Cutting Fiberglass for a shelf

[doke01]

I want to put in a shelf under the aft dinette seat in our R25 that is accessible from the galley. To do this, I need to cut a rectangular hole in the fiberglass. Can anyone make suggestions on the best tool to do the job? I was thinking a rotary saw would probably be best but I want to make sure the edges are as straight and clean as possible.

Also, what have you used for the shelving material? Marine plywood or something else?

Thanks,

Doug K.

 

[j&lgray]

Hi Doug,
I have put shelving under both dinette seats and used 3/8" Starboard, a marine plastic product that is commonly used throughout the boat, because I was concerned about mold and mildew that could/would attach itself to a plywood product. However, this thickness of Starboard requires more support due to the spans. I put in 1/2" thick cleats of Starboard around the edges to pick up the weight.

To create the penetration through the fiberglass, I used a drill to make holes in all four corners and used a jigsaw with a fine-tooth blade to cut the line between the holes, filed and sand the edges and called it good. I used 3/8" starboard to make the door that over laps the entrance and has the hinges on the bottom edge and then used a magnetic latch to hold it closed; this has worked quite nicely.

For the aft dinette, I opted to not to cut through the fiberglass but rather access that area through the entrance of the "cave." The first shelf sagged badly over time because the aft edge was not not supported. So, I replaced it and fastened a 4" high lip to the shelf by notching the wood and screwing the shelf to the wood lip. Now, it will support all the weight I need it to.

 

[doke01]

John,

I did see you pictures and they look great! Thanks for the feedback. I'll follow your technique and let you know how it goes.

Doug

 

[Finnegan's Wake]

Reading Dave Baker's postings, he took a similar approach to cutting into fiberglass - using a drill hole as a pilot and a jigsaw to cut through the fiberglass. I agree, it's the best way to prevent splintering or catastrophic damage.

 

[Andrew Custis]

These guys have it right on. Drill the pilot holes big enough for your blade to spin 360 degrees. They make actual blades that make a perfect cut on fiberglass. Rather then teeth on them they use a carbide grit blade which will last for a long time and will not chip the glass while cutting. Here is a link to the one I am talking about.

http://www.lenoxsaw.com/enUS/Product/CA ... LADES.html

 

[doke01]

Thanks Andrew! I'll pick one up and take some pictures when the work is all done. I'm planning on using StarBoard for the shelving material.

 

[Andrew Custis]

Starboard is fantastic stuff, but very heavy. I would be careful of how much you add because of the weight and supporting of it. Not to mention the cost. Just a thought. 😀