Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Fast enuff?

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Old 04-10-2007, 07:51 PM
  #1  
Mustang Fever
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Default Fast enuff?

Do you guys think this one will qualify?

She's an old Pavel Bosak design, that he did for Radio Control Model World (UK). All the balsa sizes were metric, so I had to convert everything over, but the actual build hasn't been too bad. (Started January 1st this year.)

If you want to see all of the pics, there's a thread under "Scratch Building".

Specs:

55" OAL
51" WS
750 square inches ( I think)
10 pounds (estimating)
Tower .75 with an 11x8 MAS prop.
Cline pressure system (tank is on the CG)
Robart 510 spring down retracts w/struts

Pavel claimed 120 mph for his with a piped Rossi 61, in 1990, when the build article was published, and that he designed it specifically to be a pattern bird, and that it is quite docile given the performance envelope.

I built it because all four of my Shrikes have snapped out and died over the years, and I wanted a jet, but mostly I wanted a Phabulous Phantom. If this one works out, maybe someday I'll get enuff courage to start my AK Models SU-27.
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Old 04-10-2007, 08:49 PM
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phjoker
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Default RE: Fast enuff?

I was following your build awsome job it looks great. Here is the link to the thread[link=http://www.rcuniverse.com/forum/m_5193889/mpage_1/key_/tm.htm]F-4 Build thread[/link]. Keep up the good work
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Old 04-10-2007, 09:30 PM
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Default RE: Fast enuff?

That is looking really good
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Old 04-10-2007, 10:47 PM
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Default RE: Fast enuff?

Looks very nice.
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Old 04-11-2007, 07:11 AM
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Default RE: Fast enuff?

Thanks, guys.

I'll put some more pics up here later. I should have the fuse covered by this evening, and maybe get the weight and balance checks done.
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Old 04-11-2007, 08:59 AM
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Default RE: Fast enuff?

Sensational job so far.....

Id say its going to be pleanty quick ..... and if nothing else, will "look" fast
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Old 04-11-2007, 12:12 PM
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Default RE: Fast enuff?

Mustang:

Great looking scratch bird. Your only apparent weak link overall appears to be the Tower 75 motor. A couple of club guys have them, ok for sport flying but not much on rpm even with a decent Nelson or Jett muffler. If you dont want to pay for a Jett 60LX (the ultimate in great sport high rpm motors IMHO) you may try a Webra 55. Thing is a beast and will turn a 9 X 10 (yess 10) apc over 18K with a jett ultra thrust muffler. Shocked me frankly. I expected the engine to be very hot after its first flight proped that way, but no, normal and still has its normal compression. My Webra 35 gets so hot with a 9 X6 apc that all compression is gone after its first run of the day, and then comes back and runs ok again after a few hours. Same story with 8 X 6 and 9 X 5 etc. Screams its guts out for you and then must rest for a day or so. Too bad, hot little cheep motor. Before you guys yell, I admit the motor has not seen much bench break-in time. Circumkstances demanded it must perform now, it does, for one run. The 55 had almost a gallon of 10% plus 4 OZ castor, prior to being put to work on its first flight.
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Old 04-11-2007, 01:46 PM
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Default RE: Fast enuff?

9x10 18k+ WOW
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Old 04-11-2007, 02:29 PM
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Default RE: Fast enuff?

Double wow. That figures out to 170 mph, and 6.38 pounds of thrust. All at the cost of only 2.73 HP.

I could very well be persuaded to try that some day, but it's doubtful, as I'm 60 years old and I don't think my head could turn fast enough to keep up. The T-75 should get me close to 100mph, and should provide over 8 pounds of thrust. With a 10 pound bird on grass, that's important.
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Old 04-11-2007, 02:37 PM
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Default RE: Fast enuff?

GRASS? now here it got covered with SNOW!
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Old 04-12-2007, 12:16 PM
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Default RE: Fast enuff?

Hi!
Nice model!
But it will not be that fast...at least not at that weight and with a Master Airscrew 11x8 prop.
Try a 11x7.1/2 -11x8 APC instead ...or a 10x8 -10x9 APC !
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Old 04-12-2007, 02:25 PM
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Default RE: Fast enuff?

Jan:

I've got one of those MAS 11x8 S-2 (Scimitar). Aren't they supposed to be similar in performance to the APC? I've had pretty good luck with them on T-46s. Fast enuff for me, anyway.
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Old 04-13-2007, 06:34 PM
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Default RE: Fast enuff?

Just now found an 11x8 APC in the box of Phantom parts.

She has to be balanced, and the tail cone area finished, then she'll be ready for engine breakin.
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Old 04-14-2007, 03:33 AM
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Default RE: Fast enuff?

Like the old '57 Chevy saying, your F-4 is "evil, wicked, mean and nasty". Hope it flies as good as it looks. Get the plane flying first with a conservative prop, like the 11x8 before trying props with higher speed potential but worse all around flyability. Just like choosing a torque converter for a street rod, you have to be honest with yourself about how the machine will get used.
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Old 04-14-2007, 10:21 AM
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Default RE: Fast enuff?

Pigg:

That's a plan. I'm thinking of using the 12x6 break in prop for the maiden. It will provide close to 10 pounds of thrust, and about 85 mph, which should be enuff at first.
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Old 04-14-2007, 11:14 AM
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Default RE: Fast enuff?

It looks friggin' awesome!! [sm=thumbup.gif]
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Old 04-14-2007, 03:12 PM
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Default RE: Fast enuff?

Thanks, mon.

You know, once I figured out how to build it straight, it wasn't particularly difficult. One of the easier "plans built" birds I've attempted, at least as far as the framing. All the engineering and planning ahead for various items to be installed, now that part took some thought.

I'd sure like to send Pavel some pics, but I don't know if he's still at the address on the build sheet. (After 17 years, maybe yes maybe no.)
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Old 05-09-2007, 10:56 AM
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OK, been awhile since I posted on this. The bird is complete. After much testing and fiddling, I settled on a "jumper tank" type fuel system- an 11oz ducted fan tank right above the wing, laying flat instead of vertical; and a 1.5oz bullet tank up behind the firewall beside the nosegear. Nothing else would work. I couldn't make the Cline system function correctly on a Tower engine, and the 14 oz bubble jett tank can't be got low enough to prevent severe siphoning in a level attitude. (I couldn't set the idle with it.) With the 12.5 oz system, I set the needles for 12 minutes of running, mostly full throttle, and I still have about 1/3 of it left after that time limit.

The T-75 is all broken in. She'll turn an 11x8 Master Airscrew Scimitar at 14,000 on the ground. That should work fine upstairs.

Discovered a bit of washin on the left, outer wing panel. So, even tho she looks like I cracked up on the maiden, it's just a bit of slice, patch, stick back on.

Wing loading wet is about 35 oz per square foot. I'm gonna go join the Midland, Mich RC club and the first flights will be from that 600' paved runway.
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Old 06-22-2007, 07:46 PM
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Default RE: Fast enuff?

The Phantom Phlew today! Visiting my daughter and her family in St. Louis, so went over to Buder Park, where I have a permit card.

Two nice 350' paved runways, and the wind was about as good as it gets there. Short flight, involving pumping in some up elevator trim and a flameout due to an overrich setting. That was the proof of the pudding- a downwind deadstick. Based on the bird's performance during that episode, if you ask me "should I build one?", the answer is emphatically YES. The glide performance was astonishing. It started at a point roughly at the center of the runway, about 150 yards out and maybe 275 feet altitude, upwind. Glided down well past the end of the runway, perhaps 100 yards, then did a more or less continuous left turn, keeping the nose down about 10 deg. The bird lost very little speed, and showed no signs of stalling or dutch rolling or anything- just grooved on down.

I got the nose up over the end of the runway, maybe 25' altitude, and just let it settle. She touched down about 1/3 from the end, and I got on the brakes. Rolled about 2 feet into the grass at the end.

It's been awhile since I posted on this- the Tower 75 got sent back for a refund because the second carb had the same condition as the first- full of machine marks in the housing that caused the throttle to lock up, and a crummy idle because of the air leaks caused by the poor machining. Tried my brand new Magnum 91. It's still at the service center in CA, after almost a month. It vibrated so bad near peak that it kept shaking the muffler apart. The bird flew today with an OS 91FX. Can you guess what my engine purchases will be from now on?

I made the decision to eliminate the flaperons and use channel 5 for airbrakes after flying my 4*60 at the Midland, MI club where they also have a paved runway. I felt there was really very little control of the airplane on the hard surface. It wanted to sail downwind, and on upwind landings I had to kill the engine to keep it from rolling off the end. I ended up with a BVM 2.6" system and their smooth stop valve for the F-4. Lovely, lovely system. Worked absolutely right the first time. It was great fun fast taxiing the F-4 to the end of the runway, slowing down and turning into the wind, and then winding up the engine before releasing the brakes.

Is she fast? Oh, yeah. Even at only about 11,000 rpm with a 12x8. The engine now has enough fuel through it to peak it a bit. Clean, this bird should be good for 110-120mph.

Wish I could remember what my Revver Brother number is.
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Old 06-23-2007, 07:33 PM
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Default RE: Fast enuff?

looks like a very nice plane you have their....does it have retracts?
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Old 06-24-2007, 02:25 PM
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3D

The retracts are the Robart spring down series, drilled for 3/8 struts. The system works real nice. I plan to use them on the next flight.
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