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Discussion Starter · #1 ·
I am a model builder and my current project a scratch built Carlo River designed runabout in 1/4 scale. I am about to purchase a router and table, best deal for me ?
My problem is around the deck is a molding commonly refered to as a Monkey Rail, stops ya or supposed to from falling in the drink! anyhow the stock I am using Honduras Mahogany 1" x 1/2" in three segments per side with a radius covering a total of 24" per side. My question is how to router an inside curve, do I need to make an elaberate jig [is there a comercial one] or is there a more simple way also as far as I can tell there are no comercial bit to match the rebate I require.
All help would be appreciated, I can post pictures if that will help
Thanks
David AKA The Brit
 

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Greetings and welcome to the router forum.
 

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My problem is around the deck is a molding commonly refered to as a Monkey Rail, stops ya or supposed to from falling in the drink! anyhow the stock I am using Honduras Mahogany 1" x 1/2" in three segments per side with a radius covering a total of 24" per side. My question is how to router an inside curve, do I need to make an elaberate jig [is there a comercial one] or is there a more simple way also as far as I can tell there are no comercial bit to match the rebate I require.
1. You need to use a circle jig to make the radius, either directly in the work piece or in a template which you then copy with a flush trim or pattern bit. The template will save work when you're making multiple identical or mirror imaged pieces and allow you flip the workpiece so you aren't cutting into the grain like this ->\\\\ which tends to break things.

While commercially available it's about as easy to make one as it is to place a web order. Grab a scrap of your favorite 1/4" or 1/2" sheet good, drill it for your router's mounting pattern and counter sink, see where the center ends up, drill holes for the center of your circles or arcs taking into account that you're going to gain (inside radius) or loose (outside) half a bit diameter, and drill a clearance hole for the router bit.

2. Custom router bits are available. Expect to pay $150+.
 

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Discussion Starter · #4 ·
Hi Drew,
Thanks for the reponse what if the radius is uneven, example at the aft end it becomes almost straight.
David
 

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I am a model builder and my current project a scratch built Carlo River designed runabout in 1/4 scale. I am about to purchase a router and table, best deal for me ?
My problem is around the deck is a molding commonly refered to as a Monkey Rail, stops ya or supposed to from falling in the drink! anyhow the stock I am using Honduras Mahogany 1" x 1/2" in three segments per side with a radius covering a total of 24" per side. My question is how to router an inside curve, do I need to make an elaberate jig [is there a comercial one] or is there a more simple way also as far as I can tell there are no comercial bit to match the rebate I require.
All help would be appreciated, I can post pictures if that will help
Thanks
David AKA The Brit
David,

I've only just researched the Carlo Riva runabouts, but what extraordinary boats! For the curved rail I'd recommend building your own jig for the rail. First, using a jig will ensure the rails on each side of the boat are mirror images of each other. Second, I'd recommend first cutting the rails from scrap wood and tweaking the jig with scrap until it's just the way you want it before using the "real stuff". By then you'll know exactly how it will turn out and have some practice using the jig.

Since you made the jig, tweaking it will be easy as again, you'll have experience with that too. Your router table can be your best friend!
 

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Consider using a multple router bits to accomplish what you can't find in a single bit. Multple passes with different bits or different positions can create almost any pattern. Custom bits are best if you are doing a lot of one pattern. For a small project it is not worth it.
 

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Hi David:

Beautiful boat. Jim and Drew are right on the money. However, the arc of the monkey rail is not consistent through the curve. I'm going to add to Drew's comments and add an elliptical jig. Search the forum for info.

The railroad world used to do complicated layouts for curves. Entry into the curve is an easement that gradually changes the momentum of the train. In your situation, learn from the railroad world. Lay out an ellipse then modify with multiple circles and curves until you've got it "just right." I don't think you'll find one solution that is a perfect fit. You'll have to gradually build up a complex template and tweak liberally as you go. The router is the primary tool and as GNiessen has said, be prepared to use a variety of bits each taking off a tiny bit.
 

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Discussion Starter · #9 ·
I thank you all for the replies, however I have no idea how to make a jig, can you direct me to a source how to plot out the arc, how to make the jig, as a model builder its one thing to use a balsa knife, scroll saw and the like now I'm up with the big boys. Can I impose further the rear cockpit had several variations on Riva boats they could be opened for seats, or as a sun lounge, or as in my case a hatch for the engine access. The hatch has round corners sowith out teaching you to suck eggs you will know the hinges are not regular butt type.They were a curved casting with pin held flanges. I made loads in paper, then ended up with then fashioned from brass and silver soldered. Because this model is scratch built from line drawings no details. Not having during construction made provision for the hinges now I can not figure out how to get the correct arc for the hinges or how to install them, I can not take the deck off for access, pretty stupid of me, any ideas
I have added a picture of my Ariston bow, I have pictures of the hatch and hinges I have made.
Disregard heading of pictures.
 

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Maybe this will help...

Laying out an Ellipse or...

http://www.propdaddycreations.com/DrawingEllipse.htm

There are versions of these pages in just about every language on earth. You may have to go back to your school geometry books.

In your instance, the bow is only a partial ellipse so you'll have to draw a full ellipse then use only a part of it.

As for your hinges, take a look at the door hinges on your car. I don't know where you live but North American cars have an offset hinge to compensate for the thickness of the doors. Some high end boats had the same type of hinge on their engine covers. There a pain to make though. They require some heavy metalwork.
 
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