Dead space impact on mash stiffness

[PhilMcGlass]

My mash set-up is G Wheeler double bucket design.
I am wondering what effect the space below the inner bucket has on mash stiffness?
I think the space is about 4 litres.
If I mash 10 litres with 4kg grain there is only 6 litres in contact with the grain.
Is the stiffness 2.5 (10/4) litre per kg or is it 1.5 (6/4) litre per kg?
Does that make sense?
Is it likely to make any difference to efficient extraction?

[Horatio]

I personally would go for 2.5:1 plus the dead space or, like you say, the mash will be a bit too stiff. A stiff mash will create less fermentables than a loose mash IIRC (lower alcohol and more body to the beer). I'm no expert though so hopefully one will be along in a minute!

[PhilMcGlass]

Thanks Horatio.
What I meant was, is the liquor that is not in contact with the grain included in the stiffness calculation?
If I want 2.5 stiffness to I need to add more liquor to compensate for what is below the base of the inner bucket?

[OldSpeckledBadger]

If I want 2.5 stiffness to I need to add more liquor to compensate for what is below the base of the inner bucket?

Yes.

[PhilMcGlass]

Many thanks folks.
I just need to do some checks on heat lost when adding liquor to the tun.
Then fit a tesco element to a HLT bucket and we're away to try for AG Bass clone (GW book).

[Mitchamitri]

With that much deadspace sound slike you are using a steamer!! I's chuck another 2 litres of liquor in - uses the strike temp calculator on the links above to check the different temp you will need to pitch at.