SW kitfox

[efil 01 74]

hello

here the picture of a little draw i made from internet photos

profils speed vs kitfox.bmp

make me think that it wouldn't be much work to simply update ribs without replacing any rib.

half extention wing (save washout and weigh)and kitfox profile can give a light avid SW a great flyer!

no ?

Edited 5 Dec 2010 by manu F

[dholly 718]

Hey that wing looks familiar!

- If you are suggesting to somehow cut an under camber in the bottom of an Avid speed rib and simply reposition the lower capstrip to transform it into a higher lift airfoil, I do not believe it would succeed IMHO. There would be insufficient web material remaining on underside of the Avid 'modified' speed rib to model to the Avid or Kitfox under camber (the ribs are slightly different), not to mention the rib tails are of completely different design for flapperon hinges. Much easier to make or buy new ribs from Airdale Sportplane and Supply, LLC. Safer as well, I should think sticking with the proven wing/flapperon airfoils and design.

[efil 01 74]

Hey that wing looks familiar!

- If you are suggesting to somehow cut an under camber in the bottom of an Avid speed rib and simply reposition the lower capstrip to transform it into a higher lift airfoil, I do not believe it would succeed IMHO. There would be insufficient web material remaining on underside of the Avid 'modified' speed rib to model to the Avid or Kitfox under camber (the ribs are slightly different), not to mention the rib tails are of completely different design for flapperon hinges. Much easier to make or buy new ribs from Airdale Sportplane and Supply, LLC. Safer as well, I should think sticking with the proven wing/flapperon airfoils and design.

changing bottom line and top ribs too, yes, with plymouth sandwich gluted on original ribs and new capstrips, BTW if you look at trailing edge, flapperons are same place with the two avid airfoils, just because linkage is fixed, this why on speed wing flap seem to be downed. plus this technique keep original tails for flapperon hinges.

[Av8r3400 1179]

The greater question is, Manu, WHY do you want to do this? What type of performance are you looking for?

[efil 01 74]

The greater question is, Manu, WHY do you want to do this? What type of performance are you looking for?

Hello, i will explain more the way of my thoughts :

I'm ready to loose some top speed to get smaller stall because i got the wings not finished, and i want to get safely off my 900ft strip with passenger.

By reading from avid community, i find avid SW is great flyer but poor T off/ landings.

I lookeed to the full extentions, but still thinking it is not the best solution because the excessive washout.

I can sure build new wings, but money is missing for that.

So , having the template of stol airfoil with butt ribs, i can simply change airfoil to stol, but problem with undercamber and wing tank. As i want to keep the 18 galons tank already glueted, i discovered that riblett kitfox airfoil is the similar stol airfoil with less undercamber, so i can more easily make a transition from tank (and same from opposite wing).

So here the compromise : get more lift and AOA with approuved aifoil less draggy than avid stol, get a bit more span but not full extend.

Imagine : less than 500lb empty, 27 ft span, upgraded stol airfoil, and you get a good responsive gentle little plane with more than 3hours of flight available and short field capability...

I know it can scare some who wouldn't change the father wilson design, but here there's nothing unkown imho. (I took from Dave fisher site the letters from Riblett who suggested to change stol airfoil of an avid to a riblett foil with no major changes except the CoG)

[Av8r3400 1179]

Okay. That helps explain what you are looking for from your plane.

A very good friend of mine is doing exactly what you are suggesting. He is currently building a heavily modified C model Avid, but using Model IV Kitfox wings (the famous Riblett airfoil).

The Riblett airfoil that was sold to Kitfox, but not Avid is very similar to the speedwing profile (probably why they didn't buy it). If you compare the two, the Riblett has a very subtle undercamber in the first 1/3 to 1/2 of the chord and by subtle, I mean less than 1/4". The speedwing is nearly flat on the bottom.

I believe that you will be surprised at the performance of the (unmodified) speedwing profile with the extensions added. If you build the plane as light as you intend the performance will be astounding.

That being said (and I'm sure Leni will disagree - I don't have his hundreds of hours of bush flying experience), I think 900 feet is too short no matter what wing you have. That isn't to say the plane won't do it, I'm sure it will - with a bit of room to spare - but you as the pilot will have to be near perfect on your performance every time, especially on landing. There will be little, if any, room for error. If your strip has wide open approaches on both ends I will take this concern away (mostly).

IMO, I think you are needlessly modifying your wing for the gain of only a couple of MPH on the landing and TO speeds.

Edited 6 Dec 2010 by Av8r3400

[efil 01 74]

Okay. That helps explain what you are looking for from your plane.

A very good friend of mine is doing exactly what you are suggesting. He is currently building a heavily modified C model Avid, but using Model IV Kitfox wings (the famous Riblett airfoil).

The Riblett airfoil that was sold to Kitfox, but not Avid is very similar to the speedwing profile (probably why they didn't buy it). If you compare the two, the Riblett has a very subtle undercamber in the first 1/3 to 1/2 of the chord and by subtle, I mean less than 1/4". The speedwing is nearly flat on the bottom.

I believe that you will be surprised at the performance of the (unmodified) speedwing profile with the extensions added. If you build the plane as light as you intend the performance will be astounding.

That being said (and I'm sure Leni will disagree - I don't have his hundreds of hours of bush flying experience), I think 900 feet is too short no matter what wing you have. That isn't to say the plane won't do it, I'm sure it will - with a bit of room to spare - but you as the pilot will have to be near perfect on your performance every time, especially on landing. There will be little, if any, room for error. If your strip has wide open approaches on both ends I will take this concern away (mostly).

IMO, I think you are needlessly modifying your wing for the gain of only a couple of MPH on the landing and TO speeds.

i forgot to mention that my strip is 7% with one way Toff , other way Landing. currently with my little bipe, i could leave more than half rnw to the cows