High speed turn with 9m. rib

[Fjordrafting]

I took the boat out of water today and drained the hull for aproxemately 400 l. of water, and there still is a lot of water on the sides which wount come out. Can this have something to do with the problems doing thigt turns?

[jwalker]

Originally Posted by Fjordrafting

I took the boat out of water today and drained the hull for aproxemately 400 l. of water, and there still is a lot of water on the sides which wount come out.

How on earth do you get 400lts of water into the hull?

That's about 400kgs moving around inside.

[tim griffin]

probably the main cause but its alot of guess work from every one at the moment FJORD questions that need to asked are what is your hull deep vee or less what is your props
have you tried bringing the trim in, bit by bit to see how much you need to trim down before the boat behaves as you want, trim tabs could be your answer and most probably will be but unless you experiment with trimming in
how are you going to know, its not a straight forward answer to a question , i throw the 6.5 into hard lock at 50mph trimmed in even in Solent chop (rib ex) and the 6.9 behaves the same trimmed in but trimming is a feel
thing that you have to experiment with and get the feel for your boat its not a hard and fast rule apart from the basics.of head sea and following sea, after that you have got to play and get the feel for your boat.
sorry still not helping much but give it a go and let us know how you go
regards tim
www.griffmarineservices.co.uk

[Fjordrafting]

Originally Posted by tim griffin

what is your hull deep vee or less what is your props

www.griffmarineservices.co.uk

It is deep, 24 degrees at transom, and I use 24" four blade Hydromotive.
The boat is a 8.75 Scorpion.

[tim griffin]

does it come with trim tabs as standard, reason is most of them do now,
once you get the water out, try trimming in bit by bit as you play throwing the boat into tight turns if you have trim tabs set the engines to middle or less and start using these again bit by bit to see how this effects the boat
by the way start of at a more sedate speed ie 20 knots see how she behaves
by the trimming/tabs if she responds better then increase speed to see if any changes you will need to do this in a variety of sea conditions and experiment alot, i notice she is new what size did you have before you got this one, still not helping i know but let us know if things improve
regards tim
www.griffmarineservices.co.uk

[Mikey]

I agree with Tim's comments.

For reference, we have also used 4 blade hydromotives on our boat.
They are very sensitive if the engines are low in the water .. much better with the engines higher. They will definitely both put the bow down by default and bow steer if you trim right in on a turn. Trim tabs can help to correct this but are not essential.

Combination of trimming right in, your props, lots of water in the boat and a tight turn would cause the problem if you turned too tightly.

Worth setting your trim to level and then running the boat to see if you are still nose down. If so, a little cupping on the props will solve this. Then turns should be taken at level trim or slightly trimmed in from level, but not right in. If the engines are low, trim tabs will help also ... by default set level with the hull ... then adjust as Tim suggests if you can or if you have a co-driver... not essential tho.

You should then be able to take reasonable turns at speed ... we round bouys when racing at 60-70mph for 90degree turns ... not for u-turns obviously

[Jonny Fuller]

Before you can make any judgments on the handling, you must get ALL the water out of any compartments on the boat.

And frankly, all this talk about what the boat should do at "exactly this trim", or "that trim", and with "this prop", is bollix!, it's like saying, " well my boat is white and blue, and it handles like this!, and yours is white and blue too, so it should be the same" !!
Every boat is a unique comination, depending on hull design, engine, engine/drive height and position, C of G, and many other variables, so you cant generalise.

Why not phone Scorpion and ask them, or find another person with the exact same boat/motor setup. he with first hand knowledge, could assist far more than a load of guessing.

BUT GET THE WATER OUT FIRST!

[gtflash]

i agree 100% jonny. in any kind of chop my boat will begin to cavitate with less than half trim so for me to trim down to level would infact be triming up!!

im sure jelly would be more than happy to help.... and out of interest when i went on the 8.1m stepped scorpion at ribex i didnt see him touch the trim when i was scrabbling to find a hand hold on corners at 56knts!