Boat wash

[Sibfun]

I took my 3.8 mercury inflatable out on the Thames today and kept getting shouted at for creating to much wash.
I was not speeding and doing about 4 knots if I go any slower I’m going to stop.
Two adults in the boat no baggage.
How do I stop this and is it a trim problem?
Any advice.

[Poly]

Option 1: slow down. Were you going upstream? If so 4 knots over ground will be quite a bit more through the water.
Option 2: speed up - I’m assuming there is a speed limit so this isn’t an option but often the wash will be less if you can properly get on the plane. This may not be safe even if it is legal, and may upset others anyway.
Option 3 adjust the the trim (engine angle and weight distribution).

If you are making a big wash you are just burning fuel to make waves so you might as well do 3 knots and use 1/2 the fuel.

[Poly]

Oh, and to answer properly we would probably need a video...

[Mikefule]

Wash or wake is a function of the speed of the boat through the water, and the shape of the boat in the water. A boat that is truly on the plane will make very little wash. A boat that is almost but not quite on the plane will make loads of wash. A boat that is sitting bow up will make a lot of wash, as will one where the bow is too low.

You need to adjust the trim of the boat so that it sits at a nice angle. You may find that adjusting the trim of the motor will help, but most of all, try redistributing the weight of crew and cargo.

Wake only really matters when you are near to other water users or there is a risk of causing erosion to banks, or disrupting wildlife. It is good manners to slow down for other water users, especially open canoes, and to give them a wide berth.

If you really were doing only 4 kts through the water in a boat of that size, anyone who complained was probably being a bit precious.

[Fenlander]

>>> doing about 4 knots

We use our 3.8m SIB on the river a fair bit where the flow is minimal. At a true exact 4kts on the GPS there is minimal wake but the increase in wake as we creep up to 5kts is surprisingly out of all proportion to the small speed increase and enough to annoy folks and anti-social.

If as Poly hints there could be a fair flow on the river and your speed through the water was actually 5kts or more then I'm not surprised if your wake was excessive... SIBs are lumpy inefficient things to push through the water.

[GuyC]

Originally Posted by Fenlander

SIBs are lumpy inefficient things to push through the water.

Particularly when you leave the beaching wheels down

[Fenlander]

So far I've only experienced that dropping the wheels at a pontoon on purpose and then motoring a short distance to the slip... certainly very draggy.

[Mikefule]

Originally Posted by GuyC

Particularly when you leave the beaching wheels down

Don't ask me how I know, I just do, OK...

[Locozodiac]

Try : trim motor to 90 deg (fully vertical) distribute deck load evenly, throttle enough for Sib to run fully parallel against the water level, achieves best prop thrust angle of attack, least lower hull drag along minimum wake, betters fuel consumption.

When possible, go full wot as indicated on flat calm water cond and check if there's back or even over transom water splashes, indication that motor sits too low and will produce unwanted larger rear wakes. In such scenario will need to wooden shim motor up on transom untill the back splash is fully canceled out.

Happy Boating

[jeffstevens763@g]

Who was complaining fisherman?

[paintman]

If you put the engine in neutral - leave it running - & drifted along with the current you'll likely find some that will claim you are creating too much wash.