3269 Fuel On The Outside 3270,71,72,73,75,76,79,95,3319

04-28-2008, 04:09 AM

Jim Small | 3269 Fuel On The Outside 3270,71,72,73,75,76,79,95,3319

Gentlemen,

I have been thinking about ways to keep All of the fuel out of All of the interior spaces of the Seawind. I don't want to service fuel system components in the cramped space under the wing spars. And I certainly don't want any leaks in there.

Here is an idea for discussion. Why not slightly enlarge the wing root fairings? An accumulator tank of up to 2 gallons could fit under each wing. Think of smooth saddle bags attached against the outside of the hull. This might also be a good place to put a fuel level gauge for each main tank. (My kit came with factory sealed wing tanks and it is not clear how to install a fuel level gauge.)

Next, dual redundant fuel pumps and a filter could be placed in fairings just aft of the landing gear openings. They would be easy to access from outside the aircraft. From there, fuel lines run up each side of the midbody to a Tee at the base of the vertical fin. The combined fuel line runs up the leading edge of the vertical tail. At the top, curve it forward to join the engine cowling forward of the firewall.

The installation will require an additional fairing on the leading edge of the vertical tail and over the midbody deck sufficient to hide the fuel lines. Added drag should be minimal. It might require electric fuel valves.

What do you think? - Jim

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Posted by John Ricciotti on April 29, 2008 at 03:23:37:

In Reply to: Fuel on the Outside - Discussion posted by Jim Small on April 28, 2008 at 17:04:08:

Hi Jim,

I like your thinking about fuel on the outside. The nice part of this group is that we have a lot of great minds to find the best ways to do things.

The only thing that I can think of for problems is weight. This airplane is way too heavy right now. Every ounce, especially aft, is an issue. The fairings would also have to be tough enough for a water environment and the subsequent impact loading of a water landing/waves.

I'm sure there are design ideas to address most of these issues. The best part is you have brought up the subject. We have already lost two members to fuel leaks in the cabin so I think your ideas are worth a healthy discussion and possibly some changes to our design.

Thanks for bringing it up!! Regards, John

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Posted by Tony Jurcan on April 30, 2008 at 11:35:16:

In Reply to: Fuel on the Outside - Discussion posted by Jim Small on April 28, 2008 at 17:04:08:

Jim, Some thoughts for your discussion. while it would be beneficial to locate All the fuel system outside, the real problem, as you indicated, is to service fuel system components in the confined interior space. Fuel lines running through the interior is quite common. The Lake Amphibian has a boost pump under the main tank located in the interior, but the filter is outside in the pylon. I like the concept of locating the filters and possibly the fuel pumps outside in the wing root area. The accumulator tanks could be eliminated and fuel lines could follow to standard path up through the vertical tail. Locating fuel tank control valves and interconnecting piping could prove to be a challenge. At this stage I am committed to using duel header tanks mounted in the interior. Tony Jurcan

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Posted by Jim Small on April 30, 2008 at 15:19:38:

In Reply to: Re: Fuel on the Outside - Discussion posted by Tony Jurcan on April 30, 2008 at 11:35:16:

Tony, Thanks for the very encouraging comments. I understand that those farther along in the build cycle have already committed to some version of the fuel system. For those of us who are newer or slower, your comments are very helpful. Jim

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Posted by Mike on April 30, 2008 at 16:51:56:

In Reply to: Re: Fuel on the Outside - Discussion posted by Jim Small on April 30, 2008 at 15:19:38:

Hummmm, Interesting thoughts.....

While I had the wing open for repairs, I had thought about adding a rib inside the main fuel tank approx 4 inches from the root to prevent the fuel from sloshing more than it does and therefore diminishing the amount of air that enters the main fuel line. At this point I could have eliminated the header tank, otherwise experience has told me one is needed to bleed of the air in the fuel lines. Depending where the pumps and filters are placed; one could easily add access hatches. There is room in the rear of the wing if the inspection hatches were enlarged. What would be the affect on the pumps in the cold weather? One has to be careful of the CG, although most likely not going to change considerably.

I decided to move all the fuel hardware out of the cabin and into the rear by using electric ball valves. The valves can be placed anywhere in the travel I want for fuel management (the mains draw at a different rate) or when full open/closed an led tells me the position. The cabin is almost fireproofed.

If you have not covered the wings...take note of the alert that was issued back in 1993..? Before covering the tanks one has to add glass to the top and bottom of the spar to prevent leaks.

Side note: DONT LIFT BY THE WINGS..!! I have leaks to prove it..wait...I had leaks..!!

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Posted by Tom Thunnell on May 01, 2008 at 18:43:16:

In Reply to: Re: Fuel on the Outside - Discussion posted by Mike on April 30, 2008 at 16:51:56:

I am eliminating the header tanks. I have installed sumps of approximately 3 gallons at each wing root that positively seal with a metal flap.The factory installed rubber flaps do not completely seal and there are additional drain holes to allow fuel to flow in each of the ribs. I installed a new rib with the sump flap and cpmpletely sealed it. I also am eliminating the finger strainers in the wing roots and replacing them with a large exterior filter that is easily serviced and accessible. I fabricated a large area strainer,about twice the area of the finger strainers, of #30 stainless mesh which is approximately the mesh size of the finger strainers to install in the main line before my pumps.

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Posted by Mike on May 02, 2008 at 17:06:26:

In Reply to: Re: Fuel on the Outside - Discussion posted by Tom Thunnell on May 01, 2008 at 18:43:16:

I have a stainless flapper in the 1st rib in the wings. Deleting the finger strainers at the wing is a good idea; now you can install 1/2" fuel lines from the wings to the interior. Check with planemakers and the info on this site for strainer/filter sizing (fuel posts)...sounds like the size you are installing is to large for fine particulates prior to entering the pump.

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Posted by Tom Thunnell on May 03, 2008 at 22:15:27:

In Reply to: Re: Fuel on the Outside - Discussion posted by Mike on May 02, 2008 at 17:06:26:

Mike: I am just using the filter described to eliminate the chunks and take the place of the finger strainers. Additionally before the pumps I am using Airflow Performances 125 micron pleated stainless steel filter in conjunction with their dual pump system. TT

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Posted by BUD GUSTIN on May 18, 2008 at 13:16:50:

In Reply to: Fuel on the Outside - Discussion posted by Jim Small on April 28, 2008 at 17:04:08:

My comments may not men much as I will not be using gasoline for fuel; but, for what it is worth..........I would NOT under any circumstances service a standard Seawnd fuel system without a window fan ( or such) to give a great supply of fresh air for ventilation. I also would not go to the extremes of re-routing the fuel system to avoid fumes in the interior. Your ideas only address the fumes as noxious.but, there is enough volume in the airframe to blow the airframe (and you) into the next county when you inadvertantly cause an arc. In that regard, your fan should blow fresh air into the area rather than extract foul air out as the fan moter could be an ignition source. The hull of the Seawind is a big bowl which, without ventilation, will collect a lot of heavier than air fumes. This is, and always has been, a very serious point of marine inspection of vessels. As far as the finger strainer goes; I would NOT use them until you are certain ALL the particles of resin are out of the system.I was at the ariport when Dick Silva was doing a 100 hr. inspection and he showed me that his finger strainer was packed SOLID with resin particles.......kind of a "no flow" situation. Planemakers rock the wings with a partial load of fuel to help eject the resin and catch the results in a paint strainer cup.

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Posted by Doug Fir on June 16, 2008 at 04:25:55:

In Reply to: Re: Fuel on the Outside - Discussion posted by Tom Thunnell on May 03, 2008 at 22:15:27:

Tom, What you describe sounds interesting. Can I assume you have two pumps in each wing root? Also you implied you are attempting to get a very good seal with a metal flapper valve? Does this mean 100% seal or some leakage (say a gal per hour) can be tolerated. My concern is also that the rubber flapper valves supplied with the kit are not functional and I`m looking for another alternative. Cheers Doug

10-31-2011, 01:51 AM

Rusty | Vapors in the fuselage

Bud: thanks for reminding us all about heavy vapors and ignition sources. I was going to use a Holley pump for tank balance by reversing the leads mounted low inside. I have no fear of the Andair pump I just received, but the Holley is bound to be a brushed motor. They sell either an automotive or marine version. Do I trust their marine version? Guess that Holley better be in the wing.

Boat exhaust fans mount high with a suction hose to the bilge. Do they make them with brushless motors? Bilge pumps mount low. Are they brushless?

On wobble pumps: Christianson once said at a field trip to the old Cristen Eagle factory near Hollister, that one need not worry about enough capacity---a hand on the knob of his pump and quivering fear would take care of it.