PDF Publication Title:
Text from PDF Page: 102
9/8/98 AC 43.13-1B 2-20. GENERAL. Nitrate dope and bu tyrate dope are manufactured by treating cel lulose, derived from wood pulp or cotton linter with select acids, then dissolving in a blend of solvents and adding plasticizers for flexibility. After a brush or spray application on fabric, the film develops tension and strength as the solvents evaporate. The tension and strength will increase in proportion to the total film thickness. The fabric functions as a film for mer and carries no load until a crack develops in the dope film. An excessively-thick dope film will develop too much tension and may warp or damage a light airframe. a. Viscosity adjustments for brush or spray applications may also vary between brands. When the viscosity adjustment ratio is not provided or is unclear, the product manu facturer should be contacted for detailed in structions. If instructions cannot be obtained or the source of the dope is unknown, the dope should be considered suspect and its use is not advised. b. Dope, which has been stored for an extended period of time or under adverse con ditions, should be suspected of becoming acidic and should be tested before being used on cotton or linen fabric. In some cases, fresh production dope has also been found to have a high acid content and will begin to deteriorate cotton or linen in a period of a few months. The acid content of nitrate or butyrate dope should not exceed 0.06 percent, calculated as acidic acid. An acidity test can be performed by most testing laboratories if high acid con tent is suspected. c. Butyrate dope is superior to nitrate dope in weather exposure tests. However, ni trate dope provides better adhesion to natural fiber than butyrate dope. The adhesion of bu tyrate dope to natural fibers is adequate; it is not necessary to use nitrate dope for the first application and butyrate dope for all other ap plications. The presence of naphtha in nitrate dope, manufactured in accordance with can celed Mil Specs formulas, causes nitrate dope to be incompatible with butyrate dope; there fore, nitrate dope should not be applied over butyrate dope for repairs or refinishing; how ever, butyrate dope may be applied over nitrate dope. NOTE: Nitrate or butyrate dope thinners and retarders should not be substituted for each other, nor should automotive coating-type thinners be used. d. Clear dope produces the most tension and strength. Aluminum-pigmented dope will weigh slightly more than clear dope and de velop less tension and strength for the same film thickness. Pigmented color finishes will produce the least tension and strength due to the higher ratio of plasticizers. e. During the coating-buildup procedure, solvents released from each succeeding coat will penetrate and be absorbed into the previ ous dope film, temporarily releasing the ten sion and increasing the drying time between coats as the dope film becomes thicker. If elapsed time between coats exceeds several weeks at temperatures above 70 F, it is rec ommended that several spray coats of an ap propriate dope thinner or dope with retarder and/or rejuvenator added be applied to the lightly-sanded, dried dope film to open the sur face and provide cohesion for the next coat. This will reduce the possibility of surface cracks caused by dissimilar tension between the old and new dope film. f. All dope coats through the final finish may be applied with a brush; however, brush Par 2-20 Page 2-25 SECTION 2. APPLICATION OF DOPEPDF Image | AFS-640
PDF Search Title:
AFS-640Original File Name Searched:
ac_43.13-1b_w-chg1.pdfDIY PDF Search: Google It | Yahoo | Bing
5,000 BF Shipping Container Lumber Dry Kiln For Quality Lumber The 5,000 BF container kiln consists of one 40 foot high-cube aluminum shipping container... More Info
Shipping Container Lumber Dry Kilns by Global Energy Global Energy designed and developed the container kiln back in 1991. The purpose is to give access to portable sawmill owners, furniture makers, and small business the value added profit of dry kiln lumber and quality hardwoods... More Info
Vacuum Kiln Conversion Kit for Lumber and Wood Dry Kilns Convert your existing conventional dry kiln into a fast drying vacuum kiln. Similar to vacuum bagging in the boat building and aircraft industry, we have come up with a proprietary process which allows you to build a very simple vacuum kiln at a fraction of the price, and without the intensive conventional metal chamber structure... More Info
Vacuum Pump Cart System for Bagging Clamping Wood Drying and more Vacuum Cart with 2HP Pump and Dual Pistons with multiple multiplex vacuum ports and liquid reservoir... More Info
Vacuum Bagging Basics Vacuum bagging is a method of clamping, which has traditionally been used in the composites industry, but can also be used for vacuum drying materials, including wood products... More Info
CONTACT TEL: 608-238-6001 Email: greg@globalmicroturbine.com (Standard Web Page)