I am going to put everything about delaying into here.
I will do what I can. Please contribute to make it the best.
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(1) What.
Each nation provide a different set of crew title combination. Some nation got a chief repairman, some a chief engineer; some got a sq leader fighter, some a sq leader bomber. We used to delay carrier pilot, however, ability calculation changed after some patches, making it obsolute. Now, people delay for a better repair ability or lighter crew, at the same time trying to make sure everything alse the same.
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(2) When and Fact.
Fact first:
I: 8 delayed engineers overheat longer than 5 normal engineers, however, move slower in WAW mode.
II: They only work as a whole, so, if your BB1-2 in clan war give you only 5 slot, sorry your crews are useless. However, the BB1-2 may run faster depend on the kind of ship.
III: Expert gain rate will be lower.
IV: It need more vet than normal, however vet conversaion rate is lower.
V: It assumed you boosted everything.
VI: If you delay engineer, you should not have repairman onboard.
VII: you can sell them alone hardly, no one will buy it.
When should I delay:
I: torpedoman for SS6, not the slim skeleton torp on DD.
II: always delay Operator to any level if you can.
(let's say BB3 have a typical range of 34, your gunline at lvl is 30,let's say, you cannot see it.
If you delay your BO, your gunline may be 29. So tell me, what's the difference?
You shoot with feelings!)
III: USA, UK, IJN AA gunner do not reach reload cap on normal class.
(Optional for KM AA gunner ifyou want accuracy on it.)
IV: HH gunner on Carrier.
Optional case when I consider delaying:
I: try to make light weighted crew so a list of big ship move 1knt faster
H39, Kasier, Project 24.
II: try to get 11.0 inch of armor and above on QV, with a reasonable OH duration.
III: try to create stupid combination to play.
When you should not delay class:
I: I find that my BB3 is easy to die
II: I find that my BB3 move slower when crew level up.
III: I know that SN & KM bad in repair ability, it seems not enough even with repairman.
IV: People said sonar and planesman will reach ability cap soon.
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(3) Cost and risk
Risk:
well if CCP collapse, you become one of the dude crying, or,
if new patch included ask you to have repairman independently
Cost:
expert pack after 300% event. With normal crew, I will grind the expert back from gameplay. However with delayed crew, vet & exp are your life.
Although it may not cost you more money, your time is a must.
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(4) How
I: Typical:
start with 4 elite rep 8 11/x/12, and 2 ghost sailor.
make them 2 armement, 1 sailor, 1 special force, 8 support.
Class them at least after 100 levels as gunner, BO, rookie, engineer.
II: cheap guy half delaying:
start with all non-elite sailors.
Get them 2 armement, 1 sailor, 1 rookie, 10 support.
Class them at 70-79 lvl as gunner(cheif/huge anything), BO, rookie.
keep 8 support as 2nd engineer, keep 2 supports for HH
No one delay engineer when they have repairman.
No one delay sonar & planesman
why?
firstly, I can't reach planesman cap(4.6M TA).
Second, it is easy for sonar to reach cap only under water.
If you put sonar on carrier(likely PCV or CV5/CV6), you need 3.6M TA and above.
If someone need proof, it will be a whole new topic.
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(5) Comparasion