Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Martel732 wrote:
I already showed the math of why its bad. Less than 50/50 of doing a hull point that will be regenerated on a 5+ anyway. A miniscule chance of exploding, which the the result you really want. Helldrakes are best shot with weapons that have a bonus on the damage table. Unless you are Tau and have Robotech missiles.


Automatically Appended Next Post:
"Seriously though, if the first hit pens, then there is a 50% chance of another pen, quite a big difference between "basically 0"% and 50% chance."

That is not true at all.

Im sorry, but yes it is true. If the first assault cannon hit pens and there are 3 more hits, you have 3 more str 6 rending shots against AV 12. You need a six. You have three chances to get one pen, and can even have more than one. 3 chances is 1/6 + 1/6 + 1/6. Which is 3/6. or 50%. And yea, you can always get another hit, not just one.

You are not calculating your statistic correctly at all.

The chance for three assault cannon hits to pen AV 12 is (1-(.8333333)^3), not 1/6+1/6+1/6. This comes out to be 42%. But there is only a .1666 chance of getting the initial pen, so the total probability is 7%. Less, when you consider that the TL AC does not hit 4 times 100% of the time and the demonic save.

Getting three pens from 4 AC hits is statistically negligible.

So, I'm sorry, but your chances of stripping two HPs off a helldrake with an assault cannon is very, very low.

Martel732 wrote:
You are not calculating your statistic correctly at all.

The chance for three assault cannon hits to pen AV 12 is (1-(.8333333)^3), not 1/6+1/6+1/6. This comes out to be 42%. But there is only a .1666 chance of getting the initial pen, so the total probability is 7%. Less, when you consider that the TL AC does not hit 4 times 100% of the time and the demonic save.

Getting three pens from 4 AC hits is statistically negligible.

"The chance for three assault cannon hits to pen AV 12 is (1-(.8333333)^3), not 1/6+1/6+1/6." No, you are not calculating them right at all.

1-.833333 = .166666
.16666 * .166666= .0277777777
.027777777 * .1666666= .00462

So according to your math, the chance for 3 hits to pen is .00462%

Its not right at all.

Edit: Added a "%" sign for clarity.

You missed the exponential.

Martel732 wrote:
You missed the exponential.

Alright, I'll come back in a few days and probably say you are right. Sorry. Ill respond when I don't have a 103 degree temperature : /

 Ryan_A wrote:
I was wondering if you guys thought a librarian with Gate of Infinity and Vortex of Doom belonged in a competitive CF list. I think it would be useful to use gate of infinity to toss a sternguard squad around the table to where they are needed and to avoid close combat. Do you guys think that is a good idea, or is it better to put those 140pts somewhere else?
Pedro Kantor- 175
Librarian with Terminator Armor and SS- 140
5 man tac squad, Drop Pod- 125
4 sniper scout, 1 M launcher and camo cloaks- 100
3 sniper scout, 1 M launcher and camo cloaks, telion- 150
Aegis Quad Gun- 100
3* 10 man sternguard squad, 5 combi melta, Drop Pod- 310
Skyhammer storm talon- 125
Total: 1850
Besides the obvious drop podding, pair up telion and his squad with the quad gun so they get 2+ cover save. Toss the other squad between the quad gun and where I am dropping the troops. Deploy storm talon sooner rather than later.
With the extra 140 pts I could get another 5 man and drop pod and have another 15 points for combi weapons.
What do you all think? Thanks in advance.

First in roughly 2 weeks 6th edition C:SM is coming out. Rumor is Stenguard are getting sightly cheaper, but combi weapons getting way more expensive. Telion and Pedro wont be able to be taken in the same list without allying two chapters together, which you could do but the different allies might not be able to start in the same drop pod. Drop pods are going to 10 models. Libbys are going to get cheaper but will have to roll on rulebook powers so you wont be able to ensure you get anything.

As many people have tried to explain. Heldrakes are meta changing. You can use all the math you like. If you cannot kill them with intercepter fire, they will kill one of your squads when they come on. If you cannot kill them in 1 turn, they will likely kill another squad the turn after that.
A storm talon is a good start, but remember that anything you can do to try and down the drake, a chaos player can do to try and down your stormtalon. Stormtalons being half as survivable as a drake and you have problems. 1 vector strike has a good chance of killing a storm talon(certainly better chance than a assault cannon, twin linked or not has of downing a drake), so hope you dont go first. Also your quadgun is manned by 2 squads of 4 men. Those can be killed and then the gun cannot fire, unless you bring a drop pod down to man it...

Now back to the question, yes a libby does have a place in a competitive CF army. They are great HQ choices, and getting cheaper is going to make them even better. I would wait till the dex comes out, unless you really want to play in the next 2 weeks and want advice for that small term.

In the mean time, You might want to change some of the sternguards combi meltas to combi plasmas. There is less and less armor out there but getting 2 shots instead of 1 is wonderful.

 Ryan_A wrote:

anonymou5 wrote:

 Ryan_A wrote:

anonymou5 wrote:
According to Mathhammer, 4 STR 6 TL Rending shots into AV 12 with a 5++

.0 Glances (obviously)
.395 pens
6.6% of exploding it

Keep in mind Pens 1-3 do basically nothing to a Drake 5/6 times....

Thanks for the first thing, but I really dont get the last thing you said. 2 pens on average have a higher chance to destroy anything rather than not, its bad form to calculate "luck" into math-hammering if indeed you meant that the first three pens dont do anything.If I misinterpreted you, sorry, still very sick.

Please don't tell me I'm using bad form if you don't understand what I'm saying. Heldrakes have the rule "Daemonic Possession" Which means they ignore Crew Shaken and Stunned Results on a D6 roll of 2+ That means when you pen, half the results are effectively just glances. Then, 1/3rd of the time he gets that HP back anyway (because Heldrakes also have the It Will Not Die Rule). I wasn't adding luck into math-hammering, I was adding a mathematical caveat to how ineffective a single AP - pen is to a Drake.

All that doesnt change the fact that the odds are after 2 pens the vehicle would be destroyed. Thanks for your info though.

Edit: what I mean is, you said " 1-3 do basically nothing to a Drake 5/6 times" which is pretty much the opposite of the truth. 3 pens have an extremely good chance to take the vehicle out of the game. Statistically, 2 pens will destroy any vehicle more likely than they wouldn't. And those who would prescribe to the statement that 5/6 times pens 1-3 dont do anything usually back up the claim with something like: "that has always been my experience," "I've never been able to destroy them with that much," "I blame bad rolls," etc.


Automatically Appended Next Post:
I realize I am kinda being a jerk and I know I keep using this excuse, I am really sick. But its true. Anyway, I do appreciate you guys helping, sorry for being so short.

I wasn't clear in my initial post, so I tried to clear it up a bit. I wasn't saying 3 pens do nothing, I was saying the pen results of 1-3 do nothing (because of Daemonic Possession)

You have a 6.6% chance of killing a Drake outright. You will do .395 pens, half of those pens are negated on a 2+ That's the TLDR version.

Also, that STR 7 Vector is bad news for a Storm Talon.

Basically, you are vastly underestimating the survivability of a Heldrake. You're running Marines, the Heldrake is an important part of the meta to consider.

Either way, to answer your question. A Librarian is a good choice.

Thanks for your guys info. I had a moment of clarity just now and instead of arguing when I am probably wrong I am going to show a sliver of intelligence and ask: "What should I do about helldrakes?" Given my army the only anti air I have is the quadgun and a skyhammer storm talon. Would you guys suggest switching the skyhammer to a TL lascannon for 15 pts or a typhoon for 20pts? Or perhaps taking another storm talon since my fast attack slots are open? Or do you guys think I should add in a storm raven for its stormstrike missiles and/or typhoon/Multi melta? Or something entirely different?

Or would you guys suggest something like, if I know they have a helldrake, to drop my pods out of the way and very far apart and smack the ADL quad gun in a position to intercept the helldrake on its way to the troops?

Thanks in advance!

ADL positioning will always be a good counter - if nothing else it may make the Heldrake deliberately target it early so you could even do worse than put it slightly to one side so you can position something else to shoot at it from behind.

Switching the Stormtalon out to a TL-lascannon sounds good, not just because of the Heldrake but other flyers too. It may only be one shot but it's a high chance to hit, then a 4+ will penetrate any flyer currently in the game (and is likely to stay that way). It's possible the assault cannon may be slightly more effective against AV10, mind, I don't have a mathhammer head on me at the moment.

If you have the points another Stormtalon could be useful, for two reasons. One is that, with their escort special rule (I assume they still have it in DftS and will in the new Codex?) means you can more or less pick and choose where and when they come on, making it that much easier to get at rear armour. The other is that, if you succeed in taking out other flyers and an ADL if there, you can then whizz the Stormtalons round and take advantage of that air superiority. I think that's something we forget about a lot here on the board, as opposed to on the table - if your flyer takes out other flyers you *can* still keep on using them!!

The assault cannon on the Stormtalon isn't BAD if you can get rear shots with the turret.

 Ryan_A wrote:
Thanks for your guys info. I had a moment of clarity just now and instead of arguing when I am probably wrong I am going to show a sliver of intelligence and ask: "What should I do about helldrakes?" Given my army the only anti air I have is the quadgun and a skyhammer storm talon. Would you guys suggest switching the skyhammer to a TL lascannon for 15 pts or a typhoon for 20pts? Or perhaps taking another storm talon since my fast attack slots are open? Or do you guys think I should add in a storm raven for its stormstrike missiles and/or typhoon/Multi melta? Or something entirely different?

Or would you guys suggest something like, if I know they have a helldrake, to drop my pods out of the way and very far apart and smack the ADL quad gun in a position to intercept the helldrake on its way to the troops?

Thanks in advance!

A storm raven is nice against heldrakes. The additional armor (and hull point?) help survive the mass str7 vector strikes AND it has better weaponry.
An icarus lascannon might be better against heldrakes(but worse against other flyers) as hull point stripping against IWND, 5++, AV12 is so difficult. The longer range also makes intercept more likely.

Terminators are the best thing against heldrakes as everything on the drake is AP3.

I might think about adding a TFC, if it's rules stay the same. CSM often have annoying cultists hiding somewhere, and you wouldnt want to bring sternguard down on top of them(overkill) Being able to kill those annoying 2+ cover save(when gtg) guys can end the game. You really dont want to be in a position where there are 2-3 drakes killing your army while 50 points of cultists hide in cover far away from your units. Kill them and you win.

I might consider taking only 20 sternguard in 2 drop pods to combat squad or 20 in 3 drop pods. Sternguard are of course great. Having them score is great. Them getting cheaper is great. But.... There is a lot of AP3 shooting from a lot of things that sternguard have trouble with. I think diversifying your army might make it more competitive.

The Stormraven and a quad gun maxes out at 2 helldrakes, if you roll well. For triple helldrake, you need another stormraven or storm talon support.

 Ryan_A wrote:

Martel732 wrote:

Automatically Appended Next Post:
Each AC hit has a .833 chance of NOT penetrating. Therefore, for 4 hits to NOT penetrate, it would be (.833)^4 or ~0.48. This means that the chance to penetrate at least once is (1-0.48) or 0.52.

However, there is the chance that the TL AC does not get all three hits. That drops the odds below 50/50.

That is incorrect.

4BS, twin linked, RENDING,

We will calculate for one shot, then multiply by four.
For one hit, it is a 4/6 chance, so .6 repeating, it is twin linked, so then you multiply the difference of .6 repeating and 1 by 4/6, which is .2 repeating. You then add .2 repeating and .6 repeating which gives you the chance of a BS4 Twin Linked shot to hit, which is .8 repeating (.8888888888). You then have a 1/6 chance to glance, so you multiply .8 repeating by 1/6 to get .148 repeating. But the shot is rending, so on a six you roll and get between 1 and 3 additional strength, so no matter what, you get the pen. You then multiply the chance to pen (since there is no chance to glance) by the number of shots (4) to get .592, which is your chance to pen (since you will never glance av12 with an assault cannon).

Please say if you still think I am wrong. I am very sick today and have stayed home all day so it is entirely likely I am missing something obvious.

Couple points on your math -

if you're trying to track the chance to score @ least 1 pen over 4 shots that have a ~15% chance each you'll do something like (.85^4). The number is slightly lower (closer to 52%, assuming your hit/armor save calcs were correct ***edit* they absolutely weren't, see below - I also added the drake's invuln***). Using your method, around 7 shots you would have ~ 100% chance to pen the 'drake which is impossible given the mechanics (for example one of the items in your table of results will be 1,1,1,1,1,1,1 to hit which would break your method).

I'm not sure where you're getting that method for calculating the to-hit roll for a TL BS4 weapon as well, your chance to miss is .3 repeating and .3 repeating of those will miss again, which means 10.89% (.333*.333) of BS4TL shots are misses, so (1/3*1/3) -1 gives you your hit chance of 89.11%

89.11% of those shots at a drake will bounce off of his 5+ invuln - .8911 x .66 = .588126, or approx. 59% of shots fired into this cruising helldrake will actually make you roll to penetrate it.

.59 x .16 = .0944 ie. 9.44% chance to pen a helldrake per BS4TL assault cannon shot. So we know now that 91.56% of shots into that helldrake don't do anything, and 9.44% of them will pen.

If you're shooting 4 shots, your chance to score 1 or more (up to 4) pens will be ((.9156^4) -1)= .298, essentially a 30% chance to score *one or more* pens vs the drake. Now 66% of results when you score a pen are going to make the drake functionally irrelevant (the immobilized one is up for debate depending on where the drake is on the table but let's assume for now it puts him out of the picture)

Now once you're on the table it's actually pretty lethal for the drake, such that an assault cannon volley has around a 18% chance to roll at least one destroyed result vs the drake even though it's only got around a 30% chance to do anything at all (a high percentage (50%) of successful results are also destroys) if you're just trying to destroy him or the baleflamer (more likely in actual play) then your odds are a little higher. If you factor locked velocity in as a dead drake too (up for debate certainly) then you're at around a 23% chance to knock the drake out per assault cannon volley, where the other 4/5 of the time you're rolling some combination of misses, crew stuns, and successful drake demon saves.

Hull points just add another dimension to this, where you take the results that are not destroys and count them as points (that the drake can regenerate) and figure out your odds of doing something close to 2 HP/turn to account for the regen. Bottom line is a single flyer is unlikely to effectively put a drake in the ground before it's done a considerable amount of damage to your army.

Possibilities to consider:
4 hits from TL AC
3 hits from TL AC
each hit is 88.9% likely, so this gives

(.889)^4 = 62.5% to get 4 hits
for sake of argument, 37.5% chance to get three hits since likelihood of getting 2 hits is very, very low

For each hit, there is an 83.3% chance of NOT penetrating.

4 hit case:
So the chances of getting at least one pen is 1-(.833)^4 = 51.9% chance.

However, a subset of this is the case where we get two pens, which is equal to getting one pen on three dice after getting an initial pen. This probability is equal to:

.166 (first pen) * (1-(.833)^3) = 7.0%

Note that this is a subset of the above situation, of getting at least one pen. So the approximate break down is
7% chance of getting two pens
45% chance of getting one pen (52-7)
48% chance of getting no pens (100-52)

However, note that this case is only 62.5% likely to occur. The math is worse for 3 hits.

3 hit case:
Chance for at least one pen: 1-(.833)^3= 42.2% chance

Chance for two pens: .1666* (1-(.833)^2) = 5.0% chance

So this breaks down to
5% chance for two pens
37% chance for one pen
58% chance for no pens

Also note that this does not take into account the demonic save. We'll get to that. The totality of pens per TL AC volley would be the weighted summation of the two cases:

((.07 * 2)+(.45 * 1)+(.48*0))*625+((.05*2)+(.37*1)+(.58*0))*.375 = (0.37+0.18) *.666 (demonic save) = 0.37 HP/volley

Now these are all pens, so half of them will have a useful effect: velocity locked, weapon destroyed, or explode. I'm not sold on velocity locking crippling the helldrake, so I'll go with .12 useful events on average per TL AC volley, 0.19 useful events if we count velocity locked.

So we see that it will take a Gaussian weighted average of nine TL AC volleys BS 4 to strip all the HPs in an single turn, or three TL AC volleys to have 50% chance to get a useful event. This is why I consider the TL AC a poor weapon against the helldrake.

anonymou5 wrote:

.0 Glances (obviously)
.395 pens
6.6% of exploding it
You have a 6.6% chance of killing a Drake outright.

Anonymou5 Your answer is right but your math is wrong.

I will try to explain how unlikely it is to 1 shot a heldrake with a twinlinked assault cannon

Each shot is independent
Each shot has a .0988 chance to pen. (8/9)*(1/6)*(2/3) Chance to hit, chance to pen, chance to go through the daemon save

Let's call the chance to pen, .0988 = P

Chance to get all 4 pens FO= P^4 = .000095
Chance to get only 3 pens TH= 4*(P-1)*P^3 = .0035 three pens*one miss*number of distinct combos that can miss.

Chance to get 3 or more pens is A= FO+TH =.0036

Now if you score less than 3 pens, you might destroy it. Each pen has a 1/6 chance to make the drake explode.

Chance of only 1 pen ON = 4*P*(P-1)^3 = .29
Chance of only 2 pens TW = 6*P^2*(P-1)^2 = .19

Chance of 1 pen exploding a heldrake OE = ON *(1/6) = .048
Chance of either of 2 pens exploding a heldrake = TE = TW * ((1/6)^2+2*(1/6)*(1-1/6))= .015

The chance to explode the drake without reducing it's hull points to zero is E= OE+TE = .063

SO the chance to one shot the drake is the chance to do 3 or more hull points plus the chance to make it explode when you dont take all it's hull points
D= A+E = .066

You have an 6.6% chance to 1 shot the drake with a twinlinked assault cannon.

Hah! Ninjaed you But I talked about "useful events" not outright explode. Either way, it's a miserable weapon against the helldrake.


Automatically Appended Next Post:
The case for the TL lascannon:

(.889) to hit *(.5) to pen * (.5) useful result on table * .667 (demon save) = 0.15 useful events or 0.20 useful events if you count velocity locked.

The lascannon inflicts (.889)*(.6667)*(.6667) = 0.4 HP a turn

I guess that's not incredibly better, but lascannon is also better against AV 13 and AV 14 ground targets. I guess it just shows that the helldrake is a tough nut to crack.

 Exergy wrote:

anonymou5 wrote:

.0 Glances (obviously)
.395 pens
6.6% of exploding it
You have a 6.6% chance of killing a Drake outright.

Anonymou5 Your answer is right but your math is wrong.

I will try to explain how unlikely it is to 1 shot a heldrake with a twinlinked assault cannon

Each shot is independent
Each shot has a .0988 chance to pen. (8/9)*(1/6)*(2/3) Chance to hit, chance to pen, chance to go through the daemon save

Let's call the chance to pen, .0988 = P

Chance to get all 4 pens FO= P^4 = .000095
Chance to get only 3 pens TH= 4*(P-1)*P^3 = .0035 three pens*one miss*number of distinct combos that can miss.

Chance to get 3 or more pens is A= FO+TH =.0036

Now if you score less than 3 pens, you might destroy it. Each pen has a 1/6 chance to make the drake explode.

Chance of only 1 pen ON = 4*P*(P-1)^3 = .29
Chance of only 2 pens TW = 6*P^2*(P-1)^2 = .19

Chance of 1 pen exploding a heldrake OE = ON *(1/6) = .048
Chance of either of 2 pens exploding a heldrake = TE = TW * ((1/6)^2+2*(1/6)*(1-1/6))= .015

The chance to explode the drake without reducing it's hull points to zero is E= OE+TE = .063

SO the chance to one shot the drake is the chance to do 3 or more hull points plus the chance to make it explode when you dont take all it's hull points
D= A+E = .066

You have an 6.6% chance to 1 shot the drake with a twinlinked assault cannon.

Haha, my math was actually correct, my language was wrong. I used the mathhammer site and got 6.6% chance to destroy (which includes hull pointing it out), but I said "exploded" because I'm an idiot. You guys could really save a ton of time:

http://mathhammer40k.com/shooting/armor

It's not always right, but it's always close (and almost always dead on really)

I prefer to go through the mental exercise myself. Besides, I can modify criteria on the fly doing my own math. Like as to whether locked velocity is a desirable outcome or not.

Martel732 wrote:
I prefer to go through the mental exercise myself. Besides, I can modify criteria on the fly doing my own math. Like as to whether locked velocity is a desirable outcome or not.

Fair enough. I'm just lazy I guess. Although I've gotten pretty good at doing rough math hammer in my head, if I want precision I use the website

No, the tool seems to be accurate. I mean these probabilities are trivial math problems for most computer scientists. Note that the TL MM on a stormraven has less than 25% chance of destroying the helldrake. Pretty depressing, really.

 Ryan_A wrote:
Thanks for your guys info. I had a moment of clarity just now and instead of arguing when I am probably wrong I am going to show a sliver of intelligence and ask: "What should I do about helldrakes?" Given my army the only anti air I have is the quadgun and a skyhammer storm talon. Would you guys suggest switching the skyhammer to a TL lascannon for 15 pts or a typhoon for 20pts? Or perhaps taking another storm talon since my fast attack slots are open? Or do you guys think I should add in a storm raven for its stormstrike missiles and/or typhoon/Multi melta? Or something entirely different?

Or would you guys suggest something like, if I know they have a helldrake, to drop my pods out of the way and very far apart and smack the ADL quad gun in a position to intercept the helldrake on its way to the troops?

Thanks in advance!

Frankly, outside of allies it's unlikely you're going to find a really cost-effective solution for heldrakes if you're drop-podding MEQ models onto the board. The new codex comes out soon anyway.

As an aside since there seems to be quite a few math heads here, what are the exact odds of a BS4 TL Assault Cannon popping the Drake in rear armour? Just wondering if you have better odds firing the TL AC and TML from a Talon into the front of the Drake or flying past it and firing the turrent TL AC into the back.