Standard Rail Button (fits 1" Rail - 1010)

For the standard-size rail buttons, drill a small (3/16" diameter drill bit) hole for the screw and flanged weld-nut backing. Insert the flanged nut through the hole from the inside of your rocket. If your rocket is too narrow to fit your hand into, you can use a magnetic stick or similar device to insert the flanged nut.

Assemble the rail button as seen in the diagram to the right. There are two sides to the rail button, one is routed to compensate for the screwhead, allowing it to sit flush with the top edge of the button. Put a dab of epoxy or thread-lock glue in the nut to keep the screw from coming out and you losing your rail buttons. You can also put epoxy clay on the back of the flanged nut to prevent shock cords from catching.

To use the small rail button without the flanged nut, you will need to purchase a longer screw. #10 (3/16"), 1/2" minimum length.

For the large rail buttons, there is no flanged nut included. Just drill a small hole for the screw that goes through the plastic button. Put a little bit of thick CyA (super glue) on the threads and slide it into the hole. There is very little forces trying to pull the button straight out. All the forces are in a side-to-side direction, which it absorbed by the steel screw in the hole. In other words, the CyA glue will hold the button on the rocket. But try to prevent glue from getting on the plastic button. Ideally, you want the button to spin on the screw so that it has less friction as it slides along the launch rail.

On large diameter rockets (where you can get your fist inside the body tube), you can put a little dab of Fix-It Epoxy clay on threads on the inside of the rocket. This is a lot stronger and will make a nice streamlined contour over the threads so that the parachute or shock cord is less likely to snag on the threaded portion. We highly recommended this if you can do it.

For more information on installing rail buttons, see Peak-of-Flight Newsletter #489. 

When using a rail button standoff, the minimum length of the screw you'll need is found by adding up the length of the rail button (.435" for a standard button), plus the length of the standoff, plus the wall thickness of the body tube, plus about .25 inches for the part of the screw that protrudes inside of the tube where you'll attach it with a nut or with the Fix-It Epoxy clay. You can buy screws at your local hardware or building supply store.

Because of the extra length of the launch rail, there is not a bad reason to use a rail launcher for any size rocket. We always recommend a longer launcher for the extra benefits that a straighter lift-off have.

You can probably put rail buttons on small rockets. But because they are wider than a launch lug, they will produce more drag on a small rocket than a smaller lug. A good starting point for using rail buttons is a 2.0 inch diameter rocket. If you want to use the long launch rail on smaller rockets, see our alternate suggestion of the "Fly-Apart Rail Guides" in Peak-of-Flight Newsletter 247.

First of all, radially, they should be placed equal-distant between any two fins. Remember, the rail is 1-inch wide, so you can't put them too close to any single fin or the fin itself will prevent the button from engaging the rail.

Forward-and-Aft Location: You would position them just like you would two small launch lugs. Ideally, you should put one button in front of the CG point, and one button behind. Most modelers place one at the very rear of the rocket so that it is easier to see it as it is being loaded onto the launch rail. Once you have the bottom button on the launch rail, it is easier to get the top button to slide on without scraping all the paint off the side of the vehicle.

The forward button's location is not too critical. As mentioned, ideally it should be positioned ahead of the CG point on the rocket. But if you have anything inside the rocket that needs to slide forward (like a parachute ejection-piston device), you'll have to put the button behind it so that the threaded screw on the inside of the tube doesn't prevent it from operating properly.

The nice thing about rail buttons is that they are more forgiving than traditional launch lugs. They can be slightly misaligned, and they will still slip easily along the rail (because they are circular).