Been playin' with a Payen

[maxmwill]

Recently, I have been asking a few(still more to ask, but for now, what answers I've gotten so far will suffice) questions, and have been learning a lot from the resulting back and forth between various members and myself.

So, I decided to play with the design to see if the tickle/hint I've been getting from my curiosity bump could possibly bear fruit.

About a week or so ago, I went to my favorite copy emporium(they know me very well, because I've done this previously with other model projects), and had the three view of the SP.190 blown up to better than twice its size. As the copy machine being used couldn't make complete copies(I asked for three, just in case the first copy was drafted upon too many times to be very readable), it was split into three pieces, each 11x17, because I had scaled it up to a prop from a small electric motor with a spinner that was a real close match(I tend to use the Mk1 mod0 flesh and blood eyeball for calibration, the resulting term being TLAR, or that looks about right, which is also a mechanic's term, yes, really), and so ended up with a 190 with a 6+ inch span, and a nearly 15 inch length.

But wait, there's more.

A couple years ago, while perusing Ebay in the RC models section, specifically electric motors, I found one that fascinated me, a contra prop motor. I jumped on that(fortunately at the time, I could afford this, as for such a small motor, it had a dear price). When I got this little unit, I realized just how they were able to have a functional contra prop. It was two motors, with aft motor shaft going through the front motor and driving the front prop.

At the time, I had a disc of seaplane patents from the beginning of aviation on through to the 1980s. One of the designs, a little cutie, dating from the 60s, was a small delta wing seaplane, tail less, with a fin mounted engine(looked like a possible turboprop) driving a contra prop the nacelle facing forward. And that in itself is a whole other story, so I won't go into much detail, except to say that this was part of the inspiration for me to get this little jewel.

Anyway, I took the enlarged drawings, and, using the spinner on the contra prop as a base, began to shoot some numbers. With a mux(multiplier) of 2.35, this further scaled up 190 spanned some 15 inches, with a total length of just short of 35 inches.

This I did out of rank curiosity, and now, as I think on it, perhaps a slightly modified SP.190 might be something to attempt, if I could find someone willing to fly this, as my RC flying skills are so rusty that even three cans of Liquid Wrench might not be enough.

Among the alterations are, the afore mentioned contra prop motor, and a change in the airfoils which seemed to have been planned on, the wing having a really thin airfoil of some kind and a sharp leading edge. The same for the nose wing. What I'm thinking of using is something a tad thicker, say a 10% wing section, possibly the NACA 230 series, as I know that family quite well, and am comfortable with the characteristics. Plus, Charley Zimmerman, he having designed the Vought Pancakes, used that wing section as well. The nose wing I'd simply go with a symmetrical wing section, and keep it at 10%, plus the nose wing will have a positive angle of attack, about 3 degrees or so, because I learned a long time ago that a canard aircraft needs that in order for the nose wing to stall before the main wing does, and when it stalls, the nose drops, keeping the wing stable and controllable. I found out about that the hard way 30 years ago with an RC canard. Got points for the way it crashed, but it was a learning experience.

As to the landing gear, I had kicked the idea around of having trike gear, but I think I'll stick with the tail dragger.

This isn't the first time I'm doing this in recent memory, however. A few months ago, I started drawing the plans for a kinda scale Sanka MkB from the anime Skycrawlers, and that is also being attended to, but the Payen I'm thinking of is another to help keep things flowing if I get slightly discouraged with one, I'll put that up and attack the other until the pendulum swings back

O, and the fin(if you could call it that), I'm not sure if I'll go with an actual fin, or stay with the bobtail.

[maxmwill]

Well, if I can scrape the postage or freight cost, I wouldn't mind sending it your way, unless you're in Australia or New Zealand, because they have some interesting regulations regarding things crafted of wood, such as they have to be kept in quarantine for 3 months(I think).

But right now, I'm just shooting numbers and have yet to put pencil to paper(yeah, I'm that oldfashioned), other than what I've been writing down for the calculator.

And I still have to learn about these new fangled electric motors, the coreless ones, because when I was flying RC, an electric motor had a normal rotor and stator, and there was no way to vary the motor speed, and the motors themselves were the size of a Contadina tomato paste can(a couple inches across and 3 inches long, and took a mess of NiCads to work, and those drained fast.

This little thing is .91" across, and 2.75" long, from back of the aft motor to the tip of the spinner, and for power wires, it has what looks like 22 gauge bell wire, three from each, with no color coding for polarity.

[maxmwill]

Ok. Thanks.

I am not entirely unfamiliar with the concept of coreless motors, as 3 years ago, I started considering getting back into RC modelling, eventually, and so started looking in Ebay for what I could afford and have a running start. I found a .90 size 4 cycle engine for less than 50 bucks, and which looked pretty good from the pic. I got it, an it was an OS 90, and did indeed look pretty good, except for a chip in the cylinder where the exhaust came out. There were still a few threads for the exhaust pipe to be securely torqued into the cylinder, and it has good compression, so it was put away until I could not only come up with something appropriate to put it on, but also after I get enough experience flying RC once more.

But, I didn't stop there. I got curious about electric motors, and so started looking at those. Found one that was listed an equivalent to a .25 regular engine, and the price was right(less than 15 bucks), so ordered it. When it arrived, I opened the box and treated like any other electric motor I was familiar with and held the rest of it in one hand and tried to spin the motor. This was my first experience with a coreless motor, because holding on to the body of it, and trying to spin the shaft, it wouldn't budge. So I sent a message to the seller that it wouldn't spin, and he replied that he could send me another one or refund my money, and I could discard the motor I got. I told him that the refund would be fine. Shortly after that, I realized what "coreless" meant, and that what I had was perfectly fine(never realized before that everything spins with the prop, just the lugs in the center are what anchors it to the mount. So I got my money back and had a motor that cost the amount of that refund.

Since then, I've gotten a couple more when I ordered a pair of 70 mm ducted fans for a better price than what I was used to(prior to this, the only ducted fan I was familiar with was the .049 fan that went into the Top Flite A4 model, that you had to start it by holding it separate from the model, and after it started, you had to very carefully put that screaming hungry demon back into the A4 model, and then very carefully secure it with rubber bands. A friend of mine had one, and one day he was at the flying field, started it, and as he was installing it back in, his pinky finger got too close to the spinning rotor(at some ten thousand screaming rpm), and it took his finger to the first joint really fast and really clean, so I decided right then and there that I'd wait until ducted fans could be started in the model, which is the why of my ordering the pair of fans).

And now I have a possible use for one of the fan units, a kinda scale model of the M15, among the two others I've already mentioned.

I know that everyone thinks the M15 is so ugly that it could stop a computer, but I've seen flying machines which were far uglier by a long shot than the M15, such as the Amiot143, and just about any Bloch bomber from the same time period, and I've heard few people complain about those.

Well, if you wouldn't mind waiting for a little while, I'd be more than happy to ship it when the time comes.

[PR19_Kit]

.049s? I've still got a couple of those little things stashed away somewhere. One is a Thermal Hopper, apparently quite rare these days. Do Cox still make .049s?

[maxmwill]

Well, I've started drafting the plans out, and, as per my usual, I have started drawing out the fuselage, starting with figuring out the stations and the gap on the 1/72 three view, then increasing the size after.

And, since the wing root occupies so much of the fuselage, I'm also trying to find the appropriate airfoil coordinate table and go from there. The trouble with that is that I used to have a well thumbed copy of Theory of Wing sections, by CL Stong, and that had all the tables I'd ever need on pretty much every NACA airfoil generated by them from when they were formed in the late 20s or so, up until they were dissolved and NASA rose to take their place in the late 50s. And the tables there are not what seems to be available online now. Because I'd have the centerline laid out, with the stations .0125, .05, .075, .1, .15, .20, .25, .30 all the way to 100% of chord. Easy peasy way to plot it out, just lay out your grid, the coordinates being percentages of chord, for x and for y, and all you have to do is do this for each corresponding rib. Can be tedious, can be a pita, but at the end, all you end up with is after playing dot to dot.

And that sort of plotting doesn't seem to exist anymore, just software you load into the 'puter machine.

Guess I'll have to get another copy of Theory, if I can find one.

[maxmwill]

You can find plenty of .049s on Ebay, Baby Bees, Thimble Dromes, and others, some for less than 10 bucks, while others for around 50 or 60 bucks.