How to rule helms ?

[Selion]

The "dented helm" feat states the following : "When a critical hit is confirmed against you, as an immediate action, you can apply half of the damage from the attack to your helmet rather than yourself, applying hardness as normal. If the damage destroys your helmet, any leftover damage is applied to you."
I cannot find anything about how many hp an helmet has and what penalties a broken helmet would bring . The player that may take this feat has a +2 adamantine full plate. I would say that the helm is 1/10 inch thick, so it should have 4 hp if non magical. After the enchantment bonus it would have 24 hp, and finally the adamantine special quality would raise this value to 36 hp ( 1 and an half hp bonus). Am i wrong?
What would happen with a broken helm? Would the ac of the full plate set be lowered by something?

[paranoidbox]

I've never seen any real game-mechanical rules for helmets, though I would love some :D Where is this from?

[Selion]

The feat is from "trascendent 10, company of dwarves" http://www.d20pfsrd.com/feats/racial-feats/dented-helmet-combat-dwarf

[Psyren]

The "dented helm" feat states the following : "When a critical hit is confirmed against you, as an immediate action, you can apply half of the damage from the attack to your helmet rather than yourself, applying hardness as normal. If the damage destroys your helmet, any leftover damage is applied to you."
I cannot find anything about how many hp an helmet has and what penalties a broken helmet would bring . The player that may take this feat has a +2 adamantine full plate. I would say that the helm is 1/10 inch thick, so it should have 4 hp if non magical. After the enchantment bonus it would have 24 hp, and finally the adamantine special quality would raise this value to 36 hp ( 1 and an half hp bonus). Am i wrong?
What would happen with a broken helm? Would the ac of the full plate set be lowered by something?

If the helm is broken (which means "gains the broken condition," not that the helm itself is unusable), the only mechanical impact is that you can't use this feat with it anymore. It shouldn't lower the AC of the armor as a whole, because the helm doesn't affect the armor class of the suit any more than the boots and gauntlets do. All can be swapped for various wondrous items without changing the wearer's AC after all.

[Uncle Pine]

A quick search on the pfsrd tells me that a helmet is actually a type of weapon (http://www.d20pfsrd.com/equipment---final/weapons/weapon-descriptions/helmet-dwarven-boulder).

[Red Fel]

I cannot find anything about how many hp an helmet has and what penalties a broken helmet would bring . The player that may take this feat has a +2 adamantine full plate. I would say that the helm is 1/10 inch thick, so it should have 4 hp if non magical. After the enchantment bonus it would have 24 hp, and finally the adamantine special quality would raise this value to 36 hp ( 1 and an half hp bonus). Am i wrong?

Well, according to this table (http://www.d20pfsrd.com/equipment---final/damaging-objects#table-armor-weapon-shield-hardness-hp), the HP of armor is 5x its armor bonus, +10 for each +1. So full plate gives +9, which means 9x5 = 45 HP, and it's +2, so we add +20 to that. It has, to my calculation, a total of 65 HP. Adamantine adds a hardness of 20.

When you were looking at HP based on thickness, I assume you were looking at this table (http://www.d20pfsrd.com/equipment---final/damaging-objects#table-substance-hardness-and-hp), which to my knowledge refers to materials in their unworked state, as opposed to being in a finished product such as a suit of armor. I don't think that table applies here.


What would happen with a broken helm? Would the ac of the full plate set be lowered by something?

I think it's as Psyren says. It doesn't hinder the armor itself, it merely prevents you from using the feat until you're wearing a non-broken helmet.

[Necroticplague]

Normally, helmets don't offer a benefit. However, that feat (and its prereq), make helmets provide a benefit. A broken helm wouldn't provide these.

[Psyren]

A quick search on the pfsrd tells me that a helmet is actually a type of weapon (http://www.d20pfsrd.com/equipment---final/weapons/weapon-descriptions/helmet-dwarven-boulder).

That helmet is a weapon, yes.

[Selion]

Well, according to this table (http://www.d20pfsrd.com/equipment---final/damaging-objects#table-armor-weapon-shield-hardness-hp), the HP of armor is 5x its armor bonus, +10 for each +1. So full plate gives +9, which means 9x5 = 45 HP, and it's +2, so we add +20 to that. It has, to my calculation, a total of 65 HP. Adamantine adds a hardness of 20.

When you were looking at HP based on thickness, I assume you were looking at this table (http://www.d20pfsrd.com/equipment---final/damaging-objects#table-substance-hardness-and-hp), which to my knowledge refers to materials in their unworked state, as opposed to being in a finished product such as a suit of armor. I don't think that table applies here.


Ok, so the helmet has the same hp as the whole plate?
By the way, adamantine armors have one third more hp (i don't know if the bonus hps have to be calculated before the enhancment bonus hps or after)

[Flickerdart]

A helmet is roughly the size of a gauntlet. A gauntlet is a light weapon, and light weapons are 2 categories smaller than their wielder. Therefore, a helmet should have 1/4 of the HP of the suit of armour that it belongs to.

[Edenbeast]

You could use the rules for Piecemeal Armor, from Ultimate Combat:
http://paizo.com/pathfinderRPG/prd/ultimateCombat/variants/piecemealArmor.html

Even if you're not using Peacemeal, you could use it for this specific case.

If you need to determine the hardness and hit points for a single armor piece, it has the hardness of its main material and hit points equal to its armor bonus (treat as +1 for armor pieces with a +0 armor bonus) × 5.
Which actually is the same as the basic rule for damaging armor..
But then if the enemy tries to hit your head, it will have the same hp as the rest of your body as well. Unless you're using hit locations like in warhammer fantasy/40k.