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Old Jan 22, 2002, 11:55 PM
Flying slowly along..
Northern Ca.
Joined Dec 2000
1,336 Posts
How do you cut long straigt lines in foam?

This is one for you hot wire guys... How the heck do you cut the long straight lines when cutting out the panels for your wings? What I'm getting at is when you're cutting your blocks of foam to shape before you actually cut the airfoil, how do you make the long straight line cuts?

I've tried it with a bow, but the wire keeps wanting to wander and I don't get nice clean cuts.


Thanks for your help--Rob
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Old Jan 23, 2002, 12:14 AM
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Craig Logan's Avatar
Manchester, TN USA
Joined Nov 2001
217 Posts
I use a shelf board with L-shaped metal corner reinforcing brackets (standard hardware store item) screwed in each end. The foam sits weighted-down flat on the board, and the brackets act as templates to guide the hot wire. Sometimes, if my table saw isn't buried in the corner of the shop by too much junk, I'll just blast the foam through it.
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Old Jan 23, 2002, 12:24 AM
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Ellensburg, Wa, USA
Joined Dec 2000
554 Posts
Table Saw is great for squaring up the stuff.

Gary
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Old Jan 23, 2002, 06:47 AM
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drewjet's Avatar
Central Florida
Joined Oct 2001
419 Posts
I use a japanese pull saw makes a nice cut
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Old Jan 23, 2002, 10:04 AM
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kingston Ont, Canada.
Joined Nov 2000
33 Posts
I screw 2 pieces of wood vertical to the front of my workbench with countersunk screwholes almost as wide as my bow. Slide the foam in between and let 'er rip.
Gord
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Old Jan 23, 2002, 01:48 PM
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Brian Nixon's Avatar
Clifton, Va., USA
Joined Sep 2000
632 Posts
Squaring Cuts

I use two carpenter's sliding squares clamped to my workbench to guide the hot wire bow when making the squaring cuts for a set of wing cores.
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Old Jan 23, 2002, 05:46 PM
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Craig Logan's Avatar
Manchester, TN USA
Joined Nov 2001
217 Posts
FWIW, Brian's solution with the carpenter's squares is how my setup I posted previously works... just think of my reinforcing brackets as tiny little carpenter's squares... ;-)
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Old Jan 23, 2002, 05:56 PM
Pacific Models
Vancouver, BC
Joined Dec 2000
122 Posts
Foam cutting

Hang a piece of foam over the edge of a table with marks on either side of the foam. Then center you bow upside down by wire portion hanging on the foam. Centre the bow and turn the power on. I use a fan control with the dimmer switch running 2 Amp Radio Shack 24Volt transformer. Gravity does its job and it is clean cut every time. By controling amount of cerrent going to the wire you will control speed of the cut. 2" cut aprox. 30 secunds.

PS. Cutting wire -- 0.020 Stainless Steel safety wire or locking wire used on a full size aircraft.
John
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Old Jan 24, 2002, 04:41 PM
sk8
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Portland
Joined Dec 2001
23 Posts
Straight line

I make 90deg formica T. Hold this to foam with pins.
Have been using SS fishing leader 18mil for wire.

Dave
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Old Jan 24, 2002, 09:48 PM
Flying slowly along..
Northern Ca.
Joined Dec 2000
1,336 Posts
Boy you guys are great!! I actually used two pieces of l shaped aluminum for a guide and just run the bow along it, this works great now that i have the proper wire. I have also purchased a small band saw, that works great also.

I should have mentioned that I'm using epp foam and am trying to gear up for production runs of a small wing.

Any good info on making up templates quick??

Thanks again all of you---Rob
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Old Jan 24, 2002, 09:53 PM
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J Morgan's Avatar
Chapel Hill, TN USA
Joined Apr 2001
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Check out the thread in modeling science forum on templates.
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