Sep
27
Written by:
Tom
9/27/2009 10:02 PM
There's a lot of time spent measuring and drawing boats in the first month.
If you're going to restore a boat to its original shape, it helps to know how to measure the boat that you have before you. After all, how are you going to know if the boat you're working on is straight and symmetrical without having a way to measure it?
And if it is straight and symmetrical, who's to say that it's the right shape? Perhaps the boat has been pulled out of shape by the weight of an oversized engine or sailing rig tuned too tight. Measuring the boat will allow you to draw the boat, and if you can draw it, you can start to see strange warps in the shape that will tip you off to problems that you couldn't pick up with the naked eye.
One of the ways that we measure boats at IYRS is by building a frame around them
and then putting rosin paper on the frame, and tracing the shape of a measuring stick onto the paper while it touches a point on the boat. By tracing the stick's position as it touches a variety of points on the boat, you can get a sort of map of the shape of the boat in the plane of the frame.
Here's an example of the rosin paper tracing:
Not the best photo, but you can see the lines on the paper where the stick was. These tracings are used to transfer the measured points to the lofting floor where the points can be connected into curves representing the shape of the boat in one plane.
It's a lot like creating images of bread slices. The frame is moved down the boat
and another set of measurements is taken. Eventually, you end up with a series of slices of the boat that can be used to draw the boat from any perspective, top-to-bottom, side-to-side, or front-to-back.
The 2nd year group working on the Gar Wood power boat used a transit and water level to level their boat from side to side and front to back.
The person on the transit can make sure that the waterline is perfectly level from the front of the boat to the back. The people at the boat are holding a clear tube partially filled with water that stretches to the other side of the boat.
Since water seeks its own level, they know that if the water level is just at the waterline on the starboard side of the boat, then the water level in the tube on the port side should be exactly at the waterline there as well if the boat is level from side-to-side.
By raising and lowering the boat with jacks on either side, they can make sure that their boat is level. Now when they measure it (using that light frame, shaped like an upside-down L in the photo above), they will be sure that the boat they are drawing is level on the lofting.
Not only do you want to make sure that the boat is level, you also want to make sure that it's straight. One way to do this is to suspend the boat over a grid with a straight line down the middle. You can then position the boat so that the centers of the transom and stem are exactly above the drawn center line.
We use plumb bobs for this.
At least one student is expected to say "Plumb Bob Square Pants" during this activity.
For those of you who recall that in the last blog we said that the 2nd years would be working on one motor boat (the Gar Wood) and two 12 1/2's… well you may have been asking yourself about the boat in the last 2 photos. Extra points if you were scratching your head and saying, "That's no Gar Wood!" Correct! In fact, it's a Chris Craft. The class opted to restore two power boats and one sailboat this year. There will be no shortage of learning about engines for these folks.
Back to lofting...
There's a lot of time spent making very precise measurements, transferring them to the lofting floor, and then connecting the dots with fair lines.
Here some first years are using a flexible batten to create a smooth, fair line between a series of points.
The end result can look confusing to the untrained eye
but it all starts to make sense the more you know about what you're looking at. Really.
Of course, just because you know what a line represents doesn't mean that you actually LIKE that line.
The crew of 2nd years working on the 12 1/2 liked the lines they arrived at for the body plan view of their boat, using Herreshoff's original offsets.
Still, those lines didn't translate into long profile lines that they liked, so they spent a lot of time working out why. Here, 2 students are using a long batten to connect points derived from the body plan.
And then, scratching their heads over how those nice initial points led to a funky wiggle in the long lines. Here, instructor Warren Barker helps them sort this out.
Or at least helps them to get comfortable with the fact that most lofting involves a lot of trial and error (and no small amount of art).
Lofting is really one of those tasks that can induce Exploding Brain Syndrome (EBS).
So, before losing the capacity for rational thought all together, sometimes it's good to take a break and do a task that's a bit less heady. Seeing exactly how some of the wood for your boats turns from tree to lumber is just the ticket.
Over in the Coronet building behind IYRS, former student Ken Beck (2009) used his Wood Mizer portable sawmill to saw the oak for the beetle cat coamings.
Starting with a large log, Ken squared it, cut it in half from top-to-bottom
and then sliced it horizontally.
The result is a set of perfectly matched boards (called "bookmatched") that will make the coamings look extra nice.
Another thing that the students are learning is how to anticipate problems when drying wood. They learn that if wood dries too quickly or unevenly, it will warp and split in undesirable ways. They learn to coat the wood with shellac to slow down moisture transfer from the drying wood.
They coat both sides of each board as well as the ends.
And they learn to properly sticker the wood to promote even airflow around the boards.
The wood is stacked in the same order that it was cut, so that it's easy to later choose bookmatched boards for the coamings.
Now that's a nice stack. These boards will be covered to keep them out of direct sunlight, and stored until used. That should be sometime around April 2010.
Not the most exciting work, but it's a important stuff to know and it beats having your head explode.
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2 comment(s) so far...
Re: Lots of lofting
Tom,
It's great to see that you are still connected to IYRS. You have has a wide variety of experiences over the last several years...restoring Madcap, building a six and now using your knowledge and writing talent to continue your work with IYRS. I hope you were able to see some of the Six Metre Worlds racing. It sounded like lots of NE wind on seveal of the days. This blog and the story it tells is very interesting. May the breezes continue to be fair for you.
Marilyn Williams
By Marilyn Williams on
10/7/2009 7:30 PM
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Re: Lots of lofting
Thanks Marilyn,Sorry, but I never did get to come up for the World's. It's a little hard to enjoy racing from shore, and I didn't have a boat to jump on. The best place to see them of course is as a participant! I like coming back to Newport weekly to hang with the students for a while and do these little reports. Even though I'm working in the field full time, it's a good practice to keep coming back and thinking about the basics.
By Tom on
10/7/2009 7:39 PM
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