Getting things to bloody fit!

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Rich P
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Getting things to bloody fit!

Post by Rich P »

I've been preoccupied recently with fitting the tops on my bunks, which I imagined would be the easy part! (Yeah right)

As you can imagine, I have to get the curve of the hull, as well as cutting it so that it fits in with the other sections of the bunk top. (because i couldn't make it in once piece otherwise it wouldn't fit through the companionway)
Most of them turned out ok mainly through luck, but the last one which is the hardest as theres no leeway for error because it backs up against a bulkhead on one side and an already fitted section of the bunk top on the other.

What techniques do you lot use for gettings things to fit accurately in these sorts of confines, to the get curve i've been approximating the using a compas, but due to the nature of the hull in that areas that doesn't seem to accurate!
Any help much appreciated!

Thanks
Rich
Preparing a small boat for offshore sailing.
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Rachel
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Re: Getting things to bloody fit!

Post by Rachel »

I've used a couple of ways for similar projects:

1) Make a smaller pattern that's the same shape. Tim details the process here:

http://www.triton381.com/projects/technical/pattern.htm

I recently saw a neat tip wherein someone put a fender washer on a pencil and "rolled" it around the edge to draw the pattern, but I haven't tried that yet.

2) Use a "tick stick" or "tick strip." Info here:

http://www.triton381.com/projects/techn ... kstrip.htm

and here:

http://www.lackeysailing.com/daysailor/ ... kstrip.htm

Rachel
Rich P
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Re: Getting things to bloody fit!

Post by Rich P »

Cheers for the info, they help you get the curve, but then due to them not building the boat straight in the first place I have to make it fit at either end!
Preparing a small boat for offshore sailing.
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jhenson
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Re: Getting things to bloody fit!

Post by jhenson »

I think using a tick stick to transform the shape of a hull to a flat surface like a shelf is an easy and efficient way. Forgive me if you are already using one, but the tick stick is a homemade tool made of straight wood pointed on one end with saw marks at fixed intervals along at least one edge. I label each saw mark with a letter. As the tick stick is laid over a scrap of plywood temporarily affixed in the same plane as the finished piece, lines are scribed using the tick strip edge. Marks are then made at the notches in the tick strip. Make as many lines as you like, but the more the better. You can lay a bevel gauge along the top of the tick strip and note the angle to the hull a couple of locations. I transfer the bevel angles to a separate piece of plywood and assign them to the individual tick strip lines that they were taken from.

Transforming the outline to the plywood you are cutting is done by laying the scrap plywood over the cut piece, and using the tick strip to layout marks along the piece. A flexible batten will give you a good way to connect the dots along a curved edge.

Using this method, I’m usually amazed at how well the piece fits to the hull after initially cutting it to shape. For something like a shelf, I cut it about a ¼” too wide so that the front (the side away from the hull) extends over the edge of the cabinet face. By placing a work light under the shelf, you can see what areas need further shaping to obtain a very precise fit. After I’m satisfied with the fit, it’s an easy task to plane the front of the shelf to match the face frame. However, cutting it oversize doesn't sound like it will work in your case for the piece you describe.

Joe
jhenson
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Re: Getting things to bloody fit!

Post by jhenson »

Sorry,

The reply above by Rachel was posted while I wrote mine. For something of a complex shape, you can't go wrong by building a quick mockup with cheap strips of plywood screwed together to make an outline of you your final piece. A wider section of plywood can be used along your curved hull section.

Also, the tick strip can be used to define staight lines around the entire piece, as well

Joe
Hirilondë
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Re: Getting things to bloody fit!

Post by Hirilondë »

Lots of ways to make patterns and transfer information. When the piece has to be really accurate, like cabinet work, I like making a full size pattern out of strips of door skin plywood hot glued together. I cut, shape, fit small pieces to the intricate details and build up the pattern by gluing these pieces together in place. Tick sticks and spiling (the off set pattern like Tim describes in Rachel's #1) are great for most applications but for furniture grade joinery nothing beats a perfectly fit pattern in my opionion.

For your bunk tops, which I assume are plywood, (you don't say) you can also make them a tad large and block plane them to fit. Transfer the info with which ever method you like and cut on the outside of your line. Then tweak the fit in place. I would think the fit to the hull requires not only a properly fit curve, but a bevel as well. The block plane can address both.
Dave Finnegan
builder of Spindrift 9N #521 'Wingë'
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Rich P
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Re: Getting things to bloody fit!

Post by Rich P »

In theory it needs a bevel, i choose to bridge what gap there is with tabbing!

I'm bad enough at planing a straight edge let alone using it on a curved edge! Still very much getting to grips with carpentry, i'm an aircraft fitter by trade and IMO that's much easier! Haha
Preparing a small boat for offshore sailing.
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Rachel
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Re: Getting things to bloody fit!

Post by Rachel »

Oh right, I completely forgot the glue-gun template method. The funny thing is, that helped me to get a library job once.

I was in one of those interviews where it's you and a large group of people who already work there around a table, and they go round robin asking you questions. Of course they were mostly the types of questions you expect at an interview. However when it came to one particular woman (who was going to be my supervisor, although I didn't know that then), she asked me, "When was the last time you used a hot glue gun, and for what?"

Well, that was an easy one: Not a month before, I'd made a template for a small section of built in counter-top in my bathroom. What made it tricky was that it was boxed in on three sides, and none of them were square. The counter was so narrow that I wasn't going to have a typical backsplash to cover irregularities. So I took strips of thin luaun ply, and used a hot glue gun with them to make an outline template, then cut the wood from that.

That's probably not the only reason I got the job, but it didn't hurt (use of the glue gun on the job was for mending books).

Rachel
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