The Steamboating Forum

Jon,
I could have used one of these on a project a couple of years ago. Anything I could find was many $$$ more.

You mentioned the use of some form of induction scoop to move water through the condenser. Are you looking at that with the pump to be used at low speed? The Destroyers all had circ pumps that were started under a given speed to maintain flow through the condenser. There were check valves on both lines keeping water for backing out the intake instead of going through the condenser. If you're planning on going with a pump only, forget what I just said.

I like the idea of the onboard condenser, it just feels a little more ship like. On the other hand my dad had a keel cooler on his boat in Alaska made of two bronze tubes tucked in close to the keel. It looked similar to the one shown earlier. In the twenty years that he had the boat it was never a problem, even with intentional beachings to change the prop or get net out of the wheel. Simplicity has its virtue.

Good luck

Dave

It's almost as though there are two schools of steam launch design. Both are fun and rewarding.

One is to duplicate efficient big boat practice as much as makes any sense at all. Lots of pumps and squeezing every bit of propulsion from each BTU of fuel. The more gauges and valves the better. A mechanical engineers dream hobby boat.

The other ends right about at "The African Queen". A 'boiler thing' that converts some sort of flammable substance to steaminess. Often closer to a hot day in the tropics than 'real' steam. Another lump with a few more moving parts that works at converting the muggy stuff in the boiler to rotation. Continues to run in spite of many sarcastic comments directed at it and little serious maintenance.

Personally, I love to look at 'properly engineered' power plants. I stand in awe as the responsible party lubricates everything and reads the various gauges. I think Wes called it Steam Porn. But then I realize that most of my passengers are more interested in the fact that the boat is quiet except when I let them blow the whistle. They do not appreciate a well mannered feed water pump.

So my boat hovers a bit on the simple side of the median. I add things that will reduce fuel consumption but am not that interested in fussing. I rig things so that I can pretty much make any sort of mistake and it will either make the safety blow or slow the boat to a crawl.

So please do post pictures and tell me if it works. That's what I'm on here for. To learn from both the mishaps and triumphs of other people.

Mike

Lopez Mike wrote:It's almost as though there are two schools of steam launch design. Both are fun and rewarding.


Mike

Only two???

I think I've got the wrong forum!

Regarding the condensing section of a boat steam plant, onboard condensers have been very appealing to me, especially after the plate-type heat exchangers became available to a very moderate price (I got 2 identical ones on eBay for less than $ 120).

The specifications of these exchangers amply exceed the requirements for a steam plant. Compared to a keel condenser plant, the resulting layout by using a heat exchanger is extremely simple. By locating 2 exchangers one on top of the other, the top one can work as feed water pre-heater whereas the bottom one is the condenser. If properly placed, the condensate flows by gravity into the hot well. This very compact unit can be cared for any time, no need to take the boat out of the water. Due to the rugged design of these exchangers, the risk of contaminating the feed water with cooling salt water is practically nil.

One of course needs the corresponding cooling water pump which – at best – can be driven from the engine shaft. The best available type for this purpose is the so called roller pump (Hypro offers a wide range, the smallest one being good suited for most of the usual boat sizes). As these pumps reverse the flow direction when going astern, some kind of "rectifier bridge" – consisting of 4 non-return valves – is sometimes used. I decided to go "KISS" and do without the valves. By placing the cooling water outlet well below the floatation line, the pump establishes the flow the other way around through the condenser.

In some steam plants, a vacuum pump is not even necessary (e.g. single cylinder, twin cylinder).

If for corrosion or efficiency reasons the hot well temperature becomes an issue, the inboard-condenser plant allows for a simple means of adjusting the temperature to any desired value: just regulate the cooling water flow with a valve in the discharge side.

These pictures show the layout on "Min Deern":





Albert

Hi Albert,

That is a very neat looking setup. I have considered the plate type heat exhangers, but was not sure if they would be big enough etc. Can you tell me how you decided what size exchangers to use ?

jon

Hi Jon,

If I remember well, I started with the recommended condenser surface as a function of the boiler heating area. Then, I decided how many plates the exchanger of a given size should have. For their volume, these pieces have a huge exchange area. Stainless, operating pressure well above the usual boiler one.

Let me take a look at my records or to check the actual dimensions of both exchangers. Please tell me the kind of engine you are operating. By comparing its size with the twin Pearl it should be an easy task to arrive to the correct exchanger size. On my boat, the condensate flowing into the hotwell is just hand warm.

Albert

Hi Albert,

I am running a 3x4 single, just a basic ~ 5hp engine.

jon

Hi Jon,

Your engine has a little less displacement than my twin Pearl, however it sure runs at a higher speed. Thus, the size of my heat exchangers would easily keep up with your engine. Here is the technical data:

Dimensions: 191 x 73 x 87 mm
Connections: 4 x 3/4"
30 plates, effective surface: 0.36 m²
Working pressure: 30 bar
Working temperature: up to 200 °C
Flow: 4 m³/h
Weight 1400 g

Sorry for the metric data...

Albert

Hi Albert,

No problem on the measurements.........I had another concern when I was considering this option. Is there a lot of back pressure ? I have read that putting any restriction in the exhaust loop can affect performance and rob power. I am not going to be pulling any water skiers, but was nervous about what ill effects it might have.

Jon

P.S. - It would be great to see a picture of your engine boiler set up. I am thinking about moving some things around and am looking for ideas.

Hi Jon,

You don't need to be concerned about back pressure. Immediately behind the inlet connection, the steam flow is divided into 15 parallel paths. Back pressure is just a fraction of the one caused by any keel-condenser layout.

I personally like a layout which results in the shortest possible length of steam and water lines (no lines running a couple of times back and forth...). In my case: no lines ahead of the boiler; boiler; hotwell close to the boiler, pre-heater/condenser unit on top of the hotwell; feed water pump to the left, cooling water pump to the right; engine; hand pump to the left of the engine; no lines abaft of the engine. Take a look at the pictures I posted in my introduction. Please ask if you need some more detailed ones.

Albert