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Cabin top sanding/cutting tools

az_gila

Well Known Member
Just finished the initial trim on my cabin top.

I had read of builders using a belt sander for trimming the fiberglass but thought my old 3x24 belt sander was too unwieldy to handle.

I found this on Amazon and it works well. The one handed operation makes it easy to use on the not easy to clamp down cabin top.

https://www.amazon.com/Triton-TCMBS...pID=51ax2GqmALL&preST=_SY300_QL70_&dpSrc=srch

It does take a not very common 2.5x16 belt size, so buy an extra.

The belt it came with seems to still be working well though.

Yet another tool for your collection. :D

I also bought some PermGrit tools as suggest here on VAF and they work well. After I dropped the Dremel and bent the PermaGrit cutting disk, I found a good substitute stocked at my local ACE hardware store.

41QTK7YVYEL._SX425_.jpg


It's a Dremel 543 and with the carbide bits on one face I found it a little easier to steer around the curves while trimming the rear window cutout.
 
Gill,

I got mine fitted a month ago. I did all of the initial trimming with a 3" cut off tool and I used a belt sander with a 60 grit belt for finishing and fitting/sizing and it worked well. A key challenge is keeping the long surfaces in a straight plane. I couldn't imagine a smaller tool would be more effective. Admittedly, the belt sander is a bit unwieldy and requires some muscle to to keep it level in two axis. However, it was ultimately effective for me and material removal was rapid. Occassional checking with a straight edge was enough to train my eyes for keeping the line straight.

I did it on a windy day, which ensured every sq in of my body had fiberglass material on it. That was a fun evening.

I used a carbide bit on the die grinder to work the internal radii on the window areas.

Larry
 
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I just used a wooden block and 1-1/2" alum tube wrapped with various grits of sandpaper. More labor intensive for sure, but I just didn't want to buy a tool for the job.

As for cutoffs, I used a diegrinder for some big cuts, but relied mainly on a Dremel with an EZ-lock mandrel and various cutoff wheels, similar to this:
43126228472_fa72d578b5_m.jpg
 
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Gill,

I got mine fitted a month ago. I did all of the initial trimming with a 3" cut off tool and I used a belt sander with a 60 grit belt for finishing and fitting/sizing and it worked well. A key challenge is keeping the long surfaces in a straight plane. I couldn't imagine a smaller tool would be more effective. Admittedly, the belt sander is a bit unwieldy and requires some muscle to to keep it level in two axis. However, it was ultimately effective for me and material removal was rapid. Occassional checking with a straight edge was enough to train my eyes for keeping the line straight.

I did it on a windy day, which ensured every sq in of my body had fiberglass material on it. That was a fun evening.

I used a carbide bit on the die grinder to work the internal radii on the window areas.

Larry

I found the single handed use of the belt sander made it easier to get that even cutting you mention. I thought the 3" cutter on a die grinder was hard to control and my compressor couldn't keep up very well.

The much lighter weight Dremel with the carbide disk enabled one handed cutting, freeing up the other hand to hold the shop vac next to the cutting area.

It's too bl**dy hot outside at the moment so all my work was in the hangar. I was surprised at the small amount of dust created using the Dremel/vac combination mentioned and the Triton belt sander hooked up to the shop vac.

A 1/2 inch drum sander on the Dremel did the sharper corners, and a 2" Roloc sanding disk on an angle die grinder did the sharper corners.

The PermaGrit sanding block used by hand worked well to get a final flat surface were needed, while a heavy coarse belt from a belt sander used alone as a hand tool helped to smooth the curves in the window area.

As usual, many methods work :) but the lighter belt sander was one handed and easy to control and along with the Dremel was pretty good on dust control.

It's starting to look like a real airplane now. :)

ob2.jpg
 
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Here's my experience. I just fitted my cabin top 2 days ago.

Initial Rough Cutting:
I first tried a pneumatic cut off wheel, like this one:
https://www.harborfreight.com/3-in-High-Speed-Air-Cut-Off-Tool-60243.html, but the guard made it next to impossible to track the cut line, and, surprisingly, it didn't cut all that well.
Then, I tried a pneumatic air saw, like this one:https://www.harborfreight.com/High-Speed-Metal-Air-Saw-62541.html, but while it was fine for making cuts in aluminum sheet, it was terrible for cutting composites. So, I finally settled on using an oscillating multi-tool, like this one:https://www.harborfreight.com/variable-speed-oscillating-multi-tool-63113.html. It worked slowly, but it 1) didn't create hardly any dust, and 2) allowed me to easily see/track my cut lines. I think this is the best tool for initial cutting to the scribe lines.

Sanding:
Sanding the top down so that it fits snugly is an iterative process, involving lots of "put it on, take it off" work. It really helps to have extra hands. In searching for the best sander for this work, I stumbled upon this one: https://www.blackanddecker.com/en-us/products/power-tools/portable-power-tools/sanders/3inch-x-21inch-dragster-belt-sander/ds321 It worked flawlessly. Some people complained about having to constantly adjust the belt (left/right) on the drums. I didn't have this problem and found that I really like the fact that I could adjust the belt to slip all the way to one side, in order to get into really tight spots. The little dust bag actually collected quite a bit of dust, which was surprising to me, since most of those little bags seem to be "just for show." The other cool thing, was that the front edge radius is really small and you can lift the top off it, to use the top side of the belt, for getting into very tight areas without having to work with the sander upside down. It comes with one 40 grit belt on it, and I bought another pack of 5. In the end, I only used the one it came with and half of one from my pack to do the top enough for fitting. The top requires A LOT of sanding, so I pity anyone who tries to do it all using manual block sanders only.

Now, it's on to the detail work and then permanent mounting...
 
I used a mini angle grinder with a coarse disc for rough cuts and shaping. Blows through the fiberglass like butter and you don't need to listen to the compressor.
 
I found the best tool for cutting the fiberglass to be a Dremel tool with a diamond cutting disk. It was easy to control and created very little dust.

Then I used a 5" random orbit sander to do significant sanding and finished up with a long 2x4 with 60 grit sandpaper attached with carpet tape to sand both sides at the same time to keep them level (which I believe is the sanding method recommended in Van's plans.

There are multiple ways to accomplish this work, so suggest you experiment with scrap and pick the methods that work best for you.
 
I tried almost everything. Ultimately, I preferred the controllability of a jigsaw with a fine toothed blade for the big cuts. I liked my belt sander for aggressive sanding to the scribe lines, and I liked one of the sanding disks on an angle grinder for sanding off nibs and creases on the cabin interior and for minor work around the edges.
 
......and I liked one of the sanding disks on an angle grinder for sanding off nibs and creases on the cabin interior and for minor work around the edges.

Haven't got to that bit yet, but experimented a bit.

As you say, a 2" Roloc disk sander on a lightweight HF angle die grinder seemed to work well. The smaller die grinder worked well and my compressor could easily keep up with it.

I am quite amazed at how many nibs, creases and large lumps are present. :)
 
I am quite amazed at how many nibs, creases and large lumps are present. :)

These green tops are pretty ugly on the inside, aren't they. I knocked down all the major blemishes on the forward interior (you'll find that after you remove the blemish, you're into the soft foam interior and need to patch with Flox) and did about 3/4 of the fine filling and finishing of the rear interior. After three days I couldn't take the sanding any more and moved on to the wings, which I just finished today, along with the wing tips. Soooo, back to filling and sanding the interior. My finishing kit is ready for pickup at the terminal now, so on to doors next week.

Larry
 
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