Strake/Fuel System Construction

Date: October 2002

Chapter: 14.0 Fuel System

Section: Fuel System

Long-Range Fuel Tanks - Optional

Section 14.1 Transfer Template

October 18, 2002 - Chapter 14.1.1 - "Transfer Template"

This section is only needed if you can't (due to space concerns) can't mount the wings. Well, we can only mount one at a time, but we can mount them (props to my home dog Trenaman for the assist) in the garage.

Pilot-Side Wing Attached

Section 14.2 Lower Fuel Strake

October 19, 2002 - Chapter 14.2.2 - "Preparation"

To prepare for the pilot side strake fitting, we leveled the plane fore and aft, then installed the pilot side wing. This was a bit of a trick, and to save our locking nuts we got some 1/2"-20 nuts from Home Depot. After much trial and error, with a little Vaseline the went in. We then propped the outboard trailing edge with a bottlejack from Lowe's to get the wing incidence correct.

Twisting Pilot Side Wing into Position

Checking Pilot Side Wing Incidence

October 19, 2002 - Chapter 14.2.3 - "Lower Strake Alignment"

OK, get ready because this is going to be frustrating. Get the doors on the plane (all other work ceases). Get the plane level up and back and side to side. Then you need to project a line from the underside of the spar to about 78" forward (onto previously mentioned doors). This line must be level, so pick you best midnight engineer tricks (1. Straight edge with torpedo level, 2. water level, 3. Snap a chalk line with a string level) and compare the marks. Note that they are all different and begin cursing uncontrollably. Take break, play with cat....

Eventually I decide that the water level was the best (only accurate) way to do this. I then took several measurements (pilot side strake to pilot side door, cp strake to sp side door, pilot door to cp door, etc.) until they were repeatable. Did I mention that this dimension is CRITICAL to the proper flight characteristics of the plane (the strake is a lifting surface, and you want the inboard section to incur aerodynamic stall last....). With the previous line fixed, we draw a new line 2 7/8" above this line, which should give us -.5 degree angle of attack.

Fitting Pilot Strake to Incidence Mark on Door

Fitting Pilot Strake to Fuselage

Fitting Pilot Strake to Wing Root

Fitting Pilot Strake to Wing and Spar Bottom

Next we fashion a block with a pencil hole in it for take contours of the fuselage and projecting them onto the strake which has been propped into position. Another handing technique from the videos is to take a level and find the vertical tangent line on the strake and wing root for fitting. You gradually work your way down until the strake lays nicely up against the fuselage. I actually started with the outboard side basically parallel with the wing, then worked the inside (all the while making sure you have at least an inch in back to cover the spars with). This whole process has a high potential for error so it took me a couple of nights to get it were I was satisfied.

Once the dry fit is good, you mark the line were the strake meets the spar, then pull the strake and mark a line about 1/2" forward of this and remove the inner skin. The foam is then removed from outer skin, and the foam edge is beveled for the coming layup. Once the inner skin is cleaned, we roughed up 2" of the inner skin, wet out the area and covered the foam with micro and laid 2 BID on this area.

Removing Foam from Pilot Strake Outer Skin

Glassing Pilot Strake-to-Spar Bonding Surface

October 19, 2002 - Chapter 14.2.4 - "Cutting Out Lower Baggage Access Openings"

This is a fairly un-nerving step, unless you like cutting huge holes in very expensive things. Fortunately I'm beginning to really believe that I could fix a major fiberglass mistake. The instructions say to cut an opening 18 inches forward of the gear bulkhead (that's an easy measurement to make on the outside of the plane!) to 8" aft of the door cutout (at the top? the door slants, guys...). As you can see in this series of pictures, I propped the strake up off of a long folding table with some spare foam to fit into position, marked the lines, and cut the opening. I cut it a little small and filed it down, then rounded the inside radius for later glassing.

Opening the Pilot Strake Baggage Opening

Also in this step, I sanded all of the primer off of the fuselage contacting surface areas, and inside the fuselage where the baggage area layups will go, as well as on the strake inside and out.

October 19, 2002 - Chapter 14.2.5 - "Lower Strake Half Glassing"

Next we bond the lower strake to the center spar section. This is done with a thick mixture of structural adhesive in between the two parts. Since the strake skin crosses from the center spar onto the wing spar, after mating I shined a high intensity light down between, and marked and cut a line to separate the wing from the strake for removal. Also, in order to support the strake skin tightly without moving the plane we built a jib similar to the video out of all-threaded-rod and a 2"x4" block. Be very careful to cover the board with plastic and Vaseline the rod or it's never coming out again! Once the structural cured, we micro-glassed a radius and laid 2 ply of BID onto the strake-to-spar junction.

Glassing Pilot Strake-to-Spar

Next I Bondoed the nose of the strake so that I'd have a stable platform for the next set of operations. I was a little hesitant to use the Bondo, but it turns out to better in many cases than hot glue. It holds much better, and is so brittle usually a firm tap with a sharp screwdriver or chisel will easily remove it from the mated surfaces. Highly recommended.

Pilot Strake Bondo

Next the upper and lower strake-to-fuselage areas are laid up with 2 ply of BID, with a micro-glass layup anywhere there's a sharp corner.

Lower Pilot Stake to Fuselage Bottom Layup

Lower Pilot Stake to Fuselage Top Layup

Pilot Lower Strake Inner Baggage Layup

Pilot Strake Lower Inner Baggage Lay-Up (Inside View)

Now, before we can do anything with the baffles, bulkheads, and other internal work on the strake, we have to go back and repeat the tedious fitting work on the top skin. The fun never ceases.... Shampoo, Rinse, Repeat,....

Section 14.3 Internal Strake Baffles

October 26, 2002 - Chapter 14.3.2 - "Baffles and Bulkheads"

This is going to seem simpler than it is, and there's no way around it. There's a lot of sanding, fitting, removing, sanding, etc. that I simply can't do justice here. Also note that after pleading with the factory, apparently I'm going to have to turn the plane upside down to do the final sealing work on the fuel strake (major yuck), and then put in the last 2 bulkheads. This is something that it appears some other folks aren't doing, but without Papel Dispensation, I going to do the way the man says. {end of lecture} Also note, the bulkheads seal fuel and get 2 plys of BID, baffles just reduce the sloshing and only get one (in case I forget to mention it later), and they have "mouse-holes" top and bottom for fuel and vapor flow. OK, on to the work.

First we took the 4'x8' (yes, FEET) sheet of 3/8" dyvinicel foam, buttered it with micro and glassed it with one layer BID on top of a sheet of plastic. Cure, rinse, repeat... or flip it over, butter and glass that side. Then you have to cut out these templates from a huge sheet of kraft paper the factory gives you and begin the back-breaking work of figuring out how to get 2 of each (I began to feel like Noah) out of this one sheet of foam. It can be done, and with a reasonable amount of throw away, but it takes a little thought a bunch on time on your knees with a Sharpie (they should have me doing their commercials....).

Laying Out the baffles

The Finished Product - Baffling!

Once you have the baffles, you can begin to test-fit them onto the strake. Surprise! They're HUGE, make note to find the sanding block tomorrow, go to bed.

Pilot Baffle Test-Fitting

Note the little 1"x1" right triangles, these were very helpful in maintaining the proper alignment through maddeningly repetitive sand, remove, fit cycles.

November 2, 2002 - Chapter 14.3.3 - "Install Strake Baffles"

Once you've located the baffles all you have to do is sand them down to exactly match the upper strake skin. You start by working from the outside in, so you get the bulkhead nearest the wing root to match the wing properly. Again, you have to repeatedly check that the wing still at the correct incidence and that the plane is level. I ended up sanding all of my baffles a little short so I could get them perfect by taping the mating areas on the top strake, level micro-glass on top of each, and the mash it down to get it spot-on. Here's a shot of the layup process.

Pilot Rear Bulkhead Layup

Pilot Baggage Area Fuel Bulkhead

Pilot "Mouse Holes" for Draining/Venting

And here's a shot of the leading edge clecoed tight into position and the top weighted down to squeeze the schoomey level.

Micro-Glassing the Pilot Baffle Tops

As I said, this does not do this multi-week period justice. Next we need to Jeffco the tank to seal it up. Jeffco is a funny substance, an thick grey epoxy that is still surprisingly runny. It sets up fast, except when you want it to. We spent the better part of a day just doing the pilot side tank, and ended up applying it too think because we over-estimated the 'tackiness' of the Jeffco when we began to apply the second coat. We did mix a fair amount of Cabosil in with the Jeffco, which makes it a little thicker (to stick to the sidewalls), and reportedly lengthens the cure time somewhat. This stuff stinks and will give you a headache, and gets very warm. All and all, this is a great 2 person job. Oh, avoid surprises and plan to ruin a set of clothes.

Pilot Fuel Tank Jeffco Sealant

November 15, 2002 - Chapter 14.3.4 - "Bulkhead Fuel Fittings"

We'll be installing Vance Atkinson's very nice lighted fuel gauges, which come with separate instructions to open up about 1/2 holes in the face of the bulkhead and fill it with flox. Then you sand everything up nicely, bond the white backing plate to the bulkhead with flox made from one of the clear epoxies, drill a 1/16" hole for the top and bottom of the sight gauge. Then stick the float to the viewing cover with some grease, and transparently flox it onto the base, then BID over the whole unit with the clear epoxy. Here is a picture of the gauge in place.

Atkinson Fuel Sight Gauge, Pilot Side

Next we install the fuel drain tubing. This is 3/8" tubing that comes out from the bottom rear most corner and bends to follow the center section spar. I elected to put a fitting in this line, and to BID it in place for better reliability and maintenance, and to make it easier to work on the sump tank.

Fuel Drain Line, Bent and with Fitting

Fuel Drain Line BID into Place, Pilot Side

And finally I installed a 3"x3" aluminum hardpoint and a Westach capacitive fuel probe for indication on the instrument panel.

Westach Fuel Sensor, Pilot Side

Further, we intend to install a light gauge scale next to the fuel gauges. We originally thought that Superior Panel would make these for us, like they did the overhead switch panel, but after many promises they did not come through. Here is our attempt at a homemade solution that we saw on someone else's website (Vance's?) where a plate of acrilic has the markings made with decals. Then the back side is painted white, an the front side painted to match your interior color, such that when a lamp is shined through the acrylic it illuminates the exposed legend. Unfortunately we weren't satisfied with this first attempt, so we're exploring other options.

Calibrating the Fuel Gauge

Making the Fuel Scale

I wasn't pleased with my fuel gauge calibration (electronic or sight glass), so I recalibrated them before first flight. I jacked the plane into it's '0-degree of incidence' angle to determine the unusable fuel level. It turns out about 2 gallons are not usable because my pickups are in the back of the tank. The factory now instructs folks to use a side pickup (coming in through the fuselage side wall), and this would get much lower into the tank low spot. I also find that since I had to build my strakes one at a time, my left tank is a little larger than my left tank. This will only be a factor when they're completely full, which will be very rare. Note that 0 is well above the bottom of the sight glass.

Recalibrating Sight Gauge

November 28, 2002 - Chapter 14.3.5 - "Fuel System Venting"

Fuel venting is through a common vent system in the Velocity. The two main tanks and sump all come to a common point, run to the top of the firewall to avoid any fuel spillage, and then exit through the bottom of the plane. I've installed an option check valve to allow cabin air to enter the tanks and avoid tank collapse or fuel starvation in the event the external vent gets plugged by ice or wasp's nest or something.

Fuel Venting

Section 14.4 Upper Strake Half

October 26, 2002 - Chapter 14.4.1 - "Fuel Cap Installation"

This section was actually fairly fun, with the exception of the static ground line. The dimensions on our plane are a little different than in the plans as we purchased a different fuel cap. We go these nice brushed aluminum locking caps -

Filling Around Fuel Cap

Newton Fuel Cap

Basically you first drill a hole through the inner strake skin and down to the outer skin slightly larger then the cap. Ours was about 4", and is placed outside the prop arc (just in the case, of course) which puts it about 18" from rear of the center section spar, and about 16" from the fuselage side. Then you come back and using the pilot hole from the first operation, drill hole through the outer skin large enough for the raised center section of the cap to protrude through.

Drilling Inner Hole and Removing Foam

Test-Fitting Fuel Cap

However, before installing the cap there are a couple of optional pieces of protective equipment to hook up. Enter the $2 length of brass bathroom chain, an #10 countersunk head screw, and a length wire. A through hole was drilled in the fuel cap and counter sunk, and the bath chain and wire are connected to it prior to bedding the cap in microglass. The other end of the bath chain is safety wired to the cap so it doesn't go missing during a fuel stop. The screwhead will serve as a ground plate for refueling operations, simply touch the fuel nozzle to it prior to opening the cap to ground it and prevent sparks. The wire will be routed out the rear strake bulkhead and attached to the engine. Once all of the attachments are in order, you simply fill the opening with flox and cover it with 2 BID.

November 29, 2002 - Chapter 14.4.2 - "Fitting Upper Strake Half"

This section just has you confirm everything you did earlier still looks good prior to closing the tank up.

December 2, 2002 - Chapter 14.4.2 - "Installing Upper Strake Half"

Before installing the upper strake half, all of the interior surfaces are covered with Jeffco Fuel sealant.

Upper Fuel Pilot Strake Jeffco

And the fuel intake screen is installed.

Pilot Fuel Intake Screen

Next the bulkheads and baffles have a significant (about 1/4") mound of Jeffco and flox spread on them top stake skin is carefully set in place, with the ground wire exiting out of the back. Then the leading edge is clecoed and taped tightly, and the top was weighted with buckets of water (or and whatever was handy).

Pilot Strake Top Installation

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Lather, rinse, repeat as they say. Here is a series of photos showing the same operations in super-fast-forward on the Co-Pilot side.

Fitting Co-Pilot Strake Bottom

Copilot Strake Baffles

Jeffco on the Copilot Strake

Copilot Top Strake Fitting

Closing the Copilot Strake

Copilot Strake Layups

Finishing the Copilot Strake Tip

After the strake tops are on, and the wings are removed, there is a fair amount of finishing work required inside the rear of the strake. The first step of this work is flipping the plane over so the you can layup the strake to spar and the strake to top skin on the rear and outboard fuel bulkheads. Many builders have apparently had success doing this with the plane upright, but this certainly seems chancy, and we were able to get several neighbors and EAA hands to help flip the bird. ;-) While it's upside down, we'll probably do some finishing work on the bottom and speed brake also.

Bird with Rollover Jigs

And Over the Top... the only loop this bird's going to do

Getting the jigs off so we go back into the garage

And back to the Bat Cave (or the dead roach look...)

The top strake to spar join is made by filling the recess between with micro and covering with two BID.

Top Strake to Spar Layup

Then the Outboard and rear bulkheads can have their top to strake skin bonds laid up.

Outboard Strake Bulkhead to Strake Skin Layup

Rear Strake Bulkhead to Top Skin Layup

Also, while the plane was upside down we made a repair to the pilot side strake. We realized once we closed it that we had neglected to apply Jeffco to the top skin in the compartment nearest the fuselage (This is easily seen in the first picture of section 14.4.2). To add this, we drilled a 5" hole through the inner skin of the fuselage and pulled the skin off. Then we drilled a 4 1/2" hole all of the way through, and bonded the skin back onto this 'plug'. The top skin in this repair compartment was then cleaned up, and Jeffcoed. When it all looked good, the foam was sealed up with micro and the plug replaced, and 4 BID into the opening. Sadly, we didn't take many pictures of this, but here is the finished repair.

Pilot Strake Top Repair

Once this is complete, the rear strake-to-spar bulkheads can be fitted and installed.

Strake to Spar Bulkhead Fitting

While the plane is upside down we take care of the strake to fuselage radius, to get a nice smooth arc. Next we pressure tested the fuel tanks, and found that the copilot side had a leak down the leading edge. This was sanded back to the outboard bulkhead, and light vacuum (from the Shopvac onto the fuel cap) pulled a batch of Jeffco and Cabosil into the leak until it was sealed. Then the leading edge was recovered in BID.

Strake Pressure Test Altimeter

Co-Pilot Strake Repair

Strake to Fuselage Smoothing

Finally the rear fuel bulkhead-to-spar bulkheads were glassed in.

Inboard Tank to Spar Bulkhead

Outboard Tank to Spar Bulkhead

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Also, we decided to do a couple of optional operations to our stakes at this point. The first was install an extra set of bulkheads inside of the door to give us a pocket for fuel testing, etc. This pocket was also completed with a drain in case rain or dew were to condense in there, an option we saw on someone's Velocity and really liked. The second was to install acrylic windows in the strake bottoms for the passengers, mainly for landing operations.

Strake End Closure

Strake End Finishing

Strake Pocket Drain

Strake Bottom Window

November, 2003 - Chapter 14.4.3 - "Outboard End Strake Reinforcement"

The strake outboard of the fuel tank is reinforced on both sides with 8 strips of Triaxial cloth 4" wide by 29" long. The surface is roughed up first, and any unevenness is leveled with micro, and then two strips are laid up on the leading edge all the way up onto the spar shear-web, then two more are laid up on the upper skin to overlap the lower by a couple of inches.

Section 14.5 Sump Tank and Fuel Lines

July 10, 2002 - Chapter 14.5.1 - "Fuel Lines"

We did most of the sump tank work while at the factory during our week of "Head Start" training, and even verified that it didn't leak before we left (so if it leaks later I'll be highly miffed. We also tapped the hardpoints at the factory. There are 2 connections in the pre-installed hard point for the wing tank connections, which are 1/4" NPT. We installed two curved 1-1/4"x 1-1/4" hardpoints at the very top of the sump tank, one for the vent line, and the other for a fuel return in the event we decide later to use the continental engine. On the front bottom we installed 1 hardpoint for the engine supply, and one on the underside for the drain. Finally we installed on hardpoint 1-1/2" down the front face for the low fuel warning sensor. Each hardpoint is tapped with the appropriate sized NPT, radiused with Microglass, and covered with 2 ply of BID.

July 10, 2002 - Chapter 14.5.2 - "Install the Sump Tank Cover"

This work was also completed during Head Start.

Closing the Sump Tank

November 29, 2002 - Chapter 14.5.3 - "Install Mounting Tabs"

The sump tank gets mounting tabs on the rounded side, to allow it to be connected to the gear bulkhead with AN3 bolts later. These tabs are made out of 2 ply of BID laying flat (3"x4") and 2 ply of TRIAX (2"x4") laid on the sump in and 'L' shape to overlap the BID.

Laying Up the Sump Mounting Tabs

Here's a shot of the tank with the low fuel sensor installed.

Low Fuel Sensor in Sump Tank

October 19, 2002 - Chapter 14.5.4 - "Sump Tank Installation"

The sump tank is installed with four bolts through the ears into the front of the gear bulkhead. The strake has a drain valve that pokes through the bottom of the aircraft. We've hollowed out the foam from the bottom of the fuselage. The factory recommends that this not protrude for the retracts, but I'd like mine to be easily accessible, and if I grind enough of my fixed gear off to scrape this thing, I've got real problems.

Section 14.6 Wing Strake Cutout

December 1, 2002 - Chapter 14.6.1 - "Wing Strake Cutout"

Well, this is where things went terribly wrong. First off, the instructions refer to a "strake cut template" that you don't get in your kit. You're supposed to lay this over the strake about 30" back from the place were the fuselage halves meet on the front of the door opening. You call the factory, and you have this conversation:

FW: "yea, don't use a template, it won't come out right, just the strake even with the door opening from the inside"

BF: "how do I cut it from the inside with the door on"

FW: "the doors on the plane?"

BF: "...ah, ..yea..."

FW: {chuckling} "and you can't get it off, can you"

BF: "...ah... no..., no I can't..." {getting nervous}

FW: "Ok, here's what you do, get the door off, then square it up from the inside, but cut it as close to the fuselage door cut line as possible"

OK, so two things. First, I don't like the "cut perpendicular to the door cut line from the inside" technique at all. You'd have to have line a foot long saw to do that in one motion, and I think it'd be hard to judge "perpendicular". Second, on my fast build I have a door jamb already, for which I'm grateful, but the cut line needs to be even with the opening (a 1/2" further out), not the jamb. So, here's what I did. You go to the hardware store and get one of these trick new B&W laser level/stud finder deals, pin one side so it doesn't seek level, grab a stand, and fire the laser at the strake perpendicular to the fuselage along the door line. At least this way I can visualize the cut line, verify it's perpendicular, scribe the line, and cut it. I was very pleased briefly, as this worked very well for me. Then I realized that I still had a door clearance issue. A quick search of the available Velocity picture archives confirmed that my strake was too low on the door line. Many angst filled hours and a couple of phone calls to the factory, the Strake Repair began.

Laser Alignment of Door/Strake Cut Line

Section 14.7 Fuel System Plumbing

October 19, 2002 - Chapter 14.7.1 - "Fuel Line Installation"

The Fuel tubing in the Velocity is 3/8" 3003 Aluminum tubing. The line from each tank's fuel outlet drain directly to the sump tank so there is no need for a fuel selector valve. The sump exits to a shut-off valve (with a T-handle control on the pilot's side of the keel) and exits to the firewall. All three tanks vent to a common header that drains out the bottom of the aircraft. To avoid draining the tanks inadvertently during upset flight, and to allow vent air to enter the tanks should the vent drain become blocked (with ice or insect debris), a vacuum breaker is installed to allow cabin air to enter the tanks.

Fuel Tubing

Shut-off Valve

Fuel Shut-off Handle

Late in the build, I wasn't entirely happy with the fuel plumbing (the bends, etc. didn't come out quite as nicely as I would have liked), and I wanted to remove the sump anyway, to do the condition inspection and verify that everything on the whale tail was properly tightened. So, I decided that I would go ahead and install shut-off valves from each strake tank to facilitate maintenance. Here you can see that they were installed with a pair of 90 degree elbows, and were safetied into the open position with wire ties.

Fuel Shut-off valves in Stake-to-Sump Line

~ End of Chapter ~ End of Section ~