Building
The RagWing SPECIAL bi-plane is a lightly powered ship which has been designed with the sensible intention of creating a moderately fast bird which can be used for cross-country work. Inexpensive to build, simple in its general design and structural details and only simple tools are necessary for fabrication. It has certain definite characteristics which will appeal to nostalgia builders who grew up constructing old balsa and tissue rubber band models. Perhaps the outstanding single characteristic of the RagWing Bipe is the way it handles in the air. Flown by many different pilots it proved to be easy to take off, simple to handle in the air and even easier to land. A Veteran ultralight pilot with better than 1400 hours agree that in spite of its moderate horsepower and general light weight, it behaves and is safe and easy to fly; that it will land itself, and that it has no apparent vices.
Even a beginner can pull this ship off the ground with a run of 150 feet or less.( By beginner I mean a student pilot and not any person with no training at all.) Once in the air, its extreme ease of handling, stability and responsiveness to controls make it an ideal ship for sport purposes. With a low landing speed of 32 to 35 mph, many of the difficulties presented by this operation are automatically eliminated. With a cockpit 24 inches wide and the ships low weight it is capable of lifting pilots with more weight than its own and has room for men standing tall at 6’6″. It also features a one man 30 minute wing fold which allows sharing a hangar or towing home. Almost all aircraft builders ask for a sequence of construction so I polled most RagWing builders to come up with the most recommended sequence which follows:
1. Ribs
2. Tail Feathers
3. Spars
4. Wing Assembly
5. Ailerons
6. Fuselage
7. Landing Gear
8. Controls, assembly, rigging
9. Engine, instruments, cowling
10. Disassembly
11. Sand and polyurethane
12. Cover, paint and reassemble.
It is always good to study the plans thoroughly before beginning construction; however, you will find that as you handle and dry fit parts together, many of your unanswered questions will answer themselves. And as always if help is needed its just a phone call away either to the designer or the fellow RagWing Newsletter members.
Step 1.
Begin the rib construction with the assembly of a jig board. The rib drawing is full size and will be placed on a piece of plywood or compressed board and then blocked up to allow constructing all 34 ribs from the same jib so that all will be identical Specifications and materials are listed on a complete Bill of Material. It is essential that the front spar rear spar and aileron verticals are exactly the same because these members are used to align the wing during assembly.
Step 2.
The tail feathers are constructed much like the ribs except that you must draw the outline of the tail from the dims. given in the plans. This is done because large blueprints cannot hold the tolerances given because of shrinkage. Draw out the tail feather prints on a flat table and cover with clear plastic. Carefully cut and dry fit all members. Glue together and allow to dry Before removing from table and jig blocks, fit and install all corner blocks and gusset plates. Remove from table, flip over and install remainder of gusset plates.
Step 3.
All spars all built from 3/4 X 3/4 cap members with a 1/16 ply web glued to the front side of the forward spars and the rear side of the rear spars. A fence is nailed down to one edge of your work table to build the spar against. Be sure to snap a chalk line so that they will be perfectly straight. Cover the work area with plastic and nail down enough small blocks to keep the caps in a straight line. Fit and install all verticals. Take care to get a good fit with no less than 80% contact between wood joints. Dry fit the web material. When all parts are ready to assemble remove pieces, glue and reassemble. Web material will be stapled in place while the
glue dries, then removed. Layout, drill holes and temporarily install all spar fittings.
Step 4.
To assemble the wing you first slide the ribs onto the rear spar and align ribs with the verticals. Next block the front spar up against the “fence” on your work table. Next slide the front of the ribs up to , and aligned with, the verticals on the front spar. Now dry fit all diagonals and compression members per prints. Be sure not to install the diagonals backwards. Before beginning gluing be sure that both spars are parallel and square. Glue all members in place and allow to dry. Next remove wing away from fence and secure to table with the front spar hanging over the edge of the table approx. one inch. Install all nose ribs and allow to dry. Install the 1.5 mm plywood leading edge wrap by first gluing the ply to the top of the spar and letting dry. Next wrap the ply and secure onto the bottom spar cap. This can be performed by two people or one person using strips of rubber inner tube and twine twisted on like a tourniquet (Follow builders instructions supplied with plans package.) Allow wing assemble to dry.
Step 5.
Install aileron trailing edge and gusset plates. Install aileron spars and allow to dry. When assembly is dry then drill and install the aileron hinge brackets and hardware. Cut, fit and glue the “X” bracing between each rib. Aileron may now be cut loose- and removed from wing. Install the aileron nose ribs and Install the leading edge wrap the same as the wing leading edge. Remember to polyurethane the inner surfaces of any wood and areas not accessible after ply wrap is installed. Install wing tip bows and fabric stiffeners. Complete all 4 wings. Upper wings will build much faster since no ailerons are incorporated.
Step 6
Draw out the fuselage sides using the “fence” as a guide for the upper longerons. Again cover with plastic so that your side will not be glued to the table. Fit and install the 3/4 X 3/4 longerons, the diagonals, the vertical members and blocks. to fuselage sides. Let dry then build another side directly over the top of the first side. After drying remove and install the 1/8″ ply fuselage sides. Build one right and one left side. (construct the fuselage spars per print. Start assembling sides by first placing the sides up-side
down on the table. Snap a chalk line down the center of the table to be used for aligning. next install the spars then the remainder of the horizontal 3/4 X 3/4 members. Cut and fit the 1/4 ply seat back/bulkhead and glue in place. After this has dried then pull the tail section together and secure by blocking and clamping. Install all horizontals and diagonals and then the gusset plates. Take particular care to keep the fuselage sides square and properly aligned. Complete the fuselage by installing the 1/8 firewall ply and
then the 1/8 ply bottom. Front and rear turtle decks will be installed during step number 9.
Step 7
While fuselage is still upside down on table, construct and install the landing gear. The gear was designed just like the remainder of the aircraft in as that there is no welding or tube bending required. Cut, drill, fit and bolt together the landing gear per prints. No bungee was used on the first ultralight prototype but is a option now offered and shown in the plans.
Step 8.
Assemble stabilizer, elevator and ruder to fuselage per prints. Level the top longerons fore and aft and side to side. Level stabilizer and fin. Make and install tail brace cables. With assistance, install wings to fuselage and adjust for proper dihedral and angle of incidence. Because of the way that the upper wing root brackets are installed the 2 upper wing panels are rigged as one wing. After wings are completely installed then the upper wing root fittings can be separated allowing the wingfold to be installed and used. Construct and install wing “I” struts and flying and landing wires. Install and rig all controls for proper movement of control
surfaces.
Step 9.
Install the engine, instruments, fuel tank, turtle deck, windshield, and all remaining parts of the airplane per the plans and engine supplier requirements. At this point you are considered 90% complete with only 90% left to do. We recommend only aircraft engines like 2si, Rotax 277, 447 and 503, Hirth ‘s F-23, 2703 and Mosler. 35 horse-power engines with a V-belt reduction called a K-Drive is still considered to be the best engine for the ultra-light version and the Rotax 503 for the experimental version. But many have been
successful with alternative engine like Kawasaki, 1/2 V.W., full 4 cyl. v w. ‘s and a 3 cyl.. Chevrolet Sprint engines but not enough testing has been completed to elaborate at this time.
Step.10,11, and 12
With a felt tip marker, mark the proper location of all metal parts and remove them from the airframe. Engine, instruments etc. will be protected and stored. Completely disassemble and lightly sand the entire aircraft. Brush or spray 2 coats of polyurethane to protect the wood. Fabric cover and paint the
aircraft according to the system you have chosen. I recommend Latex House paint because of its durability, low cost and light weight Only 1 and 1/4 gallons are used on the entire plane. It cost less than $200 of material including fabric to cover one light aircraft. My schedule is to rip the fabric off about every 5 years for complete inspection which I feel is very important for longevity so the latex system of covering has worked very well.
Flying the Aircraft
The RagWing SPECIAL is a very responsive yet gentle airplane to fly especially with the ultralight empty weight of 250 lbs.
Note:
The ultralight weight can only be made with a engine package weight of 78 pounds.
With its short 18 foot span it can handle wind easily and gives a quick roll rate. Taxing is very easy with a
steerable tailwheel and S turns are required for better visibility over the nose. You may take off in a 3-point
attitude or tail up. Normal ground run is less than 150 feet and climb is approximately 750 feet per minute
using a 35 h.p. Kawasaki 440A, 2.9 ratio belt drove and a 72 X 30 prop. Engine weight is 78 pounds. Using this set-up requires a throttle stop to limit the level speed to 63 mph. Without the stop cruising speed is 74 mph. Stalls are straight forward and very docile at 28 mph with a pilot weight of 170 lbs Landings can be performed easily at 35-38 mph with very little ground roll.
Recommendations
After you have completed the construction of your SPECIAL, had it checked by your friendly fliers and a Airframe and Powerplant Mech., and are ready to fly it, here are a few suggestions. Do not set a time to fly the aircraft. Do not invite any more help than necessary. Test off of the largest grass runway available Get fully checked out in a taildragger by a certified flight instructor. Take your time and get very familiar taxing the airplane in a tail up attitude until you can handle every situation When its time to fly, line up straight at the end of the runway, advance speed slowly to the point of liftoff. Gently feel out the controls then cut the throttle back in time to make a safe, easy landing. I usually do this several times to become comfortable with any new aircraft that I fly. Remember to keep a close watch on the engine instruments for any signs Of overheating, etc.
Take a break and you and your friends give the airplane a good ground inspection. When all is well, take the SPECIAL up for a turn or two around the pattern staying within gliding distance of the runway. (Approx 6 to 1 glide with the prop not turning.) I don’t recommend flying a new airplane any distance from the airport until I have at least 40 hours and 200 landings and have stalled the aircraft. power on and off (at altitude) several times. During all of this time constant monitoring of the instruments and ground inspections should be performed.