Some brands or even colors of silk shrink a little better than others but I have always covered with the silk wet.   When you do it dry you are counting on the dope to do all the shrinking.   What happens though dry is the dope wets the silk which causes it to loosen up and bag.  Then you are just hoping the shrinkage will pull it back to where you started.   When you cover wet-and STRETCH it as much as you can when you dope the edges down it will shrink down a little tighter to begin with.  Then dope will shrink it a LITTLE more.   It will never shrink as much as say silkspan does.   Also be sure you are using tautening clear dope- like Randolph tautening.   Even so it can take five or six coats to pull the last of the wrinkles out.   Then you can change to non-taunting and /or colored dope after you achieve tight covering.  Also might be better not to thin the dope more than 1/3rd or less.   

Dave

Water does not shrink Polyspan.  Put the polyspan on dry but try to pull the wrinkles out as you go.  Heating the polyspan will shrink it.   I never needed to use tautening dope.  The non-tautening dope will still shrink a bit and it is enough as long as you did not have it very loose to begin with.

I USED THE DARMHA WHITE LIGHTER SILK AND ALSO THE DYED COLORED THICKER SILK AND IT SEEMS LIKE IT DOESNT TIGHTEN UP AS MUCH AS THE LIGHTER WHITE SILK..IT MAY BE BECAUSE IT IS DYED AND IS PRE SHRUNK BECAUSE OF THAT.......THE LIGHTER SILK TIGHTENS UP NICELY BUT IT TAKES ABOUT 5 OR 6 COATS OF TAUTENING DOPE TO DO IT APPLIED WET AND PULLED TIGHT

Will,
 Pretty common that the silk is relaxing after first few coats. Usually needs 5 coats to start getting tight again. I  would proceed with doping and it will come back. However, FYI, 8MM is a bit too heavy for our needs. I have used it with success but, found 5mm to be better and it is a piece of cake to dye.

keep Doping'
Tom

Will,
I had this same problem on both my El Diablo and Barnstomer. I used both the wet and stretch and the dry pin/CA stretch methods (I like the pin/CA method, is to do inside). In both cases it took about 8 coats (50/50) to get it to reshrink to drum tight. I used the same silk you are using, no problems. Just keep going, let it dry several hours between coats in the sun if you can. Somewhere around the 6-7 coat you start to see it shrink tighter. Once it gets tight switch to non-taunting (like Sig lite coat, not the Super coat as that is the shrink clear). Good luck, post pictures.

Best,   DennisT

Here is the Ares

I bought it from Dharma Trading CO.
Black and silver , Habotai. 8mm

I am using Randolph clear butyrate tauntening dope, fresh, just purchased, and am thinning it 50/50 with
their thinner

8mm is too heavy.  Use 5mm or 5.5.  You can use the 8mm a little at a time to beef up stress joints.
For me, using my thinness, it's baggy after five coats and tight after six.  I don't even try to do ratios.  I just stir it until if feels good.