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Old Dec 04, 2010, 03:57 PM
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Fairplay, South Park, CO
Joined Sep 2005
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Pat,

glad to hear that it's working out fairly well!!

I'm getting fond of building in wider ailerons these days... you can always program them down on travel, but the 1-1/4" width could be part of the slow roll, along with the large wing tip panels.

As far as trimming down the wing tip panels, that's an easy thing to do next! I'd recommend leaving close to ~9/16" on the under-side of the wing to maintain that bit of 'flying on rails' affect that they can contribute. Above the wing, you may also want to trim them to about the same, & fly it like that. You can next experiment with loosing some of the extension length behind the wing's trailing edge... I like what they do when extended about 1/4", but most ~conventional layout designs don't benefit from having them extend beyond that. (Based on lotsa experimenting over the last 20 years on a wide variety of aircraft...)

VIKING
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Old Dec 04, 2010, 04:39 PM
Onward through the fog.
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Bohol Philippines
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Nice looking plane, Pat.
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Old Dec 04, 2010, 06:51 PM
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Steve... I could not resist posting this picture for you. I was looking for some pictures and came across this. It just reminds me of some of those unique builds you do.

Do you think a KF foil would work on something like this?

Bill
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Old Dec 04, 2010, 07:54 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by wheelspinner20 View Post
Hello kfm peeps.

I flew my 33" blue baby today with a new kfm2 that I posted some pics on and asked some questions about.

It went well. Biggest change overall was trying a small 3s 1100mah hyperion battery. Keeping the 27-12-12 blue wonder in place with the 10amp esc. I went for the large prop listed 9x4.7sf gws, and put a 90%limit on trl in case I forgot.
Congrats, Pat! Good to hear you're getting some good stick time on that. Really good to hear you finished up with some nice flying and on a positive note.

The need for up elevator trim to get level flight implies that you're tail heavy. Pick it up and find the level spot on your finger tips and see where the CG is at. There are builds where things can combine to move the CG forward or aft so there can come a point where you just have to give up on that number on the plans and go with what works.

If you want to test it a little, move the battery forward 1/4" or so or tape a couple of washers on the nose for one flight and see if it feels better. .

Quote:
The other big difference is end plates. Probly added lift and stability, but, I think they inhibit roll. It would not roll with modest ail limits. I increased and best I could get was 1 rev of roll for 3 to 4 seconds...(careful to have alt. first.) The kf3 that i tried last week did not have endplates and rolled relatively quickly. the kfm3 was 32" and this kfm2 is 36" I suppose that could have effect on roll rate maybe, not sure. I'm open for suggestions on increasing roll. I think I will try to trim end plates down a little. They are 1.25 tall by the time they reach T.E. both top and bottom.
The end plates are to keep the air flowing straight back over the step and not spilling off of the ends. When Tony65x55 started adding those he said that making them even with the bottom of the wing or slightly below and the same height as the wing thickness above the wing was all that was needed. His were simple rectangles of foam with one end rounded. You can see them here in the full sized plan for the KFm3 Sport Wing. So if you wanted to cut yours down a little you probably wouldn't lose anything.

To be honest, I've been leaving the end plates off on the builds I do that have a straight leading edge (no sweep on the leading edges) and don't seem much difference. I've kind of come to think of them as more of an eye candy thing that I add later...

Quote:
Can someone give a brief definition and use of flaperons? And what does the basic formula look like when programing this mix.? I guess I could search it.
On my radio to use flaperons you have to have two aileron servos, the left servo goes on the AUX channel and the right on the Aileron channel, and you have to set the flaperons to on. And then the flaps on on a toggle switch. You program the amount of "droop" you want to get when the switch is flipped as a percentage of the servo travel and when the switch is flipped both ailerons droop down that amount. If you use the aileron when the flaps are down you still have some aileron control but it will be with less travel because some of the travel was used up for the flaps movement. Does that help? That was how it works on the JR 9106 TX.

Jack
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Old Dec 04, 2010, 08:10 PM
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Flaperons on Model Aircraft

This guy is good at explaining and giving examples.

http://www.airfieldmodels.com/inform...l_aircraft.htm
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Old Dec 04, 2010, 08:13 PM
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Good, thanks viking, I already trimmed them. They are about 1/2" top and bottom. Since I broke off one of the point tips l.e. I cut the other to match.

I increased the throw mechanically at the servo horns, and went down the street to the middle school for a quick test. It responds to ails better, but, I think it has a little nose up yaw on left turns again. But, it was really windy, 10 to 15mph, so it was difficult to get a good measure. High winds are forecast for the next week so I guess I have to wait. In the mean time, I will cut the arrow tails off of the side fences and look at some plans for my next build.

thanks cyber, It used to be new looking. We call it franky short for frankenstien, because it has been stichted back together from pieces and brought to life with mad- science-like care.!

P.
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Old Dec 05, 2010, 01:05 AM
Onward through the fog.
Cybernaught's Avatar
Bohol Philippines
Joined Aug 2008
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Flying Wings suitable for a KF airfoil.

Quote:
Originally Posted by sharpewing View Post
Steve... I could not resist posting this picture for you. I was looking for some pictures and came across this. It just reminds me of some of those unique builds you do.

Do you think a KF foil would work on something like this?

Bill
Bill that does look interesting. The high aspect ratio would make it a bit tricky though.
If you like "odd" wings then check this site out.

http://babelfish.yahoo.com/translate...rUrl=Translate

It's in German but I'm trying to post the site through Babel.

The AET bird is ready for a maiden attempt but it's windy now. 3:30pm Sunday. I'm calling it ABE for the moment. Aileron Bird Experimental. We'll see how this weird wing shape works out. The elevator pushrod assembly allows me to do all adjustments with one collar holding the 3 wires to both elevators and the servo horn. I use a single servo for the ailerons.
It's 2.33sq in area and weighs 12.9oz for a loading of about 5.5oz/sq ft. I'm balanced about 22% behind the leading edge average. that's a guess but I think I'm in the ball park. Throws are about 3/4". If the wind dies today I'll try it or if not tomorrow early.

Steve



Edit: 12/8/10 10:22am
Problems attempting maiden in the wind. Pop-Bottle elevator horns no good. Plastic twisted and Z bends slid through. Changed to popsicle sticks should be better. Wind/rain and can't test now.
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Old Dec 05, 2010, 10:53 PM
treefinder
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I would normally post this in the kfm science thread, but there's not much action there, so Here goes: I had to make a second wing for my PV2, a 30's racer based roughly on the Parkflyer Pete, with an aileron KFM2 wing. Original wing was getting pretty rough, and the aileron tape finally cracked. So, new kfm2 wing almost done. Looking at the original wing, it's not too bad, so what if I make it into a "conventional" airfoil to do a-b comparison of flight characteristics of sport planes. Here's the question: What "conventional" airfoil should I use? I checked out the ubiquitous Clark Y, and found some suggestions to shrink it vertically to reduce drag, so resized it in Sketchup to match the overall dimensions of the half inch thick 7" chord original KFM2 wing (if just sizing the Clark Y to 7" it would have been 13/16" thick! Plump!). What do you guys think is that the good conventional target? Here's a pdf of the two airfoils.
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Old Dec 05, 2010, 11:38 PM
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Joined Sep 2005
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At a 7" chord (low Reynolds Number) the Eppler E205 might be one to check out; It is one airfoil which I've built on a hand launch glider (The Larry Jolly "FLINGER" design) in the late '80s which performed very well in that size range. (The E205 airfoil is ~10.5% thick, with a higher camber line than the other two noted below; there's a thinner version designated as the E2052595 which looks better at 9.5% thick.)

[I still have my Flinger hanging on the ceiling of the shop... might have to haul it out & fly it again one day when the weather warms up. It was always one of those that did well in a variety of conditions, & handled some wind well, too. My 'STELLAR" HLG also used this airfoil on a turbulated wing structure (built with turbulator spars placed longitudinally on the forward half of the wing's top surface) & is one of the best light air & low speed 'floater' HLG gliders I ever built back in that era. Due to a shoulder issue, I'm not an aggressive glider chucker these days, but they are great to get out on a small slope in lighter lift.]

NOTE: the PROFILI software free version will allow you to print out this & many other airfoils at whatever chord size you want; I use it now & then.

http://www.profili2.com/eng/default.htm

The EPPLER E180 and E387 are two more thinner conventional airfoils that may possibly come closer to what you are looking for, with close to a flat bottom.

VIKING
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Old Dec 06, 2010, 06:40 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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"..What do you guys think is that the good conventional target?..."

No science here, just seat of the pants impressions. I don't know that plane at all But with a 7" chord and assuming a low winged racer kind of plane, I'd think the KFm3 or KFm4 would be a good choice.

The flat KFm3 can be built in a very light and strong all FFF build because of the way the layers overlap and give you lots of glue lines. I was pretty amazed at the strength of the flat 32" KFm3 I build recently. And it has a very snappy roll rate so it should do good in the pylon racer mode kind of flying.

A pair of 1/4" or so steps on a KFm3 would still keep you in a profile that is sort similar to the Clark Y, it would just have more and shorter steps.

The KFm4 does not lend itself to the staggered/layered strength thing and the Piranha-like full aerobatic advantage of that wing is less needed in the pylon racing (less inverted flight, no loops or full rolls, etc.).

It there a plan for that guy? I didn't bring one up in a search.

Jack
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Old Dec 06, 2010, 09:42 AM
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Steve... thanks for the web link! It would be interesting to see a KF build with a wing taper like that...

springer... if your build is based around a foam Parkflyer Pete, then using any of the KF airfoils should work. You also mentioned "sport plane", so if you plan on doing aerobatics or pulling high G's, you can add balsa, basswood, or even some carbon to stiffen the wing.

I like viking's suggestions on maybe trying the Eppler 180 or 205 as starters.

Try something other than a flat bottom airfoil and reduce your step height on your wing.

Have Fun!

Bill
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Old Dec 06, 2010, 04:54 PM
treefinder
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Viking: thanks for the eppler tips, and the link to Profili, I'd looked at the program before, but don't think I downloaded it. Will do now.

for the others, The plane currently has a KFM2 wing and flys perfectly for what I want to do with it, basic aerobatics and kicking around the pasture back of the house. I never did a build log for it, just posted in the Pete thread mostly, although here's a video link that shows it flying: http://www.rcgroups.com/forums/showt...den+age+racers
I only considered the idea of a conventional airfoil based on the ongoing discussion mostly in the Modeling science or Builders forums about lack of good comparison tests between KFM's and conventional airfoils. So looks like either a Clark Y flattened or an eppler if it looks like the squashed profile I posted earlier. I definitely don't want a fat airfoil, and not a flat bottomed one either. I've already done a 7035 airfoil for the One Sheet Glider to compare with the KFM2 I currently favor, but haven't had enough time on both to really understand differences. First impression is I like the KFM better, tho.
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Old Dec 06, 2010, 05:06 PM
Onward through the fog.
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Bohol Philippines
Joined Aug 2008
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What next?

My conventional planes are fine in low wind and I have my Mini-Slinger wing and my slotted delta for the windier days but I would like a dedicated windy day flier to add to the hangar.

Dave,
You have had some good results with your Superfly Clone, I think. I'm thinking another Delta like the FireFly. Perhaps with some minor cosmetic mods???

Any thoughts as to the best windy day flier?

Steve.
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Old Dec 06, 2010, 05:44 PM
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Fairplay, South Park, CO
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Quote:
Originally Posted by springer View Post
Viking: thanks for the eppler tips, and the link to Profili, I'd looked at the program before, but don't think I downloaded it. Will do now.

..." I definitely don't want a fat airfoil, and not a flat bottomed one either. I've already done a 7035 airfoil for the One Sheet Glider to compare with the KFM2 I currently favor, but haven't had enough time on both to really understand differences. First impression is I like the KFM better, tho.
Springer,

These are not really 'flat bottom' airfoils I'm mentioning; they do lend themselves fairly well to building from flat sheet foam, though. You get to do the shaping of the underside close to the leading edge, as well as to the upper surface.

Another fine one to consider is the RG14; it's thinner than the RG15, and is used on some aggressive flying hotliners and high speed slope ships. I used the RG14 airfoil profile as the starting profile for my early DANCER KFm2 variant wings with excellent results.

The KF3P wing builds are flying superbly; they are based on the MH32 airfoil. (The 'P' is for the aft top Panel which runs from the primary step back to where it ends in the low profile secondary step.)

VIKING
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Old Dec 06, 2010, 08:05 PM
treefinder
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yup, I understand, and like them for that. I've seen several folks suggest a "clark Y" and show a flat bottomed foil, and wondered if it were true; found out that their's wasn't really a Clark Y, just the "top half". If I'm going for shaped, might as well do both halves!
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