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Old Aug 21, 2007, 11:08 PM
Heli's don't fly voluntarily
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United States, TN, Columbia
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Quote:
Originally Posted by elight50
I can't seem to find the 42'' BB with the KFM wing marked on the drawings. Assistance appreciated.

elight50
Use the regular 42" wing plan to cut the bottom section. Cut the plan in half for the top of the KF wing. Use a 3/8" spar! 2" Ailerons.

That's the wing I have in the videos, except I removed the rounded outer portion of the wing and added the wing caps. Actually = a 40" wing that way.
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Old Aug 22, 2007, 01:05 AM
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Arlington,Texas
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That's what I did. I think I'm going to add the wing caps later when I put the ailerons on. I have a couple of newbies I getting used to R/E first.
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Old Aug 22, 2007, 04:24 AM
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Carmichael, CA
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kaos, i must be confused on kfm jargon. is the "7-9% step rule" defined as the total thickness at the step or the height of just the step?

if it's total thickness then the spar should be 0.20-0.40" (and a 3/8" spar would form an 8.8% step). if it's the height of the step then the spar should be 0.45-0.65" (& a 3/8" spar would yield a 6.3% step). that's how i got ~1/2".

kev
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Old Aug 22, 2007, 12:57 PM
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I am considering building a 42" KF wing without ailerons. Alternatively, I could modify my 33 to a accommodate a KF wing. Without alierons, what differences will I see in the way the plane flies with the KF wing over the std wing? Also, without ailerons, is dihedral recommended?

Flying the BB is certainly fun. Fiddling with it is what you do between flights.
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Old Aug 22, 2007, 02:46 PM
Heli's don't fly voluntarily
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United States, TN, Columbia
Joined Apr 2007
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Quote:
Originally Posted by Truglodite
kaos, i must be confused on kfm jargon. is the "7-9% step rule" defined as the total thickness at the step or the height of just the step?

if it's total thickness then the spar should be 0.20-0.40" (and a 3/8" spar would form an 8.8% step). if it's the height of the step then the spar should be 0.45-0.65" (& a 3/8" spar would yield a 6.3% step). that's how i got ~1/2".

kev
It's the percentage of the TOTAL THICKNESS of the wing relative to the wing chord. In other words, it's the step height relative to the total thickness of the airfoil, not just to the top side of the wing bottom stock. Download the spreadsheet that Flynfrog put together for KF configuration. I posted a copy in my Regal thread. You'll be able to see how it works. The spreadsheet has been pretty well accepted as the correct method for making the KF calculations by those participating the the Kline-Fogelman Flying Wing thread. Since the 7% - 9% range has been accepted as optimum, it's important to understand the basis for calculating that 7% - 9%. The spreadsheet makes it simple!
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Old Aug 22, 2007, 02:59 PM
Heli's don't fly voluntarily
Kaos2's Avatar
United States, TN, Columbia
Joined Apr 2007
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Quote:
Originally Posted by elight50
I am considering building a 42" KF wing without ailerons. Alternatively, I could modify my 33 to a accommodate a KF wing. Without alierons, what differences will I see in the way the plane flies with the KF wing over the std wing? Also, without ailerons, is dihedral recommended?

Flying the BB is certainly fun. Fiddling with it is what you do between flights.
Can you build a 33" version without ailerons? Yes, if you use at least 1" dihedral on each wing tip. The dihedral is MANDATORY to make the rudder induce bank for turns.

As far as flight differences go, I'll reserve comment. I will say that I like the KF wing for foamie planes, and I think you'll get better wind penetration, as well as other slight differences (i.e. inverted flight is now an option with KF).

I'm in the process of building an experimental plane that will allow me to test various versions of the KF wing, as well as other airfoils, on the same exact airplane. When my tests are complete in a few months, I'll be able to tell you exactly what flight differences to expect.
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Old Aug 22, 2007, 05:14 PM
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thanks for the info kaos, spreadsheet dled. i'm curious to see how your kfm vs XXX testing turns out. it would be nice to have a windtunnel & DA eh? i'm so desperate for ae work that i'm considering making a laminar tunnel with some leaf blowers, lol.

elight50, i don't want to diminish the importance of what the kfm crowd is doing atm, but there is "old school" theory you can reference for now. in post #574 of this thread osbornmj posted some xfoil results for the kfm airfoils. it's no cfd analysis, but gives a decent prediction of the differences between the kfm & 4-40. the kfm doesn't provide as much raw lifting power (l/d), but the stall characteristics are much milder (lift produced at a range of aoa past max cl).

in a nut shell the kfm wing doesn't technically perform as well, but is much easier to fly within it's performance envelope. another way to look at it is the 4-40 is awesome, but it requires pretty good thumbs to keep it where it performs well. whereas kfm can make a numb thumb can make look like a pro.

these results don't work for inverted though; uc wings won't fly inverted & fkm will.

kev
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Last edited by Truglodite; Aug 22, 2007 at 05:25 PM.
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Old Aug 23, 2007, 01:15 PM
John 3:16
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My son and I will begin cutting foam tonight for his Blu Baby. I think I will start cutting foam for Tony's SE5a after hours each night. We should finish our builds about the same time. We hope to maiden our new planes on Saturday. Here is the link to the SE5a for those of you who haven't seen it yet: http://www.rcgroups.com/forums/showthread.php?t=649178 . Now I just need to come up with a good color scheme for the SE5a (my son has already chosen his). Thanks, Tony, for the great plans.
Daddy-O
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Old Aug 23, 2007, 05:11 PM
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Quote:
Originally Posted by Truglodite
i never had that problem with my original bb. then again, it never had a battery hatch. i admit, your table tennis ball idea looks better.

when ppl ask me why it's blue i tell them it's a spy plane & sky blue is harder to spot. j/k nobody has even asked me about colors or materials yet; they just ask "what's the wingspan?".

please post pics when you're done painting. i'd like to see it.

Well, here are the pics. I am still a newb with it comes to airbrushing and I was lazy with this plane (didn't tape anything off).

I couldn't think of what decals to put on this plane. I build signs so I can cut anything out of vinyl that I want. The only thing I could think of was the Flying Spaghetti Monster symbol.
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Old Aug 23, 2007, 06:04 PM
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MacBeth, SC
Joined Aug 2007
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Hey Folks,

Wanted to post an intro and apoligize in advance for all the silly
questions that are undoubted coming.

I'm 62, retired, have a couple of cleared acres in back to
fly in. Just gotta watch out where ya walk/land. *LOL*

About a decade and a half ago I was active in RC gliders. Nothing
since until a couple of weeks back when I found an Aero Ace at
Walmart. What a hoot the little thing is. Now I want to get an
aileron trainer and from what I read here, the BB is a most versatile
and practical trainer.

My goal is to get where I can build and fly a foam IFO and/or one of the
3d stunt foamies. Not necessarily with the competence I see in the
videos, but never the less, low and slow and hopefully multiple flights
before building another.

I still have my Futaba Conquest FM 4 channel radio. I assume I'll need
to purchase a lighter receiver and micro servo's to go with. As well as
all the electrics to add motivation to my project. I know from reading
many excerts on this site over the last week that there is tons of info
in here. Is there a search engine on the site or does one just keep
digging until you find it? I am very impressed with the competence of
builders/designers on this site. Looking forward to learning enough to
become a contributor. Warm regards, Jim
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Old Aug 23, 2007, 06:18 PM
John 3:16
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Jim,
Welcome to rcgroups. There is a ton of information here, and the people are great! There is a search feature on the top right of the screen. It is right under the advertisment and the 'Welcome Jim Hatch' box. Not only is there a search engine here, but if you go to www.rcgroups.com main page, you will see that the site is divided into sections according to interest. You can also get that list at the bottom right of the screen under 'forum jump'. If you click on the down arrow that looks like a 'v' next to 'Foamies (Scratchbuilt)' you will find a list to all of the forums. I hope that gets you started. Enjoy yourself. There is a ton of information on here. Be sure to ask if you have any questions, as most everyone is very helpful.
Daddy-O
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Old Aug 26, 2007, 02:26 AM
John 3:16
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My son and I are running a little behind on our Blu-Baby. Because of his homework and other family activities, we weren't able to begin this project until today. The good news is that everything is cut out and just waiting to go together. My son is 11 years old. He did a pretty good job cutting out the plans and several pieces, but his younger brothers called him away to help save the world on the Nintedo WII. When he left, I finished another plane I was working on. We finished cutting parts (or I did) tonight.
I have an Important Question though: Should we put the KFm step on our little Baby? It is cut out, but I don't know if it will help the flight characteristics of a 3.25" dihedral RET plane. So to those of you who have done it.....Does it noticably help or not? We will start putting this together tomorrow, then get to paint it. My son is pretty excited about it! Thanks Tony!
Daddy-O
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Old Aug 26, 2007, 02:40 AM
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If it is a flat wing right now, absolutely put the step in. If you did an undercamber wing, leave it like that(as designed). The undercamber will be better for a rudder/elevate type of a plane. The only problem with it is that it does not fly inverted well(at all?). Since it is rudder/elevator, there is no need or possibility for inverted flight.
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Old Aug 26, 2007, 02:50 AM
John 3:16
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Kurpal, thanks for the info. I was getting ready to shut this thing down when I saw your post. I haven't yet put the undercamber in it, but I was planning to tomorrow afternoon. I'm not worried about this one flying inverted since it is my son's plane, and he is basically a beginner. He can fly, and likes to do loops, but I don't think he cares about flying inverted (maybe I should ask him though). Great advice! Thanks!
Daddy-O
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Old Aug 26, 2007, 08:28 AM
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Joined Feb 2007
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Kfm plan scaling

Tony, thanks for the plans and the priceless info, sorry for the question if has been asked before, I am trying to print the 42" BB and will print the KFm sport wing with it, I have two problems
1. as I print the plans without scaling, I get missing margins in the A4 paper as my HP laserjet 5 has only A4
2. the KFm plans are for the 33" and when I use the measuring tool of the acrobat to try to figure out what precentage to upscale the drawings to get the KFm to work on the 42", I find the half wing to be 13.70" so what to do, thanks

Khaled
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