HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 09, 2013, 07:12 PM
Registered User
Joel K. Scholz's Avatar
Kingsland, Texas USA
Joined Aug 2000
2,409 Posts
Help!
Cutting foam wing cores

I have cut a few cores in my building escapades with mixed success. I am designing some core templates now for a plank style winged bird.It seems that the most difficulty I have is the leading edge, particularly on a tapered wing. If the slopes aren't in sync it flattens the top LE. I seem to have more success cutting from the LE to the TE as the distance is shorter and less error accumulates. I mark the lines with scaled numbers to keep the wire at the same point in the respective ends. Do most people cut from front to back or vice versa. Is there tricks to help cut more accurate cores. I am using 1.9 EPP.
Joel K. Scholz is offline Find More Posts by Joel K. Scholz
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 09, 2013, 08:32 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
4,095 Posts
Keep the wire super tight. I use 1/4" music wire in a bow so as the wire heats up and stretches, the music wire legs will take up the slack. Keep the legs kind of short, maybe 8 inches or so. I cut from back to front and have a helper on the other end of the bow. If you cut too fast the wire will lag in the middle and give the effect you describe. Don't get in a hurry I think is the key. I'm using some 120 lb test stainless leader wire. It's a tad thick but you can pull it super tight. My power supply is a 4 AMP, 12 volt battery charger. Cutting a 30 inch core it lacks a bit but gets the job done. A thinner wire would help a bit but a 24 volt transformer would be better for the long wire.

Ken
kenh3497 is offline Find More Posts by kenh3497
Reply With Quote
Old Jan 10, 2013, 07:59 AM
Red Merle ALES
Curtis Suter's Avatar
United States, Mt, Helena
Joined Apr 2002
5,661 Posts
Joel,

Good to see you're getting some model building in.

You may be interested in these links, all FREE!
An article I wrote for RCSD called "Build an Automated Foam Wing Cutter". It talks about the bow as well as the automated part.
http://tailwindgliders.com/Files.html#Articles

Also FREE:
Tailwind Gliders is offering a FREE 12-minute instructional video on cutting highly tapered wing cores using a Pivot Cut method.

This is a 618Meg download. It is in a zipped .mp4 file format.
Download here:
http://www.twg.tailwindgliders.com/TWG/Pivotcut.zip

To answer your question I always cut from the leading edge to the trailing edge and I always cut the bottom airfoil first then the top. If you cut the top first then you're airfoil will be thinner by the thickness of the wire.

Curtis
Curtis Suter is offline Find More Posts by Curtis Suter
RCG Plus Member
Reply With Quote
Old Jan 10, 2013, 12:05 PM
Registered User
Joel K. Scholz's Avatar
Kingsland, Texas USA
Joined Aug 2000
2,409 Posts
Thanks for the tips
Joel K. Scholz is offline Find More Posts by Joel K. Scholz
Reply With Quote
Old Jan 11, 2013, 07:58 AM
Registered User
Omaha
Joined Oct 2005
18 Posts
Cutting foam

I cut everything front to back and agree with the advice to cut slowly to avoid wire lag in the middle of the cut. Also you didn't say what span you were trying to cut. It really is hard to get a good cut on more than 24 inches or so with a hand held bow. If you google "foam wing cutting" there is some really good advice out there.
Bob Furr
icerinkdad is offline Find More Posts by icerinkdad
Reply With Quote
Old Jan 11, 2013, 10:36 AM
Registered User
Joel K. Scholz's Avatar
Kingsland, Texas USA
Joined Aug 2000
2,409 Posts
I will be cutting with a 24" bow. I use about 120 lb steel leader. It is not unusual for me to break the wire. I am wondering how to determine the correct temperature. How do you test for correct temp. I always test on a scrap, but a full length cut requires more heat as the foam absorbs some of it.
Joel K. Scholz is offline Find More Posts by Joel K. Scholz
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Foam Core Cutting? ForeverFlying Hobby Stores 1 Dec 24, 2012 12:44 AM
Wanted Foam Core Cutting Wanted ForeverFlying Aircraft - Sailplanes (FS/W) 8 Nov 26, 2012 07:31 PM
Discussion Cutting extruded foam cores mikegbogh Composites Fabrication 8 May 23, 2012 11:08 AM
Help! CNC Foam Cutting for Foam Core Wings 1stfoot CAD/CAM 6 Jan 13, 2012 05:00 AM