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Need some feedback on a scratchbuilt design

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Need some feedback on a scratchbuilt design

Old 03-19-2019, 05:20 AM
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Default Need some feedback on a scratchbuilt design

This is my first post on this forum, and I hope to gain knowledge and feedback from here. Since this is my first post, I cannot attach a sketch of the plane, but I did attach some specifications below. This is my first design of a plane and I would appreciate any feedback.Thanks. Purposeendurance, efficiency, fpvWing Span60 inchesITEMWEIGHT (OZ)Stylesleek, modernAverage Wing Chord6.5 inchesMotor w/mount3Powerplant2200 kv 6x4 propWing Area2.71 ft^23x 9g Servo1.12Stabilitywing sweep/washoutAUW35.37 ozESC (40 amp)1.89AirspeedCruise-40 mph Max-60 mphWing Loading12.11 oz/ft^25.8 ghz tx w/ANT0.83Stall Characteristicsreduced tip stallsAspect Ratio9.2OSD2.27Constructioncomposite foam wing/fiberglassTaper Ratio6:7servo extensions0.72Control System433 mhzC/1.3 ghzV or 2.4ghz/5.8AirfoilNACA 2415unaccounted1(semisym)Landing GearnoneSweep5-10 degrees3300 mah lipo9.68Breakdownremoval wingWashoutlowered angleWing3.73Flight timeover 20 minutesof incidenceFuse1.03on wingtipElevator/Rudder0.5(airfoil with largerTail boom x21.9leading radius)Wing Spar1.5Fiberglass2camera4.2
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Engineered Plane - Sheet1.pdf (69.6 KB, 108 views)
Old 03-21-2019, 12:40 PM
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Welcome to RCU, Sifez!
It is hard commenting on the design only from the data.

Last edited by Lnewqban; 03-21-2019 at 03:22 PM.
Old 04-02-2019, 11:20 PM
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Sifez, Welcome Aboard.

Lnewqban is right, it's tough to really tell much. But the numbers do seem decent enough. Especially if you can meet the 35oz total flying weight with the 60 inch span. It'll darn near being a glider at that wing loading.

The airfoil might not be the best choice though. It's rather thick for a slower flying airframe. I'd opt for the 2412 if you want to stick to the NACA series. And perhaps you should also consider the idea of 2412 at the root and symmetrical 0009 at the tips with some lower value of washout to work with the flying wing. And by all means with these airfoil shapes go with the max value for sweep or even more sweep. Otherwise it'll start to be closer to a plank style wing and you'll need to use a totally other airfoil that has a much lower pitch moment.

Outside of that the rest doesn't really mean much other than it's a flying wing. And a fairly high aspect ratio too. Which is good for trying to meet the expected weight but perhaps not realistic if you're new to building model airplanes. It'll require fairly careful choices to keep the airframe light enough to hit that weight target.

I think you're also barking up the wrong tree with a motor that only uses a 6x4 prop. That's VERY small for a model intended for longer flight and FPV. And a Kv=2200 that only needs a 6x4 prop indicates a fairly low total wattage motor.

It's tough to nail down cruise and max speeds. But I suspect that it'll take more motor and prop than you noted down to hit those numbers.
Old 04-03-2019, 10:29 AM
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It does rather depend on what you mean by 'endurance'.
For maximum aerodynamic efficiency a conventional wing and tail is actually better than a flying wing. Something along the lines of a high performance glider, however there is no one ideal solution as other factors can have an influence of the design.
The power to fly is however directly proportional to the planes weight so the chosen design may have to be altered so that it gives the best combination of aerodynamics and structural strength to weight. For instance a high performance glider is designed for absolute aerodynamic efficiency as it has to carry little or no disposable payload. To carry a reasonable payload its very high aspect ratio but efficient wings would be at considerable structural disadvantage.
A flying wing does give some structural benefits but it has to compromise a degree of aerodynamic efficiency to achieve aerodynamic stability.
'Endurance' can be a complex subject particularly if you throw in the efficiency of the motor and propeller!
It may be better to take an existing design (built correctly it will fly) and once you have determined its limitations set about designing modifications to it to move towards improving its endurance.
Old 04-09-2019, 03:23 AM
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I see threads like this on RCU from time to time.The best advice is always to not try and reinvent the wheel. Experienced hobbyists and even professionals are working on the same problem as you are now. And they are putting out some good planes. Fly some of theirs first, and start reading up on aerodynamics and aircraft design. After you know what you are doing and also have some piloting skills, then you can start designing a plane with some chance of success.
OTOH, if this is a school project and you want us to verify your ideas and tell you how to make it work, I realize you may not have time for all of that. We see that sometimes too. Your best bet will be to examine the plans and designs of some successful planes and apply what you learn about structure and aerodynamics to your design. If you don't know why something was done a certain way, think it through or read build articles until you do know. We are here to share knowledge, but there is no substitute for learning by experience yourself.

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