Pressure wash hull in water possible ?

[arch007]

I was wondering if it is possible to pressure wash a hull from the dock with the boat in the water ?

Something tells me no.

So why not ?

Thanks

[Lepke]

If you try to pressure wash under water, the water being much thicker than air, reduces the pressure. Maybe with the nozzle almost contacting the hull, but then you'd only do a small area.

[psk125]

Holding the nozzle from the dock and being able to see what you were working on would also be interesting to try to do.

[Rucksta]

Originally Posted by arch007

I was wondering if it is possible to pressure wash a hull from the dock with the boat in the water ?

Something tells me no.

So why not ?

Thanks

Interesting idea think, I'll give it a go when it stops raining here.

Can't see that water pressure due to depth is much of a factor.
A pressure washer operates at 800-1200psi for box store models.

Water pressure at 33' is 14.7 psi so the increase would be negligible at the bottom of the canoe body - additional 2 psi approx.

Distance of the working surface from the spray head would make a big difference just as it does when cleaning the driveway.

Maybe a wide fan nozzle mounted in something like the head of a vacuum cleaner floor attachment with a long curved handle for getting under the canoe body would work.

Probably be like mowing the lawn with a line trimmer blindfolded.

[arch007]

Please let me know the results of your experiments !

[ranger58sb]

There is at least one diver in our area that does it... but his apparatus isn't an off-the-shelf pressure washer, and he's down there with it when he's working...

-Chris

[fstbttms]

It’s a very bad idea. To overcome the resistance of the ambient water, the tip of the pressure washer nozzle (where the water pressure is maximum) must be held very close to the boat bottom. The result is that you are 100% guaranteed to blast paint off of the hull. A pressure washer should be used to clean unpainted metals only.

[Rblakenyc]

Originally Posted by Rucksta

Can't see that water pressure due to depth is much of a factor.

It's not water pressure from depth it's the pressure required to deliver a stream at sufficient velocity through the resistance of water rather than air.

Think about throwing a ball through air vs water or velocity of a dropped object through air vs water.

Not saying it won't work but no doubt will have lots less pressure delivered to the hull than your driveway unless super close - which then limits "spray zone"

[Rucksta]

Originally Posted by Rblakenyc

It's not water pressure from depth it's the pressure required to deliver a stream at sufficient velocity through the resistance of water rather than air.

Think about throwing a ball through air vs water or velocity of a dropped object through air vs water.

Not saying it won't work but no doubt will have lots less pressure delivered to the hull than your driveway unless super close - which then limits "spray zone"

Yes I am thinking about it and your input.

I tried the small Karcher in a 50 gal drum part filled with water.

The flow from the tip seems laminar for the first few inches.
Holding a gloved hand in front of the immersed flow at three inches indicated a similar pressure to gloved hand in air at five inches.

Velocity does fall off past three inches and is quickly lost in turbulence.

In air the laminar flow breaks down into a spray pattern within six inches.

So yes less effective in water.

At three inches poking a stick may be a better model than throwing a ball or dropping an object.

Not yet convinced enough to start fabricating heads and handles but curious to give it a test run on the boat next visit.

[fstbttms]

Originally Posted by Rucksta

...but curious to give it a test run on the boat next visit.

Apparently I am the only person here who has actually used a pressure washer to clean a hull in the water which means that every other reply is pure speculation. I am telling you that you will very likely damage your paint (and maybe your hull into the bargain) if you get a pressure washer close enough to it to actually clean off any fouling growth.

But hey, knock yourself out. It's your boat and your dime.

[Dave_S]

Originally Posted by fstbttms

Apparently I am the only person here who has actually used a pressure washer to clean a hull in the water which means that every other reply is pure speculation. I am telling you that you will very likely damage your paint (and maybe your hull into the bargain) if you get a pressure washer close enough to it to actually clean off any fouling growth.

But hey, knock yourself out. It's your boat and your dime.

I agree, I think you would need to have a very controlled distance from the hull or risk damage and the close distance would reduce the width of the fan from the blaster to such a small section you might be there for a long time.

[roverhi]

Tried it with my Ablative painted bottom. Managed to clean about 2' depth from the water line. With the turn of the bilge got to be nearly impossible to get the water jet to follow the hull curvature. Suppose if you had a nozzle that was angled to better direct the spray might have more success but don't think you'd ever get it to work without jumping in the water. If you are going to do that might as well just scrub the bottom by hand. Didn't have any problem with paint coming off and if you didn't look too deep the bottom looked squeaky clean.

[Cheechako]

Become a billionaire: Invent a Water Roomba that sucks itself to the hull, like a Remora, and squirts salt water jets on the surface as it moves around slowly.

"The Remoora"

[Dsanduril]

You mean like the Keel Crab?

https://www.youtube.com/watch?v=70U2JFkzHb8

[Cheechako]

Originally Posted by Dsanduril

You mean like the Keel Crab?

Damn! Too late again!