How bad will semi-sloppy windings affect transformer performance

I've recently began winding a transformer for a small ballast circuit. How bad will semi sloppy windings affect performance?
(Pics below)

That is not going to be measurably worse than the neatest possible windings.

Is it 50 - 60 Hz, or much higher frequencies? You can get away with a lot at mains frequencies. Have a look at the modification that I did here:-

https://www.electro-tech-online.com/threads/kef-psw2500-active-base-unit-repair.159244/#post-1380354 where some mains frequency windings are far from neat.

It depends entirely what you are trying to wind and you didn't tell us that ?
Sloppy cropping of the pic too

fourtytwo said:

It depends entirely what you are trying to wind and you didn't tell us that ?
Sloppy cropping of the pic too

Click to expand...

I'm trying to wind a small transformer for a mercury vapor ballast.

Mercury vapor ballast use saturable transformers and the secret sauce is in the steel core.
Or more specifically, the width and location of the air gaps.
The steel laminations are not your normal E-I cores. They are very special stampings with a particular steel grade.
The sloppy windings are the least of your worries.

schmitt trigger said:

Mercury vapor ballast use saturable transformers and the secret sauce is in the steel core.
Or more specifically, the width and location of the air gaps.
The steel laminations are not your normal E-I cores. They are very special stampings with a particular steel grade.
The sloppy windings are the least of your worries.

Click to expand...

I'm making a custom transformer with some e cores and a small air gap

This is a fet gate drive circuit, or a forward transformer, or flyback type transformer or current sense transformer?
If you want good coupling you should space coils evenly across the bobbin.
Also use interleave winding.
Also beware having turns too near a big gap due to fringing field heating.
Avoid too may layers of single core as you get skin effect and proximity loss.
Use litz wire if its high frequency.

actually... that bobbin is probably thick enough to avoid "fringing fields"...remember the field strength of magnetic fields is an inverse square of the distance.... most of the field lines are in the gap... commercial switching transformers do just fine with single core wire for the most part. if i were the OP i would build a simple winding machine that's hand operated... "scramble winding" (or as the OP said "messy winding") a transformer by hand without a winding machine makes for a winding that may be too bulky to get all of the wire on the bobbin, that's why machines are used to get nice neat layers.... interleave winding is very difficult to do without a machine specifically made for the purpose, and also will end up with a much bulkier winding.... i've only seen interleave winding done on things like 455khz and low HF (below 5Mhz) coils and transformers... and they're usually done with litz wire. look at the construction of TV fluorescent backlight transformers, they all use single core wire.

I see now that the thread starter is attempting to design a HF ballast.

The steel cored ballast I mentioned is for power line frequencies.

schmitt trigger said:

I see now that the thread starter is attempting to design a HF ballast.

The steel cored ballast I mentioned is for power line frequencies.

Click to expand...

yeah the ballast will run at 15-20 khz

opampsmoker said:

This is a fet gate drive circuit, or a forward transformer, or flyback type transformer or current sense transformer?
If you want good coupling you should space coils evenly across the bobbin.
Also use interleave winding.
Also beware having turns too near a big gap due to fringing field heating.
Avoid too may layers of single core as you get skin effect and proximity loss.
Use litz wire if its high frequency.

Click to expand...

It will be running off of a royer push-pull oscillator.