Details on Steeple Compound from Mosquitoe Enterprises?

[stevey_frac]

Hi Guys,

I was searching around... as I normally do on a Saturday morning, and came across the aforementioned engine from Mosquito Enterprises. It can be found here. The claim of 14 hp for it seems very high for an engine of that size. And she definitely seems reasonably priced, although if I had to guess that price is 10 years old.

Can anyone offer any insights, or problem with putting that engine in a Reliable Steam Salty hull?

Thanks,
Steve

[Edward]

Dear stevey_frac ,

Although 14 hp seems high it's not a ridiculous claim . It's certainly much more than enough for a 20'hull .
The footprint isn't too big either but it is heavy and although you don't need all 14 hp you're still going to need quite a large boiler .
The Reliable Steam website doesn't give the depth of the Salty hull (ie from Gun'l to keel) . This wouldn't matter if the hull is finished as a tug with an enclosed engine room but the engine might look rather tall in an open launch Salty , though that would obviously be a subjective opinion .
I think it would be do-able but the engine is on the high and heavy side of perfect . I suggest you work out what the steam requirements would be to run with an output of about 5-6 hp and therefore what size boiler you would need . Then when you know the size of the whole plant you will get a better idea of whether it would be practical .

Regards Edward .

[stevey_frac]

Hi Edward, Thank you for your input.

I do note that the 14hp claim is at 250 PSI, which is higher then I would intend. I'm kinda of wanting to err on the side of more power then less for the little tug, as I do intend to finish her as a tug and it would be fun to have the power available to do a bit of tug-ing!. I would also rather have a bigger engine turning slower. The engine would be dropped as low as is reasonable to keep her center of gravity low. Thus you would probably step down into the engine room a fair bit.

One thing i'm unsure of however, is that finished as a tug, i'm almost certain it would take 2 people to run her, unless somehow you could contrive a way for me, sitting in the pilothouse, to manipulate the controls of the boiler. Although i suppose it's not unreasonable to have some sort of mechanically linked throttle, and bring up the gauge readings to the pilot house. This would only require you to go back to the boiler room to stoke the boiler. Actually, thinking about it, you could just make the boiler room and pilothouse a single 'building' have the boiler 'facing' forward, and be able to stoke it from there with the engine further aft.

I think the next reasonable step is to buy the Salty plans, and try to do up a layout that would work.

For the boiler, I want to get in touch with the owner of the SL Alba which has a woodfired mono-tube boiler he designed that works fairly well and scale it up to be around 10 hp worth. Monotube boilers are light, and pretty small for their output, and fairly efficient to i'm led to understand. This does tend towards fairly superheated steam so injecting oil is a must.

You can read about the woodfired monotube boiler here.

[Edward]

Hello Again ,

I quite understand your point about going for a bit more power than perhaps needed and in itself it's not a bad idea . Do however check on the maximum prop size that the Salty can accept .
There is absolutely no point in pushing more power into the prop than it can transmit , all that will happen is that you'll get cavitation , more or less the marine equivalent of wheelspin in a car . Increasing the pitch can help , but only up to a certain point. There's a bit about that somewhere in this forum but I can't find it anywhere .
If your engine and boiler put out more than the prop can transmit you will just be carrying around excess weight and bulk which cannot do any useful work .

I know very little about monotube boilers other than that they are very sensitive to feed rate and heat input .
For this reason most applications , at least in the UK , have been either gas or oil fired as you can then control the fire quickly .
There was one coal fired monotube launch in the UK until fairly recently , but I seem to remember that its owner spent more time putting out fires that had taken hold of his hull than feeding and controlling fire in the boiler . Don't want to put you off , ......just thought I'd mention it .
I think that since you can't control the heat very precisely with solid fuel you need to be able to over feed the boiler with water and have some form of relief valve for this hot water . But as I say I know V V little about monotubes . I believe they can work well if you make the right incantations as you sacrifice black chickens at midnight on a crossroads at the full moon . (Very like injectors in that respect.)

Regards Edward .

[farmerden]

I can attest to the engine and boiler in the "Mosquito" as I have been on several runs with Dan and Marion However I think you should consider both their engine and boiler as they are a matched pair. To put in simpler terms ,if you have a 427 ci engine and put a single barrel carb on it the performance might be a tad under what you might expect.The same goes for steam,if you look at the boiler as being a carburator then no matter how many horsepower the engine is rated for it will only produce the amount of steam horsepower that the boiler can produce. And although a little reserve in the boiler is OK you don't want the safetys blowing off all the time when your little engine is pounding it's innards out! Get the specs on that hull -that will tell you how many horsepower you need. The horsepower needed to exceed hull speed goes up dramatically as does fuel consumption.[/img]

[stevey_frac]

Edward,

I believe the solid fuel fired monotube of which you speak is in fact the SL Alba, as he mentions that his wooden lagging had a terrible tendency of catching fire!

His method, as i understand it, was basically to run as much water through the boiler as was required to keep the water temperature at the outlet reasonable. You would then vent the excess steam to the condenser, if it wasn't required. He purposefully built more boiler then he needed, with the intention of venting excess. One thing about the mono tube he created however, is that it is prone to having very very superheated steam.

There is a book published by the name of 'Experimental Flash Steam' by Benson and Rayman that goes into all manner of detail about designing and building a monotube boiler. In one section, he details an experiment performed whereby he was able to produce 60lbs /hr of superheated steam out of a monotube boiler that had a heating surface of just .5 sq ft. In this example, the boiler was not operating efficiently and being forced very hard.

I'd like to model a boiler after the Doble steam car monotube, except have it be wood fired.

Getting back to the steeple compound, Farmerden, Can you give me any more details on it?

[artemis]

Gazillion answers follow:
1. I've known Dan Martin and Mosquito since 1962. I did the website design for Mosquito Enterprises back in 1999, but have done few updates as Dan has supplied me with few updates.
2. To get the stats on Mosquito go to http://www.northweststeamsociety.org/Pa ... SSBmos.htm
3. Mosquito Enterprises now also makes a fore-and-aft compound of that engine. The tandem was first built to save space. Still does. They also make a 55 sq.ft. VFT boiler to ASME code (good just about anywhere in the world).

All of the above said, the Mosquito engine is way toooooo large for Salty

4. I strongly suggest that you get in touch with Rob Christensen at http://www.rogersmachine.net/Steamboat.html - he's a nice guy and will be only too happy to communicate and share. He's located in Rupert, ID. He might be willing to part with the engine he was originally going to use.
5. Salty's plans call for a 5HP compound, 6HP double simple, or 7HP triple, depending on what you make her out of and how much you plan to really "tugboat". She draws 24.5" and displaces 6800#. Aside from Reliable's engines (which are good quality castings and very "sturdy") there are many other companies that manufacture engines in that range of HP. A good listing can be found on the "links" page of the International Steamboat Society website at http://www.steamboating.org
6. Monotube boilers can work very well in marine plans. Steamboats tend to be operated at a constant speed and thus liitle adjustment is necessary. Wally Mounster (located in Tasmania) has used them for well over 20 years, and Herreschoff was building and installing them in steam launches in the 1880s. Wally's boats are Otasell and Diabolito. Google them and you'll find out more.
7. For remote control of the engine, try modifying the "teleflex" cable devices used for outboats - you'll be able to control forward/reverse and speed.

But buy Salty's plans first. Reliable now ships the .pdf's via email so you can have them next day.

[87gn@tahoe]

Ron, it seems that the link to Mosquito's specs is broken.


Maybe this'll work:

http://www.northweststeamsociety.org/Pa ... SSBmos.htm

[artemis]

Ron, it seems that the link to Mosquito's specs is broken.


Maybe this'll work:

http://www.northweststeamsociety.org/Pa ... SSBmos.htm

Thanks - I've corrected it in my squirt now.

[stevey_frac]

Artemis. You are a fount of knowledge. Thank you. Very much.

One thing I do not understand. The Mosquito isn't that much larger then the salty is it? 20' vs 26'?

And yet a recommended 5 hp engine for salty, and 14hp for the mosquito? Is the mosquito also massively overpowered? or am i missing something.