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Old 02-04-2018, 02:22 AM   #1
Kesendeja
 
Join Date: Jul 2013
Default Mythbusters Bedliner Bedlam and you

In MythBusters S09E17 they tested the properties of Line-X Bedliner. It was bulletproof, explosion proof and just all around amazing stuff.

Well in that light I have a player in my game who intends to use the stuff in ways god and the manufacturer never intended.

At the very least he intends to give a bunker a spray down, and was eyeing the cost of doing the interior panels of a car.

So I need stats. Specifically how much DR it adds to the material its sprayed on. Weight seems negligible. Any ideas are appreciated.
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Old 02-04-2018, 07:22 AM   #2
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Default Re: Mythbusters Bedliner Bedlam and you

It isn't magical. If it performed as you think then DARPA, Honeywell, Raytheon, General Dynamics, and the others will not be spending billions on ballistic armour research.
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Old 02-04-2018, 07:41 AM   #3
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Default Re: Mythbusters Bedliner Bedlam and you

Well, per Line-X's website, a lot of DoD forces are using Paxcon PX-3350 to harden their vehicles and building sites.

Anyway, a bunch of googling brought out this lovely fact sheet:
http://www.ecoandlogi.com/wp-content..._daf_tehni.pdf

It's a two part polymer spray, made of a polyurea spray and an unidentified resin, with an average density of about 9 lbs/gallon (which works out to a specific gravity of 1.1 or so). That's a little lighter than kevlar (specific gravity of 1.4 or so) but it's not negligible.

I'd probably model it as adding DR 15 at the weight of 5 lbs/square foot of surface that's it's applied to. You can make it thinner at half the weight, but you can't apply a double layer to get DR 30. Optionally, you can make it as thick as you like, adding 1 lb per 3 DR per square foot covered.

Be aware that high quality armor steel is ~1.2-1.5 lbs per 3 DR per square foot, and composites like Chobham are slightly better, so this stuff is not a miracle material that replaces armor steel or Chobham.
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Old 02-04-2018, 07:47 AM   #4
Kesendeja
 
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Default Re: Mythbusters Bedliner Bedlam and you

Thanks. I know it won't replace "real" armor, but for a DIY armor it works really well.
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Old 02-04-2018, 02:37 PM   #5
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Default Re: Mythbusters Bedliner Bedlam and you

From what I can tell, it works better as part of a composite construction. It isn't a practical replacement for proper armour, but it can help to reinforce it.
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Last edited by DanHoward; 02-04-2018 at 04:19 PM.
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Old 02-04-2018, 05:53 PM   #6
Jareth Valar
 
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Default Re: Mythbusters Bedliner Bedlam and you

How about spraying a boat hull? How would this help hold up vs reefs and the like?

It would probably be hell on tonnage, but could it be worth it?
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Old 02-04-2018, 08:19 PM   #7
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Default Re: Mythbusters Bedliner Bedlam and you

It's supposed to resistant to corrosion due to salt water and resistant to fungal growths, so it's suitable for seawater applications. It's a toughened version of a sprayable bedliner for pickup trucks, so it should be highly resistant to abrasion. It won't give much protection if you ram a reef at speed, but it should reduce damage if you sideswipe a reef.

You're thinking about applying it to a Lagoon-52 catamaran, right? So each hull can be approximated as a rectangle 52' long, 6' wide, and about 8' deep. That's not precise, but I think overestimating the width will make up for not calculating the length of the curved sides correctly. Nominal draft is 5', so extending the Paxcon 3' above the waterline should give you plenty of safety margin. Anyway, 2 * (2*52*8 + 2*6+8 + 52*6) works out to 1856 square feet that you need to cover, which I am going to round up to 2000 sqft for easy math. At 5 lbs/square foot for DR 15, you're looking at +10,000 lbs, which is 20% of your yacht's base weight and is going to drastically reduce your freeboard. If you just want abrasion resistance and not spall and explosion protection, you could go with a DR7 coating for +5000 lbs.

Per Vehicles, hydrodynamic drag increases with the square of the cube root of weight, and aquatic speed is inversely proportional to the cube root of hydrodynamic drag. So you're looking at around a 5% decrease in speed - which will be completely masked by the differences in wind speed and direction at different times of the day but will make a difference if you're in a yacht race or if you go on long journeys.
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Old 02-04-2018, 09:54 PM   #8
Jareth Valar
 
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Default Re: Mythbusters Bedliner Bedlam and you

O_o

.........

Color me impressed. Thank you ...yet again. (for everything so far)

Now, using this and the catamaran you stated for me. HP 155, moving at a full clip (6 yds/sec) hits a reef head on (hard immovable object) it would take and do 19d-1 damage correct? ((155*2)*6/100=18.6=19d-1) the average roll would be 66 (rounded up). Now 15DR doesn't seem like much, but it's definitely better than 3. How would you calculate a brush? Use the normal HP multiplier like a sideswipe or multiply HP by .5? That would be a big difference, 10d-1 (34 damage average) and 5d-1 (17 damage average) respectively (assuming my maths are correct).

Now, the car test in the show adds up pretty much solid. 6mph crash would only be 2d-1 for a sedan, and 7d-1 for the 25 mph test. No damage (6 damage vs DR15) and minimal (27 damage vs DR15)

That brings me to another question. If the base DR of the vehicle is 3, and this is a spray coating addition, not a replacement, would it not add to the base DR? Making a full coat DR18 and a half coat DR10?



OK, now back to the OP topic. How would this DR be affected by explosives? I mean, in the show, they used 1 brick (looks like Tory used 1 on the un-sprayed wood wall and Kari used 2, but...) of C4 vs the wood wall, and 2 bricks (?) vs the brick wall. DR 15 would be completely bypassed by an average roll of only 1 brick of C4 (5dx3).

It did look like there was some structural damage to the wood wall, but overall totally contained the blast. As for the brick wall, there was probably some fractured bricks, but nothing serious. In these cases, DR15 just seems too low. Dunno, still getting used to GURPS.

Also, question on your weight. At that weight per square foot, that would assume .55 gal per square foot and for the boat, that would mean over 1,100 gallons. As per Bed-Line Calculator spraying 1976 sq. feet with 1/8 " thickness would be 154 gallons. That would be only .077 gallons/sq.ft. and .7 lbs/sq.ft. for 1400 lbs total. Your calculations would put it at a hair under 1" thick. I don't think what they showed in the show was even 1/16 of an inch, given that you could still make our the joints of the brick wall perfectly.

Not trying to argue or anything. I'm just trying to understand your maths. I appreciate the help, especially since this helps me understand the system much better.

Last edited by Jareth Valar; 02-05-2018 at 01:41 AM.
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Old 02-05-2018, 01:03 AM   #9
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Default Re: Mythbusters Bedliner Bedlam and you

Quote:
Originally Posted by mlangsdorf View Post
Per Vehicles, hydrodynamic drag increases with the square of the cube root of weight, and aquatic speed is inversely proportional to the cube root of hydrodynamic drag. So you're looking at around a 5% decrease in speed - which will be completely masked by the differences in wind speed and direction at different times of the day but will make a difference if you're in a yacht race or if you go on long journeys.
Spraying goop on your hull is going to have much a greater impact on your speed than just from the extra weight.
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Old 02-05-2018, 01:43 AM   #10
Jareth Valar
 
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Default Re: Mythbusters Bedliner Bedlam and you

Quote:
Originally Posted by Daigoro View Post
Spraying goop on your hull is going to have much a greater impact on your speed than just from the extra weight.
Many of the bedliner companies offer varying textures, including smooth. Would that help?
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