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I am starting to design the rc airplane I will build for my senior project. I need help on wing loading and how wide I should make the wing (not wingspan) here's what I have so far:
1. at least a five foot wingspan
2. Twin engine (electric)
3. The estimated weight of the electronics is two kilograms.
4. The estimated weight of the fiberglass for the whole plane should be around four kilograms.
5. Plane will have twin rudders as well and most likely be a belly landed.

I also need help on props, engine power, and wing diameter.

many thanks
Zach

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Hi, If you still need info this is a good starting point,Built several RC planes and would suggest going the foam route.

Rules of thumb
This is a good place to start then you can experiment with changes to see what happens.
The ratio of the wing span to wing root chord should be 5 or 6:
• Example: If the wing root cord is 6" then the entire wing span should be 30" - 36" long.
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 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 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.
Note: This general rule is more for rectangle shaped wings, not necessarily for odd shaped or delta shaped
wings.

Are those the design requirements set by your tutor or are they your specification?  What is the timescale and budget for this project?  Also, what is your current experience of building model planes and is this a personal or a team project?
The reason I ask is that designing a plane of that size in fibreglass and getting it off the ground is going to be not at all an easy task, will be very time consuming and require high powered motors with the weights you specify, with a good chance of running out of time or money to do this.
If you can change the design parameters and your building experience is limited I would suggest  designing a smaller aircraft from one of the aeromodelling foams.  This has the advantage of being a lot lighter. a lot cheaper ,a lot faster t build and requiring a simpler power system to get it flying.  5 foot wingspan is not out of the question, but it's an order of magnitude easier to do it in foam than fibreglass.

Have a look at RC Groups, especially the 'foamies' section to see what people are doing with foam planes.

The measurement you looking for is the wing chord. (front to back) A large chord is generally high drag. the plane will be a slow flyer with high lift.

a narrow chord will be more efficient lower drag making the plane fly potentially faster .

SO - Large chord wings tend to be shorter (think piper cub) and narrow chord wings longer (think high performance glider).

You plane with a 5 foot wingspan should weigh in the order of 1 to 1.5 pounds without the electronics.

With the electronics and the heavy battery necessary to drive twin engines you looking at 2 to 3 pounds all up weight.

This will depent hugly on your building materials, style of plane and your building skills. Carbon fibre will weight less.  Poorly selected wood and fabric will weigh more.  Aluminium will weight a LOT more.

At a couple of pounds your not looking at a high performing plane - so you are looking at a wider chord.

The usual way to scratch build is to test in a wind tunnel and establish exactly what the lift to drag ratio is.

As a final point almost ANYTHING at model scales will fly if the engine puts out enough power.

Look at flight test and watch their build videos - they used a relativly cheap building method and explain how to go though the design.

I forgot to add that at 4 KG you way too heavy. Not impossible but your making things very hard.

Sounds like you need an aeronautical engineer.

Good luck!