Wing Overview

The standard Terminator wing has a flat center section with polyhedral tips. The Terminator center section is a flat one-piece core, 21" long, with a 7" chord and a standard 8.01% thickness S4083 airfoil. The Terminator tip section is 20" long, and tapers from a 7" chord to a 5" chord. The S4083 airfoil is transitioned from 8.01% thickness to 5% thickness from the tip section joint to the wingtip, and there is 1% of washout at the tip.

The polyhedral tips are attached with 4" of dihedral under each wingtip.

For those who have not done composite wings before, the general construction sequence is:

1. Cut foam wing cores
2. Cover with balsa sheeting or fiberglass (still in separate panels)
3. Join the panels at the indicated dihedral angles
4. If balsa sheeted, finish the wing to prevent the wood from picking up moisture

Note: The trailing edge of the Terminator standard wing is straight, across both the center and tip sections - all of the chord taper is done with a leading edge sweep. Please see the pictures on the intro page for pictures of the wing layout.

What Kind of Foam Should I Use?

This is one of the most common questions we have been asked. We have had good luck with the pink foam sold in sheet form at Home Depot. It seems to be much stronger than white foam, at a very slight weight penalty. For us, the strength advantage is worth the tradeoff, since it is harder to fold the completed wing.

For a stronger wing, use pink foam for both the inner and outer panels.

For a lighter wing, but not as strong, use Home Depot pink foam for the inner panels and 1 lb virgin white foam for the outer (tip) panels.

Wing Core Templates

Below are templates in two formats for both fiberglass bagged and balsa sheeting wing designs. Templates are provided in Acrobat PDF and CompuFoil 98 LFT format (these templates use an airfoil included in the CompuFoil Airfoil Library - without the library they will not load). CompuFoil 98 will give you the most control over template creation, and allow customization easily. On the other hand, creating templates from a PDF file does not require you to purchase software (but you must check the template printouts as noted below to be sure they’re sized correctly!).

NOTE: Be sure to check the dimensions of your template printouts if you are printing them using the Adobe Acrobat PDF files! On most printers they will be full size, but on some printers the size may not be correct! The chord of termctrg.pdf and termctrb.pdf should be a full 7", while the chord of termtipg.pdf and termtipb.pdf should be a full 5".

If your printer does not render these at full size you have two options. You can either take the printouts to a copy shop and fiddle with the enlarge/reduce function of their copier until they come out the right size, or purchase a copy of CompuFoil, and use the CompuFoil LFT templates below instead. (The CompuFoil web site is at http://www.compufoil.com).

LEADING EDGE TEMPLATES

Here are leading edge templates, to help shape the leading edge correctly. Each template has two airfoil curves; the inside curve is for the foam on a sheeted wing, the outside curve is for the foam on a bagged wing (or either completed wing).

COMPUFOIL 98 LOFT FORMAT TEMPLATES (.LFT)

NOTE: These templates use an airfoil that is included with the CompuFoil Airfoil Template library option, but is not included in the “base” CompuFoil 98 product. Without the Airfoil Library option, CompuFoil will likely not be able to load these templates.

NOTE: Be sure to check your CompuFoil printouts for accuracy. Not all printers are accurate at the level needed to create clean airfoils - don’t assume that yours is without checking it. To check your printer calibration with CompuFoil 98, use the Adjust Printer Aspect Ratio item on the Defaults menu. (Make sure to write down the original settings before tinkering, just in case!)

files/terminatorlft.zip - 6 KB - Download a PKZip archive containing all four CompuFoil LFT files (this is helpful if for some reason CompuFoil will not open the airfoils correctly when you click the links above.

Finishing the Wing

The Terminator wing can be finished either with balsa sheeting or glass bagging techniques.

BALSA SHEETED OPTION (balsa sheeting step-by-step created by Dan Griscom - thanks!)

If you are going to balsa sheet the wing, find enough sheets of 30" x 4" x 1/32" balsa to cover the surface. (If you will be building a bunch of Terminators in a club-style project, you should consider buying a 100 sheet lot of balsa so that you can pick the weights that you want and end up with matched panels.)

The balsa sheeting can either be attached with 3M77 spray adhesive, or if you (or a club buddy) has vacuum bagging facilities you could bag the balsa on with epoxy. NOTE: 3M77 is a contact cement - you get one try to get the sheeting aligned - be careful to get things lined up before you let the sheeting touch the core!

1. Tape a pair of 1/32" x 4" sheets together with Scotch tape. Bend the joint open, apply some Elmer’s or carpenter’s glue to the edge joint, open the sheets up flat, and wipe excess glue off of joint with a damp paper towel. Glue six pairs of sheets this way and let them dry overnight.
2. Put the bottom core blank on a flat surface, cover with wax paper, and place a wing core on top.
3. Cut the 8" balsa sheet to fit the core, leaving extra on all edges.
4. Spray the balsa sheet and the core with 3M77, and let dry until tacky.
5. Starting at the trailing edge, touch the balsa to the core and smooth the balsa onto the core until you reach the leading edge.
6. Trim the balsa flush to the core, except for the trailing edge. Since the foam core doesn’t reach all the way to the trailing edge of the airfoil, the balsa should overhang 1/3" past the trailing edge on the center section and at the inner ends of the outer sections, and 3/4" past the outer ends of the outer sections.
7. Put the top core blank upside-down on the flat surface, and put the half-covered wing core upside down on top.
8. Spray balsa and core with 3M77, let dry until tacky, apply balsa, trim to core (again, except for the trailing edge).
9. Stack bottom core blank, wing, and top core blank, weight down until flat, and let dry for 24 hours.
10. Sand the leading and trailing edges to shape, and run a length of 3/4" tape along the leading edge to cover any leftover gap.

Finishing the sheeting is easy. Just sand with 320 (lightly - don’t go through it!), and then finish it with either water-based polyurethane or an alcohol-based shellac (make sure you get the kind with built-in sealer) like Bullseye. Applying either one with a 2" brush is quick and creates a nice finish. Finish sand and you’re done with the wing. Option: Tinting Polyurethane for a colored finish

VACUUM BAGGED FIBERGLASS OPTION

For general hard use, bag the center and tips with 1.5 oz cloth. The steps below should yield a 4.5 ounce wing:

• Add a top center doubler of 1.5 oz cloth (5" by full span)
• Add a bottom center doubler of 1.5 oz cloth (3" by full span)
• Add two pieces chordwise in the center (measured) of 1.5 oz cloth - one 2" wide and the other 3" wide. These reinforce the center of the wing where the wing bolts will go through.
• Add a doubler of 1.5 oz cloth to the top only of each tip panel, 3" wide by the full span including the tip.

That’s it! Try to bag with two ounces or less of resin for the whole wing. If you use a 4" roller it will help you to be light on the application. For a 4.1 ounce light wing, change the tip cloth and doublers to .75 ounce cloth and reduce the amount of resin on them. (Note that if you do “gorilla launches” this lighter wing will fold more easily…). Click here if you want to check out the “How to Bag a 4 Ounce Wing” option page.

Now this option is really not for first-time “baggers”, but for those of you who want to try something more adventurous, take a look at Bill’s Terminator Bagged Tips. This page describes some special work that Bill likes to do on the tips - seems to get a bit more launch height and more tip stall resistance.

Assembling the Wing

Once you cut the cores for each wing section, they can be attached with a layer of 5 minute epoxy. The center section should be set flat on your work surface, and the tip joint carefully sanded until it is a flush fit with the underside of each tip 4" above the work surface.

Once you have sanded the correct angle into the tips, here is a quick and easy way to join them.

1. Find (or cut) something in your shop that is 4" high to use as a tip dihedral brace
2. Using a #11 blade (X-Acto type works well), tap randomly on each mating surface where the panels will be joined. This will make some tiny “woodpecker” holes in the foam surfaces that will be joined, and ensures that the epoxy can flow into the foam and not just form a surface bond.
3. Take some tape (Scotch tape or packing tape works fine) and hinge the tip section onto the center section on the bottom surface, so that when you flex the tip up to the 4" set point the foam is tightly mated.
4. Unfold the tip, leaving the tape in place, mix up some 5 minute epoxy, and brush onto the foam, making sure that the epoxy flows into any foam crevices and the perforations made in step 2.
5. Gently fold up the tip and rest it on the dihedral brace.
6. Excess epoxy will flow out of the top of the dihedral joint - I use craft sticks to “scoop up” the extra epoxy right away - and if you work reasonably quickly you can then wipe off any remaining layer of epoxy with paper towels.
7. When the epoxy is cured, peel off the tape on the underside of the joint, and voila - you’re done!

If you want to cover up the joint, almost anything will do - electrical tape, covering material, trim sheets, whatever. The wing will not need any extra strength in this joint after the epoxy, so resist the urge to glass over the joint - it’s wasted weight!

Installing the Wing Hold-Downs

We use two aluminum 6x32 bolts (front and rear - about 5" apart) to hold the wing on. The exact location isn’t too critical, but on many wings we set up the front bolt 3/4" from the leading edge, and the rear bolt about 5" behind. To keep the wing from being crushed at the bolt locations, make up a couple of “washers” out of 1/16" plywood, about 1/2" in diameter, and glue them to the upper wing surface with thick CA. (These don’t need to be round - we cut them 1/2" square and just sand or cut them to be “roughly round”).