Mr-Punk

My Feedback: (2)

So I've been wanting a really hot plane for a while. The Flying Machine by Don Muddiman seemed about right. 100+ mph snap rolls and 4 pounds with hot 46 on a pipe. To get a Flying Machine one has to scratch build it from plans. It's all sheet construction and that means a lot of parts to cut out. Well I've been wanted to keep my CAD skills up so I decided what the heck I'll design my own. I'm making the fuse stick and sheet construction and standard D-Tube wing. The tail will be combination of stick and sheet with maybe spruce trailing edges. I'm keeping it beefy to withstand that kind of flying. I'm keeping it around the same dimensions. 44" WS, 440 sq in wing area around 40" lg 3 1/2-4 lbs. Semi-symetrical airfoil. Mine looks a little less racy and more sporty than Don's. The airfoil looks thicker and I made the tail moment a little longer. I've got a AX 46 that needs rebuilt and a Macs tuned pipe and header for it. Gonna use some old 4-Star landing gear, and a lot of scrap and leftovers. I'm still working on name. Probably something Spanishy. I'm open to suggestions.

It's feels kinda weird. I hope I'm not turning Chinese. This isn't a copy no more than an Ace Bingo or GP Super Sportster is a 4 Star 40. It's a plane inspired by the Flying Machine and I hope to fly it similar to the way Don fly's his.

Peace,
J

BMatthews

For a 100'ish mph model I'd consider slimming the design down by quite a lot. The wing section is pretty thick and the fuselage far more bulky than desireable.

Think more along the lines of the old pre turnaround style pattern models but scaled down to around 80% of the size of the .60 powered versions. In fact for what you're after such a model would be darn near perfect.

Or look at the idea of a Quickie 400 pylon racer with slightly wider controls. Again this would produce a slim and slippery model that is quite a lot smaller and slimmer than your design.

To add to the overall speed and the zoomieness in the dives and low fast passes you'll even want to look at going with retractable gear or at least the slim style racing wheels.

Mr-Punk

My Feedback: (2)

I may slim it down a bit. But remember this is being modeled after the Flying Machine. Mine will probably be more on the hot sport plane side. I want it to be capable of knife edge loops which is one reason the fuse is a little bulky. The Flying Machine seems plenty fast for me. It's basically a 25 sized plane with a hot piped 46 on it. I may shorten it a bit. It has less wing than a quickie. 44" WS 10" chord. Whether it's 100 mph or not is alright. I have a 60 Kaos with retracts and am going to try to keep this thing light and sturdy with fixed gear. Thanks for the input though. I will update when I make progress. Hopefully we will see it built and flown this year.

Peace,
J

BMatthews

As long as the top speed isn't a must have then I think you've got the basic idea wired solid. Certainly with your plan in mind it will be a very hot and strong performer!

A few steps taken to minimize the risk of control surface flutter would not be amiss. Tight hinge lines, solid pushrods with no slop, good tough medium hard C grain control surfaces and perhaps even build on mass balances right off the bat.

Wing mounted servos and control horns situated at odd % split locations would also aid in minimizing the flex and harmonics that can support the generation of the flutter. For example locate the control horns at 45% of the span out from the inner end instead of right at 50% where a harmonic could form with the control horn at the nodal point. I don't know if you've thought of these already or not but it can't hurt to mention them.

Mr-Punk

My Feedback: (2)

Thanks Bmathews for the input. I had not thought about harmonic vibrations. That makes sense and will take your advice. The elevator will be a pull for up pushrod. I hinge tight usually but may gap seal these. I have always kept wing mounted servos more toward the center of the wing but mainly to keep the wings lighter toward the tips a nod to my glider building days and figured it would roll and damp better with the mass more centered around the CG.

I have been thinking of making the fin and horizontal stab TE's out of spruce or maybe basswood. Wing spars of course spruce and at least the lower fuse longeron spruce as well. The wing will be built as one piece with some doublers around the center section. I've thought about carbon fiber tow or tape laminated on the spars. I did that once on a Gentle Lady and it would handle pretty stiff winch launches. I want this thing to handle full deflection maneuvers at wide open flight speeds like Muddiman's Flying Machine but without the full sheet construction. I know those are conflicting design attributes. I know stick structures can be built strong and would think this plane would look neat with part transparent covering performing like said.

Peace,
J

speedracerntrixie

My Feedback: (29)

Knife edge loops were mentioned so I assume that other aspects of aerobatics are important. I think that the tail design is going to induce quite a bit of control cross couple and it looks like the fuse side area behind the wing is a bit low for good knife edge performance.

BMatthews

I like your thinking on all that. Sounds like a great plan in all respects.

The basswood or spruce for the tail surfaces is a great idea in terms of stiffness. But the added weight suggests that using a mass balance setup would be even more advisable to keep the balance point for the surfaces as close to the hinge line as possible.

You have a good point about the servos being in close to avoid the mass moments. But like most things in like there's compromises and tradeoffs. I suspect that this is a good place for such a tradeoff to avoid longer lengths of strip aileron that tend to be more flutter prone. Perhaps split the difference and put the servos out where the output arms and control horns can be at something like 36% of the aileron span?

I've got a couple of ideas for mass balances I'll sketch up and post later for you to consider. Again I have no idea if they are needed or not but on a model of this sort it seems wise to put them in BEFORE you find out the hard way that they are needed.....

On a whim I checked You Tube for Muddiman's Flying Machine. I gotta say that after watching this that your idea for carbon caps and really, really good webbing is likely a VERY GOOD IDEA ! ! ! !

http://www.youtube.com/watch?v=25GK6s91pzI

I also hope that you'll post flying videos of your version once done. It looks like these things are a lot of fun.