Standard Pilot Blog

Monday, November 28, 2011

Assembling a Belite Flaperon

Last Revised November 28, 2011

Figure 1 Completed Flaperon, on a plane.

SPECIFICATIONS:

· CERTIFICATION STATUS: NONE. THESE FLAPERONS ARE UNCERTIFIED. Use only on experimental or ultralight aircraft, at your own risk.

· CHORD: 12” (0.305 meter)

· LENGTH: 105 ¼” ( 2.673 meter) (span of single flaperon, excluding mounting horn extension)

· AREA (per flaperon): 8.77 square feet (0.815 square meters)

· WEIGHT: dependent on amount of paint and glue. About 4 pounds.

· RED LINE Vne: 80mph. Do not use these flaperons on aircraft exceeding 80mph.

· CAUTION: 62mph is top of green arc. Keep flaperons centered (0 degrees relative to chord of main wing) and make only slight movements at 62mph and higher.

MATERIALS:

· MAIN SPAR: 0.875” x 0.035” 6061-T6 round aluminum, one piece for each flaperon.

· LEADING EDGE: 0.500” x 0.035” 6061-T6 round aluminum, one piece for each flaperon.

· TRAILING EDGE: 1.125” preformed 3003 aluminum (Aircraft Spruce PN: 03-48900), one piece for each flaperon.

· MAIN RIBS: Precut 1/8” Birch Plywood, qty 28 (14 per flaperon)

· FALSE RIBS: Precut 1/8” Birch Plywood, qty 56 (28 per flaperon)

· NYLON BUSHINGS: fits over main spar and in flaperon droppers. Qty 6.

· MACHINED ALUMINUM DROPPERS: fits to nylon bushings, allows attachment to your wings. Qty 6. Machined from aluminum. Parts are “heavy duty”, having replaced an earlier design which wasn’t as beefy.

· CONTROL HORNS: One for the left and one for the right dropper. Made from welded steel.

· RIVETS: Qty 8, use four to connect each control horn.

· ALUMINUM SHEET: 0.016” thickness, Qty 16, use to create ‘boxes’ at each end of flaperon, also around flaperon machined droppers.

· BALSA WOOD: used to create rounded end on far end of each flaperon. You should have 24” of 1x1” balsa. Makes two end caps.

· NUTS, BOLTS, and WASHERS (used to attach flaperon to wing). Qty 12 of each.

· BLUEPRINTS in electronic form – you print. We can email these to you.

· MANUAL (this document) in electronic form – you print. We can email this to you.

NOT INCLUDED:

· GORILLA GLUE

· WOOD SEALANT such as exterior polyurethane

· FABRIC COVERING and associated materials (fabric glue, primer, paint…)

· CLEANING SUPPLIES (sandpaper, scotchbrite, acetone…)

· TOOLS (normal stuff like clamps, pliers, aviation metal snips, riveters…)

WORK AREA:

· You will need a work area, completely flat, allowing you to build a flaperon. A minimum size of 18” by 10 feet is recommended.

CHECK YOUR MATERIALS:

· In the event that you have any shortages, you MUST notify us within 14 days of receipt of this kit.

1. Preparation.

a) Ensure that your work area is absolutely flat and big enough (10’ x 18”).

b) Read these instructions through at least three times before doing anything. Ensure you understand everything before doing anything!

c) Remember, you are building a LEFT and a RIGHT flaperon. Please don’t build two left flaperons (or two right flaperons).

d) Remove plastic film from trailing edge material.

e) Clean up all aluminum using scotchbrite and acetone, as required.

f) Trim and sand all plywood parts to finished shape. (Remove the excess tabs). Check that they fit over the spar tube, and that the leading edge tube also fits in the front notch of the rib. Sand as necessary. We like using a round drum sander, such as are commonly used with a Dremel or electric drill.

g) Ensure that nylon bushings fit over spar. Ensure that they also fit inside machined droppers. Sand inside and outside of nylon bushing as necessary. Final fit should be ‘butter smooth’. Absolutely no friction allowed. Flaperon dropper should flop and swing under its own weight. IF YOUR NYLON BUSHINGS ARE “OVERSIZE”, YOU MAY NEED TO MOUNT THE NYLON BUSHINGS IN A DRILL CHUCK AND TURN THEM DOWN TO THE CORRECT DIAMETER USING A MILD RASP OR SANDPAPER.

h) BEFORE YOU GLUE ANYTHING, make sure the surface is roughed up with sandpaper and absolutely, completely clean with acetone. This is absolutely necessary to get a good glue bond to aluminum.

i) A note on Gorilla glue: Our design has all of our ribs ‘locked’ in place by design, and the glue further immobilizes them. This is true in our flaperons, and also in our wing design. We use Gorilla glue in some locations because it adheres to materials extremely well, and because it is not used as a structurally critical bonding material. Also, Gorilla glue expands enormously, so use sparingly. Read the instructions on the glue container. We like to have water available in a misting bottle, so that it can be sprayed lightly on components which are to be glued.

2. Test Fit Ribs and Bushing/Droppers

a) DON’T GLUE ANYTHING until specifically instructed.

b) Slide all of the ribs, false ribs, bushings (with droppers) onto the spar. Sand out the holes as required. Remember, each rib has a top and a bottom, because the airfoil is not symmetrical.

c) Using the blueprints as a dimensional placement guide, determine where to place all parts. You may wish to place tape on your bench to mark locations, as shown in our photos.

d) ******* NOTE *******, although not shown in our photos, place an extra false rib on each side of the flaperon droppers, at approximate locations of 46”, 47 ¼”, 93”, and 94 ¼”. These will help you when it comes time to glue aluminum sheets on the top and bottom of these box locations. If you forget to put them in now, they are tough to get in later.

Figure 2 Sliding the Ribs over the spar

Figure 3 Another view of sliding the ribs over the spar

3. Glue the Main Ribs

a) MAKE SURE you have all parts slid over the spar and properly oriented. If you forget them now (or have them upside down) it is very hard to fix later.

b) GLUE: the main spar to the main ribs. Clamp the main ribs to the work bench, as shown in the photo. We use a glue syringe and minimal amounts of Gorilla brand glue. MAKE SURE that everything is absolutely square. Allow glue to set.

Figure 4 Clamping the main ribs to the workbench

4. Glue the Leading Edge, False Ribs

a) Clamp the leading edge (0.500” round tube) to the flaperon assembly, as shown in the photos. This locks all of the main ribs and false ribs in position. Make sure everything is absolutely square. You can hang the assembly off the end of your bench, as we show in the photos.

b) GLUE: the leading edge into position with Gorilla glue to all ribs. Also glue the false ribs to the main spar.

Figure 5 Gluing the leading edge, false ribs, and main ribs

Figure 6 Letting the flaperon hang from supports while gluing leading edge

5. Trailing Edge

a) Using a flat pliers, smash the trailing edge material so that it matches with the locations of the main ribs. See the photos. Don’t use a pliers with serrations, as it will scratch your aluminum.

b) ENSURE that the insides of the trailing edge are substantially roughened, wherever it mates with a rib. You’ve got to do a good job of roughening, so that the trailing edge will remain glued in place.

c) GLUE the trailing edge into position with Gorilla glue.

Figure 7 Trailing edge showing 'smash' detail

Figure 8 Trailing edge being fitted

Figure 9 Trailing edge being glued

6. ‘Box’ Fabrication.

a) Each flaperon is boxed at four locations, using aluminum sheeting: at each end of the flaperon, and at the two locations where the flaperon droppers are attached. The boxes are composed of a top sheet and a bottom sheet.

b) Make sure the aluminum sheets are of the right size. Make sure the slots (for the droppers) are cut to fit. Trim as necessary.

c) ROUGHEN and CLEAN the aluminum sheets, so that the glue will adhere.

d) Glue into position.

e) ABSOLUTELY, POSITIVELY DO NOT allow glue to get close to the nylon bushings and droppers.

f) We built our units without rivets on these box structures. You may choose to use rivets along the attachment to the trailing edge, if you desire.

Figure 10 Tip box skin glued and clamped

Figure 11 Tip box after clamps removed, before clean up and trimming

Figure 12 Another view of tip box, top down (Excess spar to be cut off)

Figure 13 Root box. Don't cut off the root spar!

7. Trim ends of flaperons; trim glue.

a) If your spar, or trailing edge, or leading edge extend beyond the outside rib, trim them flush using a band saw (or hacksaw). Sand smooth. DO NOT trim off the main spar on the inside rib – you need this ‘root’ section to install the control horns.

b) Sand off all excess glue. If you were neat with your glue application, this is not a big problem.

8. Attach Balsa end blocks

a) Glue a piece of balsa to outside end of flaperon. Use gorilla or wood glue.

b) Carve and sand to produce a pleasing aerodynamic appearance.

Figure 14 Balsa end cap, carved and sanded.

9. Apply sealant to wood.

a) Spray or brush on two coats of a good weather resistant wood varnish on all wood surfaces.

Figure 15 Protect the wood by giving 2 coats of exterior varnish.

10. Covering.

a) Cover with lightweight dacron fabric, prime, and paint.

11. Check Fit to wing assembly; install control horns.

a) After you have assembled the wings, clamp the flaperon droppers to the wing assembly to check fit. Slight adjustment of wing rib placement may be done to compensate for fit.

b) BEFORE INSTALLING CONTROL HORNS, ENSURE that wings, when folded, allow control horns to overlap. This is a tricky and critical step. Slight offset of control horns allows this. This means you must build the wings, and test fit wings on the fuselage, before installing control horns!

c) After test fit is complete and perfect, install control horns using four rivets (supplied) and 3M 2216 glue (not supplied). Control horns are to be placed 90 degrees perpendicular to flaperon chord.

Figure 16 View of uncovered flaperon in test fitting to wing (NOTE: aluminum box structures not yet done)

Figure 17 Another view of uncovered flaperon (NOTE: aluminum box structures not yet completed)

Figure 20 Quartering view of full left flaperon

Figure 21 Root of right flaperon after installation.

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Thursday, October 27, 2011

Aluminum / Carbon Fiber Spar Loading to 6Gs -- Stunning Load

Please note: James' blog has moved to a Wordpress site. To access it, please visit http://jameswiebe.wordpress.com/. All posts have been transferred to the new site, and all new posts will only be accessible via Wordpress. Thank you for your interest!

I have some really stunning load test pictures of our aluminum and carbon fiber spars. But before we get going on them, here is some necessary preamble, given our recent fantastic showing on MythBusters:

If you are looking for Belite Aircraft's production photos from MythBusters, click here. We were thrilled to be part of the "Duct Tape Plane" episode!

If you would like to follow James' tweets, @jamespwiebe is the handle to find on twitter.

If you would like to go to the main Belite Aircraft website, here is the link to follow.

Now, on to the spar loading.

Extremely long time blog readers may recall my tests of carbon fiber spars a couple of years ago. I wanted to repeat that testing, but this time I wanted to test both our current aluminum spars and our carbon fiber spars. And I was pushed to increase the load test from a 4G test up to a 6G test, which I did. (Thanks, Mike!) Also, the length of our spars had increased from 11.5 to 12 feet, as we've increased wing span (and also the wing chord.) And we had switched vendors for both the aluminum spars and the carbon fiber spars. So it was time for another test, and time to push to new limits in our testing.

This is a simple spar loading test, not a wing loading test. Of course, the airplane has two wings and each wing has two spars. We make an assumption that each one of these four spars is 'carrying' one fourth of the total weight of the airplane. Since our gross weight of our Belite is 550 pounds, the 6G loading of the entire wing structure is 3,300 pounds -- more than 1.5 tons. Therefore, the per spar loading is 825 pounds. That's a lot of weight for a single spar to hold. (The aluminum spars weigh 7 pounds; while the carbon fiber spars weigh 4 pounds, so they are capable of supporting 100 to 200+ times their own weight. Wow!)

The distribution of weight on the spar loading test spread the load over the length of the spar, with weight added at each location where a rib would be attached. Also, the spar is supported at the root (where it attaches to the fuselage) and at the strut attach point (where a strut would transfer load to the fuselage).

So here's a photo of the outcome with the aluminum spar test:

6G Spar Loading Test on Ultralight Airplane (Belite Aircraft)

And here's some individual shots:

End Section of the aluminum spar -- one of these rib/weight locations is overloaded, even for 6Gs.

Mid Section of the aluminum spar


Root Section of the aluminum spar

We also did the same test with a carbon fiber spar. Here's a photo of the outcome:

6G Load Test on Carbon Fiber Spar

The carbon fiber spar is covered in a protective plastic film.

I accidently overloaded the aluminum spar on the second to last outboard rib position, so I labeled the aluminum spar photos 6G+ :-)

The aluminum spar showed absolutely no bend after the weights were removed -- it returned to a perfectly straight attitude. In other words, this wasn't close to being an ultimate load test. There's lots more strength hiding in Belite's spars. Likewise with the carbon fiber spars -- the bend is very mild in the above photo.

Who knows how much more it could hold before it would snap? (This test does not cover other elements of the wing design, such as the lift struts, ribs, etc --- that work is saved for another day.)

IF I WAS CHOOSING, I would prefer the carbon fiber spars in my own airplane, (they are a $2200 option) but the aluminum spars prove to be an economical and beefy answer as well, albeit at a weight penalty of about 11 pounds per airplane.