Q-talk 37 - LETTERS

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Category: Q-Talk Articles

Published: Thursday, 31 December 1992 06:11

Written by Jim Masal

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Dear Jim,

The idea of type fly-ins is good. Mary and I have attended 4 - "Canard Type" fly-ins thus far. As you'll recall from Olathe, we were definitely an unrecognized minority ... but I don't think we should give up. The larger group can attract more people and provide opportunities for broader areas of technical discussion with both the Dragonflys and the Rutan group (let's try to keep that door open too!).

Changing the Ottawa fly-in to Labor Day weekend might be a good thing. I would still try to come on that date.

Art Jewett, KY

ED. NOTE: Your wish is my command:

And to your very good point regarding the wealth of technical information that we can glean from the Dragonfly boys and Rutan's EZ bunch, get a load of this:

DELAM/DISBOND FOLLOW-UP

Back in DBFN #41 (page 5) we had reprinted an article on structural degradation of foam cores that was published in "The Canard Pusher" newsletter put out by the Rutan bunch out of Mojave. To follow is a follow-up article going into more detail on the subject. I consider these gentlemen to be the "Pro's from Jersey" on the subject - Spud

From Mike Melvill

So far, we have received only one letter from a builder with a problem in this area. This aircraft is a Q-2 and, normally, we would not presume to comment on someone else's design but this particular problem could so easily have resulted in an in-flight structural failure that we felt morally obligated to say something about it.

During a landing that the pilot said was not any harder than other landings he had made, the canard (also the landing gear since the main wheels are mounted on the tips of the canard) failed. The top skin just inboard of the fuselage side, buckled and the canard folded up. Subsequent sectioning of this area showed a large percentage of foam had "melted". This builder/pilot suspected that this melting damage was caused by excessive heat from the sun while tied down outside in Florida. He included three photographs of the section of the damaged canard.

We at RAF (Rutan Aircraft Factory) have not seen this canard, only the photos, but we have a different opinion. We believe this damage may have been caused by fuel leaking out of the fuel tank (above the canard) and seeping through tiny pinholes in the top skin and melting the foam. Styrofoam, be it blue or orange, fabrication billets or flotation billets, will melt when it comes in contact with any fuel, solvent, etc. Put a scrap of foam in a container of fuel and, in a short period of time, the foam will totally disappear. Pour a little fuel, avgas or mogas onto a block of foam and you will be amazed at the damage. The three photos supplied to us by this Q-2 builder/pilot, in our opinion, show classic fuel or solvent damage. One of Scaled Composites employees who has built a Quickie and a Q-2 informed us that the fuel tank is, in fact, mounted directly over the canard and that he had heard of this type of foam damage before.

All of the RAF designs have a fuel-proof barrier between fuel and Styrofoam. This barrier can be a sandwich panel of glass/PVC foam/glass or glass/urethane foam (Clark)/glass, but RAF feels it is absolutely essential to completely protect any Styrofoam core structure from exposure to fuel or any kind of solvent. In some cases, even the fumes of fuel or a solvent such as MEK or acetone can degrade a foam core to the point of causing a possible structural failure.

We have written a letter to this particular Q-2 owner and will be passing this information on to Jack Cox, editor of Sport Aviation. We are not criticizing anyone, it's just that this kind of damage is many times invisible and may not easily be spotted in a normal preflight. Any foam core, glass structure, while perfectly safe with an undamaged core, can become prone to catastrophic failure if the foam core is damaged. This kind of hidden damage could cause a serious accident. This is our only reason to bring this to everyone's attention.

To protect yourself from this kind of failure, it is critically important to prevent fuel from coming into contact with glass structure that has a Styrofoam core (blue or orange). The same goes for any solvent, be it MEK, acetone, Prep-Sol, Acryli Clean, or whatever.

To check your structure for possible delamination or dis-bonds, move the airplane into the sun or, at least, to where it is warm. This will cause any disbonded areas to bubble up (bulge) due to the air or gas in the void heating up and expanding. Carefully tap the entire area using a quarter (25-cent piece). Listen carefully for the telltale "hollow" sound when you tap an area that is disbonded or delaminated as opposed to the solid "click" sound of a normal structure. By carefully tapping and using a felt tip pen to mark the perimeter of the damaged area, you can outline any areas that need repair, then you can repair these areas, in most cases, simply by injecting a mixture of epoxy and micro-balloons, using a syringe. You will have to drill a number of small holes (to closely fit the needle) and inject the epoxy mix into the hole until it comes out of the adjacent holes. Keep moving the syringe around until forcing it into any hole will make it come out of the holes closest to that one. Now, move the airplane out of the sun into a cooler area. Place some plastic (Visqueen) over the area, cover that with a piece of flexible material (.032 aluminum) and place a lead shot bag on top of that. As soon as the epoxy in the cup has kicked off, remove the lead shot bag, the aluminum and the plastic. Carefully scrape the excess epoxy off the paint using a "plastic" putty knife. After a full cure, you can carefully polish this area and repaint. Sometimes the visual damage is so little it does not require repainting. Recheck the area by tapping with a quarter to assure that you completely filled all void areas. - Thanks, Mike Melvill - The Rutan Group.

I reprinted this article for several reasons: First off, I know we do not have a fuel tank over the canard and our fuselage/tank foam is Clark urethane foam, but I have seen several different styles of header tanks in the area behind the firewall which is over the canard. Any kind of leakage could be a definite problem. 2nd, There are some people that are "mopping down" their canard/wings prior to painting with MEK, acetone or paint thinner. 3rd, RAF has an excellent inspection and repair procedure that we all can use. I'd like to thank Mike Melvill of RAF for giving us permission to reprint this article and any other "Canard Pusher" newsletter information that might be of merit to the Dragonfly community. - Spud

The Buenos Boys (Aires, Argentina) lonesome, but plugging away on Q-1.

Jim,

I don't know why I spend this money ($48 Aus), but I like your Q-TALK. It sort of makes me feel I am not the only Quickie 1 on this planet. Although I think there is another Q-1, but not flying in Australia. My little VH-URP is a good little bird and gives me no end of pleasure. We have had the wettest spring/summer on record and a lot of weekends, etc. The Quickie had to stay in the shed as my airstrip was covered with water. The Rotax 503 gives me the confidence that any airstrip I can fly into, I can fly out with ease. So, I often fly into ultralight fly-ins where I am well accepted. They say that the Rotax in a Q-1 must be the fastest Rotax engine in Australia! Jim, keep up the good work.

Gordon Laubsch, Australia

ED. NOTE: Thanks, Gordon. I'm giving Gordon's address here so that one of you Quickie drivers can extend an arm of support to this lonely coast watcher who has pushed out the frontier of Quickiedom to the wilds (?) of S. Australia: P. O. Box 15, Kapunda 5373, South Australia. And surely, with the popularity of Australia these days, SOMEbody must be traveling in that direction and can bring back a report on his outpost.

FIRST THERE WAS THIS ......

Jim - I'm real pleased to report the first flight of C-GJWH (couldn't resist it so dropped a message on your phone box while on the drive home). I just want to acknowledge your and QBA members contribution over the 10+ years (exact number embarrassing - with kit #15, I probably hold the longest build time record). I used many tips, methods and mods suggested by members, and would have been one of the 90% who would not have finished without you guys. I am rewarded with an airplane that the test pilot said was the nicest flying homebuilt he has been in! It is however going to be bitch to land.

AND THEN CAME ......

Jim - Here's a late report on my landing incident last June and an update on our new canard and gear that should be finished by the end of June. Basically, I landed real hard twice, the second time causing the carbon spar to have a top surface compression fracture about 6" from the fuselage. I had done a lot (20-30 hours) of high speed taxi testing and could feel the chordwise skin "wave" that others had reported forward of the spar on the left side only. The right side is still undamaged and as good as new (I intend to cut it apart also to compare when I mount the new canard.)

The first hard landing was a lulu while taking some dual instruction. I cut power on short final, didn't drop the nose, and dropped in hard from high enough up to get an immediate 10 minute lecture from the test pilot. It made the wave very pronounced. You could see it flexing when I bounced the fuselage up and down hard on the ground. I bounced it as hard as I could to verify that it did not go back to the spar. The skin delamination and flexing ended several inches forward of the spar. The left and right wings had the same "flex" when viewed from the front (i.e. was not "drooping" or obviously weakened). There were no audible sounds coming from the wing when I bounced as hard as I could. I don't think that the spar was damaged at that point, but don't have any proof. I was convinced at the time that the skin "wave" that others had reported was largely cosmetic, but I don't think that's true anymore!

The second landing was solo. I kept 1000' to a long final and was stable in a left slip at 85-90 mph all the way down. I was a bit high and increased the slip angle to max, but held it too long. Rather than add power at the last moment, I tried to flare over the grass threshold and touch down on the runway. I had done a lot of taxiing in that grass to get longer high speed runs on the first 2000' of runway at that end which is in the newest and smoothest section. The grass was hard and dry. I bounced once onto the runway but heading for the left side (left wing low?). I left a left tire skid mark starting about 150 feet from the threshold, curving back toward the centerline. The spar then failed with a loud snap, and the plane settled quite gently, skidding on the stub and other two wheels. I did not lose directional control (tailwheel and brakes still working) and was able to steer it off to the adjacent concrete turnoff/run-up area. Not even a paint scratch on the rest of the plane.

The carbon spar top failed in straight compression. I didn't see any evidence of torsional twisting at all, but I'm sure it was a factor, or it would have broken on the initial landing, and not during a hard high speed turn with me standing on the brakes. The failure point is about 3" outboard of the elevator main phenolic bearing attachment fitting that is glassed to the spar (imparting additional strength). I.e. - it failed right where you would expect it to. I will compare the undamaged right spar when I cut it off to see if it also only has 3 layers of carbon or unequal thickness. It appears to be spiral wrapped but the third wrap didn't quite go the full 360 degrees around the tube. I don't know if this is normal or not, but I don't think this is "root cause" as I really schmucked it on. I ran out of elevator way too high (I remember that "Oh, Shit!" feeling very distinctly) so this one is 99% pilot error. Did not spend enough time getting to know the feel of the airplane solo and especially slow flight before doing circuits. Hopefully, I'm a little smarter this time around. One warning though - the LS tubular spar is not very tolerant of abuse, especially when you lose the strength of the 3 skin plies. Don't ignore that top surface wave - Mother Nature is trying to tell you something!!! If you compare the load carrying capacity of 3 layers of carbon fiber at the top of a 4" tubular spar (about 3" of effective length) to 3 layers of glass skin 16" long and 5" max wing thickness, you'll find that about 1/4 to 1/3 of the compressive strength of the wing is in the skin. So all you guys out there with waves in the top surface are landing with 2/3 strength canards. Not a big deal until you do something that needs more than you got left. My spar failed on rollout laying rubber in a right turn and not on the first or second bounce.

John Wirta found another airframe with the old canard on it locally after losing his Q2 to a tornado, but was only interested in it if there was a way to put inboard gear on it without going to a Tri-Q configuration. I agreed, so we are building buddies again. I also wanted the LS airfoil, but without the tubular spar, as did John after listening to the test pilots comparison between the GU and LS aircraft (he has a gorgeous ready to paint GU canard for sale if anyone is interested). Anyway, we went to Oshkosh '91 with a mission and spent a lot of time looking at landing gear on various airplanes and talking to Jim Doyle about his canard. We had pretty well settled on spring gear, probably aluminum, until we saw the Berkut and the Dragonfly with the homemade glass gear. Jim Doyle and his partner graciously supplied us with full size template blueprints, fabrication instructions and design calcs, etc. for the carbon fiber box spar LS canard. Their wing is well designed, stiffer, cheaper and just as easy to build as the original GU canard (I know as I've built two of each now!!) We modified the center section foam core to include some internal structure to take landing loads to the fuselage without being transmitted through foam. This consists of 5 additional parallel 4 ply "shear webs" 1.25 inches apart, that transmit loads between the top and bottom skins and out to the fuselage sides. We'll use two stiffeners and extra glass at the fuselage to take up the slightly more concentrated loads at the fuselage skin.

We built a vacuum mold jig and made two landing gears out of 3" roving E-glass for less than $250 each, not including the "oops" on the first try.

We loaded the gear to 1G on a hydraulic press before we put any 45 degree cross plies on, just to make sure that we are in the right ballpark. I think mine will be a bit stiff, so we are going to press it again next week so that I will know how many degrees to shim the wheels to get them vertical at gross weight. The gears are constant chord 4 1/2 inches wide and 1.25 inches thick at the fuselage skin with lengthwise UNI plus another 1/4 inch in UNI cross-plies for a max thickness of 1.5 inches. This tapers down to 5/8 + 1/4 = 7/8" at the wheel. Front and back are rounded to reduce drag. This is "beefier" than most to limit vertical deflection to less than 2" per G force with a low and very wide 80" stance at gross weight. Attachment points are modeled after the Tri-Q and Long-Eze (I like things that work). Total weight growth is estimated at 10-20 lbs, which is more than taken care of by the approx. 4-5 sq. ft. increase in canard wing area (no wheel pants) which should support an additional 60 lbs at max-wing load. My finished gear is 30 lbs (less wheels), which compares favorably with two 12 lb wheel pants (heavier than I expected!). The carbon box spar wing should be about 5-10 lbs heavier unless I can save on finishing weight, which is still a possibility. The axle points will move forward about 2 inches, giving a small forward shift in C of G, which is also offset by increased canard area and lift.

Needless to say with my proven skill at the controls, I'll be getting my favorite test pilot to do the honors while I run the video. Safe flying and see you at Oshkosh!

AND FINALLY THIS ......

Jim - I sure appreciate getting my QUICKTALK every other month, so here's my anti-up for '93 without having to be asked twice.

Also enclosed pics of the new gear installed and working. The weather was so rotten here last summer, with 14 very rainy weekends in a row (!) that I didn't get it all installed and primed until the middle of November. Then came the snow. Today it's raining again. Go figure.

I got in a couple of hours of taxi testing, but had to quit and go back and reinforce the tailwheel - got run over by the tractor that mows the lawn at the airport, and it had delaminated internally. I added 3 wraps each of UNI and BID, which makes it about 1 1/2 inches thick, and a lot stiffer.

I now have a painted stick driven into the ground behind the tailwheel to remind the guy to go around and not over (can't see the tailwheel in tall grass).

The taxi runs feel a LOT better with the inboard gear - much smoother directional control and no oscillating bounce to contend with. The gear has an 80" stance (same as a C150) with a lower C of G than a C150, so it feels very stable (can sit on the Canard wingtip and bounce as hard as you want. Cannot even lift the other wheel off the ground, or get the wingtip near the ground. I think I'm really going to have to work on it to break this one. So far the only thing that I'd change is the curve that we molded into the gear - it was designed to "straighten out" at 1100 lb gross. I think I'd change that to about 900 lbs for better aesthetics and wheels more vertical at typical single pilot weights.

John Wirta is in final, final primer and will have his painted in January. We've both booked off work for Oshkosh weekend, soo ..... there should be two strange looking Q-birds in attendance.

NAME: Bob Falkiner Q-2-2015

ADDRESS: 5195 MicMac Cres, Mississauga, Ontario, CANADA L5R 2E2

PHONE: Res: (416) 507-0638

Bus: (416) 968-4184

Fax: (416) 968-5311

September 3, 4, 5, 1993 3rd Annual Dragonfly/Quickie/Q-2/Q-200 Fly-In, Ottawa, Kansas.

Howdy Jim,

Are YOU working on your plane?? (NO, I'm STILL working on its hangar, though. -ED.)

OK, here's my big idea for the newsletter.

I would like to see if there is any interest in a big Q1 gathering at Oshkosh. The idea is to get 10-15 Q-1's (Rotax's preferred but I'm counting on the Onan boys for numbers) to form up as we progress across the country and all meet in Madison, WI on like Friday evening or Saturday and all fly in together. I won't even consider a cross-country flight like that again unless I can get 6-10 others to commit (weather excuses allowed, except from Capt. Nitro) and 2 or 3 from near me to fly with all the way there (safety in numbers I'm told!). Do not mean to exclude the Q-2's; they are more than welcome if they like flying slow! Present the idea and let's see if there is any interest. Send me an updated address/phone list and I'll call some of the guys close to me and talk them into it! (ED. NOTE: This has been tried before with dismal success, but if you want to give it one more try, you can be organizer. Anybody who will fly a Rotax Quickie 900 miles one-way to our Kansas Fly-in is on my "A" list of macho men. Want to?)

Jon Finley, Helena, MT

Masal hangar progress ... for those who wonder why I'm not out re-engining my Quickie. Getting close.

You can order a PDF or printed copy of Q-talk #37 by using the Q-talk Back Issue Order Page.

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