My towels are hard after washing.

I don't notice the vinegar smell. I use it on sports kit too to get rid of the sweaty smells.
Must invest in some spiky balls!!

I love the smell of bed linen and towels when they have been dried outside on the washing line.

Aka just the mention of Jeyes fluid takes me back nearly about 55 years to my first job. Then we used it in the greenhouse for cleaning when my stepfather was alive.Is it still available?

Should have added that I agree, a short tumble is the only answer for towels.

Nearly about? must learn to preview!

Don't use any fabric softener on towels or they won't dry you properly. I use Tesco own bio liquid to wash them and chuck them in the tumble dryer.I appreciate that you can't do the same, but if the towels dry naturally instead they need to dry slowly, ie. hot sun will make them like boards.As somebody has said, a windy day is the best time to get washing dry.No easy answer.

Am I alone in liking a rough towel?

No, I like 'em rough! I don't like towels rinsed with fabric softener.

I dry mine on a airer in the spare room, and they are quite soft.

Could it be a build up of detergent? Could it be biological washing powder?

I use a small amount of non bio washing powder with a spoonful of old fashioned washing soda. Wilkinsons sell it at about £1 a bag. Lasts ages.
Line dry then finish off with 5 minutes in the tumbler. Never any problems. Never use fabric softener as haven't found it necessary.
Hope one of these replies will give you the answer. Good luck.

I've been thinking about throwing all my towels out and starting again.
It's good to know it isn;t just me. I only wish there was some way of solving this problem, I loathe and detest a hard towel.
The only thing I haven't tried is the spiky balls. And woudn;t you know it? My local Lakeland is closed this week.

We are hard water - i use Ariel Gel and fairy Conditioner, then dry on line, and whizz to fluff up in tumble dryer for 5 mins..

Your towels are drying hard because they still have skin on them i find if you rewash a couple of times more that should sort the problem out