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Old Apr 24, 2012, 10:00 AM
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Knoll53's Avatar
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From what I'm reading the "adjustable thrust line" concept would most likely need to be adjustable in flight and be tied to the throttle setting. Atleast it would if you wanted power to be pitch neutral at any setting.

Does that sound right?

Kent
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Old Apr 24, 2012, 10:15 AM
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Knoll53's Avatar
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Quote:
Originally Posted by HerkS View Post
The best way to visualize it is to ask "where is the drag produced, and where is the thrust aimed."
This makes sense to me. That is, the thrust should push directly through the Center of Drag. Otherwise, the thrust will create a pitch moment.

The CG could be wildly different than the Center of Drag depending on fuselage design. An example of low CG (which produces a pendulum effect) is C5A. This low CG would not affect the thrust line. The thrust line remains tied to the Center of Drag.

comments?

Kent
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Old Apr 24, 2012, 12:34 PM
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Stupot46's Avatar
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Let's see if Ive got this right.On a linear twist wing with a constant chord,ignoring any drag from the prop and housing,and say 10o of twist.If the prop shaft is at 5o it is on the centre of drag?
Stuart
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Old Apr 24, 2012, 03:03 PM
Herk
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Quote:
Originally Posted by Stupot46 View Post
Let's see if Ive got this right.On a linear twist wing with a constant chord,ignoring any drag from the prop and housing,and say 10o of twist.If the prop shaft is at 5o it is on the centre of drag?
Stuart
Depends on dihedral - and twist really. On a clean flying wing you could assume that the center of drag is somewhere about the AC on the MAC. If the wing has a lot of dihedral then down thrust would help because the drag production is probably centered above the center of the motor. Also the natural twist will produce a nose up moment when speed increases - (ie at higher power setting) so down thrust can help with that as well.
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Old May 14, 2012, 04:49 PM
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Since Richard posted the drawing of the HoXVIII I've bee wondering how I could build this wing,one of my favourite Hortens,without paying for cad work.I've done measuring on the plan of the VII,and think I could adapt it.
My question is,would these airfoils work if blown up 50 or even 100%.At the larger size,which I would prefer,the centre would be 840mm long and 120mm at it's thickest point.
I'm thinking foam,a two piece centre section split down the centre and each wing done in 3 sections.This would make the cutting easier and should give me a reasonable facsimile of the twist.The finished plane would be in 3 sections with the outer wings attaching at the u/c legs.
Stuart
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Old May 14, 2012, 06:02 PM
Herk
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Where will you put the cockpit? And who will get in and fly it??
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Old May 15, 2012, 01:33 AM
I don't like your altitude
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I've got one of those little kids who race camels stashed in a box under my bed.It will only be just over 2.4 m span,so not that big.
What prompted my question was Jens problem shrinking the Manatee,which I know is an extreme case.
Stuart
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Old May 15, 2012, 01:11 PM
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This is the revised drawing.Not the best pic,but I think it shows where I'm going with this.I intend starting cutting this as soon as the VII is a compete airframe, as a time filler.The bigger sections will be good practice before I have a go at a Colibri.
So- does the panel think this will work aerodynamically? I would appreciate comments,as I don't want to spend time makings drawings to be blown up if this is not a practical project.
Regards Stuart
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Old May 18, 2012, 09:13 AM
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One for our boffins.Is there a way to work out the volume of a wing.I'm trying to come up with a guesstimate of the weight of foam so I can see what sort of power would be needed to get this thing off the ground.
Regards Stuart.
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Old May 18, 2012, 09:21 AM
Deniable plausibility
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Wing area in m^2 * 0.66 * density of foam (in kg/m^3) should give a decent 'ballpark' figure for the mass of foam in kg.

Richard
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Old May 18, 2012, 10:27 AM
I don't like your altitude
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Thanks Richard,that should get me started.
Regards Stuart.
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Old May 19, 2012, 03:38 AM
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Does anybody in the uk know of a source for 100 mm thick foam.The stuff I usually use is Polyfoam xps 500/1200/50 from Wickes.This has a density of 30.I can't seem to find anything online that doesn't have some facing material attached.
Regards Stuart
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Old May 20, 2012, 06:48 AM
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At a loose end today,can't get any gear till Tuesday(the lhs guys go flying sun/mon-what's the world coming to!)
So I did a drawing to get a sense of the size of this beast.All the measurements taken off the iPad screen;I just stretched the half span to 12cm and went from there.
I slimmed the wheels a touch,and I need to check the u/c angle off a bigger printed copy,otherwise it looks ok.
I should be able to get a max.60 mm edf in the nacelles so power should be adequate.Good wheel bearings and a firm tyre methinks.
Not quite as scary as I thought it might be;just the pylon design to work out.
Regards Stuart
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Old May 20, 2012, 06:58 AM
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Stuart ...

I leave you alone for 5 minues and now its a jet powered rocket sled .... . So let me get this straight, you have drawn one pod and it has TWO EDF bolted to it?? is this right or am I interpreting the drawing wrong as this would mean the other wing will have the same for a total of 4 EDF??

EDIT, oh I totally forgot on page two is where this rocket is heading sorry about that Stu, man that would be awesome if you can get her to work. !!

Jens
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Last edited by kleinaberfein; May 20, 2012 at 07:01 AM. Reason: overlooked something
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Old May 20, 2012, 07:09 AM
I don't like your altitude
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Jens,if I put 4/60mm in it would probably tear the wings off.Once I know how much I need it'll be 4 small fans,or easier 2 and 2 dummies.
Stuart
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