If you want to add the six and two meter bands you can find a calculator at: http://www.softcom.net/users/kd6dks/quad.htm which will be for 4 elements.  If you want to know how this antenna works at 42 feet just ask Larry, N8BNE.

Over the years I tried many different pieces of hardware and as far as spreader arms go, I find what Larry used, (Cubex), to be probably the best, although a little expensive.  I found taking two pieces of angle 1/4 inch aluminum approximately 2 to 2 1/2 feet long bolted together and fitted with 2 inch muffler clamps was about the least expensive method and very strong.

Spreaders or elements have been tried from solid fiberglass, tapered hollow and bamboo.  The spreaders that I found to last the longest and withstand Michigan weather was bamboo sealed with Scotch 33+ tape, it will take at least two large rolls to do one spreader.  Don't use cheap electrical tape, it will come loose and you will end up with many flags after the first winter.  The Scotch 33+ will stay tight and keep the water out for many years, the spreaders Larry used had been in my barn for about 10 or 11 years and were removed from quads I had built over the years.  Some of those were 15 to 18 years old.

Don't drill holes to put your wire elements through, they were only called drill points by the fiberglass manufactures, they will only cause weak points in your spreaders.  Early years I only used electrical tape to connect the wire to the spreaders, but now the tie raps work great to get the wire nice and tight, and then tape.  Also using large tie raps to connect the spreaders to the spreader arms and then taping works great.  Always seal the upper spreaders so water can not build up in the tape and the same to the bottom, as this causes real problems when it freezes in the winter.

Now that we have covered the fundamentals, here a some quads from the past that really worked, but remember we didn't have WARC bands when these were built. If you have built a multi element four or more element five band screamer, pass it along and we'll put it up here also.

This was one of my first quads that I actually took a picture of, it was built on a 24 foot boom.  The 80 foot tower was centered in my back yard, 65 feet by 65 feet using a 4 way guying system.  This one helped put me over 100 countries for my DXCC.

This was the same antenna over a year later erected at new QTH and on 96 feet of tower.  I now had 18 acres to play with and spring was just around the corner.

This is the only picture I could find of the biggest quad I ever built.  34 foot boom holding 7 elements, 4 on 20 meters, 6 on 15 and 7 elements on 10 and 6 meters.  I held a QSO with this one which may be a record, I talked to my friend Rod, ZL3FM SK now, from 9PM local time till 10.15AM the next morning 13 hours and 15 minutes on 20 meters.  No time during the QSO did his signal ever go below S7 with 95% of the time S9 up to 30 DB over.  Antenna was only up from April to mid July of 1979 when 75MPH winds caught it sideways and snapped the 3 inch boom in half.  I guess I should mention, yes that was yours truly up there.  

The following are graphs of tested antennas and where they worked the best, keep in mind the one above worked great on 10, 15 and 20 and real good on 6.  

This one worked good on all three bands, with 20 and 15 working best.  10 foot spacing is a good compromise for 20 and 15 but drops off for 10.  

This one worked super on 20, great on 15 and good on 10.  It would beat the pants off any 4 element single band beam. 

This is probably one of the best compromises one could come up with for 5 elements on 20, 15 and 10.  With the closer spacing gives 15 meters the most gain here, 11DB or so, while the addition of a 5th element on 20 gets the gain back up to 10DB or so, and 10 meters is about the same.  This spacing also produces very good front to back on 20 and 15, but about 15 or 20 DB max on 10.  One must keep in mind with any antenna you reach a point of diminishing return, approximate gain with a 4 element Quad is about 10 DB.  One must double the elements to obtain another 3 DB.  The Big One theoretically produced 10 DB on 20 and close to 11.5 DB on 15, while 10 meter was around 12 DB.  Six meters was not far behind.

One more advantage of the quad that may not be known, metal elements or aluminum on beam antennas will produce rain static, where as the quad does not.  This may have been eliminated in the StepIR where the elements are inside fiberglass.  I remember running heads up single op single band in a contest against my friend Bruce AA8U one year on a rainy weekend, he had a quad and I had a beam.  Two or three times over the weekend the rain static on my end was 10 to 15 DB over 9 and I couldn't hear a thing, Bruce just kept right on going.  Needless to say he whooped me with well over 3 or 400 Qs.

Another thing one should know, you can broadband the beam by making the Reflector about 5.5% larger than the driven element and each director about 2.5% smaller as you go out.  This will reduce the front to back and slightly lower gain, but will allow you to have good SWR from CW through the top of the phone band on 20 and 15.  If you build for say a center frequency on 20 of 14.200 MHz for max gain and front to back you would use about 3% longer for the reflector and 2.5% shorter for the directors, all directors being the same size, not tapering down as you go out.  This will produce about a 1.5 to 1 SWR 50 to 75 KHz each side of center and climbing as you go further.  A two element quad is not as critical since only the reflector length starts to get into the picture as you go down.  If one wants good results for CW and phone with a two element, one could build the reflector for about 13.900 MHz and the driven for 14.150 MHz, you should be able to reach the top and bottom of the band with an SWR of under 2 to 1.

Good luck with your quad project and let me know how it works out.  In 1978 I received my Ph.D. (Positively Hears the Difference) Award by Clarence Moore (Inventor of the Cubical Quad 1942).