DS-21 (TD-19) compared to HQW2.5/9

[Tony D.]

After I finished the templates for my new HQW wing I modded the DS-21 using information supplied here by J.W. and the Maple Leaf Designs website.

Finished it up last night and here it is with a comparison to the HQW2.5/9.

The camber as quoted at Maple Leaf Designs is 2.25, my mod. finished out at 2.28% with an 8.98% thickness. I think it looks like a great section and I'm going to try it next.


T.D.

[Tony D.]

Here is the DS21-Mod compared to the AG40D at 100K.


T.D.

[BMatthews]

That's a pretty slick looking polar. I take it by the TD designation you've been burning some midnight oil with Xfoil or similar?

[Tony D.]

Yes, Xfoil and then I import to Profili for printing etc.

The TD19 is the Joe Wurts original airfoil that is used on the 'Icon' and Daryl Perkins 'Insanity'. This is as close as I can come without actually seeing the coordinates for the actual airfoil, which I've been unable to get.

I'm still glad I did the templates and cut the cores for the HQW wing but after seeing this I've decided to do re-think my plan and build a DS21-Mod wing first.

So it's off to the shop.


T.D.

[tonyestep]

Looks good. Thanks for posting your coordinates. I duplicated your results with Xfoil.

Before you make your final decision you might want to try the effects of flaps. Thinning the airfoil may help it work better through a range of flap settings.

Note that the AG40 has better high-speed performance and the TD21 floats better. If you want to tweak this, you could try Xfoil's inter function to combine the airfoils in various proportions.

[Tony D.]

Thanks, Tony.

I'm doing a four taper wing with this and last night I started work on optimizing the airfoils for the outboard breaks.

Got a lot of very useful information from Joe Wurts in the post I am quoting below and I am doing 5 seperate and tweaked airfoils for the span of the wing per Joe's post.

Lots of work but it is great fun! I should have an excellent thermal duration glider at the end of this, I'll do a another build thread in the Composites Forum.


T.D.

"The "JW19" is a rename of the td19 that is used for the bulk of the Icon wing. (or at this point, maybe I should call it the Icon "1" wing). It has also been used on some other aircraft, such as various DP designs in the past few years. Add a little thickness and camber to the ds19, and you will be pretty close to the td19.

If you want to get a little more "optimized", you could use the ds19 at the center, and start reducing the airfoil thickness as you go outboard on the wing. This thickness reduction is to get better section performance outboard where the spar requirements are not as much of a problem, as well as reducing the penalty due to decreased Re outboard. I'd also suggest a wee bit of camber adjustment to make sure that the Clmax and high Cl drag characteristics of the outboard portions of the wing are still in line with the center performance.

Also recommended is nudging the max thickness and camber positions slightly forward as the Re gets lower on the shorter chord outboard sections. One can also get good handling qualities via having less taper than optimal with a low cl capability section on the outboard portion of the wing. The real fun is in playing optimization games, trading between airfoil and planform.

The origination of the ds19 was to meet Brian McLeans desire for a 2 meter wingspan combination sport sloper and DS ship. He wanted good DS capabilities, but still wanted the plane to perform well for frontside light air conditions. In other words, the light air conditions ended up having a derived requirement for similar characteristics as a thermal oriented aircraft. The result, an airfoil that should work reasonably well for TD.

Joe"

[tonyestep]

After I posted the comment about interpolating the airfoils, I tried it. Half-and-half gives a section that has very close to the performance of the AG40 at lower CL, while retaining a higher maximum CL like that of the DS21. Looks really appealing.

BTW, where did you get the coordinates of the DS19? Can I get 'em?

[Tony D.]

I've tried a few interps. using the DS19/21 AG40 and S9000, they all look good and the S9000 is itself a good looking airfoil that reacts well to modding.

The DS21/AG40 interp. is a great looking section

I've included the files.


T.D.

[Bernd Brunner]

@Tonyestep

look here:
http://www.rcgroups.com/forums/showthread.php?t=309550&highlight=ds19

Bernd

[Tony D.]

Okay, here are four sections I am thinking of using across the wing, so I will be going with three tapers instead of four.

These are not derivatives of the DS21 but are derived from existing airfoils.

I'm looking for comments please.


T.D.

Black = Root Section 9.5% Thick at 2.5% Camber

Blue = Break One 8.68% Thick at 2.48% Camber

Purple = Break Two 8% Thick at 2.5% Camber

Green = Tip 7% Thick at 2.44% Camber

[nuevo]

Don't you need to run the sections at the various Re? For example, the tip section is likely to operate at 40% of the Re of the center section.

[Tony D.]

Yes, and I was going to post those Re specific Polars but my shoulder is killing me and I can't type anymore for an hour or so.

I'll post them later tonight.


T.D.

[Tony D.]

Here they are.

T.D.

[Tony D.]

Looks like a negative difference in the zero lift angle of attack between the 119K plot (panel 2) and the tip at 71K so I think panel 2 will need to be washed out by about .25 degrees and panel 3 will be rotated to match.

These are for a 3.25 metre plug in style two piece wing and I need the 9.5% thickness at the root to accept the wingrod.


T.D.

[tonyestep]

Bernd,
Thanks!

[tonyestep]

Note that when you make polar plots in Xfoil, for our purposes you want to set Type=2.
This gives you a picture of the airfoil's speed range. You set the Re for the highest CL you expect to fly at, and then as you point the nose down to raise CL, the Re is automatically adjusted.

[Tony D.]

Tony, thanks for that bit of information.

I'm going to re-do the Polars tonight with that in mind.


T.D.