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3600 rpm and is fitted with a 1:1.6 PSRU

Hi Nev, I have been in contact with a builder who recently replaced his HKS with the Valley Engineering Big Twin, and here's what he had to say: Interesting - anyone care to make a comment based on what he has reported? Cheers, Duncan

Hi, I have recently bought an aero-converted Generac 990cc industrial engine for my project. Repeated emails and phone calls to the manufacturer (Valley Engineering in the US) assured me that the much reworked engine now produces 50hp. I have designed my single seat plane around this powerplant. However, recent discussions with knowledgeable members of a homebuilt aircraft forum in the US suggest that the engine will NOT be capable of producing 50hp. I already have the engine here in Brisbane. What I would like to do now is to put the motor on a dyno and verify the power output. Does anyone know of a local company or person who could perform such a test? Thanks in advance, Duncan

Cool. 5 kts is a lot for just enclosing the tyres. And good luck with the studies. I'll no doubt ne in contact closer to the time Regards, and thanks, Duncan

Cheers mate. You've been a star. So - I'm going to be limited to 118kts? Bugger. Anyway - that's a lot faster on 50hp than most people would expect. Question: Do you actually MAKE the props, or just design them? Actually, I was considering exactly your suggestion re: fully enclosed wheels. But I gave up on the idea, because I figured it would make very little difference. But if there is an increase in top end - it might be worthwhile. Pity about retracts, though. I don't think there's any space for them. Besides, I wouldn't know how to build them... Regards, Duncan

Hi Mark, I'd be very happy to have you drop by the workshop when the plane is looking a bit more "respectable". There's a lot of mess at the moment, but I'm in the middle of adding the final touches to the plug so that i can make molds of it. That will happen in the next couple of weeks. After that, I'll be vacuum infusing actual parts - which ought to be great fun. You could arrive and give me some builder assistance for the day. I'd enjoy that. Yes, the model is available for download here on the X-Plane site. Here's the link... http://forums.x-plane.org/index.php?app=downloads&showfile=22694 Duncan

Hi Bob, No worries about taking your time. Family/life are priorities. I had estimated a top speed of 135kts, so this looks right on the money. I don't really have any drag curves to speak of, to be honest. Just a bag of wishes and an evolving airframe. Duncan

What, and spoil all the fun? Actually, one of the guys in the same complex as I am building has a business which makes industrial cases, boxes etc. He'd got a great big router, and is keen to give me a hand with my "crazy airplane". Cost will be very reasonable - materials and a bit of loose change for beers, I think. I'd LOVE to get the whole lot CNC done - but like most of us, it always comes down to money... Duncan

Great. I've just received my copy of CompuFoil software, so I'm going to be creating the files for the templates any day now. I also ordered the Feathercut hotwire system, after trying VALIANTLY to get manual hotwiring right. Every hesitation, sneeze or eye-blink puts a little groove in the surface. It's a LOT harder than it looks. But the gravity fed Feathercut looks to be the boss! Duncan

Hi guys, AL sheet might be just the thing. I wonder if my router friend will be able to cut them? Or should I find somewhere to laser cut them?I need about 14 of them. Ideas? Duncan

Good suggestions. Will phone around. Thanks guys. Duncan

Hi, I see what you mean. Looks a but bulky, but I can see how this would be effective. I'll have to start drawing to see what I can come up with... Duncan

Two sketches (from X-Plane) showing the horizontal and vertical separation of the wings. Datum: Spinner bulkhead Wing1 MAC (ft) 2.63 Wing1 CP from datum (ft) 2.86 Wing1 AR 6.82 Wing1 Area (ft^2) 42.56 Wing2 MAC (ft) 2.09 Wing2 CP from datum (ft) 9.09 Wing2 AR 7.53 Wing2 Area (ft^2) 30.05 Distance between the two Acs 6.23 Total wing area 72.61 Distance between W1 & W2 Acs 6.23 Side view: http://1drv.ms/1hh0taD Top view: http://1drv.ms/1hh0DP9

Correct. wheel fairings, very clean fuse. However, the rear wing is a lifting surface, not a stab. It is set to one degree lower incidence than the front, and (of course) sits in the front wing downwash. X-Plane predicts a six degree difference in AoA which agrees very well with NACA papers I've read on downwash angles. At takeoff, the rear wing produces about 120lbs of lift. During cruise, this decreases to about 25lbs @120kts, and about 10lbs of lift at 135kts (WOT). This is due both to downwash from the front wing, and increased pitching moment as speed increases. With this configuration (ie large wing in front, smaller wing in rear) I end up (essentially) with a mono-wing at cruise speeds with the rear wing acting as a h-stab and adding about 10lbs of drag but no negative lift. At TO and stall, however, lifting duties are fairly shared. Best of both worlds? This shift in relative lift is partly responsible for the large performance envelope. Duncan

Hi, That 20kt dip is a bit weird isn't it? To someone like me, that just doesn't make sense... Yes, the higher end of things is probably where I'll be aiming to optimise. The plane is very small and very light, so I'm not overly concerned with optimising for the climb. I reckon it'll get there soon enough. Do you tjhink we'll be able to get away with a fixed pitch prop? Duncan

Cheers mate - I'll give them a call

Hi Bob, Again, this is terribly kind of you. Thank you. MAUW: 576lbs Wing area (front wing): 63.08ft^2 AR: 7.02 Tail area: 34.05ft^2 AR: 8.53 Fuse surface area: 68ft^2 (more or less) Wheel size (front): 9.6" diameter, 4.3" wide, Mains: 13" diameter, 5" wide Sorry to be working in Imperial units, but my design software is all in feet and inches. Duncan

Hi again, I'm also looking for suitable material out of which to make hotwire templates. I've tried MDF, but the wire burns right into it. Same with plywood. I read on the web that guys use formica or phenolic impregnated paper. Neither of which I seem able to find a local (to Brisbane) source for. What do you guys use? And where can I get some? Cheers, Duncan

Hi, I am going to try my hand at hot wiring some airfoils. I have the hotwire all set up, so now I'm looking for a local (to Brisbane) source for suitable foam. The plan is to lean the art by sacrificing some cheap white foam, and when I think I know what I'm doing, move up to more suitable foams. Eventually, I want to make female plugs (one for the tip skin, and one for the bottom) so that I can make molds from them. My wing skins themselves will be a sandwiched 3mm 3D-Core hexagonally perforated EPS foam sheeting, with 2x glass on either side. So I'm not looking to spend a fortune on structural foam or even DOW blue foam. This plan may change, but that's what I'm currently considering. Any thoughts/suggestions? Regards, Duncan

Hi, Gosh, I turn my back at return to see you hard at it. Good on you... I have to just sit back and gaze in wonder at all this. Fascinating, but completely beyond me. You mentioned spinner size once or twice. I favour a large spinner (currently looking at 14.5") but this is not set in stone. It just looks nice. Some design targets: Stall 43kts Cruise 135kts My engine produces 50hp @ 3600rpm, and is fitted with a 1.6:1 PSRU. I trust these specs line up OK with your prop tinkering? Regards, Duncan

Hi, Props are really a bit of an art, aren't they? They don't seem to make sense... Duncan

Hi, Very kind of you to offer to help. The engine red lines at 3600 rpm, and is fitted with a 1.6 to 1 PSRU. Engine is rated at 50hp max. Does this help? Duncan

Hi I estimate the MAUW will be in the region of 560lbs (256kg). Valley Engineering supplied a prop with the engine, but to be honest, I don’t know what its specs are, besides being two-bladed, 5ft diam, wooden. In X-Plane, I’m using a 2.5ft radius 2 blade with the following specs: http://1drv.ms/1i7Ofg6 I’m not much of a prop person, and I was planning on getting someone who knows what he’s talking about to select a prop for me (or confirm the V.E. supplied prop is OK) closer to the time. If you use X-Plane, you might want to grab a copy of the model and fly it. Feedback invited, of course. You can find the model here: http://1drv.ms/1h2LaSI

Gentlemen, I have been working at this design for a few years now, progressing from rough sketches of improbable concepts, to what I now have - via Raymer, Roncz, Whitney and others. And lots of help from experienced friends and designers. Lately, I have discovered X-Plane as a great visual concept tool, and have been using it as a sanity check on my design formulae. Interestingly, I've discovered that there are very few design concepts which satisfy both the spreadsheets/formulae and X-Plane. What I now have ticks all the design boxes I can find, AND flies brilliantly in X-Plane. I'm a happy camper. Proposed specs: Seating: Single seat Power: 50hp Valley Engineering twin (116lbs, including redrive, full oil, starter etc) Configuration: Tractor, tandem wing (larger wing in front), tricycle undercarriage Performance: Stall 43kts, Max S&L 135kts Controls: Elevators/ailerons on both wings, flaps on both wings Construction: Glassfibre/3-D Core foam sandwich Current status: I am putting the finishing touches to the plug (completing the wing recesses), and will hopefully be doing final prep for the molds within a week or so. Regards, Duncan

Hi, I used to live in CT for many years - long before I took up flying though. I know Table View very well. My folks used to live there. Who built your engine? Sounds like a beauty. Max HP? Max continuous? Regards, Duncan