Scribing Awkward Shapes

Hi,
Does anyone have any tips on how to scribe wooden panels into awkward places like the bow for instance ? I am making a bow locker for my ground tackle and the curved V shape is proving a problem to scribe properly.

 

One method is to to create a reference some convenient distance from the surface you wish to scribe to, (or capture). You do this with a straight piece of lumber, nearly anything will do here, appropriately sized... say a 1 x 4 inch board, or a 3" or 4" piece of 3/4 ply. Make the length as needed to clamp (or fasten some way) to something overhead (eg: the deck beams), and something below ... eg: the floors. Clamp this fairly close to verticle, but it need not be perfect in this regard.

Then cut a bunch of light pine molding strips longer than needed to span the distance from the upright "baseline" to the surface... 1/2 inchers will do.. whatever you have. Cut as many as you need to create points along the curve you wish to emulate. (The more points you use, the more accurate... but this need not be carried too far.)

If you want to get fancy, bevel one end of these quickly to create some sort of actual point. If not, just mark which corner of the strip actually contacts the curved surface in the next step with a felt pen.

Next lay a strip along your clamped upright and advance it until the tip touches the hull curve. Fasten the strip to the upright here. Using a hot glue gun probably works best for this. This will be fast, and strong enough for this purpose, sets-up quickly, and allows you a second or two to move the strip around for final positioning, if needed. Just holding this against the upright for a minute or so with your hand should be adequate clamping.

Note that your pine scribing strips do not have to be horizontal or parallel to each other, and won't be.... and no measuring is needed. Take care, however, to be certain that the points do, in fact, contact the hull curve once glued to the upright reference. Where the hull curve is changing, or where the shape you wish to capture is irregular in some way, you need more scribing strips to get an accurate representation of the shape. You may use fewer wher the curve is more regular, or of greater radius.

You can have lots of these scribing strips glued to your upright at this point. Next, remove the upright, being very careful to avoid disturbing any of your glued scribing strips. Lay this whole deal down on a piece of ply on your shop floor, or on the lumber you will use itself, if practicle. Clamp the now horizontal baseline piece so it cannot move, and then accurately place a mark on the lumber where each scribing point terminates.

If you used enough scribing strips, these dots will give you your curve, and any additional irregularities in shape, if present.

Now use a nice straight piece of light thin pine to use as a spline, or if you have splines already made up for lofting, lay it along these points and carefully draw your nice fair curve ... which should match the hull exactly. If you don't have lead "ducks" to hold the spline in place, nail a thin brad into each of your points, and bend the spline around these.

You have just accurately taken off the needed curve!

Now... the bevel. Because the hull is curving rapidly toward the bow in the forepeak, you will need to bevel the edge of your bulkhead material to match. You could, I guess, repeat the process above... only a bulkhead's thickness forward of where you took the first curve... but that's much more work than needed.

Probably easiest, is to cut the bulkhead unbeveled, bring it aboard, and plane as needed along the forward edge, until the bevel matches the hull curve, and the fit is pretty close. For a chain locker, I would definitely take this route, because any inaccuracies will be on the forward aspect, and therefore invisible to anyone in the focs'l.

If you just have to get it exact, than a another method is to create a horizontal reference parallel to the centerline, and measure the distance to the hull where you took off your first curve, and then take the same measure a bulkhead's thickness forward of this. The difference in these measurements is your edge bevel. You need to do this at several points, but not so many as you used with the scribing strips, as the bevel won't change as rapidly, except perhaps in the way of any unusual irregular shapes.

Trying to describe this process makes it all sound more complicated than it is. It's really pretty simple, and fast, once you get going.

Best regards,
Robert

 

David
Some of the better shipwrights that I have worked with could crank out a shape like that in minutes by just scribing directly onto the panel being installed. But it takes some experience.And at the price of wood these days experience gets expensive. So... the easiest way is to rip strips of doorskin (I don't know what you call it there) into two inch strips and using a hot melt glue gun build a pattern by shaping and gluing pieces together. You can hotmelt blocks to the hull to hold the pattern "in plane". Then using a bevel gauge you lift the bevels and scribe them directly onto the pattern at the location they were taken from. Obviously it is easier to make the pattern fit the big side of the bevel and plane your bevels in from there. If you have a small bevel gauge is the easiest. If not you can make one out of an old hack saw blade. Just bust off two inches of each end and put a rivet or a small bolt through the two holes.
Note: Doorskin here is a light cheap 1/8" luan ply you can get at most lumber yards. We pay around $8/ sheet. Many uses.
Does that help?

 

I make patterns first out of rips ot 1/4" plywood by scribing, shaping and fitting smaller pieces together.
---Joel---

 

Thanks guys. You have all given me food for thought. I get the general idea of how this is acheived and the cogs are going to be turning tonight as to my approach. All The Best.

 

By the way you can cut doorskin easily with tin snips...combined with a block plane it is easy to shape perfect.

 

Use a jogging stick. It is the easiest method. First cut a pointy piece of wood with jogs or zigzags along one edge. It will look like half a Christmas tree. Next secure a board in the same plane of the piece you want to fit. Use the point of the jogging stick to touch the edges and particularly the vetices of the area to be fitted. Trace the jogged side of the stick on the marking board. After you are done, place the marking board over the piece to be cut, position the jogging stick over the traced marks and make a mark at the point of the jogging stick. Connect the dots and it will develop the shape of the piece to be fitted.

 

If it's not a really big part you're making, you can use cardboard and masking tape to make a pattern. The cardboard you usually can get for free and it's easy to cut, and if you screw up you're not out much.

You won't get a perfect pattern but you should get one that allows the final piece to be fitted close enough that you can easily see how much you need to trim it.

Bill H.

 

Any Pictorials??

Gonzo, Sorry but I'm a bit lost on this one. I have studied your post but still can't quite get it. Is ther any sites i can see this being done?? It sounds interesting

 

Without trying to step on Gonzo's feet, the jogging stick will be a piece of wood that will be approximately as long as one half of the panel you are trying to fit. For example, if the panel is 18" wide, make a stick 10". The width of the stick should taper from 2" on one end, down to a point on the other. On the wide end of the stick, cut a series of indentations, say approximately starting 3" from the end, working towards the end. Now, take a thin piece of plywood, or cardboard and temporarily mount it in the area you want to place a panel. It does not have to cover the entire area. Take the jogging stick and place the pointy end on the outside edge where the panel will go, and hold it against the plywood or cardboard. Now take a pencil and run it along the indentations you had cut at the fat end of the stick. Now, go to various points along the area you want to put the panel in, and do the same thing. Once you have a fair amount of points done, remove the board. Place the board with all of the penciled lines on a heavy piece of cardboard. Place your jogging stick on the board, and match the indentations of the stick to the penciled lines. At the pointy end of the jogging stick, place a mark on the cardboard. After you have done all of your points you should be able to connect the dots, and come up with a fairly good pattern for the panel. Cut out the cardboard, and see how it fits. It should be easy to make any corrections. Hope this helps.

 

Be Gad I Think he's Got It!!

I read your post and thought a bit more and then Ker Ching the penny dropped! Thanks for that. I'm off to makemy jogging stick! :idea:

 

I was on the verge of suggesting the same method as Gonzo however I learned it as a tic-stick method. The bevels are the most trying.

added in edit: be sure to mark you points all around the area then you don't need to precisely locate the original position of the record board.

 

Jogging, tick, whatever...

I've had great success with both the jogging/ticking method and the built-up template method. In tight quarters, however, I always use my tick stick. The advantage is that the only attachment that has to be secure is the one holding the reference piece to the boat. There's no worry about accidentally knocking the many small pieces off of the reference piece when you are taking it to your workbench to make the finished piece. On the other hand, the reference piece has to be very secure. If it shifts a bit, you may not know until you are trying to install the finished piece. The template that is made up of many smaller pieces will immediately let you know if it has moved.

If you watch someone doing these two methods and think about it, you will realize that they are really just slight variations on the same method.