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[boat captain]

On lifeboats what is the best water pump to simulate the water discharge through  the exhaust pipes?   Looking on websites most pumps are not constant running ones.

[craggle]

Was driving home from work today thinking, I'll ask that exact question later this week as I need some water to bubble out the exhausts on my Severn.
Will watch for the replies.   


Cheers, Craig.

[MAC]

Not bought one myself but considering getting this unit for my Tamar http://shop.huntersystems.co.uk/simulated-engine-water-coolant-pump-2612-p.asp
Be interested to know if anyone has any experience with it.

[g6swj]

What are the characteristics of the water flow from a lifeboat exhaust -  Does more flow when the boat goes faster?

I know the behaviour well of the exhaust/water output of my river boat - does anybody have a video/YouTube link of say a Severn?

Jonathan

[craggle]

Just found this video with somewhat repetitive singing!!!

Mute it and head to about 5 minutes into the film and you can see the boat coming into dock. The exhausts do seem to blow more water out of them when the engine revs are increased so maybe another speed control is needed for the pump but then you wouldn't want it to stop completely when you are not moving either?

https://www.youtube.com/watch?v=Ign90jvYdws

Craig.

[g6swj]

Craig,

I'll blame you if I can't sleep tonight with those lyrics going round in my mind.

I'm sure there must be some other guys who know the facts on this forum - it does look like the water is forced out quicker when the engine revs - no doubt with faster exhaust gases but the volume doesn't seem to change that much - or at least that's my take.

Would be interesting to know - I think this behaviour would be fairly easy to simulate - I have a couple of Servern's so would be interested to work on a solution (unfortunately one with sealed exhaust flaps which I have looked at several times trying to work out how I could unseal them) - it would be really neat to get the water out with significant air as well so you get the white foaming effect - hmmmm....

Jonathan

[Robin smith]

I didn't think water came out of the exhausts thought it came out of the pipes Which are adjacent to the exhaust and are elbowed down ....then I am a country boy !!!

[craggle]

Apparently the angled pipes above and to the sides of the exhausts were engine crankcase breathers. I say were as the boats have had an engine change since being built, Catapillar engines to MTU engines now I think and the engines breath differently.
According to Alan (17-09) the starboard pipe is now a drain port for a deck well and the port pipe fitting has been removed and replaced with a blank disc.
I'll post a picture later when I find one.

Craig.

[craggle]

Here we are, one of my photos of the Newhaven boat. Port side pipe fitting is a now a blank plate.   



Craig.

[mersey dave]

Don't know if it would work as this is just my thought, if you had a water pump connected up to a speed controller via a Y lead to the throttle channel my thinking is the faster you go the more power to the pump.....more water.....slower less water.
Like I say just my thought.

Regards Dave.

[g6swj]

My river boat has got this type of silencer which I think causes the cyclic spluttering of exhaust water/no water/ spluttering effect

Do lifeboats have something similar? Appreciate we are talking about 2 very different vessels - but do lifeboats "splutter" water on tickover?

Here's an explanation as to how the silencer works

Well-designed exhaust systems collect exhaust gases from the engine and discharge them as quickly and silently as possible. How does a typical Waterlock or Lift-Silencer work? As the mixture of seawater and exhaust gas enters the inlet connection, the water level rises in the tank. As the water level rises, the water surface gradually reduces the gas flow area entering the discharge pipe. The reduced area for gas flow causes a great increase in gas velocity and reduction of noise. The high speed of the gases, entering the outlet pipe, divides the water. The "mist" created by this process is transported to the highest elevation of the exhaust piping. The volume of the Waterlock or Lift-Silencer tank should allow ample accumulation of the return water once the engine is stopped.

[Delboy1958]

Hi Guys
My mate lifeboat Paul on his Aran used water scoops behind the props connected to the outlets and a Y
connector to put smoke through the exhaust mixed with the water.

Hope this helps

Derek

[me3]

Hi,

I work at the RNLI and can confirm the faster the engine revs the more water comes out. The type of silencer that g6swj mentions is what my old man has on his boat. The water fills a trap, when it is full it ejects the water, hence the disturbed flow of water, it comes out in burst. Lifeboats don't have these water traps so the flow is constant. The exhausts are straight through. Also, with a petrol model that I built, I have exhaust tubes that are about 100mm long and water is injected straight into the middle of the diameter. By the time the water gets to the end it 'rolls' out of the tubes like a lifeboat would...something to bear in mind rather than having a jet of water out the back.
So  hopefully that helps a little bit   
Hopefully got a picture to show the effect of the water too..

If you scroll down on my topic you can see what I mean, the smaller 6mm tube is for the water. http://www.modelboatmayhem.co.uk/forum/index.php/topic,52184.0.html

[captain bligh]

Hi all
Just came across this topic last night,we went for an engine run today and I took a couple of videos on my phone of the exhaust.lf any help to anyone PM me and I'll email them to you.Oops sorry was on a Severn class.

Mike