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26 Apr 2014 14:45 - 24 Oct 2016 19:26 #809 by Don B
Don B created the topic: Powered Aluminum Dragon
I am investigating a powered version with a giant scale model aircraft engine 15 hp 8 lb. My area does not have a glider launch near by (NJ near Phil). I desire a CD that can live outside on the ramp. I am trying to design out of aluminum, but lack some basic data. Right now I am looking for airfoil data and trying to size the ribs and spacing. I am looking for the cord-wise air-load distribution. Or basically how much more than 2 lb/sq ft. should I figure the leading edge load, and what torque moment should I use.
Last Edit: 24 Oct 2016 19:26 by System Administrator.

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27 Apr 2014 10:15 #810 by Phil Lardner
Phil Lardner replied the topic: Powered Aluminum Dragon
Hi Don,

I need to update my project page on the CD website - I've made a fair amount of progress since.

You can download a set of full scale plans from the website that will give you all the dimensions you are looking for. The plans are very detailed.

www.ihpa.ie/carbon-dragon/index.php/home...ans#full-scale-plans

For calculating wing and rib stress loadings, download my Excel spreadsheet and plug in your own figures for pilot weights etc. I highly recommend you get a copy of Jim Marske's Composite Design Manual, which contains all the methods and calculations I used in my spreadsheet. It will help you understand wing stress analysis.

www.ihpa.ie/carbon-dragon/index.php/cd-b...wing-stress-analysis

www.marskeaircraft.com/flying-wings.html - Composite Design Manual.

I can't help you with specific torque calculations as I didn't do any in my spreadsheet! I simply know that a leading edge made of two layers of carbon fiber (at +/-45deg to the long axis) are both stiffer and stronger than the original 0.8mm plywood leading edge specified in the original plans. Both Steve Arndt and Rick Mullins built their CDs using just two layers of carbon cloth and have load tested them to +5g and flown them at 70+mph without any issues. I plan to stiffen my leading edges even further using three layers (carbon-kevlar-carbon) to allow me to tow at even higher speeds behind a conventional sailplane tug. There will be a slight weight penalty but I have already managed to save significant weight in other areas (wing ribs and tail boom) so the net weight gain should be minimal if any.

My CD design has a wing loading of around 1.7lbs/sq-ft. Higher wing loadings will mean a higher sink rate.

All the best,

Phil.




This is a message from Don B at Carbon-Dragon ( www.ihpa.ie/carbon-dragon ) to you:

I see you are way into a modification of the CD. It looks like you know what you are doing, which is why I write. I personally do not work well with composites, and desire a CD that can live outside on the ramp. I am investigating a powered version with a giant scale model aircraft engine 15 hp 8 lb. My area does not have a glider launch near by (NJ near Phil). I am trying to design out of aluminum, but lack some basic data. Right now I am looking for airfoil data and trying to size the ribs and spacing. I am looking for the cord-wise air-load distribution. Or basically how much more that 2 lb/sq ft. should I figure the leading edge load, and what torque did you use.

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09 May 2014 14:24 #812 by Don B
Don B replied the topic: Powered Aluminum Dragon
Thanks to your help and others on I am moving forward to design of the aluminum rib. I use Cad and using an old cad trick to scale the paper (I used the 24" dim) I come up with a root cord of 64.8 and tip of 21.4 . I digitized the patterns for the root and tip ribs and flaperons at that scale. The three view drawing says 60" and 22" and the assembly manual says 61.2 and 22.5. Anyone out there with thoughts on this issue?

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14 Jun 2014 20:56 #813 by Roger Hardie
Roger Hardie replied the topic: Powered Aluminum Dragon
Hi Don

I am busy drawing up the CD in SolidWorks at the moment so I am running into similar issues.
Just my 50c but I would stick to the dimensions derived from the parts and templates on the plans. The 3view is a lot smaller than the plans and may have some values rounded off.

Regards

Roger

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14 Jun 2014 21:43 #814 by Don B
Don B replied the topic: Powered Aluminum Dragon

Roger Hardie wrote: Hi Don

I am busy drawing up the CD in SolidWorks at the moment so I am running into similar issues.
Just my 50c but I would stick to the dimensions derived from the parts and templates on the plans. The 3view is a lot smaller than the plans and may have some values rounded off.

Regards

Roger


I used the digitized templates for ribs at the 24" paper dimension, any given dimensions are very close at this scale. I laid out the root fittings for the wing dihedral and got 1.43 deg. One of my problems on the original post was I did not realize the wing joined at station WS 0 in the center.

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19 Jun 2014 20:53 #820 by Roger Hardie
Roger Hardie replied the topic: Powered Aluminum Dragon
OWE! I see, so because you can't see the root ribs in the 3 view, so you were actually measuring the chord a little way from the root ribs in the 3 view which explains the difference.

Or Have I got it wrong? :)

Would you bee keen to swap CAD info?
If you have the wing ribs done I would be keen to see them.
I have just finished tracing the ribs for the horizontal tail.
I also have the formers for the pilot Pod traced.
Maybe we can make a dropbox folder or something?

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