## QuickTalk 23 - Q-TIPS

STRESS TESTING WINGS AND CANARD

Your editor has a considerable interest in stress testing procedures inasmuch as he has plans to build a new canard for a wrecked Q-2 this coming year. Others who may be curious about how it is done will enjoy the following article from DRAGONFILES, an independent Dragonfly newsletter. It was originally written by Chris Gentry and printed in the now defunct DRAGONFLYTE, newsletter #32. Any of you engineers out there could help us with your critical review and/or additional comments.

The following examples and calculations are given for the Dragonfly airframe NOT the Q-2.

"We would like to pass on some of this information that relates to stress-testing wings and canards. Since we hear about so many canards breaking all over the country, it may be a good idea to stress-test your own canard and wing.

...we will only calculate the stress on the canard. The wing is basically the same except for a few parameter changes.

First, we have to get the initial base parameters which are stated in all the brochures from Viking Aircraft:

Gross wt. + 1075 lbs.

Airfoil area = 97 sq. ft.

Approx. load on the canard = 60%

Now that we have the basic data with which to work, we need to understand logically how to simulate true flying stresses on the canard. Where the fuselage covers the canard there will be no lift, so sandbags should not be loaded in that area to simulate flight loads. Since we have a canard that is tapered and not a constant chord, there should be more lift inboard where the chord area is greatest, hence more weight should be applied inboard than at the outboard portion of the canard.

The second step is to build a jig to support your INVERTED canard. This jig should attach ONLY to the normal 4 attachment points [the Dragonfly canard is removable and secured to the fuselage by 4 bolts - ED.], and can be built using 3/4" plywood. Be sure to brace it well because it will have to support at least 3000 lbs. Make sure you have about 2 ft. clearance from the floor to each tip before loading.

We now have to do our calculations for each of the 1 ft. stations that you marked off. Number the panels 1 through 8 on both sides, starting at the inboard. The area for each panel must include the elevators even though they may not be attached when loaded with sandbags. To calculate the area of each panel use this formula: Area of a trapezoid = A x 1/2 the sum of the 2 parallel sides (where A - the distance from one parallel side to the other, which in our case is 1 ft.).

Example:

Make a matrix to record the weights for each panel area:

Example: Load/panel = panel area x load (11 lbs.) x G's (4.4)

 Panel # Area Sq. Ft. Load in LBS. 1 3.0 145.2 2

MEASURING DEFLECTION AND POSSIBLE FAILURE:

Sandbags can sometimes be borrowed from various fire stations, if you sign for them and make sure they are returned in good condition.

Before you start loading the canard you should establish where the starting points are along the leading edge. Tape 3 welding rods on the flat side of the bottom surface of each side of the canard. Let the rods protrude approximately 1 inch beyond the leading edge. Placement of rods should be at the canard tips, at panels #7 and #4. These rods should be pointed for accuracy. Now, make three stands that can be placed in front of each of the pointed rods. Mark each of the stands where the pointer is (before loading - ED.). This is the zero load point.

Place a jack under each canard end. Be sure to distribute weight to the jack so as not to damage the canard. The jack should be extended just enough to barely touch the canard. Load each panel one at a time. When all panels are loaded, slowly let the jacks down until there is no weight on the jacks. Next, mark all stands where the rods are pointing. This will be your deflection at 4.4 G's. Do not disturb the position of the stands because the test is not over yet. Unload all sandbags from both sides and now check and make sure that all pointers return to the zero load point. If they do not return to zero, that is evidence of some failure."

***

Anyone anxious to try the above on the Quickie/Q-2/200 would be well advised to call QAC first to talk things over with Sheehan. I understand he can send you a loading diagram and you can get your initial base parameters for the calculations.

From Norm Howell #486

If you are putting in NASA vents for interior ventilation, you cannot just cut out an hourglass shape and expect high volume, quiet airflow. The enclosed layout guide for NASA vents is from SPORTPLANE BUILDER by Tony Bingelis. Note the 7-degree ramp angle and the co-ordinates for laying out the duct. Lazy builders will just find an enlarging copier to obtain the proper sized vent rather than plotting points. (I had ENOUGH of that in my engineering courses.)

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