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Old Dec 05, 2012, 08:32 PM
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Foam cutting service

Anyone know of a service that will cut a solid foam fuselage for you? I can cut wings, but the fuse is going to be a pain. I am wanting to create a mold for an all composite 120mm fan size F-100. I already have the 3d model, just need the fuselage cut.....I have no problem gluing togehter sections and doing final shaping if needed, but I am having a rough time figuring out how to hotwire it as a starting point.. I tried breaking it onto secitons, but this leaves an unscale outline, due to th curvature of the fuselage....any suggestions?
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Old Dec 05, 2012, 09:01 PM
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What length sections did you use? Lots of people have been using the section method lately in this forum and it handles curved fuses very well. Check out the SU-25 Frogfoot and the Chimera builds (among others) for details. Sections range from 1" to 3" in length. If you have a 3D model, you have everything you need.
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Old Dec 05, 2012, 09:06 PM
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about 8 inch sections.. guess I need to section it off more... its a fairly large airframe, didnt want to have to do that many sections, but if I have to I will
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Old Dec 05, 2012, 09:23 PM
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Actually the number of sections and not the size is the important thing. With a larger airframe, the sections will of course be longer than a smaller one. By coincidence I'm working on an F-100 too, mine is for 90mm though. What are you using for CAD? I'm using Sketchup.
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Old Dec 05, 2012, 09:23 PM
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autocad inventor
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Old Dec 05, 2012, 09:27 PM
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Darn! I guess I have to keep plugging away then...
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Old Dec 05, 2012, 09:38 PM
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whats your overall length for the 90mm?
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Old Dec 05, 2012, 11:13 PM
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Fuse is 62" and span is 52".
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Old Dec 07, 2012, 02:00 PM
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If there is a lot of contours and tight curves use smaller sections.
There is no reason not to use different spacing per your liking in the same model. Mix and match for detail as needed.
Might depend on tooling as well. I can only cut up to 5" straight and 3 1/2" at a 45 degrees with my hand tool. And
Scroll Saw
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Old Dec 07, 2012, 02:16 PM
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I've decided to buy/build a CNC router... since I have intentions of doing many scratch builds after this one
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Old Dec 07, 2012, 02:41 PM
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Klaus showed a cnc hot wire cutter with two heads. This was in his Saab 35 Darken thread. Seems like a very nice way to go from CAD directly to parts. If you're building lots of prototypes, might be the way to go.

Cheers,

Phil
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Old Dec 07, 2012, 04:53 PM
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Quote:
Originally Posted by BillO View Post
By coincidence I'm working on an F-100 too, mine is for 90mm though. .
Quote:
Originally Posted by BillO View Post
Fuse is 62" and span is 52".
What is estimated weight? Also, have you decided on what fan/motor combo you will use?

While I'm waiting to finish my F-86F, thought I'd build sport foamy about the same size for my JetFan 90. Just like to see what others are using.
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Old Dec 07, 2012, 09:33 PM
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I haven't done a proper weight estimate, but I'm hoping about 5 lbs for the airframe and 5 lbs for the gear for a total of 10-12 lbs.

As for fan/motor, something nice like a Jetfan or Stumax. I'm thinking 10s so that will drive the motor choice. Nothing definite yet though. I was hoping to see how yours turns out!
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Old Dec 07, 2012, 10:39 PM
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BillO

I have been doing a little comparison shopping if you will. What motor/fan combo's give you what kind of perfomance. What stuck me in this video was the sound, but also his set-up.
http://www.rcgroups.com/forums/showp...&postcount=545

I PM'd Emile for other specs not in post. Here's what he got.

I'm using 1,5 year old Turnigy Nanotech 4s5000 (45c/90c) 2x.
This setup pulls about 110amps at 3,250KW.
It's hard to say how much thrust it generates.
Inflight the Jetfan produces visibly more then shown in the graphs of ejets. I experience similar in my Habu
This should push your F-100 right along!

Food for thought. Good luck on your build.
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Old Dec 10, 2012, 10:47 PM
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check out this foam cutter http://www.rcgroups.com/forums/showthread.php?t=1618001
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