Derek Boyer writes:
>Thanks John. I stumbled across the CRCC website yesterday
>and found Drela's new HLG. I'm always looking for cool HLG
>airfoils and will give them a look. Never did think about
>a turbulator as you suggested. That might even be easier
>than sanding kevlar, carbon, glass and foam :-)
Turbulating HLG tails is almost futile. The Reynolds number
is too low to permit significant turbulent flow, so if there's
laminar separation it is very hard to quash.
A much better approach is to rely on *attached* fully laminar flow,
so that tripping is a non-issue. Attached laminar flow can
be obtained with a thin airfoil with the max thickness point
far forward, as you discovered. Such airfoils always give well
behaved control response no matter how low the Reynolds number is.
The HT05 airfoil on the CRRC site takes this one step further.
It has attached laminar flow even with a modest flap deflection,
so that crisp control is maintained when holding fixed
up elevator in a thermal circle. The trick that does this
is the slight dimple in the HT05 surface at the hinge line.
This is "not your father's simple slab tail section",
but it's worth the extra effort to build IMO.
- Mark
--
- Mark Drela
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