Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Steam => Topic started by: pipercub1772 on May 22, 2009, 01:53:06 pm
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hi ,doing well with my steam launch some picks shortly, i have room for the small commercial gas tank in the bow section are there any benefits in using the refillable type or is it ok to go with the commercial tanks ,also is it beneficial to try and warm the tank possibly from the condenser ,1st time attempt at steam thanks guys allan.
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Hi Allan,
Spooky...
I've just this minute come in from testing my steamer using one of those 460gram gas "batteries" that Halfords sell.
The gas cylinder sits in the bow a couple of inches away from the boiler burner with no direct heating (its against the MPBA rules anyway).
Since the cylinder is semi-enclosed, I was concerned about the ambient temperature exceeding the 50degC as stated on the cylinder instructions, so I placed a max-min thermometer near it. After about 45 minutes of testing (with the sun beating down as well) I checked the max-min and it was reading 35degC maximum, which from my experiments with warm water jacket (a decorators paint pot!) was more than enough to maintain gas pressure under light loads and allows quick recovery after a heavy load of usage.
My boiler is a flash type (maiden voyage tomorrow at Wicksteed) and has steam temperature control which operates a gas valve servo, therefore it is more tolerant of gas pressure changes.
For static pool testing, I use a 13kg propane tank, which is far more economical than the £5 cylinders. The Calor gas cylinder was an initial £29 tank fee plus £21-50 for the actual gas and from then on you exchange the empty for a full one for £21-50, as you most likely know. The equivalent amount of gas from the 460gram cylinders would be about £145!#
I suspect Halfords and other outlets only stock the cylinders for campers, therefore they are seasonal and seem in short supply during the Winter. I usually build up my own stock while they are on the shelves.
Ian G.
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hi thanks for that reply the tanks i am using are the coleman 70 butain 30 propane the small 100gram size or could buy a 50ml/75ml size refillable from maccsteam etc? you're views appreciated. thanks allan
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How big a launch is it? Open or cabin? Plank on frame or plastic?
Greg
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hi thanks for that reply the tanks i am using are the coleman 70 butain 30 propane the small 100gram size or could buy a 50ml/75ml size refillable from maccsteam etc? you're views appreciated. thanks allan
The 100gram size is ideal, but I can no longer find them in Toronto Canada. I was told by a store manager that Coleman is no longer making them.
Regards,
Gerald,
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Hi Allan,
I'm currently installing a steam plant into a tug. i have opted for a commercial refillable tank for space & aesthetic reasons. previously i have used both disposable & refillable tanks in models &, to tell the truth, have found little difference between the two. refillable tanks i have used have always been of a smaller capacity than the disposable ones, & i have found these smaller capacities seem to suffer more from cooling down (& consequently pressure drop) than the larger.
On my latest project I am using heat from the condenser to warm the gas tank, & it seems to maintain constant pressure. however i have only run the plant on the bench so far, & running it inside the boat in real conditions will be considerably different. As with all steam models, the more efficiently you use the steam when you are opperating the boat, the better the performance will be, & for me that the fun part of steam power.
If you do decide to heat the tank, please please take notice of what Ian said, & ensure that the tank never gets hot. I too have found a temperature of between 30 & 40 degrees seems perfect.
The refillable tanks are cheaper to run that the disposable ones in the long run, because you can buy bigger bottles of gas to fill them. Also the generally smaller capacity can be helpful because the plant can be made to run out of gas before it runs out of water, which removes the possibility of running the boiler dry. They also tend to look better in the models i my opinion. That said, disposable canisters perform perfectly well in my experience, I'm sure some other on here will comment on this subject too.
Cheers Glenn
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:-))thanks for the help guys ,the model is based on a windermere steam launch 48 "long 8" beam,glass hull obtained from scale hobby's in Scottsdale,mahogany topsides &cabin ,lime planking to decking .all scratch built i got a 3/1/2 horizontal boiler from macadam &and a dbl acting twin Cly engine3/8 bore 1/2 stroke of Eba just painting hull at the moment will take some pictures shortly may need my nephew to get them on the site bit of a duffer at technology many thanks PS /thank god for spell check . allan
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sorry guys even messed up on spell chq should read scale hobbys skelmersdale & maccsteam boiler allan
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I think it has just about all been said as regards gas tanks. My own current project includes a commercially purchased tank but with a much better filling arrangement and a means of raising steam from an outside tank to save on the cooling effect. Have a read here, particularly Chapter 12:
http://www.modelboatmayhem.co.uk/forum/index.php?topic=6094.msg166171#new
Having said that my next project is to be a launch and I am intending using the camping gas bottles to do away with the requirement of having to refil the on board tank so frequently. I completely agree that a nicely enamelled tank with all the fittings actually looks a lot better so I may change my mind yet and the benefit of being able to warm the gas tank then control it with a pressure regulating valve has proved to be an excellent way to do it.
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regarding the small 90 gram camping gas cans like colman etc ,would it be possible to refill them with the much larger 440gram size cans that are much more economical i/e connect the empty 90gram size to the 440 via 2 gas can valves and copper tube and allowing the larger one to fill the smaller one ,any thoughts .allan
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The small Coleman type gas tanks are not classed as refillable and if you rig up any form of device to enable you to do so would invalidate any insureance that you have and put you and members of the public at risk. Refillable tanks have to be certified and be made to a whole different level of specification than disposable tanks.
You could get a bigger refillable tank made up and certified by an appropriate vendor but it would be getting quite heavy at that size.
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There is reports that someone who looks like me has been seen in my backyard connecting two camping stove fuel tanks together with copper tube. This person fills the small 100gm tanks to 75gm from a 900gm tank. The weights are measured on a digital postal scale. I of course would never do this as the tanks are marked nonrefillable.
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Please note the views and opinions expressed by members do not necessarily reflect the views of Model Boat Mayhem or the site owner.
The practise described above is actually very dangerous and should never be attempted by anyone.
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I cannot see what the problem is disposable cans are not that dear. you need to get the mix correct for the boiler to work safely and correctly, I use refillable tanks, filled from disposables, it means I don't have to carry a large tank about in the car for my safety and the passengers.
but we all have our own ideas, I am just glad gas is the norm now and not converted primustoves, must save a lot of boats and hospital trips.
Proteus
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I think it has just about all been said as regards gas tanks. My own current project includes a commercially purchased tank but with a much better filling arrangement and a means of raising steam from an outside tank to save on the cooling effect. Have a read here, particularly Chapter 12:
http://www.modelboatmayhem.co.uk/forum/index.php?topic=6094.msg166171#new
Having said that my next project is to be a launch and I am intending using the camping gas bottles to do away with the requirement of having to refil the on board tank so frequently. I completely agree that a nicely enamelled tank with all the fittings actually looks a lot better so I may change my mind yet and the benefit of being able to warm the gas tank then control it with a pressure regulating valve has proved to be an excellent way to do it.
your tanks look like they are a permenant fit , do you fill your tanks in the boat ?
Proteus
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Under no circumstances should you warm / heat any gas cylinder commerical or other wise, and refillable gas cylinders should be pressure tested :-)
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I think it has just about all been said as regards gas tanks. My own current project includes a commercially purchased tank but with a much better filling arrangement and a means of raising steam from an outside tank to save on the cooling effect. Have a read here, particularly Chapter 12:
http://www.modelboatmayhem.co.uk/forum/index.php?topic=6094.msg166171#new
Having said that my next project is to be a launch and I am intending using the camping gas bottles to do away with the requirement of having to refil the on board tank so frequently. I completely agree that a nicely enamelled tank with all the fittings actually looks a lot better so I may change my mind yet and the benefit of being able to warm the gas tank then control it with a pressure regulating valve has proved to be an excellent way to do it.
your tanks look like they are a permenant fit , do you fill your tanks in the boat ?
Proteus
I do Proteus, via a specially made set up that allows me to fill with liquid until it reaches a dip tube, which vents through a connection in the hull. When the vent starts to spit liquid I know it's full. Gas is not able to vent inside the model, I can guarrantee the tank is filled to the level and there is always a suitable space above the liquid level in the tank. This set upincludes another branch that also enables me to raise steam from an external tank before changing over to the on board tank for sailing thereby saving a lot of gas and reducing the cooling effect.
I've described it in the Ben Ain build thread.
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Getting back to the disposable cylinder question, I use a single 220gram cylinder in my 44" Windermere launch. In my 80" paddler I can fit two of these linked in parallel. In the launch, even though it has a smaller engine and boiler cannister temperature drop is a problem on long runs. On the paddler it never is even though the draw off of gas is much greater for the bigger boiler and engine. The secret is surface area and we find the same thing with the large industrial heaters we hire at work. If you have one cylinder it freezes but double the area and it will run all day because you are drawing the gas off double the area of liquid. A long rectangular tank will cool down much less than a tall skinny round one even though they have the same quantity of liquid in them. Therefore if you can find room to fit two of the small 100gram disposable cannisters in to the boat they will run at a more even pressure than one 220gram cannister for longer. Hope I have made myself clear. Ian.
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Good tip Ian and makes perfect sense.
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Hi,
I sailed my experimental flash steam boat at the Dover Model Boat Association open event this weekend and remembered to put the max/min thermometer in bow with the gas cylinder.
On the first run of 31 minutes the maximum temperature in the semi-enclosed space above the cylinder was 32degC (ambient was 20degC) with the sun out and moderate steaming.
On the second run of 44 minutes under heavy steaming, the temperature was "You've got to buy a new max/min thermometer" degC ! @#*
Well, the very top of the max/min plastic housing was slightly brown and distorted and don't ask were the contents of the thermometer dissappeared to!
The temperature must have been well above 50degC at the very top of the space, although well below burning the paint-work. The cylinder itself was cold but not freezing and the cylinder pressure was 3.6bar (54psi) when freshly installed and dropped down to 1.5bar (22psi) when running under heavy demand - more than adequate for running the flash boiler.
I monitor the cylinder with a pressure transmitter and display the value on a servo driven indicator. I can then observe from the shore the pressure as the boat passes by.
I shall have to consider fitting a cowl vent on the bow cover and also monitor the temperature lower down next to the cylinder with my NEW max/min thermometer!
In the photo below (taken by Alan Poole of the Dover MBC) you can see the indicator on the "bridge" showing about 1.5bar cylinder pressure. The green bubbles coming out of the stack are just a trick of the light.
Its fun all this experimenting!
Ian.
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Just in general I would use a refillable gas tank for open style launches and the disposable in tugs etc. In North America there are numerous brands of disposable canisters by various manufacturers and in numerous sizes. If anyone on this side of the pond needs assistance, please drop a line (no pun intended) ;D
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We too have many different brands of disposable gas cannisters on the market here in New Zealand and the performance and length of run varies greatly between them. The biggest difference is the proportion of Propane in the mix. We commonly see anything from 10% Propane to 30% Propane and occaisionally 35%. The higher proportion of Propane means a hotter flame but faster use of the contents however if you turn the gas down you can get the economy back and because you are drawing less gas off the cannister it does not cool down so much so the pressure stays more consistent. For those reasons I now look for the higher proportion of Propane when buying cannisters. Hope this helps, Ian.
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Oh for the return of Paraffin soaked wood and Welsh Steam Coal. O0 {-)
Regards Ian.
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Oh for the return of Paraffin soaked wood and Welsh Steam Coal. O0 {-)
Regards Ian.
Hi Ian,
I can just picture it, A model Steamboat towing a dinghy behind it with the operator in it ( similar to the trains with the riding cars). The operator with a pail of coal in one hand and a small shovel it the other, leaning forward every once and a while to stoke the boiler.
Regards,
Gerald.