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Building a Traditional Wooden Boat #2: Lofting

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Blog entry by MattD posted 06-15-2009 04:47 AM 14941 reads 5 times favorited 8 comments Add to Favorites Watch
« Part 1: Introduction Part 2 of Building a Traditional Wooden Boat series Part 3: Building the Molds »

After about 12 hours of work, nearly all lofting is complete and I can finally start some construction! The famous boat builder and author, Howard I. Chapelle wrote in his aptly named book ”Boatbuilding””There was never a boat built in which too much lofting had been done”. By lofting, Mr. Chapelle is referring to the laying out of the lines and drawing of construction details to full scale, a tedious practice he writes ”avoids much trying and fitting”.

Setting up the lofting area

To begin, I cut up a 4×8 sheet of 3/4 plywood to create a lofting “table” that is 12’x32”. This is large enough to draw all 3 plan views (sheer, body and half-breadth) which are drawn over each other. After leveling the table, I rolled out red rosin paper, an option some builders use to draw the plans on instead of drawing right onto the plywood (or traditionally.. the floor of a loft). I then layed out the all important “base line” and tacked a straight edge on that line from which measurements would be made. A large grid is then drawn over the entire area to indicate vertical stations and horizontal waterlines.

Setting up the lofting area

Drawing the Profile and Half-Breath view

There are virtually no straight lines on this boat. I was immediately faced with the problem of how to correctly draw long curved lines. An ideal curved line is a fair curve – one which has a smooth continuous flow to it. It turns out to be relatively simple to do, but does require a good eye. The process essentially involves the use of long wooden battens of straight grain and clear of knots. To create the curve, you “loosely” bend the batten around nails which are tacked onto the “grid” according to measurements in the plans. It’s basically “connect the dots”. The boat plans includes a table of offsets which have measurements for where you place your marks. Once the curve looks fair, you draw the curved line against the batten with a pencil, remove the batten and do the same thing for the next line until you have something that looks like a boat. The following photos show the line for the profile sheer (top edge viewed from side) and a waterline (water level at 6 inches viewed from top). Notice how two different views of the boat are drawn in the same space.

Drawing Profile Sheer and Waterline

Drawing the Body Plan

The body plan is the head on view of the boat and is drawn right over the other 2 plan views that were previously drawn. The measurements are taken from the lofted lines in the previous 2 plan views and the batten is used again to “connect the dots” and draw curved lines for the body plan sections. The body plan shows 7 cross sections of the hull from front to back (stern to transom) with the 5 equally spaced stations in between. The layout of each station are the templates for the actual station molds which will be used later to form the hull. The photos below show the shapes of the hull from head on. The reason for the white paper overlay is to show the construction detail of how the hull planking will join to the keelson and keel on the bottom of the boat. Because there are 7 body sections all overlapping in the same space on the plans, separate pieces of paper are tacked in place as needed for each section so that the details are not a hopeless mess of overlapping lines.

Drawing the Body Plan

Final Results Example

The following is an example of a different boat showing the 3 plan views. In the actual lofting, these views are drawn right over each other.

Final Lofting Example

Lessons Learned
I’m not crazy about the red rosin paper. It has small wrinkles in it that slightly distort the lines. It’s not enough to throw off any measurements by anything more than 1/64th probably, but it’s not ideal. Next time, I’d whitewash the plywood and draw onto that directly.

Lofting Materials List:

  • Red Rosin Paper, Home Depot, $12
  • 3/4 Plywood 4×8, Lowes, $23.88
  • 1×4x12 clear pine, Home Depot, $12

Project Materials Summary:

  • Plans and Book: $60
  • Lofting Supplies: $47.88

- Total Project Expenses so far: $107.88

Labor Hours Summary:

  • 5/29/09 – 6/8/09: Lofting – 12 Hours

- Total Project Labor Hours so far: 12 Hours

-- Matt - Syracuse, NY



8 comments so far

View patron's profile (online now)

patron

13034 posts in 1996 days


#1 posted 06-15-2009 05:09 AM

i built boats for 10 years in fla. i t is a very learning experience , and rewarding !
draw every fastener also , as they can weaken or cross each other in placement .
it,s worth the time to get the lofting right , as it saves time and money (and hair ! ) .
good luck to you , and keep us posted .
i know many l.j.s. are going to be thrilled to see this come to life .!

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

View TopamaxSurvivor's profile

TopamaxSurvivor

14747 posts in 2330 days


#2 posted 06-15-2009 08:16 AM

Sheeh!! I thought all you had to do was throw down a keel, nail on the ribs and plank it:-)) Looks like there is a bit more to it than I thought, eh?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View stefang's profile

stefang

13036 posts in 1989 days


#3 posted 06-15-2009 04:09 PM

This will be fun to follow. I’m never going to build a boat, but I buy Wooden Boat magazine and love the stories about builds and sailing adventures. I used to run a lot of wooden boats in the Navy including the Captain’s gig. I really miss the fun. Unfortunately my wife isn’t fond of the water, so I am now an armchair sailor. Looking forward to the build!

-- Mike, an American living in Norway.

View MattD's profile

MattD

149 posts in 2599 days


#4 posted 06-20-2009 08:56 PM

Thanks everyone for the tips and encouragement.

-- Matt - Syracuse, NY

View a1Jim's profile

a1Jim

112089 posts in 2232 days


#5 posted 06-20-2009 09:24 PM

Very interesting a all new project for me. I’m anxious to see more. Thanks for sharing

-- http://artisticwoodstudio.com Custom furniture

View cylis007's profile

cylis007

56 posts in 2123 days


#6 posted 06-21-2009 12:36 AM

I have already learned a lot, too! Thanks for writing about your experience.

-- A life of leisure and a life of laziness are two things. There will be sleeping enough in the grave. ~Benjamin Franklin

View Splinterman's profile

Splinterman

23058 posts in 2016 days


#7 posted 06-21-2009 03:30 PM

Hey Matt,
Chapelle was right…cannot be too careful with layouts…..take your time.
We do a lot of boat strip planking using WRC and our hull moulds must be spot on.

View Napaman's profile

Napaman

5346 posts in 2732 days


#8 posted 07-22-2009 06:46 AM

wow this is amazing…

-- Matt--Proud LJ since 2007

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