Slow Moving Problem

[codprawn]

Have you checked the trim tab/anode on the outboard leg?

[shirehorse]

It is set one click to starboard i assumed this was to combat the effect of prop inertia Codprawn, one thing i do is run fully trimmed down is this correct?.

[9D280]

Trim tab - yeah, that's a fair summary. It will however have negligible effect at the speeds you're talking about. As said earlier in the thead, best thing for a long slow cruise is to use small wheel movements and soon you'll find out just how slowly the boat responds. Overcorrection just exaggerateds the problem. I did a cruise with an aux a while ago to basically give it some excersise & blast the spiders out the exhaust . Reaction times using the main engine as a rudder .... 10+ seconds! (doesn't sound a lot untill you are steering a boat!) Even without the "vectored thrust" of the main engine prop, small wheel movements were all that was needed.

I'll need to hand you over to someone with PTT for the trim question. I'm still on manuial trim, so it gets set for the sea conditions before I launch - I just have to put up with where I set it for the fast stuff.

[jyasaki]

Originally Posted by codprawn

Have you checked the trim tab/anode on the outboard leg?

Trim tab is to counter prop torque at higher power settings. Won't have much effect at idle speeds. In any case, since it's attached to the outboard, it will steer the boat in the same manner that the lower leg cross section acts as a rudder, so you can pretty much rule that out as a fix.

jky

[PeterM]

Does it not just come down to the physics of 'stuff moving through any fluid' ? Its a while since I did serious fluid dynamics , but the best analagy is a paper plane - drop it and its all over the place ( no forward speed ) , throw it & it goes pretty straight ( it has forward speed) .

In a boat at low speed it has not much energy, so will react to 'any' sideways/any force loads, when going quick the energy is vast (speed is greatly increased) so it wont really notice prop torque/ wind/ minor waves etc any where near as much .

Isnt that why all boats 'wonder' at low speed ? Similar idea to running across a current/ cross wind. The faster you go the less it will affect you over all ?

especially 'light' boats like ribs that are really designed to run at displacement speeds ?

[shirehorse]

Thank you Blackroady that is a very good answer and one i have been waiting for, the answer i was after was all ribs wonder at trolling speed now i feel happy that my boat is as good as anyone else,s. Either people are reluctant to say there boat wonders or are so used to doing those short movements they do not notice it.

[Nos4r2]

Originally Posted by shirehorse

or are so used to doing those short movements they do not notice it.

Probably closer to the truth.

[Searider]

Parents used to have a 32' deep V boat on the Thames at Reading. 6 knots max speed most of the time. We found that it would wander a bit, as you have described.

It was a little more directionally stable with trim tabs down and power trim as far in as possible. I guess that pressing the bow down a little helped.

As others have said - steering "feel" will come with practice.

[Apherel]

A useful tip for low speed work, is to think of the boat as sliding in the water - the deeper the v, the less it will tend to slide.

Also helps with planning approaches and departures to jetties / obstacles if you think of setting up the approach so you can slide the stern to where you want it.