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Old Jul 12, 2014, 02:50 PM
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Joined Nov 2011
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Wood Plank

After having my spar-less foam wing fold using a 300 watt motor I decide to build a balsa plank. It turned out well, but did not fly as nice as my foam planks. The balsa plank only had 2" elevons and weighed a little more then the foam. I think 3 inch elevons would help the flying, but landings are a little too hot. So I decided to add a spar to a foam wing at the trailing edge because I did not want it on the face of the wing. I am sad the plank does not fly as well because it hold its shape over time. After about a 100 foam wing flights they start deforming and fly weird.

I may try a balsa delta. I think the delta will fly better. I find that my wings that have a further back CG will glide better and land slower. Plank vs delta with same weight and same surface area, the plank will not float in for a landing like the delta.

Does the CG affect the glide on well balanced wings with the same weight and surface area, but different rates of sweep ? Is it the more aft CG that lends to a better glide or is it the wing sweep ?
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Old Jul 12, 2014, 04:55 PM
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Joined Apr 2013
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Generally: Given the same wing area and weight, the one with the lower aspect ratio will be "easier" to fly (and will appear to glide "nicer"), but will have a lower glide ratio.
The nice thing about sweep is that you get the same effect that dihedral gives you (some roll stability) without having to actually have any dihedral.
Pure, rectangular planks are generally more twitchy than something with some sweep.
And yes, a more aft CG will mean less reflex required, which will mean less drag - so the glide ratio will be better. But there's only so far you can go back. Other factors like wing loading, aspect ratio and drag causing structures (like excessive winglets or protruding cameras) are the key contributors to glide ratio.
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Old Jul 12, 2014, 05:27 PM
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Joined Nov 2011
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Thanks nuteman. I am sure if I built super lite the plank would behave better during the landings, but it always seems windy where I fly so a lite plane may be not so good either.

Quote:
Originally Posted by nuteman View Post
Generally: Given the same wing area and weight, the one with the lower aspect ratio will be "easier" to fly (and will appear to glide "nicer"), but will have a lower glide ratio.
The nice thing about sweep is that you get the same effect that dihedral gives you (some roll stability) without having to actually have any dihedral.
Pure, rectangular planks are generally more twitchy than something with some sweep.
And yes, a more aft CG will mean less reflex required, which will mean less drag - so the glide ratio will be better. But there's only so far you can go back. Other factors like wing loading, aspect ratio and drag causing structures (like excessive winglets or protruding cameras) are the key contributors to glide ratio.
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