Mitsubishi Raiden wing profile?

[tomo pauk]

The tricky question are:
- type/series of wing profile used (claimed to be of laminar flow)
- wing thickness-to-chord ratio?

Some data can be accesed via convoluted channels, like this pic attached. The wing profile details might be the two rows I've marked with joint red '?'.

 

[Shinpachi]

It says -
主翼 Wing
翼幅 Span 10.800 m
翼弦 Chord 2.600 m
面積 Wing Area 20.050 ㎡
取付角 Angle of Attack 2°（機体中心に於て@airframe center）
Angle of Attack 0°（翼端に於て@wing end）
上反角 Dihedral Angle (前縁 Leading Edge）TAN? 1/10 （約 approx 5"43'）
後退角 Angle of Sweepback (前縁 Leading Edge）TAN? 14/155 (約 approx 5"10')
縦横比 Aspect Ratio 5.82

 

[tomo pauk]

Many thanks, Shinpachi
By chance, could it be that you have some extra information about the Raiden's wing, I'm very interested in thickness-to-chord ratio.

 

[Shinpachi]

Not finding at the moment

 

[tomo pauk]

Okay, thanks anyway

 

[Shinpachi]

You are welcome, tomo.
I'm now researching Professor Ichiro Tani's reports as he suggested his laminar airfoils to Japanese for the first time in the 1930s.
Give me some time. Thanks.

 

[Shinpachi]

Following is my estimation with apology if wrong.
Professor Tani seems having been thinking that symmetrical wing would be the best for the laminar flow airfoil.
No exact data for the wing of J2M Raiden but some wing diagrams in the J2M manual also show such symmetrical shape.
The LB24 airfoil which was introduced to Kawasaki Aircraft in 1941 by Tani also shows such design.
Most thickness is located at 50% of the chord.
I think the wing thickness-to-chord ratio is 1:10

 

[tomo pauk]

10% t-t-c would've been really amazing. Thank you again.

 

[Shinpachi]

You are welcome, tomo, but take apology if wrong

 

[Shinpachi]

All the wing thickness-to-chord ratios are within 10% in Tani's list.
LB55 looks closer to the J2M's now.

 

[tomo pauk]

Thank you for the table.
Is there an aircraft (or more of them) that certainly used any of the airfoils from the table?

 

[Shinpachi]

Yes, there are, tomo.
The table comes from Tani's report which summarizes his job for the military but he does not seem being allowed to clarify which airfoil for which airframe as of 1940. Famous LB-winged planes are Ki-78(Kawasaki), N1K1(Kawanishi), E15K1(Kawanishi) and R1Y(Kugisho). There may be more like J2M, P1Y and D4Y as the navy recommended strongly.

* e=0.1 as max thickness ratio in my last post

 

[tomo pauk]

Thank you again

 

[tomo pauk]

Not sure whether this can help us, but anyway. I've took a peek in the N1K2 manual available on this site (link), and tried to measure it via pdf tool. The t-t-c looks to be 15%.

 

[Shinpachi]

Airfoil for the N1K1 is LB620515-6075.
It's LB620515-6015512 for the N1K2J.
No more info at the moment.

 

[wells]

The airfoil was about 15% thickness at the root, at 35% chord. So, only mildly laminar flow.

 

[tomo pauk]

This is most interesting
Would you be so kind to share other data you might have about this topic?

 

[Aeroweanie]

This is most interesting
Would you be so kind to share other data you might have about this topic?

A relevant report: NACA TM-1351 "On the Design of Airfoils in Which the Transition of the Boundary Layer is Delayed"

https://ntrs.nasa.gov/api/citations/19930093879/downloads/19930093879.pdf

And, from a AAF tech intelligence report:

 

[bf109xxl]

The correspondence between the image and the table data for LB 55 seems to be appropriate taking into account the precision of drawing tools. The angle of attack is displayed incorrectly in the image (3.3° instead of 2.0°).

 

[Aeroweanie]

I digitized the airfoils shown in the figure in post #16 and then loaded each into Xfoil. Both have a little camber, but if this is removed, the thickness forms of both match the LB56 (scaled to the appropriate thickness).

Working with NACA TM-1351, I find that the likely designation of the J2M airfoils are LB560715 (0.787% camber, 14.61% thick) at the root and LB561114 (1.135% camber, 13.70% thick) at the tip