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Old Jan 04, 2008, 04:16 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
Help!
KF Aerofoil for Glider

Hi,
I am making a glider out of elmers foam board style stuff and would like to know what aerofoil I should use some use 40% top or 50% top and then someone came along and said 50% bottom????? I am confused please help!
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Old Jan 04, 2008, 05:03 PM
Will work for foam
wingnutt's Avatar
United States, WI, Muskego
Joined Apr 2005
1,502 Posts
For a glider, go with 50% top.
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Old Jan 04, 2008, 05:17 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
How well does it work? what sort of weight will it glide at and i forgot to metion its for a DLG
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Old Jan 04, 2008, 06:26 PM
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JMPaccassi's Avatar
Fresno, CA
Joined Jan 2007
49 Posts
Lambo,

I used elmers foam board to build a DLG w/ KFM & it seems to work great. I made mine a top step at 50%.

40" WS 6.25oz AUW

I posted a vid in the sailplanes vid gallery 2 days ago if you'd like to see it in action. If you need anymore info let me know

JP
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Last edited by JMPaccassi; Jan 04, 2008 at 06:36 PM.
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Old Jan 04, 2008, 07:12 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
Hi,
I saw your glider in the other kfm glider forum and it looked like it flew great! I think I will go with 50% topstep
Thanks

Also how long is it?
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Old Jan 04, 2008, 07:58 PM
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Fresno, CA
Joined Jan 2007
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Length is 31.75 in. Good luck with the build, DLG's are a blast!
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Old Jan 04, 2008, 08:05 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
also how wide is your wing? not wingspan
edit:maybe lenght?
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Last edited by Lamborghini12345; Jan 04, 2008 at 08:18 PM.
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Old Jan 04, 2008, 08:44 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
long is your wing?
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Old Jan 05, 2008, 12:25 AM
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RWCLOUD's Avatar
Fresno CA
Joined Jul 2006
1,745 Posts
Welcome to the world of hand launch guys! It can become addictive!!

Go to this link http://www.charlesriverrc.org/ then go to articles and tips index,then to the online plans section, then to the Apogee. Read the articles about the Apogee.

In the Hand Launch Forum look for stuff by Doug Montogmery , He did a lot of work on the KFM wings for hand launches last year. He may have been the first to use the KFM / Depron wing, so he deserves a lot of credit for his work !

How much should these little things weigh ? Dr Mark Drela says 3.1 ounces or less per Square foot of wing area. If you don't know who Mark Drela is , he probaly knows more about gliders than anyone in the world ! If he says something belive it !!! Most of the newer compition gliders of any kind are off shoots of his designs.

Blue Skies ...... R Dub
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Old Jan 05, 2008, 01:54 AM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
can I just say yours wa the inspiration!!! I looked at yours for weeks! and now I will make one! I think it may end up around 6-7ounces and with a 40" wingspan with 7"long wing so 3.5" will be the KF does this sound ok?I will try and make it as light as possible.
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Old Jan 05, 2008, 02:03 AM
dougmontgomery's Avatar
Glendale,Az.
Joined Oct 2004
3,539 Posts
heres a good base to work off of

Hope this helps, 7" is almost too big of a root, try 6.5 and 4" at the tip.

Doug
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Old Jan 05, 2008, 10:53 AM
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JMPaccassi's Avatar
Fresno, CA
Joined Jan 2007
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I made my wing 6" wide, I started off by cutting 2 seperate panels 20" x 6" & then just rounded out the tip by eye, then cut my steps 20" x 3" & laid them over the other panels, traced the curve at the tip with charcoal pencil & cut. For the basic measurements I used sailplanecalc(sp?), should be able to find it here doing a search. My tail ended up being a little long which is why I'm using such a heavy battery (1.9oz), with a slightly shorter tail moment, I would've probably been able to shave another 1/2 oz off of my AUW.

JP
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Old Jan 05, 2008, 11:02 AM
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Fresno, CA
Joined Jan 2007
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Double post deleted, darn browser back buttons!
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Last edited by JMPaccassi; Jan 05, 2008 at 11:07 AM. Reason: Double post
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Old Jan 05, 2008, 11:11 AM
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RWCLOUD's Avatar
Fresno CA
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JP : I don't think the tail can be to long , the longer the tail , the higher the launches. It looks like your're using an arrow shaft for the boom , right? Next time scrape /sand the last half to a taper. There is a lot of epoxy used in making arrow shafts so getting rid of it will make the whole glider lighter.

Sand the foam tail parts more also. And use .012 to .015 wire for push rods. Every gram that you save at the tail will save 4 to 5 grams at the nose. 2 1/2 grams saved at the tail will make the total weight 1/2 ounce lighter !

Blue Skies .....R Dub
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Old Jan 05, 2008, 01:04 PM
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JMPaccassi's Avatar
Fresno, CA
Joined Jan 2007
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Boom

RW,

I think the boom may be my problem, I am using a carbon tube that I bought at hobbyTown, it's .210" O.D. x .132" I.D. x 27.5" never weighed it but is kinda thick walled, maybe a little heavy compared to other options??

Also, I originally had used wire pushrods(don't remember what size), but the AUW was at 7.3 oz to balance near CG & had to use carbon rods to get down to 6.25.

Here are some closer pics of my boom & tail, I have 2 guide tubes out on the boom secured by heat shink tubing, H-stab is secured to boom by (2) 3/16 x 3/16 wood squares stacked 2 high which are held down with fishing line & epoxy.

JP
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