I’ve come up with a tool for reproducing rails from 2d designs. I made a prototype from scrapbox materials and it works quite well.
The bit with the sandpaper on is hinged and it rotates in and out I’ll call this the “tool section”. You set the angle of your band by rotating the tool section and then tighten the nuts to lock. The slotted metal bits on either side of the tool section with the sandpaper are from cheap angle guages. The tool section is attached to another piece I’ll call the “slider section”. The slider section is made from two pieces of aluminium c section with pieces of three ply on top and bottom to form a kind of box. the bottom piece has a slot cut in it. The third piece - the "bottom guide"slides in and out in side this slot.
You can see how the bottom gauge is made of two bits of decking held together with a small shelf angle.
How does it work?
First design your rail at the widepoint in some design program - illustrator, turbocad, whatever
Printout your rail design full size, and draw tangents to your rail curve. Draw a vertical line at the edge of your rail and plot the points where the tangents intersect. Assuming you’ve skinned your blank, cut and squared up your outline and profiled the deck, you’re ready to do the rails - do not shape the bottom of your rails yet - you need a right angle to slide the rail band tool along.
Now mark the tangent intersection points on your squared up rails at the wide point. Place the rail band tool on the print out and set the tool section to the angle of the top band. Place the tool over the rail sandpaper on the top of the, rail guide section against the bottom of the board. Now with a light touch slide the tool along the rail keeping the guide section up against the bottom of the blank. You keep a light pressure on the tool section The slider section will move in and out as you move over the rail. I start at about a foot from the tail and do right up to the nose and then do progressively shorter strokes so I get a harder top rail near the tail that blends into the full profile at the wide poit. When you’ve hit the mark on the rail for the top tangent, you flip the blank and do the other rail. Next you set the tool section angle for the next band mark and repeat the process. Scren and blend the bands as usual and the then do the bottom of your rails.
Things to watch out for - make the bottom guide piece fairly wide and make sure its edges are rounded - you need to be careful not to put gouges in the foam on the bottom.
Don’t make your top tangent too flat - the slider tends to stick. Three fairly steep bands is about right. I usually get enough of a band going to rest the planner on and use that to take the foam down quicker.
I took a piece of very course sand paper and wrapped it on the rail of a board I liked. Then I ran a chunk of 2" thick high density foam over it until the rail shape was cut into the foam. I think I went in about 2 or 3 inches.
Then I place sandpaper inside the curve and run it over the rail of a board I want to shape. You could also glue some paper in there, but then it would be harder to change.
I used to use this to get a basic shape going on the EPS boards we do.
It’s really easy to make these and you can make different shapes by running the foam over a different rail.
I had a rail band from a 2" EPS blank and cut a small chunk about 4" x 2" x 2" from that. I took a piece of 80 grit sandpaper and placed that over the rail of one of my boards. Then I took the foam and cut a v into it and ran that v over the rail until it had the shape of the rail about 2 or 3 inches deep.
It only took a minute or two to do.
Then I place sandpaper inside the foam tool with the grit facing out and run this over the rail of a board I’m shaping. I creates the same curve really easily.
I need to make a new one, so I’ll take some photos and post them. I’m going to use the blue dow foam cause we have some left over.
We do solid rails now, so I need to make a tool with about a half inch flat section. Just use this to get the rail curve started so we can laminate the bottom skin without shaping the whole board.
Reverb, it makes sense when you visualize that he puts the sandpaper on his finished/master/sample rail grit out. That way, rubbing a piece of foam against it makes the female version of the rail profile. And then you glue new sandpaper inside that female version, also grit out, and rub that against your templated blank to reproduce the new (male) version of the desired rail.
Sounds like a good trick. But doesn’t the thickness change too quickly from end to middle and back to the end to make it very useful? Maybe I’m used to longboards that foil from 1/2" at the ends to more than 3" in the center. You’d need a new profiler every 18" or so, and then would still have to blend that all together.
Conversely, something like that would be most useful on something like Roys’ “Parallel Profile” where board & rail thickness are constant over the entire length.
