Chapter 12 Strakes and Fuel System
The following is a little walk through building the ERacer fuel tanks/strakes.
First the landing gear leg and wheel is raised to the retract position for proper gear well construction in the strake.
Urethane foam is cut and placed between the gear leg and the main spar. The original spar mounting hole is plugged and glassed over. the 970 washers are placed to form a gap between the leg and the next layer of foam.
High density 1/4" foam is used over the leg and made even with the previous placed foam.
A support marker board is placed to mark the bottom of the strake per the plans and the upper curve of the forward strake is created with a ridge of foam per the plans.
Leading edge foam is bonded in and a lower surface of foam is attached and curved up at the leading edge.
Gaps are filled and a wall around the wheel is built before making the interior surface of the fuel tank.
The interior of the strake/fuel tank consists of multiple layers of different kinds of glass and epoxy rich lay-ups to ensure that no leaks will occur.
In my ERacer, I chose to build a forward wall in the tank to create an area in the cockpit for a lower window as well as a small storage area on each side of the cockpit. Building this addition cost me at least 2 gallons of lost fuel capacity. This option is not in the ERacer plans.
I created a small sump in each tank and bonded in a threaded flange into the bottom as well as the one called for in the plans that goes through the fuselage. The entire area is covered in stainless steel screen that is floxed into position.
On the inside wall of the fuselage adjacent to the lower floor of the tank I installed a capacitance fuel probe in each strake.
Here is a shot of the fuel probe and the screened sump prior to sealing the strake. The upper blue pipe is an access for an extra vent or if fuel is ever need to be flowed back into the tank.
Tank is complete with baffles installed. Now for the main wheel well area.
Foam is installed in the bottom of the wheel well based on the position of the wheel of course and then glass lay-ups are glued in.
Another shot of tank before seal process begins.
1/4" Divinicell foam is layed over the strake , curved down into the correct shape. Then a matrix of criss-crossed boards are layed over the foam and bondo'd to the foam to hold the curve of the foam in the correct shape.
The foam is then removed and the inside of the tank top foam is covered with glass and the fuel cap receiver is installed. Note a ground wire is attached to the cap receiver to assure grounding during any refuel operation.
The tank is then cleaned and vacuumed and cleaned a couple more times before the cover is re-installed and floxed into final position.
After cure, the entire top of the strake is covered with glass. I also layed-up extra glass over the front inside area of the strake where I knew people would sit during entry and exit from the cockpit.
The aircraft is at some point flipped over and the bottom of the strake is covered also. First the wheel well is completed...Left.. and then the entire lower strake surface.
Lower strake with the glass covering. Note the triangular cut out. This is where I installed plexiglass/Lexon as a lower window on each strake.
Urethane foam is then bonded to the flat leading edge surface...Left..., shaped into the leading edge and then covered in glass to form the leading edge of the strake.... Right
Left...These are my inter-connecting vent lines from each tank to the forward facing vents on the lower surface of the fuselage.
Right... I connected a push-pull control cable to the main fuel shut-off valve.
This shows the fuel line from the center sump tank toward the firewall. The fuel flex line runs from a strainer in the sump tank to an electric boost pump, through a shut-off valve, through the firewall, to a gasolator. The sump tank is fed from each main tank...is vented, and a one way check valve is installed in each main tank feed line.