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Nov 03, 2010, 04:01 PM
Registered FFF Addict
larryross's Avatar
I am building a 40" wing for an Icon-a5. I decided I wanted a little dihedral and a KFM-3 to make the wing a little stronger. Oh ya I am using $tree foam board. When I cut the KFM pieces I cut them 40% and 75% instead of 50% and 75%... can anyone tell me if that will seriously affect the KFM characterise? Should I re-cut the 40% to 50%?
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Nov 03, 2010, 04:22 PM
High Altitude Flyer
viking60's Avatar
Larry,

I'll suggest that, if possible, you try flying it with the primary step at 40% first, then temporarily tape in a filler piece to extend the primary step back to 48% to 50 %, and observe the difference it makes. Your observations should be of interest to many here.

I just looked at the aircraft you're talking about; you'll want to make sure that the step panels taper in chord toward the tapered wing tips, and also taper in thickness... too much step panel thickness out at the wing tips can result in excess drag on some designs. Especially watch the secondary step if it approaches close to the aileron hinge lines; a 6mm deep secondary step should be kept at least 3 to 4 times that distance from the hinge line. (A lower profile secondary step can be placed closer to the hinge line without degrading the aileron response when deflected.)

Hope these quick suggestions help!

VIKING
Last edited by viking60; Nov 03, 2010 at 04:33 PM.
Nov 03, 2010, 04:52 PM
Registered FFF Addict
larryross's Avatar
Thanks for the quick response. The 75% second step comes right at the hinge line, if I go back then it won't be 75% anymore. What if I sand the step to nothing directly in front of the aileron?
Nobody has any idea what a 40% upper step will do to the KFM-3? Think I'll go with the 40% and if it is undesirable then I can add a narrow strip.
Yes I did make narrower steps at the wing tips and will sand them thinner closer to the tips.

Quote:
Originally Posted by viking60
Larry,

I'll suggest that, if possible, you try flying it with the primary step at 40% first, then temporarily tape in a filler piece to extend the primary step back to 48% to 50 %, and observe the difference it makes. Your observations should be of interest to many here.

I just looked at the aircraft you're talking about; you'll want to make sure that the step panels taper in chord toward the tapered wing tips, and also taper in thickness... too much step panel thickness out at the wing tips can result in excess drag on some designs. Especially watch the secondary step if it approaches close to the aileron hinge lines; a 6mm deep secondary step should be kept at least 3 to 4 times that distance from the hinge line. (A lower profile secondary step can be placed closer to the hinge line without degrading the aileron response when deflected.)

Hope these quick suggestions help!

VIKING
Nov 04, 2010, 07:38 AM
High Altitude Flyer
viking60's Avatar
Larry,

I did try a 40% step on the first of the KF3P DANCER III glider wing builds as a test, with a secondary step at 70%; after test flying it & not being happy with how it flew, I added a narrow strip to take the primary step back to 48%. All of the details, photos, & flight evaluations are now compiled in the DANCER thread, (and a lot of info was posted in this thread earlier too), so there's no need to rewrite too much of it here & now- it's all there. These are the best-performing KFm3 variant wings I've built to date. This series of experimental wing builds starts on post 26 on page 2 of this thread:

https://www.rcgroups.com/forums/show...=860461&page=2

You may find some information there which could be applied to your A-5 wing build.

VIKING
Nov 04, 2010, 09:24 AM
High Altitude Flyer
viking60's Avatar

Having room to fly


Steve,

You commented: " My short grass area is very small (10m x 15m up against the tree line) and needs on-shore wind or no wind to make a good approach. "

Trying to do test flying of new aircraft in a small area certainly can be rough! While I fly some of my aircraft off the ~20 foot wide dirt road just off the end of my driveway, I am blessed to have a great wide-open flying site about three miles from our home. This is where I've been doing the flight evaluations of my latest KF3P wings, and where I do a lot of my flying. Here's one look at it.

This is natural short-grass prairie, where I've removed close to half a ton of protruding surface rocks to end up with a fairly good 'aerodrome style' takeoff / landing area that's mowed out about 30 yards by 50 yards right now, with the longer east-west runway section having a mowed area 50 feet wide by 75 yards long. There are no tall obstacles for quite a distance in any direction (other than my vehicle, bag chair, & wind streamer when I'm there) so I can take off and land in any direction, depending upon the winds on any given day.

I've mowed the taller grasses, so it's ready to have a nice smooth snow surface to fly from when the next snow falls. Ground surface is not really 'smooth'... 3" & larger wheels do fine, but it's still challenging for small foamies with only ~2" wheels. I'll have to do more grooming of a small area for the small wheel planes.

It is a superb area for flying E-powered gliders, hunting thermals across a really awesome expanse of sky in all directions. How far away can you see your aircraft? That's the only limit on the flyable airspace, 360 degrees. This somewhat groomed short grass prairie landing area is fine for glider landing purposes. And there's plenty of area for takeoffs & landings of some of my larger aircraft on wheels, as well as with skis or floats once the snow covers the ground.

If any of you are in the South Park area, you're certainly welcome to drop on by and use this flying site!

VIKING
Last edited by viking60; Nov 04, 2010 at 09:34 AM.
Nov 04, 2010, 10:20 AM
just Some Useless Geek
Yes, Bruce, you have a near-perfect flying facility. And as we've discussed before, you suck. [ahem]
Nov 04, 2010, 10:21 AM
Registered User
davereap's Avatar
Heres my latest KFm4 it is a blend of a UFO wing and a F3P body.. 26" diameter.. 16-18oz AUW ...4.3-4.8 oz sqft.. I am using my usual 150W motor, 800 or 1300 3cell lipo and 9x5 prop ..this gives me a max of 26oz thrust at 15A
Nov 04, 2010, 10:35 AM
High Altitude Flyer
viking60's Avatar
Quote:
Originally Posted by A Useless Geek
Yes, Bruce, you have a near-perfect flying facility. And as we've discussed before, you suck. [ahem]
OK Geek, that's it, you're banned... (unless you bring your pick & shovel & help out with the site grooming! There are still a few rocks to relocate.) Everyone else is still welcome!

~~~~~~~~~~~~~~~~~~

Dave, the disc wing with the large vertical surface area fuselage looks interesting. Will it knife-edge easily? How is it in slow flight & high alpha?


VIKING
Nov 04, 2010, 12:10 PM
Registered User
davereap's Avatar
Its just finished today and is waiting to be maidened...
I am hopefull about the knife edging, but its not a standard wing shape, and I know that deltas dont knife edge very well, so this might be similar..
Ive flown a much lighter version, which is highly aerobatic, slow or fast, but conditions here are too windy for it to be evaluated properly.. .. Hopefully the bigger one will cope better
I will get a video as soon as I can, but the weather forecast here is poor for a while..with a posible chance saturday if it doesnt rain
Last edited by davereap; Nov 04, 2010 at 12:16 PM.
Nov 04, 2010, 10:08 PM
Registered FFF Addict
larryross's Avatar
I hadn't glued the top piece in so I went ahead and re-cut a new one at 50%. While gluing it on the piece moved at the tip so I have more like a 40 75 at the wing tip... wonder what that will do. I did the other side to match and will see. I sanded the front to a curve to make for less resistance.

Quote:
Originally Posted by viking60
Larry,

I did try a 40% step on the first of the KF3P DANCER III glider wing builds as a test, with a secondary step at 70%; after test flying it & not being happy with how it flew, I added a narrow strip to take the primary step back to 48%. All of the details, photos, & flight evaluations are now compiled in the DANCER thread, (and a lot of info was posted in this thread earlier too), so there's no need to rewrite too much of it here & now- it's all there. These are the best-performing KFm3 variant wings I've built to date. This series of experimental wing builds starts on post 26 on page 2 of this thread:

https://www.rcgroups.com/forums/show...=860461&page=2

You may find some information there which could be applied to your A-5 wing build.

VIKING
Nov 05, 2010, 11:44 AM
High Altitude Flyer
viking60's Avatar
Larry,

I like using ~50% at the center of the wing, and ~40% out at the wing tips- especially on a tapered wing like you are building. If your secondary step at 75% of chord at the wing tips is thinned down well, it may work fine.

We may have fresh snow early next week to fly from... I'll be interested to hear how your A5 works out!

VIKING
Nov 06, 2010, 07:10 AM
Registered User
davereap's Avatar
Ive just maidened my 26" KFm4 version post 1522 with the blended circular wing and F3P body shape..
As usuall its blowing here but this bigger heavier version went superbly. Its another keeper
I have taken some video so I will process it to youtube a.s.a.p and then put it here
.
Blended circle maiden.UFO+F3P body shape (7 min 0 sec)
Last edited by davereap; Nov 06, 2010 at 10:33 AM.
Nov 06, 2010, 10:45 AM
Registered User
davereap's Avatar
I thought I would post this KFm4 from rcfoam fighters
.
KFm-4 airfoil on my scratch built FF-21 "BlackJack" park jet (3 min 50 sec)
Nov 06, 2010, 06:31 PM
Onward through the fog.
Cybernaught's Avatar

Nice short session this morning.


Dave, I tried to download your vid and only got 2 meg before my provider hiccupped. What I got shows it flies well. Good luck with the Knife-Edge efforts.

Larry, How is your build coming? do you have the notch placement figured out yet? Good luck the KF wings are a godsend to those of us who enjoy a simpler approach to this insanity.

Got the SOB up for two flights this morning. I have a lot of work to do on getting the trim right. The Taube with the big battery and the BP21 has plenty of power but the airframe is too small. My BW drive train is only about 60W. Nice for the Mini-Slinger and the Smaller deltas but I really like the Taube and it's time for about a 44" version. I plan on a full house with a touch of dihedral and a touch of positive incidence. The tail will be the earlier type that Etrich used on the 1910 version. Not to true scale but it should have a nice early aviator pre-WWI flavor to it. The Taube 35" hit a fence at speed and with the thing as nose heavy as it is with the bigger motor and batt, I"ll not be doing repairs.

Now it's time for a shower and then off to Tagbilaran for an SD memory adapter for Angel's new electronic game player thingie. Breakfast at Kentucky Fried Chicken and a movie. If we're back early enough I'll clean up the shop ready for the new build.

You all have a great weekend and get in some stick time.
Mabuhay and Happy-:Landings!

Steve.



Edit: 11/7/10 18:10:00
New gear mount maide from Popsicle sticks and bamboo skewers. held up to 2 rough landings and one good one before it got dark. Needs adjustments to elevator and ailerons for decent low power level flight.

Gear removed from old Taube. I may try a 24" to 30" span small Taube for the BW drive train to sort some things out then do the big one when I have it where I think I want it.

Last edited by Cybernaught; Nov 07, 2010 at 05:48 AM.
Nov 07, 2010, 12:10 PM
Registered User
Dickeroo's Avatar

Two Wing Nut KFm4 3D videos from Hermann Airport


I just came across these two videos of this plane which is flown by Jon and then by Tim. The weather conditions were not exactly ideal by it didn't appear to present a problem for this feisty aircraft.

Wing Nut KFm4 3D Foam board plane prototype (5 min 55 sec)


Tim Takes a turn on The Wing Nut KFm4 3D Foam board plane (8 min 20 sec)


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