Need help in choosing an airfoil profile for a fairly heavy long range tail pusher

[SaltyItalianGuy]

I'm designing a slow-moving plane for long range and it will end up a bit hefty, likely more than 2-3 kg.
I was thinking of a 2-2.5m wingspan with a 30cm chord at the root as it would give me a wing loading between 4.5 and 6 kg/m^2 (assuming the wing gets a bit thinner at the extremities and worst case scenario of 3kg) but I'm fairly new to designing this type of thing and I want to get my initial design parameters right so any tips would be much appreciated.
Secondly, I would really appreciate some help in choosing an airfoil, I'm going to be printing the wing out of lw-pla and running a carbon spar through it (though I'm curious if I need to run it all the way through or if like 75% is fine?) so I need something with good lift at low speed, would a highly cambered wing be best? or should I go with a traditional glider wing that might have less drag? I'm a bit worried about my TWR as I'm not sure I can get it all the way to 0.5 which is why I want something that makes a decent amount of lift so that I can climb well without completely draining my battery.

 

[quorneng]

It is going to depend on what you mean by slow and I presume by "long range" you means distance covered.
Speed is almost directly proportional to wing loading. The practical difference in actual flying speed with different section will not be huge.
Of more concern is how it behaves if it gets really slow as this is where the wing section can make a difference. An under cambered section can get tricky as you approach the stall whereas the humble Clark Y is often chosen for trainer planes simply because it has a predictable and benign stall.
As far as range goes what is the limiting factor on how far it is likely to go?
If it is battery capacity then the overall aerodynamics are important. Using a glider type aerofoil and with good airframe streamlining will allow it to go further for each Amp hour of battery capacity.
If IC then the aerodynamic efficiency is a bit less of a concern as fuel has a much higher energy content per kg than any battery.
This gives some of the parameters involved but without some more detail of the design and how it is powered it is difficult to comment in more detail.
As far a carbon tube spar goes it does not have to go to the tip but where ever it stops would represent a weak spot. The strength of the wing suddenly changing to what ever strength the printed wing alone will have.
Of course if it was a tapered spar designed to match the flying bending stresses it could gradually taper to nothing at the tip and have no weak spot.

 

[SaltyItalianGuy]

It is going to depend on what you mean by slow and I presume by "long range" you means distance covered.
Speed is almost directly proportional to wing loading. The practical difference in actual flying speed with different section will not be huge.
Of more concern is how it behaves if it gets really slow as this is where the wing section can make a difference. An under cambered section can get tricky as you approach the stall whereas the humble Clark Y is often chosen for trainer planes simply because it has a predictable and benign stall.
As far as range goes what is the limiting factor on how far it is likely to go?
If it is battery capacity then the overall aerodynamics are important. Using a glider type aerofoil and with good airframe streamlining will allow it to go further for each Amp hour of battery capacity.
If IC then the aerodynamic efficiency is a bit less of a concern as fuel has a much higher energy content per kg than any battery.
This gives some of the parameters involved but without some more detail of the design and how it is powered it is difficult to comment in more detail.
As far a carbon tube spar goes it does not have to go to the tip but where ever it stops would represent a weak spot. The strength of the wing suddenly changing to what ever strength the printed wing alone will have.
Of course if it was a tapered spar designed to match the flying bending stresses it could gradually taper to nothing at the tip and have no weak spot.

Thanks for the help! I'm going to take your advice and go with a glider-type aerofoil to get better range, and I'm also going to look into making some tapered spars as they sound like exactly what I want.

 

[Shurik-1960]

In my models, I use conical spars - these are the ends for repairing rods of 1 m. Cheap and reliable.All wings with a span of up to 2m are intact.

 

[Piotrsko]

There are online model aircraft programs that predict how the plane will respond after inputting bunches of design parameters. Google for them. Need to tell the plane and hope it listens, but the predictions are close.
I like fishing pole blank$ for spars: tapered, strong and springy and relatively cheap.