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:
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!).
ADOBE ACROBAT FORMAT TEMPLATES (.PDF)
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://ourworld.compuserve.com/homepages/compufoil/).
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: 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!)
Click here to 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!
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:
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.
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").