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Current Issue » November 2013

From the newsletter of the St. Paul Model Radio Controllers, Inc., Coon Rapids, Minnesota

Covering Material

by Ellie Pflager

I was asked to research airplane covering materials and their weight ratio. I have learned a great deal in doing this article. I guess you could say that I have had several “ah-ha” moments and now a lot of things that were discussed during show-and-tells make a lot more sense to me. For my research I looked at both manufacturers’ Web sites as well as many forum group sites and tried to find multiple “agreeable opinions.” Bob LaBrash was a great help when it came to the product weights; he gave me a great head start. Hope you find this information helpful.

Tissue
[Tech. Editor’s Note: There is some misinformation here. There are several types of “tissue,” but the lightest and best is known as Japanese tissue. The “grain” has to be determined, usually by tearing, it is not that noticeable. The grain is then laid down span-wise on a wing, and this instruction is very important. Good tissuing is an art.]

This is not Kleenex, but more like gift-wrap tissue. It really is paper that comes in different weights. Tissue works best on the lightest models; usually balsa models designed for Free Flight (not RC). It has a noticeable grain to it, and this grain should be applied in the direction needing most strength.

It is traditionally applied to the wood frame with dope, although thinned glue works fine. Once the tissue is applied to the structure, it is shrunk tight with a light mist of water, then sealed with dope or Krylon spray enamel.

Silk
This covering is actually woven silk fabric that is applied with dope. From what I could tell this covering is not used very often these days. I couldn’t find any other information on this type.

Silkspan
This is like tissue but contains other fibers, and is generally stronger but heavier. It can be applied in the same manner as tissue. It is a good covering for foam. The weight per square yard of this material is 6.17 ounces.

Fabric
Fabric covering can produce a very realistic finish and can be painted or purchased painted. Some are manufactured from real woven cloth and feature a simulated, hand-rubbed lacquer finish like full-size airplane finishes. It goes on like a film; roll out and apply, then iron on at low heat to properly activate the adhesive. Because of the low-heat iron it can be used on sheeted foam. The weight per square yard of this material ranges from 2.9 to 3.3 ounces based on brand.

Fiberglass
This woven material is great on solid structures, but not good over open areas. It can be used to seal balsa wood or foam and comes in a great variety of weights, the lightest (.5 ounces per square yard) being very light but flexible. This is a great substitute for silkspan when covering foam. It may be applied with epoxy (wood) or water-based polycrylic (foam). It adds great surface strength for very little weight. It can be applied in (or over) a form to produce a “shell” for a nose cone or heli body.

Plastic Coverings
Plastic Coverings are also known as polyester films, or heat-shrink coverings. These are all applied to the wood frame with heat that activates an adhesive layer on the underside of the film. Once the film is attached to the finished airplane kit frame, it is then shrunk tight with heat. Film types of covering produce the lightest model. The weight per square yard of this material ranges from 1.685 ounces to 2.700 ounces based on brand and color. Below are some brand comparisons that I did based on forum opinions:

1. Ultracote by Hangar 9: polyester type with a lower-gloss finish.

2. MonoKote by Top Flite: supposedly preferred due to a high-gloss, smooth finish and is long lasting and durable.

3. 21st Century Film by Coverite: handles extreme temperature and humidity changes.

4. Litespan by Solarfilm Company: much lighter than MonoKote or Ultracote and has no adhesive on the underside, said not to shrink quite as drum tight as the other films. A 20 x 36-inch sheet weighs 31.8 grams.

5. Solite (Litefilm) by Nelson: super-light film but has adhesive on the underside, some of the “opaque” colors are somewhat translucent.

Painting
Painting is another option for finishing an airplane. Wood or foam structures must be sealed before painting to help produce a smooth paint surface. Surfaces that are sealed should not need as much paint and that will help keep the weight down. A primer coat is often applied after sealing. Its function is to create a surface that will bond well (chemically) with the paint layer.

I found there are several types of paint, each with their own benefits. Some examples are: dope, enamel, acrylic, and latex. Dope is a cellulose lacquer. Enamel gives a great finish but is tricky to clean up and dries slowly. Water-based acrylic dries quickly, easy to cleanup, and supposedly does not attack foam or wood. Acrylics tend to dry flat, so glass finishes need a separate clear coat. If your model plane kit (or heli) will use glow or gasoline fuel, the paint finish will need to be fuel proof. Many common paints are not fuel proof so make sure your topcoat is fuel proof, possibly a clear.

In my research I found the following Web site tutorials that seemed good to me. Thought I would pass them on.

Tips for covering RC airplanes with heat shrink film:

www.rchobbies.org/planes_covering-tips.htm

www.rc-airplane-advisor.com/heat-shrink-covering.html

Tips for covering RC airplanes with fiberglass:

Home.fuse.net/ryan/glassing.html Q

 

November 2013
Table of Contents

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President to President
Information Resources

On the Safe Side
Flightline Comnunication

Leader to Leader
National Model Aviation Day was a Success

Editor's Picks
Renewal Time

Know Your Site Owner's Policies

Six Keys to Success for New Pilots

Fuel: The Ins and Outs

Setting Up Your Servos

Eliminate Bounce in Your Landings

AMA Insider Archives Will Remain

Tips & Tricks

 

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