wing.

Just looking at the picture, your horizontal stabilizer (tail) is way too small. Your horizontal stabilizer area should be about 25% of total wing area.
 

Hai-Lee

Old and Bold RC PILOT
#36
May I ask for dimensions and weight!
It seems that you are rushing your build as the tail is obviously not well built and even out of alignment.
Additionally it appears that your wing construction is full FB underside which adds extra weight for very little benefit.
Whilst the Exhausts look nice they are not important in getting the bird to fly and actually just add unnecessary weight yet again!
The battery is quite large and heavy for your design and its already heavy construction.
15 degrees of Dihedral is somewhat excessive and potentially dangerous, (See Dutch Roll).
The CG measurement is fine but without knowing the wing cord dimension it is somewhat meaningless!

The first thing you should do is Slow Down and look at other designs in the same class and take clues from successful designs!

Have fun!
 

JTarmstr

Elite member
#37
Your getting there, the design is definitely improving and I think only a few changes would be necessary to get it to fly. First off as Hai-Lee mentioned. the tail surfaces are to small. As a comparison, here is a photo of my FT mini scout.
miniscout.jpg


Note how large the tail surfaces are compared to the wing. Here is the FT Mini scout article, in case you want some other photos for refference. also I recommend trying to build a bit lighter, and as I suggested earlier, recess the servos in the fuselage rather than the tail. Hope this helps!