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Foam removal

Old 03-29-2013, 02:13 AM
  #1  
p3arljam
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Default Foam removal

I want to remove a square section of foam from the bottom of my plane but i dont want to cut all they way through to the inside of the fuse. I have the patterned traced out and just need to remove a few layers of foam so the piece i am installing will be flush with the fuse. The piece is the size and thickness of a credit card. Is there a neat and clean way to do this?
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Old 03-29-2013, 02:35 AM
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kyleservicetech
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Originally Posted by p3arljam View Post
I want to remove a square section of foam from the bottom of my plane but i dont want to cut all they way through to the inside of the fuse. I have the patterned traced out and just need to remove a few layers of foam so the piece i am installing will be flush with the fuse. The piece is the size and thickness of a credit card. Is there a neat and clean way to do this?
One way is the use of a soldering gun. Remove the tip of the gun, and install a piece of #12 solid building copper wire, the type used in the outlets in your house. (I don't know if #14 wire would get hot enough.)

Shape the copper wire to a little smaller than the width of your required cutout, heat up the gun and slice away. You want to cut about 1/4 inch per second or so. Control the heat of the soldering gun by pulsing the trigger on and off.

This will require some sort of depth control, perhaps with a wheel collar on the copper wire. It will require a bit of practice on some pieces of scrap foam. If it looks good, then you could try it on your fuse. This is not original, many modelers have been using this type of thing for decades.

And, if to much is removed, find some of that "Premium Grade Patch - N - Paint lightweight spackling compound. I found a small container of it At Ace Hardware.

This spackling material has little mechanical strength, so don't use it in structural areas.
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Old 03-29-2013, 03:43 AM
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fhhuber
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The very thin amount being considered.. the solder gun is a bit overkill.
Great for cutting in a wheel well for retracts.

This 1/32 to 1/16 thickness... OW... no really easy way

VERY sharp knife. Cut around the perimeter.
Angle the knife (longer blade is better) and from inside what needs to be removed cut aiming the tip at the perimeter and depth... go all around leavng a hump in the middle... then cut out the hump.. then sand with 120 or higher (finer) sandpaper.

The solder iron would just melt it down . Its too thin for the iron to remove material.

*************

A "cheater" method:

Cut the square out all the way through. Pull it out. you can now access it from the side to slice off the thin layer. Glue it back in as you glue on your ply plate.
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Old 03-29-2013, 03:58 AM
  #4  
pmullen503
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One way to do it is to take a piece of wood, in your case, about and inch wide, 4 or 5 inches long, 1/2" thick. To that glue a spacer (cardboard or a strip of plastic) and a piece of 80 grit sand paper about an inch long in the center of the stick. The thickness of the spacer and the sandpaper are the depth of the recess. Put some packing tape around the perimeter of the recess and slide the stick back and forth to sand the recess. Blow out the swarf every few strokes. Eventually the stick will ride on the tape around the perimeter. Don't press too hard or you'll dent the perimeter. It's tedious but it works pretty well. Do cut around the edge of the recess with an exacto knife to get a clean edge.

Last edited by pmullen503; 03-29-2013 at 01:24 PM.
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Old 03-29-2013, 04:46 AM
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kyleservicetech
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Originally Posted by fhhuber View Post
The very thin amount being considered.. the solder gun is a bit overkill.
Great for cutting in a wheel well for retracts.

This 1/32 to 1/16 thickness... OW... no really easy way

VERY sharp knife. Cut around the perimeter.
Angle the knife (longer blade is better) and from inside what needs to be removed cut aiming the tip at the perimeter and depth... go all around leavng a hump in the middle... then cut out the hump.. then sand with 120 or higher (finer) sandpaper.

The solder iron would just melt it down . Its too thin for the iron to remove material.

*************

A "cheater" method:

Cut the square out all the way through. Pull it out. you can now access it from the side to slice off the thin layer. Glue it back in as you glue on your ply plate.
Ooops

Missed the thickness of a credit card!

Cutting out something like that, and flat over the whole entire area will be difficult without a small milling machine. (Yup, got one)
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Old 03-29-2013, 05:00 AM
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Here's another tip...

go ahead and cut out deeper than you need to. It can be ugly even as long as the outline is right.

Apply clear packing tape to your ply plate in preparation to tape it in place on the belly of the plane.

mix 1 part white glue (Elmer's school glue or similar) with Quick set Gorilla polyurethane glue. (dries white) This will foam up pretty fast.

Smear the glue mix into the hole and slap that ply in place.
Smooth the tape down.

Check to ensure the foaming isn't pushing the ply up... if it is just push it down and add weight.

About 20 minutes later its all set up. Some glue may have seeped around the edges of the ply. Just sand it or carve it off.

It'll be pretty.
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Old 03-29-2013, 05:22 AM
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kyleservicetech
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Originally Posted by fhhuber View Post
Here's another tip...

go ahead and cut out deeper than you need to. It can be ugly even as long as the outline is right.

Apply clear packing tape to your ply plate in preparation to tape it in place on the belly of the plane.

mix 1 part white glue (Elmer's school glue or similar) with Quick set Gorilla polyurethane glue. (dries white) This will foam up pretty fast.

Smear the glue mix into the hole and slap that ply in place.
Smooth the tape down.

Check to ensure the foaming isn't pushing the ply up... if it is just push it down and add weight.

About 20 minutes later its all set up. Some glue may have seeped around the edges of the ply. Just sand it or carve it off.

It'll be pretty.
Or, use that premium grade patch and paint lightweight spackling under the ply sheet. This stuff can be tweaked before drying with the edge of a credit card. And is easily sanded after 24 hours of drying. Then, put a very thin layer of epoxy on the spackling, and place your ply sheet.

Just note that this spackling doesn't have much strength, so don't use it in a structural area. Appearance wise, after sanding the foam and spackling, this spackling is very close to foam.

As for me, I'd just put a wide bevel the edge of that sheet of thin ply, and glue it to the foam.
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Old 03-29-2013, 06:46 AM
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All depends on the desired result...

if he's interested enough to want to inset the ply then I am assuming he wants a good appearance on a scale model.

The beveled ply sticking out would annoy me on a scale model.

The spackle and epoxy is a bit heavy and as noted the spackle is a filler with no strength.

The foam glue mix is structural and is stronger than some foams (will break before the foam now being used by Dynam). You can mix this stuff up and fill missing pieces from a shattered foam wing.
if sheeting a foam core and repairing at the same time I use yellow glue and the sloer setting yellow version of the Gorilla poly glue
I said use the quick set and white glue so it should blend into the (typically) white styro/EPP/EPO and will be better for color matching.

I did forget to mention... I do expect the tape used to secure the ply as the glue dries to be removed.

The assorted methods of sanding the pocket for the ply will all work.
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Old 03-29-2013, 03:17 PM
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Razor plane?
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Old 03-29-2013, 03:19 PM
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Razor planes tend to rip foam.

Too bad the Hobbico power plane is discontinued... it could buzz it out.
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Old 03-30-2013, 12:39 AM
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Originally Posted by fhhuber View Post
The spackle and epoxy is a bit heavy and as noted the spackle is a filler with no strength.
The light weight spackle is so light, one would think the container is empty. I've taken that spackle and hit it with foam safe thin CA that turns the spackle into a very hard material.

Not recommended though, that just results in a major stress point between the very hard CA'd spackle, and what it's glued to.
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Old 03-30-2013, 12:44 AM
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I have a very big solder tip on my big weller solder station and I used that to "melt" some cutouts into my Fun Cub just went slow and at just enough heat to lay the tip down and "melt" the foam 1/4 inch deep.

Last edited by BBCorvette18; 03-30-2013 at 01:57 AM.
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