Herr ½A Cub
Hobby Hangar 1/2A Super Cub
A friend from Maine once told me the story of a man from New York that was driving up in Maine. He came to an intersection with a signpost that had two signs that said Portland, but pointed in different directions. So he asked a local fellow walking by, "Does it matter which road I take to Portland?"
The local fellow replied, "Not to me it doesnt."
Well, it seems that there is more than one way to build a 1/2A Cub, too. Among the offerings are a J3 from Herr Engineering and a Super Cub from Hobby Hangar. I have built both, and Id like to report on the experience.
Herr ½ A Cub
Recent ads have announced the arrival of a series of laser-cut 1/2A planes from Herr Engineering. Among these are a Piper Cub, a Texan, a Cherokee, a trainer, and an amphibious plane, the Aqua Star. Several people have written in to the E-flight list about converting some of these for electric, so I knew it had been done before. I had been wanting to build a Cub for a while (actually, since I saw someone fly an Electra Cub on skis three New Years Day E-flys ago.) So, the Herr Cub was the one I chose. I even e-mailed Tom Herr to let him know that a lot of us were converting the 1/2As for electric, and later found out that future kits will be supplied with motor mounts and instructions for e-conversion.
The kit arrives in a bright yellow box with a photo of the model. Included are the laser cut parts of both ply and balsa, a plastic cowl and plastic sheeting for the windows. The nicely complete hardware package includes the control horns, pre-bent wire gear, gear straps, screws, and wire pushrods. The plans come in two sheets: one for the fuse and another for the wing and stabilizer. The instructions include diagrams of all of the laser-cut sheets, to aid in identification of the parts. The instructions are not photo-illustrated. A set of peel-and-stick decals includes the lightning-bolt stripe for the sides.
The wing starts with ¼" square upper and lower balsa spars. The laser-cut ribs practically fall out of their sheets, and the wing goes together nicely. The laser cutting is a thing of beauty. Shear web-like pieces are laser cut as well, and the wing tips are D-shaped pieces of lite-ply. There are four dihedral braces, uppers and lowers for each end of the flat center section. These are also laser-cut, and the process of building the dihedral is easy to do accurately. The wing is held in place by two dowels up front, and two nylon bolts in the rear. The leading edge is made from ¼" square stock, and must be shaped by hand to final profile (not exactly my favorite operation in the building of a kit.)
The stab and rudder are sheets of 1/8" balsa. I was tempted to drill some lightening holes, but decided against it, figuring the weight saving would be minimal.
The sides of the fuselage are sheet balsa, with each side consisting of three main pieces, which are then reinforced by lite-ply doublers. The formers are balsa and light ply. Constructing the fuselage is straightforward, and during the construction it is necessary to bend the sides together at the front, to accommodate the cowl. If I had it to do over, I would not glue the front third of the bottom doublers until bringing the sides together; this would enable the glue joint between the fuse side and doubler to assist in holding the front of the fuse together, and might help avoid the small cracking sound I heard as I brought the sides together to meet the firewall.
One problem I had to solve was how to mount the motor/gearbox assembly. In the end I used a piece of .032" aluminum sheet, available from the local hardware store, to make a mounting plate. The aluminum was thin enough to go in between the motor and the gearbox. I used a file to flatten the back surface of the gearbox, to make it a tight fit. I bored a hole in the firewall to allow the motor to pass through, and mounted the aluminum plate to the firewall with small screws and T-nuts.
The area at the top of the fuselage (at the front of the wing saddle) looked as though it could use a bit of strengthening, not so much as due to design weakness as to my uncertainly of my flying skills (I know, "Build to fly, not to crash," but Im not past the possibility of a hard landing or two.) Therefore I applied strips of carbon laminate at the front wing plate and along the wing saddle.
For mounting the battery, I glued a piece of EPP foam in the floor of the fuse and used Velcro on the foam to hold the 7-cell, 500mAh pack.
The fuselage and wing were then covered with Cub Yellow Ultracote (which was labeled "Oracover" on the backing, which I had heard was the case.) I beveled the edges of the stab and fin, and utilized my favorite hinge material: 3M Scotch ¾" Extra Strength Crystal Clear tape. Its easy, strong, removable, and makes an airtight joint. The all-up weight was 1 pound, 9.7 ounces.
The first flight was left to the infinitely greater flying skills of Steve Kranish. I tossed the plane, which climbed very slowly, struggling to gain altitude. A couple of turns around the field convinced us that the plane was a bit under powered with the 7-cell pack, and that perhaps a better prop than the standard MA 8X4 could be found. A later flight was undertaken using an 8-cell pack and the Aeronaut 8.5 X 5 electric series prop from Hobby Lobby (cat. #HLAN2824), and the overall performance was much better.
The Herr 1/2A Cub against a beautiful blue sky (apologies to the scale purists among you, but the dummy engine and struts were deemed non-essential for flight.)
Once I had finished the Herr Cub, I had a problem. The plans had called for two rolls of covering material, but I hadnt touched the second one. Now, when I had ordered the Herr Cub, I had also looked at 1/2A Cubs from Hobby Hangar and House of Balsa. With the extra roll of Cub Yellow Ultracote, there was only one thing to do: build another Cub. The Hobby Hangar kit is also listed as laser cut, so I decided to order one.
Hobby Hangar Cub
One of the other Cubs I had initially considered was the Hobby Hangar Super Cub. It is also a laser-cut kit, and just the right size for electric conversion. I decided I would build it and use the same drivetrain I had used for the Herr Cub. There is a superb review of the Hobby Hangar Cub by Ward Shelley on the E-zone (http://cgi.ezonemag.com/articles/1999/sep/cub/cubrev.htm), so Ill try not to duplicate the information found there.
The Hobby Hangar Cub comes with laser cut parts of balsa and plywood, and one of the first differences I noted was that Hobby Hangar labels the parts on the sheets, using a lighter setting of laser burn so as not to go through the wood. It is therefore easier to identify each part on the sheets. Also, unlike the Herr model, the Hobby Hangar includes a mount for a Speed 400 motor. However, I did not utilize this mount, since I was setting up the model for a gear drive. The cowl is not a single piece, but must be assembled from two vacuum-formed halves. The windows are vacuum-formed as well, rather than being simple plastic sheet. There is a complete package of hardware included as well. The plans are a single sheet, printed on both sides, and the instructions are photo-illustrated, but a bit less explicit than for the Herr plane, as Ill explain later.
Notes on Construction
Overall, the construction is very simple, and the model goes together quickly. Everything lines up beautifully in this kit, and the accuracy makes building a pleasure. The laser cutting is a bit finer than in the Herr kit, but the interruptions in the cuts were a bit larger, requiring more cutting by hand. The labeling of the parts helped immensely. Building the wing couldnt have been easier. The upper and lower spars fit into the ribs egg-crate style, and it is virtually impossible to build the wing anything but straight. Unlike the Herr Cub, this one uses ailerons. The wing has no dihedral, so it can be built in its entirety on a flat surface.
The instructors seem to be geared towards the more experienced builder. For example, gear installation is not spelled out quite exactly, and had I not built other planes with staggered holes for gear legs, I might have had a difficult time deciphering the procedure from the instructions. I should also mention that the gear leaves room for only very narrow wheels, and I had to use Lectra Lite wheels to accommodate the short axles. I used an aluminum plate to mount the ModelairTech gearbox, much like the arrangement I used for the Herr Cub. Instead of tail wheels I used Great Planes nylon wingtip skids, to save weight and because I fly mostly from grass, which would tend to catch a small tailwheel anyway. The total weight, including 7-cell pack, was 1lb, 7.7 oz.
Again, I chose to let a more experienced flyer take the plane up for its first flights. Jim Sarrette, of the New Hampshire Flying Misfits (Ive seen him roll my LowWatt, honest!) was kind enough to assist. On seven cells and the Aeronaut prop, the Hobby Hangar Cub climbed nicely, and flew gently (this time I actually took over the controls for a while before switching back to the camera), and made a beautiful landing.
Both planes were fun to build, and while the Herr had more explicit instructions (better for the less-experienced builder), the Hobby Hangar had the advantage of parts labeled on the sheets, and easier alignment of parts during assembly. The Herr is simpler, using rudder and elevator only; again, a positive for newer flyers.
So, in the end, does it matter which one you build? Not to me it doesnt.
Robert Buonfiglio <krazybob(at)tiac.net>
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