Slow running

[Whitelighter]

Went out with a group of friends today across tot the folly. It ws a bit rough, but nothing to bad and I was going with the tide though into a moderate sea.

It is the first time I have had more than 4 on board (8 this time) and I filled the tank to the brim befor we left. Coming out of Chichester did my usual and gunned the throttle but the boat wouldnt go above about 3200rpm and wouldnt plane.

By throttling all the way open I finally manged to get her to plane but she was running very slowly compared to the last few runs. I had a look at the props befor we left and they had a fair bit of muck on them, but the boat was only launched 10 weeks ago so I would imagine the bottom is not to dirty (it is antifouled). It did free up on the run home but still needed a lot more throttle to plane than has been the norm.

Is this likely to be the extra weight of 4 bods, dirty props/hull or should I worry and look a bit deeper?

 

[tcm]

i wd gues that that 4 extra bmw-ish midrange sized people wd indeed be significant in 28footer, and rough waves aso slow the boat. And, i also reckon that that there cd be a bit of gunk underthae boat, tho theweight is more significant. Run off the water if you can in the uk - the water is free and they have it everywhere...

 

[ballena]

Its all about weight distribution, the engines on these american boats represents a huge percentage of the overall weight, go stick 6 or 8 bodies right on top of it and the stern will not lift out. The only answer is to trim the nose down until on the plane.

if you think that each V8 and drive weighs about 1/2 tonne, mounted as far aft as possible, this makes centre of gravity low but well aft, when the boat is trying to get on the plane, there is a natural point at which the hull breaks free and an angle of attack, the further back that the C of G is, then the greater the angle of attack so by putting more weight forward this will balance things out a little.

 

[capnjack]

Jez,
I am sorry to say but IMHO, I think it may not have been the 8 people that caused your problem.

If you would like to PM me with your e-mail addy, I'll explain why.

Cap'n Jack

 

[tcm]

oi cap\'n!

aw, do tell us here.

Surely the weight of a full load of fuel and eight people wil make a difference on a 28footer?

Incidentally jez, there is likely a limit on the number of persons that the boat is ok for at sea or "rated for" - but dunno how many that is for your boat...legally anyway, it is definitely definitely not more than "12 plus crew" but some rcd rating wotsit mite well be a lower number...

 

[Wiggo]

[ QUOTE ]
Its all about weight distribution, the engines on these american boats represents a huge percentage of the overall weight, go stick 6 or 8 bodies right on top of it and the stern will not lift out. The only answer is to trim the nose down until on the plane.


[/ QUOTE ]

And I'll bet everyone was trying to sit right at the back, too. If this happens again, stuff a few of them in the cabin as you open the throttles, and let 'em back out once she's planing.

 

[MedDreamer]

Believe it or not the 285 is rated category B for 10 people (if I remember rightly). Just shows what a farce the RCD is.

The way the seating is arranged on the 285 doesn't help either, if you have eight on board then at least 2 and probably 3 people will be sat on the aft bench directly above the engine. Also with that number of people on board, all of them except the helmsman will be sat on the centreline or to port, and from personal (unpleasant - nay frightening) experience if you try and plane with this loading you will get a very nasty chinewalk and trying to correct with trimtabs requires a very experienced skipper.

I would just accept that if you are carrying so many people then displacement speed is the order of the day.


I would love to know what the secret issue is, perhaps someone would let us know.


Martyn

 

[MedDreamer]

I think in this respect the fuel and water tanks are pretty well placed on the 285. The fuel tank is low down centre midships, and the water tank is in the forward bilge.

In the engine bay, there is a bit of imbalance in that the heavy ancillaries ie batteries, hot water tank are to port - with only the holding tank to starboard - and if you don't use the on-board toilet this will be just an empty plastic tank. This imbalance only worsens the problem of the seating arrangement that I referred to in my previous post.

 

[Its_Only_Money]

[ QUOTE ]
It did free up on the run home but still needed a lot more throttle to plane than has been the norm.

[/ QUOTE ]

No doubt the weight of petrol burnt off was not compensated for by the liquid intake of the crew so the boat would be lighter....did you use the tabs to get her up on plane?