hello GOREUNCLE,
very nice video and comments
about the 'x' mark:
the 'x' mark is placed correctly on the MaGui's discs. the problem is somewhere else and i will try to explain it.
the 'x' angle is the angle (of a right triangle) opposite the side of target's course. the formula for this angle is: tan(x)=u1/u2 <=> x=arctan(u1/u2) where u1=target speed and u2=torpedo speed (use this formula for creating your tables that you are mentiong at your video.the tables that you are showing there are completely wrong and you must redo them.These tables are allready done for you as you will find out reading lower)
When discs are on their starting positions the '30' for a 30kts torpedo is matched with the '30' for a 3kts target (the 40kts torpedo is matched with a 4kts target and the 44kts torpedo is matched with a 4,4kts target).
3/30=4/40=4.4/44=tan(x) <=> tan(x)=1/10 <=> x=5,71°
so,when discs are on their starting positions the 'x' mark must point at the ''5,71'' of the inner marks of middle disc. As you can see the x mark is correctly placed to all setups for discs (either on the x15 setup or either on the x12 setup the 'x' mark is pointing at the ''5,71'' of middle disc)
so where is the problem ?
At low speeds of target there is no problem but ,as the target's speed increase, there is indead a fault reading for 'x' angle on the tool. This fault is not constant but it is increasing following a logarithmic fuction. in other words , the faster the target is,the bigger the fault that discs are giving as angle 'x'.
this is not caused by the 'placing' of 'x' mark. this issue is caused becuase the inner marks of middle disc are the tangent (or sine) scale for small angles (<5,71°). the discs are using the ''ST'' scale there which is a scale for tangent (and sine) of small angles. this scale is perfect for use at ranges (and not only) but it is not the proper one for use in order to give correct outputs for the 'x' angle.
The 'x' angle needs the ''T'' scale ,which is the scale for angles >5,71°,in order to get accurate readings from the discs.in other words, one more scale (the 'T' scale) must be added in the middle disc in order to read from there the 'x' angle.
i hadn't noticed this issue when i released the method back then becuase i used in my testing senario a low speed target (5kts) and i got a correct reading from disc(at low speeds works fine as i said before) so i moved on. Later, i discovered that as target's speed increase so is increasing the fault at 'x' angle reading and i found the cause of the issue that i mentioned above.
of course ,adding this scale to the discs ,i don't believe that worth the effort for two reasons:
1.the discs are allready 'heavy' numbered and
2.the 'x' angle can be found very fast from somewhere else.The angle 'x' is allready calculated in the shooting tables that come with the MaGui so you can use these tables for getting the ''x'' angle. i had edited ''The broken TDC Attack Method'' thread and showed there how to get the angle 'x' from these tables.
(
http://www.subsim.com/radioroom/showthread.php?t=169935)
ps: this method is not taking in account the parallax correction (the difference at bearings between torpedo tube 'eye' and periscope 'eye') so expect some tiny inaccuracies there.the further the target is,the less the parallax correction is needed.so, Avoid using this method for very close range attacks and prefer shootings to >1500m
all the best,
Manos