The Hercules

Introduction:

The Hercules is an airplane that is meant to be not only a good trainer, but also a good airplane to build if you want to get into building wooden models.  Although it does not involve "traditional" build techniques that are encountered with building such models, I believe that it is a great place to start if you want something to learn some basic skills such as covering with MonoKote.

The problem with some airplanes is that if you don't build them just right, they don't fly very well.  So if you warp your wing or build the tail crooked, for instance (both of which are very easy to do on a wooden airframe), some airplanes will not be as forgiving as others.  However, the Hercules is an exception: It has many good flying characteristics, and even if you build something a little twisted or glue something a little off, you will still have an enjoyable flight experience.

Another thing that many people are intimidated by are the build materials.  With a foamie, you usually just need to buy x sheets of foam board or depron, and you're good to go.  But with a balsa model, you need various types of wood(balsa, basswood, plywood), with each type having several sheets of varying thicknesses (1/8", 3/32", 1/16", 1/32", etc.).  To the hobbyist who has had no prior building experience or maybe just a few foamies under his belt, this list will seem like a nightmare.  The Hercules, though, uses only two types of wood: 1/4 square sticks and a 3/32" balsa sheet.  These can all be obtained for a very cheap price from your local hardware store.

How I came up with this design:

The Hercules was inspired by two things: my desire to create a wooden model and by an old aiplane called the Handley Page H.P. 42, aka the "Heracles".  For those who don't know about it, it was one of the first safe passenger planes that took to the skies; it was introduced in 1930 and had a cruising speed of around 90 mph.  This slow speed combined with the safety of the aircraft dubbed it "Slow but Safe".  Here's a photo:

I liked the stubby landing gear and square-ish fuselage.  So I got rid of the top wing, straightened out the bottom one, simplified the tail assembly, and replaced four engines with one.  (Sounds like a lot of changes to count as "being inspired by", doesn't it?)

So a little over a year ago, I created the first prototype.  After a few changes, I ended up with this:

Now that I think about it, it looks a lot like the classic "Ugly Stick" as well as the Road Runner that Flite Test reviewed in 2013.

Specifications:

Wingspan: 36 inches
Wing area: 288 square inches
Fuselage length: 24 inches
Fuselage width: 2.5 inches
Weight: 12.8 oz. (358g)
Propeller:  8x3.8SF prop.  Recommended: APC 8x3.8 Slow Flyer Propeller
Motor: 120-200w.  Recommended: Suppo 2208/14 1450kv Brushless Motor (Park 370 equiv.)
ESC: 18-20 amp.  Recommended: Suppo 20A Brushless ESC
Servos: 3x 9 gram.  Recommended: Hextronik HXT900 9 gram servo
Battery: 3s 1000-1800mAh Lipo.  Recommended: Turnigy 1300mAh 3S 20C Lipo Pack
CG: Flip aircraft upside down and balance on central wing spar

Note: Power Packs B and C from Flite Test also work great on this airplane.

Construction:

As mentioned above, you only need a handful of materials to build the Hercules:

          -7x 36"-long 1/4" square poplar dowels;
          -2x 36"-long 4"-wide 3/32" Balsa sheets;
          -2"x2" plywood for firewall (3/32"-1/8" thickness);
          -2x plastic spoons;
          -wire for landing gear;
          -MonoKote covering film (other brands also work); if unavailable, use tape.

That's it!  You will also need a saw to cut the dowels, a #11 x-acto blade to cut the Balsa, and a covering iron if you decide to use iron-on film for covering.  (NOTE: A regular household iron will not work!  Your wife will kill you, and you will burn a hole in your plane!  Those things get way too hot; check the instructions that came with your particular covering material for the optimal temperature.)

In terms of adhesives, you can use pretty much anything.  For this build, I recommend medium CA or hot glue, as they both are convenient to use and dry quickly.

I usually use extreme packing tape or transparent MonoKote to hinge the control surfaces.

I highly recommend making a "kit" before you start assembly (cut out all the parts, gather tools, etc.).
Here's a list of all the parts that you have to make:

          -26x 2" dowels;
          -3x 3" dowels
          -8x 6" dowels;
          -4x 24" dowels;
          -3x 36" dowels;
          -4x 6"-long 2"-wide balsa sheeting (nose);
          -2x 16"-long 2"-wide balsa sheeting (ailerons);
          -Firewall (2"x2");
          -Tail Surfaces (see plans).

I have included a set of plans at the bottom of this article.  All you have to do is follow the directions. The build time on the framework (provided that you cut out all the parts in advance) is about 1.5 hours.  The covering is also quite easy to do; both the fuselage and the wing can be covered with a single sheet of MonoKote.

When installing the servos, you will have to make supports for their flanges.  On the fuselage, install a second stick behind the one to which you will be mounting your servos.  The distance between the two will be determined by the length of your servos (plus room for the wires that you will have to snake through when installing them).

After covering the fuselage, remove the covering from the area below the wing and from the area below the tail. Also clear out the spaces for your servos.

Here are a few photos that show some of the construction features:

Spoons cut to serve as ducts for cooling.

The same thing, just on the inside.

The whole system viewed from the top.  Note that the ESC is positioned just aft of the left hole for best cooling.

This is a photo from the back of the interior.  I suggest not covering the rear hole; that way, the air passes through the entire fuselage before exiting and has somewhere to go.  This photo also shows the servos and the fuselage's construction.

This is the front hatch for battery access.  The hold-down machanism uses two additional 2" poplar sticks at the front that are drilled out to hold Bar-B-Q skewers.  The back uses two sticks that friction-fit each other.

The landing gear is very similar to something you would find on a swappable.  The front is held on with a rubber band that goes around the landing gear hold down, shown on the plans.  The back is attached to a separate dowel with a zip-tie.  (The plates next to it are the remains of an unsuccesful attempt to install a hatch on the bottom.)

Flying:

In the air, the Hercules has a wide speed envelope and can perform moderately advanced aerobatics.  The glide ratio is also quite impressive.  The wing is strong and can withstand high G-loads.  One thing to note though: when installing the ailerons, be sure to give each one a litte bit of "up" deflection-- that is, make each one point a little upwards, as in the photo below.  This is to prevent them from acting as flaps and thus unnecessarily stressing the wing when doing high-speed snaps in the pitch axis.

Also, keep your control throws to a minimum.  The effectiveness of the large ailerons and powerful tail surfaces is easily underestimated; I would suggest no more than 1/4" (6mm) of throw in each direction on everything.

Conclusion:

Thanks for reading!  I sincerely hope that you will enjoy building and flying this design.  If you have any questions regarding the build, leave a comment below and I will try to help you out.  Also, I would appreciate any feedback about the write-up itself-- since this is my first build article, there might be some things that could be made clearer, so any advice is much appreciated.  Thanks again for reading!

Until next time,

--The One Who Never Crashes

P.S. The plans!!!