Air Compressors

What kind of air compressor is required for building an RV? Somewhere Van's recommend a 75 psi 4-5 cfm (cubic feet per minute) compressor with a small tank.In this country it is difficult to get anything below 115 psi.The key here is the number of cfm that are produced and at what pressure. Most air tools work at 90 psi, so that is the minimum pressure compressor should deliver and is the pressure that the cfm rating should be given. Letís take Vanís 4cfm (but at 90 psi) as a minimum. More than 10 or 11 cfm is probably overkill for homebuilding. The other issues are tank size and max pressure. If you buy a large tank (say more than 50 litres) and a high pressure (say 150 psi or more), your tank can sustain your 90psi working pressure for some time. You have increased the short term effective cfm rating of the compressor. The compressor doesnít have to run all the time, is less noisy, and can be of a lower rating.

Horsepower ratings can be misleading Ė cfm at 90psi is a better measure. Tank size is often not critical, but more is usually better Ė 25 litres is probably a minimum. Maximum pressure is also not critical, 115psi is probably the minimum, and again more is usually better. Take a look at your most thirsty air tool, usually your drill.A good quality high speed drill can consume up to 14 cfm when running continuously.A 9-10 cfm compressor with 50-100 litre tank will be able to keep such a drill going at top speed during an intense period of hole drilling.It is rather frustrating to have to stop work every few minutes to wait for your compressor to catch up. If you plan on painting your aeroplane yourself then your spray gun may be the limiting factor Ė your finish quality will be compromised if you have to stop spraying and wait for the compressor.

The other factor to consider is the noise the compressor makes. Direct drive (or oil less) compressors run much more quickly, and are much noisier than, belt drive examples - but they are cheaper. Most people have to put their compressor in their workshop, you might think you can with stand the din, but direct drive compressors are very noisy and it will become very wearing at the end of a dayís drilling. The final factor is vertical or horizontal. If you have the space to hide away a horizontal version then that is perhaps better, a vertical takes up less floor space.

 

So what kind of compressor would I buy? Since I have had an air compressor I have found it very useful; I also now buy pneumatic tools when I can as they are generally much lighter than electric versions. I would suggest 2 types:

 

 

If you think you will use air tools after building your aeroplane I would go for a belt driven example such as the horizontal tank version opposite or the (more expensive) vertical tank version below that takes up less workshop space. If you donít expect much use after your project I would probably settle for a direct drive version (although I would construct a sound proofing enclose around it, with ventilation), such as the below right. I canít tell if it meets the cfm rating above, but itís probably the minimum you could get away with at 2hp.