Double delta wing design

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Starman

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I do want to be cautious, I can make the front of my fuselage cross section round in order to eliminate the full length strake (ogee) going to the nose (SR-71 style), I can also eliminate the 'double' part of the delta, but would rather just make it smaller. I also wanted to avoid rolling up the aluminum by using a diamond shaped cross section all the way to the nose.

I've been wondering about how this vortex unpredictability affects stability more than lift but lift enters into it too at landing speeds. I read somewhere, either on this thread or on the internet, that the double delta is the first planform of the delta styles to suffer from vortex breakdown.

So the question is what happens to the stability when the vortex breaks down on a double delta?

The two possible scenarios that I can think of are: 1.The vortex makes the main (rear delta) part of the wing produce lift so when the vortex is lost then it makes the craft pitch nose up. Or 2. When the vortex breaks down it causes the front, which is harder working to lose lift also. When the vortex goes away then the wing is stalled and then the stability is dominated by the area and center of area which would drop the nose. Similar to the results you would get with the 'cardboard cutout' method that can be used for initial determination of vertical tail volume, which would drop the nose.
 
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Jan Carlsson

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Some goodies with J35 Draken, in super stall, Cobra and more

Jan
 
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Starman

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Thanks Jan, those were fun to watch. It looks like those who voted for #1 option, nose pitch up at vortex breakdown won! ... and that is so cool too because it means I'll be able to do the Cobra maneuver in my delta.

Just kidding. I read that a wing is only considered a delta if it has a sweep of 55 degrees or more, and my copy of the Avro Vulcan planform will then technically be a swept back low aspect ratio flying wing rather than a delta. Also, the 'double' part of the delta or the gothic arch nose is rather small compared to the gigantic double delta on the Draken so what I need to figure out is how much effect this will have on the large Vulcan style wing and if it is dangerously destabilizing.

I noticed that even though they can do the cobra that they can easily get out of it with evidently full control.
 

John Tavares

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Apr 26, 2013
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Bankok, Thailand
Hello Michael. Great to hear that you are also into delta and or flying wings. I think that your background is probably more than sufficient and as you have said, you intend to have other professional people in the industry check your data before you build. I think that if you can keep things as simple as possible, then there will obviously be less issues to deal with and if the wing loading is relatively low, then the handling characteristics re control input, can be more easily predicted and the flight characteristics should be more forgiving. I am also busy in the final design of my own double-delta/flying wing and in the process of building a 40% scale model with real time video and data telemetry with on-board solid state data store. The real aircraft is 16' feet long & 24' span. Is a single seat, has twin vertical fins, retract undercarraige, 4 blade 60" CSU pusher with 100HP Rotax, AUW 800 lbs., carbon composites, using pre-preg honeycomb where suitable. As you can Possibly tell, the HP to weight ratio should be sufficient for good acceleration re take-off and climb and the wing span of 24' & wing area of approx 140 square feet, should help somewhat with more predictable & benigne handling qualities and provide a reasonable rate of climb. CL/max. The 40% scale model weight =51 LBS & 6.4HP. When I have the data back from the large scale model towards the end of 2014, then after further testing, I will be able to finalize and freeze the design for the full size build. I like the photoshop of Pylon 500's delta five and I hope that when he builds, it will fly as good as it looks. Michael, I am going to be very biased here and venture to say, ditch the complex cannard and just go for the double delta, keep the wing loading as low as you can, by having sufficient wing area and I am sure that whatever you decide to go for, will be a personal success, as I believe that you have more than the correct attitude to realise your goals and dreams.

John Tavi.
 
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Jan Carlsson

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สวัสดีและยินดีต้อนรับสู่ฟอรั่มนี้

Do you have any pictures of your design?
 
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