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nickyd - n/a
7-Aug-06, 01:08 PM
Hi all,



Does anyone know of any companies that could knock up an aluminium fuel tank to my spec? I say this because I assume that a GRP tank is a no no......



Nick

Gayle Spedding - n/a
7-Aug-06, 02:11 PM
Hi Nick



You could speak to Jon, he could probably do one for you, or failing that, Richard Wiles. Having said that I would think you've got no hope from either of them this side of the World Champs!....... speaking of which, have you booked your flights yet?!



Gayle

nickyd - n/a
7-Aug-06, 02:42 PM
Gayle,



Yeah not bad idea, but how do I know that Jon wouldn't slip a lead weight in to slow me down!



And about those flights, haven't quite booked them yet.......



Nick

Nick Long - n/a
7-Aug-06, 04:01 PM
GRP is fine for fuel tanks. I have a nice carbon fibre one.



Best to use vinyl ester resin rather than polyester, and arrange it so that the fibres are all sealed from the fuel to avoid wicking.



Nick

Jonathan - n/a
8-Aug-06, 12:18 AM
Best to use vinyl ester resin rather than polyester, and arrange it so that the fibres are all sealed from the fuel to avoid wicking.



Nick




Wicking?? I have a grp tank and you're worrying me!! http://hovercraft.org.uk/images/icons/smiley_icons/icon_redface.gif

srn4 - n/a
8-Aug-06, 02:13 AM
If you had exposed glass fibres inside the tank they would absorb the fuel and then allow it to flow slowly out of the tank through the pores in the material.....



Idealy you want your shiny gell coat on the inside of the tank to prevent this from occuring....

Gayle Spedding - n/a
8-Aug-06, 09:50 AM
Seriously though Nick, give Jon a ring. I'm sure he can help...... and I'll make sure he only puts a couple of small bricks in the tank for you!!!



The phone number is on the contacts page!

Jeremy - n/a
8-Aug-06, 09:58 AM
Have you thought of making your own? It isn't difficult using the lost foam process, which allows you to make odd shaped tanks to fit exactly where you want to put them.



The basic process is to make up a tank inner mould, slightly smaller than the finished dimensions, from ordinary polystyrene insulation sheet. Glue the mould pieces together with a thin smear of silcone. Once you have the shape you want, sand the corners slightly to radius them and then cover the whole thing with parcel tape, the brown shiny type. put two overlapping layers on. Don't worry about the filler hole yet, this will be cut out and a plastic or alloy one bonded in later.



Once you have a nice smooth male mould, give it an epoxy resin gel coat. I use West System epoxy thickened with colloidal silica so that it stays at a reasonable thickness when brushed on, without tending to run. Once the gel coat has gone off, but not set rock hard, start laying up fibreglass, using unthickened epoxy. If you want a really light tank, then use 3 layers of 300g loosely woven cloth draped carefully over the mould and build in stiffeners on the outside with strips of cloth layed over thin foam or balsa half round sections. If weight isn't too much of an issue, just use powder bound chpped strand mat and build up the thickness to make it stiff enough.



Once the tank has fully cured (leave it for 4 or 5 days to be sure) you can start to have some messy fun! Using a hole saw, cut out the filler hole, right into the foam mould inside. Hold the tank upright and pour some old petrol into the hole. The polystyrene will dissolve quickly into a horrible sticky gunk, that can be poured out of the hole. The parcel tape will almost certainly remain stuck lightly to the tank inner surface but should come off very easily. All you have to do is get a long nosed pair of pliers, peel off the tape starting at the edge of the filler hole and carefully pull all of the tape out of the hole as one big sticky mess (this is the reason for having two layers, so that it all stays together as you pull it out!).



Once the tape is out you'll have a tank with a very nice shiny inner surface, with no pesky joints to worry about. A filler neck and pickup pipe fitting can just be bonded in, remembering to put some resin over the exposed fibres around the cut out hole.



I've made a couple of tanks this way, plus an odd shaped inlet manifold and a few fairings. It's a neat way to make one-off shapes that would be a pain to make using a conventional mould.



Jeremy

Sean Atterbury - n/a
8-Aug-06, 01:07 PM
Would this method work to make a fan duct?



Also, will the tape not react to the resin and stretch and stuff?

Jeremy - n/a
8-Aug-06, 02:05 PM
My guess is that you'd be better off making a foam duct and covering it with composite, leaving the foam inside. There is a website somewhere (can't find the link at the moment) that shows how to do this quite easily. It might work as described if you wanted to make a one-off duct interior mould, though you wouldn't need to melt the polystyrene out I wouldn't have thought.



Epoxy resin doesn't contain solvents, so doesn't have any effect on the tape or the foam at all. It doesn't stick to parcel tape either, so no release agent is needed.



This method won't work with polyester/vinylester resins though, as they do attack the adhesive on the tape, making it go wrinkly. Also, these resins will attack polystyrene foam, so it's likely that the mould will melt or distort, just from the vapour that gets through the tape.



I made a complex inlet manifold once, by carving foam to the required shape. I added bonded in alloy stubs to take the rubber connecting hoses. Here's a picture of the manifold on the back of a BMW R series engine. It's not too clear, but it's the black thing with the throttle body on (this was a conversion of an R100 to dual redundant fuel injection for an aircraft):







Jeremy

keith_b - n/a
9-Aug-06, 04:55 PM
Nick,



I made a fuel tank using West System Epoxy using the method described by Jeremy, as Aluminium welding is beyond my garage skills and learning how to work with composites would be more useful. It was my first foray with composites, and I haven't blown up yet.



I made an expanded polystyrene plug to fit loosely in the fuel tank cavity, including a sump, then covered it in packing tape. I chopped it up into 3 separate parts to build in baffles. I used an Aluminium plate for services such as filler cap, expansion and fuel feed, which has been bolted down using a proper gasket and gasket compound.



I used peel ply to keep a rough surface for fixing in the hull after the whole lot had set. I used a filler to thicken up the resin, talk to your supplier for the best one as I cannot remember which one I used off the cuff.



Get decent breathing gear.



Keith