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MrT

Modeling for Competition:Basic Contruction

MODELING FOR COMPETITION

BASIC CONSTRUCTION






Ok here is where the rubber hits the road! We have decided to get serious. We are getting a handle on competition rules. The kit has been selected. Research of the subject is underway. Now it’s time to start putting the things we are learning into practice.

Competition rules can be a club to beat us up with or they can be a tool for success. Let’s use them as a tool shall we. I look at the IPMS rules as check list of things that need to be done or considered. So let’s look at them again and see where we need to start.

Aircraft

Basic Construction

1. Flash, mold seams, sinks marks, copyright marks, ejector-pin marks, and similar molding flaws eliminated.

2. Seams filled if not present on the actual aircraft.

3. Contour errors corrected.

4. Any detailing removed while correcting errors, filling seams, etc. restored to a level consistent with the rest of the model.

5. Alignment:

A. Wings/tailplanes: same dihedral or anhedral on both sides.
B. Plan view: wings and stabilizers aligned correctly with, and identically on both sides of, centerline.
C. Multiple fins/rudders: fin-to-stabilizer angles correct; aligned with each other in front and side views where appropriate.
D. Engine nacelles/cowlings: lined up correctly in front, side, and plan views.
E. Landing gear: components properly aligned with airframe and with each other in front, side, and plan views.
F. Ordnance items (bombs, rockets, pylons, etc.) aligned correctly with aircraft and with each other.

6. Canopies and other clear areas:

A. Clear and free of crazing caused by adhesives or finishing coats.
B. Gaps between windscreen, canopy, or other clear parts eliminated where applicable.
C. All clear areas scratch-, blemish-, and paint-free.

7. Decals must look painted on if depicting painted markings (conforming to surface contours, no silvering or bubbling, no decal film apparent).

Armor/Military Vehicles

Basic Construction

1. Flash, sink marks, mold marks, ejector-pin marks, provisions for motorization eliminated.

2. Seams filled where applicable, especially on cylindrical parts such as gun barrels, wheels, and auxiliary equipment.

3. Contour errors corrected.

4. Gaps between upper and lower hulls blanked off to prevent a “see-through” effect.

5. Gap/overlap at point where track ends join eliminated.

6. Machine guns, main guns, exhausts, vents, etc. drilled out/opened up.

7. Cylindrical cross-section of gun barrels maintained.

8. Track pattern (cleats) facing in the proper direction on both sides of vehicle.

9. Alignment:

A. Road wheels on tracked vehicles (along with idler, drive, and return rollers, if any) at the same distance from the lower chassis centerline.
B. Road wheels sitting flush on the track.
C. Tracks vertical (not leaning in or out when viewed from the front or back of the vehicle) and parallel (not toed in or out when viewed from top of vehicle).
D. All wheels/tracks sitting firmly on the ground.
E. Vehicle components square and aligned.
F. Gun(s) (on most turreted vehicles) parallel to turret centerline when viewed from above.
G. Items positioned symmetrically on actual vehicle (e.g., headlights and guards, fenders, mud flaps, etc.) positioned symmetrically on model, unless represented as damaged.

Automotive

Basic Construction

1. Flash, sink marks, mold marks, ejector-pin marks, and similar molding flaws eliminated.

2. Seams filled if not found on the actual vehicle. (This is especially important on the car’s body. Rubberized kit tires usually also have a mold seam that must be removed.)

3. Contour errors corrected.

4. Gaps between body and chassis eliminated as applicable.

5. Detailing removed while accomplishing the above steps restored to a level consistent with the rest of the model.

6. Alignment:

A. Where applicable, external items (e.g., mirrors, exhaust pipes) aligned symmetrically.
B. Internal items (e.g., seats, some engine/drive components) aligned properly.
C. Wheels: All wheels touching the ground and aligned properly when viewed from front or rear of the vehicle. If turned, front wheels should be aligned in the same direction.

7. Windshields and other clear areas:

A. Clear and free of crazing caused by adhesives or finishing coats.
B. Gaps between windshield, windows, or other clear parts eliminated where applicable.
C. All clear areas scratch-, blemish-, and paint-free.

As you can see the “rules” look more like a check list. On aircraft the first four items, armor the first eight, and automotive the first five deal with the preparation of the parts. While the other items really deal with assembly and most of the items listed are self-explanatory except for maybe item one. Now let’s take a moment and talk about item one “Flash, mold seams, sinks marks, copyright marks, ejector-pin marks, and similar molding flaws”.

Flash

•Excess plastic at parting line or mating surface of the mold
•Normally very thin and flat protrusion of plastic along an edge of a part




Sink marks

•Surface depression caused by non-uniform material solidification and shrinkage.
•Most often noted at interface between differing wall thicknesses.




Mold seams

•These are created when the two halves of the injection mold come together.




Ejection pin marks

•A rod, pin or sleeve which pushes a molding off of a core or out of a cavity of a mold.
•The pin will leave a mark or depression in the part.




Gate

•The Gate is the end of the runner. It is the entrance to the cavity.




Ok now that you have had a crash course in plastic injection molding I hope you will have a better understanding of the areas that may need your attention while preparing your kit parts for assembly.

Basic Construction Tools

1. Knife or scalpel




2. Sprue cutter




3. Sanding sticks




4. Cement/Glue




The tools for modeling are many and varied. Each modeler has their own way of modeling, but I think we can agree that these 4 items are basic to model building. As we go along with the building process we will get to see how each modeler in our class uses their tools to overcome the problems with the kits they have chosen. Hopefully we will learn some new things and master some others.

Basic Construction Steps

1. Study the instructions: instructions are like a roadmap so look the instructions over for anything special that needs to be done.

2. Do the steps in order: The manufacturer has arranged the steps for a reason. If you do things out of order you may regret it later.

3. Dry fit the parts: Check the fit of parts and assemblies before any cement is applied. Glue is not very forgiving.

4. Use a minimal amount of glue: Glue marks are first thing judges look for at a contest. Use just enough glue to get the job done.

5. Take your time: Modeling is not sprint, but rather endurance test. Don’t get in a hurry you might tear something up.

Ok I think we have enough to get started. So open those boxes and start cutting plastic. As usual I want to see pictures and explanations about what you are doing. This will help everyone learn something new. The next installment will be “Details”. From now on we will keep working as the next topics are closely related. Well let’s go!
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