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Router for cutting plywood panels

Posted: Thu Jul 13, 2017 11:51 pm
by Catbldr
I'm new at this but awhile back I was talking to a person who had built several boats. I was, and still am, intimidated by the proposition of accurately cutting out the plywood panels. He told me just clamps it in place and uses a router with a trim bit to cut it out. If this is possible can some explain how this is done? It seems to me that clamping it up or temporarily fastening it in place and marking is a more accurate way of doing the process.

Re: Router for cutting plywood panels

Posted: Fri Jul 14, 2017 2:18 am
by Hercdrvr
Looking in from the outside, building a 1st boat is perplexing. Almost any wood cutting tool would work fine to trim the planking. Any tool ending in the word "saw" would do the job, it's whatever works for you. The perfect saw on the transom might be the wrong tool for the bow.

A router is not my choice for planking because they scare me and they're hard to control free hand, but it would do the job just fine.

For me. Much of the shaping of the wood is a progression from rough cutting aggressive tools to a fine precision tool. For example, I cut a planking sheet into a manageable size with a jig then glue and screw it to the frame, next a sawz-all to get it close and finally a belt sander.
Yesterday I used a chain saw to rough in the transom of a Barrel Back. See "Texas 20ft Barrel" thread.

Buy some plans and dive in, the waters' fine.
Matt B

Re: Router for cutting plywood panels

Posted: Fri Jul 14, 2017 5:39 am
by JimmY
A trim bit has a guide bearing on it, which rolls along the frame or adjacent plywood. The problem with this is the the angle between the sides and bottom change constantly, so the router will only get you so far.

Typically I temporarily install the plywood and mark it. I recommend always cutting it oversized just in case something happens or you didn't think of something. I've primarily used a hand held sabersaw and a hand plane. Just make sure to set your screws back from the edge or you'll get really good at sharpening! :shock: I like the hand plane over a sander just for the lack of dust, but both are effective.

Like Matt says, you will find you need a variety of tools depending on the job.

Re: Router for cutting plywood panels

Posted: Fri Jul 14, 2017 6:20 am
by BayouBengal
For any impending boat building task that involves cutting, there always seems to be at least five tools that could be used to do the job. I'm going to echo what the Herc and Jimmy have stated, which is, what's the right tool for doing various cutting and trimming tasks is largely dependent of what you're comfortable working with. I don't know this for certain, but from reading posts on how other boat builders accomplish cutting and trimming tasks, and knowing how I do, I suspect I probably use a router in my work much more than others; and as a frequent router user, here's my thoughts.
1) I consider a router to maybe be the most dangerous tool in my shop because of the exposed blade with the potential to kick and jerk during use. And try to be really damn sure that you don't route anything with a hidden screw head. Of course once you do, and I have, chances are good that you won't repeat that mistake.
2) I have three routers of different sizes, each have their pros and cons, and I use all of them. But the one I use by far the most frequently is a very small hand held one with a small base that can get in to places most routers won't. It is pictured below. While it is quite small and designed to be held with one hand, I won't use it in any place that I don't have room to wrap both hands around it (for reason #1). If you're going to buy one, and only one, get this one
rigid router.jpg

3) I have a love hate relationship with routers. I love them when I quickly and professionally trim something that would have taken a much longer time to do with various other tools, but I hate them when they catch a grain in a piece of mahogany and shear off a chunk, or when the blade and/or guide moves up or down in the middle of a task. Using a router, I've done things in a couple of minutes that would have taken maybe an hour to accomplish with other tools. I've also F&(*#((*#D up things with them that I then had to take hours correcting.
4) Probably most directly answering your posted question, you can use a router with a guide bit like Jimmy described to cut out planking, and I have, but you either need a near 90 degree angle between the base and the piece that is being trimmed; otherwise, you have to free-hand it with the router, which I've also done. Herc's method of trimming close and using a belt sander (or plane, or rasp, or longboard) to get you the rest of the way there is also a good way to do it and I've probably done that more often than using a router for the planking task. In a nutshell, just start building, along the way, you'll figure out what tools work best for you.