Testing to see if wings actually work?

[The Fopster]

I've done an interesting experiment this week. My own design simple EDF uses a simple flat plate wing - like a lot of flat plate 3D foams etc. It flies just fine, but I couldn't help wondering if it would be even better with some sort of airfoil wing profile. So - I decided to test it out. I added some simple foam board wing upper skins with a foam board added spat to hold the shape and went flying to see what happened. Spoiler alert - the difference was not only detectable, it was really obvious. It flies faster for longer - manoeuvres like big loops look much better as it carries speed better, and I can now extend my flight duration without over taxing my batteries. Honestly I'm amazed how well it worked - definitely worth the experiment!

Here's a short video below of my morning at the field...

 

[Erasmus80]

A great piece of empirical work! Thanks for sharing it.
I have some questions if you are willing to share more:

1. Was your upper surface material simply a thinner sheet of foam, bent over the foam spar you mentioned?
2. About how thick is the modified wing relative to the unmodified wing?
3. Did you round the leading edge or taper the aft end of the upper sheet as part of the changes? I've often seen improvement adding a round dowel to the leading edge of a flat plate.

I'd also expect you to see a real difference in "pull up" performance, such as during a loop. Flat plates really suffer from separation drag during a higher-than-normal angle of attack.

Again, a great idea!

 

[The Fopster]

A great piece of empirical work! Thanks for sharing it.
I have some questions if you are willing to share more:

1. Was your upper surface material simply a thinner sheet of foam, bent over the foam spar you mentioned?
2. About how thick is the modified wing relative to the unmodified wing?
3. Did you round the leading edge or taper the aft end of the upper sheet as part of the changes? I've often seen improvement adding a round dowel to the leading edge of a flat plate.

I'd also expect you to see a real difference in "pull up" performance, such as during a loop. Flat plates really suffer from separation drag during a higher-than-normal angle of attack.

Again, a great idea!

Thanks for the positive feedback - it was an interesting experiment! In answer to your questions:

1. Upper surface was roughly the same thickness as the flat plate base - 5mm.
2. The spar was also 5mm - so the depth of the wing tripled from 5mm to 15mm. I thought the increased frontal area could offset any benefits, but that really wasn’t the case.
3. I made an effort to blend the upper skin into the profile, so the leading edge was somewhat rounded.

Interesting that you specifically mention loops - the most stark difference was doing big power loops where it maintained momentum MUCH better so the loops could be both bigger and faster. An interesting insight - thanks!

 

[Merv]

...My own design simple EDF uses a simple flat plate wing ... wondering if it would be even better with some sort of airfoil wing profile...

My own experiments have similar results.

a flat wing is by far the worst,​

a KF wing flies better,​

a faceted wing like the FT wing is better yet,​

a true air foil wing is the best, but not a lot better than a faceted wing.​

​

For me the ease of building a faceted wing outweigh the marginal performance gain of a true airfoil.
The FT wing is a good balance between performance and ease of build.

 

[quorneng]

The Fopster. Nice experiment.
You have discovered what has been known for good many years. A wing section allows wing depth without a drag penalty.
All my small 'built up' foam wings use top and bottom skins with just foam shear webs. A true spar is only added if the load requires it.

The unreinforced wing of a 860mm span all sheet foam Hawker Hunter. It uses a 50mm EDF with an 11 blade fan.
Note the trailing edge tapers to a fine point. Like a rounded leading edge it too makes a difference.

 

[The Fopster]

The Fopster. Nice experiment.
You have discovered what has been known for good many years. A wing section allows wing depth without a drag penalty.
All my small 'built up' foam wings use top and bottom skins with just foam shear webs. A true spar is only added if the load requires it. View attachment 240416
The unreinforced wing of a 860mm span all sheet foam Hawker Hunter. It uses a 50mm EDF with an 11 blade fan.
Note the trailing edge tapers to a fine point. Like a rounded leading edge it too makes a difference.

Now that’s an amazing coincidence. My only balsa model is a 50mm EDF Hawker Hunter built from a Tony Nijhuis kit. It has flat plate wings, and now I’m working out how best to upgrade it!

 

[The Fopster]

My own experiments have similar results.

a flat wing is by far the worst,​

a KF wing flies better,​

a faceted wing like the FT wing is better yet,​

a true air foil wing is the best, but not a lot better than a faceted wing.​

​

For me the ease of building a faceted wing outweigh the marginal performance gain of a true airfoil.
The FT wing is a good balance between performance and ease of build

I’ve also tried KFM with good results. Quick and easy to build from cheap insulation foam, but now I’m wondering if they are worth revisiting!

 

[quorneng]

The final test will be the weight you end up with.
This a my Hunter F6. All built up using sheet foam with no reinforcing anywhere. The ducting is 3D printed.

It weighs 620g (22 oz) ready to go with an 1800mAh 3s. Being so light that is all the battery it needs.

 

[Air-headed Aviator]

one can think of the capability of a wing as related to the curvature it has. The strength of the lift it produces can further be related to the difference between curvature on its top vs the curvature on its bottom. Simplified concepts of course but for low speed performance the more curve the better. Even a flat plate wing can be suggested as having "curve" the moment its flown at a positive Angle of Attack, but an airfoil allows more of this "curve" at lower angles and lower speeds/with less energy.

 

[The Fopster]

The final test will be the weight you end up with.
This a my Hunter F6. All built up using sheet foam with no reinforcing anywhere. The ducting is 3D printed.
View attachment 240421
It weighs 620g (22 oz) ready to go with an 1800mAh 3s. Being so light that is all the battery it needs.

I’ve seen pictures you’ve posted of the internal structure of your Hunter. It’s amazing - looks like the ducting is actually the main structural componen with the skin just wrapped around it. Amazing work!

 

[FoamyDM]

My own experiments have similar results.

a flat wing is by far the worst,​

a KF wing flies better,​

a faceted wing like the FT wing is better yet,​

a true air foil wing is the best, but not a lot better than a faceted wing.​

​

For me the ease of building a faceted wing outweigh the marginal performance gain of a true airfoil.
The FT wing is a good balance between performance and ease of build.

The facetted wing also is a good bit stiffer, as the paper remains on both sides of each ace of the foam layers. When trying build a smooth airfoil, I leave paper on the inside layer in strategic spots where I a
Don't have curves. It helps with the form of the roll over curve, lightens the wing some, and keeps the stiffness.