One of the nice things about building a kit, is that you can make changes to the construction to suit your own tastes. Two areas that I changed on the Alien Aircraft ArrowMaster Bipe, were the mounting of the landing gear and the cabane struts. If you followed the instructions, these are epoxied into place during final assembly of the model. While there’s nothing wrong with this, I wanted to make them removable, in case they got damaged. Being that the cabanes and landing gear both slide into pockets, it was easy to add some plywood on the top and bottom of the mounting plates and add 6-32 blind nuts.
On the left is the landing gear mounting plate, to the right, is the top of the fuselage. I used scrap ply from the laser-cut sheets and added 6-32 blind nuts. The bolts will be installed from the bottom of the fuselage for the landing gear, and from the top for the cabane struts.
Here’s the gear plate as it will be installed in the bottom of the fuselage.
Here’s the fuselage top as it will be installed on the top of the fuselage.
This is the pocket formed for the landing gear from the layers of ply.
The landing gear is a 2-piece affair. I used 3, 6-32 bolts on each half to secure them. The same method is used for the cabane struts. Now is a good time to ensure the aluminum parts slide easily into their respective pockets.
Once the cabanes were fitted, I glued the top of the fuselage in place.
The top of the fuselage is made from 2 pieces to make a single piece that stretches from the nose all the way to the tail.
Another view of the cabanes. Note the slots in the top fo the fuselage, formers will be glued into them to give the fuselage its rounded top. The bottom of the fuselage uses the same technique.
As you can see, all of the parts are interlocking. The laser-cutting of the kit is extremely accurate and makes building the ArrowMaster a joy!
Here’s a look inside the top of the fuselage. The bulkhead with the 2 holes are for the bottom wing retaining dowels. Now that the basic fuselage is built, mounting the bottom wing is next!
Bottom Wing Setup
Setting up the bottom wing is a pretty simple affair. I did make one change though, instead of tapping the ply wing bolt mount, I epoxied a couple of plywood pads to the inside of the mount and used 1/4-20 blind nuts for the wing bolts.
The bottom wing is placed in the wing saddle and then centered, I used several rubber bands to tightly hold the wing in place.
I used a long straight edge ruler and made sure the wing was equal in distance from each wing tip to the rear of the fuselage. Mine measured out to 34-1/16″ on each side.
Now measure from side to side to center the wing.
I used a 3/16″ bit to drill the bolt holes. After the first hole was drilled, I used another 3/16″ bit as a locating pin the prevent the wing from moving as I drilled the second hole.
I made the one inch square pads from 3/16″ ply and drilled the holes for the 1/4-20 blind nuts.
Here’s the blind nuts for the wing bolts epoxied in place.
The holes for the wing hold down dowels are now drilled. I secured the wing with the wing bolts and some weight on the front to prevent it from moving. Use the holes in the bulkhead as a guide to drill the 1/4″ holes.
Now insert the dowels, if the dowels are tight in the holes, use a round file to open the holes as necessary.
Here’s the dowels in place, I’ll securely epoxy them to the wing after the wing is covered.
The way the nose of the ArrowMaster is designed, lends itself to many engine options. For my build, I decided to use a Saito FG-17 4-stroke gas engine. Being the engine is longer than the recommended OS 2-stroke 65, some changes were needed to accomodate the Saito.The distance from the firewall to the thrust washer on the ArrowMaster is 5 1/2″, and uses an engine box that’s built and installed on the firewall. The gas version of the Saito is rather long because the carb is installed on the rear of the engine, this pushes the engine further forward.
After taking a few measurements, I determind that I needed to make a plate 3/16″ thick to put the thrust washer of the engine in the proper location. I cut the tabs off of the engine box, and used the engine mount to make the center hole in the parts.
I used the face of the engine box as it has alignment marks on it making it easy to properly place the engine mount. The 3/16″ ply spacer is glued to the rear of the plate and I used the the engine box to locate the assembly in its correct location. I removed excess material and sanded it flush with the front of the engine plate.
The engine mount is fastened with 8-32 bolts and blind nuts. The firewall assembly is now ready to the glued into place on the fuselage.
I used some clamps and 30-minute epoxy the glue the firewall into place.
Another view of the firewall clamped in place.
As recommended in the instructions, I added triangle stock to reinforce the firewall joint. The tank floor and bottom of the fuselage will be installed after this area is fuelproofed with a thin coat of epoxy.
The location of the throttle arm presented an interesting problem on how to run the throttle pushrod. I decided that running the pushrod straight back was the best solution. I used a DuBro flexible cable for the pushrod.
I drilled a shallow-angle hole for the cable to enter into the radio compartment. I added a spacer to support the cable’s sheath and secured it with ZAP Goop.
The throttle cable run is friction-free and takes no effort to move it by hand. I can see that I have a couple of options on where to install the throttle servo. I’ll make that decision as I start to install the receiver and other equipment. With this step completed, the rest of the fuselage can now be built.
That’s it for this time, be sure to stay tuned as more updates are to follow.
To see the previous installment of this Build-Along project, click the link: http://www.modelairplanenews.com/blog/2014/08/08/workshop-build-along-alien-aircraft-arrowmaster-4-top-wing/