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Old May 10, 2014, 11:12 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Entropy build thread.

I've been working on the concept of a 2.8 mtr fully moulded slope plane for front side aerobatics. I now have a basic understanding of CAD drawing using LibreCad as I've been learning it since I first downloaded the program in Jan 26 this year. It's been a rapid learning curve, but very rewarding. Thanks to the assistance of other experienced users here in my town and from the other side of the world!

Basic parameters:

2.8 mtr span
Fuse length: 1625mm
Airfoils: TP42/29 blend.
Full flying stab.
Two part wing and two part stab (of course).

The fuselage plug will be turned out of timber, probably Meranti. I'm advised that our local Coachwood would be ideal, but as yet I don't have a source for it. I could also use laminated MDF, but I don't know how that will turn. The flying surface plugs will be hand shaped out of MDF copying the technique developed by Kevin Bennett and described in his Afterburner build thread.
For a while I was stuck trying to find a wood lathe with a long enough bed to turn the fuse. It turned out that my flying buddy Andrew had one all along and is organising access to it for me. Got me out a possible hitch in the whole project.
I'll try and post my draft drawings here in the .dxf file, don't know if it will work.

More as the project develops.........

edit: The .dxf file did not load; I'll convert it and try again. - I have to find out how to do this.
2nd edit:
I've just posted a question over on the CAD forums for some guidance on how to do this.

edit:
I've found out how to convert my .dxf files to .jpg files for posting here.
Also, due to the numerous drawing errors in early drafts of the drawing, I've chosen to delete them and replace with the updated draft #7.pdf in these early reports.

Jim.
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Last edited by Jim.Thompson; May 21, 2014 at 03:56 PM. Reason: See edits.
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Old May 11, 2014, 02:34 AM
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Tehachapi Jim's Avatar
United States, CA, Tehachapi
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Sounds exciting Jim, I for one am interested in your process. OK, the plane too!

Jim
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Old May 11, 2014, 05:04 AM
I hate propellors
emufingers's Avatar
Australia, SA, Normanville
Joined May 2009
374 Posts
MDF turns well for a plug, providing you keep your chisels sharp. Blunt chisels leave marks, but if you turn oversize MDF sands easily back to size. It is also possible to apply epoxy like you do for moulds and polish up on the lathe.
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Old May 11, 2014, 09:14 AM
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,219 Posts
Careful of whip if the MDF blank you are turning is very long. MDF is like a noodle if it is any length at all. It can get dangerous fast.

You are going to need a steady (steady rest). I dislike turning long items with a steady as it transfers workpiece errors to the working surface but it is necessary sometimes.

Sharp tools are a must as has been noted. But MDF sands so quickly that a sanding board will bring you to the finished surface from oversize pretty fast.

Tom
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Old May 11, 2014, 03:26 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Mdf

Thanks for the comments on MDF for turning Jerry and Tom.
As the size of my fuse will be 74mm max diameter and 1650mm long, I think the potential for flex and whip will be great if MDF is used. So, I think I will try a softwood such as Meranti first up. I will still look for a seasoned piece of coachwood as I am advised that is about ideal.
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Old May 11, 2014, 05:00 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
6,553 Posts
Zipped file of drawing.

I have compressed the .dxf file into a .dxf.zip file.
I hope it is readable. Please provide feedback.

edit: This is the latest draft.
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Last edited by Jim.Thompson; May 21, 2014 at 03:59 PM. Reason: See edit.
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Old May 11, 2014, 05:04 PM
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United States, CA, Tehachapi
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I have read more than once to insert a stiff rod in the middle if using MDF for the plug Jim. Makes sense to me, you get the benefits of an easy, workable material and stiffness too. I am rough g my first plug today. I am using a carbon rod or a dowel, whichever will work best in the middle to stiffen the MDF. Just route the groove out and glue it. Its what I have on hand instead of driving to town. I will try to post some pics tomorrow if I get that far, It will be a fuse for a 2M+/- wingeron.

FWIW,

Jim
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Old May 11, 2014, 05:13 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
6,553 Posts
That's a creative idea Jim! Thanks. In this case, a length of heavy wall thickness steel pipe might be the go?
Yes, please post any pics of your plug manufacture sequence.
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Old May 11, 2014, 09:04 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Pdf version of the drawing.

I've learned how to convert my .dxf file out of LibreCad into a more universally viewable .pdf document.
Lets see what this one looks like now:
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Last edited by Jim.Thompson; May 21, 2014 at 04:00 PM.
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Old May 12, 2014, 12:53 AM
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Tehachapi Jim's Avatar
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Jim, I like it. It looks amazingly similar to my own design. I am not so hi tech though, mine is on graph paper. I like the longer nose moment, and that you have moved the hor. stab up onto the vert. stab. Much more durable, and much cleaner aerodynamically.

Question, if your thinking of aerobatics, maybe a little more side area in the fuse (not a criticism, I prefer it the way it is). It would make a great wingeron

Jim
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Old May 12, 2014, 01:16 AM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Quote:
Originally Posted by Tehachapi Jim View Post
Jim, I like it. It looks amazingly similar to my own design. I am not so hi tech though, mine is on graph paper. I like the longer nose moment, and that you have moved the hor. stab up onto the vert. stab. Much more durable, and much cleaner aerodynamically.
Have you tried to learn one of the CAD drawing program? I'm learning LibreCad 2D. Lot of work, but good fun and very rewarding.
Quote:
Originally Posted by Tehachapi Jim
Question, if your thinking of aerobatics, maybe a little more side area in the fuse (not a criticism, I prefer it the way it is). It would make a great wingeron
Jim
Sorry, but I'm too much of an old traditionalist for either of those suggestions. I can't get luke warm interested in planes with wings that twist. Seems too counterintuitive to me. (not just an old traditionalist, just plain old!).

edit: The plan that you see above is the result of 3 months learning LibreCad. I mainly relied on the forums and a very basic manual to get started. However, a local friend who was a draftsman all his working life has helped me a great deal with the more subtle details. I've been lucky.
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Old May 12, 2014, 04:28 AM
Twisted and Confused
flyonline's Avatar
Joined May 2003
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Quote:
Originally Posted by Jim.Thompson View Post

Sorry, but I'm too much of an old traditionalist for either of those suggestions. I can't get luke warm interested in planes with wings that twist. Seems too counterintuitive to me. (not just an old traditionalist, just plain old!).


Go wash your mouth out, you... you...... you...... anti-fetishist

Steve
Pro-fetish from way back


p.s. looks good otherwise
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Old May 12, 2014, 05:38 AM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Hey! It's good to hear from you Steve. Have you got that "super shed" into commission yet?
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Old May 12, 2014, 10:08 AM
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Tehachapi Jim's Avatar
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I am with Steve! I know you dont like twisty's Jim, which is a shame, and I am profoundly sorry you are sol old and set in your traditionalist ways
In truth, I like traditional gliders as well, I just have a particular like for twisty's.

I have not tried CAD, but it sounds fun. Maybe I can play with some samples today, I am home from work dealing with this cursed auto immune disease.

Jim
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Old May 12, 2014, 03:25 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Quote:
Originally Posted by Tehachapi Jim View Post
................ I am profoundly sorry you are sol old and set in your traditionalist ways
.........................
Jim
Yeah, it's not fair is it Jim. Youth is wasted on the young, as Oscar Wilde said (I think).
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