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

Model design question

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Old 01-01-2003, 06:57 PM
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BMatthews
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Default Model design question

First off a Happy New Year to all you go fast types here...

I like to drop in here and look around from time to time and all this talk does get my fires stoked so perhaps I'll just have to make one of these some day soon.

But I'd like to pose a question here. Most of you will admit, I think, that all the deltas and swept wing stuff looks cool but isn't really the optimum setup for going fast AND turning fast all in the same model. Deltas in particular tend to get draggy very fast when called upon to do a lot of lifting.... like in a fast high G reversal.

So why don't more of the models in this section look like pylon racers? Or at least FAI pylon racers with thinner fuselages? Or, perhaps even better, Speed 400 electric racers scaled up to 40 glow size? Sort of like a 40 to 44 inch span version of this SUKOL shown below.

I'd love to see something like a 36 inch version with a hot Nelson 15 and the rear exit tuned pipe......
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Old 01-02-2003, 11:26 AM
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Paulus
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Default Model design question

I was thinking exactly the same thing in this thread :
http://www.rcuniverse.com/showthread...84&forumid=162

Greetings,

Paull
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Old 01-02-2003, 01:26 PM
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Default Re: Model design question

BMATTHEWS said:

"But I'd like to pose a question here. Most of you will admit, I think, that all the deltas and swept wing stuff looks cool but isn't really the optimum setup for going fast AND turning fast all in the same model. Deltas in particular tend to get draggy very fast when called upon to do a lot of lifting.... like in a fast high G reversal.

So why don't more of the models in this section look like pylon racers? Or at least FAI pylon racers with thinner fuselages? Or, perhaps even better, Speed 400 electric racers scaled up to 40 glow size? Sort of like a 40 to 44 inch span version of this SUKOL shown below.

I'd love to see something like a 36 inch version with a hot Nelson 15 and the rear exit tuned pipe...... "

Do you mean something like this? This is a photo of my son Paul with his third generation own design he calls Aurora III. If you want to go really fast, design and build a 1/2A size airplane with a hot .40 on it. This one smokes with an old K&B Quickee 500 motor on it.

He designed his first speed plane when he was 13. He is in the middle of building Aurora IV now. IV will be the cleanest, smallest airframe possible for a .40 size engine. It will also have a good F3D engine on it.

For more of our speed planes, go the Mississippi Gang website at this link: http://home.jam.rr.com/missgang/ and click on Jet Hangar.

Dennis Lott
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Old 01-02-2003, 03:13 PM
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ChuckAuger
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Default Deltas vs other..

I don't think it's a question of deltas being faster...it's just that a guy can buy a Diamond Dust kit or Whiplash ARF and go faster than about 98% of the people he flies with for a pretty small chunk of change.

Of course you can go faster if you get into the $700 F3D racers or the like....or faster yet with the giant scale racers. By then you are up to a $10K aircraft.

Or go about 90% as fast for a couple hundred dollars, no rules to build by, etc. Just my view on the situation.

Looks Like Dennis' son has a good idea about how to go fast without an expensive plane..it can sure be done. I just bought a book on low drag airfoils and drag reduction. I plan to build a small plane someday, but I can't build it as fast or as cheap as a Dust. Or look at the Magnum, not extremely expensive but moves right along.
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Old 01-02-2003, 05:10 PM
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banktoturn
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Default Model design question

BMatthews,

Apart from some extra wetted area, I don't think the deltas are all that draggy in level flight, since they are, after all, flying wings with no extra stuff to add drag. The main problem with most of them is the lack of fairings. Engines, pipes, and linkages are certainly causing much more drag than the wing. In turns, you could do better than the delta for drag, but the flying wing delta configuration is very forgiving, easy to build strong, and has so much wing area that it turns tight and can fly at fairly slow speeds. Overall, not a bad solution for the armchair speed demon. Also not the optimum one, as you point out.

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Old 01-02-2003, 05:22 PM
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Default Model design question

I see that after a slow start to this thread the silent underground movement is speaking out.........

B2T, that rapid speed loss in tight reversals is what I was thinking about. Most of the guys here are paying a fair chunk of money for the engines and some of the RTF deltas are not all that cheap either so a molded and bagged ARF racer wouldn't be that far out of the question it would seem.

And thanks for the link Jetjock.

I guess the easy availability of the Whiplashes and DD's just won everyone over as you said.

It's all fun in any event. I've got an AAC off shore 46 in the box. I may just have to build something for it like this. I know it's not an MVVS or a Nelson but it'll be fast enough for me.
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Old 01-02-2003, 05:46 PM
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Default Model design question

BMatthews,

I know what you're saying. Even though there is a fair amount of drag in turns, these are light planes with powerful engines, so the turns aren't THAT slow. More importantly, straight-line speed is the primary figure of merit here, which is why there is so much discussion of radar guns, and no talk of lap times. I think it is fair to say the most happy owners of Diamond Dusts, Whiplashes, etc. want to fly really fast in a straight line, and be able to toss the thing around with abandon. Delta wings fit that bill pretty well. A highly optimized pylon plane probably would not. I think there are some other airframe layouts that would be even better than deltas. If I actually build one, I will post pictures.

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Old 01-02-2003, 06:12 PM
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Default Going Fast

I agree with Chuckauger. For most go fast types, a DD or Whiplash will provide plenty of cheap speed thrills. For the ultimate cheap, go with a DD. I have had several of the Diamond Dusts, and they are a very good plane for the money. After having the experience of playing with Daryl's Whiplash, I think it is better for maximum speed. It is much sturdier and stiffer for going 200 plus, and you can't blow the covering off one of them. The new Whiplash Extreme should be the ticket for those who want to go fast and not spend time building from scratch.

When you want ultimate speed, you are going to have to scratch build.

I hope to see some of you guys down here in the sunny south this spring for the Mississippi Speed Event.

Happy New Year to all.

Dennis Lott
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Old 01-02-2003, 06:31 PM
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Default Model design question

Heres my effort at going fast, an old MDS 38 with a 10x6, used to keep up with any MVVS 40 speedster.
low drag was the idea.
deltas have a couple if disadvantages... first, to hide the gear they have thick roots, which taper all the way down the wing = high drag, my own design delta had thin wings and a fuz, up to 30 mph advantage over any other plane at the field on the same engine.
Second is the symetrical deltas have to fly at a AOA to get lift, this leads to vortices behind the wing and slows it down. Flat bottom sections cure this.
There was a post ages back im trying to find again where the perfect design was discussed.
I've got a few ideas in my head that time and money allowing should lead to something really diffrent and fast
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Old 01-02-2003, 06:46 PM
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Default Model design question

phillybaby,

While it is true that a section with the correct camber will have lower profile drag, a flat bottom likely has too much camber for high speed. In any case, it is the lift itself that causes induced drag ( the 'vortices' ), not the angle of attack. It doesn't matter whether how you generate lift, induced drag increases as lift increases.

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Old 01-02-2003, 06:55 PM
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daven
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Default Model design question

I'm suprised there is not more talk in regards to the Kangke F3D that can be seen here:

http://www.boltonsales.com/boltonsales4_006.htm

This plane looks very similar to a modern Quarter 40 pylon plane, but costs about $139.

I would bet, with the right engine, and a small amount of reinforcing, this plane could hit 150+ Mph with a Jett or Nelson .40.

Then again, you could go with the plane in my Avatar (Vendetta by Lyle Larson). I believe the kit is about $400, and with a Nelson QM40 engine, I've had speeds close to 190mph.

I'm not a big delta fan, because I don't like hand launches, or belly landings. My planes are going to have landing gear.
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Old 01-02-2003, 08:59 PM
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Default Model design question

i went with the throey we're not very good at flying, and So a delta would be all wrong due to trim, thrust ect and you'd end up sucking air with you. with mine i drew the camber line, then lined the rest of the fuz with it so i wasnt pushing through the air, at least thats how i saw it in my head. i just did things i thought would work. the tailerons didnt, but the shear speed for the engine and prop used proved for me a few things. the next design looks very different and i'll be paying very close attention to what wing and section i'll use
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Old 01-02-2003, 10:13 PM
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Default I had the same thought BMatthews.....

I have been watching this forum for some time thinking the same thing also.

At our MrSpeed trials in Memphis, most of the true speed planes were converted pylon planes. There were people flying clipped wing q500 racers with no landing gear and cowled engines. Then there were people flying converted F1 ships running the venerable OS 46 VRDF, and finally there was myself and one other friend using converted QM15 planes on Cox 15 racing motors. Converted racing planes were always substantially faster than anything else-especially flying wings and Deltas...

I think the other guys are right, "plug and play" seems to have been the mantra for the past few years, and the Whiplash allows just that. "Plug and Play" Speed!---but not the optimum to go the fastest.

The Austrians/Europeans have proven that the way to truly go the fastest is with a slope glider which is built for the task.

That brings up a possible difference in the way Europeans and Americans do things....... Americans generally try to throw horsepower at things to make them go faster. Europeans generally spend their time refining the chassis or airframe and the power delivery.

Neither method is inherently wrong, and it has proven in history that it usually takes a little of both to hit the ultimate goal.
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Old 01-02-2003, 10:34 PM
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ChuckAuger
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Default Gliders...

Yep, the low drag airfoil/drag reduction book I got is based on gliders, but of course I'll do the American thing and put a hot engine on it.. It also has some chapters devoted to strong wing structures..ought to be fun if I can digest the info.
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Old 01-03-2003, 05:11 PM
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Default Model design question

where can i find sections for those slipperly plylon wings to cut from foam? current idea needs them.
why is that Kangke so quick... just looks like any other sunday flier well built, the long and hardly lacking in chord go against most peoples ideas of speed, i've heard alot before and remembered the basics. Is the canopy just a rules thing?
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Old 01-03-2003, 05:40 PM
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Default Model design question

Originally posted by phillybaby
where can i find sections for those slipperly plylon wings to cut from foam? current idea needs them.
why is that Kangke so quick... just looks like any other sunday flier well built, the long and hardly lacking in chord go against most peoples ideas of speed, i've heard alot before and remembered the basics. Is the canopy just a rules thing?
You can go to martin hepperle's site for some interesting reading and fast airfoils: http://www.mh-aerotools.de/airfoils/index.htm

The canopy's are obligated in most ic. pylon classes.

Greetings,

Paul
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Old 01-03-2003, 05:55 PM
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Default Model design question

canopys...and you guys wanna go fast
kinda like in buggy racing where your not allowed tinted windows and only cut outs in the shell if the real car had them, also no 3 door car shells, must be 5 door LOL!!!
for the yanks the 3rd/5th door is the boot, sorry trunk
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Old 01-04-2003, 10:54 AM
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Default Model design question

A canopy is a nice place to put stuff in...kinda like the "boot" of a car...
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