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Nov 12, 2006, 11:33 AM
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Cutting hatch on lost foam fuse.

The hatch will be square.
I was going to use dremel with 1/16 bit, but on low speed it heats up the 4 layers of carbon, glass and epoxy on my trial cutoffs slightly.
I am worried about clogging the bit on the 16" long cuts with the pink foam and epoxy not to mention finding a way to keep the cuts straight!
The fuse. is 4" in dia. and almost round and I want to reuse the cut out as the final hatch.
Any ideas on jigs or tools to get this done with out trashing the cuts?
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Nov 12, 2006, 01:25 PM
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Ward Hagaman's Avatar
Others that know better might chime in, but in my experience a zona saw does a good job and it has a very narrow kerf--
Nov 13, 2006, 07:58 AM
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No one else has done this successfully?
Nov 13, 2006, 09:28 AM
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I've used a #13 blade X-Acto saw to do this. Take your time and you can get a nice fine line. --Derek
Nov 13, 2006, 01:01 PM
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mhodgson's Avatar
With this sort of thing I use a dremel with an abrasive disc in it. Make the cuts shallow and keep passing over until it cuts through. lots of thin cuts will not heat up as much as trying to cut through it all at once.

The secret is to take your time.
Nov 14, 2006, 10:00 AM
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Ok, I will try the #13 blade first, if that doesn't work I will try the cut off wheel using a steel guide to stay straight (hopefully) on the long cuts.
Nov 15, 2006, 03:18 AM
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DrFragnasty's Avatar

masking tape it first

Hi Jim,

Don't forget to run some masking tape over the area then mark it with
pen. The masking tape provides more stability for the cutter.

Nov 15, 2006, 11:14 AM
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Great tip Chris! Thanks
That epoxy is slick and hard.
Dec 01, 2006, 08:13 AM
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Thanks for the tips guys, I ended up using the zona saw for the cuts across the fuse and the dremel thin cut off wheel using a 1/8" thick x 1/2" strip of alum taped to fuse with packing tape as a guide to make the long (16" ) cuts, made 6 passes with knees knocking.
Works like a charm, nice clean thin cuts thur .060 carbon, glass epoxy.
Wonder if this will work on Carbon, Kelvar too???
Dec 01, 2006, 11:36 AM
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Sled Driver's Avatar

A couple suggestions:

1) Don't worry about having perfectly straight lines, or a really narrow curf. There is a good way to seat the hatch after you have removed it to solve curf and wobbles in your cut. However, you do want to have the wobble on the outside of what you want to be your hatch.

2) I've had success using different abrasive disks and little saw blades on the Dremel tool. And, I've also uses hacksaws, Japanese Saws, and the saw blades that I've removed from Zona Saws.

3) I typically use multiple types cutting methods when removing a lost foam hatch. For example, the last hatch I cut I used circular saw blade on a Dremel motor to make the cuts along the major axis of the fuselage, I used a hacksaw to make the cuts across the top of the fuse, and I used a Zona saw blade that was removed from the handle to finish the cuts in the corners.

4) If you are going for rounded corners, don't hesitate to use a wider Dremel tool bit, e.g., the 1/8" router bit even, on the rounded corners. Make the cut so the curf on the fuse side of your line not the hatch side of your cutting line.

5) Once the hatch is free, sand the perimeter of the hatch smooth and just the way you want it.

6) The way you hold the hatch in place and fill the gap between the hatch and fuse is as follows:

a) Carefully wrap the hatch with packing tape, partcularly the around the edges and inside surface.

b) Tape the hatch in place where you want it be.

c) Fiberglass inside the fuse under the hatch. The FG should exend about an inch around the opening and you use 6 to 8 oz of FG.

d) Fill the gap between the hatch and fuse. Depending on how wide the gap is you might want to use some milled glass or cotton flox with some microballons.

e) When cured, sand over the joint between the hatch and fuse, remove the hatch, and trim the FG you installed so that you have a flange that around the hatch opening 1/8 to 1/4-inch wide that the hatch sits on.
Last edited by Sled Driver; Dec 01, 2006 at 08:37 PM.
Dec 02, 2006, 10:26 AM
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Thanks Sled Driver,
I did the flange a little differently, I laid glass and epoxy over the completed fuse in the hatch area before I made the hatch cut, placed it in the fuse and marked the outline of my cut out and Dremeled it out leaving a lip for the flange then epoxied the flange in the fuse, worked great!
Because I layed the flange up on the outside of the fuse the tension when placed on the inside made for a very tight glue joint.

Different ways to skin the same cat I guess

Any one know if you can cut carbon Kelvar epoxy with a dremel friction wheel??
Last edited by JIM CALDWELL A; Dec 02, 2006 at 10:32 AM.

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