'•!•••.. uli i i - < : ; i . . H"Vj ;;'i n o ; '

1 '

;l

CRAFTSMAN'S CORNER '

BYBENOWEN

AIR COMPRESSORS Air compressors come in many shapes and sizes. If you are building an all metal airplane or planning to do a lot of work with air powered tools, an air compressor is essential. Those who build numerous aircraft over a long period of time should definitely invest in a quality unit. The very best compressor is a cast iron one rather than an aluminum unit. The

biggest advantage of the high quality cast iron unit is the longer service life. Cast iron compressors usually run at a lower rpm; about 700 rpm is needed to reach the desired output, whereas the aluminum units usually run at 1,500 rpm for a matching output. Cast iron will cost about $200-5300 more. One of the features of aluminum is the light weight of the unit. The faster the compressor runs, the more likely it will need a water trap, particularly if you are painting. The water spray can be felt if the water trap is not

hooked up on a moist day when operating other power tools. It is unwise to operate the compressor without the water trap while spraying paint. Single stage compressors usually have one piston per cylinder and have a working pressure of approximately 100 pounds. Dual stage compressors have two pistons per cylinder. After the air is compressed in the first cylinder, it goes on to the second

cylinder, where it is compressed again and can have a working pressure as high as 200 pounds. This type of compressor, better for blasting and painting, will develop less water condensation and last longer because it operates cooler. "Duty cycle" is the number of minutes in each hour that the compressor is designed to operate. A 50% duty cycle can be operated 30 minutes during each hour. If large air draw is anticipated, you will need a high percentage duty cycle. A

This air separator works well to eliminate water. I turned the gauge so that when the needle points downline, I'm at 80 psi.

larger air tank can ease the burden to some extent on the compressor. Motors for power tools traditionally are either 1,750 or 3,450 rpm. The higher rpm unit will wear out faster. Most of the larger units will require 220 volts, so it will be necessary to wire to get the electrical efficiency of 220 volts. Three horsepower

EAA AIR ACADEMY Where young people bring their dream of flight to life

EAA JUNIOR AIR ACADEMY June 28 - July 3, July 5 - July 10

A week long adventure for youth ages 12 - 14. Participants will learn the principles of flight through simple hands-on experiments. Activities include a number of fun projects including making hot air balloons, building and flying gliders, launching rockets, and an orientation flight in an EAA airplane.

EAA AIR ACADEMY July 22 - August 2

An intensive learning experience for teenagers 1 5 - 1 7 years old. Topics include metal work, welding, fabric and composite construction and engine operation. Scheduled during the '97 Fly-In allows Academy participants full access to Convention forums and seminars. Each participant will also experience a flight in an EAA airplane.

EAA FOUNDATION INC.

EAA AEROMODELING ACADEMY July 12- 17

A new program that offers a unique experience for youth 14 to 17 years old who have an interest in building and flying model aircraft. The full range of modeling activity including gliders and U-Control. Co-sponsored by the Academy of Model Aeronautics (AMA).

Space is limited! Call EAA's Education Office at 888-322-3229 for additional information.

EAA AVIATION FOUNDATION, PO Bex 3O86, Oshkosh, Wl 549O3 114 FEBRUARY 1997

the air valve to let the air and water out at the end of each day and maintaining the oil level. Failure to maintain the oil level in a compressor is the number one cause of compressor failure. You will also see the rating in psi and cubic feet per minute. Many modern units achieve a high cubic feet per minute and a high psi. Operating at very high speeds leads to faster wear, but it gives you "more bang for the buck." One of the positive feaThis unit supplies oil to the tool. I have one tures of a high revving unit is that it can hose that I use for oil operations only. It keeps the oil from getting in the paint-spray take the pressure to 100 psi very quickly. hose line. This one will feed multiple tools all I have found that a 5 hp unit and a 20 day. Small oil feeders on each tool are handgallon tank is about the minimum that I ier for small jobs. The bow is optional. can use for painting, sanding, riveting, etc. output is adequate to operate a 60 gallon It is best to spend less on the tools and more on aircraft parts. That's exactly what tank. Tanks are also rated at output psi. Basically, the low rpm 1750 large tank I did, and I have a 5 hp, 20 gallon tank, one cast iron unit, running on dual stage with stage aluminum unit with a motor operat220 volts, is near the top of the line. Most ing at 3450 rpm and maximum psi of 125. larger shops have an 80 gallon tank; its pri- It puts out 11.8 cubic foot per minute at 40 mary advantage is its ability to cool down psi and 9.4 cubic feet per minute at 90 psi; it is right on the ragged edge of "barely adthe compressor between duty cycles. Proper maintenance of any unit can equate." An engine compression tester will ensure longer life. This includes opening require 100-120 psi, for instance.

I know many excellent homebuilts that have been built with smaller units, possibly with a little more thinner on the dope or paint when its sprayed on the aircraft. Economically, the HVLP paint sprayer (high volume, low pressure) is an excellent choice for the homebuilder. It reduces overspray and is more economical on paint. The reason that it is not used in commercial shops is that an HVLP unit simply doesn't operate fast enough to turn out the high volume needed in a commercial shop. When selecting an air compressor, are you a hobbyist or going toward a semi-commercial operation? This should guide your selection in purchasing an average or top-quality compressor. > CORRECTION

The December 1996 Craftsman's Corner stated that the strength of the material from which an AN bolt is made is 160,000 tensile. This is incorrect as an AN bolt is the equivalent of a "grade 6" bolt and the strength of the material from

which it is made is 125,000 psi tensile.

WICKS AIRCRAFT SUPPLY AIRCRAFT MATERIALS KIT SUPPLIER SPECIALISTS

WICKS AIRCRAFT SUPPLY OFFERS COMPLETE AIRCRAFT MATERIAL KITS FOR: ACRO SPORT I & II • POBER PIXIE • BARRACUDA • BABY GREAT LAKES • BUDDY BABY LAKES • CELERITY • CORBY CJ-I STARLET • COZY, COZY CLASSIC, COZY MARK IV • CYGNET • DRAGONFLY • E-RACER • GP-4 • KR I & II • LONGEZE • SONERAI • AND MANY MORE...

PROFESSIONALISM, COURTESY AND EFFICIENCY: ANYTHING NEEDED BY HOMEBUILDERS, ANYWHERE IN THE WORLD. THE FASTEST AND EASIEST WAY TO ORDER FROM A SINGLE BOLT

TO A COMPLETE KIT! Lett - Skybolt

Right - Cozy Mark IV

NEXT DAY SHIPPING - SPECIAL RATES ON 2ND DAY UPS SERVICE 12,000 PARTS IN STOCK - 100% SATISFACTION GUARANTEED Our Warehouse is overflowing with all parts you need to complete your aircraft airframe one part at a time or a complete kit packaged in one shipment. Next Day shipping is the norm and we will challenge any competition to beat our service. Special services we offer are custom cut lengths of tubing at no charge, customer sheet metal shearing, custom made lengths of tachometer cable, aircraft control cable swedging and custom cut spruce spar blanks.

^\

CALL NOW and order our comprehensive 350 page catalog complete with aircraft kit information and pricing - $5 U.S., $20 Overseas Air Mail -

refundable on your first order over $50.00.

^ •/&

f> v jf ^

WICKS AIRCRAFT SUPPLY 410 Pine St. Highland, IL 62249, USA

Phone: (618) 654-7447 and 1-800-221-9425 - Fax:618-654-6253

*" VW'

-'^ v \ ^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^ s~j NEW: Door-to-Door European Service!

Shipments sent DAILY • Special AIR Shipping Rates V FAX or CALL: WICKS orM.A.P. (English/French), U.S. prices For information, use SPORT AVIATION'S Reader Service Card

SPORT AVIATION 115