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

Plane choice

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Old 09-12-2005, 11:37 PM
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stupidaso
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Default Plane choice

Is the Diamond Dust a good first "speed plane"?

If not, what is?

If so, where do I get one?

I've got 2 OS 46 FXs that are nearly new and run great, and I decided to try one of these fast 40-size singles. I had a duellist that went well in excess of 100 mph, but was a twin and therefore a fair amount of tweaking and syncing the engines.

Any help would be much appreciated.
Stu
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Old 09-12-2005, 11:55 PM
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Default RE: Plane choice

Yes and no- How is that for an answer?

The DD is VERY light and will fly easily with the 46's you have... But if it will be your first delta AND first speed plane I would go with a quickee like a Viper or Predator-

The quickee has LG, and take-offs and landings are typical- so you can get used to the speed without the hassles of launching a delta-

I really enjoyed my Whiplash but wheels come in handy whilst going up and down--
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Old 09-13-2005, 09:44 AM
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Default RE: Plane choice

I wouldn't suggest a DD to get your feet wet. Last year. If it were me I'd go buy a quikee and bolt the 46 in it's nose. Last year I had a Jerry Smith Outlaw with a 36 that I thought was fast until I flew my DD this year with a Rossi 40 and it's much faster.

Besides, the Q500 has landing gear and if you like it you can always build a DD. They only take a day or two to get done depending on how quick you work and how much time you have.

I have both by the way.
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Old 09-13-2005, 10:52 AM
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Default RE: Plane choice

I feel the same as others about landing gear. My Shrike is a blast to fly, but I find the lack of landing gear to be a pain in the butt. Maybe I need to get started on one of the kits (Patriot, F-15, or Kobra) that I've got stashed away. Oops, F-15 is spoken for, can't build that.
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Old 09-13-2005, 10:59 AM
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Default RE: Plane choice

Chuck, you made my stomach knot when I saw the F-15 listed![X(] Lunch tomorrow?[8D]
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Old 09-13-2005, 03:03 PM
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Default RE: Plane choice

I have had fast planes before, I just lost my 2/46 duellist.

I did not know the DD had no gear.... I wasn't able to find a pic of it. Thank you for the info, I'll look at more of a Q500 type plane or stuff a Jett 90 in by old curare.

I checked out the Jett site...holy crap, those are some fine looking engines. Are the performance and reliability as great as I have heard? Not a single person in my club (that I have talked to) has any real experience with Jett.

For the same money, a YS 1.1 could swing a lot more prop, but is a 4-stroke just not a good speed ingine? I don't hear anyone talking about using them in speed planes...

Makes sense, rather heavy and low rpm. My Mustang with saito 100 pushes 100mph with the right prop and fuel.

Thanks again for the help, I love this forum....so much info from experienced pilots.

Stu

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Old 09-13-2005, 03:58 PM
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Default RE: Plane choice

They are giving you good advice in my opinion as well. The Viper with a Thunder Tiger pro 40 is a very nice setup and a handfull of speed. It will also glide in nicely and land very slow. Your are also off the ground straight as an arrow in 3 or 4 feet. You can even use a grass field if you get some better than factory wheels. With your 46, it should be pretty darn quick and will do 180 degree turns in about a half of second, and still be doing over a 100 coming out of the turn. Once trimmed, it's about as stable as anything I've flown. The faster, cleaner planes are great too, but they take a lot more room on landings and don't slow down well. Most club fields don't have enough open area and you will soon destroy it on a landing. The Vipers are cheap and easy to put together in a few nights. I would recommend going with the TT pro 40, so you would be legal for quickie races, just in case you get hooked and want to compete. A Jett or Nelson will be much faster, but they cost a lot more and 428 quickie races are harder to come by, especially on the East coast.

On your first flight, be SURE the elevetor and rudder trim buttons mix on both sides of the V or you will have a wild beast on your hands with no leash. Talk to Mack at Hodges Hobbies in Georgia. He's a great resource and will set you up right.
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Old 09-13-2005, 09:20 PM
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Default RE: Plane choice

YES the Jett's are as good as you have read...

The 4 stroke vs 2 stroke for speed argument is a sensitive one, tread lightly---

You are talking about a YS-1.10 now, they can be made fast on a certain type of airframe but it depends what you have in mind...

Honestly, I would decide what airplane I want first then research engine options.... The Mustang Saito combo. does not compare to a properly set-up quickee or delta, trust me
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Old 09-13-2005, 10:49 PM
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Default RE: Plane choice


ORIGINAL: stupidaso


I checked out the Jett site...holy crap, those are some fine looking engines. Are the performance and reliability as great as I have heard? Not a single person in my club (that I have talked to) has any real experience with Jett.


Stu
I have 4 JETTs flying right now a 40SS .50FIRE .50FISE and A 1.20
they ALL run strong !@!!
the 40SS was rebuilt just before I got it and the single needle carb is GREAT! from idle to wide open

next on my buy list is a.35 for my Wide Hare LR-1

bob Brother #105
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Old 09-13-2005, 11:15 PM
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Default RE: Plane choice

Thanks for the input.

I'm down to 2 planes for this...... a Q500 with my fx46 or my 60 size curare with a jett 90 or ys 1.1.

I am going to go out on a limb here:

In my small and overworked mind (inbreeding can do that) it comes down to thrust minus drag equals speed.

You can have the most thrust in the world, but you will eventually "max out" the airframe.

Conversely, you can have the cleanest airframe in the world and be limited by the thrust produced.........

Don't get me wrong, I LOVE the sound of a 2 stroke screaming at high rpm on a high-speed pass......but I also love a burley 4-stroke twisting a lot of prop.

My only point is that a 4-stroke with the right prop should produce comprable thrust to a "similar" 2 stroke, and therefore yield comprable net thrust on the same airframe..........

That should stir the pot pretty good.....I'll probably NEVER get into The Brotherhood now!

Now......we wait[]
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Old 09-14-2005, 12:10 AM
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Default RE: Plane choice

Stirring the crap eh? The Curare is designed for a 2 stroke, old school speed-pattern... Find the fastest airplanes in the 40-50 size and see what engine is up front--- you started the thread with a request for a 46 sized airplane, remember?

The Curare is not gonna compete with a Diamond Dust no matter what you put up front- The quickee is the best combination of speed and ease of operation--

Dude, here it is... Sell the OS-46FX, put the cash towards a Jett-50, get a quickee- pin the firewall and light your hair on-fire!
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Old 09-14-2005, 09:02 AM
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Default RE: Plane choice

Makes sense to me.......

Thanks again for the help, I'll go in that direction

Stu
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Old 09-14-2005, 09:13 AM
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Default RE: Plane choice

You are right on power output on some of the 4-c engines. The YS engines in particular are outstanding for power to weight. The YS110 is an animal.

However, most 4-c engines are RPM limited due to the valve springs. Most have to be propped to run under 10K rpm on the ground. YS 110s have been known to safely unload up just over 11K rpm in the air. The Jett BSE-120 is the most equivalent engine, designed for lower rpm and big props. Same props, same rpm range. Easily turns a 16x8 near 10K rpm. And although it should not really be run over 12K rpm, it is not physically rpm limited by springs and stuff.

The Jett 90, for example, is the same size and weight as the 120, but by design is not as rpm limited. The rpm key here is the muffler range (And that can be changed). Typically, the 90L runs between 13K and 15K rpm. Prop selection is made by that. Tuned differently, I have had a 90L up to 18K rpm in a ducted fan setup. Engine didnt care (in fact, it loved it).

For speed, there is nothing like a small diameter prop (less disk area, less drag), high pitch, and high rpm.... as long as the plane will go along for the ride
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Old 09-14-2005, 09:30 AM
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Default RE: Plane choice

I see your point, looks like Jett is gonna fill the bill, in both the small and larger planes!

Dumb question: I didn't see any warranty info on Jett's website... is there any?

Stu
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Old 09-14-2005, 09:54 AM
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Default RE: Plane choice

bottom of the CONTACT US page
http://www.jettengineering.com/warranty.html
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Old 09-14-2005, 02:06 PM
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Default RE: Plane choice

Please correct me if I'm off, but I don't think thrust minus drag equals speed. I always thought inches of prop pitch X RPM equal the maximum speed of the aircraft in a perfect world where there is no drag. Since there IS always lots of drag (more the faster you go), you multiply your maximum speed by a percentage of efficiency of the prop, say 80%. This depends on lots of variables and keep in mind drag comes from lots and lots of places. Props, unclean surfaces, airfoil design, control surfaces out of trim or fighting each other, the angle of attack the wing has to maintain if the loading is high, gear, wheels, etc etc etc.....

Try this one Sunday when you are bored. It give you a report card on your building skills. TAC your prop. Compensate for unloading by adding 200 rpm on slow/dirty planes, or 500 or more on fast and clean planes. Best guess here. Multiply rpm x pitch = convert to mph, this is Speed1.

Next, get a buddy to help, stop-watch your plane flying straight and level across a 500' distance both ways. Compute the average mph. It's simply feet per second converted to mph. You can do one leg if the wind is dead calm. No cheating coming out of a dive..... Divide this mph by the computed Speed1 above. The result is your plane's efficiency....

Measure yours against someone elses who plane is faster, but engine, prop, RPM, weight, fuel, and design are equal. Their efficiency will be greater and they'll just smile at you when you ask them what-all they did...... ;o) That's racing boys and girls......

At least that's the way it use to be in the old school...

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Old 09-14-2005, 04:17 PM
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Default RE: Plane choice

cool, thanks
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Old 09-14-2005, 04:48 PM
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Default RE: Plane choice

I agree about *****g out an airframe. I think my Miss LA was maxed out with the .28 MVVS and 8X7 at 13,9. Not too much difference between 3/4 and WOT aside from sound. Still for a small model it is a honker.[8D]
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Old 09-14-2005, 04:54 PM
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Default RE: Plane choice

I was being very simplistic with the "thrust minus drag equals speed" comment, merely to demonstrate my question on 2 vs 4 cycle engine use.

I certainly realize there are more factors involved.

Thank you for the formula, I will definitely use it.

And thanks for schooling me! I knew throwing that out there would generate some good info.

Stu
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Old 09-14-2005, 07:18 PM
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Default RE: Plane choice


ORIGINAL: stupidaso

I was being very simplistic with the "thrust minus drag equals speed" comment, merely to demonstrate my question on 2 vs 4 cycle engine use.

I certainly realize there are more factors involved.

Thank you for the formula, I will definitely use it.

And thanks for schooling me! I knew throwing that out there would generate some good info.

Stu

You are on the right track. When thrust and drag is equal then speed is constant. Increase the thrust and you increase the speed. While a ballpark thrust can be calculated, the drag is much more difficult to come up with.

The pitch and rpm formula may give you a ball park speed in some cases, it also can be way off. A good radar gun or accurate time and distance figures are the most accurate way to calculate speed.
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Old 09-14-2005, 11:36 PM
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Default RE: Plane choice

I agree, Mike.

I have a good radar gun, but I've only used it a few times. This is because I have trouble finding (and asking) someone to let me fly my airplane straight at them at full throttle.

The timed distance method has worked for me, too, although I must admit I have only had one plane with which I was concerned with it's speed.......my Duellist.......and she's gone now

Oh, well. She made me realize how much I love speed!

Thanks for the help and...what is that yellow and blue delta plane of yours? Looks fast just sitting there!

Stu
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Old 09-15-2005, 09:18 AM
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Default RE: Plane choice

It is my second Diamond Dust and my all time favorite WOW factor and speed plane. More pics and short videos on my web page listed below.
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Old 09-15-2005, 03:57 PM
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Default RE: Plane choice

sorry, wasn't trying to school anybody, just want to make sure I hadn't been steird wrong.....
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Old 09-15-2005, 04:29 PM
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Default RE: Plane choice


ORIGINAL: grubs4flying

I always thought inches of prop pitch X RPM equal the maximum speed of the aircraft in a perfect world where there is no drag. Since there IS always lots of drag (more the faster you go), you multiply your maximum speed by a percentage of efficiency of the prop, say 80%. This depends on lots of variables and keep in mind drag comes from lots and lots of places. Props, unclean surfaces, airfoil design, control surfaces out of trim or fighting each other, the angle of attack the wing has to maintain if the loading is high, gear, wheels, etc etc etc.........


..........sorry, wasn't trying to school anybody, just want to make sure I hadn't been steird wrong.....

A lot of people use the pitch and rpm to get a ballpark speed. But as you say, "lots of variables".

This was posted awhile back by Jeremy F. and I thought it was interesting.

-------------------
published in MAAC magazine a few months back.



Aircraft.....................Engine............RPM ........Pitch.................Theoretical mph............Actual mph
6ft Chipmunk............90 4 Stroke.....9540.......14x6..................54.20. .........................84.7
Hanger 9 mustang.....100 4 stroke...9240........14x7..................61.25.. ........................72.43
1/A wing...................061 Norvel.....21,990.....5x3....................62.5. ...........................96.4
Quicky.....................40 2 stroke.....18,500.....9x8....................141.. ...........................139
Diamond Dust..........40 2 stroke.....24,400.....7x8....................184.8 ...........................165

So go figure........
For interest, the article says:

Each competitor must fly straight and level over a 528 foot course, both ways and is timed from two pylons at each end. The timing system used is manual timing to a single stop watch, hard wired from each end. This method has proven more accurate than a radar gun that was used in the past. The flying mile is comprised of five timed laps around the pylons.

So yes, there is room for error etc, but I just found it quite interesting when I read it

Another short excerpt from the article that actually made great sense to me when explaining why an aircraft would move faster than the theoretical pitch would allow was

" 'it's perfectly understandable, it's a rotating wing with an airfoil .' As I had a very good understanding of boat propellers of which always had slip factors of from 12% to 30% it became very apparent that air and airfoil s were very different"

I guess when you consider that a wing in forward motion creates lift, it stands to reason that a forward facing rotating wing will create more pull than just what the pitch of that prop is giving as it's creating lift as well.
I don't understand the physics behind it, nor do I want to, all I know is, I've had airplanes that were radar clocked faster than what they "should" have been going and never understood why, this sort of tells me why it COULD be anyway




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Old 09-15-2005, 04:35 PM
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Default RE: Plane choice

Eh? The only time you can max out an airframe is when some part can no longer handle the aerodynamic loads and it breaks. Drag is proportional to speed squared. If you want an airframe to go faster you need more power. You can theoretically make a Cub fly 250 mph with enough thrust, though of course you run into practical issues. There is no limit to the theoretical speed if you are saying that in some way. But yeah baby, there is a limit to the practical speed when you factor in structural limits and limits to the powerplants available.

The faster you want to fly the more horsepower you need, period. Roughly speaking dynamic thrust is proportional (didn't say equal) to horsepower times efficiency. Efficiency of course bundles some complex "figgerin'" into one number, which involves propellors of course and whatever else. So in theory a 2C .50 runnning at 18k and a 4C 1.10 running at 10K but putting out identical horsepower (horsepower not torque..) and with drag and weight being constant (so induced drag is the same) should be able to drag the airframe along at about the same speed, if you can get the appropriate propellors for each setup to work as efficiently as the other.

Mike D.

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