Fairings at the wing root  
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Fairings at the wing root - 11/26/2007 9:57:34 PM   
iron eagel



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Joined: 7/15/2004
From: Middleboro, MA, USA
Status: offline 		I am building a Sig Something Extra one of the many mods I intend to make is to fair the wing into the fuselage. It is my understanding that this will reduce the drag that is caused when you normally have with a square joint to the fuselage.

Your opinions/suggestions...
One consideration I am thinking of using is to raise the AOA of the faring at the fuselage. I am of the understanding because of the built in washout of an SE wing that tip stalls are not an issue anyhow, but this just would be an enhancement to that design, not to mention it would look good. I also intended to round of the lower part of the fuselage as another improvement to reduce drag. The aircraft will have a full cowl over an inverted engine mount as well as the vertical and horizontal stabs having airfoil shapes and no flying wires.

Why you may ask, just to have a SE that has a clean look.

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The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185
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RE: Fairings at the wing root - 11/26/2007 10:38:58 PM   
da Rock



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Joined: 10/11/2005
From: western, NC, USA
Status: offline 		Interesting ideas, all.

There isn't going to be much room for fairings. To get a significant savings in drag from them would require they be decently large. But heck, whatever you can do is going to look kewl.

If you are interested in reducing drag, then lose the stab stiffeners. Those and the landing gear create more drag than the entire fuselage. They basically double what the fuselage creates. Oh wait, I just reread your post and you're planning that. Excellent.... Losing the flying wires is an excellent drag reduction move. Also, while you're doing the extra work, take some time and simply round the LE of the gear struts and taper the TE of same, and you'll have some drag reduction. And if drag reduction matters, then do NOT leave the wheelpants off.

You might consider placing the engine sideways. It just might give better ground handling and a cheekpiece cowling is about as low drag as possible for realistic looking cowls. Frontal area matters and sideways does that well.

You've got some good ideas. That's the beauty of this hobby. If you can think it, you can probably do it.

(in reply to iron eagel)
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RE: Fairings at the wing root - 11/26/2007 10:53:48 PM   
da Rock



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Joined: 10/11/2005
From: western, NC, USA
Status: offline 		I've not seen that the airplane has built in washout. And I've not seen one to know, but it's picture looks like it's a straight taper wing. Those things naturally stall from the fuselage out anyway. And it looks like a symmetrical airfoil. You do not want to mechanically twist a symmetrical airfoil. The Tower specifications don't mention washout. That'd make sense, if it is a straight taper and symmetrical.

They do mention using the ailerons as flaperons. I really don't think anyone would want to do that with a tapered wing. So that also suggests it's a straight wing.

I really like your idea about airfoiling the stab/elevator and fin/rudder. Just looking at the airplane just now..... It looks pretty, but the bracing on the tail ruins it for me. It's like fingernails on a blackboard to me. It's a cheap way to strengthen something that should have been designed better. In real life, it's usually a cheaper way to build. Or done when cantilever is beyond the ability of the mfg or the workforce.

Looking forward to some construction pictures.............

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RE: Fairings at the wing root - 11/27/2007 8:30:46 AM   
BMatthews



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Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		Iron Eagle, the SE is a full on aerobatic model. As such you really don't want to alter the wing incidence setup from the 0-0-0 setup it has already. At least you don't want to do this if you wish to retain the traits that it was designed to have.

As for the fairing go ahead if you're after it for looks. But really drag with such a model isn't a big deal. The typical size of the engine for aerobatics makes any such drag a total non issue. And if you're after speed then this is not the model you should be building since the surfaces are wide enough that if you try to go that fast it's going to flutter and destroy itself.

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RE: Fairings at the wing root - 11/28/2007 12:20:08 AM   
iron eagel



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From: Middleboro, MA, USA
Status: offline 		Bruce,
It is mostly for looks, I know that the overall reduction of drag probably will not be all that much of a change, with the exception of the support wires on the tail. I am not looking for high speed performance, I have a one of Mike Connors' "Screamin Demons" for a high speed bird, just cleaning up the plane a bit. I had hoped that just increasing the AOA of the faring at the wing root would not cause degrading of the overall performance. I intend to use a 3/4 inch radius on the farings from the wing to the fuse.

I had also thought about adding horner style wingtips, perhaps not that good of a idea...
It's just that those big blunt wingtips do not look all that great, perhaps a better idea is just to make them tapered and leave it at that.

I have started a posting in the kit build forum but have not added to it yet, as I am trying to work out all the details of changes I hope to make. Among the changes planned in addition to those above, Adding 10-15% more rudder area and where the wings will have the wingtips added to the span I wanted to enlarge the horizontal stab and elevator by the same percentage as I am adding to the wing area.

I had thought about cutting down the ailerons at the root and adding flaps, I am not all that concerned about roll response that I will lose by doing this. I also am going to add hard points to the fuse so I could add payloads or weight to the finished airplane. I hope to use this plane as a warbird trainer it has been a long time since I had flow a plane with high wing loading and by adding weight at the COG I could vary the wing loading to get the feel of flying a warbird again without trashing one in the process...

The main reason I had considered mounting the engine inverted within a full cowl and it would be very easy to make the exhaust for the hot air under the main fuse behind the cowl. This exhaust would end right about the LE of the wing, this will add more side area ahead of the COG and should enhance the Knife Edge performance...

After looking through the manual and at the plans again I am trying to figure out where I gotten the idea that the wing had washout....

< Message edited by iron eagel -- 11/28/2007 12:24:38 AM >

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

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RE: Fairings at the wing root - 11/28/2007 2:01:14 AM   
Tall Paul



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From: Palmdale, CA, USA
Status: offline 		Don't remove the tail bracing wires!
The structure is poor back there.
The wing as built on the plan comes off the board with built-in washin.
And the suggested c.g. is way conservative.. 25%.. most fliers move it way back from there.
SIG took no notice of the difference in airfoil thickness between the root and tip when laying out the construction instructions.
When asked to explain, they came up with 'it improves "decoupling" ".. whatever that might mean.
I doubt wing root fairings will accomplish anything worthwhile at the speeds and manuvers the SE does.

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RE: Fairings at the wing root - 11/28/2007 2:47:37 AM   
BMatthews



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From: Burnaby, BC, CANADA
Status: offline 		Well, if you're looking for a warbird trainer that sort of doubles as a sport model then I'd say you'll get a lot of results doing what you're planning. It's still an odd choice of model given the SE's original intended flying style but what the hey. Have at 'er and all the best.

Although.... if I was looking for a warbird trainer I think I'd look at doing a sort of "Stand Way Off and Squint Scale" (SWOSS ) model that uses a more or less warbird layout. Picking a sport or pattern sort of model and adding a big scale sort of looking fuselage wouldn't be that hard to do. Something like a SWOSS Skyraider would actually be a bit cool. And the fuselage would be big enough to stick a camera into. Meh... just a thought.

A few years back a local guy had a Sig Kadet that he'd built up with a lot of experimental metal work details that he wanted to use on a quarter scale model later on. The Kadet came out at 10 lbs... so he added an extra rib bay on each side. It didn't help much, I think I heard that he got something like 10 to 20 flights out of it before the odds called in the debt. But something similar but lighter and with gobs of washout and perhaps the Selig 8035 airfoil to help out would be an interesting heavy trainer.

< Message edited by BMatthews -- 11/28/2007 2:50:23 AM >

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RE: Fairings at the wing root - 11/28/2007 2:53:38 AM   
iron eagel



Posts: 1325
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From: Middleboro, MA, USA
Status: offline 		I noticed that there are issues with the structure of the tail, that is why I plan to replace both the horizontal and vertical stabs with airfoil shapes, fully sheathed (1/32 inch), and using composites for the spars to stiffen them as well as allow for more ridged mounting to the fuselage. As an additional note, I intend to sheath the plane and use carbon fiber veil applied with dope for the finish.

I thought it had wash-in but when I looked at the manual, I did not come across mention of it.

Thanks for the hint about the COG I will have to keep that in mind.

Gee, I thought that putting fairings would be a big plus, given that thick wing sticking out of the fuselage would cause a lot of disturbed airflow along the rear portion of the fuselage. Oh well, I guess I will just have to do it because it will look good, hopefully without screwing up the design, or performance to much...

I have got to find out how this would improve "decoupling"....

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

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RE: Fairings at the wing root - 11/28/2007 3:09:07 AM   
iron eagel



Posts: 1325
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From: Middleboro, MA, USA
Status: offline 		Bruce,
A couple of months ago I slammed a thirty year old TF Mustang into the ground. Not even the motor survived I'm not to sure about what happened, it may have been a high speed stall. Lost control and got into a spin up high, stopped the spin and when I tried to pull up the nose came up and the plane continued down nose high till it hit the ground. Hence my wanting to try something else before I trash another old plane still knocking the rust off.

The main reason for the SE is that I have it and it is designed for more performance than a trainer would be. I have a brand new OS 55AX I plan to put in it so power to weight should not be much of an issue.

I hope to keep the basic flying weight as close to the 4 lb figure as possible so as a sport plane it will still perform, and by varying the wing loading I may be able to see how it reacts with more load.

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

(in reply to BMatthews)
       Post #: 9

RE: Fairings at the wing root - 11/28/2007 8:04:48 AM   
BMatthews



Posts: 9015
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		IR, I'm sure you'll learn something from the effort. It's an odd model to do that with as it's totally out of character for that sort of design but if you've already got it then go for it.

As for your Mustang I'm sorry to hear about the loss. It sounds like you may not have let it accelerate downward to restore flying speed before pulling up the nose or that perhaps you pulled up too hard and re-stalled the wing. Just guessing based on your description.....

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RE: Fairings at the wing root - 11/28/2007 11:21:25 AM   
da Rock



Posts: 6982
Joined: 10/11/2005
From: western, NC, USA
Status: offline
quote:

ORIGINAL: iron eagel

Bruce,
A couple of months ago I slammed a thirty year old TF Mustang into the ground. Not even the motor survived I'm not to sure about what happened, it may have been a high speed stall. Lost control and got into a spin up high, stopped the spin and when I tried to pull up the nose came up and the plane continued down nose high till it hit the ground. Hence my wanting to try something else before I trash another old plane still knocking the rust off.

The main reason for the SE is that I have it and it is designed for more performance than a trainer would be. I have a brand new OS 55AX I plan to put in it so power to weight should not be much of an issue.

I hope to keep the basic flying weight as close to the 4 lb figure as possible so as a sport plane it will still perform, and by varying the wing loading I may be able to see how it reacts with more load.



It sounds like a kewl project. It's amazing how much more interest you have in an airplane you change than one you buy and fly. We got us a great hobby, don't we.

I think it'll work well to get back your touch, but don't expect it to be much of a warbird trainer. That wing is nothing like one that'd be on your average warbird.

And after noticing in the pictures that it looks like a low aspect ratio, fully symmetrical design, and hearing that it builds with washout.... and that the airfoil thickness changes from root to tip, but the designers didn't seem to notice..... and they suggest flaperons to help make the landings safer......... that sucker ought to be an amazing learning experience.

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RE: Fairings at the wing root - 11/28/2007 5:33:20 PM   
Tall Paul



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From: Palmdale, CA, USA
Status: offline 		The SE is nothing more than a cobbled up SIG FAZER. Uses the same wing, with no sweep where the FAZER has a straight trailing edge with leading edge sweep.
I guess the modifiers couldn't finger out how to put the wing joining tube in the FAZER wing.
I built up the kit, sweeping the wing ala FAZER, and built a profile fuselage version at the same time.
Both flew fine.
The roll rate on an SE is awesome!
Make absolutely positive the aft wing anti-rotation dowel is GLUED in place!
One of the SEs at the field was landed with extreme difficulty.... "interference" was blamed. when I pointed out to the owner and the flier that the right wing was not held by the dowel, and with aileron deflection became a very LARGE wingeron! Which of course would roll the plane -opposite- the commanded direction.
Seems the builder missed the instruction to glue that dowel in place. And it vibrated out of the right wing into the fuselage, with most of it in the left wing.

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RE: Fairings at the wing root - 11/28/2007 11:45:04 PM   
iron eagel



Posts: 1325
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From: Middleboro, MA, USA
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