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Old 02-03-2018, 04:15 AM   #11
Jareth Valar
 
Join Date: Aug 2013
Default Re: Need help with a 4e Vehicle

True, but from a couple of sailing forums/blogs I've looked at, a lot of sailors/boaters doing long ocean swear by using sea water for toilets, dishes, laundry and basic bathing (with rinsing with fresh water to remove the salt).

Not saying 21 gal isn't sufficient, the exact opposite TBH.

Thanks again for all the help.
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Old 02-04-2018, 10:02 PM   #12
Jareth Valar
 
Join Date: Aug 2013
Default Re: Need help with a 4e Vehicle

OK, now I've seen several brochures and videos for this thing now (want one in RL now... :-(, LOL)

There seem to be options for upgrading the engines from 54 HP each to either 75 HP each or 80 HP each.

Now, I've even worse with this kind of stuff. How would this affect the Move, a little, a lot or would it at all?
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Old 02-05-2018, 03:27 AM   #13
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Default Re: Need help with a 4e Vehicle

Assuming that the propellers, etc. are able to properly use the added power (which seems likely, as we're not talking about much compared to the displacement of the boat), a rough guess would be to increase speed by the square root of the ratio. Thus by x1.18 and x1.22 respectively.

This would make Move 0.5/5 for either of the upgrades. Acceleration would stay at 0.5 unless you're interested in playing with small fractions.
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Old 02-05-2018, 05:46 AM   #14
mlangsdorf
 
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Default Re: Need help with a 4e Vehicle

Vehicles for 3e scales water speed with the cube root of propeller power, and acceleration linearly with propeller power. That's accurate enough, though real ship designs have their hydrodynamic lines optimized for their expected top speeds and going faster or slower than that can change their effective hydrodynamic drag.

A better estimate would be 0.75/4.5. You're going to need a much larger engine to go faster. Hitting 20 mph would require 450 kW engines, for instance. It's not improbable, though: the trimaran designs for the US Navy claim to be able to sustain 50 mph for 5 to 10 hours.
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Old 02-05-2018, 06:38 AM   #15
Jareth Valar
 
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Default Re: Need help with a 4e Vehicle

Thanks to both of you.
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Old 02-22-2018, 07:29 AM   #16
Jareth Valar
 
Join Date: Aug 2013
Default Re: Need help with a 4e Vehicle

OK, here's something that has me curious. Apparently Carbon Fiber and Kevlar are used to make some boat hulls stronger, more rigid and lighter, up to 20%-30% from a couple articles I've read.

How would this translate into GURPS?

A reduction of weight/mass would decrease the ST/HP, but it is supposedly of a stronger material.

Would it increase the HT rating? If so, how much?

DR? ( I know it won't make it ballistic resistant, wrong application of Kevlar).

Or would this be treated like weapon quality and you treat HP/ST off of it's "default weight"?

How would this effect Move?

Thanks again
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Old 02-22-2018, 08:58 AM   #17
mlangsdorf
 
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Default Re: Need help with a 4e Vehicle

So it generally doesn't make a lot of sense to me that lighter, more advanced materials make your vehicle more fragile. Vehicles 2e handled this better. For 4e, I'd just treat it as a weapon quality thing and calculate HP/St of the default weight.

That said, I'm pretty sure that the Lagoons' hull is already carbon fiber, so it's not getting any lighter.

But for other boats, roughly speaking, drag increases with the square of the cube of weight, so to a vague approximation, doubling weight increases drag by 50%. Speed varies inversely with the cube root of drag, and so halving the weight increases speed by about 16% and doubling weight decreases speed by 16%.

So a hypothetical Lagoon made entirely out of wood that weighed 30% more would have about 94% of the speed of the standard Lagoon made from carbon fiber. Alternately, if the standard Lagoon is made from wood, switching to carbon fire and reducing the weight to 70% of the stock would increase speed by about 8%.

Huge caveat: Hydrodynamics is a really complicated subject, there are a lot of subtle breakpoints and weird behaviors, and these are really rough guidelines. All of the speed numbers are probably +/- 5% or so.
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Old 02-22-2018, 11:43 AM   #18
Jareth Valar
 
Join Date: Aug 2013
Default Re: Need help with a 4e Vehicle

That what I was thinking, just keep ST/HP the same.

Would HT increase at all?

or DR from 3 to maybe 4 or 5?

Would it give quality bonus to the Sailing roll?

Just asking as weapon quality gives modifiers to breakage, but there isn't a mechanic or that outside of DR and HP for things like this are there?

Not trying to squeak out bonuses or anything, but somewhere down the line there might be a possibility to change things/upgrade if possible. Just leke to have options if at all possible. It will also give the GM some possible extra stuff to surprise us with should the need arise.

Thanks again, you're a real help.
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