CLOWNING AROUND
This event has gained popularity in several regions and serves as an introduction to controlline racing. The rules are simple, build a Clown from one of three approved plans, with no deviation from the profile and wood sizes, use an engine up to .19 cu. in., put on a 1 oz tank with only a 1/8" fill tube and race it for 15 minutes using 10% nitro and the one with the most laps for that duration, wins!
The power plant is the trick, in which way you want to go, hull ass with lots of pits or, go for the economical route or do both with a radical Nelson .19, rear induction diesel like Bob Whitney plans to use, Todd Ryan holds the N.W. Regional record using a Moki .15, I plan on using MDS .18, larger cubes and try to control the fuel consumption.
The MDS may not be the best choice because of quality control problems, I hate it when a manufacturer starts out building an engine and then doesn't follow through. During breakin, the wrist pin clip tang broke off and sent it through to the top, after inspection I also found that the wrist pin broke right down the middle. The liner wear pointed out that it was ground not honed.
I've replaced the wrist pin with a gage pin and used .012" wrist pin clips made of piano wire. I also made a lap for the piston and the liner and fitted them together as best as I could. I recut the liner port timing to 130 degrees for the intake and 155 for the exhaust, cut the crank to open at 30 degrees ABDC and close at 60 ATDC. I ran it in with a APC 7 x 5 and it's turning 19,000 rpm with a fuel consumption rate of 1 oz for 2 min. 15 sec., don't know if it's good enough but I'll fly it and give it a chance.
The airframe is your typical small profile type, I've made some acceptable changes like adjustable leadouts, replaced the stab with a piece of basswood and rounded the nose down because I don't plan on using the optional 2" spinner. The weight of the basic airframe as shown is 10 oz, a bit heavier than I'm use to building but they tell me it needs to be heavy in order to whip it around to your pitman because you don't know where the engine is going to quit, fuel shutoffs are not allowed.
It's now time for the finish. I'm going to use a traditional stunt type finish. light silkspan on the fus and Polyspand on the wings. I like using this combination on an open bay structure race plane because it provides a durable struface and has held up rather well on previous racers plus, it's very light.
Below I've listed the procedure and must be followed if using Polyspan because, it hasn't liked nitrate dope combined with butyrate for a finish.
Finishing With Polyspan
-First coat, full strength nitrate
-Sand with 320 c/s all over
-Second coat, full strength nitrate
-Sand with 320 all over
-Put glazing putty on low areas, don't worry about small irregularities such as grain
-Third coat, nitrite thinned 50-65%
-Sand with 320 all over
-Fourth coat ( fus. only ) just before covering, thinned nitrate
-Cover fus with light silkspan, use thinner mostly, and thinned nitrate on those tough spots
-Fifth coat, fus only with thinned nitrate
-Sand with 320, you won't be able to sand all the wrinks down so don't try
-Sixth coat, thinned nitrate
-Seventh coat ( wing structure only ), butyrate thinned 50-65%, just before covering with Polyspan
-Cover with Polyspan using thinner and use butyrate for those problem attachment areas
-Coat wing with butyrate thinned 50-65%
-Lightly sand edges of Polyspan and wrinkles with 320 grit, don't go hard on it or it starts to fuzz
-Roughly sand fillet area with 100 grit and add filets
-Sand fillets with medium 3M-sponge pad, make sure you get all the shine off
-Coat all with butyrate thinned 50-65%
-Sand all with 320 grit
-Spray all with sanding sealer thinned with 65% thinner
-Sand all using a 3M Fine sponge pad, watch out for the edges on the Polyspan, it tends to fuzz
-Spray all with butyrate thinned 50-65%
-Use glazing putty on low areas
-Sand all with 320 grit
-Spray all with butyrate thinned 65%
-Sand all with 320 grit
-Start spraying colors with added pigment
-Spray clear coat ( I used Dupont 580s and 582 thinned 25%, one medium coat)
Photo shows finished plane, the covering and finish added 2.5 oz, with all hardware the flying weight is 20.5 oz. The CG came out on the money, according to the plans, not good. I may have to add some nose weight in order to whip it on a dead engine. Bottom right photo shows the tank and engine installation, note the micro-alligator clip for air bleed when fueling. If you decide to build one for yourself, try to get the gear wire as close to the wing as possible, the tank is mighty cramped on this project.
The image on the left was to be rendered into a decal as afixed to the wing panel but, time was running short and will be added after the contest and, after I figure out the right decal paper and ink to use on my inkjet printer.
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