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Building Tips and technical articles. => Building techniques => Topic started by: dave siegler on November 02, 2015, 02:49:44 PM

Title: best way to cut spar notches in foam wings?
Post by: dave siegler on November 02, 2015, 02:49:44 PM

Have had poor results using a hot wire and templates, the wire sagged. 

Sanded it worked well but that was messy and tedious. 

Will try a router table next pass. 

What is your experience?   
Title: Re: best way to cut spar notches in foam wings?
Post by: Curare on November 02, 2015, 08:11:13 PM
sounds like not enough tension on your bow.

I have no problems cutting spar slots in foam wings, although I rarely do it.
Title: Re: best way to cut spar notches in foam wings?
Post by: fred cesquim on November 03, 2015, 03:32:47 PM
on 33% scale r/c models i use this method: bend a wire to the shape of the chanell, make a side slider along the bend and plug to my soldering gun, then lay the slider on a metal rule and run along the wing, never had an issue, just nee to keep a steady movement to prevent the hot to build up and carve more than needed.
little practice and you will master ir perfectly
Title: Re: best way to cut spar notches in foam wings?
Post by: Fredvon4 on November 04, 2015, 05:43:10 AM
For my combat foam cores, usually no LE sweep, I just put a spacer for height of the Trailing edge to keep the wing panel center line level to the routing table, set my fence for distance back from LE, and rout to the correct depth....LOT of foam dust and it electrostatic sticks to every thing so I do it out side

On some tapered wings with some LE sweep back I prefer to tape both panels together and tape down a strait edge and use a cordless Dremel router atachment
Title: Re: best way to cut spar notches in foam wings?
Post by: Brent Williams on November 04, 2015, 08:22:57 PM
More wire tension. 

Cut the airfoil with a smooth template, no spar slot. 

Make a separate spar cutting template that has longer spar guides.   The spar template doesn't necessarily need to look like the airfoil, as its only purpose is to help make a clean cut.
Title: Re: best way to cut spar notches in foam wings?
Post by: Curare on November 05, 2015, 08:34:25 PM
Oh yeah, hadn't cosidered that you might be trying to cut the spar slots at the same time as cutting the wing shape, which will give you a big problem.

As brent says, cut the airfoil shape first, then cut your spar slots!