HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 10, 2011, 04:05 AM
Registered User
Strasbourg
Joined May 2009
95 Posts
Discussion
Milling a wing mold of aluminium

Hello,

my brother finished to build his cnc milling machine ; its cnc who is capable to mill alu molds

And so, i have a question : it is necessaire to put a vrillage on the wing mold? I know that some wing builders put 1...

Sorry for my bad English, school is far away!!

Fabrice
Fabrice67 is offline Find More Posts by Fabrice67
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 10, 2011, 12:46 PM
Now fortified with carbon
DLGjunkyard's Avatar
Canada, ON, Cambridge
Joined Apr 2010
2,610 Posts
I cant answer the question but for those that dont know vrillage means :twist or washout
DLGjunkyard is offline Find More Posts by DLGjunkyard
Reply With Quote
Old Dec 11, 2011, 09:20 AM
Jeff Carr
Ft. Mill SC / Charlotte NC
Joined Mar 2001
2,633 Posts
Fabrice

Thats a choice of the builder. I know here in the states most of the DLG's and 3 meter sailplanes have some washout in them. Full scale aircraft do too. I know Geralds Zone foils incorporate 1 degree in the tips.

You will have to ask yourself if the proto type aircraft tip stalled easy or not? If yes I would put in 1 degree. This will help that problem.

Now if it was for me. YES I would

Jeff
Goinav8n is offline Find More Posts by Goinav8n
Reply With Quote
Old Dec 11, 2011, 01:39 PM
Registered User
ron gijzen's Avatar
Liempde, Netherlands
Joined Jul 2007
145 Posts
Adding wash-out or not is not the right question.
The question should be: how much efficiency am I prepared to sacrifice in trade for a ability to turn tight circles at a low speed without sudden stalls?
If you don't have a flying prototype yet, you could make an analysis in XFLR and look at how the lift force is distributed across the span (ellipsoid would give best efficiency), and how the operating Cl is distributed along the span (ideally, fairly constant with a slight drop near the tips). If the airfoil in the tip differs from the root, than you need to compare the local operating Cl to the max Cl the airfoil in that location can deliver.
And you would have to do this for the Re-range (speed and chord) in which you want your model to perform well.

If you don't have the knowledge to do this or have someone around to help you, you are best of making a design that is close to something that performs well.

I think, if you are going to invest the time and $ in aluminium molds, you better make sure you are building a design that will perform, else it may be a big disappointment in the end.

Don't mean to spoil your party, you can still have a geat building project in moulds, but going aluminum moulds is what you do to earn the last few % in performance and build quality when evrything else is optimized, it is not the thing I would start with.
ron gijzen is offline Find More Posts by ron gijzen
Last edited by ron gijzen; Dec 12, 2011 at 12:59 AM.
Reply With Quote
Old Dec 12, 2011, 01:02 AM
Registered User
ron gijzen's Avatar
Liempde, Netherlands
Joined Jul 2007
145 Posts
Maybe you should team up with people who have skills that complement those of you and your brother? There must be modelling enthousiasts in your area with knowledge of aerodynamics and composites but lacking the means and knwo-how of milling molds fro aluminum. It would be a learning experience for everyone, the cost can be shared and the end-results is likely to be good.
ron gijzen is offline Find More Posts by ron gijzen
Reply With Quote
Old Dec 12, 2011, 02:49 AM
I hate propellors
emufingers's Avatar
Australia, SA, Normanville
Joined May 2009
363 Posts
Quote:
Originally Posted by Fabrice67 View Post
Hello,

my brother finished to build his cnc milling machine ; its cnc who is capable to mill alu molds

And so, i have a question : it is necessaire to put a vrillage on the wing mold? I know that some wing builders put 1...

Sorry for my bad English, school is far away!!

Fabrice
The yanks are always pretty blunt but let an Aussie have a go.

The aluminium can be milled as a positive plug and moulds taken from it or it can be direct milled as a negative and used directly as the mould.

The idea is to make sure all of the aerodynamic adjustments are built into the plug or the mould. If the wing require vrillage ie twist or wash in or wash out then the cnc code should produce this. because the wing should not need be adjusted out of the mould.


A good place to start your thinking is to download Profili PRO. It allows you to design wings, including adding washout etc and to produce an STL output that can show you the wing in 3D. If you purchase the product you get the ability to convert the STL file to CNC code suitable for your mill.

This will let you visualise the process. There are also many thread in the CNC area of this forum that will be helpful. I also know that there are a number of useful sites in German that may make things easier. Unfortunately I don't have the links as my knowledge of German is far worse than your knowledge of English. Google with your domain search limited to .de will probably find them.


Jerry
emufingers is offline Find More Posts by emufingers
Reply With Quote
Old Dec 12, 2011, 06:32 AM
Registered User
Strasbourg
Joined May 2009
95 Posts
Hello Ron,
Hi Jerry,

We know milling alu mold is an adventure. We dont have the knowledge for all and i will thank you for your interest.

My brother work for a aluminium factory, so he can have some alu in good price.
I work actually with Predim RC (a few like xflr) with other guys in France...So i can mutualize the knowledge to built our project.

Here is a vid of the cnc :

http://cjoint.com/data3/3LmnFMGWlBj_IMG_1524.MOV
Fabrice67 is offline Find More Posts by Fabrice67
Reply With Quote
Old Dec 12, 2011, 07:25 AM
I hate propellors
emufingers's Avatar
Australia, SA, Normanville
Joined May 2009
363 Posts
Quote:
Originally Posted by Fabrice67 View Post
Hello Ron,
Hi Jerry,

We know milling alu mold is an adventure. We dont have the knowledge for all and i will thank you for your interest.

My brother work for a aluminium factory, so he can have some alu in good price.
I work actually with Predim RC (a few like xflr) with other guys in France...So i can mutualize the knowledge to built our project.
That is impressive. Have a look at the CNC thread in this forum there is a lot of infromation there. I will have a look at Predim

Jerry
emufingers is offline Find More Posts by emufingers
Reply With Quote
Old Dec 13, 2011, 03:26 AM
Registered User
ron gijzen's Avatar
Liempde, Netherlands
Joined Jul 2007
145 Posts
Quote:
Originally Posted by emufingers View Post
The yanks are always pretty blunt but let an Aussie have a go.
The dutch are a good 2nd though
ron gijzen is offline Find More Posts by ron gijzen
Reply With Quote
Old Dec 13, 2011, 05:01 AM
I hate propellors
emufingers's Avatar
Australia, SA, Normanville
Joined May 2009
363 Posts
Quote:
Originally Posted by ron gijzen View Post
The dutch are a good 2nd though
Aussies are not known for observing all the niceties either m I have several dutch friends wh0o like aussies are interested ingetting things done
emufingers is offline Find More Posts by emufingers
Reply With Quote
Old Dec 13, 2011, 02:31 PM
Registered User
Germantown, Maryland
Joined Apr 2004
4,493 Posts
I almost made another of those really blunt posts. I'm glad that I didn't do it though, now that I see that bluntness is considered a compliment.
Phil Barnes is offline Find More Posts by Phil Barnes
Reply With Quote
Old Dec 13, 2011, 04:09 PM
Registered User
Strasbourg
Joined May 2009
95 Posts
Hello,

i have work a lot to see if i need a twist on the wing before milling yhe molds.
We din't put a twist, the Predim RC is ok. So my brother must enter all in Gcode and for the new year, we will built the molds.

Here is a picture :

http://cjoint.com/11dc/ALnxjb5X0s4_P...laneur_2m.xlsm

Next pictures when the cnc is milling alu.

Bye
Fabrice67 is offline Find More Posts by Fabrice67
Reply With Quote
Old Dec 22, 2011, 04:26 PM
Registered User
Strasbourg
Joined May 2009
95 Posts
Milling a Volcano mold stabilizer of aluminium...

http://www.colmar-cnc.com/fr/attachm..._attachment=18
Fabrice67 is offline Find More Posts by Fabrice67
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Making a mold for two piece wing. Dbox Composites Fabrication 7 Sep 07, 2011 01:19 AM
Build Log How to make a wing mold RCShop Composites Fabrication 0 Mar 25, 2011 05:14 PM
Discussion CNC milling - plug or mold? jvander Composites Fabrication 9 Jul 27, 2006 12:29 PM
Discussion How can I make a wing mold from my existing wing? soholingo Composites Fabrication 31 May 19, 2006 04:44 AM
Converting straight wing mold Mig 27 to swept wing? AMTJIM Electric Ducted Fan Jet Talk 0 Nov 07, 2002 03:25 PM