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Old Nov 16, 2009, 05:25 PM
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Cybernaught's Avatar
Bohol Philippines
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Fellas,

Dave said:
"Joining wings at the centre always makes for the problem of reinforcing that weak spot in your build.. "

With the materials I use the center joint is just hot glued and taped on a KFm4 and if the chord is long, say 12" or more I use the same method on a KFm2. the reinforced tape gives all the strength I seem to need. With a high AR wing I use broom straws or bamboo skewers for a half-span I beam and it's just fine... Nice and light too.

Picture is my "Wallula" a 40" span by 14", 4sq ft, constant chord AP podded wing based on the Vesper design. There are no wing braces at all and it's target weight will be 20oz or less for power with a bp21 and 1300mah Lipo. Wing joint strength is good! Max thickness is just under 1.5" giving about 10.7% thickness.

The plan is to be able to carry a 100g camera on top with bracket just tapped on at CG for easy adjustment and removal. All gear to be internal and short-nosed pod below the wing only

Steve.
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Old Nov 16, 2009, 08:44 PM
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Dave,
You talked about moving the zigzag pattern, but didn't tell me how you thought it might perform. You know this was a KFm4 build and after I finished it, I felt the back 50% looked anemic. It reminded me of my foam FlatOuts and looked like it wouldn't be able to carry the weight.

After initial testing of the new KFm4, this is true at least with these three wing builds. The KFm4 came in last on lifting.

The triangles came from an idea that I was going to do on one of my Swept Wings as a test to see what might happen to the airflow over the KFm3 airfoil. Never did it because of time and having to deal with a bunch of small triangles for a wing with a 30 degree sweep, and large span. I may revisit that someday.

Anyway, let me know what you think would happen by moving the pattern forward.

Steve,
I know or at least I think your not a big fan of the KFm3 airfoil. I was wondering why you went with the KFm4 on the Wallula. With a constant chord KFm3, I would think you could to get some good lifting properties. Your wing is looking good.

Bill
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Old Nov 16, 2009, 11:43 PM
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Quote:
Originally Posted by wjsflywing View Post

Steve,
I know or at least I think your not a big fan of the KFm3 airfoil. I was wondering why you went with the KFm4 on the Wallula. With a constant chord KFm3, I would think you could to get some good lifting properties. Your wing is looking good.

Bill
Hi Bill,
BTW, I like what your doing with the zigzag. It looks good while I haven't had a good flight on my new Nifty yet I have a feeling it will be a good performer. Hope I'm right.

The 3 has been a bit sensitive to CG placement for me. Not sure why it just seems to be a lot trickier to set up right for good performance. It is also a touch more complicated to build though only slightly. I like the 2 and the 4 best, mainly for simplicity, and of those two, the KFm4 may have less lift but it's slower and stiffer, naturally, because it's thicker. I just figured slow is good for AP. I also want to be able to fly it as a fun ship without the camera. That's why I plan on having the top flush and the KFm4 is fully symmetrical which should be better for a little aerobatic performance.

That's all.

Steve.
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Old Nov 17, 2009, 05:31 AM
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Ashford. Kent. England
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Quote:
Originally Posted by wjsflywing View Post
Dave,
You talked about moving the zigzag pattern, but didn't tell me how you thought it might perform.
Anyway, let me know what you think would happen by moving the pattern forward.


Bill
I didnt mean that you should move it...since it is obviously working well, so leave it alone..
I just meant that we normaly use a step at the optimum 50% location on top for an improved glide...and the 40% on the bottom for ? stall/stability ? cant remember now... when our steps are located forward or backward from the "ideal" spot the best glide is slightly reduced.. So I would have assumed that by averaging the zigs and zags across the 50% line, that would have been their optimum position..
Most of our KFm4 builds use steps that are fixed at the same %ages top and bottom, and usually between 40-50%.. for ease of build, strength etc..all work well..even though one or other step is then slightly away from the optimum...when flying ,the wings all go well and we cant really notice the difference..
So personally I would leave a nice flying wing as it is, But the next time you need a new wing you could try a different location and/or smaller zig zags, or anything that takes your fancy.
Myself I fancy smaller zig zags with an open overhang like on my FB's eagle

lifting properties... you are correct... the KFm4 works as if it were a symetrical section ...KFm2 and 3 work as lifting sections.
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Old Nov 17, 2009, 11:28 AM
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Ilford,Essex, UK
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Hi All somthing a little different in KF

I thought you may like to have a look at a KF hydro based loosly on the Gemini
Fitted with a BP 21 and 8x6 sf I think the motor is a little underpowered at 21 oz rtf (best take out the car battery I suppose) I am going to order another motor from HC any suggestions?

It is almost complete however I am having real frustrating problems to get the staples packing tape to stay stuck on the blue foam.

The foam is not FF or depron I got it from the inside of a UPVC door off cuts and sliced in down, this tape is driving me nuts

I will post a video if it gets off the ground

BTW I have discovered a new way (to me anyway) to make very good hinges in foam start with the commom method of angling the edge of the control surfaces butt the edges almost together on a piece of masking tape then spread in some COPYDEX glue.

This glue is water based so you can clean up if you make a error but only before you let it cure.

This stuff is (I think) almost pure latex wipe of the excess with a shaped piece of wood leaving a thin film up the sides of your tapered cut and a thin bridge across the gap where the surfaces hinge after about half an hour take of the masking tape to let the air get at the " hidden glue" . When fully cured somtime the glue is still taky if so just run a permanant marker down the hinge.

The strenght of these hinges is amazing you realy have to pull very hard before they let go in the case of this foam the foam sheared first. I reset the hinges on my superfly and the glue works just as well on epp

Regards Jeff
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Old Nov 18, 2009, 04:23 PM
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Neenah, WI
Joined May 2006
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Hereís a spar arrangement that can increase the beam strength of a KFM airfoil. The foam is 1/4 inch thick and the spars are 1/4 x 1/4 inch. The total wing thickness is 3/4 inch. The objective was to place the wood spar along the upper-most and bottom-most regions of the airfoil shape. The shown spars are spruce, but Iíve used medium-weight balsa for lighter-weight structures. Gluing some carbon fiber strips along the top of the top-spar and the bottom of the bottom-spar can further increase the beam strength. The shown airfoil-shape is KFm3, but the spar arrangement is readily adaptable to the KFm1, KFm2, and KFm4 shapes as well.
In the photos, the distance between the end supports is 28 inches and the gallon jug of glow fuel weighs ~7 pounds (~3.2 kg). The structure does bow, but readily recovers its original shape.
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Old Nov 19, 2009, 08:58 PM
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Bohol Philippines
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Quote:
Originally Posted by Upup View Post

BTW I have discovered a new way (to me anyway) to make very good hinges in foam start with the commom method of angling the edge of the control surfaces butt the edges almost together on a piece of masking tape then spread in some COPYDEX glue.


Regards Jeff
Jeff.

I use hot glue the same way on both foam and taped over foam. just lay out a bead and use a putty knife to spread it. 1/4" to each side of the hinge line works well. I get the same results you get with your COPYDEX glue

Finally maidened the Nifty Zigzag. It was a bit hairy till I went to full throws on the dual rate. I got stuck in the wind and couldn't turn left.
NZZ Maiden 11 20 09am (1 min 40 sec)

Also had a short flight with the Pagan but rain interfered.
Pagan 11 20 09am (4 min 14 sec)


I'm not good at windy flying but I guess if you don't fly in the wind you don't fly at this time of year here in PI...

Steve.
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Old Nov 20, 2009, 03:53 AM
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CYBERNAUGHT WROTE

I use hot glue the same way on both foam and taped over foam. just lay out a bead and use a putty knife to spread it. 1/4" to each side of the hinge line works well. I get the same results you get with your COPYDEX glue

Hi Steve

I also have used the same method as yourself IE hot glue and it is very effective. However the copy dex hinges seem to move much more freely and are very "neat" but the real advantage, to me anway, is when I "Cock it up" a wet cloth is all I need to start again. I changed the "hotglue" hinges on my super fly and it is now more areobatic seems as though the servos have less work to do somehow

Do give it a try all I am doing is trying to pass on somthing which I believe is better,easier.

Regards Jeff
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Old Nov 20, 2009, 06:19 AM
Onward through the fog.
Cybernaught's Avatar
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Quote:
Originally Posted by Upup View Post
Do give it a try all I am doing is trying to pass on somthnig which I believe is better,easier.

Regards Jeff
I would love to but I don't think We have it here in the Philippines. I find once I move the hot glue hinges up and down a bit they loosen up and the trick is to use a thin layer of glue. They can be heated with a hair dryer and redone easily too.

I like quick and dirty!

Just a quick after-thought that pertains to my new Nifty ZZ maiden video: "Yelling at your plane when it doesn't respond to your control inputs doesn't help!" However onlookers do seem to find it quite amusing.
Steve.
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Old Nov 20, 2009, 08:33 AM
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Quote:
Originally Posted by Cybernaught View Post
I would love to but I don't think We have it here in the Philippines. I find once I move the hot glue hinges up and down a bit they loosen up and the trick is to use a thin layer of glue. They can be heated with a hair dryer and redone easily too.

I like quick and dirty!

Just a quick after-thought that pertains to my new Nifty ZZ maiden video: "Yelling at your plane when it doesn't respond to your control inputs doesn't help!" However onlookers do seem to find it quite amusing.
Steve.
Latex carpet glue ( I have since discovered) is very similar halls f2 is one

BTW I find yelling at planes very usful and effective particulary on take off

Hence my thread non de plume UP UP!!!!!

Regards Jeff
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Old Nov 20, 2009, 10:16 PM
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Cybernaught's Avatar
Bohol Philippines
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Nice session today.

Had a good time at the field today. The NiftyZZ flew very well and details are on the Nifty thread. I also got the original (RED) Vesper back in the air and it performed OK and was a fun ship to play with again. I got in about 40 minutes air time with most of it on the Nifty.

A fun morning. Wishing you all the same!

Steve.
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Old Nov 23, 2009, 07:27 AM
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Windsor, Canada, near Detroit
Joined Jul 2007
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a recap on KF?

Dear Sirs: Could it be possible to have a recap on KF airfoils about what we get from each one, how they compare, based on your experience:
1.- their relative speed, lift, stability;
2.- what % (thickness) is better for what type of flight;
3.-what is the difference bet a step over or under.
I think this will be of great help for newcomers to decide what to use.
Your input will be highly appreciated.
Phil
Jack: I just sent to you a message thanking you for the input in the next post (283) but somehow i think i sent it to the wrong address, so here it is again:
Thank you very much for all the input; it will save me lots of experimentation, even if sometimes you don't provide direct answers; your guess is highly appreciated. Thanks again. It's this kind of assistance that makes a forum so great. Phil
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Old Nov 23, 2009, 10:59 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Here is your recap, right where it has always been:

http://www.rcgroups.com/forums/showp...48&postcount=2

If we put it in one place and refer to that, it avoids have 16 different version with subtle variations spread all over the place. I am the moderator of this thread, I (with some help from others) can and do modify that post from time to time.

But there is not hard or conclusive data for these details:

"..1.- their relative speed, lift, stability;"

"..2.- what % (thickness) is better for what type of flight;"

"..3.-what is the difference bet a step over or under..."

There is not any hard or conclusive details that will answer all of those questions conclusively. Many different builds, many different builders, many different flight impressions collected by many different people and in many different conditions, and many different opinions.

If anyone can see trends or answers like that emerging in these threads and posts, give me a summary of the details and I'll put them in post #2 with the other details.

As always, read no anger or rejection into my reply here. This is just a polite recreational discussion of what I think it is.

Jack
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Old Nov 23, 2009, 01:42 PM
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Moving ahead on the Jupiter Project.

Here is the latest video of the Jupiter cargo plane, which will be testing the lifting capacity of the KFm2, KFm3 and Clark-Y airfoils. Paul has placed a camera on board this flight and it has a wide angle lens. The flight is very smooth and the camera work is terrific. To me, this RC aircraft flies and looks like the real thing... a full-scale aircraft.

Project Jupiter Part 6 (KFm3 RC Airplane) (9 min 57 sec)
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Old Nov 23, 2009, 04:51 PM
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Bohol Philippines
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Dick,

That's a video download for the Cybercafe speeds for me.

Here's the link to the Foamfighters' Jupiter:
http://rcfoamfighters.com/blog/?p=645

Thanks for the heads-up. Looks interesting.

BTW: All my builds use KF foils and I have no inclination to change that! They Rule!!!

Steve.



Edit: 11/27/09 9:41am
Decided to fly the Assassin 39. Here's a short vid you may get a kick out of. That thing is fast!
A0 CC1.wmv (0 min 29 sec)
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