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Author Topic: Carving concave shapes  (Read 2764 times)

Matthew Brown

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Carving concave shapes
« on: February 24, 2018, 04:49:53 PM »
I’ve run into difficulty carving concave parts like hollowing out wingtips several times. I don’t have any suitable tools for this work nor any idea what to get! I’ve always made do with Dremel sanding drums but I know there’s got to be a better way.
What’s the scoop for this?

Matt

Offline Dan Berry

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Re: Carving concave shapes
« Reply #1 on: February 24, 2018, 06:58:32 PM »
X-Acto has a set of blades that they call routers. They are similar to a scorp.

Matthew Brown

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Re: Carving concave shapes
« Reply #2 on: February 24, 2018, 07:06:36 PM »
X-Acto has a set of blades that they call routers. They are similar to a scorp.

What is a scorp?

Offline Air Ministry .

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Re: Carving concave shapes
« Reply #3 on: February 24, 2018, 07:08:53 PM »


Need a steady hand , or rest the wrist adjacent . alternately , mount the drill and hold the block .

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Offline Dan McEntee

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Re: Carving concave shapes
« Reply #4 on: February 24, 2018, 07:23:56 PM »
  The hobby knife makers such as Xacto, Excell, etc. make heat are called gouges that are used for carving. The blades fit the big red or aluminum handles that come with knife sets and you can buy them separately. If there is no hobby shop near you, try an art supply or crafts store such as Micheal's or Hobby Lobby for them. I almost never use power tools for hollowing out wingtips or carving cowls, too easy to let it get away from you and ruin a good piece a wood. I also use different grits of sand paper bonded to different shapes of wood like leading edge stock, dowels and such to finish sand things. Ted Fancher did a great article on carving cowls for either Model Aviation or Stuntnews and covers it all very well. His techniques will work for cowls, tips top blocks, anything! It should be pinned to the top of the building section here.
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Offline Tim Wescott

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Re: Carving concave shapes
« Reply #5 on: February 24, 2018, 07:25:00 PM »
The keyword is "gouge".  I made mine from music wire, but I'm crazy, and enjoy making woodworking tools as much as I enjoy woodworking.  If you don't get something disposable, you'll need to sharpen it all the time (maybe less so if you actually buy a quality tool instead of making your own from music wire!).  Balsa wood has this really nasty combination (from a woodworker's perspective) of strong fibers in a weak matrix, making it easy to rip the wood up instead of making clean cuts, combined with lots of little silica particles that dull blades.  So you at the same time that you need a really freaking sharp blade, the wood is constantly dulling your blade.

Particularly when you're gouging, a really sharp blade is your friend.

(I remember the xActo tools being called "gouges", but that was a long long time ago.)
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Offline Phil Krankowski

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Re: Carving concave shapes
« Reply #6 on: February 24, 2018, 07:41:42 PM »
Scorp, gouge, chisel, knife are among whittling and carving tools.  A scorp looks sorta like the xacto router, but usually is not a closed loop, and generally a little bigger.  These tools are easy to find, but a bit pricey.  I would recommend ordering drill rod if you wish to make tools.

Phil

Offline frank williams

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Re: Carving concave shapes
« Reply #7 on: February 24, 2018, 08:35:46 PM »
..... the best Xacto blade of hollowing tips is the router  shaped like a circle , use the big circle one ...
http://www.xacto.com/products/cutting-solutions/blades/detail/X135

Offline Brett Buck

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Re: Carving concave shapes
« Reply #8 on: February 24, 2018, 08:50:32 PM »
I would suggest carving with one of the suggested tools, but I use sharpened brass or SS tubes, and take "core samples" at shallow angle to remove the bulk materal, Shove one in from one direction at about a 5 degree angle to the surface, pull it out, come from the other side, and merg it with the other cut, or break off the "plug". This removes the wood very quickly with minimal mess.

   The other alternative, maximally messy, is the Dremel sanding drum. This is very safe and easy to control (particularly compared the burrs Matt showed above), and also does the work very quickly. It generates massive snow drifts of balsa dust, but that's what they make vacuum cleaners for.

    When you get close, coarse sandpaper, loose, curled up and slide longways, smooths out any divots, and I end up with a small round bit of sandpaper (1/2" or so), maybe 180 or 220, glued to my finger with Hot Stuff.

     Brett

Matthew Brown

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Re: Carving concave shapes
« Reply #9 on: February 24, 2018, 08:58:24 PM »
I have a vague memory of an X-acto blade that was about a 1/2” diameter loop. I’m guessing this is what is being suggested. I also had a carbide sanding ball made by Robart that cut great but was so out of balance it destroyed one of my Dremels.

As far as drill rod, I have access to any size I could ever need, plus a heat treat furnace and quench tank. I’d just need to see pictures of what to make out of it!

Thanks, Matt

Offline Dan Berry

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Re: Carving concave shapes
« Reply #10 on: February 24, 2018, 09:00:53 PM »
I have a vague memory of an X-acto blade that was about a 1/2” diameter loop. I’m guessing this is what is being suggested. I also had a carbide sanding ball made by Robart that cut great but was so out of balance it destroyed one of my Dremels.

As far as drill rod, I have access to any size I could ever need, plus a heat treat furnace and quench tank. I’d just need to see pictures of what to make out of it!

Thanks, Matt

Your memory of the round loop blade is correct. They call it a router.
Google search 'scorp tool' for images.

Offline Randy Cuberly

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Re: Carving concave shapes
« Reply #11 on: February 24, 2018, 10:22:20 PM »
For the final finishing process on the inside of blocks etc I use small round cylinders of various grits available at woodworking shops.  They are very stiff and can be cut to various lengths and used to sand by simply holding between your fingertips.  They are available in sizes from about 1/4 inch in diameter to more than an inch in diameter and 4 or five grits from very coarse to fine!

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Offline Don Jenkins

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Re: Carving concave shapes
« Reply #12 on: February 25, 2018, 06:10:00 AM »
I’ve run into difficulty carving concave parts like hollowing out wingtips several times. I don’t have any suitable tools for this work nor any idea what to get! I’ve always made do with Dremel sanding drums but I know there’s got to be a better way.
What’s the scoop for this?

Matt

For wing tip blocks, I tack glue the blocks together and once the outer shape is established I split the wing tip in half at the tack glue point then hollow each half separately (much easier) with the various tools and techniques discussed above, then glue them back together.

Don

Offline Mike Danford

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Re: Carving concave shapes
« Reply #13 on: February 25, 2018, 06:24:48 AM »
Handmade rasps are AMAZING.  Cut 1/16 balsa with control and ease, cut oak like is butter and you can hand sand with 100 grit to rid the tool marks.  PERFECT for a stunter nose. 

This riffler style one is slick with models.  Lasts forever, hand made and not cheap but worth every penny.

The burrs are also slick and work a lot better than the ones designed for porting heads in models and balsa. 

Tools

Nevermind, not in the mood to resize files.  Google auriou rasps and kutzall burrs.

Online Bob Hunt

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Re: Carving concave shapes
« Reply #14 on: February 25, 2018, 09:24:48 AM »
X-Acto or Excell gouge and chisel sets work well to take out most of the excess wood in a carved tip or fuselage top/bottom block. Brett is absolutely correct in his observation that a sharpened brass tube worked from various angles also does a pretty neat job of hollowing, As Randy Cuberly noted, a round drum sander sleeve is very handy for smoothing out the "bumps."

I used all those tools to make a set of Horner (not sure of that spelling...) tips for an RC wing a while back. See it in your mind, and then use the tools at hand to make it a reality! Here are a few photos of that tip.

Later - Bob Hunt

Offline Chris Cox

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Re: Carving concave shapes
« Reply #15 on: February 25, 2018, 03:23:56 PM »
I regularly use the X-Acto gouges, but I also have a couple of “bent” and “spoon” gouges from Lee Vally Tools.  They are incredibly sharp!

http://www.leevalley.com/us/Wood/page.aspx?p=58812&cat=1,130,43332,43703&ap=1

Offline Steve Helmick

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Re: Carving concave shapes
« Reply #16 on: February 25, 2018, 04:58:38 PM »
Most guys mold fuselage "blocks" from sheet balsa, over foam bucks. John Callantine published an article in SN showing how he molded wingtips, so no hollowing was required. A search here should turn up some info on molding balsa. y1 Steve
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Offline Brett Buck

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Re: Carving concave shapes
« Reply #17 on: February 25, 2018, 05:09:29 PM »
Most guys mold fuselage "blocks" from sheet balsa, over foam bucks. John Callantine published an article in SN showing how he molded wingtips, so no hollowing was required. A search here should turn up some info on molding balsa. y1 Steve

  Any of Al Rabe's articles would explain that, too, he more-or-less popularized it.

    Brett

Offline Steve Helmick

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Re: Carving concave shapes
« Reply #18 on: February 25, 2018, 05:18:40 PM »
Did Al mold wingtips? I don't recall that.  n~ Steve
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Matthew Brown

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Re: Carving concave shapes
« Reply #19 on: February 25, 2018, 05:50:33 PM »
My wife was making an order on Amazon Prime so I had her add on the X-acto carving set. It will be a start anyway!

Matt

Offline Al Rabe

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Re: Carving concave shapes
« Reply #20 on: February 25, 2018, 07:06:30 PM »
I hollowed block for wing tips and cowlings with a Dremel Moto tool and burrs.  I also split the tips to hollow.

Al

Offline TDM

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Re: Carving concave shapes
« Reply #21 on: February 26, 2018, 06:13:54 AM »
May I sugest an alternative solution to carving?
You can mold with two layers of balsa 1/16 over a mandrell with white glue and ace bandaids. To get around the LE compound curvres you want to slit the balsa, in the grain direction, evry 1/4in or so just the last 2in in the front.

The idea is that you have to shape the outside of the balsa block anywaise. so insted of doing thet to finish size you undersize 1/8in. Then use that for a buck.

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