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Q-Talk 168 - Doing it Right!

N480KS Quickie Q200

by Kevin Sheely

N480KS

I am a 285 TT single engine land private pilot and this is my second amateur built aircraft. My first was a single seat Pitts S1-C, which later became an S1–T model after purchasing and recovering a used set of symmetrical SparCraft wings. I bought the Pitts project (fuselage welded, some sheet metal complete and a 150 Lycoming attached to an engine mount) while purchasing my Continental O200 engine for the Q200. As I was leaving the garage, the seller asked if I knew of anyone interested in finishing the project. Two weeks later, I picked it up. I finished it quickly, and made the first flight in November 1986. It had about 135 hours on it when I sold it. I made a lot of 10-15 minute flights to fly some aerobatics and return at sunset.

After my original forty hours of private pilot training, I received some aerobatic training at the suggestion of our FAA flight examiner at Kent State University. I loved it and started flying a Decathlon and a Great Lakes, and I also got some Christen Eagle time along with some time in a J3 cub on floats and Super Cub on floats and tundra tires in Michigan.

Not flying any after moving to Florida, I had my Q200 project sent from Michigan to Florida with the hopes of completing it in 6 months. Well, it took 4 years of work in the garage and 6 more months once I got it to the airport. I incorporated all of the 6-pack of kit handling improvements. Everything had to be correct. There were a lot of calls and emails to Sam H., Jim P., Gary K., Sanjay D., Mike D., and Jerry, M and others.

N480KS

For a couple of months prior to my first flight I got transitional training in an RV6 (about 5 hours) and one flight with Mike Dwyer in his Q200. During this time I also had 17 times where I would taxi down the runway at speeds up to 55 mph. Usually I did three taxing runs per session. I was able to keep it straight except a few times where it left the centerline when removing power. I believe it had to do with P factor. I also completed the EAA Flight Advisory program. This really helped prepare me for “what if” situations of a first flight. Remember that our Quickies are truly a homebuilt aircraft and not an assembled kit. We were responsible for creating our airfoils from paper templates and minimal construction plans. We rely on each other now.

 

25Jun14 – First flight of a kit that was purchased new in April 1985

After a restless night of reviewing every bolt, nut, layup, assembly, and a second thorough preflight, I briefed my ground crew on my flight plan. All three EAA members had radios and golf carts along runway 08R at North Palm Beach County airport, Florida (F45). My wife was very calm on the outside. One of the guys was able to take her aside and talk her through everything I was doing.

My plan was to treat this like I was taking it out for another taxing test but keep the throttle in. I took off around 8:30AM on a calm morning, with the elevator trim and reflexor in the neutral positions and the C of G was neutral also. The first thing I noticed was that my elevator forces were very high with a tendency to roll to the left. The roll to the left was expected but the elevator was not. I maintained a wings level climb out to a downwind and midfield crosswind to stay over the airport at 3,000 feet. The CHT got near 400°F so I reduced the power and climb rate. Then it was suggested to climb to 5,000 feet for cooler air. My forearm was getting pretty pumped because I only used the trim wheel and not the reflexor. I did some slow flight down to 90 mph with some shallow turns. Then I returned to the airport for a beautiful 3 point landing and I let it roll out to the end of the runway. The total time in the air was 30 minutes. After a de-briefing I removed the cowling and went home. It took three days to go back out and inspect my plane and prep for another flight.

Lessons learned that day after talking with about 28 friends and my flight advisor:

  1. I was prepared both physically and mentally.
  2. I was not nervous at the end of the runway because I was prepared.
  3. I should have used the reflexor to trim the airplane.

 

11Jul14 my second flight

Another calm morning and my wife was a little less nervous. As I taxied out I could see a couple of rain showers in the distance (south Florida in the summer), so I knew this would be a short flight. I took off from 08R again, but this time I used the reflexor after takeoff to relieve the elevator forces and it was awesome. The left was still there but I managed it. The landing again was three point but maybe slightly tail first. The CHTs stayed around 400°F. Total time in the air was 15 minutes with a max speed of 151 mph.

Lessons learned:

  1. I was prepared with knowledge from the first flight and conversations with other Quickie pilots.
  2. I was not nervous at the end of the runway because I was prepared.
  3. The reflexor is an awesome tool when used properly to trim the airplane.

 

18Jul14 my third flight

Another calm morning and my wife was getting used to the experience and radio jargon. My plan was for a 30 minute flight, staying within a 5 mile radius. The takeoff on 28L went well, again keeping on the centerline which I can prove because of my MGL EFIS flight data recorder. I used the reflexor for trim and climbed to 3,000 feet for some more elongated oval holes in the air. I returned for landing and did not trim the elevator like before so I had two landings instead of one. The roll out was to the end again as I landed long (1,000 foot mark). The CHTs stayed around 400°F. Total time in the air was 30 minutes with a max speed of 147 mph.

Lesson learned:

  1. Trim the airplane using the reflexor during the final approach for full elevator travel (hint from Jerry M.)

 

23Jul14 my fourth flight

Another calm morning and my support crew had gotten smaller but my wife was there. My plan was for a 30 minute flight staying within a 5-7 mile radius. The takeoff on 28L went well, again keeping on the centerline. I used the reflexor for trim and climbed to 3,000 feet for some more back and forth ovals in the air. I did some slow flight and tested out the use of the air brake ”belly board”. The test went well and I could feel it slow me down without any noticeable pitch change. I returned for landing and decided to deploy the air brake at 110 mph on downwind. I made sure to get my base leg at 100 mph and my final at 90. I still had a long glide in ground effect but it settled onto the runway at 80 mph and I was able to taxi off at the 3,000 foot mark. The CHTs stayed around 400°F. Total time in the air was 30 minutes and the max speed attained was 161 mph.

Lessons learned:

  1. The use of the air brake is a wonderful thing also.
  2. A slower approach speed equals less runway length required.

 

Flights five through ten

These flights were all in the 20-50 minute range with nothing significant to report. The landings went very well with minimal amount of wind but hot days which had density altitudes of 2,000’ plus from an airport at sea level.

 

18Oct14 my eleventh flight

A beautiful clear blue sky morning with a little bit of wind 10 mph relatively down the runway. The take-off was normal and I flew my racetrack near the airport at 3,000 feet AGL. After 25 minutes I decided to return so I reduced power to about 2200 RPMs and as I got to 2500’ the engine stopped producing power but the propeller was wind milling. I turned on carb heat, climbed to 110 mph and checked all switches. Then I pumped the throttled twice and the engine sputtered and quit. I then pulled the throttle back to idle and fed it in slowly and the engine power came back so at that point I was at about 2,000’ so I headed for the airport which was 4.6 miles away. My landing was a little hot so I used all the runway and parked the plane and took the cowling off for an inspection. Nothing was missing or out of place.

Temperature = 73°F, DP = 67°F, Humidity = 68%

Lessons learned:

  1. There was one warning sign after reaching cruise altitude in that the RPMs dropped and I thought it was the friction lock.
  2. The O200 is considered an “ice maker”.
  3. Use of carb heat during a decent is a good thing.
  4. Install a carb temp sensor, which I did.
  5. Carb icing chart www.ez.org/t/carb-ice

Q-Talk 168 - Flipping the Board

Belly Board mod that rewards you with yet another GUARANTEED  .003 mph speed gain.

By Jerry Marstall

[EDITOR'S NOTE: This article is another "speed mod" provided by Jerry Marstall. You can read about more of his work in Issue 166. Thanks again Jerry!]

I mounted the belly board on my Tri-Q according to plans, hinged at the back to open to the front.  By designing the belly board to open to the front, the linkage was quite basic.  Simply release the handle and let the wind open it and simply pull the cable to close it.

 I have never liked this implementation for the following reasons:

  1. I wasn’t able to get the corners of the board to stay up tightly within the fuselage.  As a result,   I always felt that the airstream was probably pulling the board open a bit costing me airspeed/fuel.
  2. Whenever I opened the board it scooped up exhaust fumes – not good.
  3. If the retraction cable were to malfunction, it would fail to the open position requiring a timely landing before being asphyxiated or running out of fuel.

Hinging the belly board at the front for a rear opening addresses all of these concerns.

While it has always a concerned to me, I confess that it wasn’t enough of a concern to cause me to do anything about it over the 17 years my Q has been flying.   

It wasn’t until the 2014 Sun N Fun Q-form when Richard Kaczmarek of Fast Little Airplanes fame showed up and mentioned he had turned his board around to hinge at the front. That peeked my interest.  I thought, this should be simple enough.  I’ll simply turn the belly board around and somehow attach it to the front of the belly board cavity. 

The challenge became how to open the belly board in this configuration.  The original mechanism design for opening and closing would no longer do the job.  As I previously mentioned, in the original design, the belly board acts as a scoop with the air stream holding the belly board open.  A tug on the cable would retract it.  Hinging the board at the front meant the mechanism must now force open and hold the belly board into the air stream that is trying to force the belly board to close. 

To solve this problem, Richard installed a direct control tube to the belly board for deployment and retraction.  As usual, I chose to make things more difficult by wanting to retain my present control handle and cable linkage to the belly board.

Here is what I did.  I’ll address the easy step first - relocation of the hinge; turning the belly board around 180 degrees. 

1.  Remove the piano hinge from its attachment point on the fuselage by drilling out the rivets.  Do not remove the piano hinge from the belly board.

2.  Make a paper pattern of the hinge side that is opposite the belly board.  Make the pattern the exact size of the hinge leg and mark the center of each mounting hole.  Put it aside.  More on this later.

3.  Above I mentioned, “. . . simply turn the belly board around and somehow attach it to the front of the belly board cavity.” For this to fit properly, the belly board had to be originally cut as a perfect rectangle leaving you with a perfectly rectangular cavity otherwise the board won’t fit the hole when turned 180-deg.  Unbelievably, my belly board fit the hole nearly perfectly.  That isn’t my typical luck.  If yours doesn’t fit, you will have to modify the shape of the belly board to fit the shape of the cavity.  Suggest you modify the edge opposite the piano hinge so you won’t have to remount the hinge.

4.  A length of 1”x 1” aluminum angle is used to reattach the free side of the belly board piano hinge to the fuselage.  I used a hand-held hack saw blade to scratch out a slot in the foam the thickness of the aluminum leg (1/8”) between the bottom fiberglass skin of the fuselage and the foam that forms the fuselage shell.  This slot runs the length of the cavity and is parallel to the bottom fuselage skin.  The slot recedes enough to receive the base leg of the “L” of the aluminum angle.

5.  To attach the angle aluminum to the hinge, with the horizontal leg from the hinge slid into the slot you carved, position the vertical leg of the hinge (A) flush up against the aluminum angle (B), pushed tight against the hinge pin.  Clamp the vertical leg of the hinge to the vertical aluminum angle.  Make sure to open and close the belly board to ensure that it will.  Then drill each of the mounting holes for 1/8” pop rivets and rivet the hinge to the aluminum angle.

Flipping the board

6.  When satisfied with the fit, secure the belly board in the up position (good ol’ duct tape).  Retrieve the hinge template that you made in step 2.  Align the template with the hinge and tape it to the bottom of the fuselage.  Drill the 1/8” holes for the pull rivets through the template, bottom of the fuselage and horizontal leg of the aluminum angle.  If you want to countersink the pop rivet heads, now is the time to do it.   Then from the underside, pop rivet the horizontal leg of the aluminum angle to the bottom skin of the fuselage.  You now have a belly board that opens to the rear.

7.  The next challenge is to fabricate the mechanism to open and close the belly board. The problem is space.  There is only 1.5” between the bottom of the main gear bow and the top surface of the belly board when it is closed.  In this small space needs to be a mechanism that can force the belly board out into the wind stream at some predetermined angle.  I chose 80-degrees which required the trailing edge of the belly board to open 8.5”. I finally settled on a scissor styled mechanism.

Mechanism Right

I strongly suggest fabricating the initial mechanism components out of a material other than aluminum, such as 1/8” plastic, because you will probably make more than one before getting the geometry right.   Since I am not an engineer, there were no fancy formulas for me – lots of do and redo.

The final two scissor arms are constructed from 1/8” aluminum and are each approximately 3” long.

Since I chose to retain my actuation cable, I already had one pulley mounted in front of the landing gear bow.  In order to get a straight, horizontal pull on the scissors, it was necessary to mount another pulley beneath the original pulley.

Pulley Mechanism

 You guys with conventional gear will probably need a different solution.  A way of testing your mechanism design is to hold the belly board up with your hand and attempt to deploy it with your actuation control handle.  If the belly board cannot be forced down, your geometry needs modification to gain the appropriate power advantage.

8.  All that remains is a means of retracting the belly board out of the wind stream.  I installed two springs, one attached to each corner of the belly board trailing edge with the opposite ends attached to the seatback bulkhead.

Spring Mechanism

9.  Now for the fun part.  Pull/push your actuation handle and see if it deploys.  Now release the handle and listen for the belly board to slam shut.  I discovered that the actuation cable was hanging up on the bolt head that attached the lower scissor arm to the belly board.  That is why you see the “dowel” on the bolt.  It keeps the cable from hooking on the bolt head. 

All together

Flight Test:  When I first deployed the belly board, the nose quickly pitched up about 5-deg.  The original board was a scoop which pulled the nose down, now it seems to work as a lifting surface.  I simply push it over, allowing me to point the nose down for a good view of the runway. 

No more fumes, better runway view, less drag and if the mechanism malfunctions, it will fail to the closed position.  Why didn’t I do this years ago? Thanks for the push Richard.

 

 

 

Q-Talk 167 - Airventure 2014 - QBA Forum

Quickie Builders Association AirVenture Meeting

31 July 2014 - Homebuilders HQ Porch

By Mike Bergen
Baltimore, MD

Airventure QBA Forum

I led the meeting and although I was twenty minutes late, three QBA members had already engaged in a general discussion. The following people attended:

Terry Crouch, Bettendorf, IA - Still flying his Quickie with about 900 hours on it.

Hardey McDaniel - Marion IN - Hardey came to the meeting last year as well. Q1, N87HN and Q2, N95LR. He talked of pegging the tailwheel on his Q2 to restrict the movement because of a ground loop after a recent flight. His Q2 has the Jim-Bob Six-Pack mods that include the full swivel tail wheel. He bought a 40x40 foot hangar and is waiting on some parts from Richard Kaczmarek to get flying again.

Dave Peterson, Blaine, MN. Has a Q1, N35DP. Still interested in electric propulsion as reported last year.

Paul and Tama Fisher, Taylor Ridge, IL - Q200, N17PF, 1,500 hours since 1990. Still flying the Quickie and is flying an RV as well.

Jim DeBower has one of the first Quickie Q1’s. It has been sitting in stored condition for several years with the canard exposed to sunlight. He is in repair mode and tackling a gas leak. He was concerned about UV degradation to the exposed end of the canard and so he conducted a static load test with the addition of 1700 lbs of sandbags to failure. He is going to build a new canard and is motivated to get it flying again. He is currently having fun flying a Weed Hopper ultralight.

I (Mike Bergen), Baltimore, MD flew my 1960 M35 Bonanza into AirVenture and plan to attend FOD. Still working on the Q200 after 30 years. Completed the new composite engine baffle/plenum and I’m working on mounting the cowl.

Barry Weber built a Q200, N189BW, and sold it to a Canadian man in Las Vegas. Three months later the new owner ground wrecked it.

I provided an update on Richard Kaczmarek’s battle with illness last year and his move to South Carolina. He is getting reestablished and will be providing parts again. He has found a reliable heat treat facility and has met the quality assurance check.

I went on to support Richard’s claims. He delivered Imrann Faruque’s Tri-Q nose gear and it passed the 3-G drop test that Imraan conducted following its reinstallation to the Quickie.

I told everyone that I communicated with Sam Hoskins prior to my trip out and he indicated that he would not be at AirVenture unless he was able to race. He wasn’t quite ready.

Toward the end of the meeting it was a real pleasure to see Norm Howell appear at the Homebuilder’s Porch. Norm built a Q1, N17UQ, in 1989 when he was in college at 19 years old. He went on to pursue a U.S. Air Force career as a pilot and has since landed a job as a test pilot. He claims that the build and test flying of the Quickie was very instrumental in opening doors throughout his flying career. The aircraft is now owned by Nelson Ham in Newton, MA. Norm now owns and flies an Aerostar.

I provided a reminder for Field of Dreams in Orange, MA, the last weekend in September. Terry and Paul said they would try to plan for it. Their plan is to swing by and meet with Sanjay so they can all fly to FOD together. I testified to the great host that Dave Dugas was last year and the fine job done on the local cuisine.

Q-Talk 167 - Airventure Cup Race Results 2014

Reg Collects His Award!

 

[EDITOR’S NOTE: Sam Hoskins was conspicuously missing this year at the AirVenture Cup race (much to the relief of his fellow competitors). However, this doesn’t mean that Quickies were not represented in the field. Reg Clarke turned in a blistering average speed of 218.98 MPH (I think we can safely call that 219 MPH) with his 150 HP Highly Customized Subaru Powered Q2 and won the Sprint-T class. Did we mention that Reg’s plane is FOR SALE? I think he might have just improved the resale value! Congrats Reg!]

 

2014 Experimental Winners


Unlimited

T. Paul & Pam Tackabury
Lancair IV, 346.24 MPH​​

Sport

5. Lee Behel

Lancair Legacy, 324.69 MPH​

Sport SX

30. Harry Hinckley

SX-300, 328.33 MPH

Sport FX

9. Tony Crawford

Venture FX, 274.99 MPH​

Formula RG Blue

38. Mark Quinn
Lancair 360, 254.12 MPH

Formula RG Red

24. Bob James & John  Corcoran
Lancair 320, 238.04 MPH

Formula FX Blue

91. Bruce Hammer

Glasair 1 TD, 274.05 MPH

 


Formula FX Red

48. Jeff Mallia

Cozy MKIV, 233.30 MPH​​

Formula RV Blue

16. Charles Greer

RV-6, 228.51 MPH​

Sprint

83. David Adams

Long EZ, 207.84 MPH

Sprint-T

2. Reg Clarke

Quickie Q2, 218.98 MPH​

IF1

15. Creighton King

Cassut, 186.67 MPH

LSA

99. Norm Hendersen & Mike Dzurko

RV12, 126.69 MPH

 


To see more Beautiful Photos of the racers check out Geoff Sobering's site here.

 

 

Reg casually chatting before the race!

 

Reg crossing the finish line

 

Xpresso tied down

 

Xpresso in chocks

 

Beautiful Xpresso

 

 

 

Q-Talk 166 - Composite Build Competition at FOD?

Guys,
I would like to propose a composites building competition at FOD this year.

I'm thinking give everyone 30 days or so to build a Rutan confidence layup (bottom of page) using whatever epoxy or process they like, with the requirement that they document it fully. You bring it with you to FOD for testing with the group.

At the field, we have a gauge to verify it does not exceed the cross-sectional area limitation, and a scale to weigh the part. A couple of bricks and some weights (with a larger scale) would suffice to test the parts. You can enter several parts, but only your top result is used for scoring. Score is based on *specific* strength, ie failure load normalized by part weight.

I can probably put together a lot of the competition except some of the parts: the heavy duty scale (300-350lbs max), bricks, and a bunch of weights that I'm not going to fly there with (barbell weights would suffice). It'd be nice if someone with access to a laser cutter could cut out the gauge for accuracy.

In any case, this seems like a good way to both get a sense for the build quality that people are turning out, and to encourage good practices (eg, VARTM process generates stronger parts, etc). I've specifically set up the requirements so that it can be tested safely and at home so that people can go practice themselves.

If all this sounds a bit wordy--I took a stab at this process a while back myself (Shown Below.) Let me know if you think this would be a popular event and we can start formalizing the rules and maybe some kind of prize. I know I'd have a blast testing parts with you guys but we need about 10 entries to really start learning from it.

Best,
Imraan


LEGAL DISCLAIMER: This document is provided as an incomplete record of events to inform those conducting similar tests and is not intended to serve as design advice. Author does not warrant that it is complete, comprehensive or accurate, or commit to its being updated. You agree that making this information available shall not be seen as the provision of design advice, and therefore I, my heirs, employer, and/or any other agent acting on my behalf are not liable in any way for its use or for the consequences of any actions taken on the basis of the information provided.

Load Testing of a Composite Fiber-Reinforced Laminate Beam

Imraan Faruque
This email address is being protected from spambots. You need JavaScript enabled to view it.
3182 Glenn L Martin Hall
College Park, MD, 20742, USA

I. Introduction

Due to my inexperience at composites work and the need to perform a structural repair on my aircraft, I elected to evaluate both the original load characteristics of a composite fiber reinforced laminate structure and the characteristics after subsequent failure and repair.a

II. Theoretical Stress Estimate

The Rutan confidence layup described in Moldless Composite Construction was selected as a standard test specimen. The beam is composed of a 1/4in urethane foam core with 2 layers each of bidirectional and unidirectional woven glass on the top and bottom as seen in Fig 1(a). The relative simplicity of this structure allows for analytic results and straightforward reproduction by other researchers of the results described herein, and the sample lends itself well to simply supported moment testing.

The structural member was modeled as a simply supported beam loaded in the geometric center of the beam length as seen in Fig 1(b). This load condition imposes both sheer stress and a bending moment stress, however, the bending moment stress will be shown to be higher and is expected to cause failure, as glass-fiber and resin structures have a lower compressive yield stress.

 
Figure 1. Rutan confidence layup cross sectional dimensions and load test.

Figure 1. Rutan confidence layup cross sectional dimensions and load test.

 

A. Shear Stress Calculations

The beam has an estimated cross sectional area of Aw = 0.18818in2. Shear force is maximal at the supports with Vx = F/2, and sheer stress Shear Stress Formula.

B. Bending Moment Stress Calculations

Equivalent peak bending stress at break force Fb is

Break Force Formula

If modeled as a solid structure, an equivalent section modulus for a solid structure is Sx, s = 0.06913in3 .

However, the structure is not solid. Approximating as a hollow rectangle, Sx = 0.03387in3 .

III. Experimental Methodology

HexCell's EZ Poxy was selected, due to its favorable structural properties. Epoxy was mixed by weight with a ratio of xxxx. Initial layup was conducted at a temperature of 77°F and 40% relative humidity on a glass preparation surface cleaned with acetone. The sample was allowed to cure for 18 hrs before being removed from the surface and an initial trim conducted using aviation shears.b The sample was then postcured in an unventilated glass enclosure subjected to solar heating for 42 hrs.

 
Figure 2. Layup construction.

Figure 2. Layup construction.

 

Load testing was conducted as a simply supported structure, using a pair of standard bricks and a load applied at the center. The load testing fixture is shown in Fig 3.

 
Figure 3. Load testing fixture under load, and failed component.

Figure 3. Load testing fixture under load, and failed component.

 



IV. Results and Discussion

A. Original load test

Load testing began at 145lbs and increased to 210 lbs. Due to lack of calibrated weights greater than 210 lbs, dynamic loading of the 210lb weight was conducted, and failure occured at an estimated 225 ± 5lbs. Failure occured at the point of load application, showing compressive failure and delamination in the upper surface. No damage was apparent visibly in the lower surface.

While supporting 210 lbs, the sample experienced peak shear and bending stresses of 0.56 ksi and 25 ksi, respectively. At 225 lbs, the sample experienced peak stresses of 0.60 ksi and 27 ksi. Room temperature cured E-Z Poxy alone has a strength of approximately 8200 psic , indicating that the glass fibers have significantly strengthened the structure.

B. Repair

The sections that were visibly damaged were removed as seen in Fig 4 (approximately 1.5 in long), and a urethane foam plug shaped to replace the removed foam. The foam was painted with a 1:1 micro slurry, and remaining voids filled with 2:1 flox mix. Actual epoxy mix was xxxx. 2 layers of BID and 2 layers of UNI measuring 3 in long were then applied, and the part allowed to cure for approximately 68 hrs in the solar enclosure.

 
Figure 4. Damaged material removed for repair.

Figure 4. Damaged material removed for repair.

 

C. Repaired load test

Load testing again began at 145 lbs, and proceeded to 210 lbs without only elastic deformation. After a 230 lb load was added,d plastic yield failure was observed. Again, failure was in the compressive loading of the upper surface as seen in Fig 5, but the failure occured adjacent to the repaired area, suggesting that the repaired area had been restored to full strength and the lack of staggered plies now created a stress concentration. Minor damage was noted to the lower plies as well, as seen in Fig 6.

At a 230lb load, peak sheer and bending stresses were 0.61 ksi and 27 ksi.

 
Figure 5. Repaired beam after testing.

Figure 5. Repaired beam after testing.

 
Figure 6. Failure after repair, including two damaged points on the lower surface.

Figure 6. Failure after repair, including two damaged points on the lower surface.

 

V. Conclusions

A composite beam structure was fabricated and loaded in bending. After failure, the sample was repaired and re-tested. The original and repaired samples exhibited failure at an overall load of 225 lbs and 230 lbs, respectively. Both held a proof load of 210 lbs, corresponding to a solid-beam-equivalent peak bending stress of 12 ksi. Modeled as a hollow rectangular beam, in both cases, the structure failed betweend 25 and 27ksi of bending stress. While he original sample failed at the point of loading, the repaired sample failed at the terminus of the plies added during repair, suggesting that the additional plies had concentrated stresses at the edge of the repair. Additional stagger of the plies could reduce this concentration. Additionally, unavailability of a loading structure with adequate capacity complicated the original test, and it is suggested that the original test should be repeated with a calibrated load to failure.

Footnotes

a This document is provided as an incomplete record of events to inform those conducting similar tests and is not intended to serve as design advice. Author does not warrant that it is complete, comprehensive or accurate, or commit to its being updated. You agree that making this information available shall not be seen as the provision of design advice, and therefore I, my employer, and/or any other agent acting on my behalf are not liable in any way for its use or for the consequences of any actions taken on the basis of the information provided.

b Minor delamination was sustained near the terminus of the lofted structure during removal. The sample was still usable for load testing, as this area is subjected to low bending moment stresses.

c Manufacturer data. Increased to 10 ksi if postcured 150◦ F for 2 hrs

d 210 lb human + 8x8x16 cinderblock


From Q2 Plans - Page 3-20


CONFIDENCE LAYUP

.....The second practice layup is one intended to give you confidence in the strength of your work. This layup is a sample of composite sandwich structure and is typical of the load carrying structures in your Q2. When this layup is finished, and completely cured, you will subject it to a simple load test, and thus demonstrate the strength of your workmanship.

.....First, tape a piece of waxed paper about 30 inches long to the top of your work table. Shape a piece of green foam as shown.

 

.....Go to your glass cutting area and cut the glass plies shown.

 

 

.....Lay up two plies of UNI, two plies of BID, paint the foam with micro slurry, and press it in the center. Then lay up the other BID and UNI plies. Be careful to work a11.air bubbles out of the corners. The best way is to stipple with the brush. The glass is oversized so that it can be trimmed to exact dimensions later. Trim to the dimensions shown after curing 24 hours, using a coping saw or band saw. Allow the piece to cure for four days at room temperature before the load test.

 

 

.....Now for the test: lay a broom handle or piece of tubing on the work bench and try to break the sample by putting all of your weight on the ends. A 200 pounder will stress the sample more than any part of your airplane is stressed at 10 g's.

 

 

 
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