Guy's Wooden Drift Boat Project

Hello Everyone,

 

My name is Guy and this is my first post in this forum.  I am here because I want to build a wooden drift boat and, undoubtedly, I will occasionally need advice of the pool of experts and experienced drift boat builders on this forum.

 

In preparation for this project I have read and studied three books: Drift Boats and River Dories by R. L. Fletcher, Boatbuilding with Plywood by G. L. Witt, and Covering Wooden Boats with Fiberglass by A. H. Vaitses.  I have also developed my own set of construction plans based off of the "Original McKenzie Double-Ender with Transom" in Fletcher's book.  I used and MS Excel spreadsheet to calculate all of the dimensions, cut angles, compound angles, and bevel angles of all frame components and I used Pilot3D software to calculate the as-cut dimensions of the plywood sides and bottom.  At this point I am pretty comfortable with the mechanics of construction and I think that I am just about ready to start purchasing lumber.

 

Presently, I plan to use Meranti Hydro-Tek plywood; 1/4-in. on the sides and 1/2-in. on the bottom.  I found plenty of places to purchase these materials, but they are all far away from Idaho Falls, Idaho, and as a result shipping costs more than the materials.  Are any of you aware of a business within a few hundred miles of Idaho Falls that sells this plywood?  I have a few requests in to the local lumber companies, but I have yet to talk with someone who has heard of this material before.

 

I also plan to use Port Orford Cedar (CVG) for the straight frame sections and White Oak (quater sawn) for the bent frame sections (chine logs and sheer rails).

 

Thank you, Guy

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Permalink Reply by Guy Fredrickson on March 23, 2012 at 11:59am

I was not satisfied with the results of the first scarf cut in the plywood, so I put a 1/2-in. sheet of the hydro-tek on the table and recut the scarf.  This is the result.  As you can see, next to a straight edge, the scarf is still not that good.

Everthing looked and measured pretty square, but obviously it was not.  Then I took a pieced of tapered wood and check the distance between the upper steel tube and the plywood.  I simply slid the wood under the tube and made a pencil mark; then check the mark at other locations along the rail.  Sure enough there was variation.

The result was that I shimmed the bottom of the table in the center along the sawhorse and then clamped the ends of the table to the sawhorse.  In other words, the table was sagging in the center and I lifted it slightly with the shim.  It's still not perfect, but this might be good enough.  The table surface is made from three sheets of 1/2-in plywood (two from the crate and one hydro-tek) and you can still see some waviness.  The shallow 12:1 scarf joint is obviously very sensative to imperfections.

 

 

 

 

 

 

 

Permalink Reply by Greg Jensen on March 23, 2012 at 1:36pm

Guy -

Ditto Mike's reply, just touch up with your belt sander. I tried to use a hand plane but did not have the touch, or the right planer. but some light quick work with a belt sander will do the trick quickly.

 

Greg

Permalink Reply by Mike Baker on March 23, 2012 at 1:26pm

Hey Guy,

I have enjoyed watching what has to be the longest thread in WBP history. Can't wait to see your jig that prevents ring shank nails from bending (I know you are planning one!) I use a jig very similar to make my plywood scarf joints, I always finish them off with a belt sander to get that perfect feather edge.

Mike

Permalink Reply by Guy Fredrickson on March 23, 2012 at 1:50pm

My grandfather taught me a trick with nails to help prevent the wood from splitting.  (He was a machinist.)  Take the nail and grind a wedge-shaped chisel point on the end and place that cross-ways to the grain of the wood.  The chisel point cuts through the grain of the wood, which (almost always) prevents it from splitting.  It works very well.  That's all I got regarding nails.

Permalink Reply by Guy Fredrickson on March 23, 2012 at 1:43pm

Greg and Mike, I used a sanding block and 50-grit.  Like you guys suggested, it helped true it up.  I have never been very good with belt sanders (table or hand); I always take too much off with those things.  Guy

 

 

Permalink Reply by Dave Barnes on March 23, 2012 at 2:09pm

Question, guys. on a shallow scarf joint like this, are there screws involved after the epoxy mating or does the epoxy over such a wide band do the trick? It seems to me if you feather this right, you'll never see the joint reveal. Very cool. If no screws are involved, that is.  I had instructions that called for screws either way, so I thought, "why bother with a scarf joint if all the screws will still be there?" 'course a simple butt joint plays to my craftsmanship skills better.

 

db

Permalink Reply by Greg Jensen on March 23, 2012 at 2:25pm

Dave - with the scarph when you are done there are no screws involved.

When the joint is cured, sand off the excess bleed off and you will end up with a very faint line where the joint is. Also the scarphed joint is now exponentially stronger than the surrounding wood.

On my test with 1/4" plywood I was able to bend my sample piece into the shape of the letter C.

When it finally broke, it was at a point more than 1 inch away from the scarph where there was a small void in the plywood.

Greg

Permalink Reply by Guy Fredrickson on March 23, 2012 at 2:26pm

Dave, I will use only epoxy (with microfibers) to join the scarf joints.  There are no screws involved.  I am joining two 3x8 ft panels and one 3x4 ft panel to make a continuous 3x19.5 ft panel.  I will make two 3x19.5 ft panels and cut the boat's two side panels from the pieces.

 

I will have one butt joint in the 1/2-in. plywood running down the center of the boat's bottom.  The two halfs of that joint will be screwed into a cedar backing board.

Permalink Reply by Greg Jensen on March 23, 2012 at 2:26pm

Guy -  this scarph looks fantastic...

Great job !

Greg

Permalink Reply by Guy Fredrickson on March 24, 2012 at 6:24pm

I got the first side panel epoxied.  There are two 3x8 ft panels and one 3x4 ft panel.  I'll leave it setup for about two days before I start the next one.

 

Permalink Reply by Guy Fredrickson on March 25, 2012 at 9:14am

Well... this morning I inspected my glued scarf joints and the conclusion is "they suck big time".  I am going to cut the joints out and try again.  Luckily I have enough plywood for this.  It seems that close isn't good enough for scarf joints.  I made two major mistakes: 1) the scarf joints were not perfectly square with the edges of the plywood and 2) as a result of the unevenness, the joints overlapped too much in about a third of the length.  Here is a picture of the worst area.  The other joint is marginally acceptable, but it's going too.

 

Permalink Reply by Guy Fredrickson on March 25, 2012 at 1:37pm

I think I'm back on track.  I recut the scarf joints using the router jig.  But what's different this time is that I squared up the joints with some careful sanding using a steel-covered table edge and a marked reference line 2.5 inches from the edge.  This picture shows the steel sheet under the plywood and along the table edge.

 

Here you can see a straight edge along the scarf joint.  Each scarf is now 2.5 inches wide, very straight, and square with the sides of the plywood.

For me, this finishing step produced a much better quality scarf joint.

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