I've assumed that the slope at the leading edge point would be zero, which the "control points curve" or "through points interpcurve" do not seem to accomplish.
Played around with creating multiple points on the leading edge radius, with array curve, and using them for "control points curve" or "through points interpcurve".
Blue = through points using the extra points.
Black = current method, control points starting at tangent point.
Red = control points starting with the extra radius array points.
Need to LEARN how to calculate MidPoint of a line, given the two endpoints, which should be easy.
There is already a MoI script, "DoArcCenter". Mainly need to LEARN how to substitute existing points, for PointPicker
There already exists a MoI script, "DoIntersect", just need LEARN how to substitute the two arcs for ObjectPicker list, somehow, which a good programmer could do easily. :-)
the naca points stop short of the leading edge radius. this is the problem really. if they extended out enough then you probably could have some sort of shape that you could then fillet after the fact. but you can't have a smooth continuous spline without a few extra steps. i have a screencast showing how i do it. you and michael actually helped me determine that process awhile back. it works great. i have no problem at all doing it manually. i just thought it would be nice for new users of prop_design and moi to have a script. its asking them to learn an aweful lot without it. you have to learn prop_design and moi and then figure out how to model the blade in moi otherwise. this way its a lot easier on a new user.
if the airfoil generation is a problem, I should be able to manually figure out where the missing points need to be and redefine the array so all you have to do is curve fit it. i would just need a few days to test it out and so forth. is this something you would want me to do or are you ok trying to do things another way.
i went ahead and found the tangent points needed. so this elimates that work for you. you can now just import the points and curve fit it. you still need to use them as control points rather than through points. going over it i noticed i took out one point for the same reason you have to use them as control points. the naca data points are just plain off some. so these two changes get them to work out nice. i moved the points to make the arcs at the end of the table for you. give this a shot. you should be able to directly make a spline from the data then just lay in the last four points. a simple mirror and two arc commands followed by a join and sweep will finish the model. same method as before, just don't have to find and add the tangent points.
The leading edge is not a circle. Its radius is as specified only at point zero on the X. The curve has a constantly changing radius away from 0, which a circle or arc does not. It's a pity MoI does not have a curvature radius display then it would be more obvious what I am talking about. An ellipse is a better approximation than a circle. Indeed it is suggested that a tilted ellipse is the way to get the first section of the aerofoil. You do not want tangent connections either. They must be G2 curvature continous at the very least.
everything I have seen from naca shows the le as a circle, including the blue Bible. do you have naca documents or experience regarding your assertions. I have worked for two different propeller manufacturers and the le was a circle tangent to the rest of the data. I'm not interested in noncontructive information. Your free to model things however you like. I enjoy the same frerdom. Frankly I'm tired of responding to your posts.
Anthony, would you please confirm the AFXTAB and AFYTAB data, in particular, the last 6 points, in each array, as follows:
"X & Y" Elements 24: Leading Edge "tangent" point, end of arc radius, and also the starting control point, of the curve "spline".
"X & Y" Elements 25: Trailing Edge "tangent" point, end of arc radius, and also the ending control point, of the curve "spline".
"X & Y" Elements 26: Leading Edge "uppermost arc radius start" point.
"X & Y" Elements 27: Leading Edge "arc radius center" point.
"X & Y" Elements 28: Trailing Edge "lowermost arc radius start" point.
"X & Y" Elements 29: Trailing Edge "arc radius center" point.
I will enter the first and last points of the "spline", again, (a second time, in the order to be selected for spline), to simplify point selection in the for loop.
I read over the articles you are referencing. They state that the original definition contained circles:
"The values of leading-edge radius of the derived airfoils, published in references 9 to 12, were initially determined by plotting
the ordinates to a large scale and fairing in the best circle fit by hand."
I know from many documents and experience that the le and te are based on circles of a specified radius, made tagent to the rest of the airfoil definition. Perhaps you are confusing what some NASA engineers are doing in a Fortran code 50 years later to what the original designers specified. I am using the original NACA 65A009 definition. I am not going to recode this NACA Fortran code you are referencing. It offers me no benefit. There already exist many NACA airfoil plotting codes for one thing. I recommend Hanley Innovations VisualFoil Plus. You can not only plot the airfoil but get data for it at transonic speeds. I don't have $700 dollars to spend on it. Thus I am using the NACA definition and data.
I appreciate people trying to help. However, what you have been doing I do not perceive as help. Thus my frustration at this point. I am a retired engineer who has designed and worked on a number of real aircraft propellers. I am well aware of what I am doing. You can take that as hard heading if you like. When someone is insisting I am doing something wrong, I don't know how you would like me to take it. Plus, not showing how to do it supposedly right, until I request it. I have worked with a number of people that think being a road block is an accomplishment, that is how you are coming off to me.
No one needs to use this script if they don't want to. Nor develop it for that matter. I could care less. I thought it would be useful to people, thus the request. If you think its wrong, fine don't use it. But enough already. You are beating a dead horse.
Are you seeing something wrong with them? I ran two examples with them and they work out pretty could. I still think my original method is better, because there is no round-off error when you do it inside MoI. The points I added were determined using my original method. However, there is some round-off error. Visually, when I made the models to check the new points, I could not see anything horrible. As far as ripples or lumps.
The last four points are for the circles. The two points preceding the last for are the new tangent points. You can place them in any order you need.
Points X = 0.0D0, Y = 0.0D0 and X = 100.0D0, Y = 0.0D0 aren't really needed anymore. I left them there, they could be helpful. But you can make the arcs now without them. If you wanted it may be simplest to just make the airfoil arc from everything but the last six points. Then mirror that curve. The only thing left is the arcs and MoI may be able to do it without a center point. I haven't tried it that way, but want to next. If you wanted to leave the center points in, then I know you can definitely do it that way.
There is nothing wrong with your data, as far as I can tell. (except maybe the tangent points, see below :-( ) I just wanted to confirm that I had identified the points correctly.
I believe that the spline needs to start and end on the "tangent" points, which is why I put an extra copy of them back in the array, in the order in which the spline is created. So the "tangent" points have a dual purpose.
Attached is an updated Prop_DesignGeo, which incorporates your data as of 12/29/2011,
also creates and shows the control points for the rails.
To see the control points for the Airfoil, do "show points."
The control point spline runs from upper "tangent" point, to lower "tangent" point.
The user still needs to add the two arc radii.
Unfortunately, it appears that the two "tangent" points are just a little bit off, the arc radii do not quite intersect them...(zoom in).
(Or maybe I've made a mistake somewhere...)
(I've read how to calculate the tangent points manually, using either arctangents, or simple algebra, as a right triangle is created.)
Anyway, I think it is progress :-)
With the help Michael gave a few posts back, I think the "tangent" points can be created in the scripts, using either your "point line tangent to circle" method, or else the Thales method....
Being how we are not alone in the forum, I like to jump in and paticipate whether needed or requested.. It's how I learn stuff. It is not intended to direct anybody. It may be usful for someone reading the thread..
Here's how I have done airfoil curves using Conic sections:
Sometimes I use the blend tool also, when I want to use G2 and G3 Curvature.
I stuck the 0.75 and 0.835 points back in, and reran the tangent line and thales arc, which produce the blue
point on the attached png. The adjoining red point is your point. (I think this is correct....)
The two points are very close together...
Hi Brian,
Where the last scripts curve ends, an arc wont fit. An easy check is to use the arc-cont tool between the 2 points. The last 2 points of that arc should be planar. I wonder if the blue point would create one.
AlternativeMultipoint.PNG