How can I accurately cut out this hull?

Hey guys. I'm still building the one sheet skiff, and have another dumb question. If you look here, at the plans:

http://www3.sympatico.ca/herbert.mcleod/plans.htm

that's the shape I'm supposed to cut the bottom out in. But is there any good way to draw the lines on the actual piece of wood? I could do that tricky thing where you draw a grid on the paper, then one on the wood... but that's probably stupid, right?

Also...so far I have the sides, with the transom and frame. But I noticed...they aren't even. When you rest it on the ground, it kind of rocks. This means the bottom will have to be slightly twisted. Any advice?

Thanks!

 

One way to get curves is to use a long, flexible batten (board, slat, whatever you want to call it). Put nails at the important points, bend the batten around them. Then either have someone hold it while you run a pencil, or nail it in place temporarily.

But what you should probably do here instead is assemble the rest of the boat first, turn it upside down, lay the piece for the bottom over it, and mark it directly from the boat. String it first, and make sure it's symmetrical. By that I mean run a string from the center of the stem to the center of the transom, and make sure the boat is square and straight.

For those who are curious, here's the home page for the boat:

http://www3.sympatico.ca/herbert.mcleod/skiff.htm

And here's the page with the instructions:

http://www3.sympatico.ca/herbert.mcleod/build.htm

 

I have built the rest of the boat. I was actually thinking of doing that thing with placing the bottom of the boat where it'll go, and tracing it out. But the thing is, the bottom is curved, so I'd have to kind of 'roll' the board with the curve...

Also...haha, my boat is far from even and straight. Like I said, it rocks and it's clearly a little off. I'll get a pic so you guys can have a good laugh.

 

Put some weights on the bottom board at each end, to hold it down while you mark it.

Are your transom and stem permanently fastened already? It's usually better to tack things together temporarily when you can, to make sure everything is lined up and straight.

Yep, show us pictures. We like pictures around here.

 

The curve of the bottom is called rocker and is created when the sides are bent in the horizontal plane and then tipped at the chine angle. I would guess rocker is 3 to 4". The bottom is not flat longitudinally so the finished hull will obviously rock forward and back, but not side to side.

Stretch a string between the center of the transom and the bow to form a centerline, the make sure the hull is symmetrical before attaching the bottom permanently

Viewed from the rear, a straight batten laid between the sides should appear parallel to the edge of the rear plank, or transom. In other words, the hull should not be twisted.

After the bottom is added and the boat turned right-side-up the gussets are added to stiffen the boat. They were not mentioned in the instructions, I assume they fit between the sides and the transom: check the hull is not twisted before adding the gussets or the twist will become pernanent.

This is not a sophisticated hull design and is very small. It is going to feel tippy when you sit in it unless you are very short. Remain seated!

 

Hi!

Think it is better to design these as sheet metal parts, utilizing a capable software.

...
Sorry, I misunderstood your problem.
But, why not printing with a plotter, cutting out, then drawing on the wood?

 

Flat bottom boats are easy. Build the rest of the boat, turn it upside down (or downside up). Put the ply on top. Tack each end down with a nail or screw if you have to. Mark around the chine with a pencil. Cut a bit outside the line (maybe 1/4" depending on how good you are). Nail/screw/glue bottom on. Finish off with a plane and sandpaper. No problem. No need to measure anything.

If the boat is twisted a bit, untwist the silly thing before putting the bottom on permanently. This shouldn't be hard to arrange. Use props, nails, swearing, friends, bad attitude, whatever works. Eyeball it for straight and you're all set.

 

I concur, a one-sheet skiff is quick and dirty boatbuilding at it's minimalist best. Remember, this is carpentry, not cabinetry...an eighth isn't going to matter once on the water.

 

Agreed that an eigth is unimportant, so is appearance. Of course this applies to general dimensions of finished hull. However, good workmanship with well-fitted joints will result in a stronger boat. The most important joints are at the chines and between the gussets, sides and transom.

The stiffness and strength of any structure builds as it approaches completion. The hull will be floppy until the final elements are in place; at this stage it can still be forced back into alignment and will hold the new shape once the final elements are in place.

The effect is particularly dramatic for those boats with decks: when decks are added the increase of stiffness is remarkable. As an everyday illustration of this, try twisting a shoebox, first with, and then without its lid.

Your hull will respond the same way to the addition of gussets, and also to the addition of a breasthook which is a gusset fitted across the sides where they meet at the bow. The breasthook acts like a small deck. If there is not one on the plan, I recommend you add one, about the same size as the gussets.

The joints at the gussets and breasthook can be heavily stressed by a small twisting force applied to the hull which is greatly magnified at these joints. This can be demonstrated by repeating the test on the shoebox after cutting a large hole in the top: it is still stiff, but it is much easier to buckle the top after the hole is cut.

 

Hey guys! Sorry I disappeared for so long. I went hiking for a week, then got sick, then had lots of work to catch up on, then built the boat more!

I'm not done completely, but I did attach the hull (it was fine and easy like you said, haha), so here's a pic:

http://imgur.com/3zBN4.jpg

Now to add oarlocks and paint it two colors! Any suggestions on colors? Oh, also, what type of paint to use? I've already lacquered it like crazy though.

Edit: Ahhh! I used

 

I like a man who builds a boat inside his house. Sense of style.

 

It's in my one of my roommate's rooms while he's away for the summer. He'll never know! Unless he sees all the paint splotches on the floor...

 

I think he'll know! You'll to bribe him with a ride. Looking good. also looking small. Very small. Listen to who's talking, old Mr. boat under one arm and sail under the other himself!