capi3101

Yeah, helicopters are pretty much out if you're going solely with stock parts. However, VTOLs are quite possible in stock. Let me point you to DocMoriarty's KSP Space Plane Construction and Operation Guide, which has an extensive section on VTOLs with stock parts and stock aero. It was written for 0.24.2 but the principles are still applicable to 0.90.

The stock game doesn't come with any bearing parts of its own. That said, I've gotten "bearing-like" results before utilizing Cubic Octagonal Struts and connecting them directly to launch clamps...

Well now - there's getting the plane up to transition speed as well. Granted, that probably doesn't involve all that much fuel, but it ain't exactly zero either... Good related question then - what is the Isp of Turbojets and RAPIERs in FAR? Are they any different than what they are in stock?

Okay - so general rule for a payload to orbit craft around 2500 m/s? That's pretty much the only kind of plane I flew while I was still in stock.

1) Alt F-12 to turn on the debug menu. 2) Pick the option that says "Whack-A-Kerbal". 3) Select your size/shape/mass options carefully. 4) Pick a target. 5) Aim carefully and use the middle mouse button to shoot. 6) ??? 7) PROFIT.

Alright - since I was able to prove earlier that almost 98% of the delta-V of your stack was coming from the core, I'm going to focus my efforts there. We have a stage that's 170.5 tonnes full and 26.5 tonnes empty, with 2500 kN of thrust and an Isp of 280. We're attempting to figure out how much is the maximum payload this rocket can lift to orbit. So, two possible limiting factors there - thrust and delta-V. We can solve the thrust factor using the same formula I was using earlier (T = Ft/mg) solving for mass and assuming a TWR of 1.2 (again, the generally accepted minimum figure). That gives us m = Ft/Tg = 2500 / (1.2 * 9.82) = 212.152 tonnes. Since we know the booster is 170.5 tonnes full, the maximum payload is the difference: 212.15 - 170.5 = 41.65 tonnes. Now to see about delta-V. For this, we'll add a payload mass to both the mass factors of Tsiolkovsky (which we'll call P), and set the target delta-V to 4500. So we have the following: dV= ln(M/Md)*9.82*Isp = ln((170.5+P)/(26.5+P)) * 9.82 * 280 = 4500 ln((170.5+P)/(26.5+P)) = 4500 / (9.82 * 280) = 1.636602 (170.5+P)/(26.5+P) = e1.636602 = 5.13768 170.5+P = 5.13768(26.5+P) 170.5+P = 136.14852 + 5.13768P 170.5 - 136.14852 = 5.13768P - P = (5.13768-1)P 4.13768P = 34.35148 P = 8.3021, the maximum allowable payload due to delta-V limitation. So the limiting factor of the booster's effectiveness is delta-V. We can confirm this by adding the two indicated limiting factor masses to the mass and dry mass of the booster and calculating delta-V: dV= ln(M/Md)*9.82*Isp dV= ln((170.5+8.302)/((26.5+8.302))*9.82*280 = ln(178.802/34.802) * 9.82 * 280 = 4500.007 dV= ln((170.5+41.65)/((26.5+41.65))*9.82*280 = ln(212.15 / 68.15) * 9.82 * 280 = 3122.397 I'm going to make one more pass at this just to see if the booster's performance can really be expected to be this bad; I have neglected the (negligible) delta-V contribution of the outboard engines after all. But I wouldn't be too hopeful.

Okay...so for boosters I always use the atmospheric Isp when I'm designing things - I treat it as the "worst case", because it at least accounts for some of the atmospheric effects. In reality, you'll have a smidge more delta-V than what I calculate here - just that disclaimer before I get started. Okay - so the core stage is 2x Kerbodyne S3-14400 tanks stacked and a 1x Kerbodyne KR-2L Advanced engine. That's 82+82+6.5 = 170.5 tonnes full and 10+10+6.5 = 26.5 tonnes empty with a 280 Isp and 2500 kN thrust. That stage has 5,108 delta-V by itself (?) with a TWR of 1.496. The outboard "booster stage" adds two Mainsails, which have a different Isp - you do the math there (divide the Thrust by Isp for each engine and tally that up, then divide the total thrust by the result) and the effective stage Isp is 300.4878. Then you've got - 4x Rockomax Jumbo-64 Tanks (2 per side), 2x Rockomax X200-16 Tanks (1 per side) and 2x Mainsails. That stage has 36+36+36+36+9+9+6+6+170.5 = 344.5 tonnes full and 4+4+4+4+1+1+6+6+170.5 = 200.5 tonnes empty, for a TWR of 1.63 and 1,593.95 m/s of delta-V. Total delta-V would be 6,701.95 m/s... From that math, I'm assuming that you're not running fuel lines from your outboard units to the core and that you're running both stages concurrently. You'd get FAR better performance from the booster if you ran the fuel lines; at this point the outboard units aren't contributing all that much to your overall delta-V. Okay then. So things are even trickier than I thought - I'll need to calculate about how far into the flight it is when the Mainsails run out of gas and are cut loose, and then figure out what the mass of the core unit is at that point. So let's see...Mainsails have a fuel flow rate in atmo of 0.4778 t/s. You've got two, so their fuel flow is .9576 t/s. You've got 144 tonnes of fuel in the core, so you'll be empty after 150.376 seconds (two and a half minutes into the flight, sound right?) A KR-2L has a fuel flow rate of 0.7037 t/s in atmosphere - so after 150.376 seconds it has burned through 105.8195 tonnes of fuel. Thus at that point in the launch the core has a mass of 64.6805 tonnes. All this assumes that there is NO payload on the craft whatsoever. I'm out of time to type at the moment - I'll try to pick this up later; maybe one of y'all can check my math in the meantime and/or pick up the discussion.

I also doubted it was a single-stage lifter given the earlier parameters - but it's not impossible to build something like that. Just unlikely. In any event, with the new data I know it's a multi-stage rocket and we can work with that; I'll do the calculations here in a little bit. No, Tsiolkovsky came up with the equation; Goddard invented the first working liquid fuel rocket.

Thanks, I'll check it out. Stock or FAR?

If you're not interested in calculating a potential payload mass, you could install KER or Mechjeb for a delta-V and TWR readout in the VAB, and then you need to look for a mod called NRAP. NRAP would let you put a "proofing payload" on your design that can a) be adjusted for size and more importantly can be adjusted for mass. You simply stick that on the top of your booster and then increase the mass in whatever increments you want until either the TWR goes below 1.2 (generally considered the lowest "safe" TWR for a successful launch) or the delta-V goes below 4500; whatever the mass of the NRAP payload is at that time is what your booster can handle. Alternatively, you could just load some fuel tanks on top of the booster and go with that measure. That's a more "stock" way of figuring it out. EDIT: To answer your question mathematically, I'd need to know more about the characteristics of the booster itself - big one there is how many stages it has and the TWR of each stage, but the types of fuel tanks happen to be important in this case (the really big tanks have a wet-to-dry ratio of 8.2, while the FL-T100 through the Jumbo 64 have a wet-to-dry ratio of 9). I suppose I could guess at your booster configuration by what information you've given us. Lessee...347.6 tonnes with 1.6 TWR, and 5182 atmospheric. You've got 5450 kN of thrust (simply based on the general T = Ft/mg TWR equation, where T is the TWR and FFt is the thrust force of the engines, thus Ft = Tmg = 1.6 * 9.8 * 347.6 = 5450.368). Assuming a single stage at that thrust level and solving the same equation for mass (m = Ft/Tg) , you hit a 1.2 TWR at 463.47 tonnes. So your payload limit based on TWR would be 115.87 tonnes (463.47 - 347.6 = 115.87). I very much doubt that TWR is your limiting factor. Now, there's no single engine that produces that much thrust on its own. I'ma guessing you've got a cluster of engines - and I'd need to know which specific ones so I could tell what your Isp is; that's a bit of data I'd need to tell you the delta-V limit. So I guess I'd need to know both the fuel tank and engine configuration. But what I would do is work Tsiolkovsky backwards, setting the delta-V to 4500 (of course if it's a multi-stage rocket, it'll be a might hairier, but not as bad as you might think).

Haven't been checking 25k/Mach 4 - usually I check 0k/M0.35, 5k/M0.85, 10k/M1, 15k/M2, 20k/M3, 30k/M4. I general I haven't been getting red numbers until 30k/4, and those have been in the Nß parameter (i.e. "needs moar tail"). Occasionally I'll get Mw and Xu instabilities at that level too. Level AoA at that level is up around 20 degrees as a rule. The Xu baffles me - "X-force changes with forward speed"; does that mean I need to throttle back or something? Usually I do whatever I need to do to fix the pitch-up tendency and the Xu goes away in the process. That usually involves me having forgotten to not put my tailplane level with the wings instead of moving them up towards the top of the fuselage and giving them dihedral; it goes away when I do that. Seems I still need to un-learn some of my old stock aero habits... Didn't get a chance to play again last night - same reasons (the upstairs of my apartment, where my KSP box is located, has a temperature currently being measured in Scoville units/percentage of Hells). Spent the day looking at RL supersonic designs and Wanderfound's designs. I do have a question there - I noticed a fair number of the "engine unit" designs included two FL-T800 tanks but a few utilized one, and a few utilized three. What kind of criteria do y'all use when determining how much fuel to load? I think I might have asked this question before (and probably didn't understand the answer). I did note that the SR-71, X-15 and Concorde all had dry weights that were about 45% of their normal takeoff weight; is that a good metric to shoot for in KSP?

Well, a lot of this issue is going to be dependent upon which aerodynamic model you're using. Short answer is that "level flight" is a foreign concept in KSP no matter how you choose to fly. As far as fuel drain changing the center of mass goes, though, there is something you can do about it - there's this wonderful little mod called RCS Build Aid, which I'd recommend to anyone wanting to get serious about planes regardless of aero model. Among its many useful features is an indicator for the "dry center of mass", i.e. where the CoM will be when all the fuel tanks are empty. It's a good indicator of which way the mass will tend to shift as you fly, and you can use it to where you can balance your fuel load so that it won't shift around in flight when you're designing your planes. EDIT: Mostly ninja'd.

I do have RCS Build Aid - that's that torque parameter in Engine mode I should be looking at then, right? Okay - I can do that. Didn't have a chance to play last night on account of busted air conditioner and crummy weather, so nothing new to ask y'all today.

Do you think that's why the plane is behaving the way it is once I'm up in space?

Let me ask this question real quick - I've been largely considering the aspect ratio of the wings as a function of span-over-chord (you know, if it's a 2:1 ratio, then the span length is twice the chord length). I haven't been giving much thought to going the other direction of chord-over-span (i.e. a 2:1 ratio having the chord twice the length of the span). Would there be any point in me trying a design like that?

I can report a successful flight to orbit last night in the Screech Owl: Turns out having enough fuel makes a difference. So does making sure the action group that closes your air intakes includes the ones on the Radial Engine Bodies, and then making sure you actually hit that group once your RAPIERs switch to closed-cycle. Did forget about doing my adjustments before taking off, and this flight had no payload. Good question there - how much payload do you think this plane would be able to handle given its end conditions? 34 tonnes / 0.96 TWR at takeoff. The numbers would say 11 tonnes for a 25% payload fraction; my TWR at takeoff in that scenario would be 0.73, which would be low but acceptable - my principal concern then would be whether or not I'd have sufficient fuel to make orbit. This one exhibited the same behavior as the other plane I was flying over the weekend - once it was in space, I couldn't get it to fly straight. I verified the CoT and CoM were aligned in the SPH...so I'm wondering why it's doing that. I imagine the only reason why I got it into orbit was the fact that I had set the Ap a bit higher than 75k this time and had time to make corrections. An ugly orbit but an orbit nonetheless. So...landing. Yesterday I began with my usual starting point halfway across the planet and Trajectories helped me put the red cross right over my KSC ground markers. The deorbit went relatively okay up to about 20,000. That was when I was watching my Q, my rate of descent and the data from NavUtilities - I was attempting to keep my rate of descent around 150 m/s and had to pull up my nose. At 10k, still going Mach 2, I pulled up a little hard and went into a spin. Recovered from the spin at Mach 0.5 and 4000 meters, so that part worked out - but that's definitely not the way I want to lose speed and reduce Q, I imagine. I should mentioned I was crabbed out (if that's the proper term) at the time - spoilers deployed, flaps fully extended. Probably should've retracted the spoilers when I entered the spin... Anyways, I got into the pattern, relatively lined up on the Runway, slowed my rate of descent to 5 m/s, then fouled the approach and crashed. I think it was because I wasn't level at touchdown; that sort of thing used to screw me up with stock aero on occasion. It's been a few weeks since I've done a landing of any kind - and my first attempt at one in FAR. I did quick-save the game so I can try again; any pointers on things I should do differently this time (like, not put myself in a spin to lose speed)?

Had my second ever successful FAR spaceplane flight to orbit. The attempted landing...didn't go quite as well. Let's say I made the Runway at least. Tonight I plan to work on the "intact" qualifier a bit more rigorously.

Span or chord, and why?

Good morning, y'all. Quick update on my weekend's shenanigans. Actually, I had a pretty good weekend all told - had three designs that made space (but not orbit). Let's start with the plane I designed in my last post: If y'all will recall, this was the one that I couldn't get going even though FAR green-lighted it because it got hit with a symmetry bug - it attached the wings in radial symmetry instead of mirror and refused to switch back. After this debacle I decided to bit the bullet and download B9 Procedural Wings. I must say I like it a lot better than the other Procedural Wings mod; I still have both installed at the moment due to the fact that the earlier designs incorporate the other mod, but I may be doing some redesign work in the future. Good airliner design, perhaps. Not so great a design for a spaceplane... Anyways, I decided to give this adjustment to the design a try: I didn't think for one second I was going to get anywhere with those chicken wings, and yes the design had roll issues. But believe it or not, this one made space (inverted...) - and it would've had the delta-V to circularize and make orbit, except that I found myself lacking the ability to control the plane once it was in space. Its behavior in space with the rockets lit was consistent with a misalignment of the CoM and CoT, and yet I know the two were aligned. Ordinarily I'd have fixed that issue by adding a SAS module - so I did that with the final design of the weekend, the Screech Owl 7: I literally designed and test flew the Screech right before I went to bed last night, so I haven't had time to make adjustments yet; I've already given strong thought to replacing the tail cone with a drag chute and am thinking about what I might want to tweak up at the nose. With this one, I went back to the RC glider ratios and I added a Large ASAS Module. FAR also green-lit this one at the crucial 30k/Mach 4 mark - in fact, it only gave a single red-light for the standard benchmarks for the entire flight profile, and that was to the Mδe parameter at 0k/Mach 0.35 (one I don't know how to test in the simulators). This one ran out of oxidizer before making orbit - the only fuel tanks in use ~as~ fuel tanks on this plane are in the outboard nacelle assemblies, and I'd drained the oxidizer from the forward bicouplers... Fuel again - for FAR the general advice I've received is "1 liquid tank and 1 rocket tank per engine". My reply: what size of rocket tank? I wasn't necessary happy with the mass balance of this plane either - the CoM was forward of the center of the cargo bay and shifted aft in flight by about half a meter according to RCS Build Aid. That's not enough to destabilize the plane, but I imagine I might've had some issues had there actually been payload in the bay. I imagine I just need to adjust the positioning of the nacelles on that one. Maybe add a little bit of fuel to the forward fuselage for additional ballast or something. Anyways, the flight of the Screech Owl ended in a fiery crash, and that's something I'd like to talk about: the process of de-orbit. I obviously screwed something up there - the plane's dynamic pressure exceeded 40 kPa; FAR gave me the Q warning and seconds later I was treated to the sight of the wings and canards ripping themselves off like something out of a 1920s Bugs Bunny cartoon. How do I avoid that? I'm assuming what happened was that I was going too fast as the atmosphere thickened up; I've heard that the shuttle performed "S-turns" to bleed off speed during the approach and I'm assuming that I should've been doing the same (rather than just letting the increase in density slow me down; rather a stock aero approach come to think of it) - how do you execute that maneuver properly?

I know; I've used 25% as a very conservative figure since my stock days (because even a lousy spaceplane in stock should be able to do at least 25%). Of course, I've yet to hit that figure in FAR - it's the fuel doing me in. I haven't had a design make it past 1400 in airbreathing mode - it's the wing drag doing it to me, of that I'm sure. Alright - give me some time and I'll get a pic or two of this plane up there. Neither the ability to dock nor the gathering of sci data was in that particular craft's intended mission profile - but I'll keep that in mind for future designs. I understand that, but are there any general guidelines? I consider myself lucky to have come across those RC guidelines; surely there are similar ones for supersonic planes somewhere... I can guess a few. The SR-71 and X-15 had wingspans that were 45-50% the length of the fuselage, with an aspect ratio somewhere between 1.75-2; if I'm doing the math right, cutting "the span of the wing by one-third" on my Horned Owl Design would've put the aspect ratio at 1.97, within that range. I might give that a try tomorrow. You also mentioned the Horned Owl (that last one for which I put up pictures) was light on engines - its takeoff TWR was 0.75 - would you recommend a higher TWR, and if so, what? Finally do you have any unmanned plane designs I can look at? Sorry if any of this sounds smart-assed or if I sound ungrateful in any way; I really am trying to figure out how I can make my designs better than they currently are.

I have a performance evaluation in six minutes, so I ain't got time to type. Try here if you're using stock aerodynamics or here as well if you're using FAR, and that's assuming you're wanting to build a spaceplane - SSTO just means "single-stage to orbit", meaning no parts come off of the craft, it can be applied to both rockets and spaceplanes but most commonly on the forums refers to spaceplanes. EDIT: For an SSTO rocket, assume a 4% payload fraction and 1.2 TWR at launch, and be willing to throttle back so that you stay at the top of the green zone of the gee meter after you make your turn. That's with stock aero; to be honest, I've yet to try an SSTO rocket launch in FAR, but I imagine the procedure'd be the same (1.2 is what I've heard is recommended for general all-stages rocketry in FAR, so I imagine you could pull off a better payload fraction there...). Seriously, those links I've posted above will help out a lot - keptin's guide is an essential for newcomers to the world of spaceplanes, while DocMoriarty's guide is good for the specifics in stock aero. The second link is a chronicle of my personal adventures in FAR; it would be useful to you if that's the aerodynamic model you're using, or are thinking about using.

So, last night I decided to build another FAR plane. My original intent with this one was a general purpose parts tester - something that could fit an object the size of a Mainsail engine in the cargo bay - but I decided I should go ahead and try to design it to where it could be used as a large cargo orbital transporter in a pinch. FAR gave me red lights for beta and r on the runway at Mach 0.35 and at 10k/Mach 1, but in both cases the simulations showed decreasing oscillations; it greenlit the plane at 15k/Mach2, 20k/Mach3 and - for the first time - 30k/Mach4. Sounded like I had a winner on my hands - so I launched the thing. Discovered after it rolled over and crashed that the SPH had kicked me over to radial symmetry on the main wing (I think it had to do with how I'd set up the outboard engines) and it wouldn't let me reattach the stupid wings in mirror symmetry. To say I was annoyed at this turn of events is an understatement, one I'm only using due to the rules of the KSP forums regarding the use of profanity. Anyways - can I walk y'all through the design process I used for this craft? I'm still looking for help on this score - what I'm doing is largely based on the advice I've received on this thread up to this point. This will be math heavy. Okay - so as always, I start with my payload. I want to haul a Mainsail engine to orbit - so I've got six tonnes of payload. 25% design payload fraction means I want to build a plane that has a mass of around 24 tonnes. I'll need a Mk3 Cargo Bay to contain the Mainsail due to its size, but I should be able to use the shorter bay. I want a 0.75 TWR on the Runway (per eddiew), and I know RAPIER engines output 80 kN of thrust each on the Runway (from observation), so I know that each RAPIER will conservatively support about 10.75 tonnes of airplane: TWR = T /(mg), (mTWR) = T / g, m = T / (gTWR) = 80 / (9.8 *0.75) = 10.88 (which is not a nice figure to work with, hence I round it down). Since I want a 24 tonne aircraft, I'll need three RAPIER engines. And since I've got three RAPIERs, I know my plane oughta be able to support up to 32.25 tonnes (10.75*3 = 32.25), so I'll actually design it for that mass instead. Knowing that, I can calculate my fuel needs: 40 units per tonne of both oxidizer and liquid fuel, assuming a kickover to rocket mode above 30k going about 1400 m/s. That comes out to 1,290 units of both LF and LOX. If I want to use the plane for its original intended purpose, I'll just drain the LOX before loading up the payload. So I begin building my fuselage, starting with a large RGU followed aft with a Z-4k battery. To the nose I add a Protective Nose Cone. I then add a 2.5m-Mk3 adapter, put in the Mk3 Cargo Bay, put another 2.5-Mk3 adapter (going back down to 2.5), then a short 2.5-1 meter adapter. I decide to put a single RAPIER in the centerline tail and put the other two outboard, each with a Radial Engine Body. To the front of the outboard units I attach a short 1m-Mark 2 adapter, and on each of those I added a Mk2 Bicoupler, with a pair of Shock Cone Intakes on the ends of those. I've got more fuel in the craft at that point than I need, so I decide to drain the 2.5-1 meter adapter as well as the outboard components, and balance the remaining fuel between the two 2.5-Mk3 adapters, running fuel lines inside the cargo bay between the two tanks. I also run fuel lines from the aft tank to the outboard units. Checking the mass distribution, I see that I'm a little heavy aft, so I add a large RCS tank for ballast immediately aft of the battery. RCS Build aid tells me that my CoM will remain reasonably stable, so I run with this setup. I set up tricycle gears - one gear up by the nose, two on the outboard units. I'm using my customized Large Gear Bays for this since I've got a big plane. Now I begin calculating what I need as far as wing surfaces are concerned - for these, I'm using those formulas I came across the other day. First, my final fuselage dimensions are 21.8 meters in length, 6.3 meters in width and 3.8 meters in draught. Fuselage should be 70-75% of the total wingspan; I go with 70%, so I know I want the wingspan to be 31.14 m (21.8/0.7 = 31.14). Chop that in half for a single wing - 15.57 meters - and then subtract half the fuselage length from that: 12.42 meters is the desired span of the wing. As far as the wing chords goes, I want it to be 1/6 the total wingspan, so 31.14/6 = 5.19 meters. I should have a total wing area of 5.19 * 12.42 * 2 = 128.92 square meters. I'll generally shoot for a 45 degree sweep of the wings if I can manage it. Horizontal stabilizers are 25% of the total wing area - 32.23 square meters, and the vertical stabilizer should be 10% of the total wing area - 12.89 square meters. I'm assuming I want the fin to have a 4:1 aspect ratio - so 4x * x = 12.89, 4x^2 = 12.89, x^2 = 12.89/4, x = sqrt(12.89/4) = 1.795 meters, the chord of the tail. The span will therefore be 7.18 meters. Again I'll shoot for 45 degrees sweep. For the horizontal surfaces, I'll have two canards at 2:1 and two stabilators at 4:1, so that's 2x^2 + 2x^2 + 4x^2 + 4x^2 = 32.23, 12x^2 = 32.23, x^2 = 32.23/12, x = sqrt(32.23/12) = 1.64 meters. So my canards will have a span of 3.28 meters each and the stabilators will have spans of 6.56 meters. With the dimensions calculated, I whip out Procedural Wings (going to install B9 Procedural Wings today to see if I get better results) and build the various surfaces to the tolerances I've calculated, and then start attaching them. Fin first, then canards, then stabilators, wings last. After that I adjust their positions so that the CoL is not too far aft. Each wing surface is set to .7 strength and 100% of the axis to which it's designed to control. When I think I've got a plane that might fly, I head to FAR and check its stability with the usual benchmarks: 0k/Mach0.35, 5k/Mach0.85, 10k/Mach 1, 15k/Mach 2, 20k/Mach 3, 30k /Mach 4. If I get a red number, I check the simulation for the subscript indicated with an initial value of 5 and see what the graphs do - I know I'll have problems if the graphs diverge or it shows an increasing oscillation, and that the problem is tolerable if it shows a steady or decreasing oscillation. After all that, I hit the Intake Build Aid magic button, make sure the front gear is set up properly, and go test it out. Alright - flaws in this process: I want to hear about it if there's something I'm doing wrong (besides, perhaps, any accusations of over-analyzing things).

Spent some time working on a third FAR craft. Got hit by the symmetry bug - it put my main wings in radial symmetry and refused to switch it to mirror symmetry, so the thing had no roll control. I was quite annoyed...

This definitely sounds like an interesting challenge...I wonder if it'd be possible to construct something approaching a Difference Engine, or perhaps an Analytical Engine. Programming it would be the tricky bit - I don't know what would be a good Kerbal equivalent for punch cards...

Big question of whether or not to make the switch is simple: how much do you rely on mathematics in your launches? If you utilize the math and want a plane-like craft to behave like a plane-like craft, you might like FAR. If you're more of a "throw it together and see if it works" type, or if you prefer supersonic tri-planes, avoid FAR like the plague. Myself, I made the switch because A) I had pretty much nailed down how to fly planes in stock and because I knew changes to stock aero were coming and I wanted to get to a state where, to the best of my knowledge, I could design and fly craft that would work in the new state of things. Pecan gave you the link to the thread I started up last month that's detailing my adventures with FAR. Have I figured everything out yet? No. Obviously. But I am learning, and I haven't yet resorted to throwing bricks, so there is that. My big annoyance with FAR is that I am very much a figures and guidelines type of builder, and FAR has few solid guidelines. Or at least, it has guidelines that are more ambiguous than stock. For example, in stock, you fly with 1:1 mass to total lift coefficient ratio. In FAR, that much wing will give you too much drag in the critical region between 25-30k. What's the proper substitution there? Hell if I know...I haven't found a working solution with stock parts yet, let's put it that way.