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Discussion Starter · #1 ·
Hi,
I have to manufacture new cap rails for my sailboat. The wood I will be using is Iroko and I will be cutting the new curved caprails out of 6" X 8' 7/8 inch boards. Each segment of the cap rail will need to be 1 3/4" wide X 8' long. A 1/4" deep X 1 1/2" rabbet will need to be cut on the underside of each caprail. My question is how to best accomplish this with a portable router both in terms of stabilizing the caprail to the work bench and best type of bit to use. Remember that each caprail segment is curved.
Thanks,
Marcelo
 

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Marcelo - this is where photos, sketches and drawings can help us help you the most.
a cross section drawing of the cap rail with measurements would be fantastic.
and - photos of your boat. (and how big is it ?).
 

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How many rails do you have to do?
It may pay to create a template.
 

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I think ifthere is any curve to the sides of the boat, that you'll almost certainly want to create a template. If the curve is the same both port and starboard, you can flip it over for the second one. You can trace the pattern onto the wood you're using, then rough cut it and so some hand work to get the shape and size just right on the template. Once the pattern is smooth as a baby's behind, you can use it to outline the shape on your final material, then use a jig or band saw to cut the shape, leaving a little proud. You can then use a trim bit with a bottom mounted bearing riding on your perfected pattern to do a nice, clean final work piece. If you have a boat that requires it, you can cut a groove on the underside to match the top edge of the boat. I'd clamp that thing down and mark the groove carefully. This is a general process, but I think it's what you're looking for. I don't think you can hand shape the final wood piece so it matches exactly. That's why you make and perfect the pattern. I'd probably use a strip of half inch MDF for the pattern. You can hold the pattern in place with double stick tape.
 

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Discussion Starter · #5 ·
I think ifthere is any curve to the sides of the boat, that you'll almost certainly want to create a template. If the curve is the same both port and starboard, you can flip it over for the second one. You can trace the pattern onto the wood you're using, then rough cut it and so some hand work to get the shape and size just right on the template. Once the pattern is smooth as a baby's behind, you can use it to outline the shape on your final material, then use a jig or band saw to cut the shape, leaving a little proud. You can then use a trim bit with a bottom mounted bearing riding on your perfected pattern to do a nice, clean final work piece. If you have a boat that requires it, you can cut a groove on the underside to match the top edge of the boat. I'd clamp that thing down and mark the groove carefully. This is a general process, but I think it's what you're looking for. I don't think you can hand shape the final wood piece so it matches exactly. That's why you make and perfect the pattern. I'd probably use a strip of half inch MDF for the pattern. You can hold the pattern in place with double stick tape.
 

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Discussion Starter · #8 ·
Thank you all for the input. At present, I have a router, a router table, a circular saw, a good jigsaw and hand tools (chisels, planes, etc) I don't mind investing in a band saw if that is needed to do this job well. I have been toiling with the same general approach that desert rat tom has of creating and perfecting the templates, cutting the Iroko with the jigsaw slightly oversize to the pattern, and then using the router with a flush blade. The part that is a bit concerning to me is how to cut the large rabbet underneath the rail since it is on a curve. I can see that being an issue for the router table.
 

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one minor alteration worth considering wound be to make the outside edges flat vs rounded over. Then the top corner could be easily rounded over with the hand router with minimal effort. The inside edge also could be altered a little if you were flexible in not keeping the bull-nose rounded edge. That is more difficult because of the inside radius. making a couple of "prototypes" out of soft pine and study the methods that you will have to use for the final project with your available tools. (your call).
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(and as Lt. Columbo says - oh wait, there is one more thing).
my experience with double fixtures put together like in this photo, the "engineers" that assemble the two pieces together in the plant don't always get the same exact dimensions throughout the project. so don't get frustrated when the cap rail doesn't fit exactly. Just be prepared to make "adjustments" as you go along.
please keep us in the loop with some photos as you go along.
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Discussion Starter · #12 ·
Today I took a 1 X 6 X 8 board of pine and laid it on top of the rail from the bow back to just get a general feeling for my plan. It is in the first 6-8 ft that the curve of the hull is the greatest. I found that due to obstacles like the stanchions which are 1 1/2 inches in from the rail prevented me from utilizing the width of the board to its max capacity so that after the 4th foot the board stuck out over the side and no longer followed the curve. Is there any other way to recreate the curve on to a wood pattern other than laying it on top of the gunwale and tracing it from underneath? Perhaps when they built the boat back in 1970, they cut the rails straight and then bent them using steam.
 

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you can tell by the grain of the existing wood if it was steam bent or cut from the board to the shape needed.
if I have to work around obstacles, I would use a long sheet of paper to make a paper template then transfer that to the wood. tape or glue copy paper together to make the length you need. whatever it takes. the heavier the paper, the easier it is to work with: brown craft paper, cardboard, etc.
Edit:
looking at your photo, I would tape some cardboard together to get the profile accurate.
removing all the obstacles is not the best option.
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Discussion Starter · #14 ·
That sounds like a good plan. I will give it a go. My plan is to first remove the existing rails and base the pattern on the raised fiberglass contour on which they sit rather than tracing over the existing rails that with time and repeated sanding will not be true.
Thank you for all your input!
 

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Discussion Starter · #16 ·
Yes, I thought of that too but I am concerned about the wood springing slightly out of curvature once released from the boat and because it has been sanded repeatedly over the years it is no longer true to the hull shape as it once was. However, if all else fails, I still think it is an option.
 

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Back again. Looking at your picture, it dawned on me that you can simply take the old rail off and use it to trace onto your new piece. It will also give you exact locations of screw holes and any under side cuts..

If the wood isn't wide enough for the next four feet, you can use waterproof glue and glue an additional piece to widen the piece. Water proof glue for sure, but also either T&G or a long spline to reinforce that lateral joint. It would look something like this: Red lines represent the cut line. You could even trim some of the end of the top board to add to he smaller add on.
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Discussion Starter · #18 ·
Great idea Desert Rat. The reason you see screws exposed is because after years of sanding prior to varnishing, the wood thickness is down by 75%. Normally, the screws are inset into the wood and the holes are covered with bungs. I guess that after so many years of being on the boat, the rails won't change shape much after I unscrew them. I am concerned about that.
 

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Discussion Starter · #19 ·
I plan on making my templates out of 1/2 inch MDF after tracing them from cardboard marked along the hull of the boat. Once I cut the Iroko boards a bit proud, I will route them to the templates. Should I position the templates above or below the Iroko? I plan on using a handheld router not a table. I presently have a flush cutting bit with a bearing on the bottom but if necessary I will purchase one with the bearing on top.
 
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