Rob Lewis Posted July 28, 2011 Share Posted July 28, 2011 I'm at the stage of trying to find a tank for my latest build but i'm not having much luck finding one which i think will be large enough that will fit into the space i have. I'm going to be running a super tigre 61, but the largest tank i can find to fit is an 8oz. I haven't run the engine yet so don't know what sort of run time that will give but i don't think it will be that long. The tank needs to be less that 107mm long to fit between the formers and less than 53mm tall and 73mm wide to fit through the former to be removed if need be. Its the length that is really restrictive and I can't leave the tank in the hole in the former as this would leave the clunk sitting around 3" below the carb level. If i could get a tank the exact size i need it would be around 12 - 13 oz, but theres never exactly what you need. I'm a bit stuck which way to go. I've read about dual tanks which could be an option run in series but it adds complexity and could be a pain to fill, although i'd have ample room for 2 6oz or 2 8oz tanks side by side. Is there any other solutions anyone could think of? I can't cut the former to fit a tank because its the former where the wing dowels locate. Cheers Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 28, 2011 Share Posted July 28, 2011 Having the clunk 3" below the carb level isn't an issue, so long as the level of the fuel is at or above the carb so that it gets to the needle valve when you start the engine. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 28, 2011 Share Posted July 28, 2011 can you extend the hole in the former to raise the back of the tank or allow a fatter tank through? With a 53mm (2" tall) tank and the clunk 3" (75mm) below the needle, that puts the top of the tank an inch below the needle unless he tank is at a fair old angle. Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted July 28, 2011 Author Share Posted July 28, 2011 Thanks chaps, its hard to describe the angle so i drew a quick pic. So you can see if the tank was aligned with the bung in the hole in the firewall and the back of the tank was still in the hole in the former the tank would be at an angle which is why the clunk would be 3" lower. Although as you deduced the top rear of the tank will be about 1/2" - 1" below the carb line. I can widen the hole in the former but can't make it taller due to the location of the wing and wing dowels. I'm a bit stuck where to go with this. Quote Link to comment Share on other sites More sharing options...
Jimbo565 Posted July 28, 2011 Share Posted July 28, 2011 Rob, I've had a situation like this before,I brought the rear end of the tank into the wing bay and modified the lower wing sheeting to clear the tank,the mod cant be seen with the wing in place. Just a thought. Jim Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted July 28, 2011 Author Share Posted July 28, 2011 Thanks Jim, Interesting idea. The wings on this are foam core and already joined and glassed, but i may beable to get away with just taking the leading edge off. Although it all depends on how it lines up with the location dowels, as there are 2 for the wing and 2 for the canopy. CheersRob edit: Just had a quick look and the dowels for the canopy would get in the way. Back to the drawing board. Edited By Rob.. on 28/07/2011 11:49:16 Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 28, 2011 Share Posted July 28, 2011 Rob, I'm afraid your drawing doesn't mean anything to me. Not sure what's depicted. Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted July 28, 2011 Author Share Posted July 28, 2011 Sorry PatMc, i guess i'm used to looking at it so it looks normal to me. Its a side on view of the nose area. The vertical line on the left is the firewall, with the hole for the bung shown as the dotted lines. The other vertical line on the right side is the former, with the dotted lines depicting the hole in the former. Everything to the right of the former is the fuselage side and the wing seat as its a mid wing plane. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted July 28, 2011 Share Posted July 28, 2011 Rob Is it not possible to accept a smaller tank? I guess you have mentioned the size of the motor, although i cannot see it. To an electric flyer 1/2 lb of weight seems quite a lot. I guess for IC modellers the trim change is not an issue. Another thought, I have seen many years ago, a sketch of how two tanks were installed in a Vulcan. A smaller tank was fed by a larger tank. Could this approach be viable? Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted July 28, 2011 Author Share Posted July 28, 2011 Thanks Erfolg. Think i said in the first post but its a 61 size engine so will guzzle the fuel, and i'm not too sure about the run time i would get from a smaller tank, but it may be the last resort. I've seen about using 2 tanks and i think thats probably what i'll try. There seems to be a couple of ways to do it either a main tank with a header, similar to the way i believe its done in helis, or 2 of the same tank piped in series which will probably be the way i'll try mounted side by side. It means there will be a slight lateral trim change but both tanks will be near the centreline so i'm hoping the change won't be big enough to notice. I can always stick one smaller tank in at a later date if i have troubles with it. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 28, 2011 Share Posted July 28, 2011 Rob,go electric,I bought a job lot of tanks and Ill get my ruler out and have a look Quote Link to comment Share on other sites More sharing options...
Steve Houghton Posted July 28, 2011 Share Posted July 28, 2011 Rob, This doesn't help your immediate problem, but is just a thought that was triggered by your thread: As a camper I use collapsible poly water bottles than can be crushed down for packing into the car. Fill them with water and they pop out again. I just wonder why no-one has manufactured a fuel tank based on the same concept. It could be crushed/squeezed and generally pummelled to fit into awkard spaces. The only problem may be the odd wrinkle left in the tank sides, that may affect the smoothness of the clunk, so these would have to come in various sizes so that a 'near fit' could be achieved. How do I contact the patents office - this could be a winner! Edited By Steve Houghton on 28/07/2011 17:51:49 Quote Link to comment Share on other sites More sharing options...
fly boy3 Posted July 28, 2011 Share Posted July 28, 2011 Not 100% sure about this, but I think the jet boys use this type of tank some times. Cheers Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted July 28, 2011 Share Posted July 28, 2011 you need to buy one of these i bought mine in america, but they are stocked over here, you could put the tank on the moon, and it will still shove fuel through Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 28, 2011 Share Posted July 28, 2011 Steve, the idea isn't new. The first proper control line stunt model (circa 1958) I made & flew, a KK Stunt Queen, had a tank made from a toy balloon. It was housed in a balsa compartment just behind the engine & accessible for filling via a simple hinged hatch on the side of the fuselage. The tubing between tank & engine was joined by a short brass tube & of course there was no need for any vent or clunk.I had an AM35 diesel in my model which meant that I had to make a new tank every outing as diesel fuel rotted the balloon but this wasn't a problem for glow engines.The illustration is taken from the 1959 edition of Ron Moulton's Model Engine Encyclopaedia. Quote Link to comment Share on other sites More sharing options...
Jimbo565 Posted July 28, 2011 Share Posted July 28, 2011 Giving your age away now Pat. Quote Link to comment Share on other sites More sharing options...
kc Posted July 28, 2011 Share Posted July 28, 2011 Have you considered eliminating the dowel by using 4 wing bolts instead of dowel & 2 bolts? This might enable you to cut the former for tank access. Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 28, 2011 Share Posted July 28, 2011 Posted by Jim Carss on 28/07/2011 19:15:39: Giving your age away now Pat. Age has it's advantages, Jim. Polite young people occasionally give up their seat in a packed Metro & hold doors open etc. But I expect you'll have already experienced that. Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 28, 2011 Share Posted July 28, 2011 Posted by kc on 28/07/2011 19:23:10:Have you considered eliminating the dowel by using 4 wing bolts instead of dowel & 2 bolts? This might enable you to cut the former for tank access. A better idea might be to cut away the wing LE as Jim suggested & glue the overwing fuselage fairing to the wing with the dowels fixed to the fairing at a point above the tank. Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted July 28, 2011 Author Share Posted July 28, 2011 Thanks for all the replys everyone. Flexible tank, sounds good, if there was one that was the right size, definately onto a winner there Steve. The ones i've seen on jets have all been long bags, almost like a drip bag used in a hospital that holds no air so shrinks as the fuel is withdrawn, but then i believe they all use pumps. Using 4 wing bolts would work, although a fairly major modification would be needed to the fairing to allow it all to match up. Unfortunatey i can't really attach the overwing fairing to the wing as the angles don't really equate for getting the wing in and out due to the amount of space (or lack of). The plan actually had the wing and fairing all as one piece but when i offered it all up it was too tight to get everything together and apart so i made the canopy removable. I guess i have taken the 'easy' route and went to the LMS today and brought 2 smaller tanks that will fit in the space available. I'm going to run some tests with the tanks linked in series and parallel and see how well the system works. With them in series there will be a slight lateral imbalance but i don't think enough to be concerned about. Having them in parallel will solve this problem but could be difficult getting them both to drain at a constant rate. I can't really see a problem this way and theres no modifications that need to be made to the plane to get them to fit. I'll let everyone know what i decide on but thanks for all the help. Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted July 28, 2011 Share Posted July 28, 2011 you dont mention the perry pump, this will solve every problem you have, except insufficent fuel, Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted July 29, 2011 Author Share Posted July 29, 2011 Sorry Alan, didn't mean to miss any out. The perry pump would obviously solve all the problems instantly, but i'm looking for a cheap option and don't really have the spare cash to buy one. Quote Link to comment Share on other sites More sharing options...
Shaunie Posted October 15, 2011 Share Posted October 15, 2011 Hi Rob, On one occasion when I couldn't get a tank to fit I made one out of sheet steel from an old 5 litre oil can, easier to make than you would think. Two square end caps with a small lip tapped over right round and one strip formed into a square tube all soldered together. Nicked a clunk from an old tank and a bit of silicon pipe withstood the soldering ok. Still got it somewhere, I'll see if I can post a pic. It was about 6 ounces capacity and it was not very heavy (little bit more than a comparable plastic one but not much). To correct the height difference is it possible to invert the engine (sorry can't see your sketch, it no longer displays). Shaun. Quote Link to comment Share on other sites More sharing options...
Rob Lewis Posted October 16, 2011 Author Share Posted October 16, 2011 Cheers Shaun, I ended up fitting 2 smaller tanks and running them in series, so the exhaust pressure goes to the feeder tank and feeds the main tank. I've run a couple of tanks through and it works fine. Engine is side mounted because i'm using a pitts muffler so couldn't have moved it. Heres a pic of what i ended up with. Rob Edited By Rob.. on 16/10/2011 15:11:46 Quote Link to comment Share on other sites More sharing options...
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