measuring the hull

[werner]

Hi,
Would like to hear about an "easy"system to measure the old wooden hull (35') and drawing a line plan before changing the shelf .on sight there seems to be something slightly assymetrical.
although checked with battens and then no major problem shows.
What kind of contraption have I to make for this reverse lofting?
the hull isn'standing on a level floor .
Read that a laser is used for precision(how?)

Tought about a line from stern to bow on deck and another on the floor as ref.lines cutting the boat virtualy lengthwise in half. Then measuring, with some kind of"jig" ??from always the same distance from these lines(forming vertical plane outside the hull), at fixed heights and angles the distance to the hull.
any ideas?
regards,

[Lucky Luke]

Plumb line, tape meter, long straight edge and level gauge (including a long hose). That's all what's being used when measuring a hull for the IOR or other rules. And that's accurate. No matter what the ground may be like, or how the boat sit in it's craddle , but be ready for a some geometry. ;)

Edited to say: "start right, end right"...and if it looks right, it's right.

[ 01-27-2004, 09:28 AM: Message edited by: Lucky Luke ]

[Nicholas Carey]

About the only book I know that describes the taking off of lines is Wooden Boats: A Manual for their Documentation (http://www.maritime.org/msca/MSCAPublications.html) (Museum Small Craft Association, 1993).

I believe it's available from Our Sponsor (as well as, I'm sure, The Usual Places).

This article (http://www.loc.gov/folklife/maritime/twoarti.html), published by the Library of Congress' American Folklife Centre, lists some other sources of information as well.

Your reference librarian is your best friend.

And even if what you need isn't in your local Building Where the Book Live, they can probably get it for you through interlibrary loan.

[ 01-27-2004, 12:39 PM: Message edited by: Nicholas Carey ]

[Bob Perkins]

There was a good article a few issues back in WB on taking off lines using a laser level..

I don't remember any of the particulars except remembering it seemed like a good method.

[werner]

could order a backissue? In what WB was this method described??
thanks for your replies

[Gary E]

Werner,

Measuring the hull can be construed to mean many things. Before you develope a method ask yourself several questions.

..How accurate and repeatable must he measurement be?
The smaller the error allowed the more complex, time consuming and therefore expensive the measuring system must be.

..After you have the measurements, what will you do to alter the current shape if it falls outside your specified error? Again, the smaller the error allowed the more time and expense consuming it will be.

G

[Basir]

For getting the boat level and plumb in all directions, a water level is indispensable. As for taking off lines, another article that might be helpful was in Maine Boats and Harbors magazine sometime in 2000 about how somebody took the lines off of an old Frost lobsterboat for the Frost Torpedo built by Rumery's boat yard. If I remember correctly it was a low-tech method using string, eyeballs and math. Seemed very sound and fun to me.

David

[davef]

Depending on your requirements for accuracy I have used the following method that might work for you. I've tried to illustrate it on the following picture. No math required and it was very quick.

a)park the boat next to a flat wall or strike a line on the floor that runs parallel to the cl of the keel. you can also use a board or rod that you level as you move it along the length of the hull.

b) mark two horizontal lines on the wall (or mark two lines on your movable board.

c) carefully stretch a taut tape measure from each line to a point on the boat. Record the two different lengths as L1 and L2. If desired, you can use this to spot in chines or you can simply take enough measurements to loft a fair line.

d) On paper (or in any CAD system) you can strike radii = to L1 and L2 from a distance H on a flat line and the point at which they intersect corresponds to that point on the boat.

e) move along the length of the boat and continue.

Hope this makes sense. I used this method and got pretty good results in short order.

Perhaps this will help. Best of luck to you.

-Dave

http://www.imagestation.com/picture/sraid102/p7d929c378d4fd6542d1cd189d636a210/f9c930a4.jpg

[mic]

Hi Werner, Bob is absolutley correct Wooden Boat magazine number 167 August 2002 on pages 34 to 41 has a brilliant article about getting a set of lines drawings with a laser level. Good luck Mic ;)

[werner]

Many thanks to all,
will try to get hold of that WB issue
and ask someone to help it doesn't look like a one man job

Or post the boat to this firm ? http://www.capture3d.com
(I knew there had to be a modern way to get it realy right!!!)
:D
regards ,
Werner

[FG]

Is the wall straight? You can measure from any plane you can stretch a tape to from the hull. Inaccuracy results most when your angles from the plane to the hull is small.. that is why you have half breadths and depths in canoe offset tables. My first inclination is to find a straight 10' 2X4 and 4 straight 8' 2X4. level 8 points on the floor and set up under the keel and out perpendicular to the keel at 8 foot spacing. Grid on top of the 10 footer laid across the 8 footers. Not a lot of setup and easier to be sure you are perpedicular to your points using a plumb bob than a level from the hull.

[paladin]

Werner...
I am really slow these days.....but I can send you a dvd that details how to take lines off a boat the easy way..by hand, not laser....but it will take about three weeks to get it to you if you send an e-mail to me with your mailing address......