Building the HKM 1:2.5 ASW 28 – INDEX
by Rick Briggs
KIT PARTS
Received my 28 two weeks ago, photos attached. I was very happy to see the quality of this ship; the photos don’t do it justice, many thanks John! At HKM USA. http://www.hkm-models.com/
It was great that HKM was willing to make the model with my own graphics, I chose to go with a Swiss version, with my letter font and numbers.
The kit comes with all the bits you need to assemble with bags of goodies, less RC equipment and Cockpit detailing.
A 7 ch Competition Power Box system that comes with two 3300 nm batteries and a digital switch from Aircraft International. http://www.aircraftinternational.com/.
LANDING GEAR
Before I sound too nuts, just understand all the stuff I show you on this building log is meant to express ideas and not to make the building of your 28 an exact science, this is meant to aid and exchange ideas with all. I will assume that all of us by now know now how to build at this level. I will try to show all the details in photos. When in doubt, ask a question, your humble servant.
The Kit comes with a retract installed. You have to mount the servo.
In this case I used a Hitec 5945 digital servo. I also fabricated a brake system using a second 5945 digital.
I used some left over servo mounts from Hock, you could use any aluminum right angel extrusion that’s light weight from the hardware store, the same as in John’s photo. The linkage is a carbon aero shaft with 4 /40 all thread inside with 4/40 ball links at each end.
The brake system is made with a brake kit from Fema Modelltechnik that fits a 127 MM wheel. The rest is made from 1/8″ aluminum plate and 1/2″ round rod. After mounting the servo and linkage I used braided fishing wire to connect the bell crank to the brake arm. This is done so the retract can rotate up and down and still have a positive connection to the brake.
http://www.fema-modelltechnik.de/
One thing I would recommend, the aluminum collet on the main shaft that has a recessed 4mm alien screw that needs to be replaced with a 4mm external socket screw. Also make a flat spot on the shaft so the screw will seat and prevent it from rotating, this is done after you find the proper movement of the retract.
RUDDER AND ELEVATOR
Shots of elevator and rudder install.
Elevator
I used some flat aluminum plate and made a insert for the elevator control arm. Notice I have extended the clevis hole aft past the bottom of the arm.
Make a slot in the elevator to receive the arm, to the underside of the top surface. Then make a slot 90 degrees to each side of the first slot, inside the elevator, making a + shape. Fit the arm inside the slot, mark a line on the arm to show the amount you will be bonding, drill some holes in the part of the arm that will be bonded. This way you have a secure mounted arm. The push rod is a carbon tube with allthred inside, with nuts at each end to capture the rod. The rest is easy.
Rudder
I used 4mm aluminum fittings for the carbon rudder hinge and rudder control arm.
I cut off the top of the inserts to make clean looking fittings.
For the hinge, remove the flat section of the threaded control arm and cut a slot to receive a screwdriver, at the other end drill a hole to receive the hang rod.
Drill a hole in the bottom of the rudder in line with the rudders center line, for the insert. Install the insert with the hinge rod inside the insert, this will keep the rod straight, be careful don’t get CA on the rod or threads!.
Tape the rudder to center and mark the center of the control horn inline with the rudder fairings back edge. Install the insert by drilling an additional hole in the LE of the rudder to allow you to get epoxy to the inside of the rudder, and bond the insert.
Mounting the rudder servo is easy and in this case I used a left over aluminum servo mount with a plywood backer. Every one has there way of doing this. Just keep it clear of the retract arm.
One tip, I use masking tape on all surfaces when using epoxy, it keeps things tidy.
MOLDING COCKPIT SEAT PAN AND SEAT BACK (Part 1)
The following photos show the process of making plugs and molds for the seat pan and seat back. This process is much the same as the ASH 26 I did on the ISSA Tech Tips page only here I decided to use polyester resin instead of epoxy.
MOLDING COCKPIT SEAT PAN AND SEAT BACK (Part 2)
The following photos show the process of making plugs and molds for the seat pan and seat back. This process is much the same as the ASH 26 I did on the ISSA Tech Tips page only here I decided to use polyester resin instead of epoxy.
MAKING THE SIDE COMBINGS
Making the side combings is much the same as I did on the 26 except I am making the plugs removable so I can mold them.
Since this model is bigger it’s a little easier to work on and I wanted to keep the weight down so making molds for lighter parts made sense.
Later I will show the cockpit with the parts in place and primed.
COCKPIT DETAILING
Getting a little closer to getting the hard stuff done. Soon it will be on to mounting all the R/C gear and servos.
INSTRUMENT PANEL
I ordered my instruments from Axel’s Scale Pilots. I used 1.2.5 and 1.3 sizes. Using several photos of full size, I went with something close to the ASW 28. The Mini Micro switches are from Radio Shack. The texture is 3M rocker panel spray from an auto paint store.
COCKPIT LABELS
Time to add the labels, I purchased a set of ASW 28 Labels from Eastern Sailplanes (the ASW 28 & 29 are now a black background the earlier are white).
I then scanned them at 400 dpi into Corel Draw 11. I then printed them at 40% reduction onto a 8.5 X 11 acrylic permanent sticky back with a matte finish. This matte paper is called “Labelblank Scoreline”. You can Google it.
I then sealed the paper with Deft brand clear satin wood finish; it darkens the inkjet print and puts a nice clear seal to the paper. I then use a new exacto blade and cut out the labels placing them where the full size labels are placed.
This works for all ASW and ASH 3.5 scale and up. What is great is the label sheets come with everything, even the on off for switches and fuse labels for the instrument panel.
Working on R/C install and cloth panels.
R/C EQUIPMENT
I fashioned a switch platform and flat surface for the RX and Power Box System from light ply. I made holes in the standoffs for wires to pass through.
The aero tow release is a simple assembly with a Hitec 5645. I left access for balancing the C/G.
Batteries are mounted with Velcro, as is all the R/C gear.
CLOTH SIDE PANELS
The side panels are fashioned from poster board and a 1/4 fiber filler and a cloth of choice.
The layers of cloth, fiber filler, and cloth backing are all glued with 3M adhesive spray.
If you don’t have skills for sewing things, this might be the time to have female input. I bet you could get this done for a night out on the town, you know, dinner and stuff.
After gluing all the materials together, I then sewed the seam lines to match the full size cockpit panels. I used tape to guide the seam lines.
I did a test fit by taping the panels in place and then trimmed the sides of the seat tray to seat on the mounts.
I then made a map pocket and mounted it to the side panel. The pocket has a copper wire at the top edge so I can shape it.
WING SERVOS AND CANOPY LATCH
Just when you thought I was done.
The wing servos are pretty standard. I’m using Hitec 5945 dig. The servo frames are a new item. They are from Germany and Craig Greening is the US distributor at servoframes.com. These are for JR but you can modify them to fit Hitec. I really like these because you can easily remove the servo.
On the canopy frame, the latch and pull are made from a latch you can get at Hobby Lobby.
CANOPY FRAME
Getting a little closer to being done. The following is adding more detail to the canopy frame and instrument housing. I added height to the sides, a lip to the instrument sunscreen, and I flattened the front of the housing for the air intake flap.
The texture is done by using 3M Rocker Panel Spray.
The top cover in made by using a thick vinyl tape to outline the cover, then use body filler to blend the edges. Once you get the shapes, remove the vinyl tape and you get nice even edge to the cover. Spray on the panel spray then sand and prime the panel spray to get the desired finish. When you spray the texture, be sure to mask and protect the rest of the canopy frame, this stuff is hard to sand off. The rest is painting using flat black enamel and a white that matches the model.
Next I will install the canopy.
At this point I have installed all the servos and programmed the model. After a complete assembly I will set the C/G.
Plan to do the Maiden at the Spring Visalia aero tow.
My next and last post on the build will be finish shots of the 28.
CANOPY DETAILS
Here are some shots of the finished cockpit. The canopy is left off so you can see more detail.
FINISHED
All done!
FLYING SHOTS
Here are some photos of the maiden flight.
