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It’s been reported that Global’s Wacky Waco is a poor quality kit. No one discredits however, it’s flying qualities. In fact, there is a documented report of this design having a successful landing after a catastrophic failure of half the eppanage! As there aren’t many biplane kits out there under $50.00,(eBAY or elsewhere) I decided to buy it and see for myself. Here then, are my thoughts and observations on building this airplane:
Opening the box, everything is well laid out. Plans are rolled and all hardware is neatly packaged. Cabanes are stamped aluminum, pre-bent and ready to install. Landing gear legs are 1/8” bent aluminum. The wheel pants are essentially worthless. By reshaping the forward fuselage, the 2 halves of the vacuum formed cowling may be glued together to form a continuous unit and fiber glassing made much easier. This reshaping will facilitate installing the cowling over the engine mount. Apply a layer of 6oz. glass cloth around the rear, inside diameter of the cowl for secure attachment.
The photo instruction manual shows the tail feathers going together first so I started actual construction there.
If you own a pair of Midwest’s Balsa Cutters, this task goes quickly and accurately. Punch the die-cut parts as shown and dry assemble over the plans. First thing you’ll notice is that as you place these parts, the angles just don’t line up. Gaps abound everywhere. This is easily overcome by having gap-filling CA and activator on hand. I chose to use thin HandiBond CA as the primary adhesive then made fillets of thick CA at each joint.
Once you have both vertical and horizontals done along with rudder and elevator, block sand each smooth. Any remaining gaps should be filled at this time.
Cont:
< Message edited by PointMagu -- 9/27/2005 2:44:47 AM >
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The fuselage lamination is very straightforward with a few suggestions. Get several weights. This is a long fuselage and to prevent warping as the epoxy cures, having plenty of weights on hand will make things a lot easier. Also, the plans show open areas on the ply cores beneath the cockpit area. Once laminated with the outer balsa sides, these open areas create “pockets” that are very susceptible to cracking. My suggestion is to add stringers of 3/16” balsa along the inside seam lines of the 1st laminate then flip the assembly over and attach the other balsa side. This will give the long center balsa filler pieces something to attach to. You’ll soon see that as you add each piece to be laminated, long gaps result due to the balsa not being milled evenly. The length of the center filler is also short by about 1-1/2”. Scrap will be required to finish it out. Mix your 30 min epoxy with a few drops of isopropyl alcohol to make brushing easier and to make your adhesive go further. This is a large fuselage and it has 3 primary laminations to glue! Spackling makes short work of all the gaps once everything has cured. At this time, you may wish to change the manner in which servos are mounted for the rudder and elevator. I cut 2 access holes for standard Futaba servos in the rear area of the fuselage. You can reference the plans for proper location of this modification,(your radio gear may be different). Servo wires are routed through an outer nyrod tube, slit lengthwise to clear the connectors, attached to the finished fuselage side. The weight that this modification adds to the tail can easily be offset by adding additional weight up front, if necessary. The servo connectors can then be inserted into the wing center and routed to the receiver.
Cont:
< Message edited by PointMagu -- 9/29/2005 1:10:14 AM >
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An important note: You may find that once the fuselage has been laminated, the vertical stab may not fit in between the balsa sides as shown on the plans! The only recourse you have is to sand down the tail enough to get the stab situated as shown. This also holds true for the filler piece directly behind the cockpit.
Cont:
< Message edited by PointMagu -- 9/29/2005 1:11:32 AM >
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Another approach to the fuselage is to saw the nose off just foreword of the “U” shaped plywood landing gear plate. This allows the addition of a contoured firewall epoxied perpendicular to the laminated profile with triangle gussets glued behind for additional support. This is an old ukie construction technique that lends itself to this project. I’ve never had much trust in 1/8” laminated light ply for a firewall nor as a motor mount! The kit includes pre-shaped bulkheads to mount the cowling and fuel tank but only for the port side. There are 2 of these that the instructions show being laminated together. Instead, use these as templates for your custom-cut firewall. By making this modification, you will have build the mount out far enough to get the engine thrust washer out beyond the cowling. You will need to measure the engine that you plan on mounting in order to get an accurate measurement out to that thrust plate. Even with the extended arms of your mount, the engine may set too far astern to clear the cutout on the front of the cowl. A simple laminate of several ¼” aircraft plywood pieces drilled and bolted to the main firewall should suffice in getting proper propeller clearance. Two 3/16” holes may be drilled into the fuselage with doweling inserted as “pins” secured with 30 min. epoxy for added strength. The motor mount can then be bolted to the extension, blind nuts installed with throttle access and fuel lines drilled. Remember that IF you chose this method, the cowling MUST be reinforced with fiber glass for rigidity! Otherwise, stick to the plans and trust the designers.
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Wing construction mirrors the tail group. Gaps will need attention as will the top wing center section. Once assembled, trimming and some carving of the plywood ribs is required to get proper clearance for all the parts to fit properly.
I decided upon building lower wing panels 1st. The construction is simple and very straightforward. I used lead weights rather than pinning my parts to the work surface. The 20-1/2” trailing edge stock needs to be reduced significantly to contour shape prior to installing the top and bottom trailing edges. I knocked this down with a small razor plane followed up with 220 grit sandpaper. Be very careful to get the cabane ribs vertical! Once sheeted, the struts need these ribs to be perfect at 90 degrees to the wing surface. Another point: When knocking down the trailing edge, try to make both panels even. Once inserted into the fuselage, if the TE’s are uneven, the wing appears to have “twist”. That is, the 2 panels do not line up evenly on either side of the profile. If you have offset like I have, you can modify the sandwiched ribs that are glued to the inboard W-3 rib slightly to compensate for this twist. Also, be cautious when gluing the spars to the bottom wing inboard ribs. Once completed, you will need to remove that portion of the rib between the top and bottom spar. This is the area where the center ply main brace is inserted and epoxied.
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Even though the panels build quickly, they are incredibly strong utilizing spruce spars and 3/32” sheeting along with a hefty ½” square leading edge. Each of the 4 panels do require significant carving and sanding to finish. Be prepared! Aileron construction is quick and easy. Using that Midwest Balsa Cutter makes this job a snap. Use the plans to make your 1st aileron. Then, cover it with waxed paper and build the 2nd one over the 1st. This insures even sizing. Building over the plans proved not to produce consistent results.
You may opt to build the top wing in 1 piece as others have reported doing. I chose to follow the manual and join them at the center section. Primarily, I did not have the material to produce a 1-piece assembly so I followed the instructions. Clamping the 2 halves together is essential to providing a solid joint. Remove excess epoxy before it sets up with alcohol. This saves effort later on.
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Joined: 1/29/2005 From: Cumberland,
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The center cabane assembly is complicated but not impossible. However, IF you follow the very vague instructions, you won’t be able to mount your top wing so be forewarned! First, measure the solid wedge that is to mount between the aluminum inner-planes,(struts). You’ll find that the block is about 2” wider than the opening you just built into the bottom of the top wing. If you follow the manual, you’ll have to completely re-cut all parts and start all over on this step! Work from the wing, not the plans! Take all 6 ply pieces and the center wedge. Using a ruler, calculate how much to remove from the wedge to get it all to fit into the cavity of the wing. Once the excess has been removed, dry-fit one side and insert down into the cavity of the upper wing. Do likewise with the other 3 ply pieces. You will have to eyeball how far down into the cavity the plys should go. Then, you’ll have to cut and trim the plys to get a good fit. Remember, the top wing will friction-fit into this cavity with ¼-20 or smaller nylon bolts. Mark with pencil onto the wedge in order to know where to make your final glue joints. Don’t rush this step! Your wing incidence depends upon being accurate. The manual simply tells you to epoxy the plys together and then onto the wedge. The plys must be measured, trimmed and aligned prior to gluing to the balsa wedge. This was my biggest challenge in building the entire model. Once completed though, it makes a great and very secure wing attachment.
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Joined: 1/29/2005 From: Cumberland,
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The Global Wacky Waco is not a beginner’s airplane. However, anyone with intermediate building experience should be able to tackle the few challenges that present themselves. I’ve tried to present the assembly process as clearly and as accurately as I could. My powerplant is an OS Max, .60FP swinging a 12x6 wooden prop. The FP is no longer manufactured but mine is brand new in the box and should prove to be more than adequate to pull this baby around the sky. Hopefully, I’ll someday have a .90 FS to try. Four stroke engines simply seem to lend themselves best to biplanes….
Once I get the whole thing finished and covered, I'll start the final segment on rigging and radio installation. Hope this helps anyone out there that comes across this bipe...either at the field, in someone's garage or on an auction site. It's a moderate amount of work, especially in today's age of Oriental ARF's. However, I'm of a mind that she's worth it.....
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Joined: 3/7/2003 From: Port Angeles, WA, USA Status: offline
Have been flying a Wacky Waco for a while now. I had to rotate the landing gear a bit more forward to keep the plane from nosing over on our grass field. I did this by drilling a single bottom gear hole forward about 1/2 inch from the original. Also the motor I use, ASP .90, is quite a vibrator and I have to tighten things periodically. I was told a .60 would be marginal. Now, I don't think that is the case. The .90 performs very well. I can do knife edge loops and the snap rate is pretty violent. I recommend a small receiver. My Futaba 7 ch. bulges the wing mount area some. Bob
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Wacky Waco...Updated - 
