Swappable T-28 Trojan

Some time ago I received a request for a  T-28 Trojan from Jose Valentin. Unfortunately due to  a medical emergency it has taken quite some time to complete. As with most of my designs it was quite a challenge, and a learning experience. I've never designed by request before so after getting as much information from Jose  about what he wanted I began the initial layout. We had decided on a wing span of 44” and trying to keep as close to scale as I could the fuselage came out to 33.5”  and weight somewhere around 2.5 Lbs. It takes 5 sheets of Adams foam board to buld, and I'm using my Turnigy D2836/11 750 Kv for the test model  swinging a 11 / 5.5 prop. I recommend using a motor in about this range that is rated at about 280 Watts at least. I'm going by the recommendation of 90 Watts per pound. With the model now complete and the first copy safely in Jose's hands. I'm ready to bring this design to you.

Let's take a look at the build!

Due to the fact that the Trojan has a radial cowl and placement of the nose gear and actuating servo. I chose to modify the power pod to mount the battery pack within it. Since I chose to do this. I provided a secure mounting box for either a 2200 MaH or a 1300 MaH battery.

Shown is the power pod for the 2200 MaH battery

The fuselage is designed similar to the FW-190 using bulkheads and stringers secured to the box frame to support the skin.

I've also provided an air intake for ECS and battery cooling. Notice the cut out just aft of F-1

 F-2A and the intake completed and ready for mounting.

 F-2A and the intake is mounted. The flat plate just aft of F-2A is the canopy mounting plate.

At the suggestion of Jose I used the Dynam T28 Canopy w/ Cowl Insert Catalog # T28-05 from Grayson Hobby. The entire canopy section is removable and held on with magnets for easy access to the rudder and elevator servos.

Test fitting the canopy.

The dash is simply a poster board frame that is glued in place over the hole you see at the front of the cockpit.

Fits quite nicely!

The nose gear is also the same gear bearing used for the “Ruptured Duck” The Du-Bro 1/2A steerable nose gear catalog # 234

Notice the servo is mounted slightly below the surface of the fuselage frame.

This is necessary to allow the power pod and battery box room to pass through the frame.

The tail section is standard to most designs using tab and slot to maintain alignment.

Notice the control rods are supported by coffee straws at F-5 and F-6

The wing is also the standard design using 1/8” plywood gear mounts and also have the option for the use of flaps.

 As usual, I provide the Dihedral support guide in the plans.

Notice the dihedral brace is 1/8” plywood also.

This is becoming the norm in my designs.

The flap being readied for insertion.

Notice the cutout next to the main gear slot.

The designs provide for a 9G servo to be used for flap actuation,

but you can also modify it for sub micros.

 Flap servo ready for insertion.

The wing is then inserted into the fuselage and centered like most designs. Gluing only the bottom of the wing to the frame and then cutting it free from the fuselage

Gluing the wing in after centering.

Notice F-4C  is in place , but not glued at this point.

It must be removed to cut the wing free. The same is true for F-3C

The next step is to apply the skin. The cowling is done in two halves. The paper is removed from the inner surface and the part is curled over a piece of 1” PVC pipe. The exhaust port is also created by cutting three sides of the port and creasing the forth. Pushing the port inwards and supporting it with a piece of paper on the inside.

 Removing the paper from the cowl half.

Notice the slot and the cut out for the bottom of the nose gear servo.

All the sheeting is slotted to fit the tabs at the bottom of the fuselage frame to aid with alignment.

 Curling the cowl half.

It takes the form pretty well.

 The exhaust port is then cut and pressed inward.

 A paper tab is then glued in place to support it.

 It works quite well.

Aligning the slot and the gear door at the front with the tab on the gear mounting plate. I first glued along the bottom of the fuselage and worked my way up.

Placing the tab on the fuselage into the slot in the sheet ensures alignment.

Once the cowling is glued all the way up to the intake side. You can then align the top surface of the side plate with the canopy plate back to F-5. Before applying the other side. Run a BBQ sewer through the holes in the fuselage frame for the front wing hold down rod, and punch it through the skin. Do the same after applying the other side. This ensures proper alignment of the holes.

Cowling applied and ready for trimming.

Trimming the excess skin from the nose.

Note: The nose ring will be glued to this surface so sand smooth after trimming.

The tail skin is done in much the same manor. The tabs and slots have proven to be great for helping with alignment. There are even slots in the bottom of the horizontal stabilizer to help.

The tail sheet is one piece and I was surprised how well it worked.

The sheeting being removed. Notice the triangular section in the center.

The paper remains in this section.

 Curling the sheet as in the earlier step.

The end of the tail requires a sharp crease. This is done with a steel rule.

 This is the result.

Align and glue the sheet at the bottom as shown using the tabs for alignment.

Inserting the push rods before closing it up.

Control horns are connected.

Notice the bend just aft of where the sheeting will end.

 Gluing the left side first. Notice the tab on the right side.

This is glued down over the top edge of the left side, closing the surface.

As with the cowling.

Make the hole for the rear wing hold down rod before gluing the other side of the sheet.

The tail sheeting after it has been closed up.

Note: Trim the paper overhang at the rear of the canopy section.

Main gear is then bent to shape and glued in place similar to the FT P-51 gear.

Note the center of the wing also has tabs for the bilge sheeting.

 Removing the paper from the bilge sheeting to be curled.

 The sheeting in place.

 The wing saddle requires a little sanding for proper alignment of the wings at this point.

 The nose ring is cut from 1” Pink Foamular.

Notice the notch cut in the top for the intake.

 I found a pilot bust from an old canopy set and cut it down to use.

Fit pretty good.

Looks even better painted.

The nose ring has been mounted and puttied and sanded.

Decals have been printed out and ready to apply.

 Ready for a test flight.

This is my son Who is in the Navy Serving on the USS Abraham Lincoln. He just got promoted to Petty Officer 3rd Class. Seams only fitting that he be in this pic.

He just can't separate work from pleasure! LOL

So far this has been a really satisfying build. The initial glide test went extremely well. I used the first build to accomplish this. Needless to say I was pleasantly surprised! I wasn't sure if it would even fly strait because I didn't pay that much attention to how true the flight surfaces were. I was just making sure of the parts fit. I had my son to help me, and he paced off about 30 feet and I gave it a good toss. With the CG set at 30% of MAC, It flew strait and level and only lost about a foot in altitude by the time it reached him. I'm hoping for some decent weather this weekend so I can get a test flight in. I just loaded it and checked the CG and with the 2200 on board it was a little nose heavy, but with the 1300 it was right on. the plans are now posted to my web page and ready for download! Use the link below to get yours now!  I am also starting the build module on my Facebook page so yo can have a visual reference along with the instruction packet I provide.  Thank you to Jose Valentin for the inspiration for this build and I hope you enjoy it as much as I have.

Visit my site at:   Flyin Foam RC

Visit my FB page at: Flyin Foam RC on Facebook 

Update: 01-10-2015

 Finaly got some descent weather to fly today and my son had the day off, so we headed to the park I was hoping to get some good flight time in. She preforms really well, and I'm sure you will all enjoy building and flying the Trojan as much as I have. 

Enjoy

Randy Floyds maiden of his Trojan Was a bit windy but he couldn't wait any longer!

Nice work Randy!