Hull size table

A thread of 2 messages, 21 September 1993 to 22 September 1993, in the order they were sent.

#6070 Hull size table

I was just sitting down to design a ship design aide for the new
rules. The first thing was to convert the "hull size table" to a
formula, because I have always disliked even sized hulls. One doesn't
see discrete sizes of automobiles, nor are we in Niven's universe with
discrete sized General Products hulls.

Below is the hull table I got from plugging values into the
correct formulae for a sphere. L was calculated from volume:
	vol = 4/3 pi r^3 (where L = 2*r)
and the material value from:
	surface = 4 pi r^2, and multiplied by 0.01 to get a 1cm volume.

Note that in the 30 Ton - 20,000 Ton  range the figures are quite
similar, but outside those values significant deviation occurs.

Comments??

  Rate	     Vol	    MV	     L
     1	      14	  0.28	  2.99
     2	      28	  0.45	  3.77
     3	      42	  0.58	  4.31
     4	      56	  0.71	  4.75
     5	      70	  0.82	  5.11
     6	      84	  0.93	  5.43
     7	      98	  1.03	  5.72
     8	     112	  1.12	  5.98
     9	     126	  1.22	  6.22
    10	     140	  1.30	  6.44
    15	     210	  1.71	  7.37
    20	     280	  2.07	  8.12
    25	     350	  2.40	  8.74
    30	     420	  2.71	  9.29
    35	     490	  3.01	  9.78
    40	     560	  3.29	 10.23
    45	     630	  3.55	 10.64
    50	     700	  3.81	 11.02
    55	     770	  4.06	 11.37
    60	     840	  4.31	 11.71
    65	     910	  4.54	 12.02
    70	     980	  4.77	 12.32
    75	    1050	  5.00	 12.61
    80	    1120	  5.22	 12.88
    85	    1190	  5.43	 13.15
    90	    1260	  5.64	 13.40
    95	    1330	  5.85	 13.64
   100	    1400	  6.05	 13.88
   200	    2800	  9.61	 17.49
   300	    4200	 12.59	 20.02
   400	    5600	 15.25	 22.03
   500	    7000	 17.70	 23.73
   600	    8400	 19.98	 25.22
   700	    9800	 22.15	 26.55
   800	   11200	 24.21	 27.76
   900	   12600	 26.19	 28.87
  1000	   14000	 28.09	 29.90
  2000	   28000	 44.59	 37.67
  3000	   42000	 58.43	 43.13
  4000	   56000	 70.79	 47.47
  5000	   70000	 82.14	 51.13
  6000	   84000	 92.75	 54.34
  7000	   98000	102.79	 57.20
  8000	  112000	112.36	 59.81
  9000	  126000	121.54	 62.20
 10000	  140000	130.39	 64.42
 20000	  280000	206.98	 81.17
 30000	  420000	271.22	 92.91
 40000	  560000	328.56	102.27
 50000	  700000	381.26	110.16
 60000	  840000	430.53	117.06
 70000	  980000	477.13	123.24
 80000	 1120000	521.55	128.85
 90000	 1260000	564.15	134.01
100000	 1400000	605.21	138.80
200000	 2800000	960.70	174.87
300000	 4200000	1258.88	200.18
400000	 5600000	1525.02	220.32
500000	 7000000	1769.63	237.34
600000	 8400000	1998.34	252.21
700000	 9800000	2214.63	265.51
800000	11200000	2420.82	277.59
900000	12600000	2618.57	288.71
1000000	14000000	2809.11	299.03

And for those of you who might think my programming is at fault,
here is a section of the code used:

	double l,mv;
	int rate,vol;

	(value is the rate, read in from a file)
		rate = value;
		vol = 14 * rate;
		l = 2.0*cbrt(vol*3.0/(4.0*M_PI));
		mv = 4.0*M_PI*(l*l/4.0)/100.0;
		printf("%6d\t%8d\t%6.2f\t%6.2f\n",
			rate, vol, mv, l);


			-Dan



Dan Corrin,	Network Manager,       Mechanical Engineering
[email removed] 		University of Western Ontario
Smiley du jour:			      London, Ontario, Canada
:^(	has had his nose put out of joint; useful for replying to flames

#6072 RE: RE: Hull size table

Dan Corrin [email removed] wrote:
> I was just sitting down to deisgn a ship design aide for the new
> rules. The first thing was to convert the "hull size table" to a
> formula, because I have always disliked even sized hulls. One doesn't
> see descrete sizes of automobiles, nor are we in Niven's universe with
> iscrete sized General Products hulls.

> Below is the hull table I got from plugging values into the
> correct formulae for a sphere. L was calculated from volume:
>       vol = 4/3 pi r^3 (where L = 2*r)
> and the material value from:
>       surface = 4 pi r^2, and multiplied by 0.01 to get a 1cm volume.

> Note that in the 30 Ton - 20,000 Ton  range the figures are quite
> similar, but outside those values significant deviation occurs.

For the hulls from 1 to 10 tons the text in the Tech Book gives a hint:
cite from page 2, Configurations (under the Hull siye table)
"Hulls of 10 tons or less in displacement are elongated six-sided blocks, and
 are assumed to be laid out in a utilitarian form."
This will result in some inaccuracies, if a sphere hull is assumed. But all in
all I think the only cause of the values in the tables is the cut down of
fractions in calculations.

For the larger hulls, you should take into consideration that the errors of
your formula are within 10% of the MV given in the table. The same is true for
the length. This shouldn't bother you, especially if you compare it to the
section of the text talking about Deck plans, which says:
"When comparing the final number of grid squares used on the deckplan to the
 rated tonnage of the vessel's design, allow 10-20% leeway."
Your calculations are more exact than those in the table, so keep them. A
deviation of 10% in the hull volume does not much damage. If I'm correct in
my observation, that the calculated values for smaller hulls are smaller than
those in the table, and the values for larger hulls are greater, there should
be no problem, because with increasing displacement, the part of the volume
devoted to the hull shrinks significantly. And of corse the Hull Form and
Configuration Table give much more error margin than you could include
using your formula.

One more thing: There are no Asteroid hulls any more. I will use the
Megatraveller rules for this. Will there be any rules for hollowing out
asteroids?

Juergen

- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Juergen Kirsch
Institut fuer Informatik, Universitaet Bonn
Germany
[email removed]