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Old Aug 19, 2012, 01:29 AM
What could possibly go wrong?
nickchud's Avatar
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Nice link Dereck! He did a good job of the build thread.

John:
Quote:
Who knows it might even be possible to make a sea-plane based on this..
I was thinking of a seaplane like that, where the lower wing of the bi-plane is replaced by sponsons. I guess that would suggest that the canard wing should be smaller, or the main wing bigger. Might work!

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Old Aug 19, 2012, 02:54 AM
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Sounds like the first model sea cucumber isn't far away!
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Old Aug 19, 2012, 12:34 PM
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Quote:
Originally Posted by Trevorh View Post
Sounds like the first model sea cucumber isn't far away!
That would be a novel model.

Idle thought, not exactly canardly... Doug was renowned for dreaming up models most of us would only have in nightmares! Imagine a diesel powered low winged semi-scale twin with engine cut-offs that would kill the running engine when one cut and a semi-scale rubber powered twin with four fuselage mounted rubber motors running into a nose end gearbox that drove the props via lots of bits of carefully bent piano/music wire. Both were built with no lathes or similar machining in sight either.

At which point, a free flight biplane canard looks very ordinary...

Looking forward to the resurgence of the Cucumber indeed.

D
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Old Aug 26, 2012, 05:14 PM
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Hi All, I tested my flying wing with canard replaced by an inverted LE (flat bevel) on the wide forebody (30% of total wingspan) of the center section and got very good stability, even IGE.
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Old Aug 26, 2012, 06:36 PM
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If I interpret you correctly, that results in a reflexed airfoil, with the reflexed portion being about the last 95% of the chord. Noot terribly efficient, but it does result in an concave-upwards camber line, and a positive aerodynamic pitching moment.
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Old Aug 26, 2012, 08:58 PM
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Reflex on the nose if there is such a thing. I had a canard on it but started thinking of experimenting with a flat bevel on the underside of the LE to act as up (canard)elevator. The entire model is a T shaped flying with the outer wings swept deltas and inner wing ar of .3 sticking forward as a forebody. The inner wing should be at a higher incidence but untill I build next model I thought I would try the bevel which in effect makes it an inverted airfoil. I hope I explained clearly
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Old Aug 26, 2012, 08:59 PM
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Correction ' T shaped flying wing'
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Old Aug 26, 2012, 09:25 PM
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My idea is contrary to logic because the flying machine I am designing needs to be inefficient OGE, to remain in IMO regs. Today at high speed it remained stable just 12" (about 1/3 wingspan) off the ground. In fact it was very nose heavy and would descend OGE even with full up trim but yet IGE would climb back OGE untill I trimmed down a bit. My goal is to adjust cg and trim to maintain about 1 wingspan height.
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Old Aug 27, 2012, 01:26 PM
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http://www.youtube.com/watch?v=Ipdk9...re=context-cha

sorry about poor quality...

take off and level hands off elevons, climbed it for stall test, dropped her nose after i cut power. released sticks after nose dropped and then pulled up and added power. i think she ran out of eleveator before she stalled.

interestingly i moved cg back and although still nose heavy OGE she actually felt a little TAIL heavy IGE, not as solid and smooth as yesterday.
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Old Aug 28, 2012, 04:10 PM
What could possibly go wrong?
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Professor Ann Dowling

I've just been listening to a really interesting program about the engineer behind this project to design a silent aeroplane.

BBC: The Life Scientific Let me recommend it - fascinating. She is "Professor Dame Ann Dowling, head of Engineering at Cambridge University and one of the UK's top 10 women scientists and engineers."


Nick

PS Here's a link to the 4-view. The plane was designated SAX-40. Not quite a canard, but it looks an interesting project.
Quote:
The airframe makes use of a novel centre-body shape with leading edge carving. This balances the aerodynamic forces without the need for a tail, and enables an optimal wing design with an elliptical lift distribution and low cruise drag.
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Old Aug 28, 2012, 10:45 PM
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Thanks Nick, she's gr8.
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Old Aug 29, 2012, 05:30 PM
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The side view makes it look like the center is an inverted airfoil. That would make it stable without a tail. Also the The forebody mean chord line would be at a higher incidence than the wings and also act as a canard. My model became stable without a tail when I introduced negative camber at the LE of the forebody.
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Old Aug 30, 2012, 06:23 AM
What could possibly go wrong?
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I've been Googling around and searching for SAX-40 without finding any previous efforts to build a flying model of it.

I think I could make those shapes out of Depron, with the aid of a rolling pin and by cutting out some wedges to make 3-D curves. As you say "The side view makes it look like the center is an inverted airfoil." or just a fat belly . What's going on with that lip around the forebody? It's a bit difficult to see from the diagrams just how big it is and what angles. Technically speaking, could that lip be called a canard?

A lesson I have learnt the hard way is to be sure that those wings will be rigid.

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Old Aug 30, 2012, 12:31 PM
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Very interesting.
The bottom of the center looks like an inverted airfoil but the lip (strake) joining the wing/fuse together with the nose and top of fuse looks cambered and at a lower incidence than wing. The lower incidence may not create much lift/drag in cruise but at higher AOA, like on approach, may contribute much lift for a lower app speed.

If the forebody stabilisies the aircraft and produces lift we may venture to say it is a canard.

My 2 cents...
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Old Aug 30, 2012, 03:00 PM
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Great observations Nick and captarmour, I was thinking the same as you. On modern aircraft, the wings are moving rearward to replace horizontal stabs and extend forward to replace canards. High aspect ratio type wings seem to be a thing of the past. My recent thoughts have been on trying to locate a single motor at the center of the fuselage at the CG point with a low rear wing and a high 50% canard.
It will require a kv of around 2200 and a prop about 4.5 inch diameter.

Captarmour, It would be great to see a picture of your model which was in the video.

Charles
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