300% FT Mini Corsair

Horseman3381

Well-known member
I have been flying RC since July of 2016 when I got my first plane, the FT Seaduck. I have friends that have been flying RC planes for years. When a coworker shared with me a link to the Flite Test Seaduck video I ordered it right away and told my friends to let me know what I all needed to get it in the air. After building/flying the Sea duck and reading/watching everything FT had put out I was hooked. I work in an engineering firm and have always like designing and building things. Combine that with my love of airplanes and it is a perfect fit.

I started designing and building planes since shortly after I started flying and have had several people at the local field tell me I need to post on the forums here. So, after enough nagging, I decided to give it a go.

This is my 300% FT Mini Corsair. I was inspired to create this plane when I was left with a motor from the FMS 2000mm Beaver after playing an impromptu game of RC lawn darts.

COR 01.jpg


Specifications:
  • Wingspan – 6’-0”
  • Motor – FMS 4258 550KV https://www.motionrc.com/products/fms-4258-550kv-brushless-motor
  • ESC – 70A
  • Prop – 15x9 2-blade
  • Battery – 6s, 4000mah (5 min flight w/ 50% battery remaining)
  • Aileron, Elevator & Rudder Servos – (4) Full size 12.8kg
  • Flap & real Wheel Servos – (5) 9g servos (I used HXT900)
  • 18 sheets of foamboard (a few less if you are better than me at puzzles)
I started by bringing the mini corsair plans into AutoCAD 2017 (program I have most experience with). After scaling them up 300% I made the following modifications:
  • Adjusting the plans for the foam being 1/3 the thickness
  • Updated the wing spar to a U-Box style
  • Updated the poster board parts to be made of foam (With exception of the canopy)
  • Added Provisions for non-retractable Landing Gear with a steerable tail wheel
  • Modified plans for the joints of the wings to fit cleaner at the bends (These areas did not scale up well)
  • Added provisions for the wings and fuselage to separate for transport.
  • Added flaps after hearing from several people that they make landing corsairs a lot easier.

The Main body structure is built using a double layer of foam along with the vertical and horizontal stabilizers. A few barbeque skewers were added to the stabilizers for additional strength.

For the cowling I decided to use 3 layers of foam for both structural integrity and to make assembly easier.

COR 02.jpg


The power pod is built using a spare motor mount for the FMS Beaver as a firewall (As it is designed for the motor I used). I made sure to keep the angle of the motor from the mini corsair to counter torque roll (which was needed).

The flaps are built in 4 sections (2 per side) and gave each section its own 9g servo.

COR 03.jpg


For the steerable tail wheel, I bought a setup from a local hobby shop with a 5/8” wheel. I rigged this up to be controlled off a 9g servo.

COR 04.jpg


The main landing gear I uses 3” wheels I bought from a local hobby shop. When anchoring them into the wing I bent a C shape into the wire to fit inside the wing. I then cut out a matching pattern into a rectangular piece of foam, and put one more piece on top of that to hold it into place.

COR 05.jpg


When scaling the plane up the control rods for the rudder and elevator ended up being too long to run unreinforced, so I converted them to a push/pull setup. In addition to this, on the elevator, I added popsicle sticks to the top and bottom at the center as the foam was starting to tear after the first few flights.

COR 06.jpg


To attach the wings to the fuselage I build an angle bracket by sandwiching a paint stick between foam on both the fuselage and the wings. I drilled 5 small holes that go through both brackets and placed 1/16” pieces of wire through them that friction fit to hold the wings on.

COR 07.jpg


COR 08.jpg


COR 09.jpg


The battery hatch it is the same relative scale as on the mini corsair. In order to get the CG correct I needed to put the 6s 4000 mah battery as far forward as I could.


COR 10.jpg


The ESC does not get as much airflow as it should, and gets rather hot if run at full throttle the entire flight. If I were to rebuild the plane I would make some alterations to locate it in the cowling, or provide a path for air to flow over it during flight.

To finish the plane I used Paper tape on all the ends and joints of the foam to seal things up and Rust-Oleum Spray Paint to make it look good passable from a distance. (I’m not great with finishes/painting)

Initially the plane tended to nose over on taxi and landing. By bending the gear wires forward, not using flaps and keeping the power on when landing the issue is minimized.

It’s not a pretty plane, but it turned out better than I had hoped. It looks like a Corsair, but it flies nothing like other RC corsairs I have flown. It flies more like a trainer, not very fast, but in the air it looks and performs to scale and is very easy to fly. It is one of my favorite planes because it makes flying so easy.

Overall I would say this would make an excellent second plane if you are looking to fly something bigger.

Here are some videos of it in action:


 

Userofmuchtape&glue

Posted a thousand or more times
Wow nice work mate! I have 2 parkzone corsairs so I imagine it would fly something like those. very light and smooth.

Abe
 

PsyBorg

Wake up! Time to fly!
Nice job mate.

Great work with the details and write up of what you had to change. I see people asking a lot of the questions on how to scale up you already addressed in that write up. Well done.
 

thenated0g

Drinker of coffee, Maker of things
Mentor
Very good build man. Liked the combination of skills/parts you put into it. The written part of your post was enjoyable to read as well. Have you considered doing an article? I think it would be a pretty easy copy paste for you. This has me inspired to try and do another large build. When i did my 200% guinea pig and FT-22 i really was worried about things breaking and made them both way heavier than needed. The flew, but was full throttle almost the entire time.

How did you reinforce the wing for positive and negative g's? IE stop it from folding in flight. I had aluminum tubes in my wings attached to thin plywood on the bottom of the airfoild. Strong, but heavy. I cant imagine how you reinforce that crazy shape on this thing.
 

Horseman3381

Well-known member
I had not thought about making the post an article, I guess I didn't realize there was a spot to submit them.

For the wing reinforcing, to handle the positive G's I added reinforced packing tape to the bottom of the wing at the bends. Positive G's act with the outer bends of the wing and the tape keeps the bottom of the wing from separating while the spar go into compression. For the center joint of the wing I added 2 extra pieces of foam to the bottom and a lot of hot glue which has held up so far.

COR Wing.jpg


The negative G reinforcement is not as robust. The wing U-spars have double foam vertical legs. One of the layers on each side has a joint at the bend, but the other layer is continuous through the bend. In addition there is also a 3rd foam piece that spans 6" each side of the bend. If I were planning on doing a lot of negative G flying I would recommend adding some paint sticks or plywood at the bends to reinforce it. Weight is not an issue with this plane, so some extra reinforcing would not be an issue.