IAD

Yes, spring isn't known for it's flying weather. Also, I found out that I'm shamefully out of practice. (I crashed/crash-landed a couple ships that normally I can fling around the sky as I see fit. Only light damage, but still mortifying.) I'm going to have to do some brushing up on technique, before I take the SV out. ~Luke

No good weather so far... If it isn't raining, it's windy. (And that's when it isn't both.) Also, I'm just getting over a cold, and didn't really feel like trying a first flight with anything less than full mental capacity at my disposal. So, I applied the canopy frame instead... Not much, but it does look good. (Obviously, yet to be painted.) It is made up of strips of paper, carefully applied. This way, even when painted, there's a nice 'frame' look, instead of just having lines drawn on a flat surface. ~Luke

I tell you, that control rig has more pushrods-per-servo than anything else I have seen... Glad you like it, though (for your sake) I hope you never have to fix it! (Don't worry, it's durable.) Next, I have to get a spot of good weather for flight-testing. ~Luke

Ok, here's a couple photos... First, the control installation. It's really not as messy as it looks. (Promise!) It's a little hard to see what's going on, but the general idea is this: Right servo: Right elevator demixer feed and right thrust-vector vanes feed to outside side of the servo arm. Right elevons go to the inside side of the same servo arm. Left canards to the inside side of the servo as the right elevons. Left servo: Left elevator demixer feed and left thrust-vector vanes feed to outside side of the servo arm. Left elevons go to the inside side of the same servo arm. Right canards to the inside side of the servo as the right elevons. Also, just to prove that overall, the SV still looks just fine, I've attached an overall shot. It did take some 'hanger rash' in the process of swapping out the servos, but nothing really visible. ~Luke

Ok, the servos are installed. They're 0.1 oz. lighter (for the pair) and have twice the torque output. They definitely work better in this application, all the surfaces recenter faster, etc. Also, because the geometry of the servo arms is different, I don't have to reduce the throws via the dual rates on the transmitter, which in turn means better resolution in terms of servo position. (At least, that's what I remember reading 'out there' somewhere.) Also, it definitely means that the torque of the servos is being put to better use. ~Luke

Well, the servos came Thursday, and I hope to have them in place by today. Unfortunately, I'm running at decreased efficiency... Picked up some sort of sore-throat-bug thing, and not feeling so great. But, I'm determined. The weather has finally gone from ultra-windy to flyable..! ~Luke

I'll get some photos, maybe even a short video clip, showing the controls working, once I get the new servos in place. Almost all of the control systems are completely hidden. The only exception is on the elevators. Each one has a very low profile (custom) control horn about 0.2" tall, and about 0.25" of pushrod exposed, at the very base. All the other aerodynamic control surfaces use torque-rods, so everything's internal. The thrust-vector vanes have the interlinks up inside the 'glove' at the very end of the nacelle, so unless you're looking right up the exhaust ducting, you won't see anything. Even if you are looking, the 1/64" interlink pushrods don't really show up that badly. ~Luke

Thanks guys. It's encouraging to know that I've got moral support, as it were! Ok, I'm on the final leg. All the controls are hooked up, and I've got an order of lighter, higher-power servos 'in progress'. Twice as much torque, 0.03 oz., lighter per servo, plus better recentering, to boot. (The current servos I have are close to 'burning', due to all the different control systems they have to drive, plus they never quite come back to the same 'center' point.) Once those come and are installed, it's just a matter of waiting for the perfect day to test-fly! ~Luke

Yes, I was rather pleased. Right now, it's actually got some basic controls, but the wind is so strong, I've only been able to fly for a couple seconds at a time, between gusts. NoSuchFile: Whaddya mean, looks funny? It looks like an SV-51... Which... Well.. Ok, fine. SVs do look funny. Too many fins, and a Cyrano-de-Bergerac-esque nose. ~Luke

Decided to build a center-of-gravity test-bed. Better to smash up some sheet foam and a day's worth of work, rather than the real thing. http://www.rcgroups.com/forums/showthread....=31#post5200153 ~Luke

I haven't flown yet... Still working on the last few control system details, and waiting for some decent weather. The scale is.... Oh... 1:25th... (3' long.) ~Luke

Thanks! First flights next weekend, hopefully. (Nice avatar!) ~Luke

At this point, the only way to know if additional modifications will be necessary is to test-fly. (STRESS!!! ) ~Luke

Got a good deal of work done today... The canards are online, the elevators are installed and functional... Thrust-vector interconnects, and elevons are all that are left. (And weathering/panel-lining, which will be done after it flies.) ~Luke

No flights yet... I started hooking up the canards, and figuring out the best way to tie them into the control system... The battery mounting is in place, and tomorrow afternoon, I'll start up a weekend's worth of control system installations. Tricky business, getting everything to go in the right directions, off a mere two servos. (This is what I looked like, after designing the final linkage setup: ) ~Luke

Yes, I would love to see the Ivanov and Nora schemes in the air at the same time..! ~Luke

Well, as Sean has mentioned, here's what's on my workbench... ~Luke

In the end, the thrust-weight ratio is almost identical. (The new one is 1:2.13 T:W, the old one 1:2.28.) Some slight improvement. The thrust-vector losses weren't present in the older version, because they were mounted further out from the exhaust duct. This isn't an option on the new ship, because of space restrictions. However, because of the considerable loss of weight, (3 oz.) the wing-loading of the new version is much better, which should make it easier to fly, while at the same time requiring less power to remain in the air. If I decide to use a different battery pack I have my eye on (better voltage under load, less weight, but less capacity) my AUW would go down to 11.3 oz., for a 1:1.83 T:W ratio, with an even lower wing-loading. The further reduction in power requirements would help to offset the loss in capacity. Options, options. ~Luke P.S. Just to make this even more confusing, I understand that a better prediction of performance can be made based on power loading. (W/lb.) If this is true: Old ship: 100 W/lb. New ship: 125 W/lb.

Latest update, from RC-G: "Well! How does 6 oz. of thrust sound..? With thrust-vector vanes. (Fully charged battery. Just before the BEC kicks in, I get ~4.25 oz..) I did some more experiments, and found that there's a very specific spread position at which things work well with the TV vanes. Adding a discontinuity on the inner surface didn't really seem to do anything... I'll keep playing around with it, though... ...There are still some losses, I think I'd be looking at 7 oz., without the TV system, but... Win some, loose some. I may yet be able to improve the vanes further, but... 6 oz. should keep a 12.8 oz., 9.2 oz./ft^2 ship in the air... Hopefully. ~Luke"

http://www.rcgroups.com/forums/showpost.ph...8&postcount=422 Latest post on RC-G... Working out some of the more fiddly bits on the control system. ~Luke

Ohhhhh! Well, then. Yes. I can't say that it isn't a possibility 'something' interesting will happen. As long as I'm in control when my altitude is 0.0 ft, I'll be happy. ~Luke

I have been known to execute advanced maneuvers on the maiden, but on this airframe? I think I'm going to hold off until I'm sure of what it can do... A loop, a roll, perhaps... But no Z-IAS* moves. ~Luke *Zero Indicated Airspeed. I think that's a real acronym.

Yes, very. I've pretty much finished both sides now. I'm going to add the saw-tooth on the intake lip, and make sure that doesn't kill thrust, and then it's time to glue everything back together. Then it's controls, then battery mounting and paint touchup, and then... DIE, CF VF-0! ~Luke

Good news! I finished modifications on the left-side ducting, and.... I'm up to 3.125 oz. of thrust per fan! (That's quite a bit better than 2.25 per!) Note that it's also better than the fan running in free air without the intake lip, which suggests my ducting is at least somewhat effective. If I removed the intake box, I lost a good deal (~0.5 oz.) of thrust. Likewise, if I removed the 40mm-38mm cone on the exhaust, I lost ~0.2 oz... The fans seem very sensitive to ducting changes. Anyhow, now all I have to do is pull off the modifications on the other side, and this whole rotten 'thrustless' episode will be behind me. ~Luke

After some simple measurements, I found the problem, and formulated a way to correct it. First, the problem: The exhaust ducting diameter is about 2-3mm too small. This is, to say the least, bad. (The current cross-sectional area is only 85% of what it should be.) The fix: Using 150 grit sandpaper on a dowel, I'm going to enlarge the foam duct until it's over-sized by about 2 mm. I will then construct new ducts from transparency material, sized to have the correct taper (just like on the first SV) and insert these into the enlarged foam ducting. This will save me the nasty task of having to re-surface the assembled ducts, which are pretty inaccessible. ~Luke P.S. I tested the 'starved fan' theory, by carefully removing the intake boxes, and the thrust didn't improve at all. In fact, the thrust went down a bit, indicating that while the intakes may not be perfect, they are definitely beneficial. So, for the time being, I'm leaving them alone.