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Building a Traditional Wooden Boat #6: Stem and Knee - Part 1

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Blog entry by MattD posted 07-22-2009 03:20 AM 14450 reads 1 time favorited 4 comments Add to Favorites Watch
« Part 5: Building the Transom Part 6 of Building a Traditional Wooden Boat series Part 7: Stem and Knee - Part 2 »

I’m starting construction of the stem and knee by making sure that I have these parts drawn correctly on the full size drawing (lofting). I could really use some advice before I actually cut out the parts!

The photo below is the front section of my lofting. I used photoshop to make the lines and sections of the stem more visible. The stem is actually two parts as shown in the lofting below. The red section is the stem and the green section is the knee. I’ll make luan templates to cut these pieces from white oak and bolt them together.

Stem Lofting

After cutting out the stem and knee, the challenge will be to carve out a rabbet that will receive the planking. This is what it should look like:

In my first lofting photo above, the two solid black curved lines represent the rabbet and bearding lines which will be used as the reference to carve out the rabbet to the depth of the planking (3/8”).

It’s important to note that the lofting shows the profile view (side view) and half-breath view (top view of half the boat) on the same drawing. The light grey lines are waterlines for the profile view and the blue lines are water lines for the half-breath view. These waterlines represent heights every 3 inches and are very much related to each other to determine the overall shape of the boat.

The rabbet line is determined early in the lofting and is drawn in the profile view using a batten to establish a fair curve from the tip of the boat to the bottom keel. The bearding line is determined from the angles of the planks at different points where they intersect with the stem. These angles are shown in the half-breath view as solid blue lines. These lines are like a contour map of the hull and meet the center stem at different heights and angles. For example, the lowest blue line shows how the outside of the plank will meet the stem at the rabbet line at a height of 6”. The planks will be 3/8” thick, so I drew a parallel line 3/8” away and noted where the inside of the plank would intersect the stem. Using a square, I then placed a mark on the profile view at the same point 6” in height on the stem to indicate where the bearding line should be for that point. The same process is done for the waterlines for other heights, 9”, 12”, 15” etc. and the marks are connected with a batten to form the entire curve for bearding line.

Need some advice:

As detailed as this may seem to be, I’m not 100% confident that the rabbet will be perfect if I carve it all out on the bench from these measurements. I’m trying to decide if I should carve out just the top section on the bench and complete the bottom section after I put the stem in place and can do some test fitting and final carving with everything up on the molds. Any advice here would be greatly appreciated!

Lessons Learned:

When trying to work out how to fit the keel to the stem knee on the drawing, I realized that my original drawing of the stem profile was off. It didn’t fit the measurements from the blueprint. The keel would have had to curve up sharply to meet the stem and other parts wouldn’t fit according to the plan, such as the mast step. I had to re-loft the entire front end, moving the profile of the stem out about an inch. Fortunately, the changes were slight enough that they had no effect on the rest of the drawing including the station molds, which I had already built. Next time, I think it would be a good idea to add more details earlier in the lofting to make sure everything fits before cutting any actual wood.

Also, an observation I’ve recently made is that I’m really starting to be able to think through solving problems with this project much easier than when I started. For example, working with the relationships between the different views of the boat was very difficult at first. I think I owe this to reading, practice, writing this blog and getting some tips from others on here. I’m nowhere near an expert or anything, but I’m no longer entirely fearful of this project.

Materials List:

None!

Project Materials Summary:

  • Plans and Book: $60
  • Lofting Supplies: $47.88
  • Mold Supplies: $36
  • Strongback Lumber: $33
  • Transom Materials: $22

- Total Project Expenses so far: $198.88

Labor Hours Summary:

  • 5/29/09 – 6/8/09: Lofting – 12 Hours
  • 6/14/09 – 6/20/09: Building Molds: 5 Hours
  • 6/25/09 – 6/27/09: Building Strongback: 7.5 Hours
  • 6/30/09 – 7/13/09: Building Transom: 6 Hours
  • 7/14/09 – 7/20/09: Stem Lofting Detail: 3 Hours

- Total Project Labor Hours so far: 33.5 Hours

-- Matt - Syracuse, NY



4 comments so far

View a1Jim's profile

a1Jim

112165 posts in 2243 days


#1 posted 07-22-2009 03:24 AM

Hey Matt
This is a great blog it’s super interesting and great idea to include time and materials

-- http://artisticwoodstudio.com Custom furniture

View patron's profile

patron

13064 posts in 2007 days


#2 posted 07-22-2009 04:55 AM

as i’ve stated before , you want to to know where every fastener goes ,
so they don’t weaken the frames or cross each other later in the building ,
or if you add something later .
i’m really proud of you for learning all this ,
it will make your boating a real pleasure !
and thanks for sharing .

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

View Pete_Jud's profile

Pete_Jud

424 posts in 2419 days


#3 posted 07-22-2009 06:21 AM

Back in the 80’s I met a man in his late 80’s in a small village in Alaska, he cut all of his knees from old growth cedar stumps that he pulled out with horse teams and left to dry for 5 years before he built his boats. I rember coming back after a fishing trip and asking him if he built that boat, he looked at the marks, and told me that it was built in 1937 by him.

-- Life is to short to own an ugly boat.

View Splinterman's profile

Splinterman

23058 posts in 2027 days


#4 posted 07-22-2009 11:18 AM

Hey Matt,
Glad you are makeing steady progress…......take your time…..measure and check three times…..cut once.
The stem can be cut a number of way’s using very sharp chisels or even a router if you feel comfortable.
Do as much work on the stem as possible…off….the jig.

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