Head wing cantilever.

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TFF

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Most people don’t look to the side directly high or low. Personally turning around a point and looking, the low wing beats a high wing. The high wing rolls into the view while the low wing rolls out of view. If you are straight and level trying to take a picture like a map, I will go with high. From a helicopter, I have taken or flown for thousands of pictures and keeping the rotor blades out of frame is hard to do. Eyes doing what they are supposed to do in the air, and hey don’t look to the side. Not against high wing in fact real airplanes have a top wing and a bottom wing.
 

Toobuilder

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My first airplane was a Hiperbipe - perhaps the worst configuration for outward visability with the exception of the Spirit of St. Louis.

EVERY airplane Ive flown since then is a major improvement. Visibility is highly overrated.
 

stanislavz

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Some real world geometry example:

From Pottier P.130 Coccinelle - Wikipedia which plans i do have at hand.

Main data for UL version is as follow :

1634753120516.png

Naca 4412 airfoil, 3.5 forward swept, 1260 chord and 8000 wing span. And longeron placed at 30% or at 380mm. Top left one example in drawing. Move longeron to 40% of chord - and we can live without forward swept at all.

1634753764974.png

Add some taper (bottom left) - again more sleeker and still with same mid chord placement as in original. And with same taper but some forward swept of 2.2 degree - we can have spar at 35% of chord or have wider cg range... And all this with vw in front. Which is longer and heavier than rotax912...

Am i correct ? Only plain geometry.

On interesting aspects - its have ailerons and flaps with 0.35 of chord.

1634754181728.png
 
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BJC

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Riggerrob

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And a wing structure from bf109.. spar is on 45% chord region
Messerschmitt bf109's main wing spar is that far aft to clear the (retracted) main wheels ... and keep a straight leading edge.
Otherwise, it is structurally wiser to install the main spar at the thickest part of the wing (about 25 percent M.A.C.).
Another alternative is to have a small, leading edge spar (D-shaped) to transmit pitch loads to the forward fuselage, plus main and rear spars.
 

stanislavz

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Another alternative is to have a small, leading edge spar (D-shaped) to transmit pitch loads to the forward fuselage, plus main and rear spars.
Or one can have a short strut to transfer this load.

Ok. Before i will start my own bird thread - worst case scenario at maximum angle of attack most load is at 10-20% of chord. Two struts - all is ok load is transferd by two struts, load of each one depends on aoa.

Cantilever wing with classical airfoil with 25-30% of max thickness position and spar in this place too - some torque load present.

Give it some modern laminar airfoil like ga37 or even ga40 our "arm" of moment is twice as big. And Billski will kill me - but this placement of spar at 45% of chord do cost us 5% of spar height, but solves forward swept wing joining problem. For cantilever one.

But - rans rv12 have rotax 912, and two seats are in front of spar.
 

stanislavz

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One more exercise. KITPLANES Builder Profile: A Checkered Past - AVweb

A Keller’s Prospector STOL Span 33 feet, chord 50 inch, 3.5 degree of forward swept and span placed at 30 and 32%. And wing tip is at 9inch futher at wind tip than on wing root.

So wings geometrical center point is moved at 4.5 inch

Basic math - main spar is at 15" and 16" , and add it 4.5" + some extra half inch will result in 20" and 21" of spar position. Which are 40% and 42%. For GA30 airfoils it is less than few % of spar height loss. For GA35 or GA37 series - it will increase spar height.

So for straight wing without any forward taper one have to move spar location from 30/32% to 40/42%. Which would allow to use cf pultrusion and have simple spar layout and simple spar box to join them.

Where forward swept wing needs an build up spar or use some sort of short wing struts.

In conclusion - this aft. placing of spar will cost only some dynamic cost due to moving center of mass of wing backward.
 

stanislavz

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10 metres wing span, 1.1 m wing chord, Strojnik wing tips, parelel fuselage at wing connection. Stabilator and vertical tail just to be here.. And no motor cowling. And two heavy and big boys.

1635344279379.png
1635344319029.png
1635344357697.png
700 mm lower
1635344469370.png
and 200 mm higher wing postion
1635344517967.png
 

stanislavz

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I guess Wittman learned a lot from Strojnik.

No, wait....
wingtip

;-)
1635347928603.png

It was named like this in a kind of joke..

Just that flay sided fuselage is a now-now for composide.

And there do exist strojnik wingtips for tailwind which lowers stall.

Back to "my design" - this taper an wing tips and higher A/R does allow to shorter chord for view similar as with swept forward wing. And placing wing at shoulder level allow best possible view. But this on need an spar at 45%. But similar is done in bf109, and RV-12. Plus much less of wing area and it possible to have composite front without to many holes.

And maybe minimum of hard points. And one main bulkhead.
 

Vigilant1

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10 metres wing span, 1.1 m wing chord, Strojnik wing tips, parelel fuselage at wing connection. Stabilator and vertical tail just to be here.. And no motor cowling. And two heavy and big boys.

View attachment 117327
Two questions:
1) Do your drawings show the wing spar/carrythrough at the approx 40% chord location you mentioned in Post 34? It looks like it might need to be closer to 50% in your drawing above to clear the heads of the occupants.
2) Do the drawings show the wing at the correct location for your anticipated CG? Given the weight of two beefy occupants, an engine, nose gear, etc the wing seems to be a bit aft of where I'd expect it. Again, just by eye, no calculations.
 

stanislavz

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just by eye, no calculations.
Now just by eye, but with main points placements from pottier p130. Which have vw on front and similar placement of occupants. And straight wing with shorter span.

But, yes will make some cg calculations too.
 

Vigilant1

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Now just by eye, but with main points placements from pottier p130. Which have vw on front and similar placement of occupants. And straight wing with shorter span.

But, yes will make some cg calculations too.
I think the forward sweep of the P130 (like the similar Cygnet) changes the situation, when compared to a straight wing. Or, maybe you've already accounted for that.
 
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