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Old Mar 22, 2010, 03:14 PM
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Hair Pulling Sessions

Hi Erazz,
After reading your thread, I am still having real big problems, with using the converted text files. I have tried to model a new tailplane mold for heli_bee, but the problem is when coming to split the mold. On further investgation, I have found that the aerofoil trailing edge is jaggered and so is the rest of airfoil. I have tried numerous methods, but still no luck.
I have tried using a different aerofoil file, still no luck.
See attached file for your viewing.
Getting the point of calling it a day, and reverting back to using Autocad.
Steve 827
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Old Mar 23, 2010, 01:51 AM
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Hi Steve,

The problem was that the airfoil file was not "continuous" but segmented into 2 parts.

What I mean is when you look at the files I used the airfoil file coordinates went from front to back through the top and return to the front through the bottom. This makes for a continuous "loop".

In your file the top curve goes from front to back and then again from front to back. this makes the curve split in the middle. The solution is simple, split the file into two curves - top and bottom. Insert those and convert them to a single sketch.

I've added the files to show what I mean.

p.s. Please note that the file you posted results in a 100mm airfoil. You need to resize it accordingly so you don't get a too-large airfoil.



btw. anybody who has found this thread helpful is welcomed to post his/her work. I bet there's a lot of interesting stuff to learn from all.
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Last edited by erazz; Mar 23, 2010 at 01:54 AM. Reason: Remembered the airfoil size issue.
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Old Mar 23, 2010, 07:31 PM
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United States, SC, Myrtle Beach
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erazz

I will post as soon as I figure it all out. I am also very new to S/W and try to follow what your doing, but have problem. I hope it will come to me soon.

Roger
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Old Mar 28, 2010, 07:35 AM
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Hi guys,

Finally got the wings to the CNC. Hope to have pictures soon
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Old Mar 30, 2010, 01:08 PM
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Hi Erazz,
I have final solved the problem, thanks for help. Now just to solve the sweep base/boss in loft section in Solidworks.
Many thanks.
Steve827
Quote:
Originally Posted by erazz View Post
Hi Steve,

The problem was that the airfoil file was not "continuous" but segmented into 2 parts.

What I mean is when you look at the files I used the airfoil file coordinates went from front to back through the top and return to the front through the bottom. This makes for a continuous "loop".

In your file the top curve goes from front to back and then again from front to back. this makes the curve split in the middle. The solution is simple, split the file into two curves - top and bottom. Insert those and convert them to a single sketch.

I've added the files to show what I mean.

p.s. Please note that the file you posted results in a 100mm airfoil. You need to resize it accordingly so you don't get a too-large airfoil.



btw. anybody who has found this thread helpful is welcomed to post his/her work. I bet there's a lot of interesting stuff to learn from all.
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Old Mar 30, 2010, 02:57 PM
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Hi Guys,

Got the cnc work done. Now need to finish and polish....

Here's some pictures:




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Old Mar 31, 2010, 04:38 PM
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Erazz,

I'm very jealous, the moulds look great.

I have been having some success with my attempts to make moulds from your drawings. The reduction in the stepover size has made a vast improvement in the quality of cut that I can achieve. Today I did a finishing cut on the resined MDF. It looks impressive, however my mould needs to be resined again and the finishing cut re-run. This is because the resined surface has higlighted the fact that my table is not completely level. I need to take another 0.1-0.2mm off the top.

Unfortunately I will not be able to do this for a while, at least until I get my own workshop built. At the club EGM this evening it was highlighted that my machine is not registered with the building's owner, needs PAT testing and a more efficient dust extraction system attached to it!!!

Don't you just love club politics and the associated Health and Safety rules?

Anyway, tomorrow I hope to post a photo of my progress so far. Keep up the good work, and I can't wait to see how you finish the aluminium moulds and how you laminate up fin, tail and wings.

Regards,

Martin.
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Old Apr 03, 2010, 02:46 PM
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Progress Photos

Hi Guys,

attached are the promised photos, later than promised. My apologies. Sorry for the slight rant in my previous post, but I would have thought that "my" club would have considered a CNC machine to be an asset and not a liability. Their loss!! There are a number of companies that will charge them for cutting parts out!! Rant over!

I will keep following this post and inform you of my progress as it happens.

Regards,

Martin
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Old Apr 04, 2010, 01:40 AM
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Already looking much better!

The change in the direction of cut has also improved the result. You might want to try and coat the top of the mould with gelcoat and mill that. Though the epoxy filled MDF is really stable it's also porous.

I'd also coat all of the exposed MDF with at least one coat of epoxy so that moisture doesn't get in and expand the mould.
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Old Apr 14, 2010, 02:05 AM
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Polishing...





Before and after polishing...
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Last edited by erazz; Apr 14, 2010 at 02:11 AM.
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Old Apr 19, 2010, 08:23 AM
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That looks so good!
Eitan.
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Old Apr 28, 2010, 10:57 AM
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Not quite ready to layup the wings (waiting for some Kevlar) but in the meantime here's the next project

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Old May 01, 2010, 03:04 PM
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Whitchurch,Shropshire. UK
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Looking forward to seeing some photos of the laying up process in the wing moulds.
The finish on the prop moulds looks excellent.
Do you get the moulds hard anodised to help protect them after polishing ?

Chris
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Old May 01, 2010, 10:51 PM
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Thanks but I must admit that the finish on the prop mould is great because it's a computer generated image. Still need to mill those out

I don't like anodizing. It messes up the surface. I've been told that you can't anodize a polished surface and I'm not sure how well you can polish it after anodizing. Doesn't matter much though. Aluminium is much harder than even the best gelcoat. With proper use these molds should last a long time.
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Old May 02, 2010, 12:16 PM
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Hegra, Norway
Joined Feb 2007
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Great work!
The prop mold is very interesting, can you post a cross section at mid-span of the closed mold, so we can see how the two parts fit together?
Are there resin channels?

Lars
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