ProfLooney

I am designing an ME 109 and sent my cad files to get me a fuse kit laser cut and tonight as i framed it up to check it, the former widths were correct and look really nice with stringers on them but the bottom of the rear formers and the top of a couple of the rear formers are too short. I made 17 formers and a finpost figureing as i worked on the structure i can figure out for the plans which formers to leave out. looks kike formers 1-11 are good but 12 on they seem a little wavy. anyone good at lofting can give me some advice or help?

Joe

digsy

Not really any help - more a question.

Where did you get them cut ? And did it cost mega $$$ ?

Highflight

My Feedback: (4)

You COULD perform actual lofting procedures to get your rear formers right, but there's a much faster, easier and better way.
On most aircraft, the height and width ratio of each successive former changes but the basic shape remains the same. That's key.

In most cases, all you need to do is design ONE former and turn that into a BLOCK.
Now write down the height and width of each of the formers in the fuse and INSERT your BLOCK back into the drawing specifying each individual height and width of each of the formers.

The CAD software will take care of the rest and you'll have perfect transition from one former to another. You'll have to EXPLODE each of the formers before exporting them to a CNC cutter.

In the occasional instance where the general shape of the fuse actually DOES change (like from a perfectly round nose to a rectangular former behind it), what you would do there is to set up the two shapes in 3D in a spatially correct position to each other that is the same as their positions in the fuse itself.
Then RULESURF or EDGESURF the two of them depending on the situation, then do a SLICE right where a former would be located between them on the fuse.
Use that SLICE as the shape of that former and you'll have your perfect transition between the two different shapes.

'Zat help?
Highflight

ProfLooney

I have a friend that laser cuts kits and he did it for me. http://www.laserlizard.com He didnt charge me as he is trying to help me get the plans done and i do some vectoring for him occasionally.

joe

ProfLooney

Highflight you lost me totally hahaha basically I think I get what your saying so here it goes: when I have the same shape in a section of the fuse ie the rear where the same shape seems to run the length. I make 1 former and then where I wanted the rest of the formers to be placed I resize the height of the former and then take the percentage i had to enlarge/reduce the height by and adjust the width by the same amount to be proportional on the former, then just do that for every place I wanted a former?

As for the rest of what ya said ya got me I am not a cad whiz I just know enough to create vectors for the laser from already drawn plans and to correct them for semetry etc. and how to draw basic lines shapes etc all using Corel Draw.

I did find my problem last night after a couple beers to help make me see things better :0) what I did was to put the notches that slide over the crutch in the wrong place, once i adjust that it should be pretty good although i still want to figure out ways to loft better than hit and miss. The way I am doing this is like the way dave platt showed on one of his videos. I also have plans I am working on for a lockheed hudson bomber that his method of lofting doesnt work since the fuse shape is not oval but has more of a box shape with oval top and bottom but thats another project altogether.

But back to my main question bsides what i just mentioned about the adjusting the size and that is how to actually loft a former with a top and side view as a HOW TO FOR DUMMIES

thanks guys for any help
Joe

Highflight

My Feedback: (4)

The one thing you may not be clear about (from how you describe your understanding of what I said earlier) is in the "resizing" of the basic former shape.

When you use the term "resize", that implies using the SCALE command. But reSCALEing changes only the scale _size_ of the entire part (X and Y _equally_ in proportion) where you need to change the proportional difference of X and Y to different sizes for each of the different formers.

You can only do that by making a BLOCK and then reinserting it because when you SCALE something, you are only prompted for a single scale factor.
But when you reINSERT a BLOCK, you are prompted for both the X and the Y dimensions separately. While a fuselage will maintain it's same general shape along most of it's length, the height and width of each former are not usually going to be proportionately the same throughout.

As far as the notches go; I draw them in as part of the formers when I'm designing the aircraft so they pretty much line up themselves once the parts are cut.

Any better?

Highflight

ProfLooney

yea better i reread the other thread and see what ya mean about height and width. I dont know about the block thing but Corel has a feature that lets me input x and y seperately and will work fine for that. as for notches I make me a box bigger than the former and in it I have lines drawn at either every 10 deg or every 15 deg then i just overlay it over the formers and just mark off my notch locations and comes out pretty good that way too.

Joe

captjack

My Feedback: (3)

highflight
agree with you on the lofting but the terms you are using change with the cad program being used.i use designcad 3k
i use the zoom command to scale both the x and y axis the same amount and the scale command gives me the x and y axis independently.

ProfLooney

and I use Corel draw and i just have to dup the parts then whenever I click on something it shows x and y on the top menu and the percentage and the dimensions and i just type in the new dimension I want OR there are pull tabs on top and bottom of parts you can just pul or squish to the desired height or width all independent of each other. Now if i need to scale something say 150% i have to type in 150 for both x and y seperately

Joe

Highflight

My Feedback: (4)

capn jack,
Any reference to "zoom" in ANY cad program always refers to a view, not any manipulation of an entity.

There's something funny going on with Designcad if any part of the zoom command changes entities.

Highflight

captjack

My Feedback: (3)

highflight
was not refering to zoom veiw command here is the pasted command description from the command help memu itself.
i may have confused you when i did not specify selection edit zoom command.

Menu: EDIT

Submenu: SELECTION
Menu Command: ZOOM

Toolbox Icon:

The Selection Zoom command zooms, or scales, selected entities to be larger or smaller. It is similar to the Scale command, but it changes the X and Y (also Z for three-dimensional object) scales the same amount. This keeps the proportions of the object intact.

Using the Command

Select the object to be zoomed. Choose ZOOM from the SELECTION submenu in the EDIT menu. Enter the Zoom Factor in the ZOOM FACTOR box in the dialog box. Press the Enter key. The object will be redrawn to the new Zoom Factor.