Many aspect-ratio 6 wings have no washout at all, since the induced flowfield unloads the tips anyway, so the root stalls first. Avids are a bit over 7, so one might think we don't need the 4.5 degs of washout spec'd for them. That may well hold if you have VGs, and can't stall when landing anyway, since your nose would be pointed so ridiculously skyward. Without VGs, the stall, at least with the Avid STOL airfoil with cylindrical leading edge, is abrupt, so the washout may be there to soften the stall. Another argument for the washout is that it allows tighter-radius turns at low speed without the inboard tip letting go first. It could save your bacon if you inadvertently got too deep into a box canyon. If your short wings are already built, you may be stuck with the washout you get by extending them. Otherwise, you'd be adding stress to the wing structure, unless there's a way to relieve it.
If you look at the picture of the wing sandbag load test in the original brochure, you'll see that the cantelevered part of the wing outboard of the strut attachment shows the greatest bending deflection, and clearly the highest spar-bending stress is right at the strut attachment. If you have the wooden "spar stiffeners" I wouldn't extend the span, since these only prevent the spar tube from crimp failure. If you have the aluminum tube internal stiffeners with the vertical web, you have a spar stiffener and strengthener, so should be able to carry more bending load. In this latter case, by how much you can safely extend the span should be the subject of an engineering stress analysis. With an extended span, maximum loads will be higher in other places in the airframe as well. To first order, the max bending moment (and bending stress) at the strut attachment point varies as the cantelevered span squared.
Sorting things out is difficult, especially with very little background in biological science. There are simple and cheap solutions to non-life-threatening things like leg cramping, so I typically spend some time online going to multiple sites and look for agreement. Sometimes I will sit through a 30-minute speil with the predictible $50 / bottle ending, just to see what the critical ingredient is. To justify the price they usually include a set of exotic-sounding but essentially useless all-natural ingredients. It's an interesting game. Still, for sigificant health issues, I am wary of oversimplification, and put my trust in mainstream medical science.
I like the rudder trim idea, but I don't have any scissors that big! Springs and maybe a turnbuckle would seem to do. My old Tri-Pacer had a primitive aileron-rudder interconnect. Neat idea, but difficult to do on the Avid, I reckon. Maybe stiffer rudder springs would reduce the tendency to wallow about in turbulence, by effectively making the fin seem bigger. Oh, on the CG issue: I installed a luggage compartment in my C, which I intend to use. This will certainly help move the CG aft.
Actually, I am very close to test-flying a very simple relief tube system that uses a men's external condom-style catheter, connected to some small tygon tube that runs about 1/2 way down the inside of my pantleg before emerging. This quick-connects to another tube anchored to the seat truss, that runs about 2/3 the way down the inner landing gear strut trailing edge. A little extra tubing makes sure the system remains intact even in a hard landing as the LG flexes. Preliminary testing indicates that this is quite secure; when the moment comes you can just let go. It feels like you're peeing your pants, but you stay dry! Oh yeah - you have to designate one junky pair of pants for flying, as you have to make a small opening where the tube emerges to outside your pant leg, so you can plug it in to the airplane. The catheters are painless, come in sizes ranging from PeeWee to Magnum, so you have to first establish the correct size. The catheters are made of thin silicone rubber, and have a weak adhesive on the inside, which keeps it on, and assures a good seal. The distal end of the catheter fits snugly over 1/4" tubing, making for a secure seal. They can be worn for up to 24 hours, and cost about $2.00 each. There is, however, the potential for ending up with a bit of a sticky dicky! They say the adhesive comes off with warm, soapy water. Getting out of the airplane, say for getting gas, etc must be done carefully, as you have peed uphill, so disconnecting has risk. In my system, I keep nearby a small stopper for use on the tube running down my pantleg, which I will carefully install before getting out! I can include some pix of the system if there's interest. Coffee flavored salty virga! Yeah!
Hi Leni, Typical CG ranges between 12.4 & 12.8 in. But the real problem is not having flown in smooth air for a while. It's really just a matter of me whinging a bit too much. As you well know, the Avid C has no provision for pitch trim except the flaperons, so I have a simple stick-force mitigation setup with an adjustable-tension spring as a poor man's pitch trim, kinda like JimChuk's bungee setup. That, along with power and flaperon settings are what passes for trim on my machine. Once I get the opportunity to set up for cruise in still air, I will definitely take a look at rudder trim. Currently I have no tab on the rudder, and hopefully none will be needed. I'm planning an 880 nm flight out to Ft Collins, CO for mid August, and am trying to get all important issues resolved beforehand. Biggest Q? is what to take in case of emergency. I am thinking warm clothes and food, water, matches, and some kind of first aid kit. I am now not planning any leg longer than about 150nm, maybe shorter coming back against the weather. Headwinds really slow these poky birds down! I plan on having maps with course drawn on them as backup for the GPS (my Samsung tablet). And I think I have a viable solution to the problem you so eloquently addressed. Could launch a new thread, if I can keep the language such that I don't inadvertently get myself kicked off the site!
Wow, Leni, that's hard to top! I dunno about the rest of you mugs, but my bird is like a helo, in that left alone, seemingly would love to dive into the ground all on its own. Just putting on or taking off a jacket is next to impossible. Toss in a little turbulence, and staying rightside up and pointed roughly in the direction of travel becomes a full-time job! Of course almost all airplanes suffer from spiral instability, as this is preferable to Dutch roll. Nobody enjoys puking!
On the magnesium issue: The oxide form is cheapest, and seems to stick with you longer, but may predispose one towards diarrhea. The glycenate and citrate forms are said to have greater bioavailability, but are typically sold in smaller doses per pill than the oxide form. My read on this "bioavailability" is that it gets into your bloodstream faster, but may not stick around as long. The pill bottles advocate 3 pills a day. So I, for one, am back with the oxide form. I now have cobbled together a relief tube system. This allows me to stay hydrated, which will help with leg cramps. Hell, I can even have a cup of coffee at the airport cafe!
My Avid C STOL has a 582 with 3:1 C-box. I have been looking into swapping out the 3-bladed IVO for a PowerFin prop, to reduce rotational inertia for smoother idle, less forward mass for a small CG improvement, and improved prop section shapes and blade twist, hopefully resulting in improved cruise efficiency. I am not impressed with the IVO's sharp leading edge and weird twist distribution, and feel that it might be leaving a more-than-insignificant amount of performance on the table. Does anybody out there have experience with PowerFin Props? With the biggest "F" blade, can I get away with a 2-bladed prop instead of 3? There's more to life than static thrust.
I too was at one time contemplating a revised seat design, but in the end just decided to use a small pillow for some semblance of lumbar support. But man the Avid sure is short on legroom, no matter what you do with the seat. Maybe it is worth a second look, though. I agree that if the shape is right, you don't need much padding. Good luck!