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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 5:26 pm
by Mike Davis
Hi Warren, it doesn't seem to me like you would need to drill holes along the entire length, just a couple at the inboard end since it is lower the fuel/water will eventually run there and then through to the next stringer until it finds its way to the bottom corner and the water drain. And from what MAM says below that shouldn't be anything to worry about.

Mike
----- Original Message -----
From: Warren Montgomery (monty@emirates.net.ae)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Monday, April 15, 2002 9:39 AM
Subject: Re: SR3500 Split Tanks 40/20


Re: SR3500 Split Tanks 40/20
Mike,
Regarding drain holes in stringers.
=======================
O O O O
The following is reply from MAM
Quote:
The lower stringers are in tension (unless you go inverted or receive a massive negative loading) and are less critical.
So personally I don't think this will matter if you stay with 1/8 holes.
Unquote:
Now to decide what to do???????????????????
Warren
Dubai, UAE
SR029

SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Warren Montgomery
Dang Mike! Now you got my mind going in circles!!!

Why I didn't split the tanks when I first upgraded to 120s I don't know. I already had the 5th rib all sealed off.
I've closed one wing and am nearly ready to close the second but am now thinking maybe the split tanks are the way to go.
I've got extra fuel probes, flanges, drains, etc so only need an extra set of fuel caps and ribs as I already cut all the baffle holes.
I can reopen the bottom skin on the closed wing and change out the 5th rib and add the bits. I'm good at re-doing rivets!!!
It's now or never!!

What I'd like to do is split the 120 into 2x40 Inners and 2x20 Outters.

Rib
Replace 5th rib with solid rib. Install stringer gussets with rib temporarily held in place with scrape.

Fuel Feed
Run a ~3/4" to 1" alum tube from the re-sealed 5th rib to an extra outlet on the root rib sealed in place with extra flanges on the inside
of rib 5 and root rib. Nylon gromits used as guides on 2nd, 3rd and 4th ribs.
Have this exit somewhere aft of the Inner tank outlet and place the strainer on the root flange.

Vent
Vent outter to outter and inner to inner.
Install ~1/2" alum tube as above from root rib to 5th rib. This would have to be about 5" aft of the main spar as I'd need to clear
the main tank vent, main tank fuel probe, stringer and main tank fuel cap.

Probe
I have already cut out access covers on the wing skins in the 7th bay, fuel tank typical.
Mount probe on 7th rib, tip side of outter tank.

Extra work and cost aside, what are the groups thoughts on the split tanks????

Warren
Dubai
SR029




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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Scott & Leere' Aldrich
Warren, for me the extra weight and complexity of double probes, caps,
drains, etc., would outweigh the benefits.

Scott
SR#174





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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Mike Davis
Didn't mean to make a bunch of extra work for you Warren! I've pretty much
decided to split my tanks one way or another though. I figure that a 30/30
split though will give me 4 hours duration on the inboard tanks alone with a
solid 1/2 hour of reserve... and that's figuring at 13 gph which is a little
higher than I should see with the Subaru. That's enough to go just about
any where in Alaska from Fairbanks... and if there may be a problem getting
fuel at the other end, well then I'll just fill the outter tanks too!

Mike
195SR

P.S. I think you just like building way to much Warren... you know you
could finish this project and then start another one! :-)

----- Original Message -----
From: "Warren Montgomery" <monty@emirates.net.ae>
To: <murphy-rebel@dcsol.com>
Sent: Friday, April 12, 2002 4:14 AM
Subject: SR3500 Split Tanks 40/20

Dang Mike! Now you got my mind going in circles!!!

Why I didn't split the tanks when I first upgraded to 120s I don't know. I
already had the 5th rib all sealed off.





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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Warren Montgomery
Mike,
I weighed all the parts and the system will weight 955gms + per wing or 2.1lbs.
Add misc. for a total of ~4.5lbs.
Cost looks like it'll run about 650 USD. I'm short by about 300USD in parts but at least I'd be putting the 350 worth I have to use.

1/2"x48" tube 125g 3US
3/4"x48" tube 200g 5US
Brass Fuel valve
& fittings 175g 23US
Fuel cap/flange 100g 50US
Rib W-173 +? 48US
Drain 015g 11US
3x Lrg flange 040g 21US (3)
4x Sml flange 020g 28US (4)
Strainer 020g 7US
Probe 200g 116US
Rib Gussets 060g
Total 955g 312USD per wing

Plus: wire, nylon fittings, fuel line, x-vent line, proseal, rivets
Less: holes drilled in skins.




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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Mike Davis
That seems pretty reasonable to me... thanks Warren

Mike

----- Original Message -----
From: "Warren Montgomery" <monty@emirates.net.ae>
To: <murphy-rebel@dcsol.com>
Sent: Saturday, April 13, 2002 10:35 AM
Subject: Re: SR3500 Split Tanks 40/20

Mike,
I weighed all the parts and the system will weight 955gms + per wing or
2.1lbs.
Add misc. for a total of ~4.5lbs.
Cost looks like it'll run about 650 USD. I'm short by about 300USD in
parts but at least I'd be putting the 350 worth I have to use.
1/2"x48" tube 125g 3US
3/4"x48" tube 200g 5US
Brass Fuel valve
& fittings 175g 23US
Fuel cap/flange 100g 50US
Rib W-173 +? 48US
Drain 015g 11US
3x Lrg flange 040g 21US (3)
4x Sml flange 020g 28US (4)
Strainer 020g 7US
Probe 200g 116US
Rib Gussets 060g
Total 955g 312USD per wing

Plus: wire, nylon fittings, fuel line, x-vent line, proseal, rivets
Less: holes drilled in skins.


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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by lawsonb
Hey Mike,

Wow! The cost of these simple items on planes still amazes me.
Anyway, I know nobody "likes" automotive stuff on a plane, but
Princess Auto has 12volt in-line fuel pumps for 89 Canadian, regular
catalogue price. That would give you some fuel management control
that I haven't read into your ram-air idea.

I realize you are trying to do this compartmentalizing by just
continuing the pro-sealing, but what about adding just one rib about
6 inches over to separate the two tanks, then you've got room to work
at different methods and allows two top tank skins (one per tank) of
smaller size than one big one, and easier to proseal than trying to do
a huge one.

One more quickie. I don't know about the SR, but on the standard
Rebel, one end of the tank is the root, and the other end is at the
third rib. The wing strut attach area is between the fourth and fifth
ribs, admittedly forward of the proposed tankage area, but have you
considered the wing loading and flexing if you do what you are
proposing. Just a thought.

Brian Lawson,
Windsor, Ontario.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
On Sat, 13 Apr 2002 22:35:32 +0400, you wrote:
Mike,
I weighed all the parts and the system will weight 955gms + per wing or 2.1lbs.
Add misc. for a total of ~4.5lbs.
Cost looks like it'll run about 650 USD. I'm short by about 300USD in parts but at least I'd be putting the 350 worth I have to use.

1/2"x48" tube 125g 3US
3/4"x48" tube 200g 5US
Brass Fuel valve
& fittings 175g 23US
Fuel cap/flange 100g 50US
Rib W-173 +? 48US
Drain 015g 11US
3x Lrg flange 040g 21US (3)
4x Sml flange 020g 28US (4)
Strainer 020g 7US
Probe 200g 116US
Rib Gussets 060g
Total 955g 312USD per wing

Plus: wire, nylon fittings, fuel line, x-vent line, proseal, rivets
Less: holes drilled in skins.


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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by mike.davis
Hi Brian, considering I intend to put a Subaru engine in my airplane, I'm not
to adverse to automotive stuff on my plane. What I was looking to do with the
ram air system is have a non mechanical/electrical solution. I like the
simplicity of the gravity feed system, and I would love to find a solution
that works without any pilot intervention. I may end up doing what Warren
suggested with separate plumbing, but that another valve that has to be pilot
actuated to make the system work... I like the idea of put fuel in the tank
and forget about it, it will find its way to the engine!

As far as wing loading, we are not really talking about modifying the
wing/tank design, just not drilling baffle holes in one of the tank ribs
effectively splitting the tank in two. The tank size and construction would
otherwise be build exactly to Murphy's instructions. By keeping the rib of
your choice be it the 3rd or 4th whole, and fully sealing it off you now have
two tanks in the same space as one large one. This should not effect wing
loading at all. On the other hand, while your idea of splitting the tank skin
and tanks by 6 inches or so may make installation easier, but it would take
one 32 thousandths solid tank skin and split and separate it which I believe
would impact the wing's strength.

I'd love to be able to connect the outter tank to the inner with nothing more
than a check valve, but if I cannot demonstrate that this will work
effectively, then I will plumb the outter tank through the inner and have
separate shut off valves on the root rib like Warren has described. I would
imagine you could also run a small like through the inner tank to a separate
set of sight guages if you didn't want the complexity or expense of electric
fuel senders and guages also.

Mike
195SR

On 4/14/2002 12:56 PM, MURPHY-REBEL@DCSOL.COM wrote to MIKE DAVIS:

->
->
-> Hey Mike,
->
-> Wow! The cost of these simple items on planes still amazes me.
-> Anyway, I know nobody "likes" automotive stuff on a plane, but
-> Princess Auto has 12volt in-line fuel pumps for 89 Canadian, regular
-> catalogue price. That would give you some fuel management control
-> that I haven't read into your ram-air idea. =20
->
-> I realize you are trying to do this compartmentalizing by just
-> continuing the pro-sealing, but what about adding just one rib about
-> 6 inches over to separate the two tanks, then you've got room to work
-> at different methods and allows two top tank skins (one per tank) of
-> smaller size than one big one, and easier to proseal than trying to do
-> a huge one.=20
->
-> One more quickie. I don't know about the SR, but on the standard
-> Rebel, one end of the tank is the root, and the other end is at the
-> third rib. The wing strut attach area is between the fourth and fifth
-> ribs, admittedly forward of the proposed tankage area, but have you
-> considered the wing loading and flexing if you do what you are
-> proposing. Just a thought.
->
-> Brian Lawson,
-> Windsor, Ontario.
-> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-> On Sat, 13 Apr 2002 22:35:32 +0400, you wrote:
->
-> >Mike,
-> >I weighed all the parts and the system will weight 955gms + per wing or =
-> 2.1lbs.
-> >Add misc. for a total of ~4.5lbs.
-> >Cost looks like it'll run about 650 USD. I'm short by about 300USD in =
-> parts but at least I'd be putting the 350 worth I have to use.
-> >
-> >1/2"x48" tube 125g 3US
-> >3/4"x48" tube 200g 5US
-> >Brass Fuel valve
-> >& fittings 175g 23US
-> >Fuel cap/flange 100g 50US
-> >Rib W-173 +? 48US
-> >Drain 015g 11US
-> >3x Lrg flange 040g 21US (3)
-> >4x Sml flange 020g 28US (4)
-> >Strainer 020g 7US
-> >Probe 200g 116US
-> >Rib Gussets 060g
-> >Total 955g 312USD per wing
-> >
-> >Plus: wire, nylon fittings, fuel line, x-vent line, proseal, rivets
-> >Less: holes drilled in skins.
-> >
-> >
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->
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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Warren Montgomery
<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> Brian,
Okay now I see what you're saying, have a dry area between the tanks. MAM was very clear that they wanted the new .040 longer skin 74 1/2" when increasing the tank size. I had asked about just splicing in a .040 for the extension but apparently the compression loads are quite high here.
Yes the strut will be part of the tank. MAMs mod has a baffle to keep the strut dry and allow inspection. I installed the strut with pro seal and it will be wet. Have the fuel cap to use as inspection hole and std fuel tank inspection cover on the bottom if I have to actually remove one of the bolts.
3, 4, and 6 Bay tanks are all approved by MAM.
Regards,
Warren
[quote] [quote]Subject: Re: SR3500 Split Tanks 40/20
I realize you are trying to do this compartmentalizing by just
continuing the

SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Warren Montgomery
Re: SR3500 Split Tanks 40/20

Mike,
No matter how we plumb split tanks we'll both have the same problem. That is with the stringers.
These will carry through the outter tank and trap about 1/2" of fuel. Even with the tail dragger there'd be
about a pint to a quart trapped in front of each stringer when on the ground.
I'm not worried about the unusable fuel but rather the water, which is one thing we're trying to avoid in
the first place. Either small drain holes need to be drilled through the two stringers or you'd need
three water drains. I'll contact MAM and see if I can get some advice on drain holes.

Warren
Dubai, UAE
SR029





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SR3500 Split Tanks 40/20

Posted: Fri Feb 17, 2012 10:04 pm
by Warren Montgomery
<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> Re: SR3500 Split Tanks 40/20
Mike,
Regarding drain holes in stringers.
=======================
O O O O
The following is reply from MAM
Quote:
The lower stringers are in tension (unless you go inverted or receive a massive negative loading) and are less critical.
So personally I don't think this will matter if you stay with 1/8 holes.
Unquote:
Now to decide what to do???????????????????
Warren
Dubai, UAE
SR029

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