DLG foam or hollow ellipse wings

[Glidergider]

Hi Glidergider!

I use a 1/4 straight bit and I compute my Gcodes using a 2mm step. I have installed a vacuum table on my hobby CNC router.The first set will take many hours. The values on the left when you start may be changed. They are close to what is used for the Blaster.

I'm thinking that you'd be better off if you used a 1/4 inch ball nose bit. Wouldn't you get a better leading edge with a ball nose?

Regarding the vacuum table, what pressure are you running?

[Glidergider]

Cocodet,
I'm not familiar with your terms Mhd Mhg Chd Ghg. Sorry for my confusion. Can you clarify?
Dave

Hi Glidergider!

First cut the molds of the top parts in foam or presswood (Mhd... and Mhg). Then drill holes in them with grooves on the underside, to allow for the vacuum from the table to go thru the mold. See how they do http://www.rcsoaringdigest.com/pdfs/...SD-2006-04.pdf and following issues. Then cut the top cores (Chd and Chg...) in foam leaving some material below Z0. Then cut with a knife the material around the grooved part and place Chd on Mhd. Then cut the bottom part of your wing with your CNC machine (Cbd and Cbg..). It takes more or less 45 minutes for each operation on the CNC machine. When the moulds are made it means 4 hours per set (3 hours of machining plus 1 hour for adjustments, thinking....) but the result is a much better DLG.
You may use the software to compute Gcodes for your stab and rudder then using "copy, replace..." with "wordpad" and your knowledge of Gcode you can have one only Gcode file for the whole stab or rudder. Since they are smaller it is faster to cut them and it could be a good training, this is my suggestion.
Sanding is limited, less than one hour per set. You still have to make the grooves for the carbon spars...
You may contact me directly if any more questions.
Hope you will enjoy your next home made DLG!

[cocodet]

Those are the first letters of the Gcode files my software is making. M is for mould, C for core, h for high (top part), b for bottom (lower part), g for left (gauche in french) and d is for right (droit in french); the numbers after reflect the numbers you gave for your wing, the last one is the step chosen so Mhd760130602.txt is the Gcode for the right top mold with a 760mm long half wing having 130mm in front of a 60mm flap (total width at root is 130 + 60 = 190mm) and computed with a 2mm step on y.

[cocodet]

I am using a straight 1/4" bit and my leading edge is perfect working with a 2mm step on y. I also have a 1/8" ball nose, but I think that to use it and have little to sand, I will need to go at 1mm step on y; that means much more machining time. For the mold, the precision is not really important if you want to cut foam wings (it is not the case if you want to build a hollow wing) because it is only to keep one side of the core in place while machining the other side.
My cnc router is a hobby router and i am getting the vacuum for my table from a vacuum cleaner. It is more than enough!

[juzwuz]

I'd be very interested in seeing a picture of your cnc router and some pictures of your wings and DLG's. Would you be able to make your source code available? I'd be interested to see how you model the wing in your code. What kind of foam do you use for your cores?

I'm interested to see if I can use the Vectric CUT3D software to generate the toolpaths for the wing and use the 2 sided cutting strategy with the wing held with tabs. That way, you mill out one side of the wing, turn the block over, and mill the other side of the wing. Then manually cut the tabs to loosen the wing from the block of foam.

[cocodet]

I purchased my CNC router on Ebay. You may contact the builder at jeffberch@sbcglobal.net. I changed his table for my vacuum table. I am most happy with this machine. He has put its machine on youtube and you could ask Jeff its references.
I do not have a digital camera. My last DLGs are similar to the Blaster. I am using low density blue construction foam for the cores. It has to be strongly held to stay straight and I doubt you can cut a wing the way you plan to. The profiles used are those I gave before. On the files taken directly from Profili, the first x coordinate shows a negative y while it should be positive but it has minimal consequences.
The wing is made with 2 ellipses computed: one for the front part (130mm width, 760mm long) and one for the back (60mm width, 760mm long) which becomes the flap. Then as we go from the root to the tip, the profile is more and more like the tip profile and less and less like the root profile; you may see them using the rib button and the value below it. The AGcoord file made by my software is the file showing the profiles one after an other (Y X Z for the top then Y X Z for the bottom).
The files (Mhd.. Mbd.. Mhg Mbg Chc Cbd Chg Cbg) are the Gcode for the coordinates you need (M for moulds, C for cores). You have to add the general indications to your machine; for example just add the following in front of one of the M.. files and see your CNC router do the job (I do not need to tell more to my router):
M90
G90
G21
F2000
G00 Z20
G00 x0 y0
G01 Z00 (Change this value for the top of the surface)
M00 (Stop)
G00 z20
g00 z00 (On surface)
M00 (end adjustments)
F2000
G01
(Here insert one of the M.. file then add M02 at the end)

If you have more questions you may contact me directly.

[harpia]

I have written a VB software which computes coordinates of ellipsoïdal wings then produces the Gcode (as txt files) of those coordinates needed to cut or mould the wings. One has to add the general instructions to its CNC router (feed, units used that is millimeter....). It does not take the size of the router bit into account. The profiles used are txt files from "profili".

I also have written a similar software to produce "Drela" type wings with a CNC router instead of a hot-wire machine.

Any body interested?

I am very interested.
I built a CNC router to cut foam wing cores and my great difficulty was drawing in 3D an elliptical wings.

Thanks for your good software

Edson

[harpia]

Hi Cocodet
What software I can use to convert dat files to use with your software? The dat files that your software read is diferent of Profilli dat files.


Edson

[cocodet]

On profili click on airfoil database (small yellow airfoil), then pick your air foil and chose export as a .txt file. See attached picture. Be carefull, for one reason I do not know, sometimes the first coordinate shows a negative value while it should be positive.

[cocodet]

Does any one knows a guy who could machine aluminium moulds in 3/4" thick plates for my wings? I am ready to pay for it if not too expensive. Please contact me directly at cocodet@vl.videotron.ca

[robust]

This software (profdlg) is computing ellipsoïdal wings using Drela's profile or others if so you wish, then produces the Gcode needed to cut them with a CNC router. My experience is that those ellipsoïdal wings give better performance than regular Drela's wing. Supposedly the spitfire had such type of wings and was better than those aircrafts with straight wings. I have attached the soft which computes Drela's type wings, that is a wing originally in two straight sections. Take AG47 for tip and AG 455 for root and run it step by step. You will have a wing close to Drela's. Usually one cuts such wings with a hot wire and templates made using the Profili software. Good luck.

Hi Cocodet,

You done the great job! And I just confused that on SuperGee2's design the wing has 3 prosiles: AG455ct (root), AG46ct (middle) and AG47ct (tip). In you software could just input root and tip.

Thanks