Ernie Posted November 27, 2012 Share Posted November 27, 2012 Hi Guys, Due to incredible lack of forward planning on my part, I find that it is necessary to manufacture a tank for glo fuel. I don't want to use metal, because of the weight, and I can never get plastic to stick well My thoughts are to make an open top balsa box, and line it with glass cloth and resin. It would have a removable and well sealed lid (so I could get the glass and resin in) and all the usual feeds and fillers Any thoughts? ernie Quote Link to comment Share on other sites More sharing options...
John Cole Posted November 27, 2012 Share Posted November 27, 2012 Tinplate is pretty light and solders relatively easily. Your alternative sounds horrendous to me! But why can't you use a conventional tank? Quote Link to comment Share on other sites More sharing options...
Ernie Posted November 27, 2012 Author Share Posted November 27, 2012 Hi John,Why can't I use a conventional tank? Oh dear, The only space left is a funny shape. I used to solder up tanks for C/L team racers. It's the weignt of the solder that worries me...The balsa seems a bit daft to me too, But I can't think of a better way ernie Quote Link to comment Share on other sites More sharing options...
Paul Williams Posted November 27, 2012 Share Posted November 27, 2012 Your losing the plot fella, but hey I love outside the box things what about cutting a foam block to shape then use an old tank neck fibreglass around it all than when dry fill with petrol which will disolve the foam please tell me if it works I will write to the pope and get it on his miricle list Quote Link to comment Share on other sites More sharing options...
Ernie Posted November 27, 2012 Author Share Posted November 27, 2012 Hi Paul, I suspect you're right about the plot. Probably to much of the red stuff. I'm sure I've read about making a wooden tank (maybe the WOO) I once make a cowl as you suggest, and it did work very well, but, I'm a tad concerned about foam residue in the fuel. It doesn't alter the fact that I can't get a conventional tank in the space, unless I have a 30 sec flight time ernie Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 27, 2012 Share Posted November 27, 2012 Can you put a main tank in remotely with a header tank in the restricted space (like helicopter flyers sometimes use)? I used a similar arrangement during experiments to get a Supertigre 91 running reliably in conjunction with a Perry Pump - the power was amazing but so was the fuel consumption - so I had to add a second tank near the C of G. Nothing worked with the ST by the way - until I bunged an OS 4 stroke plug in it out of desperation and it ran like clockwork ever after! It was an incredibly frustrating engine - loads of power, idle for miutes at a time and transition perfectly - but it would cut dead for no apparent reason as soon as you were happy it was sorted! Quote Link to comment Share on other sites More sharing options...
Paul Williams Posted November 27, 2012 Share Posted November 27, 2012 mustangs had a drop tank food for thought Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 27, 2012 Share Posted November 27, 2012 Thinking about what you were saying Ernie, if you don't build up large fillets the solder shouldn't add any significant weight unless you're building something incredibly small. Quote Link to comment Share on other sites More sharing options...
IanN Posted November 27, 2012 Share Posted November 27, 2012 A balloon? Used to use those in control liners. Maybe one balloon inside another to provide a little insurance v leaks or bursts Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted November 27, 2012 Share Posted November 27, 2012 Its a facinating thought Ernie but I can't think solder/tinplate will be heavier than glasscloth & resin by very much, if at all..... I do agree with the others that the glass cloth route sounds horrendous & fraught with potential problems.....maybe try a test box first & see if it works!!! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 27, 2012 Share Posted November 27, 2012 What effect will the fuel have on the resin? I know that the proposal to up the alcohol content of road fuel to 10% is causing concern in the historic vehicle world with GRP tanks being potentially affected. I'd guess that eopxy resin would be better than polyester which is widely used in the automotive world but I'm no chemist... Quote Link to comment Share on other sites More sharing options...
Ernie Posted November 27, 2012 Author Share Posted November 27, 2012 Hi all, Thats what I like about this forum, We can bounce daft ideas around. Ian, I did wonder about a balloon. would it not tend to give more pressure than a conventional tank? Maybe a header tank is a solution, Martin. I'm off to the 'shop to have a bun, a cup of tea, and a think Il'l keep you all posted ernie Quote Link to comment Share on other sites More sharing options...
Mogs Posted November 27, 2012 Share Posted November 27, 2012 An interesting problem, I would try the wooden tank with many layers of fuel proof, then go with the balloon inside, having made sure all right angles are filleted round. Drop tank sounds easiest. I look forward to reading your solution. Quote Link to comment Share on other sites More sharing options...
Mogs Posted November 28, 2012 Share Posted November 28, 2012 Hi Ernie If you coat the inside of the wooden tank with glue, then fit and presurise the balloon it should stick to the walls, once the glue has set the balloon should not collapse back and therefore no additional pressure. You will have to allow any air trapped between the wooden tank walls and the balloon to escape during the process. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 28, 2012 Share Posted November 28, 2012 Sounds like a recipe for a tank collapse if there's a slight weakness in the balsa when it's done or gets a small knock! Also, what's the life expectancy of the average party balloon exposed to glow fuel? Not long if elastic wing bands are any guide! Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 28, 2012 Share Posted November 28, 2012 You will end up wasting your time and probably loosing your model with either fuel soaking or dead stick .Plastic is the only proper solution for glow fuel . Tin plate, brass or copper are fine for diesel fuel but will rust or be attacked by any nitro in the fuel. Have a look in supermakets or the chemist for a suitable bottle. my local chemist were very helpful when I wanted a tank fo a small model converted from electric. You may hav to make the fittings to screw through the lid or sides for the pipes but it will be a tank that will last and work. Better still bite the bullet and modify the model to accept a commercial tank. E.D. Quote Link to comment Share on other sites More sharing options...
John Cole Posted November 28, 2012 Share Posted November 28, 2012 Engine Doctor: rust is oxidised iron. Brass and copper CANNOT therefore rust as they do not contain iron. Tinplate is mild steel (i.e. an iron / iron carbide mix) coated with tin. The tin stops the rust from forming. NItromethane is NOT acidic and will attack none of these metals. The products of its combustion are acidic, but the material itself is not. See for instance this. But I agree with your conclusions: modify the model. Quote Link to comment Share on other sites More sharing options...
IanN Posted November 28, 2012 Share Posted November 28, 2012 Posted by Martin Harris on 28/11/2012 13:01:16: Also, what's the life expectancy of the average party balloon exposed to glow fuel? Not long if elastic wing bands are any guide! That was never an issue. They only cost pence - we used new ones for every session Quote Link to comment Share on other sites More sharing options...
John Cole Posted November 28, 2012 Share Posted November 28, 2012 Ernie: can you take a photo of the tank bay and post it here? Then we can all see what the problem is. Don't be shy... Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted November 28, 2012 Share Posted November 28, 2012 A wooden fuel tank with a removable lid? It certainly sounds interesting, and indeed, a bit different. It also sounds like a prolonged total penance for making the initial drop off. I think I’d be inclined to start the whole thing again if necessary, probably less effort anyway, and sooner rather than later, too, because like E.D., I also think this arrangement may just not stay standing for too long! I must admit, I’ve been poggering somewhat over exactly what the problem is…… and I’ve not really reached a satisfactory answer……. The drop tanks on the Mustangs were made from cardboard, I believe, presumably with a quick internal coat of some sort of sealant, but I guess that in the main they would only have to last a few hours; and I don’t suppose anyone was ever going to hang about to ask for them back! Metal is attacked by the methanol in the fuel, I had it happen to me years ago, the brass tube, or I suspect might have been some sort of cheaper type of brass alloy, in the tank swelled up, started flaking and split open. Methanol is reputed to also affect copper and aluminium, although I replaced the brass with small bore copper tube, which is perfect for the job; and ally is often used in Chinese ARTF models and I’ve never seen either of these types affected. I believe that drag racers and the like that use methanol as fuel replace any brass fitting in the fuel system and the carburettor etc. to avoid this, probably with stainless steel. I’ve never used nitro in the fuel, always just straight methanol and oil. I’d guess that as John says, any unprotected iron, or ferrous, fittings would soon go rusty, so that might not be a good idea, either. PB Quote Link to comment Share on other sites More sharing options...
Rusty C Posted November 28, 2012 Share Posted November 28, 2012 Why not try one of sullivan flex tanks **LINK** I used one in my wot 4 e conversion, They are great you can heat them to any shape and even better, If you get it wrong simply reheat and they will go back to normal ! rusty Quote Link to comment Share on other sites More sharing options...
Ernie Posted November 29, 2012 Author Share Posted November 29, 2012 Good morning from sunny dry France, Thanks for all the input. I didn't know about the flexi tank. I'll take a pic later today, to explain more ernie Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted December 20, 2012 Share Posted December 20, 2012 Posted by John Cole on 28/11/2012 14:38:51: Engine Doctor: rust is oxidised iron. Brass and copper CANNOT therefore rust as they do not contain iron. Tinplate is mild steel (i.e. an iron / iron carbide mix) coated with tin. The tin stops the rust from forming. NItromethane is NOT acidic and will attack none of these metals. Hello John . You are correct in saying" brass and copper cannot rust" but they CAN corode . You obviously have not used a tin plate tank with glow fuel or you would have noticed that they DO rust . The tin plate only gives a short protection against methanol which is mildly acidic then the rust starts . Have you not had the brass tubing in fuel tanks go brittle and break; or noticed the green residue left in tanks after a long lay up ?The green residue is dissolved copper ! Ask any fuel manufacturer if they use brass or copper tubing in their equipment. The following from a friend with a sceince background should help explain. One of the potential drawbacks of using high concentrations of methanol (and other alcohols, such as ethanol) in fuel is its corrosivity to some metals, particularly aluminum. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminum from corrosion:- 6 CH3OH + Al2O3 = 2 Al(OCH3)3 + 3 H2O In other words the Methanol attacks aluminium and the copper content in brass tubing. The net result (with Brass tubing) is Copper methoxide, which is soluable in methanol - hence no 'green gunk' seems to be in the pipes, but the fuel blackens. Also Halide ions in the impurites can also aid corrosion. This of course begs the question, why do tanks come with brass tubing? I for one have experienced this a few times, and I know others have. So SLEC tanks for me, or replace all my tubing with plastic. Quote Link to comment Share on other sites More sharing options...
John Cole Posted December 20, 2012 Share Posted December 20, 2012 Your friend's point about methoxide corrosion: aluminium is particularly susceptible to methoxide corrosion for 2 reasons: aluminium is easily oxidised and the surface of metallic aluminum oxidises rapidly in miost environments. The methoxide corrosion depends on an oxide coating. Once the oxide has corroded away it will reform and then be attacked again by the methanol. Additionally, the methoxide formed is umstable in the presence of traces of water, and converts back to yield a hydroxide ion. This attackes aluminium in a different way, forming aluminates and hydrogen. Tin does not have an oxide coating and so is not attacked this way. Neither does copper. Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted December 20, 2012 Share Posted December 20, 2012 From some practical experience, and that’s a good few years now, I’ve found that methanol can affect the brass tubes in model fuel tanks; and rather than that it attacks the copper content, I suspect that it may be the zinc element that gets a kicking; but it might also be that these ‘brass’ pipes are some sort of brass alloy, and which might increase it’s susceptibility to damage from methanol. As I said in my previous post, @ 28/11/2012, I used copper tube to replace the brass, and this has never shown the slightest signs of any corrosion. And as I’ve always believed brass to be a mixture of copper and zinc…… I’ve had it happen to me, plus I’ve seen other pilot's examples, only very recently indeed a colleague showed me a fuel tank brass pick-up tube that had spit open inside the bung. This had started to cause problems but fortunately as soon as he started pulling it apart it was obvious. I have used many tanks over the years with aluminium tubing, and I’d have thought that pretty well every ARTF comes with a ditto item, and I’ve never seen any such damage to any of these. I’m sure I’ve never heard of, or read about, any others either. So does it actually happen? Maybe the oil content in the fuel affords some sort of protection. So I think that if it were necessary I would be quite happy to replace any brass tube with either copper or aluminium. PB Edited By Peter Beeney on 20/12/2012 14:04:21 Edited By Peter Beeney on 20/12/2012 14:05:54 Quote Link to comment Share on other sites More sharing options...
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