skyjet

Skyjet's 

SIG Rascal 110

Electric Conversion 

 

Preparing the firewall for the battery tray.

The batteries will load through the firewall. 

 

 The hole I have in my firewall is 2 5/8" high by 3 1/4' wide. The extra width is to allow for a lot of cooling for the batteries and speed controller. You may not need to go as high with a 10 cell set up (mine is a 12 cell set up). I have an extra cell to get through the hole. The narrow part at the bottom is 2 1/4 wide. The part of the firewall each side of the narrow part is where I put the 2 4-40 blind nuts to hole the tray in. The piece of ply that holds the batteries is Midwest birch plywood 3/32" thick. It is 1 15/16 wide by 15" long. The pieces at the firewall end will have a slight angle do to the firewall offset. I put the tray where I want it and then just trace a line on the wood along the firewall. I use industrial strength Velcro to hold the batteries down. The two screws hold the battery ply down onto the 1/4" piece of ply that the 4-40 screws are in (epoxied also). You will want to put a piece of 1/2" X 1/2" X ? plywood across the inside of the firewall above the opening to reinforce it. It will have 45 degree cuts on each end. The part that the battery tray slides onto that is glued inside the plane. I made it real light because its only purpose is to guide the batteries into position. It is made with Midwest 1/32" plywood and is 2 3/4" wide and approx. 15" long. The side rail pieces are 1/2' X 1/4" balsa glued on vertically.

 

 

 

 The piece in the picture below is glued to the floor of the Rascal. You can put some pieces of balsa underneath it to support it. This is the floor of the battery tray that guides the batteries into position.

 The picture below shows an arming switch installed The purpose of the arming switch is to open the circuit to the batteries so the batteries can be installed through the fire wall without worrying about powering the motor while your hands are near the prop. 

The picture below shows the floor of the battery tray glued into place.

 If you look at the first picture below carefully, you will notice that there is and angle at the firewall end of part of the tray that holds the batteries. It is do to the offset of the firewall.

Picture two shows the completed piece that the batteries mount to.
 
Picture 3 show the batteries mounted.
 
 
 
The first picture below shows the drilling for 4-40 blind nuts. I completely install one blind-nut and screw before I drill the second. The blind nuts are easier to put in before you glue the battery floor in. When I drill the holes for the 4-40 screws that hold down the front of the battery tray I drill them a little smaller diameter than the 4-40 screw. I then make threads in the ply by screwing the 4-40 screws into the wood. After I have threaded the wood, I remove the screws and put thin CA in the holes to harden the treads. The purpose of this is so the screws won't fall out of the tray when I'm changing the batteries. It works great! 
 
Picture 2: Battery tray installed

Picture 3:  3/32" ply, 1/2' X width of fuselage to hold down the rear of the tray. 
 
 
Picture 1 below: Rear of tray with batteries.

Picture 2: 1/2" X 1/2" balsa stick above each battery. I use industrial Velcro on the tray. With the industrial Velcro and balsa sticks, I don't use a strap around the batteries.

Picture 3: Shows the two balsa sticks above where each battery will be.

Picture 4: Firewall reinforcement piece. 1/2" X 1/2" X width of the inside of the firewall (plywood).

Picture 5: You can see the reinforcement piece in the hole where the wires come out.

Picture 6:  
 
 
 
 
 
 
You need to have a exit hole for proper cooling. I put mine on the bottom rear part of the fuselage. 
 
 Cowl after being mounted.
 
 Picture 1 below: I opened the hole in the cowl for the motor shaft the same diameter as the motor for cooling.

Picture 2: Cowl mounted showing the cut out for the battery tray. Because the cut out is on the bottom of the cowl, the opening is hard to see.
 
 
 
 
The finished product!
 
 
If you have any questions or think of something else I can do to improve this information contact me at RC Groups user name skyjet.
 
You can also find a lot of other great info from several different pilots at RC Groups