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[IanLloyd]

Is there a specific way of working out what angle a propshaft should be at? I see different boats have different angles and as I am scratch building at the moment I need to work out if it makes a big difference or not so I know what to do.
 
The trawler I have has an almost straight propshaft relative to the bottom of the hull whereas the MTB I have has a very sharply angled propshaft comparatively.
 
Does it affect performance or is it based on hull design?
 
Any help would be good thank you.

[triumphjon]

the best angle is as shallow as possible , the steeper the shaft the more the prop would like to push the bow into the water, rather than push the boat forwards !  where abnouts in hampshire are you ? jon

[NFMike]

With high powered/fast boats like the MTB the thrust from the prop is under the boat and thus below the centres of drag and gravity which means horizontal thrust tends to lift the bow. Having the prop angled helps to counter that.
With trawlers and other slower or larger ships that isn't an issue, so horizontal thrust for best efficiency is usually the aim.

[Bryan Young]

From past experience I've noticed that most fishing vessels (and tugs etc) have a hull that deepens towards the stern. With that in mind, I suggest you try to get your prop shaft as close as possible to be parallel with the waterline. BY.