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Old Apr 17, 2010, 05:36 PM
Scale Modeler
Concordefan's Avatar
Canada, ON, Mississauga
Joined Feb 2006
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Question
How to cut foam delta wing with complex curves?

I have cut straight and tapered wings before with hot wire cutter, no problem.

My problem now is very complex and i need to know how i can do it with foam before i go to built up wing. This is a delta wing with drooped leading edge and has anhedrial that is in curvature form cross section wise. Root to tip on OB wing sections.

So basically i will have to cut longitudinally curves and also anhedrial curves at the same time with regular hotwire cutter..... I'm more concerned about cutting OB wings then IB wings...I have posted pictures from front, side and back of the airplane to show what i mean.

Like i said straight wings, taper wings and swept back wings are not a problem but this is very complex wing for me so i'm here seeking help from guys who might have done this sort of wing before..
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Old Apr 17, 2010, 08:57 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,350 Posts
Do it in pieces that leave enough material to allow hot wire cuts after joining or just use abrasives to blend the various sections.

Another option, if you're doing the wing in the scale thickness, would be to form a bed that is shaped to the bottom of the wing then heat form thinner layers over the bed and build up the thickness. The layers would be bonded together with a heat friendly adhesive. Then using a series of templates that key to the bed to allow the wire to cut away at different portions of the top to shape the top into a segmented form. Finally you'd use some abrasives to feather in all the ridges to give a pretty good scale to near scale upper surface.

And of course mixed in with all this would be spars, various channels for equipment, motor mount hardpoints, ribs for hard points to allow hanging hinges, etc, etc.
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Old Apr 18, 2010, 10:57 AM
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gutboy17's Avatar
Redding, CA, USA
Joined Nov 2000
195 Posts
I don't think my method would work for scale wings such as on the Concorde or B-58, but on some of my deltas I've used what is called the root-trailing edge method. Basically your templates are a root profile and a trailing edge profile. Starting at the aft inbd root corner of the wing you run the hot wire forward towards the leading edge keeping it parallel with the leading edge. Do the top surface cut and then the bottom. Keep the draw speed up when your cut length is short (usually the start of the cut) and then slow your cut speed down when the cut length starts to increase (towards the leading edge). This will give you a smooth cut and prevent the wire from dragging in the middle of the cut.
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Old Apr 18, 2010, 12:23 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,149 Posts
I had a lot of trouble cutting my Vulcan wings from foam.

The inner section was easy enough. The next section took two cuts*. Finally the tip was rough cut and the whole lot sanded to blend together.

*The straight delta was cut first. I wrapped masking tape around the mid section. Then with a small template on the end, I cut using the end template and the masking tape as the the other template. Gived the stepped section.


gb17, one method of doing straight taper deltas is to fix one end of the hot wire and just have one template on the inner end. See the picture below.
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Old Apr 18, 2010, 01:11 PM
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Concordefan's Avatar
Canada, ON, Mississauga
Joined Feb 2006
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HI Guys,

I see what you guys are suggesting and these are good points no doubt, but from what i see these tricks are good for straight delta wing airplane whom don't have curving anhedral on the outer wings. LE droop can also be added later on but my main point is to ask for a method to cut anhedrail curved wing panels using my hotwire cutter!. None so have have pointed into this complex curve and how it could be cut.

Cutting Inboard wing is not a problem at all, whole problem is the outboard wing panels on Concorde.

As Bill said, cut into many pieces or use layering cutting and joining method, this is partially what i can see is try able method but then i have never used heat to form foam curvatures or used heat friendly glues/adhesives before so i'm bit hesitant at this time to do so something new.

Worst come to shove if foam core method is too time consuming and will need a lot of experimenting then i will go back to built-up methods as it's much more easier to do this that way as far as i can see.


Pls keep sharing more ideas here as this is not the end of this not the end off road.


Sam
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Old Apr 19, 2010, 07:43 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,149 Posts
I don't think it's feasible to cut what you want, (a double curvature ?), with a hot wire, especially the tensioned wire type. A straight line cannot follow a double curvature.

Your only chance with a hot cut would be some sort of pre-shaped wire, (piano wire ?), even then I don't know if you could follow a template.
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Old Apr 19, 2010, 07:11 PM
Registered User
Joined Aug 2005
2,687 Posts
Quote:
Originally Posted by Concordefan View Post
HI Guys,

I see what you guys are suggesting and these are good points no doubt, but from what i see these tricks are good for straight delta wing airplane whom don't have curving anhedral on the outer wings. LE droop can also be added later on but my main point is to ask for a method to cut anhedrail curved wing panels using my hotwire cutter!. None so have have pointed into this complex curve and how it could be cut.

Cutting Inboard wing is not a problem at all, whole problem is the outboard wing panels on Concorde.

As Bill said, cut into many pieces or use layering cutting and joining method, this is partially what i can see is try able method but then i have never used heat to form foam curvatures or used heat friendly glues/adhesives before so i'm bit hesitant at this time to do so something new.

Worst come to shove if foam core method is too time consuming and will need a lot of experimenting then i will go back to built-up methods as it's much more easier to do this that way as far as i can see.


Pls keep sharing more ideas here as this is not the end of this not the end off road.


Sam
A CNC mill could cut the shape easily, but a traditional hotwire cutter can only cut straight sections. If you can cut your wing in many different small sections, then you can join them to approximate the desired shape. That's about the best that can be done with a hotwire cutter.
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Old Apr 19, 2010, 10:39 PM
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Concordefan's Avatar
Canada, ON, Mississauga
Joined Feb 2006
2,009 Posts
Thanks guys for your support but i have decided to back to my original plan to make built-up wing and now i have completely dropped the idea of foam core wing for this model.

Regards,
Sam
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