|Apr 13, 2009, 11:56 AM|
F-9 Panther scratch build from SketchUp **Successful Flight**
A while back I was looking for plans for a F-9 Panther parkjet and found only a couple of builds and not many plans. So I figured I could make this my first scratch build project. Since then Hobby Lobby started selling a F-9. RC Lander came out with a great version and Beanie started a build. Well Ö.. better late than never.
Iíll get started.
Ported 3 views into SketchUp and built a model from that.
|Apr 13, 2009, 12:32 PM|
Making plans from the model
The concept is to build an airplane with 2 inch thick insulation foam. A SketchUp model can be sliced up into even increments to create cross section templates. These can then be used to hotwire cut the foam sections. Sections can be glued together to then create an airplane.
SketchUp is a free 3D modeling software you can get from Google.
There is a 3D warehouse that you can down load models from if you donít want to build your own. There are plenty of airplanes modeled but I could not find an F-9 and thus created my own.
There are a couple of threads here in RC Groups that can give you more information about how to use SketchUp to model airplanes
And there is SketchUp for Dummies with tutorials on the basics
Here are some specific to building airplanes
View the videos by Crash, kram242 and AnyAirRc of them using SketchUp
to create 3D models of aircraft, then unfolding the model to have flat
parts to print as patterns to cut out the actually flying RC model
Ruby scripts are available to automate some tasks. There is a slice plugin that I used to slice my model in even 2 inch increments then lay them flat so plans can be printed.
Must have Sketchup Scripts/Plugins - these are used in the above
Examples: jf_unfoldtool.rb, progressbar.rb, weld.rb,
SketchUp screenshots of F6F Hellcat and FW-190 unfolded, ready to print.
|Apr 13, 2009, 12:39 PM|
Slicing the model
After the model was built and scaled, I used a Sketchup plugin that slices it in even increment. The plugin also puts all the cross section slices on the same plane. I then cleaned them up and got them ready to print. BTW, none of this is easy. To get the plugin to work I had to orient the model in the Z axis. Lots of clean up and rearranging before printing. Printing to the right scale is difficult. Instructions are in a post on one of the other threads. I will include it here later on in the build. I will also post the plans once I have a flying model.
Here are some more pictures
|Apr 15, 2009, 11:18 AM|
Started cutting sections.
Foam must be squared up and marked with a line on 3 sides to ensure proper template alignment.
|Apr 15, 2009, 12:27 PM|
Very interesting. I've seen something like this done for a large scale B17 one time. I will be watching with interest. What kind of foam wire cutter are you using? Is it the standard $20ish one that I've seen at Hobby Stores and JoAnn Fabrics? Seems that would work for 2 inch increments that aren't to large. Just curious.
|Apr 15, 2009, 03:42 PM|
To cut foam wing cores I made a cutting bow with 1/2 x 1" trim. It is hard to see but one end (left side of picture) is fixed and the other end can rotate to supply tension. Tension is from a rope (see picture).
|Apr 16, 2009, 12:03 PM|
SUBSCRIBED!!! Very nice work using SU. I've been trying to talk myself into learning this program and this is very inspiring. The F9 Panther is one of my favorit jets ever since I saw these pics from a Top Gun airshow here in Lake Land FL.
I can't wait for the plans. Best of luck on the build and on the maiden.
|Apr 16, 2009, 01:27 PM|
I just started teaching myself sketch up, Your links are a great help, thanks! I have only modeled a coffee mug so far but I can appreciate the great work you have done.
This is going to be a great thread to learn from, keep the posts a coming
Is this an edf or pusher? And do you have a wingspan?
|Apr 16, 2009, 03:31 PM|
So, to line up the templates you must have foam that is squared off on one end relative to the surface you pin the templates to. I leveled my work bench and let gravity pull the cutting bow straight down. That creates an even squared off cut Ö. Right?? Well it seemed like it worked for a few cuts, then the cuts started getting inconsistent. My guess is that the path of the hot wire is affected by gremlins. My second guess is that the grain of the foam and/or density variation play a part in the path of the wire.
What I do now is clamp the bow to my work bench, hold 2 carpenter squares on either side of the foam and use them to guide the wire and my hand as I pull the foam up. Obviously you need metal squares to guide a hot wire.
Lay a template down and mark a dot on the foam where the template center line is. Use a square to draw a line that connects on 3 sides of the foam. If every thing is square, the line on the bottom should be directly below the line on the top and the templates will line up just right. Itís been working for me.
|Apr 16, 2009, 06:54 PM|
LOL I am glad I am not the only one suffering from the gremlins I ended up doing the same thing with the squares, sure thought gravity would do all the work for me
|Apr 20, 2009, 11:22 AM|
Templates out the wazoo
Lots of work accomplished.
If I use this tecnique again in the future for an EDF version, I will work the ducting into the plans such that they can be cut with each section and eliminate the need for separate fabrication. I would guess that you would have to glue sections sequentialy and spackle the seams in the ducts as you go. I'll leave that issue for another day.
|Apr 23, 2009, 12:29 PM|
Hi Osprey Engineer,
Here are a couple of my and MarineA4 builds using this type of construction, I favor EDF and the ducting is cut at the time I cut the section as you have surmised. It works very well but is labor intensive at times with all the cuts.
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