Sig kougar leading edge issue
02-17-2019, 03:41 AM
#1
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Sig kougar leading edge issue
Hi
I am building a Sig kougar and ran into an issue when trying to fit the 1/4x3/4" leading edge. It fits fine at he wing tip but it looks like the wing is to tick at the wing root. It is not wide enough to cover the sheeting on the wing and i wil have to sand the sheeting down to the wing core to get a nice transition. Is this the way it is supposed to be?
Lars
I am building a Sig kougar and ran into an issue when trying to fit the 1/4x3/4" leading edge. It fits fine at he wing tip but it looks like the wing is to tick at the wing root. It is not wide enough to cover the sheeting on the wing and i wil have to sand the sheeting down to the wing core to get a nice transition. Is this the way it is supposed to be?
Lars
Last edited by larscato; 02-17-2019 at 04:28 AM.
02-18-2019, 04:10 PM
#5
My kit had the same issue!
I just added some balsa like everyone else and started sanding.
Also, I flew the Kougar every time I went to the field last year. It's a helluva design and is a blast to fly. No wonder it's been around for 4 decades.
I just added some balsa like everyone else and started sanding.
Also, I flew the Kougar every time I went to the field last year. It's a helluva design and is a blast to fly. No wonder it's been around for 4 decades.
02-18-2019, 05:08 PM
#6
I would just replace the pieces supplied with a new piece wide enough to cover the entire leading edge, height wise. After that, a small block plane or belt sander would be used to take off a majority of the extra balsa prior to the final sanding. This would eliminate the chance of any hard spots that could result from adding additional material to the supplied pieces
02-18-2019, 06:40 PM
#7
I would just replace the pieces supplied with a new piece wide enough to cover the entire leading edge, height wise. After that, a small block plane or belt sander would be used to take off a majority of the extra balsa prior to the final sanding. This would eliminate the chance of any hard spots that could result from adding additional material to the supplied pieces
I used good ol' Titebond wood glue, which sanded easily enough for shaping. I keep moving further and further away from CA on every build.
02-18-2019, 06:49 PM
#8
02-18-2019, 07:40 PM
#10
On the contrary, you said what works for you and I don't have an issue with that. You also said you don't normally use CA, to which I just pointed out is only one of several kinds of adhesives that will harden balsa and affect how it sands, or other ways of finishing it. As far as I'm concerned it's all good
02-19-2019, 07:54 AM
#13
Maybe off topic, maybe not.... Since we are discussing leading edge construction now would be a good time to design in the flight characteristics one wishes the plane to exhibit.
Scott
Scott
02-19-2019, 08:05 AM
#14
My Feedback: (6)
I don't remember what I did with that. I do remember all the shaving and sanding to the leading edge and wingtips that covered the back lawn . LOL
I made the mistake of covering mine in brushed aluminum Ultrcote. After a few yards out it was barely visible, sorta like a Romulan cloaking device.
Last spring I tore it all off and recovered it to resemble USAF trainer with Safety orange and white. Much better now.
Mine's powered with a Scorpion 3026-10 4s and 11X5.5 prop. A comfortable speed for me. With a 5S and 10X7, the anxiety levels get too high.
I made the mistake of covering mine in brushed aluminum Ultrcote. After a few yards out it was barely visible, sorta like a Romulan cloaking device.
Last spring I tore it all off and recovered it to resemble USAF trainer with Safety orange and white. Much better now.
Mine's powered with a Scorpion 3026-10 4s and 11X5.5 prop. A comfortable speed for me. With a 5S and 10X7, the anxiety levels get too high.
02-19-2019, 09:05 AM
#15
My Feedback: (19)
Now a disclaimer: Nothing wrong with those old SIG kits and they were produced and flown in unknown thousands, maybe even millions? But like most things in our hobby, a bit of understanding goes a long ways and can make the building / flying experience more pleasant.
Last edited by Truckracer; 02-19-2019 at 11:52 AM.
02-23-2019, 04:08 AM
#16
From my limited 30 years of experience it is usually best to follow the plans and use a consistent leading edge from root to tip . Too sharp of a leading edge will allow a quicker stall but also make a more response but less predictable plane. Read that as don't do it you'll crash faster . The Kougar is an excellent flyer as built per plans without airfoil modification
02-23-2019, 05:06 PM
#17
My Feedback: (19)
Look at 20 kit built planes and I bet you find 20 different LE shapes. Nobody really does it the same and the instructions don't address the radius issue. You may have one view of an airfoil cross section if you are lucky. I've built some high end kits that supplied shaping templates for both the root and tip LE. Some pattern planes stated LE radius on the plans. It was especially critical on pylon racers where a sharp LE could make a plane unstable in pitch and snap happy in high "G" turns.
02-23-2019, 06:43 PM
#18
If you look closely you can see the the TE of the inboard section actually has some sweep, outboard of the wing struts the TE is straight.
The reasoning for making the root LE sharper then the tip LE is to help promote the inboard section of the wing to stall before the tips. The theory is that the airplane will stall more predictable and with more control. When I designed my Divergent pattern airplane I used this technique not only on the wings but the stabs as well. The feature was designed into the airfoils. Another feature I used was the airfoil percentage thickness was actually increased from root to tip. It's a double taper wing so at half span the cord was reduced by 1.75" but thickness remained the same, at the tip the cord is 6.5" which is 50% of the root cord but looses only 35% thickness. The TE of the wing is fairly sharp at the root as well but 3/16" thick at the tip. The end result is an airplane that is extremely predictable and must be forced to stall. In fact both snap rolls and spin entries are now flown through with virtually no stall presence.
02-23-2019, 08:18 PM
#19
The leading edge of the wing is critical in the flying and stall characteristics of the wing. Post 16 is the response I expected when I first commented on LE shape. To each his own, I expect my planes to perform in the manor I will fly them. Race planes are kind of picky.
That being said... Shawn, if you fly through a spin entry it is not really a spin, is it. don't get me started on that...
Scott
That being said... Shawn, if you fly through a spin entry it is not really a spin, is it. don't get me started on that...
Scott
Last edited by Pylonracr; 02-23-2019 at 08:21 PM.
02-23-2019, 09:06 PM
#21
Scott