robert_e_bone
Can't you just do what Tony Banks of Genesis used to do and take either the left or right mono track of let's say a nice lush organ that was recorded in stereo as L/R mono and apply a slight delay to just one side?  It's not anything complicated - just put whatever short delay on one side or the other and that's it.
 
Really fattens it up, though - even with just that little short delay.
 
Bob Bone
 

That's kind of what the Haas effect is and what this thread is about. Some DAWs have a "track delay" parameter which is convenient. With Sonar, you'll need to use something like Channel Tools.

I just watched a Youtube video this past week that was put together on this topic (using Logic). It may contain what you want. Follows the technique Konrad mentioned above. I share below if interested:
 

I often clone a track, pan each track in opposite channels then just put sonitus delay on one channel with 0% dry and 0% feedback (click the "man"ual button twice to get to where you can adjust the delay time manually). then you can tweak it easily, I usually go anywhere from 10ms - 300ms+ depending on desired effect.

Again, the same principle. Channel Tools gives you finer control over small values though. I'm not sure 300ms still counts as Haas effect, that would be too extreme for me to perceive as one stereo sound.

I find another way of achieving similar is to stup the Sonitus delay with no repeats to two different vales say 27ms and 30 ms.

Hearing the voice first from the actual track then a quick left/right reflection to follow widens the track nicely. Faster settings for less slap...

If you really want to do VINTAGE HAAS effect, the delays back in the day were done with REVOX tape decks. So, if you have access to a TAPE DECK VST and it has the delay feature, try what everyone is saying above.
 
GENESIS, used this all over The Lamb during mix down (not to be confused with T Banks keyboard delays, which he applied during tracking using tape based echo devices, think ECHOPLEX or ECHOREC machines).  This sounded good and thickened up the keyboards but didn't give him the HAAS effect.  The mix on the LAMB is almost 100% HASS effected.  You can't hear the delay because it was timed to the tempo of the song and the delay signal fell right on top of the next beat, but what it does do, is give the mix more AIR (like a pseudo reverb).  They would time the delay using the REVOX pitch shifting capability (it could go +-7 semitones and everything in between).  This in effect changed the time between the record and playback heads.  They would make a large loop of tape (manually) and loop it around stuff hanging in the control room and just let the REVOX continuously run during the mixing section and pretty much send everything to the REVOX delay buss.  Oh yeah, they would then send the delayed return from this buss to the REVERB (they called it delay) busses and turn the faders ALL THE WAY off on the direct REVOX buss so they only had reverb affected HASS tracks and no direct HASS signals.
 
Sorry for the long explanation but I am still amazed with the REVOX tape delay trick.  I think Andy Johns might have discovered this but I don't think he knew it was called the HAAS effect and just stumbled upon this. I am just guessing here but it wouldn't surprise me if this was serendipitously discovered with playing around with the Abbey Road ADT that was all the range back then. I wish I could have been a fly on the wall back in the day.

I'm under the impression that Channel Tools is designed to work with true stereo pairs.  I'm working with mono tracks.  I record a mono track, duplicate the track, pan them far left and right and then delay one of the tracks.  I was really just looking for way, in Sonar, to delay a track, without plugins, by a predetermined amount in milliseconds.  The result is the ability to more accurately place an instrument in the stereo image:  See below:
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By Dave Moulton, with Alex Case and Peter Alhadeff
December 1992

"What this means for stereo is: a monaural signal that is undelayed to either speaker is perceived to originate at a point in space compatible with the idea that the sounds from both loudspeakers are reflections (the non-existent direct sound is inferred from these reflections - this is why it is a “phantom” image); a monaural signal that is delayed by less than seven tenths of a millisecond to one of the two loudspeakers implies reflection paths from a different location in the room. It will as a result cause the phantom image to shift toward the earlier speaker. The amount of shift in localization is related to the amount of time delay. I’ve noticed (fooling around with an SPX 900, for instance) that the phantom shifts quite reliably in linear increments from the center to the earlier speaker as I step through .1 millisecond delays from .1 ms to 1 millisecond. This is consistent with what Haas (and many others) found."
     

Approximate locations of phantom image for various delay times. With a 1 millisecond delay, the phantom appears to emanate from the earlier speaker. Longer delays yield erratic results, with the phantom emanating from various places, depending on the acoustics of the room and the spectra of the signal, among other things. By 10 milliseconds, the late signal begins to be heard as an echo, depending on the envelope of the signal.

 

Amiller, the channel tools plug in has a built in delay for side / mid / stereo imagining.
with that being said, I know exactly what your trying to do. typically I record to mono tracks for guitars and pan them hard left / hard right. I don't use the Hass on these but if im in a bind and find theres a hole in there some where (just need something else) I will duplicate the mono track (like you are doing) then I will nudge the duplicate slightly to the right (between 8- 6/10's of a second).
 
In the old days when all I had was tape, I used to produce a similar effect by running the dry signal of one track to a send patched in to a delay unit. then patch the return in to a tracks input.
 

Keni
I find another way of achieving similar is to stup the Sonitus delay with no repeats to two different vales say 27ms and 30 ms.

Hearing the voice first from the actual track then a quick left/right reflection to follow widens the track nicely. Faster settings for less slap...

Great idea here Keni.

You can use channel tools on mono tracks. Just use the delay and none of the panning controls. Sonar doesn't have a "track delay" parameter. If this bothers you, you could make an FX Chain out of Channel Tools with knobs assigned in the ProChannel. That way you wouldn't have to open any plugin window.

Sanderxpander
... you could make an FX Chain out of Channel Tools with knobs assigned in the ProChannel. That way you wouldn't have to open any plugin window.

It's not so much that I don't want to open a plugin window as it is I don't want to run the track through yet another signal processor.  I'm just trying to keep it simpler.  But, since Sonar doesn't have a "track delay" parameter, I'll probably try your suggestion above.
 
Thanks all.....