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Power Tools and Accessories for Cutting Fiberglass Hulls

In order to make our ships penetrable, we need to cut large windows in the fiberglass hulls. For those who have not done so before, cutting the hulls can be practically traumatic. Here are some tips on how to make the cutting much easier. These instructions assume that the hull has already been marked for cutting (our 3/8 inch tape works well for this) and has had the corners drilled.

For a long time, the tool of choice for cutting the windows in our fiberglass hulls has been the Dremel rotary tool with a fiberglass reinforced cut-off wheel. These wheels wear quickly, but they work. The standard ceramic cut-off wheels are not suitable for cutting hulls as any misalignment in the cutting will cause the wheel to shatter. Within the last couple of years, we found that the carbide cutting/shaping wheel (#543) works better than either of these wheels for cutting the windows in the hulls. I’ve only purchased a single one of these wheels and cut many hulls with it. The wheel base is metal, so the chances of the wheel breaking are very slim, and they do not wear out quickly.

Very recently, I found a tool that I think works much better than the Dremel rotary tool for cutting the hulls. This tool is one of the oscillating tools such as the Dremel Multi-Max combined with the grout removal blade or the Harbor Freight Multifunction Power Tool combined with a carbide half moon blade (HF #67462). With the HF tool and carbide blade, I cut out one half of the HMS Hood in one 35 minute session (and it was the first time I had used the tool). I timed myself at starting a 3 inch cut every 15 seconds. What I liked about using the tool is that you never felt like you were straining to keep the cutting action under control like one would with a rotary tool. You also only need to apply a little pressure to the tool against the fiberglass instead of forcing the blade along the cut. I did best by rolling the blade slowly between the drilled corners to cut through the gel coat, and then rolled the blade back to cut through the fiberglass below. One other thing I really like about this type of tool is that it doesn’t throw the fiberglass dust around like the rotary tools do. You still need to be wearing goggles and breathing protection, but the dust is much better. On the negative side, your hand will get tingly from holding the vibrating tool.

I’ve also tried the Harbor Freight inexpensive diamond wheel, but the this wheel takes three times as long as the carbide one. A more expensive diamond cutter might work better, but I haven’t picked one up.

After cutting the windows in the hull, you will almost certainly find that parts of the window panes and caprail will be too thick. Once again, Harbor Freight comes to the rescue. They have a finger width hand held belt sander that makes very short work of the sections that are too thick. The entire hull can be fixed in only minutes, depending upon now close the original cut was.



After about eight months of use, my Harbor Freight Multifuction Power Tool died. One of the motor brush springs broke. I’d found that I almost completely stopped using the Dremel rotary tool except for some metal cut-off and polishing during this time. With the death of the HF version, I’m keeping to my rules about buying cheap tools (buy a cheap tool once; if it breaks, you’re using it enough to warrant getting an expensive one). The Dremel Multi-Max is a much nicer tool for our purposes. The ability to change oscillation speeds is nice, but the really nice thing is that it is half the weight of the HF version. This makes it much easier for one handed usage, which is typically needed when cutting hulls.

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