Mainly for looks

I feel that main benefit for using easements is that the curves with easements look much better than curves without them.  While equipmemt looks much better easing into curves with easements  than without I do not think there is any real operational gain unless you are using a radius of much smaller than 30".

I have easements on the visible sections and curves without easements in the staging area and I do not notice any difference in operation.

I would at least try to use some easement and think that a 28" radius with easements would look better than a 30" curve without.

Easements

Agree. Try using a slightly smaller radius with easement on each end. That way you don't sacrifice tangent track length.

You won't have any operational issues with 30"R curves without easements. It is an aesthetic thing. Easements look good. 

Check out Jan-Mar 2009 MRH article

You should look at the article on car length v. radius. It might help you decide what you want to do with easements.

If it were me, I would reduce the radius with easements to save the operation possibilities elsewhere on the layout.

When Armstrong was writing

" I loose 9" of tangent length to get the easement "

Not really because the easement curve extending onto the tangent  is so slight that you can still fit in the same turnouts, they'll just be slightly curved.  I'd stick with 30 inch radius so the longer cars look better then ease them minimally by moving the tangent tracks a bit toward the walls so the flextrack can relax a little at the curve points  then forget about it.I built a similar O scale layout in a narrow room and used 46 inch radius ( equivalent to 25.4 inch radius in HO scale)without easements and it worked fine, the only thing that I found I could not run was 4 wheel front runners coupled to 89 foot pig flats. So get out there and make tracks.  .....DaveB

loosing 9" of tangent length sounds right

Actually 9" of tangent length sound correct.  Not that I think NMRA is gospel, but as an example, NMRA data sheet (D3b.3 for reference) indicated that for a 30" radius the easement should be 21" long.  Half of which would be in the radius and half in the tangent, making it 10.5 into the tangent. You could easily reduce the easement to 18" with 9' into the tangent. (this probably matches John Armstrong's recommendations)

 At your 30" radius, easements are less important that when radius are smaller, however all radius no mater how large should have easements.  Not only do they improve the look (a tighter radius with easements looks better than a larger radius without easement) is does make your equipment operate better. 

 In my situation, at a club I belong to, we had a 29" radius that lead almost directly into a turnout. I am also a big John Armstrong fan.  I cannot remember what his book said off hand.  I know I used his recommendation for a 30" curve and only used half of the easement that went into the tangent.  As you quoted 9" as half the total easement I will assume you got that from the John Armstrong's book for a 30" radius curve.  Using that information, I started my easement 9" before the end of the curve and then continued the easement for 4.5" into the tangent. The easement ended 1/2" before the turnout just to ensure the easement ended before the turnout. Looks great and we have not problems with equipment.    

 I would recommend decreasing the radius a little to include easements and then if you have to fudge the easement a little bit for your turnout.  

Art

Thanks everyone and I have a good solution in mind

I really appreciate the thoughtful and helpful comments you all made.  I love the ability to tap other modeler's experience on this site.  I take to heart the multiple comments that easement with a smaller radius will look better than no easement.

I have read the excellent article on car length versus radius, and that made me want to go no lower than 30" radius.  That article makes me wish I could fit 36" radius, but that is not to be.  This hobby is about endless search for compromise.

The 9" "loss of tangent" does come from the numbers John Armstrong suggests.  If I used a 28" radius, I could save a few inches of tangent length and still have an "Armstrong easement."  But, it would not save enough to save the day.  I could also move the edge of the curve even closer to the wall to gain a bit more tangent, but I don't love the scenery implications of that one.

But, then I realized that I was ignoring one of the benefits of my approach to the track work and switches.  I am using Central Valley tie strips and switch ties.  I have built several practice switches using CVT and Fast Track filing jigs, a la Joe Fugate (http://siskiyou-railfan.net/e107_plugins/forum/forum_viewtopic.php?5125.0).  They look great and operated very well on my pre-layout proving grounds.  Plus, they were fun to build.  I can make these turnouts take a curve to fit very well within the easement (you leave a few ties right around the points and the frog straight to make maintaining gauge easier, but there is still enough room to curve the rest of the switch and fit pretty smoothly into the easement).  Curving the switches to fit is not going to be that difficult since you pin the CVT tie strip down firmly during construction.  The only compromise is a bit more care and patience in building a few of my switches.

I can locate the frog in the exact same place as I would have if I skipped the easements.  If I want, I can locate the frog a bit farther back into the curve, actually gaining a bit of tangent length for the rest of my operating features.  My remaining "big decision" on this one is whether I use #8 or #6 for the curved turnout.  I'll probably go with #8 because it will give me a prettier looking set of track work and the diverging rail radius will be gentler.

Thanks again everyone.  I'll try to post a picture of this part of the track work once it is built (I work slowly, so don't hold your breath).  My admiration for the people who surveyed the pioneering rail lines in the 19th century grows all the time.

I used Armstrong's book in

I used Armstrong's book in designing and building my previous two layouts and incorporated his easements.  It only takes about an inch off your available room to add easements to a 30 inch curve so if you can fit 30 inches, and have a tiny bit extra to spare you can add easements have your cake and eat it too.  As for tangents yes, they are shorter by the approx 9-inches mentioned but if you cant have a siding long enough, due to this, then used curved turnouts or run the siding into the curve.  There are ways to tweak things and get what you are after, within reason.