Pyramid #3/34: Alternate GURPS

[wabishtar]

I think I've noticed a bit of a problem with the vehicle design rules in Pyramid 34. I've been trying to design a submarine that has a comparable performance to a U-Boat. So I looked up a U-Boat in my copy of GURPS WWII : Motor Pool and I found a crush depth of 330 yards. Using the formula provided for crush depth, I can't get anywhere close to 330 yards without using force fields! Using the formula of dDR * 150 / (hull length in feet) = Crush Depth, I can't begin to approach 330 yards, or any reasonable crush depth at all. I'm not sure what the mistake is, but I'm pretty sure there is one. Can someone who knows more about this crunchy stuff help me?

[Tyneras]

If you assume the sub has enough armor systems to have -1 SM (at least 12) then it increases the armor value per system by 1 step and gives that nice modifier to dDR. Try playing around with that, I don't have my spaceship books handy to look up the numbers too see if it gets you there or not.

Edit: also, try using only the pressure hull for the Length value, instead of the entire sub.

[wabishtar]

Originally Posted by Tyneras

If you assume the sub has enough armor systems to have -1 SM (at least 12) then it increases the armor value per system by 1 step and gives that nice modifier to dDR. Try playing around with that, I don't have my spaceship books handy to look up the numbers too see if it gets you there or not.

Edit: also, try using only the pressure hull for the Length value, instead of the entire sub.

Tried that. Ended up with a crush depth of 20 yards. I think there's something seriously wrong with the formula.

EDIT: I made a mistake. I end up with a crush depth of 36 yards. Still only 10% of my goal, and my ship is over half armor.

[Tyneras]

Originally Posted by wabishtar

Tried that. Ended up with a crush depth of 20 yards. I think there's something seriously wrong with the formula.

How? According to wiki, the pressure hull of a type 7 is 165 feet, its 857 tons (SM +8?).
For a crush depth of 20 yards, we need. 20*165/150 = 22 dDR.
If it is 12 armor systems, then each one needs to be 22/(12*1.8)= 1dDR

That's the dDR of wood, if I remember right.

[wabishtar]

Originally Posted by Tyneras

How? According to wiki, the pressure hull of a type 7 is 165 feet, its 857 tons (SM +8?).
For a crush depth of 20 yards, we need. 20*165/150 = 22 dDR.
If it is 12 armor systems, then each one needs to be 22/(12*1.8)= 1dDR

That's the dDR of wood, if I remember right.

On a streamlined SM +8 hull, the dDR of steel is 3. Four systems in each hull section, 12 systems total, equals a dDR of 12. Multiply by 1.8, you get 21.6, which you rounded up to 22. 22 * 150 / 90 (the length of an SM +7 hull) is 36. I forgot to multiply by 1.8 the first time, which is how I ended up with 20. You'll notice I edited my post. Still 36 yards is a pretty pitiful crush depth.

[Tyneras]

Originally Posted by wabishtar

On a streamlined SM +8 hull, the dDR of steel is 3. Four systems in each hull section, 12 systems total, equals a dDR of 12. Multiply by 1.8, you get 21.6, which you rounded up to 22. 22 * 150 / 90 (the length of an SM +7 hull) is 36. I forgot to multiply by 1.8 the first time, which is how I ended up with 20. You'll notice I edited my post. Still 36 yards is a pretty pitiful crush depth.

Ahh, I see the difference. I am adding ALL the systems together, not just for a section. I'm home now, so I have all my files handy.

Anyway, my logic is this, the craft is SM 8, and has SM -1 from armor, so we use SM 9 parts. Using TL 7 steel, we have dDR 5 per system, total dDR 60 * 1.8 = 108, so we get a crush depth of (108 * 150) / 165 = 98 yards, not yet at 330, but getting closer.

Actually, if we change length from feet to yards, it works out to 306 yard crush depth. Pretty close.

Edit: and if we have 18 armor systems (-2 SM), we can have a sub of 18 SM +10 systems and 9 SM +8 systems, and a crush depth of 412 yards! Fun fun.

[wabishtar]

Originally Posted by Tyneras

Ahh, I see the difference. I am adding ALL the systems together, not just for a section. I'm home now, so I have all my files handy.

Anyway, my logic is this, the craft is SM 8, and has SM -1 from armor, so we use SM 9 parts. Using TL 7 steel, we have dDR 5 per system, total dDR 60 * 1.8 = 108, so we get a crush depth of (108 * 150) / 165 = 98 yards, not yet at 330, but getting closer.

Actually, if we change length from feet to yards, it works out to 306 yard crush depth. Pretty close.

Edit: and if we have 18 armor systems (-2 SM), we can have a sub of 18 SM +10 systems and 9 SM +8 systems, and a crush depth of 412 yards! Fun fun.

If we use SM +9 parts, the ship ends up weighing 3,000 tons instead of 1,000 tons. That's a big difference. I was going for a 1,000 ton ship.

[vierasmarius]

Bought it, love it. The "Spaceships as VDS Lite" is pretty cool. I know there are some existing SS design spreadsheets floating in the digital ether. Anyone planning to add in the new Ground/Water/Air options and systems?

[Mgellis]

Originally Posted by Gudiomen

Got this, rather liked it.

I must say, while I thoroughly enjoyed the When We Were Little article, I'm a little disappointed that it didn't go into more depth into the 0.1 [1] ST steps and left it for us to figure out. I realize there's no grand mystery, but I was kind of hoping to realize my "insects take back the house" campaign. The richness in examples for little critters made me drool for an expanded table that went into the 0.1 increments universe.

Sorry about that. When I was writing it up, while the core concept is actually pretty simple, it always ended up becoming crazy complicated as I tried to work through all the implications of adding an entire extra level of scale to GURPS. Armor. Movement and combat and reach with 3.6" hexes (especially since you can have Fractional Move and Fractional DR as well as Fractional ST/HP). I finally decided that if I couldn't do it right, I should just provide the basic concepts so people could at least try it out in their own groups if they wanted to.

Also, it's really hard to find weight values for most insects. (Honestly, don't these biologists know there are game designers who need this information?) I did find out that a black widow spider weighs just shy of one gram, giving her a ST of 0.2. I guesstimated that a honeybee would be ST 0.1 and a dragonfly would be ST 0.3.

[RyanW]

The formula for crush depth appears to be off by a factor of 10, and L should be in yards rather than feet.

Edit: An opinion. Unofficial. Not associated with any of the creators.