I found a copy of the text that was in that article. Unfortunately BP Hobbies, which is mentioned a a primary source for many of the powertrain and construction components is no longer in business.
Later - Bob
Park Cat
My good friend, Dick Sarpolus and I have joined forces to design a very simple to construct, all-sheet foam model that we call the “Park Cat.” Full size plans for the Park Cat are available through the Park Pilot Plans Service.
The basic material used here is 5mm thick White Construction “C” Foam that we purchased from BP Hobbies. You can also use the new Midwest Products Cellfoam 88. For the wing and tail components you can simply measure out the dimension of the wing and tail pieces onto the foam and carefully slice them out using a straightedge and a hobby knife, fitted with a #11 blade.
To layout the fuselage, position the plan over a piece of the foam and where there is a curved line use a straight pin to punch holes through the plan and into the foam at approximately ¼ to 3/8 inch intervals. For straight line areas on the fuselage, make pin punches through the plan at the beginning and end of each straight line. Remove the plan from the foam and use a pencil to connect the punches. Then cut out the fuselage with the #11 blade, using use the straightedge where necessary.
There are a few simple-to-make plywood parts needed for this model. These include the fuselage nose doublers, an elevator reinforcement piece, a bellcrank mount, an elevator control horn, a leadout guide, a pushrod guide, a battery area stiffener plate and a motor mount plate. The plan indicates what thickness plywood to use for each part.
You will also need two 36 inch long pieces of ¼-inch square basswood. One of these pieces will become the wing spar and one a fuselage spar onto which the two fuselage halves (top and bottom) will be glued. Note that these pieces are just slightly thicker than the 5mm foam pieces that they will be glued to. You can use a sanding block fitted with #220 grit sandpaper to thin down the bass wood strips in the appropriate areas to match the thickness of the foam, or if you have access to a small modeler’s table saw you can cut 5mm by ¼ inch pieces of basswood to begin with.
Once all of the wood and foam parts are cut out and sanded, and all of the hardware items are in hand (see the plan for a list of these…), assembly can begin.
Assembly
All the parts for this model can be assembled using 15-minute epoxy glue (Or even with 5-minute epoxy if you are fast!). Let’s start with the wing. Cut the wing spar to length and lay it down onto a piece of waxed paper on a flat building board. Apply a thin coat of epoxy glue to the edges of the forward and aft sections of the left wing that will butt up against the basswood spar. Make sure that the ends of the foam pieces are flush with the end of the spar. Press the foam pieces firmly against the spar and then weight the assembly until the epoxy cures. Repeat this process to glue the other two wing pieces to the spar, being careful to also glue the center joint of the wing halves.
Next glue the upper and lower foam fuselage pieces to the basswood fuselage spar in the same manner as you did the wing. Before you can glue the 1/32 plywood doublers in place - or any of the plywood pieces to the foam - you will have to make small punctures through the smooth skin that is on the BP Hobbies foam surface to allow the glue to grip properly. To do this accurately, position one of the doublers on its corresponding fuselage side and draw around the rear edges with a #2 pencil. Trace also the lightening hole locations. Using an awl or a scriber, punch a number of shallow holes, being careful not to punch holes in areas where the doublers will not cover them when glued in place. Using an acid brush, coat the inner face of one of the doublers with a film of epoxy and position it on the fuselage side. Weight this assembly and let it cure and then repeat the process to glue the other doubler onto the opposite fuselage side.
Make a row of small punctures through the wing skins along each side of the center line joint, then slide the wing through the slot in the fuselage. Line it up carefully and epoxy in place.
Glue the plywood elevator joiner piece in place (don’t forget the punctures…), and then bevel the lower forward edge of the elevator assembly at a 45 degree angle. Join the stabilizer to the elevator assembly using clear plastic packaging tape as a hinge (See the hinge detail on the plan). Cut a shallow slot and glue the elevator horn in place.
Slide the tail assembly into the slot at the rear of the fuselage, line it up carefully in all axes and then glue it in place. Check the alignment often until the glue cures. Now epoxy the rudder in place with approximately 1/16 to 3/32-inch offset to the right.
Attach the leadouts to the bellcrank, but do not bend the line attachment loops yet. Glue the 1/8 plywood bellcrank mount in position. Bend the pushrod from 1/16 music wire and insert the right angle bend at the rear into the elevator horn. Use a small nylon keeper to secure the pushrod to the horn. Slide the 1/32 plywood pushrod guide onto the pushrod and leave it loose for now. Insert the right angle bend on the front of the pushrod into the bellcrank from below. Now hold the bellcrank over the mount in the neutral position and move the assembly fore and aft until the elevator is also at neutral. Mark the hole position and drill a starter hole for the sheet metal screw that will anchor the bellcrank. Screw the bellcrank to the mount and then position the pushrod guide about half way between the trailing edge of the wing and the leading edge of the tail. Make a small slot for the guide and epoxy it in place. Next glue the leadout guide in place and then bend the line attachment loops.
Position the motor mount that came with your motor on the 1/8 plywood motor mount plate and drill small starter holes for the #2 Sheet Metal screws. Glue the 1/8 plywood mount to the front of the fuselage and make sure that there is at least a degree of offset in it before letting it cure.
Glue a 1/4 ounce flat washer to the underside of the outside wing for tip weight and the assembly is complete.
Although you could bend up a 1/16-inch diameter wire landing gear with small, light wheels for flying from smooth surfaces, we generally fly this type model over grass fields where a landing gear isn't practical, or needed. Get a friend to give you an easy hand launch and make a smooth dead stick landing on the grass. The plane will even perform better without the drag and weight of a landing gear. And a soft grass field is easier on the airplane when a crash does happen.
You can dress up your model to suit you taste by adding some trim colors using water based acrylic paints. We’re going to hold off on painting ours so we can explain that process in a dedicated How-To later on.
I’m handing the keyboard over to Dick Sarpolus now for some power thoughts.
Power system stuff
The power system consists of a motor, battery pack, speed controller, and timer. Taking advantage of today’s new technologies for high power and light weight, we use a brushless outrunner motor, Lithium Polymer batteries, an R/C type electronic speed control (ESC), and a timer specially made for C/L flying. We want a system having about 150 watts of power for good flying, meaning we want a motor which will turn about an 8x4 prop and draw about 15 amps from a 3-cell 11.1 volt battery pack, that makes the 150 watts we want, and we’ll need a battery pack with a rating of about 1800 or 1900 mAh to deliver the current for flights of about 5 or 6 minutes duration.
For specific hardware recommendations, we used a BP Hobbies A2212-10 brushless outrunner motor, a BP Hobbies 18 amp ESC, a 3-cell 1800 mAh PolyQuest Li-Poly battery pack, an 8x4 GWS prop, and a Z-Tron timer (Available from BSD Micro R/C). We also installed a prop saver device on the motor, it retains the prop with a small O-ring so the prop can move somewhat if it hits the ground, and won’t break on the landings. And of course you’ll need a Li-Poly battery charger to handle the battery pack. All of these components or their equivalents from other manufacturers are available from your local hobby shop or the many web-based hobby suppliers.
These electric power system components require proper care and handling, particularly the battery charging, to insure reliable performance and safe operation. We urge you to follow the directions which come with the equipment and ask more knowledgeable hobbyists if you have further questions. – Dick Sarpolus
Flying
Check to insure that the center of gravity is where it’s supposed to be according to the plan. To adjust this CG position move the battery fore or aft in small increments, double checking as you go. Fly the Park Cat on 35 foot long .008 diameter multi-strand cables, and use a 1/2A type control handle.
Launch the model downwind to keep tension on the lines until some speed is achieved. This model is capable of most of the aerobatics that are in the official AMA pattern, so start with the easy ones like loops and progress as you gain confidence.
If you have any question about this project, please feel free to email Bob Hunt at: robinhunt@rcn.com, or Dick Sarpolus at: rsarpolus2@comcast.net. Enjoy your Park Cat!
Sources:
BP Hobbies, L.L.C.
140 Ethel Road West – Suite J
Piscataway, NJ 08854
Phone: 732-287-3933
Email: support@bphobbies.com
Midwest Products Co., Inc.
PO Box 564
Hobart, IN 46342
Phone: 1-800-348-3497
Email: customerservice@midwestproducts.com
GWS
138 South Brent Circle City of Industry, CA 91789-3050
Phone: 909-594-4979
Email: usa@gws.com.tw
BSD Micro R/C, L.L.C.
9054 Gum Rd.
Carthage, MO 64836
Phone: 417-358-9521
Email: bob@bsdmicrorc.com