Actually, I think, given the AG airfoils, optimum aspect ratio is
probably a function of your vision. Given very good vision and very good
skill with composites, optimum aspect ratio is probably upwards of 12,
as in the original Agea 2M. More realistically, maybe a bit over 11.
Wing loading shouldn't be an issue, given enough building skill, as 21
oz. can be acheived. Maybe 25 oz. for all the other really good builders
besides Mark. You can add ballast on windy days. Carbon tailbooms and
some of the other more sophisticated building tricks keep the weight down.
Most of those old airfoils are now obsolete, aren't they? (I saw a new
foil, a thicker one, on the yahoo xfoil group, which behaves just like a
thinner AG, though)
In local contests, I end up competing against Mark. One of these days I
want to see what happens if I have a glider almost as good as his is.
From: David Register wrote:
snip
snip
Beause of it's size, a 2M is not going to be able to roam as far
or as high as an open class ship - it's simply harder to see at
distance. So, like DLG, it's going to be more of a close-in ship.
Consequently, it probably should tend to better minimum sink and max L/D
rather than having great 'legs' for roaming all over the sky. This tends
to drive the design towards lower aspect ratios. Due to the span limit,
a high aspect ratio 2M may start to run into Re problems.
Carrying more wing area will allow a lower wing loading with modest
attention to building techniques. This should also help with the launch
as more area would help to carry the tow weight better.
The airfoils often used for 2M are not particularly well optimized for
this class. If you run X-Foil snip
So a couple of suggestions;
- Look to lower aspect ratio designs. An evaluation discussed in RCSD a
few years back suggests the 8 to 11 range is about right.snip
- Sort through the Drela sections, many of them are much better in the
intermediate speed range than any of the sections commonly used for 2M,
snip
- Work a bit on keeping the weight in the 30oz range. A ballast box is
great for the windy days but it's tough to add lightness.
snip
- Dave R
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
"unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe
messages must be sent in text only format with MIME turned off. Email sent from web based email
such as Hotmail and AOL are generally NOT in text format
