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PRANDTL-D Foam Board Wing by FoamyDM

What plane should I add the Prandtl-D Wing to?

  • Mini-Arrow

    Votes: 20 41.7%
  • FT-Explorer

    Votes: 14 29.2%
  • FoamyDM-HS Carrier

    Votes: 6 12.5%
  • FT-Simple Cub

    Votes: 5 10.4%
  • FT-Tiny Trainer

    Votes: 11 22.9%
  • FT-Bloody Baron (somehow)

    Votes: 6 12.5%
  • Airliner

    Votes: 14 29.2%

  • Total voters
    48

FoamyDM

Building Fool-Flying Noob
Do you have a build thread and information on how you determined twist angle and how you accomplished it for the above model?
Thank you for the Interest @L Edge in this project.
:unsure: I don't think I understand what you're asking. the... this IS the build-log page... Specifically Posts#2 and better, yet post #3 (soon to also include Post #4) and Part #10 "Twist guide" on the Right of the Free Plan sheet from post #97.

The... Twist angle was something determined by NASA chief Engineer Albion Bowers using Ludwig Prandlt's 4 page paper on solving the lift equation for efficiency. After listening to Al's talks at Oshkosh, EAA workshop and some of his other videos (available through Youtube) and the Information Published by the AMA and they had the airfoil and twist information on their website for a while, and in detail in Al Bowers' Technical NASA Paper, which covers not only the foil sections, but the twist angles. I took that information and... dumbed it down a bit so it would be simple and buildable using the DTFB Build methods we are familiar with here.

As outlined in post #1, #2, and #3 and some others... there are three (3) KEY things that allow this fly without rudder.
  1. The wing airfoil goes from a Modified Clark-Y (roughly) to a symmetrical airfoil by the tips.
  2. The twist is +8° at the root to -2° at the tip. This is a 10° twist. (The motor is mounted with a Thrust angle of 0°.)
  3. The control surfaces are only on the outer 25% of the wing.
On a related note
Here's an update on what they are doin with the MARS wing:
 

L Edge

Elite member
First of all, not here to hijack your Prandtl D wing. Doing my own thread in reference to swept wings and what I am attacking. A lot of my research is based on the Prandtl research of what you are doing and offshoots of that.

Wanted to share and compare in depth reports since this is a new area to see if it sheds new light for me or reverse. Forward Swept Wings have the reverse flow direction across the wing. Besides needing wing stiffness and torsion problems, can I get it to fly without a rudder?
Some say, no way. Isn't finished yet for maiden flight.

It is amazing on how much data is out there already. Remember, there is no fuse on this design. As you can see, started to modify this non existing thing to see if it goes. Willing to listen to ideas to help it succeed where especially you have working knowledge on swept wings and its problems.

Already laying out another concept on wings based on my readings.

one.JPG


two.JPG
 

FoamyDM

Building Fool-Flying Noob
@L Edge I appreciate you sharing the information you are testing yourself as I hope it will interest others too. Please link the research papers and a link to your build thread.

I have almost finished a build video for the project. Sadly I forgot to take a picture so
Here are some of the finished product.
IMG_20211114_090303539.jpg
IMG_20211114_090222841.jpg

I the picture below not the different airfoil sections on the wingtip vs the base, along with the twist
IMG_20211114_090241274.jpg
 

L Edge

Elite member
@L Edge I appreciate you sharing the information you are testing yourself as I hope it will interest others too. Please link the research papers and a link to your build thread.

I have almost finished a build video for the project. Sadly I forgot to take a picture so
Here are some of the finished product.
View attachment 211698 View attachment 211699
I the picture below not the different airfoil sections on the wingtip vs the base, along with the twist
View attachment 211700
Will do.
Hope you don't mind questions, reason is too see if you tried it in actual flight.
My question to you is "Did you try different rates of deflection on your control surfaces(differences in drag between wings) to see if any results?
 

L Edge

Elite member
It will be very interesting with my FSW. Since the flow is directed inward across the wing(not like the ASW) it should be interesting stuff. Hey, if I can morph my ASW to FSW plane in flight and do it successful, who know what will happen? The avain approach has really inspired a lot of new stuff in my reading and projects.
For instance, the CG is 4.5" ahead of V section, hoping the stabilizer will reduce drag and will it change the pitch problem and yaw? Will it require to put EDF in front,etc?
 
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FoamyDM

Building Fool-Flying Noob
It will be very interesting with my FSW. Since the flow is directed inward across the wing(not like the ASW) it should be interesting stuff. Hey, if I can morph my ASW to FSW plane in flight and do it successful, who know what will happen? The avain approach has really inspired a lot of new stuff in my reading and projects.
For instance, the CG is 4.5" ahead of V section, hoping the stabilizer will reduce drag and will it change the pitch problem and yaw? Will it require to put EDF in front,etc?
Isn't it cool that you can test these ideas so easily with these Materials? I love it. Keep it going. So the goal is to change direction mid flight?
 

FoamyDM

Building Fool-Flying Noob
Will do.
Hope you don't mind questions, reason is too see if you tried it in actual flight.
My question to you is "Did you try different rates of deflection on your control surfaces(differences in drag between wings) to see if any results?
The big one Flies Amazing. I think I set it on Mid Rates. but they were symmetrical. I'm sure exaggerated inner turn aileron deflection would aid in Yaw control like a Drag rudder would.
 

L Edge

Elite member
Isn't it cool that you can test these ideas so easily with these Materials? I love it. Keep it going. So the goal is to change direction mid flight?
No. Just fly as regular plane.
With inward airflow on each of the wings, it causes vortices as they meet, so by adding the additional airflow from the EDF going down and across wing, what interaction will result? Hoping for better pitch stability.

Since wings are so fragile, to get CG right, (4.5 " ahead of fan in air) will try positioning heavy battery in front of EDF on rack for first shot. Also problems with leading edge flow according to wind tunnel reports, so added my stabilizer to redirect flow. Now working on new design for handling the adverse yaw.

Reason for endplates for now is, if left off, as I try to launch and nose down crash, as wing digs into ground, it may allow me to try again rather than total disaster. Been there, done that.

Since I expect lots of crashes, my first goal is get it to launch and see what happens.
So, depending on my gut feeling, I have also added the use of movable canards(think gyro) to get it into the air rather than have it flip up or down.

Here is my first experience with FSW years ago with using CG calc and what really happens. Surviving crashes save a lot of time. Problem was not having fixed canard forward enough for stability.




.
 
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No. Just fly as regular plane.
With inward airflow on each of the wings, it causes vortices as they meet, so by adding the additional airflow from the EDF going down and across wing, what interaction will result? Hoping for better pitch stability.

Since wings are so fragile, to get CG right, (4.5 " ahead of fan in air) will try positioning heavy battery in front of EDF on rack for first shot. Also problems with leading edge flow according to wind tunnel reports, so added my stabilizer to redirect flow. Now working on new design for handling the adverse yaw.

Reason for endplates for now is, if left off, as I try to launch and nose down crash, as wing digs into ground, it may allow me to try again rather than total disaster. Been there, done that.

Since I expect lots of crashes, my first goal is get it to launch and see what happens.
So, depending on my gut feeling, I have also added the use of movable canards(think gyro) to get it into the air rather than have it flip up or down.

Here is my first experience with FSW years ago with using CG calc and what really happens. Surviving crashes save a lot of time. Problem was not having fixed canard forward enough for stability.




.
Tail heavy, looks like.......

:unsure::unsure::unsure::unsure::unsure::unsure:
 

L Edge

Elite member
Understand the twist induces yaw moment, how are you handling the pitch situation?

Most flying wings have a couple of degrees trimmed in for reflex, are you?
 

FoamyDM

Building Fool-Flying Noob
Understand the twist induces yaw moment, how are you handling the pitch situation?

Most flying wings have a couple of degrees trimmed in for reflex, are you?
There is no reflex. I repeat. None. The modified Clark -Y has a turned up trailing edge. (Similar to reflex.) I do this with ironing the underside.
 

FoamyDM

Building Fool-Flying Noob
By the way... Post 4 of the Prandlt-Arrow now contains the maiden video. And some final looks.
I will say, reinforce the top and bottom with strapping tape from CG point to CG point . It will help In a nose dive crash