chasingmars

As a data point, a bare bow, right ot of the box before trimming or layups or whatever, weighs (in my case anyhow, my bow arrived this week) about 13.2kg (or about 29 pounds). I suspect we add alot more glass than we trim in chapter 9. That said, assuming you're looking at the "Cavalier" 1800lb rated arms, that 25# is for the bare legs only too, and a retract system has a lot more mounting & hardware mass. Not to mention that a lot of the load transfer is managed by the "bow" centrepiece, if you use two independant legs, you're going to need a much beefier attach structure to deal with the localized bending/torsion loads, or, if you put them on oleos for compression (probably necessary, the S-glass bow it it's own shock absorber, not so most aluminum gear), then you need to account for that weight and stucture to transmit those loads. And while the legs may only be 1" thick, that doesn't mean a 1" cutout. What about the wheels/brakes, the lines, the shocks, the mounting and swing mechanisms, all these require space and weight allowance.

Thanks Mark for the summary, that's exactly the sort of thing I was looking for. The archives are great and it's my usual first step, but for some topics, there's not always all that much concensus, and a summary from a flyer is helpful. cheers,

Apropos of this, I'm going to be skinning my fuselage bottom soon. Is it a reasonable approach to not embed any antennas in the fuselage, and still have sufficient separation, space, etc, using only the lifting surfaces and winglets, assuming a fairly capable full-IFR capability? Marker beacon antenna in the canard, navcoms in the winglet, GPS externals, what else am I missing? Are there drawbacks in orientation of the marker beacon transverse in the canard vice longitudinally in the fuselage? Thanks

For what it's worth, I break out exactly as mentioned in the opening post if I get the 285 on me. It also itches like mad. I see it almost as a benefit, in that I know immediately if I get any on me, and so can go wash it off right away (I use Orange/pummice hand cleaner for this). Another odd thing, if I get it on me, I get itches where it's not actually touching, really stong. Like inside the canal of my left ear or on the top of my scalp. This is more problematic, as these aren't places one can scratch without first stripping the gloves and decontaminating! I use the hand cream and nitrile gloves, and have recently begun long sleeve for any significant about of epoxy work, the long sleeves made a really big difference as I always seem to get my forearms on something, and the Ply 9 doesn't stop the MGS well enough to prevent a reaction. Generally speaking though, my reaction is localized to the contact point (except for the odd itches sometimes), and I don't have any issue with fumes or whatever (although I have started to use an activated carbon filter mask, just like the one pictured) when mixing significant amounts, as this is when I'm right over top of it, because I vac bag, I'm not over the layup as long as with a hand layup as the vacuum does a lot of the work of getting out the excess resin for me. One thing I learned about those masks, is that between uses the filters should be stored in a plastic ziplock to keep them from getting "used up" sitting on the bench. Anybody know if that's necessary, or how often to change the filters?

"delivers 50 miles to a gallon of regular gasoline - about the same as a large motorcycle" Or about what my Jetta TDI gets at 55mph. Interesting looking, but really, would you want to drive it on the road at speed, my guess is crashworthiness is not that great!

This is kind of scary, as it begs the question of how do you know the layups were right (or is just about everything pre-manufactured in the kit) Have you considered doing a set of core drilling and burn testing to determine the actual layups used for any of the original owner's glass layups?

If you model them as flat plates, which isn't entirely accurate, it generates very little lift *at zero angle of attack*, as angle of attack increases, so does lift. Eliminating the strakes removes a fairly large *roughly* flat plate lifting surface forward of the M.A.C., moving the centre of lift back, and I'd make an educated guess that this would have quite a significant effect on the aerodynamics of the aircraft at high angle of attack (i.e. approaching stall). But because of interactions with the rest of the wing, it's not clear on the extent and details. similar aerodynamic concerns arise if you make them lifting surfaces, moreover if you do make them full foils, you don't gain as much as you might think as you exacerbate an existing problem of the canard design, that being poor span load distribution, reducing the lifting efficiency of the wing, ironically, a poor foil inboard means the reduced inboard lifting effectiveness in cruise can actually increase the aircraft's overall efficiency factor (all else equal which isn't the case, the parasitic drag here makes this a losing game)

Most people here are builders and pilots, not aerodynamicists, and I don't know if it's the right audience to discuss fluid dynamics and theory of lift, etc. That said, before you launch in on Bernouli you may, if you already haven't, wish to look at Newtonian concepts of lift, and consider that it's not really an either/or thing, but rather, both are simplifications of relatively complex goings-on that involves viscous effects and such, and as models, aren't necessarily an exact representation of the details of the system.

Designing and building your own homespun constant speed prop? I have to ask whether you consider yourself both a competant engineer (of two or three types) AND a competent machinist? You may wish to look at what's involved in such a beast, the tolerances involved, and how much innovation you're interested in hanging your life on. "Some effort" is an understatement along the lines of... well, I suppose it could be done, but, yeah, engineer and machinist skills needed to a significant degree. As to fixed pitch props, while it takes more work that google, and much more work that just spitting out new questions in threads, I'd suggest that near forgotten breed - the library. A university engineering library if possible. There's a fair bit of (managable) math (if you get vectors, you can understand it easily enough), but a fixed pitch prop isn't rocket science. While there are computer programs to help design props, my own opinion is that if you don't understand what the computer program is doing behind the scenes, and why, at least to a pretty good degree, you probably should leave it alone. But that's just my opinion. As to contingencies - speaking as someone who's run out of epoxy... for best chances of finishing your plane, your action on running out of epoxy should be to obtain more epoxy, rather than design a CS prop. In the meantime, if there is a meantime, carve your next few pieces of foam, read the plans, etc.

Interesting, thanks. Indeed, it says 135kg dry, and it appears to be the same block as used in the automotive TDi's, which means it's probably pretty close despite being for an 80hp (@3300rpm) industrial version of that engine from 1997. I stand corrected on the weight issue, but I still think trying to pump a 100hp@4000 rpm to 200hp@prop rpm to be a very bad idea. This is playing very fast and loose with the numbers, saying 165hp as a 75% power figure is just over stock is seriously flawed. The block is certainly solid, but you have to consider the duty cycle. for the north american 1.9L PD, stock is 100hp. 75% of that is 75hp, about, and 165hp is hardly just over stock. Even if you baseline against the 2.0L european engine, which is 134hp in north american (Passat) form, and 140 hp in euro Golf V form and up to 170 hp in Euro Passat form (may be different engines), that's boosting the thing up when you're substantially increasing the duty cycle if you're looking at making 165ho your "75%". Maybe it will take it, but it's a substantial development project that I'd have little confidence in until it reachs whatever you make TBO and tear down a few. *derating* an automotive unit is probably more sensible in light of the duty cycles they were designed for. Moreover, it's torque that will govern bmep and therefore engine stress. Saying 200hp at 2700rpm (Lycomoing redline rpm, I believe) is the same as saying nearly 300hp at 4000rpm. There's just no way around that math. Brake mean effective pressure is the key index of engine stress (not the only factor in life, rpm does matter there too) and trying for 165hp at 2300rpm (what the Lyc turns I think, roughly, in cruise) makes for nearly 2.9 times the brake mean effective pressure in the cylinders. I suspect you therefore do need the PRSU to make enough power with this engine unless you're willing to sacrifice efficiency and static/low speed thrust to turn a smaller prop faster (which with a diesel *might* be a practical approach, and the flatter power curve lets you recover some of the loss of static performance) Still, by all means, prove me wrong, soon, cause I'm planning to try and figure a way to put a diesel in my plane I just had ruled out this engine when I reseached it.

Perhaps you could quote a source for that? Restating a disagreed with point in metric doesn't add much to the validity. I looked at the graph, I just disagree with the wisdom of using extreme hot-rodded performance numbers as a baseline for what you should strive for in aircraft use. There is a real enthusiast community with the TDi's and they can get astounding performance out of them for sure, way beyond design, but with what reliability? Remember that a hot rod does 30% duty cycle with occassional runs to 100% that last only minutes, an aircraft engine has to reliably put out 90% power for significant periods of climb, and 65-85% power continuously in cruise. This is not what even stock auto engines are designed for, and way off the design point for hot-rods. You should be looking at how much you want to DE-rate your automotive conversion not how much you can possibly boost it, and certainly not by 100%-200% over factory torque, that's not likely to survive. When you can take that dyno test and show that it will do that for *hours* at a time, then I'll be more convinced. Consequence of a broken engine is much higher at 10000 feet. Again, driving that much torque through an engine originally designed for 90-100 hp @4000rpm is asking for trouble. Yes, you can put beefier components in throughout, magflux everything, etc, but that adds to weight and cost. This is one reason I like the Mercedes V-6 diesel, because they have pushed them at high loads for extended periods over several stock units without failure in some publicity demos. If BD was cheaper than dino-diesel, on a source-to-consumer basis, it would be outselling it, by pure market forces. it's not. It's good, by comparison, one of the most competitive biofuels, but it's still, for the moment, pricier than fossil fuel derived diesel. I buy it anyhow, it's not that big a cost difference. Ah (edit) I think you mean making it yourself from used fry grease or such for that price... yes, you can. Do you want to run your plane on that? Maybe, if you've really got your process down, but if you don't, the residual glycerin in the fuel will varnish in your injectors and cause your engine to fail. There are other pitfalls there too. Great garage project for running the beater car than you work on yourself if something should happen, less ideal for when you're loading the family into a single engine airplane.

Some points: The TDi engine is quite heavy, I'm not sure where you read 300 pounds, are you sure you don't mean 300 kg (but that would be too much they are heavy, but not that heavy) If it's the 8 valve PD engine in current north american cars, pumping up to 200 hp is a very agressive increase in power (100% over stock) If it's the european 16V engine, then that's still 50% over stock. The TDi engines from VW really aren't good candidates in my opinon for aviation use, it mostly comes down to weight. Pumping up power to levels that street hot-rodders have is asking for trouble I think in terms of reliability. *Some* increase make be justifiable, given adequate engineering, but 100%?! I drive a Jetta TDi, rock solid engine, I like it a lot. but its a cast iron block, not even CGI, and not built with light weight in mind. Potential diesels that *might* manage a weight in line with aircraft use as an automotive conversion - Volvo's D5 (185 hp), Subaru's upcoming flat-4 diesel (which there's a derth of information on, so who knows), and maybe, if you can really get creative about managing weight, Mercedes new V6 diesel, but that's probably just too heavy. Remember that automotive quotes engine weights are usually dry and don't represent "installed" weights, and, even with a slower turning diesel, you'll need a PRSU, as peek power is up at 3800-4000 rpm (or a propfan with a thrust bearing assembly - since car engine cranks aren't designed for thrust loads).

Possibly with a compression ignition engine, turboed, at altitude, I'd say. Better bsfc to reduce consumption. Question is, can it be done light enough for effective use, and what are the bugbears hiding in the details along the way. I'm really wondering what the new boxer-4 Subaru diesel's going to weigh.

what I think you are talking about here is known as Mach Tuck. It has nothing to do with a lifting surface "stalling by itself". It has to do with a shift of the pressure distribution that occurs as the airflow over parts of the wing move into the transonic region and localized supersonic flow on the wing causes shock waves to form (the flow over the wing is faster than the freestream flow, and airfoils/wings have a critical mach number which is the freestream mach number that produces local M=1 flow) http://en.wikipedia.org/wiki/Mach_tuck

No, I don't think I missed your point. To be blunt, I think you're off a bit, no big deal, to be honest, I cring almost every time a pilot trys to explain an aerodynamics concept, you don't need to know how to design a plane to be a great pilot, just don't try to redesign the plane, after all, you wouldn't expect an engineer to hop in a plane and say "well, I know the theory, I can design part of this machine, so I must be able to fly it without any specialized knowledge or training" would you? The reverse holds too.

This is pretty dangerous, as it expects the pilot to know (a) Why an airplane stalls, and (b) how to set it up appropriately, and © based on assumptions that are incorrect. Ask a pilot (a) and most will answer "because you flew too slow", pressed, they clarify "below the stall speed". Stall speed varies with load and c.g. As to ©: An airplane stalls when the angle of attack of the airfoil exceeds some critical value, which is only more or less well defined (i.e. lift loss can be sharp or somewhat gradual depending on the foil's stall characteristics). You can stall an aircraft at any speed up to the square root of it's load limit times the 1g stall speed for that configuration. Above that, you run a risk of ripping the wings off instead. Trying to go fast only affects stall speed somewhat, in a way that is largely dependant on aircraft configuration. it in no way protects you from main wing first stall on takeoff. I suspect that a main wing stall on takeoff (by definition a phase of flight involving low speed operation) is much less benign in a canard than a canard stall (which would limit climbout angle or, if you don't have enough runway, be bad). With regards to (b), the pilot shouldn't have "be an aerospace engineer and set incidence accordingly" on the checklist prior to T/O, cruise and landing. As to the last part... Induced drag (from lift) becomes a very small component of total drag at high speeds, so doing wing things with AoA and expecting drag savings that are significant is unrealistic. Parasitic losses are your concern at the top end. Of course, not being able to get enough down elevator is another issue, and there is some advantage in being closer to neutral on the elevator when operating at high speed, but probably less than you suspect. Flirting with pitch stability and controlability problems is a dangerous game and I'd suggest not worth the trade. The real problem with trying to use variable incidence canards is that the concept misses a fundamentally fixed relationship. The airflow over both wings, at a distance, is coming at the fuselage at a fixed angle. That angle, modified by the incidence of the lifting surface, is therefore affecting both wings (yes, the wing behind the front is also affected by downwash, but that doens't significantly affect the conclusion), therefore, there is an optimum value of difference between the front and rear wing that, given the foils llift curve differences (and downwash), provides adequate protection from a main wing stall. increasing this incidence on the canard therefore, always, will reduce your margin for main wing stall. Decreasing it from this will therefore, always, increase your stall speed (a canard first stall, so perhaps minimum 1g flight speed is a better term). At the end of the day, neither is a good thing. Downwash and other second order issues complicate this, and make it a little less than strictly true, but it's basically the case, given that the elevator on the canard operates as a flap, and to a reasonable approximation, flaps do not significantly alter the maximum angle of attack of a wing.

I would suggest that it is useful to qualify mods listed in the wiki into two groups, flying, and unproven (that is, any mod who's examples haven't cleared their initial flight testing). Preferably, flying mods should list the registration number/s it's flying on (in those instances where it's not so common as to be routine (eg, electric nose lift).

I'm figuring I'll just throw it up in the air on my hopefully eventual first flight and hope it stays up there. Until then, I figure I don't really know what I'm talking about

I'd suggest you take a read of John Slade's site, you will certainly enjoy it if you want to use a turbo rotary. He's blazing the trail. In some cases, with bits of blown turbos. Car and motorcycles may not give you adequate background depending on how well you can extrapolate that the what happens when the atmosphere gets tenuously thin and what that does to pressure ratios, and the fact that as you climb, turbine output rises while compresser absorbed power falls.

Hi Hans... As you've already found out, your ideas, while potentially interesting from the perspective of a clean sheet of paper, are problematic as modifications. I thought I'd throw in my two cent, and try to add something constructive by adding a bit to Why they aren't likely to be successful. Bear in mind I'm only on chapter seven myself, so, take with salt. If you're trailering it all the time, well, the road is a harsher environment than a taxiway or the air, think about the ding you get when a stone gets thrown up on your windsheild, if it happens to the plane, hopefully you notice on your preflight! I guess you can always wrap it up in a quilted cover for trips or such. (edit: I did some musing on structural weight, but then on re-reading it didn't make much sense to me, so removed it) long and short is that easy trailering involves a *lot* more than a shorter main spar. Fuselage widening has been discussed to death, probably with more heat than light, but, at the end of the day, a fuselage, esp a boxy one like a Cozy, generates lift, and in a substantially different way than the wing. More significantly, there are, I think anyhow, easier ways of getting elbow room. Why? It won't really help for grass/gravel, and changing your thrust line will have very significant effects on handling. Moreover, remember these aircraft graze forward for ground stability when parked. With short mains, you'll worsen what is a livable design compromise. If you are thinking that by putting in a take off attitude you can move the short main back to avoid tip back, well, then you'll always be landing on your nosewheel. which is not good. At high power settings, the moment arm that the high mount engine produces will mean that the canard will have to carry more of a share of the lift and you can't offset this at the low end without risking deep stall, so at high cruise power you will kill efficiency of the wing (an issue canards already have and much of why they don't see as much real world benefit of their "all surfaces lifting" planform). By forcing the canard to work significantly harder than the main wing to counteract engine couple, you raise the induced drag (it goes to the square of the lift coefficient) and hurt performance. Only needed if you have no strake tanks, I think the plane can already go further than most bladders. But, I suppose ferry tanks are probably the easiest of the mods you'd proposed. Well, that's probably because airplanes are compromises by their inherent nature. The question is, is the Cozy the right compromise for you? If you have a compromise in mind that doesn't have an example, you can either design it, or accept the limitations of a design that's good enough. But I'd caution you as others have, the scope of what you proposed, well, to be honest, a clean sheet design would probably be easier and need the same level of knowledge and skillset.

I think I'm in this "wake up and smell the coffee" phase myself at the moment. My "good" ideas have done a great deal to slow me down, cost me money, and create parts I've needed to scrap. The further along I get, the happier I am with the plans. Like anything I guess, one starts not knowing what what doesn't know, then you start to figure that part out, and it takes a while sometimes.

This is, I suppose, as good a place to ask this as any: Are the Cozy canopies from both suppliers Polycarbonate (Lexan) or Acrylic/PMMA (Lucite, Plexiglass, et al)? Thanks.

Yeah, we may have three forums, but perhaps we can have one wiki? That would be in all our best interests I think... Was this regarding the phenolic micro? Positive, but the price premium isn't insignificant, and this is probably yet another improvement that doesn't need to be improved. More research needed (with gear I don't have access to anymore) to determine if there's a weight savings to be had here, my initial estimates are little bit of one at a cost of about $80/lb, with large error bars on the estimate. http://www.maddyhome.com/canardpages/pages/chasingmars/Misc/Phenolic%20vs%20Glass%20K20%20micro.pdf actually, the only reason I chose pdf is because I didn't like the HTML-export look, it messed up all my image placements and all and I wanted to keep it how it was laid out in my actual log. Anyhow, my pages are all off my root build log page, including the updates. Thanks for the positive feedback.

Alright, 20 more pages, I'm up to date now Including my Phenolic vs Glass micro experiment log. Which reminds me to add to the subject list and stay on topic: * Using Phenolic based micro instead of Glass micro.

I haven't knife trimmed since the day after I got my Fein, which I think was in chapter four. If you don't have a Fein with a HSS bit, you are missing the most labour saving tool for building this airplane out there, in my opinion. And far less risk of accidentally chopping off a finger using sharp blades on unevenly cured beta laminate that you didn't *quite* time right. Quite aside from it being impossible to knife trim a bagged part.