Edge Wingtips

[teryn]

If you want to increase the roll rate, the ultimate fix is not to add SFGs (a goofy non-technical term) or winglets or tip extensions. Just design the wing right way the first time to give you maximum roll (if it isn't already that way). It's solving the problem or defficiency at the source, not adding bandaids.

For those planes that you want to "fix", as Tod suggests, I would recommend, in Peter's case, tip extensions which you would have a much better shot at improving aileron flow. However, increasing the span changes a bunch of other important things, among them, increases the roll damping which could offset the improvement of 2D flow over the aileron that your extension may cause (at a given flight condition) in the first place - and now you've got the extra drag all the time. It's also going to increase your aspect ratio (for the same chord) which lowers your stall angle-of-attack, AND increases root bending moments - both not good for aerobatic airplanes.

[todhog]

Dood, yer way too smart.

Todd

[dick hanson]

here is my EDGE (H9) with my own designed tip plates -I did not copy the shape -just tried to imagine what would give best effect to stopping spanwise flow at the tip with least drag problems . I also clipped 4" from each pane tip - the extended spinner was another "trial" to eliminate prop to cowl interference
Thepower is a full piped ZDZJ and so far best prop is a 27x10 mejzlic - running about 6600 static -and 7150 (recorded) level full speed flight
I have done three of these with DA100 and ZDZ 80 - stock wings
this setup by far is better on rolls snaps in any attitude and just all arounf d better and Far mor power than any of th other setups (23 lbs)
the increased wing loading from chopping off the tips is NOT detectible- maybe th tip plates compensate - too hard to tell.

[adrian]

Trust Dick to be first - come on give us the real story - lol

looks nice even if they dont work - let us know!!!!! and more sticker space!!!

[dick hanson]

well - anyway --- it is very good at controllability at looow speed and high angles - just a touch of power and it goes right where you want it to go. no wobbly stuff or trying to "snap out". That is likely more a product of the shorter wing .
Next model will have extreme double wing taper- not an EDGE but much like an EDGE
this is it but wings will be short

[Ion01]

I would go with reducing the wingtip vortex for reduced drag and increased speed and efficiency. The wingtip vortex is what has caused a number of crashes in aviation over the years when other craft fly through them. Look at the current boeing aircraft and thier winglets.

I have recently been considering this problem regarding propellers and have recently conducted experiments, one which is pictured below, which illustrate this problem.
You can see in the fluid flow experiment, on a traditional prop, the wingtip vortex. this experiment was done with very slow flowing water, thus the vortex is small. As speed increases so will the size and strength of the vortex. I have a prop shape that doesn't just reduce this effect but completely eliminates it. I have recently finished a write up regarding my design and will be posting it soon. The post will not show my design as I need to protect it. I am currently writing a contract for those who wish to see my design and are possibly interested in producing it. I am hoping to have it up soon.

[Ion01]

Oops didn't load the pic......
here it is.

[teryn]

I am not sure what you are trying to show in that picture but it does not look like a vortex to me. Maybe you can describe your method of visualization and what you are trying to show us in that picture. It looks like it could be shadowgraph or schelieren technique.

I would like to see your proposal, along with the experimental data, and a concise and clear description of your theory and the math that's needed to justify it. Providing us anything else is just a waste of everyone's time and clutters these forums with baseless conjectures and non-scientific information.

For the same lift, the total vorticity will be the same no matter what you do. You can not get rid of something that is the fundamental mechanism for lift. You can come up with interesting ways to redistribute it but you can not get rid of it. You will always have a tip vortex...period.

	Quote: Originally Posted by Ion01
	Oops didn't load the pic...... here it is.

[teryn]

Dick, your wingtip look sharp.

[Ion01]

I just increased the contrast on the picture to show the vortex better. Like I said, it is relatively small due to the fact the the flow velocity is slow. Anyways, I will try to get the write up as soon as possible to help make things more clear and if you or anyone else is still interested then I will be happy to discuss it and provide additional information. Thanks for your interest.

[dick hanson]

Tip vortex is a product of air trying it's level best to return to it's normal placid state in life--
so --when you take a panel/wing/blade/ whatever and tilt it such that there is high pressure on one side and lower pressure on the other - like the airliner pic above - the air at the tip which is sliding spanwise (again, trying to get away), meets and natcherly- swirls as the two unbalanced flows combine.
A secondary effect -- is that this whirlpool creates a easier path for air sliding spanwise .
This is because it is a lower pressure path- The air being stupid, sees it as a shortcut and follows the path of least resistance.
So - a good tip plate will -at high angles of attack, slow the span wise flow somewhat-- at the higher pressure side and killing the production of a large vortex.
net effect : overall--more air is herded chordwise , doing the job intended .
Getting the shape where this COMPROMISE shape is best for the task at hand - is a scientific wild ass ed guess at best (SWAG)-because it is a moving target.
I close my eyes and try to imagine the flow -if I were I were creating shapes to redirect it.

[teryn]

	Quote: Originally Posted by dick hanson
	So - a good tip plate will -at high angles of attack, slow the span wise flow somewhat-- at the higher pressure side and killing the production of a large vortex.

Dick, your wingtips are really nice looking and you did a wonderful job with them....and that's pretty much where it all ends.

You are not "killing" the large vortex. You can reduce its magnitude by redistributing it but the total vorticity is the same. And....even if you redistribute the vorticity (one method is adding winglets), the induced drag may not be reduced. You have to look at the TOTAL vorticity or circulation across the wing span to see if the induced drag has gone down. In reality, it boils down to the fact that ONLY an increase in span can reduce the circulation and therefore induced drag (and I will be more than happen to argue that further). The Kutta-Jowkowski theorem states that clearly and can be verified in experimental tests. And...it can be shown that the winglet's sole effect on aerodynamics of a wing is an equivalent increase in span. A perfectly designed winglet will do this but very hard to design so most of the time they ending up hurting more than helping.