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This was one job I hadn’t really been looking forward to but I’ve never really worked out why until I started thinking about it. I soon realised that there are no positive and secure location points for fixing the tanks. The Build Manual and Video are typically wishy washy offering a few dimensions that don’t necessarily relate accurately in practice. There are some great ideas on the ROG site and other (mostly US) owners sites but the best of these involve some welding to the frame!!! - something that we can’t even think about in the UK. I had to come up with a method of securing the tanks in the optimum position using (basically) the recommended methods.
All methods require the tanks to be raised by about an inch on the support ledges on either side of the frame - the only mounting datum supplied. I didn’t fancy the block of wood technique - the tank wasn’t parallel to the mounting ledge anyhow, so I thought I’d kill two birds and make a GRP Tray ‘Socket’ for the bottom of the tanks supported on pillars of filler. I estimated this would be no heavier than an inch thick piece of hardwood.
I started by wrapping the bottom of the tank with a sheet of 1/16 in thick foam sheet and securing it with tape. This foam would eventually be used to line the tray.
Then a layer of - you guessed it- Packing Tape as a mould release. I made this as smooth as possible, covering all the foam and three inches up the sides of the tank.
I used 4 layers of GRP chopped strand matting in single pieces.
And formed them over the bottom of the tank.
Here are the two trays, trimmed to approximately one inch depth with the holes cut for the fuel outlet unions.
I stuck 1/2 inch of foam rubber to the fuel tank front face to space it from the seat back and held the tanks in position with some small ratchet straps.
This shot shows Packing Tape Mould release (the brown stuff) on the top of the support ledge and around the frame tubes. I taped the GRP trays to the bottom of the tanks and shaped some body filler into support columns. I made and fitted the long securing straps before disturbing the tanks position.
The finished item. Two counterbored screws hold it to the support ledge.
The filler pillars have been blended into the GRP tray then dressed and tidied. It’s difficult to see in this picture but the filler pillar locates in the angled corner of the support ledge. You can also see the cut away for the fuel outlet union.
The top forward strap securing clamp is pretty much as recommended but it’s a bit daft having the short thread on the eye bolt. I’ll run a die down this to extend the tightening range later.
This is the clamp before rolling.
There’s not much that can be done with the rear securing band without welding some locations onto the frame so I chose to try and at least make the standard method work as best I could. I made the strap as tight a fit around the tank as possible.
I made saddle clamps for securing the rear strap to the frame but instead of just twisting the strip to compensate for the angle change, I made a cardboard template and cut some dog-leg shapes from steel sheet.
These folded at an angle on one side to mount parallel to the rear strap. This picture shows a nut in-between the four layers of steel to help with making the template. This will be removed on final assembly.
And this is the passengers side with temporary bolts - shaped but not yet dressed. A good suggestion from the ROG is to add a hose clip around the frame tube to prevent the clamp sliding down.
This rubber channel is perfectly sized for the 3/4 inch fuel tank straps and clamps. It has a few benefits over the simple rubber strip supplied by Rotorway. Firstly, you don’t have to glue it to the steel straps - it’ll hold itself in place and it won’t slip or roll off. Also, because it rolls around the front side of the straps it will prevent the steel chafing the body panels and the frame if they make contact. If cut half way through with a sharp knife like this it’ll fold to a perfectly sharp angle.
Here it is in use under the forward top clamp.
I’ve also extended the cut thread on the eye bolt to almost it’s full length to extend the useful tightening range
The insulation went on pretty much as expected. I found the plastic handle of my scissors very useful in pressing down the tape. I’m still not too convinced about exactly how sticky this stuff is. We’ll see.
I used the off-cuts of insulation to fill in the triangular gap in the corner.
FUEL TANK MOUNTING UPDATE
I was quite proud of my mounting straps and brackets - that is until I tried to refit the upper rear body panels. The passengers side was fine with sufficient clearance between the rear end of the tank and the body panel. But the rear of the Pilots’ side tank held the panel away from the tail boom by almost an inch. - I must have missed the section in the Build Manual and Video that instructs you to install the fuel tanks as part of the body mounting procedure!! There’s not much room for error in this area. It appears that maneuvering the body panels to get adequate clearance around the fuel tanks is as important as any other body fitting datums. Whatever, it’s easy to kick my own ass for a such a fundamental oversight but I’ll console myself with the thought that there’s very little on this ship that is symmetrical, so I set about finding a solution.
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This is the offending part of the tank. The body panel was touching on the heat insulation and the securing band in the area of the lower white mark. First step was to remake the securing band but this time, to form it to follow the tapered shape of the tank. I beat it, ‘Cooper - style’, around a steel bar until it was shaped like the hoop around a wooden beer barrel, tightly hugging the tank where it had previously made contact only on the forward side.
Here’s the working version of the remade saddle clamp. I cut one flat oval of 3 mm steel, drilled and countersunk from behind and inserted a stud that would allow me to pull the rear of the tank inwards and upwards as the securing nut was tightened.
And that’s it - In and Up just about as far as it will go. The body panel just clears and all in the garden is rosy again - phew.
This is the ‘T’ the returns fuel to the top of both tanks. I secured it to the seatback using two P clips fixed to two ‘standoff’ bolts with screwcups on the cabin side and penny washers on the back. Strong and secure.
FUEL TANK SEALS
Following a disturbing post on the ROG website Rotorway issued a Mandatory check directive to all owners of recently delivered kits to check the rubber ‘O’ Ring seals on the fuel tank outlet unions. It seems that some ships were supplied with seals made from the wrong rubber. When immersed in fuel the rubber would absorb fuel then expand and degrade. I removed my seals and left them overnight immersed in fuel. Sure enough -they expanded over 6mm in diameter and became very soft and mushy.
The new replacements are on the left and centre of the picture. Far left - new virgin seal, Centre - new seal after 24 hour fuel soak, Right - Old Seal after fuel soak.
If you’re interested in dimensions. The dry new seal measured 29 mm diameter and 10.26mm thick. The soaked new seal measured 29.8 mm diameter and 11.06mm thick (so it still swelled a little). And the soaked old seal measured 34.5 mm and 11.68 mm thick!! Sorry about the Metric measurements.
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