Savannah/Ventura

[sfGnome]

Well, I’ve just ticked over 1000 hours building, and that’s just the time in the shed. All the hours on the computer investigating options and sourcing parts are not included. Probably about another 1000 to go. 
 

Funny thing I noticed yesterday. With the heatwave, it appears that all my heat shrink tubing has shrunk a little. The size that used to slide over a spade connector now just doesn’t. Now all I need is for the heat to help my gut to shrink a little… 😛

[Moneybox]

12 hours ago, sfGnome said:

Well, I’ve just ticked over 1000 hours building, and that’s just the time in the shed. All the hours on the computer investigating options and sourcing parts are not included. Probably about another 1000 to go. 
 

Funny thing I noticed yesterday. With the heatwave, it appears that all my heat shrink tubing has shrunk a little. The size that used to slide over a spade connector now just doesn’t. Now all I need is for the heat to help my gut to shrink a little… 😛

I've found it better to buy the multi layered heat shrink from someone like MM Electrical, an electrical wholesaler. It seems to have a resin or something in there so it not only shrinks but seals and bonds as well. Not easy to remove but I don't usually want to pull my soldered joins apart. It stays tubular as well unlike some of the cheap stuff that flattens and kinks easily.

[sfGnome]

Ok, here's a strange one for all you Savannah (and possibly Zenith?) people. I put a bit of fuel into each wing today for the first time - plenty sufficient for it to flow into the header tank - and it didn't. I spent about 15-30 minutes mulling this over and checking what I could without starting to undo pipes, and eventually I gave up thinking and pushed it back into the hangar. Hey presto, the fuel was in the header. Something about moving it started the flow, and then it flowed quickly as you'd expect. Interested to see if it was a blockage that had somehow moved, I pushed it outside and repeated the process. Again, no flow until the aircraft was moved, whereupon it flowed. 

 

Have you seen this? Is this a normal Savannah thing? I expect that if the header tank and pipes were full, it would not happen (ie fuel would flow as it was consumed), but I'm having difficulty making sense of it.

[Kyle Communications]

Does your header tank have a breather at the top?...The std Sav setup is wrong so you can get a vapour like lock. I only have all tanks feed into one pipe at the top of the header tank..the other entry at the top I do NOT connect to the plumbing system it goes to the top of one of the tank sides to act as a breather/normalizer so flow will alwys happen

 

[facthunter]

Might be worth checking your flow rate as you did initially. Sediment can settle in the Lower parts of the fuel Lines. Perhaps disconnect sections and blow out with compressed air. When you cut a section of rubber fuel line be careful there is Not a section (scarf) that can obstruct fuel flow.. Lodge in some Place. Nev

[IBob]

13 minutes ago, Kyle Communications said:

Does your header tank have a breather at the top?...The std Sav setup is wrong so you can get a vapour like lock. I only have all tanks feed into one pipe at the top of the header tank..the other entry at the top I do NOT connect to the plumbing system it goes to the top of one of the tank sides to act as a breather/normalizer so flow will alwys happen

 

Mark, by the time my kit was despatched in Dec 2014, ICP had corrected that, with instructions to connect the header with a breather, as you describe.

[sfGnome]

Yep, there's a breather on the top of the header that goes to the top of the LH tank.

[Kyle Communications]

Gnome if you do have a breather only pipe in the top of the header tank then it can only be that you have a low loop in your fuel hose. It basically has to run uphill at some stage to get from the tank to the header tank...this is the laws of physics. Every liquid will run down hill....so if it doesnt there must be some wierdo blockage. I did have a issue in the first few months of my aircraft that there was a intermittant blockage that was draining the carb bowls at high power. I finally found that a piece of plastic had come off the inside of the tank it was not a shaving it was a flat flake and it got lodged in the bend of the alu tubing that ran under the floor and upo to the firewall and it slowed the flow to my gascolator. It would be hard to imagine both tank feeds to have something like that. There must be a simple answer to the issue. I would have to look through my original XL build blog on here to find the pictures of my header feed system.... oh just had a thought before finishing this post...are the breathers on you tank caps working?...this could also be a issue if they are not doing their job or restricted. I got rid of the silly 3mm tubes from the fuel caps through the wings and used 6mm alu tubing in the tank caps. You will find a post on my blog why I did this...I couldnt access a full tank of fuel due to a insect getting into the 3mm breather tube

 

[IBob]

Hi Gnome, as Mark has pointed out, any undulations in fuel lines can have the effect of inhibiting initial flow. However, unless using solid lines, it is difficult to avoid some undulation, and I would think that is what you have.
But

You have also demonstrated (twice) that a minor movement of the aircraft is enough to establish initial flow, after which flow is as expected.

The Savannah fuel system is well thought out, and has proved to be very reliable in practise. In particular, the provision of a large header (with a level switch at the top to indicate if the header is not entirely full) works as an excellent buffer, should there be a momentary interruption of flow (unporting of tanks etc).

In short, provided you have laid your fuel lines flat, I would not be concerned at what you are seeing: if your experience matches that of thousands of Savannah owners, you will never see that low fuel indicator come on.

 

[Blueadventures]

To add to the good info, I had reduced fuel flow into my collector / surge tank (it's the 6 litre Savannah one in my Nynja) when my wing tanks (52 litres each) were down to about 30% full; at this time I had each tank feed line feeding to the nipples on the collector tank (My build was 2013 to 2015 when finished and there were two inlet nipples (10mm) in the top of the collector tank.  As my clear primary fuel filters are behind the seats I could see when no flow was occurring and the level in the collector tank would slowly reduce and then the low fuel light would come on.

 

I fixed this the same way Mark described.  I feed from wing tanks into one inlet nipple via a joiner 'T' for the tank feeds.  The second nipple was routed to the starboard tank via a 'T' at the top of the fuel contents tube where it enters the fuel tank to be the vent for the collector tank.

 

Works with no reoccurring issues.

 

My belief on why the fuel flow was reduced is the low fuel in the tank prevented the fuel flow under gravity (including some pressure from the fuel tank vent setup) was not enough to overcome the air trying to escape back up the hose from the collector tank and being a blockage.

 

Anyway; the need is for a dedicated vent line for the collector tank.  I am not familiar with the current batches of 6 and 18 litre collector tanks for the Savannah builds and the number of nipples fitted now -  three is the go.

 

Cheers.

[sfGnome]

Thanks. I’ll drain the fuel and check air flow through all the lines as a first step. Picturing in my mind’s eye, I can’t think of any undulations greater than the pipe diameter, but I’ll check for that at the same time. The advantage of that 18L header tank is that if I have flow problems, then I still have 1/2 an hour flight time plus 1/2 an hour reserve, which is comforting. 

[skippydiesel]

sfGnome - What airfield are you flying out of? 😈

[Kyle Communications]

Gnome definatly check the breathers for the tank caps too

[facthunter]

The deadly mud Wasp?.  Nev

[sfGnome]

Skippy - Shellharbour 

Mark - definitely clear, as I’ve only just installed them. 😁 Actually, I had the fuel caps off while I was experimenting, so I know it wasn’t a tank vent issue. That doesn’t discount a blocked vent line from the header tank, but if that was the case then I doubt that it would have flowed so easily once it started. 
 

Anyhow, I had anlso asked ICP, and their reply was that on first fueling, it is acceptable to pull the tail down to start the flow. Once it has started, the it will be fine, so I guess that matches my experience. 

[skippydiesel]

42 minutes ago, sfGnome said:

Skippy - Shellharbour 

 

Thanks - Thought you may be at Mittagong (S Highlands) just down the road from The Oaks  😈