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Using epoxy for glueing down wing skins

1. Mixing epoxy for wing skinsUse West systems 105 with 209 hardener (works great for Epoxy fuses). For climates that are not so hot you can use the West Systems 206 hardener and still have time to put the wings together without it going off in the pot (Exotherm).You can also use an epoxy that you get a the hardware stores for this. as long as it is a general purpose epoxy and not a laminating epoxy. Laminating epoxy has a stronger wicking action, not what we want.
2. The wood next to the wing needs to be sealed. Get a wood sealer. any sealer will work except the water base kind. Water and wood sheeting don't get along!
3. Mix the epoxy and then mix the same volume of micro balloons. Again just about any clear looking micro balloons will work. Stay away from Prather brand of Micro balloons, they use phenolic balloons and does not work correctly.
4. Put a layer of epoxy/micro balloons on the wood sheeting. Don't skimp here! Remember we mixed in micro balloons into the epoxy. It does not weigh anything! Create a thin layer that you can start to see turn a little milky is about right. I mix a little over one ounce of resin and this will do a set of PSS wings (48" span). This works out to about a 1/4 cup of mixed resin and micro balloons per wing panel.
5. Press or vacuum (5 inches only white foam) the wings in place over night. Final sand after dry.

- Robert Cavazos (CSD)

Basic Mold Making

To create your own plane / mold, you can basically do it by:

Get some 2" or thicker "Blue" foam, and glue the blocks together using some 3M 77 adhesive, or some Dave Brown's Sorgum contact cement. This will make the blue foam blocks as big as you need it to be. Lay the blocks in the horizontal plane, and stack them together. Cut the outline of the top and sides into the blue foam block. You should have the "Profile" of the plane at this point. Then, make templates of each of the major cross-sections, (You only need one half, as the other side is a mirror image). Then start sanding the blue foam at the nose, working your way back to the tail. Use the templates to check the profiles as you go. They must be even on both sides of the fuse. Once you have carved the blue foam "Plug", you then use EPOXY resin, not polyester resin to glass the outside of the plug. Once you have laid a couple layers of 6oz glass cloth over the plug, you can then do one of two things:

a) Pour acetone down into the center of the plug, and eat away all the blue foam, leaving you the outside shell of fiberglass. This process is called "Lost Foam" method. You must make sure that you have enough fiberglass on the outside though. Don't try this with a couple layers of light cloth only. You then have a fuselage ready to build a plane from. The disadvantage to this is that you only have one fuse - not a mold to make more. The advantage is that you didn't have to build an expensive mold.

b) Build a mold. Get a piece of 3/4" pressboard with the white melamine surface on it. Trace the side side profile outline of the plane onto the board, and cut carefully the inside of the profile on the pressboard "Parting plate", so that the profile (Side view) of the plane fits really tight at the centerline of the fuse. You should now have a "Parting Plate" with half of the side of the fuselage sticking out of the top of it. The fuselage plug must be primered, sanded and waxed very well at this point. Any scratches or marks will show up in the mold. Put polyester modeling clay in the gaps around the plug/parting plate, and then scrap it so that there is a perfect joint between the plug and the parting plate. Carefully wax all around the plug and parting plate, at least 6-12 coats. This helps release the mold from the plug when finished. Now spray some black gelcoat over the plug, and parting plate. This will be the surface of the mold. After the gelcoat hardens up, lay 1oz fiberglass and resin over the gelcoat, carfully making sure that there are NO air bubbles between the glass and the gelcoat. Repeat using 6oz cloth, until the mold is approximately 1/8" minimum to 1/4" thick. all around. when the glass has dried, pop the parting plate loose from the mold/fuse plug, and set it aside. Do NOT remove the plug from the first half of the mold you just laid up.Wax the remaining half, and spray black gelcoat on the remaining plug/mold surface. Apply the light 1oz cloth again, and then the 6oz glass cloth. This will build the other half of the mold. When completed, you probably want to drill some 1/4" holes so that you can bolt the two halves together.

Congratulations! you now have a mold.

Clean up the new mold, waxing it, and polishing it until the inside of the mold is smooth. Then wax again - You can use PVA release agent on the mold if you want.. You can now "layup" a fiberglass fuselage using 6oz glass cloth. 3 layers in the nose, and two layers in the tail area. Take the two halves of the fiberglass fuselage out of the mold, and Zap together. Then use 1" fiberglass seaming tape and resin to seam the two halves together. You are now ready to go!

Have fun.....

- Carl Maas (ISR)

Charging Jack / On-Off Switch

To create a combination charging jack / on-off switch from a jack / plug:

First of all here is a summary of how it works. The phone jack is installed in the plane and replaces both the normal ON/OFF switch and charging plug that comes with a typical radio system. Two plugs are required. One "dummy" plug (no wires connected to it) is inserted and remains in the jack most of the time when not flying to open the circuit between the battery and the receiver. This is the OFF state. When the "dummy" plug is removed, the circuit between the battery and the receiver is closed which turns the onboard radio ON. The second plug replaces the plug on the battery charger. When the charger plug is inserted into the jack, the circuit between the charger and the battery (plus-to-plus, minus-to-minus) is complete allowing the onboard battery to be charged.

Here's how I did the wiring. First I decided that the positive (red) lead from the charger would go to the center connector of the charging plug and the negative (black) lead would go to the outer connector. This seemed pretty conventional to me. I therefore cut off the old charger plug and soldered the red lead to the center connector and the black lead to the outer (longer) connector. (Remember to slip the plastic sleeve of the plug over the wires before soldering the leads to the plug.) You really don't have to do anything to the "dummy" plug. However, on mine I cut off the outer connector completely to make sure there was no way the two connectors could accidently touch and short out the battery. I also attached a red ribbon to the "dummy" plug as a reminder that the plug must be removed before launching the plane. The first step in wiring up the phone jack (mounted on the fuselage of the plane) is to identify the connectors. There are three connectors on the jack. Hold the jack in your hand with the bottom facing you. Rotate the jack so that there is one connector at the 9:00 position, one at the 6:00 position and one at the 3:00 position. At the 12:00 position will be the springy metal housing which makes contact with the plug when it is inserted. Solder the red (positive) lead from the battery to the 6:00 connector. (This will connect with the center connector of the plug attached to the battery charger.) Solder the red (positive) lead from the receiver to the 9:00 connector. Finally, solder the negative (black) leads from BOTH the battery and the receiver to the 3:00 connector. I would strongly recommend NOT soldering the battery leads directly to the phone jack. Instead install another connector (e.g. Deans 2-pin) between the battery and the phone jack so that the soldering can be done without the battery in the circuit.

Well, this seems to work for me and I hope it helps you. Please be aware that this technique works for the Radio Shack CAT 274-292 phone jack and CAT 274-290 plug only.

(Thanks to Bill Mullica)