Cutting Foam Wings With a Hot-Wire
Aircraft Spruce and Plywood
(Aircraft Wingtips, Foaming and Framing)
Using Aircraft Spruce and Plywood to build bows out of wood and then did the plywood leading edges. In my experience it doesn't help you. What we determined is that if we would ever do another, it would be made of metal tube bow and foam/fiberglass. You'll get better and smoother finish with the fiberglass. Although when using plywood remember it doesn't like compound on the curves of which you will be looking at on the wing tips of your project.
If you have been making your wingtips using the foam/fiberglass method. Then the best recommendation is for the 4130 tip bows also. You can use a hot-wired framing system to shape the foam. I have the raw foam on the top of the two left side wings right now and I thought I'd cut them to shape before I go any further.
The foam used in this project comes from the Home Depot store and is a pink, Owens Corning 2' thick insulating board foam.
The reason to choose this material is that it's actually pretty light and sturdy. It also lets you make pretty decent cuts and it smooths to a nice finish. There are many choices that you can go with from the ACS to Birch to Spruce. For a sheet roughly 4x8 and about 2 inches think, you'll end up paying about $25 dollars. This will also give you plenty of room to experminent with different shaps and cuts on the board. To cut the board and foam I will use a hand saw to get the correctg shape for each bay then when I'm finished cutting, I'll sand it to the proper fit. Then to finish off, use a bit of epoxy glue aroudn the edges and fix the foam so that it's secure.
Finish Insulating with the end and with the nylon attached to the wires to each end. Then with a .025 safety wire for the cutting wire. Get a one 6 volt lantern battery, then went with two 6 volts in parallel. It would cut, but was very slow. I then remembered that I had an old low-voltage outdoor lighting transformer in the attic. I can now hook it up and have the hot-wire cutter ready to go.
It works very well but you have to be a bit carefull or you cut a wider swath than you intended. I'll cover the foam with fiberglass and epoxy resin. I'm just getting started and have made a few mistakes, but by the time I finish all four wings I'll be getting good. I have posted a few pictures showing what I have done so far. I hope my eperience and explanation helps you. As I said, this is my first time and I'm learning as I go.
So the next question is should you apply the fiberglass before or after the leading edge plywood has been fitted?
Well, the construction application the foam is used for is insulating walls. I've seen it in 1" and 2" thicknesses. They probably make it thicker. also. It's the basically the same blue foam that ACS sells. It can be safely hot-wired and sanded.
My plan is to cover the foam before I do the plywood leading edges. I'll put some type of barrier of the last rib of the open bay to keep the glass off of it. That way, I can use that rib to attach the end of the plywood. I sould be able to sand the glass at that joint to make a smooth transition from the tip to the leading edge. I'm glad I went with the foam. The results so far are very nice and I haven't even started with the fiberglass.
1. Western Aircraft Supplies
- British Columbia.
Sells aircraft grade Sitka Spruce.
Has Spruce kits for the Pietenpol as well as some others.
Marc Septav, Western Aircraft Supplies,
Slocan, British Columbia V0G 2CO, Canada.
tel (250) 355 0003
fax (250) 355 0004
e-mail - firstname.lastname@example.org
2. Aircraft Spruce and Specialty
Sells Spruce, Aircraft Plywood, glues, fabric, and just about everything else.
3. Wicks Aircraft Supply
Similar Product line to Aircraft Spruce.