Hairy bottom/ speed.

[miket]

Had a sea trial on a semi-displacement boat last week and had a very disappointing result. Best speed obtained 13 knots with manufacturer's max' at 25 knots.
Engines revved freely in neutral to the designed max'. I found it hard to believe that the difference could be accounted for by even the 12 months growth (SQ Southampton) admitted to by the owner.
Brokers were very good and offered to have the boat lifted and pressure washed (their or vendor's expense) and a 2nd trial set.
Wow!! What a difference. Straight up to 24.2kts and an easy cruise at 19kts.
I took photos of the hairy bottom. Mainly small barnacles and worms with some weed with the props, p brackets and rudders and shafts liberally coated.
Happy bunny and now proceeding to completion.

 

[burgundyben]

About right.

I got a year of growth 2 years ago, dropped by speed from 30 knots to 15 so its about what I would expect.

 

[ari]

Even worse on a full planing boat sometimes.

You can end up in a catch 22 where the growth stops the speed climbing to the point where the engine revs bring the turbos in to push onto the plane, and because the turbos won't come in there isn't the power to get on the plane so the speed won't build up.

So you end up stuck off boost and floundering along at 10 knots in a 30 knot boat!

 

[SeaDave]

Mine dropped from 32 to 18 knots. First day out since a scrub and re a/f tomorrow - can't wait to see how she goes.

 

[sk16]

It's bad!

Last week I took the boat out and only manged 11 knots at 4000rpm (mercruiser 350 MAG engine). Arranged a lift and wash next day. Went out and straight up to 25 knots no problem. It's only been 6 months since my last life and wash and I'm based at Eastbourne.

 

[Renegade_Master]

Had a sea trial on a semi-displacement boat last week


cmon do tell what is she?


I am currently looking into that ultra sound antifouling system

 

[powerskipper]

Clive

Had a sea trial on a semi-displacement boat last week


cmon do tell what is she?


I am currently looking into that ultra sound antifouling system

We have that fitted to the school boat at the mo, will let you know how it goes.

 

[Renegade_Master]

Hi Jules yes I heard that was the case, how long has it been on to date? or can you not tell me.

A lot of my customers out here are showing interest in this product, so I am looking for proven cases.

 

[powerskipper]

hi

Hi Jules yes I heard that was the case, how long has it been on to date? or can you not tell me.

A lot of my customers out here are showing interest in this product, so I am looking for proven cases.

Both the boys are away this weekend but will try get info on mon for you.