Cavitation

[Falcon]

I am still dicovering what my RIB can do but i have found i get allot of cavitation when trying to turn quickly, anybody got any tips.

[matiboy]

before you do anything

make sure your prop is in perfect condition, the only way to ensure this is to have it proff serviced or even consider a brand new one. Even if your prop looks ok it may still be knackered and causing the problem.

a stainless prop can be serviced for about 60 quid which is cheaper than 400 odd for a new one

I had this problem recently, not just in turns, rough water would cause cavitation even in a straight line.

Purchased a new 4 blade ally prop which cured the problem.( A 4 blade will give better grip and initial pull 7 on the flipside lose a bit of top end. ) This type of prop is usefull for skiing.

I then managed to pick up a brand new stainless & this is working superbly and is better for cruising.

Give the experts a call:

www.steeldevelopments.co.uk

If you are running commercially then a prop service should help to be more fuel efficient

Does it still cavitate in tight turns with an excessive amount of trim down which is sometimes required ?

[Falcon]

Thanks for your advice matiboy, the prop does have a nick out of the metal and so i will look into servicing it. I don't know what it is like at turning with allot of trim down, i'll try it. the prop Is a Stainless laser II.

[Jelly]

I realise this might be teaching your granny to suck eggs, but are you going into the turn with the power on? i.e. are you backing off a bit going in, then putting it back on in the turn to drive out.
might help
Jelly

[Brian]

On this subject, and combining it with the trim tabs thread, can anyone detail the best or correct procedure for.................

making a tight a turn as possible, at the best speed possible on a boat fitted with trim tabs (let's say a 180 degree turn back and assume calm sea).

[Julian]

Brian

If you want to make a very tight turn, approach at quite a high speed, begin the turn and trim the leg in a bit you can get the rib right up on its tube then back of the power and straighen her up. Oh and hang on coz there is a lot of force

Julian

[Scubakid]

If you want VERRY tight turns try a jet powered RIB if you are not bolted to the seat you will part company with the boat.

John

[Charles]

A bit like this......... power in to the turn, leg(s) trimmed right in, trim tabs fully up, off the power slightly as you commence the turn, and lots of power to bring you out again?

[Julian]

That's the one Charles, nice photo.

[Alan Priddy]

And for those of you with outdrives, attach a piece of string to the leg so you can fish it out of the water when the gimble housing goes bang and it falls off!!!! Alan P

[Manos]

What every body says in this thread is very wise and correct. However, what you do not say is HOW you attempt to make a tight turn. If you have full power and (even) just a bit of trim or even no trim and attempt a sharp turn the engine prop will cavitate.
Your best bet is to follow Julian's instructions, see what happens and tell us about it.

[jwalker]

It ain't necessarily so.

JW.

[Manos]

JW any further suggestions to avoid this effect and learn something more are very wellcome!!
I seriously mean that!!