Undercamber airfoil-wing questions

[soar-ne]

I want to build a simple stick type indoor flyer useing sturdyboard foam, bent into a undercamber airfoil. I have three questions I would like your opinions on
1. for a given wing area which will give the most lift at low speed, a longer wing with a slender chord or a stubby wing with a larger chord?
2.On a undercamber wing is the lift ruined much by putting the spar (1/8th inch dowel) on the bottom of the wing out in the open airflow, or would it be better to imbed the spar into the foam?
3. What would be the best dihedral for a slow flying airplane,vee type in the center of the wing, or double dihedral break at the wing tips like some older free flight models?
Thanks in advance for your comments
Bob

[Sparky Paul]

A long wing will turn slower than a short wing. Indoors this can be a design parameter.
The exposed spar won't affect anything.
Plain vee-dihedral or tip dihedral will work equally well.

[BMatthews]

Some wide packing tape over the dowel spar to spread out the "bump" will clean it up a little so there's not so much drag. I suspect it'll be a small improvement but you can try it. I also think you'll find that a one inch wide bit of 1/8 balsa sanded to an arch and glued onto the base will provide more of a spar function than a length of flexible 1/8 dowel will. The balsa can be tapered over the span so it's wide at the root and narrow at the tips.

Tip panel dihedral will provide a bit more bang for the buck response wise than simple V dihedral will just because it puts the rolling action out further on the wing for the same amount of yaw.

[adam_one]

I want to build a simple stick type indoor flyer useing sturdyboard foam, bent into a undercamber airfoil. I have three questions I would like your opinions on
1. for a given wing area which will give the most lift at low speed, a longer wing with a slender chord or a stubby wing with a larger chord?
Thanks in advance for your comments
BobThe longer wing (high aspect ratio) has a higher lift coefficient but stalls at a lower AoA than the stubby wing.

[Martyn McKinney]

Reynold's number Re should be taken into account for low speed flight.

Reynold's number is MPH X Chord(in) X 760.

Although high aspect ratio wings have higher lift coefficients at higher Reynold's numbers, for low Reynold's numbers (20,000 ?), low aspect ratio wings are preferred.

This is one reason why empirically many of the indoor fliers use IFO type airplanes.

[adam_one]

Agreed.
One may say that for a given wing area, increasing the aspect ratio may result in a too small wing chord with a too low Re number which may significantly reduce the lift coefficient.