# How to cut wood transom



## Duct Tape (Jan 5, 2016)

Hi folks. I'm new here and this is my first post.

I'm building a boat, a whitewater dory, and need some advice on how to cut the arched top of the transom. It is 3 layers of 1/2" marine plywood, laminated together with epoxy resin, plus some thin layers of E and S Glass fiberglass on each outside surface. So total thickness of a little over 1.5". It is already mounted to the boat, so a band saw is not a good option 

I need to cut an arched top from one edge of the boat side panel to the other. The person who has been giving me some building advice says he uses a circular saw, but it seem to me the radius of the cut (the transom is approx 24" across the top) will be too tight and the blade will bind and either kick back or destroy the wood.

Other options include a jig saw, with some long blades. Or maybe a recip saw. My plan with any saw was to cut just short of the final cut line, and then hand finish with a plane. I don't see where a router can safely do much here but open for good ideas.

Thx for any advice, and thx for a great resource.

Jon


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## Stick486 (Jan 4, 2013)

Bosch jigsaw w/ progressor blades...

T-Shank Jig Saw Blades for Wood | Bosch Power Tools

you'll get a fast clean cut...


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## Ghidrah (Oct 21, 2008)

I've made accurate circle cuts with my table saw quite a few times, with no binding, you just start out with a shallow cut and keep raising the blade after completing each circuit. A router and circle jig will produce a symmetric arch, however when dealing with plywood it can be a challenge regardless of the tool used. The more fibrous the ply the greater the chances are for shredding. You could pre draw the arch both sides of the transom then score the lines with a "sharp" utility knife or scalpel and or then add tape over the scored cut. You may even consider applying a pre coat of the resin along the line of the cut both sides of the transom to help set the fibers.


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## CharleyL (Feb 28, 2009)

Make a template out of 3/8 plywood. Then use a reciprocating saw to rough cut the transom about 1/4" from the template. Then use a top bearing long flush cutting router bit running against the template to finish the cut.

Charley


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## Cherryville Chuck (Sep 28, 2010)

Hi Jon and welcome to the forum. Don't try the circular saw. Your assumptions are correct. Even using a keyhole saw would be a better option than that. A jig saw with a long enough blade is your best option. That's the kind of cuts they were made for.


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## DesertRatTom (Jul 3, 2012)

I agree with CharleyL. Make a template, draw the line, cut outside the line with a jig saw, then use a trim bit with a bearing to make a smooth cut. An inch and a half, plus the template thickness is going to take a pretty good sized bit, so I'd go easy on how fast I'd move the bit during the cut. I also would cut a little closer than the quarter inch. But that's just me. Stick made a good point about using a Bosch blade. I find they cut better than any other brand.


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## Duct Tape (Jan 5, 2016)

Thanks for the advice. Much appreciated. If I were to go with the flush trim router option, how to attach the template? With two sided tape? Really no way to clamp since I need to leave the top arch free for the router pass and the sides and bottom of the transom are attached to the boat hull leaving little point for clamping. I suppose I could rig up some clamps on the side panels and then run a board across the template, and then strap to each side panel clamp.

I have to admit I'm a little nervous considering a router bit big enough for 1.5"+ of wood, handheld sideways in a router.


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## Stick486 (Jan 4, 2013)

clamp the template on with extra clamps..
remove the clamp that is in the way of the router and place it behind the router where you have already cut...

or...

place your clamps ...
trim between clamps...
stop the router...
move the clamps to the trimmed sections...
finish trimming where the clamps were...


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## Nickp (Dec 4, 2012)

Go with the jig saw..use your template with it...sand smooth after.

Did the same thing with wooden clam boat...

I agree with you for not using the router...


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## Duct Tape (Jan 5, 2016)

Here's an early pic of the transom. I left the top part proud since it would help protect the dory when it was turned over.

PS> If anyone wants to check out this build I have a blog about it (my first blog so nothing professional!):

www.westtavaputs.com


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## TwoSkies57 (Feb 23, 2009)

Excellent blog Jon!!!

once completed, this boat ought to be the source of an awful lot of fun while heading down the Colorado!!!


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## Cherryville Chuck (Sep 28, 2010)

Nickp said:


> Go with the jig saw..use your template with it...sand smooth after.
> 
> Did the same thing with wooden clam boat...
> 
> I agree with you for not using the router...


There are 2 types of template bits, one with the bearing at the bottom which is normally referred to as a flush trim bit and the other with the bearing at the top on the shaft of the bit which is normally referred to as a pattern bit. I certainly would not recommend a pattern bit that long or in that situation without using an offset base on the router (use our Community Search for that if you aren't familiar with them). Normally only about 40% of the routers base is supported on your work which would make it easy for the router to tip and the tip of the bit could dig in and you lose control. If you do use a router then use a flush trim bit which will put your template on the far side of your work from you. Nick may be right in suggesting that you just jigsaw as close as possible and the sand to finish. It probably doesn't have to be perfect, it just needs to be good enough to fool the eye.


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## Duct Tape (Jan 5, 2016)

Nope, doesn't have to fit anything. Just please me.


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## old55 (Aug 11, 2013)

Welcome to the forum Jon.


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## Herb Stoops (Aug 28, 2012)

Duct Tape said:


> Nope, doesn't have to fit anything. Just please me.


I would cut it with a jigsaw like suggested and if you can get a hold of a belt sander to finish off the cut they are easy to control and will do a nice job. I imagine you are going to coat it with resin anyway.

Looks like you are doing a good job, I have built several prams and row boats and they are fun to make. All plywood with fiber glass over.

Herb


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## Stick486 (Jan 4, 2013)

Duct Tape said:


> Nope, doesn't have to fit anything. Just please me.


jigsaw and the belt sander...


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## Duct Tape (Jan 5, 2016)

Thanks all. I appreciate the warm welcome and all of the good advice. Seems like a nice place. 

I do have a belt sander, and a power planer. My kids like to make fun of my love of my shop and tools. Their favorite quote (which I don't completely recall actually saying) is a reply once to their question of where I was going, "out to the garage to look at my tools". 

Working on setting up my NYW style router table and Woodpecker top and lift, after retiring my old table and 690 Porter Cable. It was a good Christmas.


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## Cherryville Chuck (Sep 28, 2010)

Duct Tape said:


> Thanks all. I appreciate the warm welcome and all of the good advice. Seems like a nice place.
> 
> I do have a belt sander, and a power planer. My kids like to make fun of my love of my shop and tools. Their favorite quote (which I don't completely recall actually saying) is a reply once to their question of where I was going, "out to the garage to look at my tools".
> 
> Working on setting up my NYW style router table and Woodpecker top and lift, after retiring my old table and 690 Porter Cable. It was a good Christmas.


Your kids aren't allowed on the forum then. We don't appreciate having people make fun about tool addictions.:smile:


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## Stick486 (Jan 4, 2013)

cherryville chuck said:


> your kids aren't allowed on the forum then. We don't appreciate having people make fun about tool addictions.:smile:


*snork!!!!*


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## Multiwood (Feb 24, 2013)

Welcome to the forum Jon.


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## marecat3 (Nov 30, 2010)

welcome Jon


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## Bodger96 (Mar 18, 2014)

Welcome Jon. I used to restore antique wooden boats and the cut close and then router to finish with a template and router with pattern bit method is the one I would use. The pattern bit I use a lot is 1 1/8" dia. with 1 1/2' cutting depth, the first pass would be with the template in place and the second pass would use the transom it self as the template, light sand to finish.

Regards Bob


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## DesertRatTom (Jul 3, 2012)

Forgot to add my welcome. Tool addiction is a good thing! Ask your kids what's wrong with them that they don't enjoy power tools? Turn the tables. Rag on them a bit until they get the point. From then on, you'll probably get Big Box gift cards for Christmas and birthday. Can't go wrong getting dad a gift certificate for his shop stuff. You can also add a public wish list for yourself on Amazon. Put up stuff you'd like to get on that list. Let them know your list is up there and see what happens. 

My wife and I buy our own Christmas gifts, or give a specific list of stuff. I got a box joint jig and a Work Sharp chisel and plane iron sharpener this year. Can't believe how easy it is to sharpen stuff.

I like what you're doing with the boat. Do you do much whitewater running?


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## Duct Tape (Jan 5, 2016)

DesertRatTom said:


> I like what you're doing with the boat. Do you do much whitewater running?


I've been a river runner for a long time. Most recently we've been fortunate to do some private trips on the Salmon, Rogue, Green (Lodore), Green (Deso) and Colorado (Cataract). All in self bailing rafts or catarafts. Some of those rivers I would take the dory, but not all. I'm waiting to hear from this round of river permit applications. 

I've never been down the Grand but that's my ultimate goal.


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## tacomamacxtech (Mar 31, 2009)

Because of the many layers of veneers which change direction, I would use a recip saw and then a sander of some sort. Possibly rough to the line with a belt sander and then finish with a palm or disc. sander. The router suggestion is good if you have a 2+ horsepower router with 1/2" carbide bits. Plywood is rough on bits

Joe


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## Stick486 (Jan 4, 2013)

tacomamactech said:


> Because of the many layers of veneers which change direction, I would use a recip saw and then a sander of some sort. Possibly rough to the line with a belt sander and then finish with a palm or disc. sander. The router suggestion is good if you have a 2+ horsepower router with 1/2" carbide bits. Plywood is rough on bits
> 
> Joe


that assembly doesn't stand a prayer against a Progressor blade...


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## Duct Tape (Jan 5, 2016)

I thought I would reply with an update of how I ended up with this. I decided to scribe a smooth arch with a batten on the back. Then cut just proud of it with a jig saw. The cut is angled 25 degrees toward the boat interior to match the angles of the side panels. Then I hand planed and sanded down to my mark.

Didn't use a router for this I'm sorry to report on this router forum, but have attached some pics of the next step where I used a Bosch Colt (great tool) to rout out the top edge of the foam b/w the fiberglass which was then filled with resin and Cabosil. Plus, the next thing up will be to build the frames which support the hatch lids. My plan is to rout out the water drainage channel and recess for the weatherstrip on my router table. 

Thx again for all of the help. 

Jon


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## Duct Tape (Jan 5, 2016)

Most of the pics didn't go through. Will try again.


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## Duct Tape (Jan 5, 2016)

Hmm. Maybe I'm limited to one pic or a size limit on this iPhone. Will try to get back later with a couple of more. 

Jon


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## Duct Tape (Jan 5, 2016)

PS. Progressor blade. Thx Stick.


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## Stick486 (Jan 4, 2013)

Duct Tape said:


> PS. Progressor blade. Thx Stick.


sweet...
aren't they...


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## DaninVan (Jan 1, 2012)

Hey, Jon; welcome!


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