Fw-190 D9 MW-50 50-50 methanol and water 115L and "85Kg"?

[Llucmk]

Well, one mate from my squadron saw that in the main page of the D-9 says that the MW-50 is 50-50 methanol and water which is in a tank of 115L (85Kg).

 

Well, he calculated the density of the Methanol and the Water and it's not correct...

 

57,5 L of water x density 1kg/L =57,5 Kg

57,5 L x density 0.79Kg/L=45,4Kg

57,5Kg + 45,4Kg = 102,9 Kg And should be 85kg...

 

So we were discussing this and i saw that maybe the devs calculated the weight thinking only in all the fuel tank of Gasoline without Ethanol which it's density is : 0.745 Kg/L

 

So:

 

0.745Kg/L x 115L = 85,675Kg

 

I don't know if i'm wright or if there's something wrong in this. Could someone clear this doubt or tell me if the Devs are wrong?

 

Sorry for my bad English

Edited June 30, 2014 by Llucmk

[Demongornot]

Nice done !

But, i think they just use a simplification with the closest full/half number 5,10,15,20,25 etc

I also don't think it is exactly 115L exactly, it can be 2l more or less.

[gavagai]

Well, one mate from my squadron saw that in the main page of the D-9 says that the MW-50 is 50-50 methanol and water which is in a tank of 115L of 85Kg.

 

Well, he calculated the density of the Methanol and the Water and it's not correct...

 

57,5 L of water x density 1kg/L =57,5 Kg

57,5 L x density 0.79Kg/L=45,4Kg

57,5Kg + 45,4Kg = 102,9 Kg And should be 85kg...

 

So we were discussing this and i saw that maybe the devs calculated the weight thinking only in all the fuel tank of Gasoline without Ethanol which it's density is : 0.745 Kg/L

 

So:

 

0.745Kg/L x 115L = 85,675Kg

 

I don't know if i'm wright or if there's something wrong in this. Could someone clear this doubt or tell me if the Devs are wrong?

 

Sorry for my bad English

 

You are assuming that 1L of water + 1L of methanol = 2L of 50/50 water+methanol. Instead, you'll get something less than 2L.

 

You could be right that there is a mistake. But, the other big possibility is that the tank wasn't filled to capacity. 115L was also the size of the tank for GM-1 boost, and if that was significantly less dense, then you wouldn't want to change the CoG too much with MW-50.

 

 

This lady gets about 145mL when she adds 80mL of water to 80mL of methanol. So, the density of your 50/50 mix would be:

 

(80g water + 63.2g methanol) / 145mL = 0.99g/mL, or 0.99kg/L

 

--------------

 

One more thing to consider: the 50/50 mixture could be by mass, and not by volume! There are too many things we don't know to have a definitive answer. If we do learn more my bet is that ED got it right.

 

:book:

Edited June 30, 2014 by gavagai
added video

[Flagrum]

That video is really enlightening.

 

And while watching it, I wondered about something else. When we talk about MW50, do we speak of volume or weight? I.e. 1 litre water + 1 litre Methanol or is it 1 kg water + 1 kg methanol ?

[gavagai]

Haha, I just had the same thought with my edit. Good one flagrum!

[Llucmk]

You are assuming that 1L of water + 1L of methanol = 2L of 50/50 water+methanol. Instead, you'll get something less than 2L.

 

You could be right that there is a mistake. But, the other big possibility is that the tank wasn't filled to capacity. 115L was also the size of the tank for GM-1 boost, and if that was significantly less dense, then you wouldn't want to change the CoG too much with MW-50.

 

 

This lady gets about 145mL when she adds 80mL of water to 80mL of methanol. So, the density of your 50/50 mix would be:

 

(80g water + 63.2g methanol) / 145mL = 0.99g/mL, or 0.99kg/L

 

--------------

 

One more thing to consider: the 50/50 mixture could be by mass, and not by volume! There are too many things we don't know to have a definitive answer. If we do learn more my bet is that ED got it right.

 

:book:

That was an awesome vid.

[Kurfürst]

The tank has 115 liters capacity, but it was needed to maintain the CoG, also it was in some cases dual-purpose, and could be used for either to store MW-50 or aviation fuel.

 

Since aviation fuel has a density of about 3/4 that of MW-50, the same weight was filled (ie. ca 80 liter MW or 115 liter methanol, both weight about 75-80 kg), at least on the 109K. I think its very likely the D-9 followed the same procedure.