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

swept wing scat cat 500

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Old 06-28-2014, 06:21 AM
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westwind1124
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Default swept wing scat cat 500

I currently have a scat cat with a YS 45 rear exhaust and tuned pipe. I cut 3 inches off each wing tip and removed the landing gear, turned it into a hand launcher. Sucker is fast but as you all know, always looking to go faster. I am debating building another one with the same setup but sweeping the wings. Anyone tried this? Thought about taking a standard wing and essentially just cutting the center joint at an angle. Then matching the wing tips and adding winglets. Thoughts?
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Old 06-28-2014, 04:15 PM
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The guys who look for every edge possible are the Control Line Speed flyers and the RC Pylon Racers.
These events have been going longer than most people have been alive. Swept wings have been tried, but for models it's more about "SHOW" than it is "GO".
One of the most popular .049 powered models was a swept design, called The GLH. I scaled the GLH up a little bit for a hot .12 engine and without doing a side by side comparison with a more conventional winged plane, having a swept wing on a model this small doesn't seem to be a handicap.
A fairly popular mid-sized RC swept wing model called The Weston Magnum has done 196 mph with the same engine / prop that RC pylon racers with more conventional wings are doing about the same speed.
It's easier to build the conventional wings lighter and stronger, so the advantage of un-swept wings will show up at some point as the models get larger.
Choosing a thinner airfoil, like what they use in Q40 racing will help. Within certain limits, shedding wing area doesn't pay off as well as using the best airfoil. Real thin wings are trickier to build, but there are a few really good threads in the racing forum that take you through it step by step.
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Old 06-29-2014, 04:07 AM
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westwind1124
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Interesting information. I never thought about thinning the wing. I do have to consider though that what I do with it will still allow to be hand launched. Its not anything I am doing for competition so its a strictly for fun deal. The wing sweep idea I like if for nothing more than the cosmetic aspect. I have to believe however that sweeping the wing will give it some more speed if if only slight at best. I guess my question should be restated then. Thoughts on sweeping the wing from a technical/stability stand point with a fringe benefit of maybe a bit more speed?XD
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Old 06-29-2014, 06:57 AM
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Odds are that your Scat Cat if built otherwise stock with that YS is slightly nose heavy. That in its self is costing you speed. If you do nothing else but sweep the wings then you will be even more nose heavy and the result will be even more lost speed. When I was Q500 racing with Scat Cats the standard mods were to take 3/4" off the nose, reduce the vertical area by 20% and reduce the horizontal area by 10%. That brought the CG to where it needed to be and reduced drag of the enormous tail section. The next option for you would be a new wing with a tapering cord, thickness and slightly increased span. I would do a tip airfoil with a cord of 7.5" and thickness of 3/4" and increase the span to 55" this would give you more speed and great turning ability. Keep fairly close to the same wing area as reducing wing area too much will actually hurt speed as the wing has to be flown at an increased AOA to support the models weight and any AOA is massive drag.
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Old 06-29-2014, 07:15 AM
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Originally Posted by speedracerntrixie View Post
Odds are that your Scat Cat if built otherwise stock with that YS is slightly nose heavy. That in its self is costing you speed. If you do nothing else but sweep the wings then you will be even more nose heavy and the result will be even more lost speed. When I was Q500 racing with Scat Cats the standard mods were to take 3/4" off the nose, reduce the vertical area by 20% and reduce the horizontal area by 10%. That brought the CG to where it needed to be and reduced drag of the enormous tail section. The next option for you would be a new wing with a tapering cord, thickness and slightly increased span. I would do a tip airfoil with a cord of 7.5" and thickness of 3/4" and increase the span to 55" this would give you more speed and great turning ability. Keep fairly close to the same wing area as reducing wing area too much will actually hurt speed as the wing has to be flown at an increased AOA to support the models weight and any AOA is massive drag.
Wow, nice response.
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Old 06-30-2014, 06:43 AM
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Other than looking cool, at the low subsonic speeds that models fly sweeping the wings does little else than move the center of lift rearwards.
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Old 06-30-2014, 01:16 PM
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Hmmm. Very helpful information guys. I appreciate it. I may look into that chord and tail reduction this winter. I am likely to change the trim scheme so that would be a good time to do it. I don't think it's tail heavy though right now. I moved all of the servos and battery plus the header tank to the tail and it seems to balance well enough.
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Old 06-30-2014, 02:36 PM
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You would need to mount the wing further forward if you went with any sort of a "jet fighter" amount of sweep.
I'll bet the most noticeable improvement comes from a thinner airfoil and finding the prop that marries the engine to the new wing.
A good plane to look at for design ideas is The Rifle by Angel RC. Angel uses simple construction to create a design that looks more complex / exotic than it actually is.
If you stick with the basic Q500 layout, [except make it thinner everywhere you can] they are hard to beat in general.
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Old 07-02-2014, 11:23 AM
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why not just buy a Q40 plane and put the rossi in it.
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Old 07-03-2014, 07:05 AM
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Westwind - long and short is, sweep won't buy you speed. Sweep is of great benefit as you approach m=1. If you get close to that, please let us know how you did it!

Remember a Q500 is designed to be within reach for the average flier interested in racing, so they have a few design restrictions with the specific purpose of limiting speed, not increasing it. Drag reduction is key - and as already suggested, Q500 wings are limited by the percentage thickness in the rulebook, so thinning the airfoil is a major step. Tapering the wing and lengthening span as suggested improves lift distribution and increases aspect ratio - good things. Fillet those wings and stab, do a good job on the tail surface cross sections, tight hinge lines, etc etc.

There are faster airframes overall, but it is always fun to mod something up to your tastes.
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Old 07-03-2014, 04:33 PM
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Cool, I may just have to find me another kit and try out some of those ideas. if anyone has a "new" in box scat lemme know.
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Old 07-03-2014, 05:32 PM
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I have a Doddger fuselage downstairs, it has been in stasis for several years now. It was intended as exactly this sort of thing, a warmed over Q500 for fun. It has an old ST X-45 FIRE engine on it, because it needs a home, and with a pipe they are known to spin a 9-8 prop pretty well. Now it needs a thinner wing just as described. I already extended the tail moment a bit. Yet another project in the 35%-65% complete stage, waiting in the wings. I'm great at starting stuff but not so gr
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Old 07-05-2014, 12:17 PM
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If you ask me the scat cat is a absolute blast to fly with the stock setup. Pretty fast and actually flies "sport" pretty dang well. The new Q500's go fast but are not nearly as fun to sport fly.
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Old 07-05-2014, 07:25 PM
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Originally Posted by westwind1124 View Post
Cool, I may just have to find me another kit and try out some of those ideas. if anyone has a "new" in box scat lemme know.
I think I have a kit, but I wont be home until Monday.
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Old 07-06-2014, 11:16 AM
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westwind1124
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Cool crazy. If you are interested in coming off of it. PM and we can get things rolling.
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Old 07-06-2014, 01:24 PM
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Cool crazy. If you are interested in coming off of it. PM and we can get things rolling.
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Old 07-09-2014, 02:21 PM
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I have a NIB scat right now for sale in the for sale adds. Shoot me a PM if you want it and we can talk price on it.
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Old 07-11-2014, 09:21 PM
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listed my scat cat for sale. bob
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Old 07-13-2014, 05:08 PM
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I have a used U K Magnum wing to sell cheap. scratch build a fuse for it and go ballistic!
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Old 07-14-2014, 06:15 PM
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I have a Magnum R fuselage and tail group but the wing is pooched.. perhaps we should talk.
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Old 07-14-2014, 06:31 PM
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MJD.

send me an Email at turbinecrazy@aol.com

Just need to be able to box it up

PM and everything else here does no go thru

I get more invoice returned by the mailer deamon thna go thru :-(
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Old 07-15-2014, 11:29 AM
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I did send one to that email. I will try again though
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Old 08-14-2014, 02:36 PM
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Still looking for NIB scat cat if anyone still has one to sell.
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