Mustang Fever

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Scott: Any idea what the wing area is? I couldn't find it on Tony's site. Anyway, it looks like it has a LOT, judging by that mammoth chord in the center. I'll bet you can safely exceed the max recommended weight and have no problems with all that power. With 2 15s and 2 10s, you have something in the neighborhood of 1.3 horsepower, or almost a thousand watts.. Tony has 4 - 180 watt motors called out in the description (720W total). Models fly OK at 50W per pound. You'll have almost 100 per pound, which is getting close to the "extreme aerobatic" category.

Even at 35 oz per square foot wing loading, stall speed (clean, sea level) is still only a bit above 25mph. The flaps should improve that considerably, but I doubt if your loading is going to get anywhere near that.

siddus74

Bob,

Your view on this is very positive . . . @ 8lb (the recommended AUW) the loading is said to be 29oz, maybe you can work out the wing area from that . . . do you think that a bit of glass and a covering in solartex will exceed 1lb? I dont qute understand your explaination please can you put an simpler the 25mph etc . . .

At this point I am glad I put the flaps on, do you think that they will make a difference?

Btw, saw your recent work on the Cat nacels . . . nice sheeting - takes an age doesnt it?, your going to enjoy that bird, I put an Iron across my wings today, good as new.

Scott.

Mustang Fever

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Scott:

I don't think some glass and solartex will exceed a pound, but have you figured in cowls and other trim items?

I did the math on this a couple times, but I don't trust it, as that wing looks much bigger than 633 square inches:

8 pounds is 128 ounces.
128 divided by 29 ounces per square foot works out to 4.4 square feet, or 4.4 x 144 = 633 square inches. At these figures, at 8.25 pounds you'll be at 30 oz/square foot, and you'd have to touch 9.6 pounds to be at 35 oz/square foot. Rather than trust their wing loading figure, what's the tip chord and the root chord? Is the taper more or less constant?

Stall speed is that speed (during level flight) at which the wing will quit flying and literally drop the airplane out of the air. It's kind of the "do not go below" speed. It varies according to wing loading and altitude, and to a lesser extent air temperature and barometric pressure on a given day. (The hotter it is and the lower the baro, the less efficient the wing is.) This graph of altitude and wing loading vs airspeed was put together for model planes, which stall at a much lower angle of attack than full size aircraft. I have found it to be quite accurate. If you save it and then increase the size, you can read it well.

The flaps will add extra drag on approach so that you can lower the nose and come in at a steeper angle, and also will provide extra lift such that you can go below the stall speed that you would have without them. How much is impossible to estimate. An aero engineer could do it, but I can't. The trick is not to get so slow that one or the other wing tips stalls before the section of the wing that has the flaps. That usually resiults in the airplane flipping over on it's back and augering in shortly afterward. It's something you want to experiment with when you have plenty of altitude in which to recover, so you can avoid it during approach to landing.

Fast Freddy

[8D]Hi Sid,

It's been awhile since I've checked this thread, but you're really coming along quite nicely. Man that's a lot of airplane and a lot of balsa dust! I know how the motivation thing goes and how one is tempted to put a current project on the backburner when the boredom factor sets in. That's why I have 4 projects in various stages of completion. My problem/enemy right now is no time. My pleasure is watching you guys build these awesome planes. For what it's worth, keep up the great work!!

siddus74

After a little break and together with my mate Simon we managed to do some more to my Sunderland . . . Thanks Simon.

Mustang Fever

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Scott:

She's really looking great[8D]

I haven't done a thing on the PBY, lately. Away from home for 3 weeks. Did get to maiden my 1/7 P-51, tho. Flies great. Much easier to handle than I expected.

I tried to fly my little electric Arrow off a pond near here, no go. Impossible to keep the left wing tip from digging in and flipping it. I'm real close to scrapping it, as it only seems able to fly off fresh, soft snow. Rather limited. [:@]

siddus74

Have made a start on glassing the lower part of the hull . . . started by giving the area to glassed a light rollered coat of the finishing epoxy with no cloth, leaving it for 24 hours and giving it a light sand. This stops the pin hole air bubbles and ensure the cloth goes on really nice - not worth skipping this stage.

Layed the cloth on the section to be glassed and with small dabs of cyano tacked the cloth taught, trim around the excess cloth with sharp scissors leaving 15mm over then just mix and roll . . .

siddus74

All the glassing is complete now, tail sections are covered so the fus/hull is ready for paint . . . Engine nacels are painted as are the tip floats - Tip floats are a little rough close up (glass on foam is a little crude, but they look ok from a short distance and more importantly are servicable and lightweight)

alasdair

Scott,
You are getting on well, but you'll need to get stuck in to finish it for Colwick in May!!!
Or will it be the july event?
I'll try to make it to one of them.
Alasdair

siddus74

Alasdair, I feel that it will be the July event . . . need to give this project as much chance to succeed as possible, you know how it goes . . .
a gallon of fuel through each engine 2 gyros etc etc

Be great if you can make it down to see it fly, then maybe you can bring your turbine water plane?

Scott.

Mustang Fever

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Scott-

That is beautiful. Keep plugging.

alasdair

Oh, if I come I'll bring the turbine, if they'll let me fly it. And I'm keen to see your Sunderland fly.
What about the Lake District? Ullswater in June?

How much do you think your Sunderland will weigh?
Alasdair

siddus74

Ill see what I can do with regards the other meets . . . do we have specific dates?

With regards the weight the brushless equivalent (no flaps) was supposed to be 8lb, I think I can get mine in with IC and and flaps at just under that . . . but it is only 72" and the wings are tapered too, so fingers crossed . . .

Scott.

alasdair

Scott,
Ullswater is June 20/21
Alasdair

Mustang Fever

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Scott:

Have you seen the video of Tony flying the B-50?

siddus74

Bob, Yep saw the video . . . nice I guess, not really my bag tbh . . .

Started the nasty jobof covering the wings. [:'(]

siddus74

After doing one half of the bottom the rest was quite easy and the wing was finished as far as the covering goes in under 2 hours . . .

Mustang Fever

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That's really lovely, Scott.

I haven't decide yet whether or not I have the courage to build something with four glow engines. My pal down state did, a 100" cardboard monster with four OS 61FX's.

I'm considering Ivan's Mars again, and it looks on the surface like there's room for glow engines (maybe 25-35 size) but the electrics are calling to me on this one.

Regards

siddus74

Bob, Thanks,

I have the Martin Mar plans from Ivan they are beautifull . . . . IF I build another it will be that one, how ever I have lookied into the potential brushless setup for that bird and am concerned about the length of the moter / ESC wires required as there are definate do and donts with regards to maximum length of wires etc . . . anybody else care to contribute on this one? G?

Scott..

Mustang Fever

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Scott:

The trick with long wire lengths is the increase the size of the wire, to prevent a voltage drop to the motors. I'm sure that 10 gauge automotive style wire would be large enough for the outboard motors, and maybe 12 gauge for the inboard ones. 10 gauge wire is used for 30 amp circuits up to about 10 feet long in the auto world. The other thing about long wire runs on electrics is that they will wreak havoc with FM radios. The best cure for that is a 2.4 GHz radio. The operating freak is so high that it's immune to onboard electrical interference from long wires, gas engine ignitions, or brushed electric motors. If FM is your radio of choice, the other cure is to just twist the pair of wires (power and ground) all the way along their length. This effectively cancels the magnetic field and the interference that results. A small doughnut magnet can also be placed over the twisted wires to add suppression.

I was thinking of using Rimfire 35-30-1250 motors. (Brushless outrunners) They can run at 30 amps continuous at 11.1V (3S LiPos). That's about twice the power that Ivan has in his prototype, but these were the smallest outrunners that can turn 10 inch propellers so the model will look right. I'm thinking most flying would be done at around half throttle, anyway. With two Flight Power 4350 batteries, the bird should be at least a pound lighter than Ivan's, as the outrunners don't use gear boxes, and the LiPo batteries are about 10 oz lighter than Ivan's 18 NiCads. Getting differential steering with electrics is so easy compared to glow- a micro servo slaved to full rudder travel that operates a left and right microswitch that connects a resistor across the power lines to either of the outboard motor ESCs. (This drops their voltage and slows them down.)

I'm estimating this bird could be built for $850 US, not counting receiver and a few of the servos, which I have on hand.

siddus74

Bob,

You seem to have this all worked out . . . Maybe we should build a couple? As I said previously I have the plan already and enough stock to make a good start - the motor / ESC / Battery setup was the only thing really holding me back (as well as an unfinished Sundrland) but you seem to be confident of setup that will work . . .

Let me know when you get a plan and I'll start building mine, knowing someone else is out there building one would do wonders for the motivation eh?

Scott.

Mustang Fever

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Scott:

Sounds like fun. When I get the PBY done, and after a short break, I'll contact Ivan and get a set of plans.

siddus74

On a real roll now, fixed the EGR valve and pipe on the BMW as well as put the first coat of enamel on the fus, not to mention covering the flaps and ailerons!

All in one evening!

siddus74

Another couple of hours see's the solartex hinges created and the flaps and the ailerons attached . . .

Additional: Engines / tanks and all radio apart from the RX and battery the AUW so far is a shade over 7Lbs so looking at just over 7.2lbss complete ready to fly and thats with glow . . . the estimated UAW with brushless is 8lbs, makes you think eh?

Mustang Fever

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Lookin more gorgeous everyday, Scott. That's really good news about the weight.

I really like using iron on film for hinges, and have done so on many models, large and small.