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[John Foreman]

I am recommissioning and bringing up-to-date a model steam boat. The boiler does not have provision for a clack valve so I will run it on what water I start with in the boiler. It is recommended that one arranges it so the gas will run out before the water so is there a formula to work this out so I can get a refillable gas tank of the correct capacity. It did use disposable gas cylinders. I have a Clevedon Steam EGV and figure that will not change the water gas boiling ratio to any great extent.

[DBS88]

John the medium size refillable gas tanks contain enough gas to run for more than a hour so suggest filling the gas tank and then weighing it. Fill the boiler and then fire it and run the engine at about 2/3 max rpm and see how long it takes for the boilers water level to get down to the low level. Then re weigh the gas cylinder. This will tell you two things, first the sort of time you can safely run for, so you can set a timer to bring the boat in, and second the weight of gas consumed, so you will then know the weight of gas to put into an empty tank. You will then need to test this to double check it’s ok.

[John Foreman]

Thank you for that and it may be that is the way I have to go rather than calculating. I do have vague memories about calculating this sort of thing but I cannot recall how.
What I am trying to do is follow what is in the "The Boiler Test Code 2018, Volume 2 - Boilers under 3 bar litres". For a "Previously uncertified boilers - initial certification test." These are the rules that are also followed if the certificate has been lost. Section 7.3 says "The boiler will be subject to an initial hydraulic shell pressure test of twice Working Pressure (2xPw) and is valid for the life of the boiler. Then it is steam tested with all the pipes, etc., in place. Prior to this section 1.2 sates ".... If no means of supplying water to the boiler whilst working is present, the fuel supply shall be so arranged that it is used up before the water is exhausted." So the rules say that I cannot use a timer to comply.

[rhavrane]

Bonjour,

John, don't worry, your problem can have simpler solution

Personnally, I like using large gas tanks as they are supposed to freeze less than the small ones.

Because of this choice, I ALWAYS test my boats in my bathtub or on table if too long, boiler full, machine operating without stopping (except for a gas regulator test) at middle throttle and playing with the whistle to time the time it takes for the boiler to empty, which means water is at the lower level of the boiler which is not empty so.

Then, on the pond, i always check my navigation time with my stopwatch.

Why am I fully confident with my method ? At first because it is very difficult for our torchs or ceramic burners to heat until debrasing a boiler especially when a little steam remains in the boiler. Furthermore, I have ragulators and RC safety gas valves in case of big problem like propeller blocked by a piece of wood for example (lived experience).

[Bunkerbarge]

The Boiler Test Code contents are not recommendations, they are requirements to pass the steam test.

John you are perfectly correct in your interpretation.

[DBS88]

John apologies, my suggestion is that you only put enough gas in an empty tank so that it runs out before the water in the boiler, hence the reason for weighing the tank. The reason for the timer was so you brought the boat in before the gas ran out, after all you don’t want your boat to be stopped in the middle of the lake. Having witnessed a boiler run out of water and the white steam be replaced by black smoke as the cladding turned to charcoal making sure you run out of gas first is safest

[SteamboatPhil]

All good sound advice, with luck John could post a picture of the boat, its a thing of beauty .


John I have replied to your e mail

[John Foreman]

I am having a try to put a couple of pictures of the boat up as she was before I started the recommissioning.

[John Foreman]

I do have an early alloy hulled Seekadett that is about 630 mm at the waterline. A video of her can be seen here: (104) Der Seekadett trial - YouTube
I always time her on the water and to be honest, although she run and the RC works well, she does not have a lot of freeboard and I am very nervous of any water that is not flat and other model boats. I have had model boats glug and she would be an expensive loss if she went under.

[John Foreman]

DBS88 suggestion might be the way to go in that I could weigh the disposable gas tank and run through a steaming from full boiler down to above the fire-tube. Weigh it again to give me the gas usage and then buy as gas tank that will take that, or less. It would not be an absolute figure as there are variables like starting temperature, calorific value of the gas and air pressure, but I would be dealing with those if a had a formula that would also not have things like burner efficiency.

[AlexC]

Hi John,What a lovely steamboat you have there.
Can you not replace the filler cap on the top of the steam dome with a Goodall valve... that would allow you to add water whenever needed.The only thing you would need to know was how long you can run from a full boiler until the level was down to just above the fire tube.You can then come alongside and top the water level up, whilst still in steam, using a hand operated pump or spray type bottle with a suitable hose attached that fitted into the Goodall valve.

No worries about size of gas tank.
I hope you find a solution.
AlexC.

[derekwarner]

Hullo John.....I understand you mention revisions to gas capacity, however you also suggest recommissioning

Many yacht type Craft such as the Seekadet, incorporated a design with the propeller diameter protruding lower than the keel itself. To protect the propeller from any form of mechanical damage due to this height protrusion issue, the builds incorporated a metal Skeg attached to the keel in a low u type profile that connected to the rudder Pintal

So this additionally provided a substantial mounting for the Rudder to be increased in depth, resulting in vastly improved steerage

It would be a tragedy if the recommissioned vessel suffered a damaged propeller due to steerage that could have been improved

Derek

PS......I became a little confused as at 1:02 into your video of your vessel, we see  a Seekadet complete with the skeg & deeper rudder??

[ooyah/2]

PS......I became a little confused as at 1:02 into your video of your vessel, we see  a Seekadet complete with the skeg & deeper rudder??







Derek Warner being "confused"  ?? never, re read post No 8


George.

[KNO3]

Hi John,What a lovely steamboat you have there.
Can you not replace the filler cap on the top of the steam dome with a Goodall valve... that would allow you to add water whenever needed.The only thing you would need to know was how long you can run from a full boiler until the level was down to just above the fire tube.You can then come alongside and top the water level up, whilst still in steam, using a hand operated pump or spray type bottle with a suitable hose attached that fitted into the Goodall valve.

No worries about size of gas tank.
I hope you find a solution.
AlexC.

This is a very practical suggestion and easy to implement.

By the way, the blue boat looks very nice. Is that a Seekadett hull or something else?