Me or the boat thats wrong?

Tight Fart · 03 August 2005, 07:18

I have a small 4.5m Quicksilver RIB with a 50hp Johnson, however in a small swell say 3 foot + ish, if I open her up a bit to get on the plane the boat feels as if it's going to take off and roll. at say 15 to 20 knots it will hit a wave and start to turn as it lands it makes a movement back the otherway to right itself that's is quite violent.
Now is this me doing something wrong, the basic design of the RIB not liking any swell or what? I have only noticed this when it's only me in it and am unsure if it could be down to weight, but as the family won't go out at any sign of a wave it's hard to check.

Andy · 03 August 2005, 09:45

Changing the trim of your engine may help have you tried that

ollyit · 03 August 2005, 09:54

have you got dolefins attached to your outboard?

Tight Fart · 03 August 2005, 10:30

There are fins on the outboard, I haven't changed the trim, is that different to the tilt?

hannah · 03 August 2005, 10:37

i dont really no if this would help but are you hitting the wave square on ?
if we dont hit the wave square on in our boat , it tends to land lop sided

ADS · 03 August 2005, 14:38

Quote:

Originally Posted by Tight Fart

There are fins on the outboard, I haven't changed the trim, is that different to the tilt?

Get rid of the fins and then test it. Fins have their uses but they dont work on every application.

Alex

Tight Fart · 03 August 2005, 16:29

I will take them off at the weekend and give it a try.

Biggles · 03 August 2005, 16:30

Trim. In my opinion.

Tight Fart · 03 August 2005, 16:37

Can someone please explain the difference between trim and tilt

If I have been buzzing along flat out on still water I have adjusted the tilt and seen the speed change on the GPS, I don't think thats what you meen though.

ADS · 03 August 2005, 16:42

PTT (Power Trim and Tilt) enables you to control the angle of the engine when running at speed, using hydraulic rams, and operating from a control lever mounted switch.

Secondly, outboards have a tilt bar and a range of holes. This restricts how far the engine can go down and holds it at the required angle, although this is usually found on outboards without ptt.

Alex

ashbypower · 03 August 2005, 16:43

Engine Trim is the lower part of the tilt mechanism.
If you use the Trim/Tilt switch you notice it is 2 speed. The slower (close to virtical) is trim used to trim engine/boat. The faster is Tilt used to Tilt engine prior to beaching/recovering.

Trust this helps

Brian

Pete7 · 03 August 2005, 21:01

Quote:

Originally Posted by Tight Fart

Now is this me doing something wrong, the basic design of the RIB not liking any swell or what? I have only noticed this when it's only me in it and am unsure if it could be down to weight, but as the family won't go out at any sign of a wave it's hard to check.

If you heading into a 3 foot swell in a 4,5m rib at 20 knots then it is going to go airborne big time. How it lands can depend on the torque from the prop, balance of the boat and the distribution of weight in the boat, offset of the engine and the angle of the wave to name a few.

I suggest you keep the engine trimmed in going into the waves and trimmed out going with the waves but also dip the revs as you touch the wave so the boat floats over the wave not fly off the top. Power can go back on almost instantly to keep the momentum going.

Pete

Tight Fart · 04 August 2005, 07:38

Thanks for all the replies, I have a lot to learn and I think some tuition is in order. I have never noticed 2 speed in the tilt action and will have a look at the weekend, The throttle response would not allow me to adjust engine speeds over the rise of a wave.
So tilt and trim are the same thing (ish) Tilt lifts the engine out and trim is a finer adjustment off engine angle?
I know it's going to get air bourne but I thought it should pretty much glide over a small swell at 20 knots. Its the way it takes off and lands that's scary.

Biggles · 04 August 2005, 08:07

Quote:

Originally Posted by Tight Fart

Thanks for all the replies, I have a lot to learn and I think some tuition is in order. I have never noticed 2 speed in the tilt action and will have a look at the weekend, The throttle response would not allow me to adjust engine speeds over the rise of a wave.
So tilt and trim are the same thing (ish) Tilt lifts the engine out and trim is a finer adjustment off engine angle?
I know it's going to get air bourne but I thought it should pretty much glide over a small swell at 20 knots. Its the way it takes off and lands that's scary.

Hi Mate,

If the throttle response won't let you adjust speed over the wave then you might be over propped.

Bill S · 04 August 2005, 09:11

Hi TF,

I think you just need a little bit more experience with your boat in differering sea states (no offence meant - just my tuppence worth). I have a wee 4 metre boat with a 40 hp on the back - flat out speed is 31 knots on gps (flat calm, solo, fully trimmed out), so our rigs are similar. Any wave action reduces that performance considerably - not that the boat isn't capable - its a matter of comfort and safety. In the type of swell you mention (3ft) I am probably doing just over 20 knots, but backing off just before cresting the wave, then power on again to drive down and up the next one. It ends up being a very smooth rolling action - and keeps airtime and slamming to a minimum. I nornally keep the motor trimmed in in anything other than a flat calm - in my wee boat it doesnt make that much difference except in flat calms. The boat behaves well like this, and my ears are saved the verbal abuse from the missus sitting on the pillion! The frequency of the swell (space between waves) is also critical, as closer, steeper waves are not as easy as longer, spaced out ones. Having said all this, I don't get it right all the time, and sometimes get caught out by a wave, and find myself airborne big time, complete with big slam back down. It isn't comfortable, sometimes the boat gets a bit skew-whiff too - the solution is in your throttle hand - ease off a bit! Like I said at the top - I think you just need to get more used to handling your own rig in different conditions. I have also tried doel fins on my outboard, but found the boat behaved better without them, so took them back off.
Of course every now and then I get to pretend I'm young again, and I'll blat round flat out jumping every wave in sight. You still need to exercise throttle control just before takeoff, or the boat lands every which way. This generally doesn't last too long 'cos its tiring and I eventually scare myself too much on a bad landing, so the red mist clears and I back off a bit again. Just enjoy what you have, and as you get more in tune with your own rig you will find your own limits and be confident within them.

Bill