This page will be dedicated to the construction of a REMOVABLE bomb drop system for any of the Parkzone and many other FOAM airplanes.
10mm or 3/8 X 3/8 motor stick or equivalent approximately 5" long
5/8 or 3/4 wide base plates (I used wide tongue depressor type sticks from Wal-Mart) approximately
Wire - As thin as you have - a straightened paper clip CAN be used but music wire is preferable
Several straight pins.
Roll of packing tape. I used the clear type as it will need to be painted later.
3/4" thin wall sprinkler pipe
CA glue - thick and thin
Gorilla glue - big bottle brown color
Water - spray or mist bottle preferred but not really necessary
Drill and/or dremel tool Needle nose pliers. Cutters. X-Acto knife.
2 sets of control horns - small and as inconspicuous as possible! LOL!!
8 rare earth magnets (you could probably get away with using 4 if you have to.)
First cut two 2.5" lengths of the 10mm or 3/8 X 3/8 motor stick.
Then drill several holes near one end and route them out to create a slot which runs through the stick.
The slot need only be big enough for the wire to pass through easily without resistance.
Next make a groove from the end of the stick NEAREST the slot to the slot in the bottom of the stick.
The groove need only be deep enough that the wire can move along it freely after the stick is glued to it's base plate.
The 10mm or 3/8 X 3/8 stick then can be "shaped" using a sanding drum and dremel tool or
regular sandpaper if you want so that the side opposite the "grooved" side has a slant. This will give it the appearance desired
when mounted of a hard point on a regular plane.
Once the shaping is done the wire needs to be bent to shape. I used a "z" bend at the control horn end to make it easily removable
but I suppose you could use any connector type you want. There needs to be about 1" of wire from the end of the base plate to the
"z" bend. This gives plenty of room for movement as only about 1/8" of movement is needed for actuation anyway.
STOP!! - DO NOT GLUE ANYTHING YET!!
Now place a magnet on the end of a base plate and draw a circle (or rectangle as may be) around it.
This material will need to be removed so that the magnet will be flush with the bottom of your base plate.
This can be done at both ends of your base plates as this is the mounting method. I also used the sanding
drum to "rough up" the ends of the magnets where they will be glued as this helps keep the glue in place.
Now tear off a piece of packing tape and place it STICKY SIDE UP on your bench. Place one of the base plates
that you have prepped onto the center of the tape strip. Place the magnets into their place (the tape will "hold" them there.
Now us a liberal amount of CA glue to secure the magnets in place with the base plate. Don't worry about getting CA glue
on the magnets as the tape is covering the essential mounting surface!! LOL!! Repeat for both base plates.
When the glue has set and the magnets are in place on both base plates cut the tape around the base plates as closely as you can and
use your sanding drum to remove any excess. You can now set the wire in place and glue on the 10mm or 3/8 X 3/8 stick to the base plates.
If your magnets stick up slightly then making a indent into the stick so that it covers the magnet is preferred. Make sure the wire moves freely
after the glue sets!! LOL!!
Also do not worry about the wire sticking to the magnet as it really will not be a problem.
Your top mount is done. You can check it against a piece of the thin wall sprinkler pipe to make sure it works as designed.
This is also the time to add the straight pin to the front of the mount. The straight pin is used as the front tensioner for holding the "bomb" in place.
It will need a drop or two of CA after it is in place. The length between the front pin and rear wire is totally up to you and the size you want
your bombs to be.For trial cut a piece of the pipe and use the pin placement for reference to drill two small mounting hole into the pipe.
Keep in mind that the REAR hole on your actual bomb will need to be as far rearward as possible.
The reason for thins is that after you add the fins to the rear of the bomb it must still "clear" the flap!
The bomb is "trapped" by the pulling of the wire rearward by the flap and thereby "trapping" the bomb
between the wire hook and the front pin. When the flap is actuated and pressure is relaxed the bomb
simply falls away.
Now that you see HOW it works we can start the wing mounting process.
Allow two other magnets to snap themselves to one of your base plates. These
can now be used to mark their mounting place in the wing. Make sure the wire is completely
to the rear of the slot - as it will be when the flap is up in its normal position (as it should
be for this installation!). This will give you the mounting place not only for the wing magnets
but also for the control horn on the flap. Remember you will only need about 1/8" of
travel in the wire to capture or to drop your bomb but the control horn must be mounted
so as to allow travel of the wire WITHIN THE SLOT and not bottom out at one end or
Not like this!! It won't work like this!
Once you have the position set press EVERYTHING down pretty hard into the foam.
This will indent the foam with the magnet position as well as leaving an impression. Now
cut out the impressions to allow mounting the magnets. While the magnets are STILL STUCK
to their counterparts you need to MAKE them - the marked side will be GLUED into the wing!
If you need to test fit a magnet remove one - but put it back after the test fit!
This is WHY the magnetic poles of the magnets being matched is so very important because
if you glue a magnet into your wing incorrectly it will NOT ATTRACT but will repulse!
Leave the magnets attached to the base plates until you are ready to glue them in place!!
When you are ready test fit the mount WITH the magnets still attached. If it fits tightly
and is aligned then you are ready for glue. Remove the base and keeping it aligned with
the wing - i,e, front to front and rear to rear - remove ONE magnet. It will very hard to do!
And now you will see why marking the side that will be glued was important!! LOL!!
Put some thick CA into the hole for the magnet - place the magnet into the hole with the
MARKED SIDE IN the hole - now repeat for the other end. Cover the magnets with
Let the glue set and while it is setting use a Sharpie (Silver in this case as these are on a
Parkzone P-47) to color the tape. The tape will also help in keeping the magnets aligned.
Now attach the control horn into the place marked earlier and you should be ready to snap on your
system and go drop bombs. Making bombs will be covered in a later build thread but they are
made from the 3/4" thin wall pipe. Thin wall pipe is the lightest so that is why I chose it.
Here is a little video demo of the system finished and working.
Hope this helps. I have fully tested this and it works flawlessly.
The following is a "HOW TO"for installing your bomb release mechanisms onto your airplanes wings.
After the control horn is set in place AND installed onto the flap you are ready to proceed with the installing of the release mechanisms you have built. Although the photo does NOT show the control horn what is NECESSARY is that the release connector rod ( "Z" bend) be connected to the control horn and the release mechanism be pulled taught so that the control rod is at it's rear most position with the flap (control horn) in it's normal position. Then the release mechanism is placed on the wing and firmly pressed into the foam of the wing. Since the two extra magnets are STILL attached they are being pressed into the foam of the wing at the mounting location. This will leave two "indentations" of the magnets in the foam of the wing after the mechanism is removed.
The indentations may be faint so that drawing around the indentations with a pencil or ink pen will make them more readily visible. Once the circles are readily identified you will need to recess the foam INSIDE the circles ONLY deeply enough for the magnets to sit LEVEL with the wings foam.
I use a dremel tool with a grinding bit for this purpose but an x-acto knife could be used for doing this step also. Just make certain the magnets WILL fit into the recesses flush with the wing foam surface. DO NOT GLUE THEM YET.
You will now need a piece of packing tape and a good clean cutting surface. The packing tape should be only slightly longer than the release mechanisms.
Place the tape on your cutting surface and using a rule or a straight edge and knife (X-Acto or utility) slice the tape horizontally into two equal lengths. Remove the extra magnets from one of your release mechanisms. Keep them separated! LOL!! Now take one of the tape halves and place it onto the release mechanism over the magnets that are embedded in it - BUT sticky side UP. Holding the tape in place over the length of the release mechanism NOW return one of the extra magnets at a time BACK to their mate magnets. When these "snap" into position they will TRAP the tape between them and the release mechanism. (SEE PHOTO ->) When both of the extra magnets are in place and the tape is between them and the release mechanism then they are ready to be glued into the circles you made earlier.
Apply CA medium thick glue to the circles you created. Do not place too much glue into the circles though as when the magnets are inserted you do NOT want a lot of glue overflow squishing out all over your wing!
Now re-connect the "Z" bend to the control horn and stretch the release mechanism taught again. The extra magnets should line up with the circles perfectly. Press the magnets into the circles with the glue. Now you will see how that packing tape is sticky side out!! Press the tape to the wing! Make certain the tape is completely adhered to the wing.
After pressing the tape to the foam you may slide the release mechanism sideways (the front of the mechanism that is NOT connected to the control horn). You will note that the packing tape in now holding the magnets in place in the wing! The release mechanisms should be removed by sliding them sideways in the direction that will allow the "Z" bend in the control wire to be removed from the control horn. You will replace/install the release mechanisms in the same manner - "Z" bend into the control horn and then move the release mechanism over to the magnets in the wing where it will "snap" into place.
Once the magnets have been installed you will have a packing tape strip with the two magnets visible under it on your wing. The tape is pretty shiney so you may choose to use a Sharpie of the appropriate color to "color" the tape to hide the magnets and the tape. Remember once the "Z" bend is installed to the control horn and pulled taught the magnets will be automatically aligned and they WILL strongly attract each other nd the release mechanism will "snap" into place!