Slow delta wings?

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delta

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Interesting Rick. Is that the motor mounted up high? if so, is it meant to be angled upwards? I'd be worried about abnormal thrust lines normally associated with top mounted motors? (nose over effect)
Hi Doug

I was planning on having the engine mounted in the aft fuselage and running a toothed belt reduction to propeller pod atop the verticals. The pod would not be angled up as the model shows. I don't like the high thrust line aspect either, but I love the large slow turning props. I've been experimenting with my own propeller design and haven't really decided whether to go with the large diameter prop or a ducted fan on this one. Either way, I hope I'll be able to incorporate the automatic angle of attack idea I've been working on. The ducted fan would probably be better since I plan on being able to fold the wings and take to the road as a three wheeled motorcycle when the weather gets bad. I'll still have a boat bottom, but have decided to put off the amphibious portion (hydrofoils) of the project for now.

Later...

Rick
 

Norman

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I was planning on having the engine mounted in the aft fuselage and running a toothed belt reduction to propeller pod atop the verticals. The pod would not be angled up as the model shows. I don't like the high thrust line aspect either, but I love the large slow turning props.
You don't have enough elevator authority to rotate for takeoff with your thrust line that high. You may be able to get it to launch by using a really long nose gear but you're still going to have to fight that negative pitching moment from the propeller with a lot of elevator input during the entire flight. The thrust line should pass through, or as close as possible, to the center of gravity.
 

delta

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You don't have enough elevator authority to rotate for takeoff with your thrust line that high. You may be able to get it to launch by using a really long nose gear but you're still going to have to fight that negative pitching moment from the propeller with a lot of elevator input during the entire flight. The thrust line should pass through, or as close as possible, to the center of gravity.
Point well taken and understood. Thanks for the input... I just got all excited watching the pedal powered MIT catamaran and decided big is beautiful... I guess it's on to the DF and all its headaches.

Rick
 

Aircar

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look up Arthur Zimmerman's work on very low aspect ratio (circular equivalent) aircraft -- inspired in part by the Arups and based on research done by him at NASA Langley --he later was in charge at Chance Vought aircraft of building the V 173 test bed and later the XF5U --both twin contra rotating tip prop/rotor configurations described as "flying pancakes or Flying flapjacks" at times --hardly slow at 500 Mph top speed and zero bottom speed ( VTOL or minimal ground run limited by angle of attack but able to hover in free flight -- his one man version was 7 ft span and prone pilot --the really minimum dimensions for a single person vehicle but also a very low minimum speed by virtue of the slipstream enhancement of lift .
 

delta

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Hi Doug

When going through the archives looking for folding wing ideas, I noticed you're planning on folding too. Have you found any good info yet applicable to the delta? I've found some dyke stuff that might be useable, but haven't found any detailed drawings.

Later...

Rick
 

deskpilot

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Not planning on folding wings Rick, but removable outer panels for towing purposes. As they stand at the moment, the fins will also have to be removable due to their tips being oversize at 9ft wide. I could over come this by changing their geometry and or size.

I don't have detail of any folding system but there's plenty on the web to give you ideas. Just make sure it's impossible for them to fold in the air.
 

delta

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Hi Doug

I just measured my bird. It's 13ft long with a 13ft span. Needless to say, I'm planning on wearing it. I'll probably wind up with removable panels too as it'd be a lot simpler in the long run.

Later...

Rick
 

dirk_D

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Hi deskpilot, just wondering if you have flown scaled rc version of your design?
The airfoil seems quite symmetrical and neutral, wouldn't that have the pilots view pointed upwards 10 or so degrees?
Maybe play around crashing a few rc models before you cut any metal, it could refine your design cheaply.

I am watching this thread, i hope to see you cutting metal eventually and I wish you good fortune and success!
 

deskpilot

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Hi guys. Thanks for your input and suggestions/questions. Ltatly Ive been taking another look at my wing profile and have decided to increase its depth from 9.5% to 12.5%. I've also moved the pilot rearwards about 12" for better balance (I hope). So far, I've stopped building a model until I have the wing more sorted.

12.5% wing minus winglets rear quarter.jpg12.5% wing minus winglets.jpgWing sections 4.jpg
 

dirk_D

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I too am basing an R.C delta project on the space shuttles wing design, but adding gently curved winglets. I've heard of a design issue called bernoule's principle which roughly goes along the lines of the viscosity of air increasing as scale reduces - air acts differently.
But, heck - it's better than nothing. if the model is proven and i get good enough to fly it in a 'cocky' manner (induce stall - recover) then it goes on the back burner for upscaling whilst i get my student pilots license.
If it flies poorly and no amount of modification makes it fly confidently one could always resort to a subaru powered edge 540 scaled home brew!
 

Norman

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I've heard of a design issue called bernoule's principle which roughly goes along the lines of the viscosity of air increasing as scale reduces - air acts differently.
Stop listening to whomever told you that! Bernoulli's principle simply applies Newton's conservation laws to fluids to show how speed and pressure affect each other, it has nothing to do with viscosity, in fact it neglects viscosity. The Reynolds number shows the ratio between viscous and dynamic forces in a fluid.
 

grounded

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that little french plane reminds me of a propeller version of the Lippisch P.13a that the germans designed at the end of WW2....
 

dirk_D

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The verhees genius lays in the lack of fuselage, the entire width of the craft is airfoil. Plus i managed to google an airfoil cross section it is no plain old naca generic type, he must have spent 100's of hour coming to that design.
I am discovering through my rc model that a small delta wing and slow speeds are not happy bedfellows. (crashing)
Small wings like speed and an airfoil to match, hats off again to the verhees!
 

delta

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The verhees genius lays in the lack of fuselage, the entire width of the craft is airfoil. Plus i managed to google an airfoil cross section it is no plain old naca generic type, he must have spent 100's of hour coming to that design.
I am discovering through my rc model that a small delta wing and slow speeds are not happy bedfellows. (crashing)
Small wings like speed and an airfoil to match, hats off again to the verhees!
I've had some that would land gently around 5mph, but admittedly had a pretty light wing loading...

Rick
 

Lynne Wainfan PhD

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The plane from the 60s that you're probably referring to was the Dean Delt-Air. I built a peanut-scale (13"/rubber-powered) model of it back in the 80s and it flew well.
Dean's problem was his thrust line. He lifted off and pitched way up before of course pitching down.
The plane was tested in the U-Michigan wind tunnel (where I went to aero engineering school) and of course they didn't evaluate the thrust line. Was a real shame--Herb Dean was not an engineer but he was close to doing something very impressive.
 
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