[cash]

do i add the dead space volume under the false bottom of my S.S mash tun to the calculated 1.3 qts/lb water needed to mash in

[tschmidlin]

You need to add it for strike water temp calculations, but not for calculating the amount of water needed to hit a specific water/grain ratio.

[hubie]

You need to add it for strike water temp calculations, but not for calculating the amount of water needed to hit a specific water/grain ratio.

If you really want to hit specific numbers, than strictly speaking I would say you do have to add the dead space to your mash thickness calculation. If you remove part of your strike water and put it down in the dead space, then you now have a thicker mash thickness up top.  It only really makes a difference with small grain amounts and large dead spaces, and for someone who (for some reason) wants to hit a very specific water/grain ratio.  If you had 10 lbs grain and 2 qts in your dead space, your mash thickness would be sitting at a water/grain ratio of 1.1 instead of 1.3.  Even with that example, though, I would be surprised if one would notice the difference in their beer.  I never worry about it.

[tschmidlin]

Sorry, I guess I wasn't clear.  When I calculate my strike water at say 1.3 qts/lb, for 10 lbs that's 13 quarts.  Then I add the dead space water, 2 qts in your example, for a starting water of 15 qts.  This (15 qts) is the number I use to calculate the strike water temp, but 13 qts is what I use to calculate mash thickness.

I agree though, I don't think you would really notice it in your beer.  As long as it is thin enough to hydrate the malt, the temp will have a larger effect than the thickness in my experience.

[cash]

thanks, that makes sense to me. I've recently started using Beersmith but I have been having a little trouble hitting the strike temps without a lot of temp corrections and  the mash seems a little dry also.I usually add some more strike water to get the consistency I'm looking for. Like you guys , I'm really not so concerned with the numerical proportions.