| Designing and Building an SSC Warbird from Scratch The KI61 Hein (Swallow) added February 18th, 2003 |
Many combat pilots are reluctant to attempt to build an figher from scratch. It's easier than you think. I will take you through
some of the thought processes and design rules you can use to easily build your favorite fighter from scratch using only a 3 View
drawing as a starting point. Having a three view is important. Search the internet to find one of the plane you want to build.
some of the thought processes and design rules you can use to easily build your favorite fighter from scratch using only a 3 View
drawing as a starting point. Having a three view is important. Search the internet to find one of the plane you want to build.
The three view shown at left was found by doing an internet search. It is a very clean
drawing of the fuselage profile and has formers shown on the drawing. These
formers will be used to create foam cutting templates.
Decisions you will need to make:
1. What size plane are you going to build?
2. Will you build more than one of the same plane
3. What is your target weight
4. How do you determine the CG
5. What airfoil will you use? Do you want dihedral and washout?
6. Where do the thrust, wing, and tail lines go?
To answer some of these questions lets say you are going to build and SSC
Warbird. Some of the design questions are answered by a quick review of the rules.
First you know you are limited to a .15 size engine. You also know you need to
weight 2-1/2 lbs or more.
drawing of the fuselage profile and has formers shown on the drawing. These
formers will be used to create foam cutting templates.
Decisions you will need to make:
1. What size plane are you going to build?
2. Will you build more than one of the same plane
3. What is your target weight
4. How do you determine the CG
5. What airfoil will you use? Do you want dihedral and washout?
6. Where do the thrust, wing, and tail lines go?
To answer some of these questions lets say you are going to build and SSC
Warbird. Some of the design questions are answered by a quick review of the rules.
First you know you are limited to a .15 size engine. You also know you need to
weight 2-1/2 lbs or more.
So lets start with some proven numbers. Experience has shown that SSC Warbirds need to have a wing loading between 11-12 ounces a square foot to fly well. How
do we determine the wing loading?. Well start with an assumption that our finished plane will weight 2-3/4 lbs which is 44 ounces. The simplest way to calculate the
wing size and loading is to use the wing calculator by clicking here.
Now that you have determined your wing size you can work out your fuselage size. By trial and error we have come up with the following numbers to use as a
benchmark for SSC Warbirds:
do we determine the wing loading?. Well start with an assumption that our finished plane will weight 2-3/4 lbs which is 44 ounces. The simplest way to calculate the
wing size and loading is to use the wing calculator by clicking here.
Now that you have determined your wing size you can work out your fuselage size. By trial and error we have come up with the following numbers to use as a
benchmark for SSC Warbirds:
| - Fuselage length from back of spinner backplate to center of rudder - 29 inches - Wing leading edge to back of spinner backplate - 7 inches - Height of fuselage at the highest point 5-3/4 to 6" maximum |
With some of the design parameters done we can start laying out our fighter. We will begin by drawing out the fuselage profile to create a template for cutting the
foam "blanks". It is easiest to use a digital caliper and a handheld calculator to do this step. It can also be done with a normal ruler. Print out your three view
drawing and measure onthe drawing from the back of the prop to the center of the rudder where the fuselage rear will end. Lets say this measures 4.5" on your print.
Since you want to make your fuse 29" you divide 4.5" into 29" for a sum of 6.44. This is the multiplication factor you will use to transfer dimensions from your three
view to your full size pattern. We will our calculator for transforming sizes.
Draw a centerline (which will also be your the thrustline) on the drawing. This line is normally already on the three view for you. It starts in the middle of the spinner
and goes through the rudder out the rear of the plane. Once you have drawn this line horizontally on the plan you need to make perpendicular "station lines" through
the fuselage. The station lines should be located at each end of the fuselage and at the profile change points. You will measure from the center line on the 3 view
print on each station line to the outside of the fusleage and multiply this measurement by your sizing factor.
Using your caliper or ruler and calculator transfer these dimensions to a carboard template . Your template will look like this:
foam "blanks". It is easiest to use a digital caliper and a handheld calculator to do this step. It can also be done with a normal ruler. Print out your three view
drawing and measure onthe drawing from the back of the prop to the center of the rudder where the fuselage rear will end. Lets say this measures 4.5" on your print.
Since you want to make your fuse 29" you divide 4.5" into 29" for a sum of 6.44. This is the multiplication factor you will use to transfer dimensions from your three
view to your full size pattern. We will our calculator for transforming sizes.
Draw a centerline (which will also be your the thrustline) on the drawing. This line is normally already on the three view for you. It starts in the middle of the spinner
and goes through the rudder out the rear of the plane. Once you have drawn this line horizontally on the plan you need to make perpendicular "station lines" through
the fuselage. The station lines should be located at each end of the fuselage and at the profile change points. You will measure from the center line on the 3 view
print on each station line to the outside of the fusleage and multiply this measurement by your sizing factor.
Using your caliper or ruler and calculator transfer these dimensions to a carboard template . Your template will look like this:
Here is the finished two part fuselage template with the wing saddle cut into it. Before we get it to this stage we have to do a couple of things. After transferring all
dimensions to station points on the template we connect the dots to form the profile shape of the fuse. The next step is cutting out the wing saddle area.
There are numerous airfoils that will work with this plane. We have used the Eppler 203. If you do not have an airfoil generation program we suggest you check out
PROFILI by clicking on it.
dimensions to station points on the template we connect the dots to form the profile shape of the fuse. The next step is cutting out the wing saddle area.
There are numerous airfoils that will work with this plane. We have used the Eppler 203. If you do not have an airfoil generation program we suggest you check out
PROFILI by clicking on it.
When you calculated your wing area you determined the root chord. Print our your airfoil root rib using Profili then use it as a template to cut the wing saddle. It is
important when printing out your root chord airfoil pattern that you use the centerline function on Profili. You will need this reference to set the proper wing incidence.
Use your horizontal thrust or data line on the template to position your wing root template. I measure the thickness of the root trailing edge till I get to the one quarter
inch thick point and cut it off bluntly there. I use 1/4" thick aileron stock and after I cut the patter to shape I trace it onto the template. Make sure the root chord template
centerline is exactly parallel to the line you have drawn on your template and that the Leading edge is 7 inches from the front of the template (this will make it balance
with an OS or Magnum). Draw your wing saddle on the template. Now you can cut out your template. Separate the template in two as shown in the photo above at the
high point of the fuselage. You are going to make your fuselage in four pieces: two front and two back.
important when printing out your root chord airfoil pattern that you use the centerline function on Profili. You will need this reference to set the proper wing incidence.
Use your horizontal thrust or data line on the template to position your wing root template. I measure the thickness of the root trailing edge till I get to the one quarter
inch thick point and cut it off bluntly there. I use 1/4" thick aileron stock and after I cut the patter to shape I trace it onto the template. Make sure the root chord template
centerline is exactly parallel to the line you have drawn on your template and that the Leading edge is 7 inches from the front of the template (this will make it balance
with an OS or Magnum). Draw your wing saddle on the template. Now you can cut out your template. Separate the template in two as shown in the photo above at the
high point of the fuselage. You are going to make your fuselage in four pieces: two front and two back.
Click on drawing to see enlarged view