Wing questions

[SuberAvid 617]

Under the fine brokerage of JackAK I am the pround owner of an Avid MKIV HH kit. Not sure if that means or . My intent is to use it to buid a new set of wings for my Avid+ and then put my MKIV back together(maybe I will have a plane on floats and another on wheels some day:rolleyes:) . I need to review the posts Doug made about reinforcing the spar insert and design an insert to upgrade mine. I am thinking about sandwiching an aluminum plate between plywood to make the I beam insert or possibly fabricating an aluminum I beam with plate and angle riveted together. Doug, can you remind me where you posted up your work on this?

I have a bunch of other questions for the group:

1. I am thinking of adding wing tip and flaperon extentions to the wings. The stock wing length gives me about 30.5' wingspan. I think the KF's are around 32' or 34' . Do these seem to perform better on short takeoff and heavier loads? Any opinions on what would be the optimum wing length to shoot for with my heavier Avid+ (1320 Gross)?

2. Is it worthwhile to extend the flaperons with the wing?

3. Thinking of changing the washout from 2" to 1". What do the KF's have for washout and does anyone know what the stall is like with washout at the 1" range?

4. Plan to change the lift struts to 1" tubing. What wall thickness are the stock 7/8" lift struts? Leni, when you did this did you build whole new ones or just cut the 7/8 tube at the ends and plug it into the 1" tube and weld it up? What wall thickness did you use on the 1"?

5. Plan to replace the 1/4" Heim joint on the lift strut. Those who have done this; have you just gone to the 5/16 size?

6. The speed wing uses an aluminum leading edge to smooth out the rib valleys. I know a supercup driver who told me this make a huge difference on a cub. Has anyone done this on their Avid/KF and does it seem to perform better.

7. Jack is using a leading edge cuff on his Avid+ but it is not flying yet. Noticed Doug's new bird has the cuff. Is anyone flying with a leading edge cuff? If so, what is the performance like?

8. Are there multiple sources out there for cuffs? any sources you have would be appreciated.

9. Does anyone have the wing specs for the Magnum (spars, spar inserts, lift struts, Heim joint, drag tubes. etc.)?

Probably more questions to come as I get into this but thanks for any and all information,

Randy

[akflyer 1427]

Randy, Congrats on your new bird! Now your gonna have trouble going back to your cramped cockpit on the MK IV unless you do some mods!

If you are planning on using your old fuse, did you end up with an extra set of MK IV incowl radiators? If so, and if you would like to get a lil money back on your purchase would you consider selling either the new or old ones??

1. I am thinking of adding wing tip and flaperon extentions to the wings. The stock wing length gives me about 30.5' wingspan. I think the KF's are around 32' or 34' . Do these seem to perform better on short takeoff and heavier loads? Any opinions on what would be the optimum wing length to shoot for with my heavier Avid+ (1320 Gross)?

Yes, the kitfoxes I have flown I can get in and out shorter and fly slower. That extra 3' makes a pretty big difference! I would be very tempted to build a set of Catalina wings for your Suberavid!! If Bob would have put bigger tanks in his wings, I would have already made a midnight run on his shop and had them bolted onto mine!

2. Is it worthwhile to extend the flaperons with the wing?

The extended speed wing that I flew just moved the flaperons out and used a tube to extend them on the inboard side. Roll was lighter than quicker than my full length flaperons and I could get it in and out just as short as my HH wing. Stall was a non event just like we are used to.

3. Thinking of changing the washout from 2" to 1". What do the KF's have for washout and does anyone know what the stall is like with washout at the 1" range?

I thought about that when I rebuild my wings and I am kicking myself in the butt for not doing it. I think the latest KF has 3/4" washout. I would love to get that extra inch out of mine right now!

4. Plan to change the lift struts to 1" tubing. What wall thickness are the stock 7/8" lift struts? Leni, when you did this did you build whole new ones or just cut the 7/8 tube at the ends and plug it into the 1" tube and weld it up? What wall thickness did you use on the 1"?

I used 1" X .058" tubes for my new strut tubes. Yes, I cut my old struts off and just slid them inside the tubes and welded them up.

6. The speed wing uses an aluminum leading edge to smooth out the rib valleys. I know a supercup driver who told me this make a huge difference on a cub. Has anyone done this on their Avid/KF and does it seem to perform better.

I have the aluminum leading edges on mine. They were beat up a bit and Steve Winder tried to talk me out of fixing them and told me to just take them off. I liked the smoother look and I too have flown cubs with and with out the smooth leading edge. I left mine on there and repaired the sections that I needed to. What ever the difference, the kitfox still kicks my butt in slow flight and getting off shorter. I can get in just as short, but take a bit more to get off the ground.

Bob used the new plastic leading edge cuff from KF on all his KF wings when he rebuilt them.

Edit: Added the link to Dougs wing mod thread

http://www.avidfoxfl...-modifications/

[SuberAvid 617]

Randy, Congrats on your new bird! Now your gonna have trouble going back to your cramped cockpit on the MK IV unless you do some mods!

If you are planning on using your old fuse, did you end up with an extra set of MK IV incowl radiators? If so, and if you would like to get a lil money back on your purchase would you consider selling either the new or old ones??

1. I am thinking of adding wing tip and flaperon extentions to the wings. The stock wing length gives me about 30.5' wingspan. I think the KF's are around 32' or 34' . Do these seem to perform better on short takeoff and heavier loads? Any opinions on what would be the optimum wing length to shoot for with my heavier Avid+ (1320 Gross)?

Yes, the kitfoxes I have flown I can get in and out shorter and fly slower. That extra 3' makes a pretty big difference! I would be very tempted to build a set of Catalina wings for your Suberavid!! If Bob would have put bigger tanks in his wings, I would have already made a midnight run on his shop and had them bolted onto mine!

2. Is it worthwhile to extend the flaperons with the wing?

The extended speed wing that I flew just moved the flaperons out and used a tube to extend them on the inboard side. Roll was lighter than quicker than my full length flaperons and I could get it in and out just as short as my HH wing. Stall was a non event just like we are used to.

3. Thinking of changing the washout from 2" to 1". What do the KF's have for washout and does anyone know what the stall is like with washout at the 1" range?

I thought about that when I rebuild my wings and I am kicking myself in the butt for not doing it. I think the latest KF has 3/4" washout. I would love to get that extra inch out of mine right now!

4. Plan to change the lift struts to 1" tubing. What wall thickness are the stock 7/8" lift struts? Leni, when you did this did you build whole new ones or just cut the 7/8 tube at the ends and plug it into the 1" tube and weld it up? What wall thickness did you use on the 1"?

I used 1" X .058" tubes for my new strut tubes. Yes, I cut my old struts off and just slid them inside the tubes and welded them up.

6. The speed wing uses an aluminum leading edge to smooth out the rib valleys. I know a supercup driver who told me this make a huge difference on a cub. Has anyone done this on their Avid/KF and does it seem to perform better.

I have the aluminum leading edges on mine. They were beat up a bit and Steve Winder tried to talk me out of fixing them and told me to just take them off. I liked the smoother look and I too have flown cubs with and with out the smooth leading edge. I left mine on there and repaired the sections that I needed to. What ever the difference, the kitfox still kicks my butt in slow flight and getting off shorter. I can get in just as short, but take a bit more to get off the ground.

Bob used the new plastic leading edge cuff from KF on all his KF wings when he rebuilt them.

Edit: Added the link to Dougs wing mod thread

http://www.avidfoxfl...-modifications/

This is a great help, Thanks Leni. As far as the radiators; I really don't know what I have yet; it is bought sight unseen except by Jack. I don't think it has any FW forward though except possibly the cowling. Will know more when we go to get it after I get back from the lower 48 in a couple of weeks.

[dholly 718]

Way to go Randy! Personally I agree with the 'one for land, one for sea' philosophy so... no question, no hesitation... I vote !

If you search up 'MTOW modifications' in the Avid+ forum, it should have the stiffener info and lotsa other good stuff. Just ask if you have any question not answered and I'll see if I have more info in my R&D files.

I too wanted to add a bit of wingspan to my standard length Avid wings, but not too keen on all the work involved for another 18" per side. I just sourced a used set of Kitfox 4-7 Hoerner tips. They are about 14" wide and I liked that I could easily make them removable vs. the standard fixed tips. In my case though (I built with the long spar to HH spec but substituted speed for HH ribs), I am shooting for (hopefully) most of the best of both Avid wing worlds vs. max STOL capability. I built both Mk-V and Avid+ wings with 1-1/2" twist vs. 2" per the manual and, knowing what I know now, wish I used less. I would not hesitate to use 1-1/4" or even 1" washout. IIRC, both my KF3 and KF 4-1200 use only 1/2" twist.

With 582's on front, my KF3 got off the ground a lot faster than my Avid Mk-IV. Climbed better too but I'm sure it had as much to do with empty weight as airfoil or wing length. I do, however, think the new Riblett airfoil on the KiIfox 4-7 is superior overall to both the KF1-3 and Avid HH airfoils. Just as much (arguably, even more) lift, and with less under camber, so you don't hit the typical Avid HH aerodynamic 'wall' at 90-100mph or so. I believe a KF 4 will easily out cruise an Avid HH by 15-20mph, and with less rpm and gas obviously. As Charlie Sheen would say, "Winning!". I were in your shoes with an unstarted Avid kit, I would be tempted to retrofit the Kitfox mixer into the Mk-IV and use Kitfox 4-7 ribs and flaperons. I think that airfoil, even on the std Avid length spar (basically one bay less than KF) would be great and would likely give performance very close to a KF and equal to or better than an extended Avid wing with HH ribs and short flaperons. The f/r spar carry through tube bushings distance of 27-1/2" is the same on both planes and, since you are likely going to make new lift struts, no real added work there. Keep in mind too, when I fold the wings on my Avid vs. KF, the KF is quite a bit longer (ie., harder to fit into a garage) and the ass end quite a bit heavier (ie., harder to wrestle around), should that be an issue for you (or resale). Of course, the leading edge cuff will add width in the wings folder configuation, so if you intend to transport in an enclosed trailer this might be a consideration. I can not fit my Avid+ w/ cuff inside a [legal width] trailer, and there was only about 1/2" clearance on each side of my KF4 w/cuff when the prior owner delivered it in his $20k custom trailer with full width rear door. It wasn't enough, see my "First fabric repair" thread, lol.

In any event, the leading edge cuff extrusion was an integral part of Harry Riblett's new KF airfoil. That wing chord is longer and necessitated the portion forward of the leading edge spar which, up to then, was used as the wing leading edge for all KF and Avid airfoils. KF and Airdale are the only sources I've ever heard of. There are differing reports of exactly how much, if any, STOL or stall benefit is gained from adding the cuff to the Avid airfoils. Seems like the speed wing benefits more overall than the HH, and the HH benefits most from a reduction in stall speed rather than an increase in STOL capability. I'm not sure anyone can say they definitely are worth the building time or weight penalty. Personally I think I would just add VG's to a HH wing (and under HS) and leave the cuff off. I did not add the cuff to my Mk-IV HH wings, but did add it to my Avid+ long speed wings. I did it primarily to sharpen my speed wing LE (like most aerodynamic mods, maybe help increase cruise?) and cover up the butt-ugly lift strut bracket and rivets from showing under the fabric. Never liked that aesthetically. Regarding the aluminum sheeting to prevent oil canning, I am seriously considering using thin marine ply instead. Joanne Heckman did that on her Avid and not only does it look great, it will not permanently dent like aluminum if it gets dinged. She used one thin layer of PolyFiber polyester padding over the ply and also the wing tanks, for both chaff protection and to avoid having to Bondo, Super-Fil and sand the f/g wrapping around the tanks smooth. Huge time-saver, that job sucks!

Have fun!

Edited 27 Apr 2012 by dholly

[EDMO 1078]

Good suggestion Doug, regarding the thin plywood. I wanted to add an aluminum sheet under my extended LE, but was concerned about dents, heat expansion, gluing to wood ribs, etc. I am only going to add the plywood from new LE back to spar, to save weight, and probably will add VGs under the wing after flight tests.

Happy Birthday to you and C5.

Ed in MO

Edited 28 Apr 2012 by Ed In Missouri

[EDMO 1078]

Doug,

My design book says that if you angle those Hoerner tips in at about six degrees from back to front, with the trailing edge being the longest, you will cut your drag. But it did not say how much.

I plan to install mine that way, so I wont have any comparison on cruise speeds for that mod.

One degree = about .017 per inch, so you can figure out the measurements.

Dont know anything about the engineering where they put the extra rivets in the Magnum strut attachments, but put them on mine, figuring that "more must be better".

Ed in MO

Edited 28 Apr 2012 by Ed In Missouri

[SuberAvid 617]

Thanks for all the info everyone, it leaves me a lot of options. The KF ribs sound tempting but will have to see what the cost is. Would they require using the KF flaperon or could I use the Avid flaperon with them?

I am definately thinking of the horner style tips that are a little longer. I know Brett has them as well; not sure if they are the same as the KF ones. Will have to check prices on those as well.

Leni, how did you form the leading edge aluminum sheet on yours and what thickness did you use?

[EDMO 1078]

Does anyone (Doug?) know or can find out what thickness Joanne Heckman used for the leading edge covering?

Anyone have recommendations? I was wondering if 1/16 would be thick enough. Now thinking about top and bottom for platform to attach VGs.

Ed in MO

[dholly 718]

Does anyone (Doug?) know or can find out what thickness Joanne Heckman used for the leading edge covering?

Anyone have recommendations? I was wondering if 1/16 would be thick enough. Now thinking about top and bottom for platform to attach VGs.

Ed in MO

Ed - it was 1/32 inch birch plywood. Thanks anyways but too late on the tips, holes are already drilled.

Edited 30 Apr 2012 by dholly

[dholly 718]

Thanks for all the info everyone, it leaves me a lot of options. The KF ribs sound tempting but will have to see what the cost is. Would they require using the KF flaperon or could I use the Avid flaperon with them?

I am definately thinking of the horner style tips that are a little longer. I know Brett has them as well; not sure if they are the same as the KF ones. Will have to check prices on those as well.

Leni, how did you form the leading edge aluminum sheet on yours and what thickness did you use?

Yes, you will need the KF flaperons. There is a set of KF 4-1050 wings for sale on Barnstormers right now for $2500, which I assume includes flaperons and maybe even lift struts. If the Hoerner tips from Airdale are the ones used on the Magnum wing, they are still fixed tips like on the other Avid Flyer model wings. That's one reason why I went to the KF 4-7 Speedster tips, the other being that that KF 4-7 rib profile was very close to the Avid Speed rib profile. If you use Avid HH ribs, I'm not sure how well (if at all) the KF 4-7 tips would work. You would need to source KF 1-3 tips, as that rib profile is almost dead nuts on to the Avid HH rib profile.

[EDMO 1078]

Ed - it was 1/32 inch birch plywood. Thanks anyways but too late on the tips, holes are already drilled.

Thanks for the info Doug. I will use something similiar. Probably 12 inches on top and 6 inches on bottom of L$E estension.

Maybe someday, someone will try modifying the Hoerner tips, and give us a report.

QUESTION for anyone: I used T-88 when I built my ribs, then 9460 to glue them to the spars. Should I use T-88 to glue the plywood to the ribs, or the 9460 that I will use to glue the new rib extensions to the new 1 1/4 inch aluminum tube leading edge?

I have estimated that my cost will be about $300 for the new leading edge extensions, including a new can of 9460, and can add another $250 for the plywood. Still cheaper than the 16 inch stretch, and don't have to re-engineer everything from firewall back.

Any thoughts are welcomed.

ED in MO

Correction: My LE plywood will only be $125. I misfigured price from Spruce.

Edited 1 May 2012 by Ed In Missouri