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familyman
14-04-2005, 03:17 AM
Ok this is for all you seasoned boat drivers out there.
I recently went out around half tide rocks on easter sunday with a 2-3m se swell running -very sloppy as the swell bounces back of the rock wall of the channel .The only other route was to go outside of the channel up onto the flats with only 1.5 m of water and increased roughness of swell.
The question I am getting to is the boat better off ie more stable if it is driven at slow planing speeds or should you back off and into displacement mode?
The boat is a 4.6 sportsman craft halfcab with 115merc .The problem is with this power the boat goes from 5kn to 15 kn with no in between. :P
It may be just boat driving experience as no one else seemed to be having a problem with the conditiions. ???
Everyones opinions would be appreciated ;D

ps the half tide rocks reference is for central coast nsw residents ;)
cheers jon

Rusty_Hook
14-04-2005, 04:19 AM
I think any ride in a 2-3m or a rough 1.5m swell would be pretty tough going in a 4.6 rig. It comes back to your personal comfort and those riding on your boat. I usually take it easier for the sake of my passengers, but just on the plane would probably be ok with backing off for those swells/waves that stand up more.

I normally try & keep on the plane, but I usually find that in those conditions I have my hand on the throttle and I am constantly throttling off & accelerating depending on what's coming up next. Hard to say if on the plane or displacement is better without knowing your boat.

Either way sounds like crap conditions.

finga64
14-04-2005, 05:02 AM
What ever feels the safest to you.
If somebody tells you to do 20kn and you poo your pants or worse that's too fast and if somebody tells you to do 5kn and you fall asleep that's too slow.
Personally I tend on towards the slow side, but I have all day to get somewhere and I hate pounding the boat. Things usually break when you pound them :'(
Might be a good oportunity the check out why there is no between 5-15 kn speeds??

cooky
14-04-2005, 05:11 AM
good post. Being pretty new to boating I'm just trying to figure out what is best myself. one night trip was rough chop and I was just going slow in displacement mode (comfortable, but I got impatient after about 30 mins so I planted it to about 40km/h and scary, but actually worked out better - hitting the top of chop - hit the occassional wall (lucky for grab handles), but overall my preference.

I'm actually okay with going fast and getting airborne occassionally (rough ride), but I do worry about passengers sometimes - so I usually adjust the ride to their preferences.

familyman
14-04-2005, 06:52 AM
I was by myself on this occasion ,had I had passengers I probably would have opted for not going out and staying in the bay.The motor takes alot of controlling to get it to sit at 2100rpm otherwise it will just take off.The downside to 2100rpm is that the motor is thirsty as at this speed.It may be that I will have to not go out in these conditions :-[ or maybe a bigger boat or 4banger is in order ;D ;)
Either way I'm thinking that it comes down to confidence and knowing your rig.Oh well ,MORE time in the boat,how sad ;)
cheers jon

basserman
14-04-2005, 07:17 AM
i have a 115 on a 5.3 cuddly and the flys along in the river also great outside but i do slow down out there are there is a diffent 2 foot chop :-X
however would love to have a spin in your 4.6 with a 115banger on the back! must be a real hoot on flat waters ;D

gunna
14-04-2005, 07:23 AM
I would be more concerned that you were thinking of getting onto the shallow flats with that sort of swell coming through. You would know that waves break right across those flats. Stay in the deeper channel and potter along. With that sort of slop you need to be careful that you maintain a speed that avoids the nose descending into the oncoming wave. That brings into play the distance between the waves too - which will dictate your speed. The same sort of thing happens around West Head at times and real slow is the only answer.

mini696
14-04-2005, 08:03 AM
Its the usual story of "it depends".

I usually sit as fast as I can to be comfortable. Usually this means being on the plane just fast enough to keep the bow up for the next wave. Too slow and the bow dips into the trough and the ride becomes a lot bumpier.

If it gets too rough I slow right down (5 knots or less).

Going too fast is very dangerous if the bow digs in and turns the boat (happens a lot running with the swell) you can be thrown over and the boat will just keep on going.

As I said just above. The general rule I go by is to keep the bow lifting from one wave to the next.

Mick

dfox
14-04-2005, 12:18 PM
Jon- your boat seems to jump from 5knotts to 15 maybe due to the prop your using, as a general rule in rough seas its best to have a semi plaining hull, it keeps the bow high and the boat more controlable. I would suggest that you fiddle with a number of things to achieve a craft with better bottom end performance.
Youve obviously got plenty of power, but what good is that to you if its not where you need it. Without seeing or driving the boat i can only make guesses of what to try but start by adjusting prop, engine hieght, wieght distribution and possiably a foil to get the boat plaining at lower speeds in calm water.
The better you can get this low down performance the better your boat will handle in the rough stuff...foxy

familyman
14-04-2005, 03:38 PM
I think the boat was /is set up for skiing as there were NO rod holders when I bought it-fixed that quick smart ;)
the boat will actually plane down to about 10 knots but you have to slow down to this speed not build up to it.The other thing is that it takes very fine throttle control to hold the right revs.Any way i'll have to experiment with it :)
And yeah basserman its a ball in smooth water- 35kn at 4200rpm
:o
cheers jon

dfox
14-04-2005, 03:53 PM
Jon- 35kn at 4200 says it all mate, she's deffently not set up for rough water handling, play around with it, i'll take a guess and say your prop is something like a 21 pitch you may need something more like a 17...