flying wing CofG

[Andy Freeman]

Here is a question that has been puzzling me for a while. Hopefully some of the knowledgeable Gents on here can help me out with.

On flying wing models what is the best indication of having the CofG spot on?

A dive test with neutral or slight pull out? or how much down it needs when inverted? or a mixture of both?

I ask as i have one model that performs a dive test with no "tucking" or pulling out yet needs a fair bit or stick input to maintain level inverted flight.

Your help much appreciated.

Andy

[Tim Mackey]

My guess is that the wing is merely not very good at flying inverted, due perhaps to it being semi symmetrical in section?

[Andy Freeman]

Thanks Timbo. That is an explanation I had not thought of.

 

If it helps any its one of those models that slopetrash gets upset about on this forum

[Tim Mackey]

LOL....yeh most if not all them tend to do that - if flying very slowly or even just virtually hovering (inverted) they start what we on the orme call the Wildthing "nod" where it seems that its nodding its head....probably stalling/recovering/stalling/ .... and so on.

I believe the WT uses a modiifed EH2/10 section which is not symemetrical.

[ken anderson.]

tim-andy is one of the lesser member's of the 'hill top posse'...if you see him flying - you will see a few nodding their head's..................  ...he's like cc carr on a bad day....

 

     ken anderson ... ne 1..

[Tim Mackey]

LOL

[Andy Freeman]

He has got a nasty side that Ken! Mind you, I have a photo of his better side that might have to be posted

[Slopetrashuk]

Posted by Andy Freeman on 10/05/2010 15:36:56:

Thanks Timbo. That is an explanation I had not thought of.

 

If it helps any its one of those models that slopetrash gets upset about on this forum

 I felt a disturbance in the force.....What's going on here?

 

 

 

 

 

 

 

[Slopetrashuk]

Posted by Timbo - Administrator on 10/05/2010 15:52:16:

LOL....yeh most if not all them tend to do that - if flying very slowly or even just virtually hovering (inverted) they start what we on the orme call the Wildthing "nod" where it seems that its nodding its head....probably stalling/recovering/stalling/ .... and so on.

 

 

 

That nodding is known now as a Hyperstall.

 

This from the NCFM website might help:

If you experience any pumping (or "hyperstall" as we came to name it), it is, in fact, a stall, or rather many little stalls and many immediate recoveries. When any other "non-straight-swept" airplane stalls, it usually drops a wing and spirals down...that's the beauty of a straight / forward swept wing... they very rarely drop a tip. Rather, if off CG, allowed to stall or given way too much elevator, they simply hyper-stall and then immediately recover; (this also allows for near-vertical landings). If the lift suddenly disappears, just let the plane cruise and allow the airfoil to work... you willl gain much more lift over 50 yards than slowing the plane down with too much up elevator.

There are really only 2 causes for hyper-stall: An "off CG" and / or too much elevator input in light lift. In medium to heavy lift, and if the CG is dead-on, it's just a matter of making sure you don't have too much elevator or radical exponential throws. Once both CG and travels are dialed-in, you will quickly find that sweet spot where the plane snaps a turn and rockets out the other side!

 

Shunt the CG rearward with a sticky weight and reduce your elevator throw slightly as you go. You will reach a point where the model will fly inverted with very little down elevator - Yes, even on a WT. Whether you can live with it's pitch characteristics then is a matter for personal taste.

 

Andy

[Andy Freeman]

Thanks for the explanation.

I shall give it a try..

 

[Tim Mackey]

Posted by Slopetrashuk on 11/05/2010 07:52:56:

Posted by Andy Freeman on 10/05/2010 15:36:56:

Thanks Timbo. That is an explanation I had not thought of.

 

If it helps any its one of those models that slopetrash gets upset about on this forum

 I felt a disturbance in the force.....What's going on here?

 

 

 

 

 

 

 

 

LOL

[Tim Mackey]

Oooh hyperstall...is that like hyperflight but more bumpy

.....Good explanantion - thanks Andy

 

Edited By Timbo - Administrator on 11/05/2010 10:24:14

[Craig Carr]

 

Posted by Timbo - Administrator on 11/05/2010 10:23:59:

Oooh hyperstall...i

 

I had hear that phrase "hyperstall" a few months back during a chat with the lads.....  none of us had heard of it before and thought the lad in question was getting ready for a trip with the men in white coats.

 

Now we know.......  Thanks Andy  Im off to sign his release papers 

Edited By Craig Carr on 11/05/2010 12:04:03

[Slopetrashuk]

Hyperstall was the phrase coined by Harris Nelson in discussions about setting up the original NCFM Bluto 48 back in around 2002. Let your buddy out!

[Tom Satinet]

the ncfm m60 exhibits the same characteristic very markedly if flown in a certain way and/or with a forward CG. it's a bit like one of those nodding dogs you see in some people's rear car windows, but quicker. Although more tasteful. 

[Former Member]

[This posting has been removed]

[Slopetrashuk]

Maybe back in your day Eric but these days modern sections can be quite trick. Reflexed but very high performance, high speed and very aerobatic. Most fly easily upside down and only require small inputs to get the best out of them.....................

 

Oh no wait! This is a Wildthing isn't it.

 

Scrub that Eric.

Yeh! You'll need loads of down.

SAS models use a version of EH 2-10 that was traced around an old slipper that once stood on a faxed and photocopied version of EH 2-10 that had been scribbled onto the back of a fag packet.

 

 

 

 

Oh I feel better now...

 

Andy

[Andy Freeman]

Mine is actually a Fusion, but I guess they are one and the same.

 

On a serious note, are there actually and combat/disposable models that stand head and shoulders above my Fusion? I have found myself looking at the flying wings Slipstream over the last few days...opinions please..

[Tim Mackey]

I have the slipstream Andy, and althought its nice - agile - and responsive on high rates its not a combat model IMO. Too light ( around 14 - 17 oz ) and exposed control horns, somewhat flimsy winglets etc.

This may be of interest, although the film was only really done to demonstrate its launching for someone

Edited By Timbo - Administrator on 12/05/2010 22:19:54

[Tom Satinet]

ref the fusion and the issue Eric is talking about. In my experience you never can get the CG far enough back on the fusion to have the lack of reflex you can have in a high performance model. Well you can but it's not flyable.  so you will tend to need a fair bit of reflex on the elevons even with a reward CG.

[Slopetrashuk]

This is a product of the poor section. EH2-10 is very old school and marred the flight performance of models like the Birdworks Zipper which needed constant re-trimming in pitch depending on the forward flying speed no matter where the CG lay. Upgrading to sections like PW51 solved these issues and produced a faster flying, less draggy model.

Notably Stans choice of MH42 (Phoenix Models) never really sufferred the same on his wings and you could shove the CG back to the sweet spot. None were as quick as the 'secret' NCFM sections until Peter Wick released some new coordinates. Models like the Retox bear this out. Fast flying wings with little or no reflex on the control surface. It's all in the section. Inverted hands off is very easy to achieve without compromising control. Even the new Weasel EVO is easy to set up well.

Modern sections faithfully reproduced.

Not something SAS can claim for their range.

 

Sure they fly well. But there are 'better'.

 

Andy