First splash, first (almost) sinking

[smacksman]

Exhaust hose is very, very stiff. 2" dia. hose will turn at about 2 foot radius!
Water injection does kill the noise but a muffler or lift box is better.
Running at tickover is much quieter than 2500 rpm.

[kerrye]

I ran across this which claims a muffler isn't necessary. The guy appears to know what he is talking about.

http://www.yachtsurvey.com/exhaust_risers.htm

"Personally, I do not like water lift mufflers because they cause too much back pressure, among other things.There often isn't enough space to install them correctly. If a system is designed right, it doesn't need a muffler as the water in the hose will accomplish all necessary muffling."

[kerrye]

Here's an image of a looped 2" exhaust hose in a sailboat locker. I think I could make a similar loop at the transom. One thing to consider with a loop like this, is that the length of hose filled with water up to the top of the loop from the engine is substantial. Will that water run back down into the engine when the engine is shut off? I can't see why it wouldn't. So how to solve that problem?

http://www.bristol27.com/projects/exhaust-system

[smacksman]

Well Mr. Pascoe doesn't like water lift mufflers so that creates a lot of problems if the engine is low in the boat.
Never use a loop or swan neck or a transom riser without a water lift box as water will get back to the engine.
If the top of the exhaust riser on the engine is well above waterline then yes, a fall aft should do ok. I would put a flap on the transom fitting to stop high waves pushing too much water up the exhaust when the engine is off.

[DesertAlbin736]

I've slept on it and had more thoughts.

You must have tossed & turned all night thinking about this & got up early, since your first post this morning was time stamped at 6:26 AM. I'd be pretty damn rattled too if my boat almost sank the first time out after all the work you've done. Not sure if that time stamp denotes your local time or my computer's time, since we're both on Mountain Time, but AZ stays on MST & doesn't do daylight savings, so we're an hour behind Denver during summer months. I'd only reiterate that having a valve to close off the exhaust through hull in such an emergency would not be a bad idea. A flap functioning as a check valve might to the trick too. Good idea about routing the raw water intake to the bilge though. Except for the exhaust fumes coming out of the broken muffler. Of course I imagine it's kind of hard to come up with MacGyver solutions like that on the fly when water is gushing into your boat through a 2 1/2" hose, at what, 50 to 100 GPM?.

Kind of like the Titanic's officer of the deck trying to decide which option had the best chance of survival, turning the ship in time to miss the 'berg and risk scraping the hull and ripping open six watertight compartments or ramming the iceberg head on and crumpling the bow but only flooding the first one or two watertight compartments.

[kerrye]

What is the material of your ball valve? I see some stainless 2" ball valves available. I still can't imagine a good place for a water lift muffler so I think I'm going to have to stay with something similar to the original unless someone can give me a better idea. I will add a ball valve under the quarter berth I think. What is the brand of your muffler? A person needs a relatively small one to fit in the space where the original elastomuffler was located.

[DesertAlbin736]

Hi Kerry,

You know I haven't really paid all that much attention to that valve, only to note that it's there & works. Probably s/s-bronze, but I'd have to look again to see. Maybe it's Marelon? Can't recall right offhand. Whatever the case, use bronze or Marelon, not brass. Our muffler is a Vernalift brand inline, as shown in the photo I added in the above post. I think we've talked about that before, haven't we?

Maybe this could be your ticket for replacement, available from Defender at +/- $215 depending on size/model?

The Vernalift muffler was designed originally for small auxiliary propulsion engines installed near or below the water line in sailboats.

muffler.jpg

http://www.defender.com/product.jsp?pat ... id=1248544

I think the part number on the one in our boat, #1300209, may be obsolete, the manufacture date is 1992. Besides, you're running a 42 HP engine compared to our 24 HP, so you might need something different. Maybe your muffler was just under sized for that engine?

T minus 5 days & counting to departure bound for Desolation Sound.

[kerrye]

Just ran across this. What do people think of installing this under the aft berth. I can't find the diameter of it yet but it looks like it might fit there.

http://www.defender.com/product.jsp?pat ... id=2051557

[kerrye]

Actually, I think this one may be better. It shows the diameter as 4 1/3 inches. I'll have to measure the depth of the area under the aft berth. It looks like it has enough capacity to capture any water from a loop at the transom. There's 3.7 liters of liquid in 6 ft of 2" hose

http://www.defender.com/product.jsp?pat ... id=2026305

[Beta Don]

I think one problem with not having a water-lift muffler as close to the engine as possible is that if you try starting the engine and it doesn't fire right up, you don't have that couple gallon 'bucket' for the water coming out of the engine to fall into and you risk back flooding the engine with seawater. The last one you linked to only holds 3 liters. The muffler also provides a 'water lock' which prevents water from the exhaust outlet on the stern from back flooding the engine. It's a critical piece of gear IMO. I would buy the recommended size muffler and install it as close to the engine as possible - The size of the muffler should be determined by the size of the hose running to it from the engine. I would guess the muffler on my A27 holds about 2 or 3 gallons. I sure wouldn't run my boat without one . . . . 'saving' a few bucks there might prove to be a huge mistake

Kind of like the Titanic's officer of the deck trying to decide which option had the best chance of survival, turning the ship in time to miss the 'berg and risk scraping the hull and ripping open six watertight compartments or ramming the iceberg head on and crumpling the bow but only flooding the first one or two watertight compartments.

I have always thought the reason they hit the iceberg is because they put the engines in full astern as soon as they sighted the berg. If they had left the engines in full ahead, the rudders would have been much more functional and simply steering away from the berg they probably would have missed it. Every skipper worth his salt knows that the rudder works much better with the thrust of the props working on it. I have no idea if this was addressed in the accident investigation or not, but I would imagine it had to have been mentioned at some point

Don

[kerrye]

The issue is that the A25 has no good place to put a water lift muffler next to the engine. It's not a question of saving $$. The A25 never had a water lift muffler from new. I plan to measure the height of my exhaust manifold above the waterline tomorrow, but I assume the designer of the A25 thought water would simply flow from the engine into the lake without backing up into the engine. It must actually do that otherwise there'd be lots of reports of waterlocked A25's on here. But since the exhaust hose is below the waterline for much of it's length, any breach with the thru hull below water will result in flooding the boat even if water can't enter the engine cylinders. So what I'm really looking for is a waterlift muffler to catch the water in the loop I want to put at the transom. A looped exhaust hose is somewhat preferable to me over a ball valve since the loop is always operational without having to activate it. Although the original system is preferable on the issue of accumulated water draining back into the engine. It can't happen with the original design so maybe the original design with a ball valve is better than a high loop system since you don't have to worry about engine waterlocking.

[kerrye]

As I've been thinking about this topic, I've realized that the low exhaust thru-hull on the A25 isn't just because of the aft berth, it's because of the slope necessary to keep water from backing up into the engine. So the picture I posted of the raised thru hull outlet earlier in this thread, is dangerous unless it also includes a water lift muffler because that raised outlet also raised the level of water in the exhaust hose at the exhaust manifold.

[DesertAlbin736]

I have always thought the reason they hit the iceberg is because they put the engines in full astern as soon as they sighted the berg. If they had left the engines in full ahead, the rudders would have been much more functional and simply steering away from the berg they probably would have missed it. Every skipper worth his salt knows that the rudder works much better with the thrust of the props working on it. I have no idea if this was addressed in the accident investigation or not, but I would imagine it had to have been mentioned at some point

Don

This could start another whole thread over on the General Discussion page.

There were several factors involved with Titanic's First Officer Murdoch's prior experience that led him to make what turned out to be the wrong decisions. The correct decision, in line with your suggestion, might have seemed counter intuitive to him at the time. None of which were negligent or faulty. First, the Titanic didn't really break any really new ground in contemporary ship design other than sheer size and having three engines & propellers instead of one or two (Cunard's Mauretania had four, but it was built for speed). Conventional clipper style stern, single skeg hung rudder, not much different than our Albin boats, except there were three propellers instead of one. Increasing the scale of size up from the typical liners of the era from 10,000 tons up to 46,000, they did not add additional rudders or increase the relative size of the single rudder beyond the proportions of earlier ships due to other design factors. It could have been that Murdoch figured that throwing everything into reverse he could stop the ship in time, or at least slowed done and still have steerage, which might have worked with a smaller ship. With the center prop stopped he lost propeller wash but would have still had some steerage flow, just not enough

One innovation with the Titanic was to add a Parsons direct drive steam turbine for the smaller center propeller which ran off low pressure steam exhausted from the other two reciprocating engines. Problem with that was, it could not be run in reverse, only forward. That was a huge drawback, since it not only stopped providing prop wash, it actually created drag and decreased the effectiveness of steerage way. The two outboard engines were very conventional triple expansion reciprocating steam engines. So when Murdoch used the standard maneuver of "Full Astern", the center engine had to be stopped, losing prop wash effect on the rudder. That was mistake number one. Mistake number two was running at 21 knots on a moonless night on a dead calm sea, where lookouts could barely make out the horizon, let alone a looming iceberg. That was Captain Smith's fault, since he'd received iceberg warnings from other ships all that day. Not only that, there had been a sudden drop in temperature, an indication that ice could be ahead. And as luck would have it, in the confusion of getting ready for the maiden voyage on a new ship, no binoculars could be found for the lookouts.

So in the event, when the lookouts did see & report the iceberg, the ship was only 37 seconds from impact. You can imagine there would have been some lag between turning the wheel "hard a-starboard" (they were using the archaic term of "starboard helm" in terms pushing a tiller to starboard to turn the ship to port) and the 78 feet tall, 101 ton rudder actually moving. I don't know, but it could be that Murdoch had been used to sailing on smaller single screw ships, so in a panic did not think of leaving the center prop in forward and port engine full astern and starboard engine full. Even in that case I'm not sure they would not have to shut down the center turbine to run even one engine astern. In any case, the time of getting at least one engine slowed to a stop before it could be spooled up in reverse wouldn't leave much room for error, and with 21 knots of momentum there would not be a whole lot of turning the ship could do in that short of time. Murdoch was attempting to "port around" the iceberg & later put the helm hard over to attempt to kick the stern around. Bad luck that there was a "spur" of ice sticking out below the iceberg's water line. Just putting the helm hard over without trying to slow down could have been a career ending move. He could hear the bosses second guessing, "Why did you do a sharp turn without trying to slow down? Passengers are complaining that you woke them up and knocked them out of bed!

[JT48348]

**squelch**

"Car 59: we have a 211 in progress at Broadway & Mainstreet. Hijacking in progress. Use extreme caution."



**squelch**

"Car 59 responding"

[WillieC]

I think I have hijack tendencies myself. Kerry has started a new thread which I will be following closely. These A25 should be sinking like an October Dow Jones and they are not, so there is something good in the original design. I just splashed mine then read Kerry's original post...what else have i forgotten! His research and tenacity are inspiring, as are ALL the relevant posts.