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Old Oct 05, 2009, 09:36 AM
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Quote:
Originally Posted by davereap
quote Flew the rebuilt FFF glider today. Much better than the EPP version. Glide was unbelievable. Thanks for all the input. Pics can be seen at the thumb wing thread.

a link please for us lazy people ...dave



Perhaps we should also post where not to stick a step...
When I said they mostly work, I meant with reasonable positions..A bit off here and there and the steps are still ok
I wouldnt for instance stick a KFm2 at 20% or 80% when the target location should be 50%.
Best always to be fairly accurate knowing what is required, but a bit moved here or there if needed is acceptable
I didnt post a link originally because I didnt want to detract from this thread with another. Here it is, post #60:
http://www.rcgroups.com/forums/showt...1113019&page=4

Interesting you said you wouldnt stick a step at 20% or 80%. I was thinking of trying one at 28% to somewhat mimick the flat bottom clark Y. Has it been done?
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Old Oct 05, 2009, 10:08 AM
just Some Useless Geek
Chicagoland
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Quote:
Originally Posted by jackerbes
...OK-C3542-A is the leading candidate for the SpadStik...

That is a seldom found out of production motor, there is little or no data around for it, and it came to me for about $15 (too cheap to not buy it) via eBay. It cries out to be used though as it bench tested very nicely. Pretty frightening with a APC 10 X 6 on it.
According to Nitro Planes, "Temporarily Sold Out!" As with everything they ever post on that crappy site. Those guys...

Take another look at the Turnigys on Hobby City. There's an incredible array of motors there for every application you can shake a stick at.
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Old Oct 05, 2009, 11:29 AM
Geaux Saints
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Grafton, Il
Joined Nov 2007
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Quote:
Originally Posted by j2m2t2
I didnt post a link originally because I didnt want to detract from this thread with another. Here it is, post #60:
http://www.rcgroups.com/forums/showt...1113019&page=4
What detraction?
That is part of what this thread is for.

This thread is not intended for an entire build thread but posting some pics, videos and links is fine.

Mike
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Old Oct 05, 2009, 12:29 PM
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Interesting you said you wouldnt stick a step at 20% or 80%. I was thinking of trying one at 28% to somewhat mimick the flat bottom clark Y. Has it been done?[/QUOTE]


The glide tests to determine the best position for the KFm2 were made with steps at various locations and the best result found was at 50%
Going back a long way this video was posted
.
KF stepped wing test glides (2 min 16 sec)
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Old Oct 05, 2009, 04:28 PM
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Quote:
Originally Posted by davereap
quote
Perhaps we should also post where not to stick a step...
When I said they mostly work, I meant with reasonable positions..A bit off here and there and the steps are still ok
I wouldnt for instance stick a KFm2 at 20% or 80% when the target location should be 50%.
Best always to be fairly accurate knowing what is required, but a bit moved here or there if needed is acceptable
How much does the thickness of the step affect things?

I was thinking of building a FFF version of VQ models VTO:http://www.vqmodel.com/MateriePrime/...es/VTO/VTO.htm
(or a UFO or Nutball) using either KFM2 or KFM4,
but for a 32" wing I would need 1.5 inch thick spar.
That seemed a bit excessive.
Obviously I could use cf as a spar and stiffener, and then just use the fff to fill in for the height I need, but I'm not sure I'd like the look of that big of a step.
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Old Oct 05, 2009, 04:59 PM
PunchDrunk ex-Pug try'n fly'n
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Quote:
Originally Posted by j2m2t2
I was thinking of trying one at 28% to somewhat mimick the flat bottom clark Y. Has it been done?
Yes I have played around allot with the step placement. At @ 28% you will get alot of nose up attitude. It would require a counter force either @70-80% on top or @28% on the bottom. That is if I am finnaly understanding the theory at last. Let us know
jp
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Old Oct 05, 2009, 05:05 PM
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Quote:
Originally Posted by davereap
Interesting you said you wouldnt stick a step at 20% or 80%. I was thinking of trying one at 28% to somewhat mimick the flat bottom clark Y. Has it been done?

The glide tests to determine the best position for the KFm2 were made with steps at various locations and the best result found was at 50%
Going back a long way this video was posted
... [/QUOTE]

Thanks for sharing the great work!
The vid' sure makes the 50% step KFm2 look like the winner. The flat plate appeared to have a tendency to go nose up and stall. I wonder if moving the CG slightly forward would have improved performance.

Where was the CG of each test set up?
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Old Oct 05, 2009, 06:23 PM
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Thanks for the vid davereap. I hadnt seen that yet.
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Old Oct 05, 2009, 06:24 PM
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Quote:
Originally Posted by jp.electrik
Yes I have played around allot with the step placement. At @ 28% you will get alot of nose up attitude. It would require a counter force either @70-80% on top or @28% on the bottom. That is if I am finnaly understanding the theory at last. Let us know
jp
Thanks. Ill let you know if or when I go down that road.
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Old Oct 05, 2009, 06:26 PM
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Quote:
Originally Posted by bz1mcr
The glide tests to determine the best position for the KFm2 were made with steps at various locations and the best result found was at 50%
Going back a long way this video was posted
...
Thanks for sharing the great work!
The vid' sure makes the 50% step KFm2 look like the winner. The flat plate appeared to have a tendency to go nose up and stall. I wonder if moving the CG slightly forward would have improved performance.

Where was the CG of each test set up?[/QUOTE]

That is exactly why I asked in a few posts back if the CG changed according to the step. My 9mm KF2 seemed to need the CG more forward than my FFF KF2 version of the same wing?
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Old Oct 05, 2009, 06:36 PM
Onward through the fog.
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Quote:
Originally Posted by davereap
Interesting you said you wouldnt stick a step at 20% or 80%. I was thinking of trying one at 28% to somewhat mimick the flat bottom clark Y. Has it been done?

The glide tests to determine the best position for the KFm2 were made with steps at various locations and the best result found was at 50%
Going back a long way this video was posted.
Your tests are pretty conclusive and add more insight to the KFm2 performance envelope.

I am using a 50% KFm2 for both wings on my new canard, The Pangangan Island Goose. (PIG) I hope the elevator isn't too close to the step on the front wing. We'll try it and see. When the main wing is finished, sans color, I'll add about 5" to the fuse length. Probably go with some kind of skids instead of LG. Problem is keeping the fuselage light while making it strong. BP21 and 8x4 or 8x6 prop on 3s to power it. WOT around 200 watts. Hope to fly it mostly under 1/2 throttle. We'll see...

This should be interesting.
KF wings rule!

Steve.
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Old Oct 05, 2009, 06:45 PM
Geaux Saints
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Quote:
Originally Posted by sdj544
How much does the thickness of the step affect things?

I was thinking of building a FFF version of VQ models VTO:http://www.vqmodel.com/MateriePrime/...es/VTO/VTO.htm
(or a UFO or Nutball) using either KFM2 or KFM4,
but for a 32" wing I would need 1.5 inch thick spar.
That seemed a bit excessive.
Obviously I could use cf as a spar and stiffener, and then just use the fff to fill in for the height I need, but I'm not sure I'd like the look of that big of a step.
I did a rough guess that wing chord is 24" with ailerons on the plane from the pictures.

Using 0.25" foam thickness at 8% came to 1.48".
Using 0.25 for foam thickness at 7% came to 1.18" spacer.

Seems a bit much to me also.

Hopefully Dave, Jack and Steve will jump in here on this one also.

Mike
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Old Oct 05, 2009, 07:39 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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sdj544 asked:

"..How much does the thickness of the step affect things?..."

You may have two things confused a little. The wing has thickness, the step has height.

The height of the step can vary quite a bit with the type of plane and wing involved and the materials used. I'd generally like to have 1/4" or so and think they start looking too high at around 1/2". But I don't know that they will assuredly fly badly at 1/2" high.

Wing thickness is the thickness of the wing at the top of the step normally as it is measured at the thickest part of the wing.

Step height is the distance from the top of the step down the wing surface (or the top of the next KFm strip if there is one butted up against the step).

"..I was thinking of building a FFF version of VQ models VTO:http://www.vqmodel.com/MateriePrime...nes/VTO/VTO.htm (or a UFO or Nutball) using either KFM2 or KFM4..."

That looks like a design that might work with a KFm wing.

The Nutball is a flat plate wing, not really a comparison to KFm wing at all. Flat plate wings generally have no lift and do not glide. They fly at a high angle of attack (AOA) and the exposed bottom surface's resistance to the air supports the weight.

"..but for a 32" wing I would need 1.5 inch thick spar. That seemed a bit excessive..."

The percentages in the figure are recommended starting points for more conventional wings. Wings that are more rectangular than round.

You are plowing new ground here with a half round more or less wing and you would have to work out the details. I'd probably try building that in a KFm4 because the performance of that wing would most likely be better for that plane than a KFm2 would.

I'd probably make it with FFF (1/4" nominal thickness) and 1/4" square spars. I'd epoxy the spars to the top and bottom of the wing at the 50% line and rest the KFm strips on top of the spars. That would make the wing about 1-1/4" thick at the steps and the steps would be about 1/2" high.

That step height is a little higher than I've used before but I'd give it a try because the wing's aspect ratio makes it a little bit short on wing span so the extra height might provide more lift.

The figure there says the fuselage length is 595mm/23.4". I'd guesstimate the chord as being only about 18-20" of that length so a wing thickness of 6-9% would be in the 1.1"-1.7" range. And the build I mention is in that range so it might work.

That could have pretty good lift once it gets moving (it will not be a slow flier I think) and little inherent stability with it's low aspect ratio (the ratio of wing span to fuselage length). You'll have to plan on flying it full time.

You are inspired by a design that has not been done you in KFm I think, you're plowing new ground and will have to work out the details.

Jack
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Old Oct 05, 2009, 10:41 PM
PunchDrunk ex-Pug try'n fly'n
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Quote:
Originally Posted by davereap
The glide tests to determine the best position for the KFm2 were made with steps at various locations and the best result found was at 50%
Hey Guys, were these tests done with one step only?
If so I wonder where the step intersects the CG. If I might wager a guess, I would say close to the MAC line.

I think we are approaching the crux of the dynamic here.

Anybody done a study on the relation between the MAC, CG, and step placement?
Apache Pilot was talking about this relationship on the old thread about two weeks ago.
jp
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Old Oct 06, 2009, 06:36 AM
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The test video was not mine so I dont have any other info, you will need to search for that little T tail glider to find the originator
I reposted the video to youtube as the original was slow to upload.. there were other vids with other step locations, you will see his info says test 3, where was test 2?

cog... on the tests not known... but your cog will obviously vary with step location, and personal preferences on how you like the plane to fly..But as with any design start with a safe forward location or whre the plan specifies and move back slowly untill its as you like

edit.. with only a vague memory I finaly tracked down the man who made the tests.. Mr Doug Montgomery... check out his various KFm glider build threads including the depron dynamite dlg.
here is the tests thread.. http://www.rcgroups.com/forums/showthread.php?t=629435

I read up on Dougs many build some time ago when I got interested in the DLG idea, but at my age twirling round to chuck up a glider just knackered me out so I went back to getting them up with a motor... much more suitable
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