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Old Nov 11, 2014, 07:23 AM
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Alien Aircraft Corp Arrowmaster Biplane

I have been looking for a small gas biplane, and stumbled on the Arrowmaster kit from Alien Aircraft Corp.

I was looking for:

1. a sport biplane
2. wingspan about 50 inches
3. full up weight about 8 pounds, so that a new 15 cc gas engine (such as the OS GT15) would be a good fit

I will be keeping some notes here, on this kit, and how the build went.
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Old Nov 11, 2014, 07:31 AM
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Tucson
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Here is where you can take a look at the Arrowmaster: https://www.alienaircraft.com

This biplane is a Tom Herr design, and version 2 came out in June of 2014.
There is a PDF format manual (47 MB) that you can download, to get an idea of how the plane is designed and built, to see if you are interested in this airframe. The manual is clean, crisp and well done, with a complete listing of parts and wood that you will get in the kit. And the manual steps through assembly with a lot of color pictures. I like it when a manufacturing company can handle modern technical writing and drawings.

The kit is about $200, with $22 shipping to get it to my carport. Expect a plain brown cardboard box, well packed, with a solid block of building supplies that will go into the plane. This is a kit with heft!
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Old Nov 11, 2014, 07:43 AM
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The kit includes 3 full-sized sheets of plans. The 3 sheets are sized to fit on a building board (such as a door core from Home Depot). Drawings are clear, clean, and CAD CAM fresh. There was no damage in shipping. A big block of the heavier plywood sheets was shrink wrapped.

From the fresh smell of the balsa, I almost wonder if Alien is running a just-in-time manufacturing process.

Basic stats for the biplane are:
1. wing area: 995.6 square inches
2. 55 inch wingspan
3. about 48 inch fuselage length (will not fit across the back seat of most cars)
4. 7 pounds estimated full up weight (target weight for a .46 size cruiser plane, but up-motored to a .70 size engine for aerobatics)
5. about 17 ounces per square foot for a wing loading. (this and the slim airfoils point to a penetrating, gliding airframe)

Sample power plant on the plans is an OS .65 AX. The cowling is a ply and sheeted built up design that could be made to fit any engine of this approximate size. I am thinking more of a 15cc gas engine, such as an OS GT15 ($345) or RCGF 15cc ($150). You could probably make a 4-stroke nitro 1.20 fit, or A Saito FG14 4-stroke gas engine (Sunday cruiser power only, $400 on eBay). A 50x55mm 500 kv 6-cell 100A electric system would give you 10 pounds of thrust (aerobatic wuuup version). If you're going electric, think about modifying the front of the fuselage stress box (maybe moving the servo tray way into the nose, and making a battery box above the lower wing and where the gas tank is shown on the plans.

The fitness of this biplane airframe for this class of engine, is exactly why the Arrowmaster caught my eye. This biplane is an inspirational gateway drug into bigger scratch builds (such as a Pitts S1 60 inch biplane, with a Saito 33cc gas radial engine).
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Old Nov 13, 2014, 09:39 AM
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First 3 days of building

Here are some expressive photos from the first 3 days of building the Arrowmaster.

After just 3 days of work, it is shoutingly obvious why quality kits can produce a 7 lb plane that is much stronger than any ARF you are going to find for the same price. All the money that Alien would have had to plough into labor to build the ARF, can be put into higher quality and stronger building supplies.

Covering plans with a roll of Walmart parchment paper (for baking cookies on, $4 for 35 square feet) works well. Take care opening the box.

The design is a core stress box of plywood, with reinforced areas for wing seating and main gear. The outer shape of the airframe will be created with little formers and balsa lathing and blocks hewn to the final shape.
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Old Nov 13, 2014, 09:53 AM
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I built the fuselage, laid out over tracing paper (Walmart) taped to a 1" rosewood desk top that is jointed. I did not build over the plans, as the laser cut fuselage parts clip together and self-align (unlike our national budget). Most fuselage pieces are 1/16" plywood, which comes in the kit a little bit rough, so that glue will pounce and grab.

Tail feathers are 1/16" sheet balsa sandwiched over 1/16" sheet balsa that is cut to look like tail ribs and outlines of the shape.

As a biplane with 2 x 55" of wing, note that the tail area is substantial. The ratios call out to the attentively listening ear that this airframe is going to carve at speed, contrasted to the ratios of a Pitts S1 (that will tumble much easier).

In the final photo, we see the framed fuselage as Leonardo's man, filling out the center of the Alien plan for the whole, showing isobars of photon levels that the Sony Bloggie slices in the crappy morning back lighting.
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Old Nov 13, 2014, 10:17 AM
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A note on building materials...

I use Alene's ("Premium Quality Original") Tacky Glue (Walmat, 16 oz), which is a thick aliphatic resin that is outrageously cheap. I run a thick bead of this stuff anywhere a bead needs to be, running the nozzle opening in the direction that the nozzle is moving, to force glue into the joint and sculpt the bead.

Although using aliphatic is not attractive to some people, it resinates with a lot of died-in-the-wool builders.

I use Elmer's ("Washable No Run" School Glue (Walmart, aliphatic resin) in the small 4 oz bottle, because this little bottle can shoot glue where the 16 oz Alene's bottle will not reach.

High stress parts will get 6 or 30 minute 2-part epoxy.

I use thick CA as a tacker, or a medium strength glue between aliphatic resin and epoxy.

Weigh down the aliphatic resin joints, as the water in the glue will tend to warp the wood that it sinks into. Alene's pretty much sets up after 3 hours, but needs a day to cure. Put it on heavily, as most of the water volume will completely disappear in drying, leaving things looking more like a CA joint.
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Old Nov 20, 2014, 07:48 AM
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Lower Wing, Day 2-3

This is the 2nd week of building.
I built the lower wing first. It has no sweep back, and has 3 shapes of ribs. Only the lower wing has ailerons.

The first side took a while to work through, But once you have built one half, you know what to expect with the other half, and it goes much faster.

The final pic is the fuselage and the lower wing (unjoined), after 3 days total of building.

After seeing the size of the lower wing, I wonder if I should have chosen an OS GT22 for those 13.5 pounds of thrust ($390 + shipping from bigskyhobbies). Pulling 110 inches of wing through the air is going to produce some resistance. If I like the way the plane flies, I might want to eat Ramen noodles for 6 months to get a Saito FG-21 4-stroke ($504 horizon hobby).
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Old Nov 20, 2014, 08:54 AM
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On Covering

I plan to cover the wings and ailerons with dacron, then seal and paint them.

Why dacron?

1. with about 6.85 square feet of wing, wing loading will be about 8lbs / 6.85 = ~19 ounces per square foot, so a little more weight is not a problem
2. lightweight aircraft dacron comes in 60 inch rolls and is about 17 cents a square foot (aircraftspruce)
3. bursting strength of dacron is higher than plastic covering
4. covering with cloth allows me to choose custom color schemes.

Sealing before painting:
I am trying artist's gesso (michaels art store, 64 oz for $20). A fine bristled brush with decent strength can be used to bang on the gesso, which is a thick, chalky paste. This fills the wood pores, and is a chemically stable base for all sorts of paints. A light sanding when dry will leave the wood ready for paint.

After the wings are built I will do an initial CG check with the engine and tank in. If the tail end needs weight, I can sheet the turtleneck, and put the elevator servo near the tail.

I'm new to spray painting, so this will be an experiment. I painted the bare balsa wings with water cut Polycritic wood floor finish. This seals and hardens the wood, and is water based and non-toxic. A light sanding after drying, and the wings are ready for the dacron to be glued on.

I will use thinned aliphatic to glue the cloth on the edges of the surface. After the glue dries, trim the extra cloth off, and snap the dacron tight with a blow drier.

For a color scheme, I am looking at a core white plane with dark red accents. Using a cloth covering opens up the color combinations. Dark red accent could be: (painting-crafts acrylic, $1.19 per 2 ounces)
berry red
antique mauve
antique rose
autumn red
brilliant red
burgundy wine
country red
crimson tide
naphthol red
persimmon
tomato red

or even a crystal clear see-through gloss:
turquoise
white
black
yellow
orange
blue
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Last edited by wuest3141; Nov 20, 2014 at 11:15 AM. Reason: Alien abduction
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