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Old Dec 03, 2008, 04:58 PM
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Scratch Built F-35 EPP Slope Soarer

Here is my current project. An F-35 Joint Strike Fighter in EPP for Slope Soaring.

The screenshot is from an early CAD model. Construction of the fuse is done by slicing it into 50mm sections in CAD, outputting these to my CNC hot wire and then gluing them together.

Yes, I know it is missing its rudders at the moment. Like I said, this is an early CAD model.

Wings are cut in the usual manner although I may have to do them in two peices (inboard and outboard halves) due to the extreme angles caused by the massive root airfoil compared to the tip.

Construction is progressing a little slowly but I'll post some pictures shortly.


Regards
Marty
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Last edited by mravell; Dec 03, 2008 at 05:37 PM.
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Old Dec 03, 2008, 05:16 PM
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Slices

So, for the fuselage the process is a little tedious. There are a total of 22 slices. Here are a couple of those.

They are bulkheads 8 to 9 and 9 to 10 I think.
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Old Dec 03, 2008, 05:26 PM
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Stacking the slices is progressing nicely.

Aluminium tube has been inserted for wing spars to slide into. I cut the holes for these with the hot wire as well.

The slices around the LE of the wing have been built with slightly different sections so that they can be sanded to a better curve. I used tangents to the airfoil curve to plot the endpoints of the slices..

Note this fuse is a prototype in expanded polystyrene. Final model is to be in EPP for combat duties!
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Old Dec 03, 2008, 05:37 PM
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Nice work there Marty! I have a CNC wire cutter and have yet to spend the time to learn how to carve up a fuse like that. Any tips for the noobies to learn from?

EB
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Old Dec 03, 2008, 05:51 PM
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Depends on your CAD program.

I'm using Rhino outputting DXF for GMFC.

Takes a fair bit of practice to get it just right. Although I now use scripting with Rhino to prepare the DXF files that are then used in GMFC.

The big trick is to get your DXF files to have only a single polyline. I use a large number of points (say 2000) evenly distributed over the top and bottom parts of each curve. You need to do this exactly the same way for each subsequent bulkhead or GMFC come up with a "Differing number of point between root and tip" error.

Hence my preference for scripts to do the preparing and then exporting.
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Old Dec 03, 2008, 05:56 PM
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Here is a sample CAD file. There is one of these for each of the bulkheads.
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Old Dec 03, 2008, 06:37 PM
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See, that's where I fall short-CAD. I have an old copy of Solidworks, but not a clue how to use it. I need to get my brother, the engineer, over to give me a crash course.

I'll be watching your progress.

Thanks,
EB
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Old Dec 03, 2008, 07:21 PM
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I've been told that Solidworks is the dogs bo11ocks. Better than Rhino.

Quite different from Rhino in turms of usage but supposedly more powerful.

I taught myself Rhino without too much trouble. Then learnt how to write VB script that Rhino uses for automation. I am a programmer by trade though so your mileage may vary.

Having said that though, what you are doing for foam cutting in CAD is pretty simple stuff. You create a curve matching the shape you want. Export the shape as DXF. If you are using the same shape on both sides of your cut that is pretty much it. Import into GMFC or your foam cutting software of choice and away you go.

If you are doing different shapes (root and tip) divide them by a set number of sections, fit a polyline to the resultant points and save to DXF. The trick is to get the same number of points root ant tip. I typically divide my curves into top and bottom first, divide them by a set number and then join them back after I fit polylines to both.
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Old Dec 03, 2008, 08:49 PM
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You have my attention.

Nauga,
heartened by some of the recent builds
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Old Apr 14, 2009, 08:23 AM
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Any more info on how to get a single polyline? I'm fiddling with gmfc pro and rhino now, and even when autocad shows the shape as a single polyline (saving in r12 natural from rhino) gmfc doesn't accept the file.
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Old Apr 14, 2009, 08:35 AM
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I have been fiddling around too and that is the error that I always get, the single polyline rejection. Any ideas on how to correct that?
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Old Apr 14, 2009, 09:13 AM
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I found you can draw whatever you want (make sure you are in MM mode) in Rhino. Then join the whole thing, then you can use the convert to convert the shape to line, then save as dxf (r12 - natural).

So far all the things I've brought in as tests have worked (all this done this morning). I haven't done the different tip and root shape stuff to see about the # of points per line like was discussed above.
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Old Apr 14, 2009, 10:25 AM
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Quote:
Originally Posted by Sleedo
I have been fiddling around too and that is the error that I always get, the single polyline rejection. Any ideas on how to correct that?
I'm hoping to see a clear answer...I use the 'hands-on' method and "profscan." If there's an easier way to do it I wannna know, 'cause I've got several designs I'd like to section fuses for but don't have time for the profscan method.

Nauga,
and his compound curves
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Old Apr 14, 2009, 02:18 PM
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I find its simple I use pencil and paper.exe
SteveW who'd like to send his Rhino back to Africa
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Old Apr 14, 2009, 11:32 PM
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I went over a friends today and fiddled some with putting the dxf files into GMFC to cut, and ran some cuts.

Now I eagerly await more info on how to make it work right from Marty.
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