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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Rick,

You are correct, and more gracefully worded than I!  haha.  the "weight forward" design of a drift boat is purposefully built that way.

 

exciting...makes me want to get out there and design another one or two.....

 

Rick,  Those are all very good points.  And now that I've spent some time thinking about these issues, I can see you point about how the shape of the bottom can be used to compensate for the placement of the load.  What I presently have is basically a symmetric double-ender (with a full-length continuous rocker bottom) that is slightly truncated at one end to accommodate a narrow transom.

But I am learning how one thing affect another.  It's a very interesting design problem.

Dave, I start with the basic shape of the side panel shown in my second screen capture.  This shape has four straight edges and it can be defined by the positions of four points (each "corner" of the shape).  Now imagine standing that piece of plywood up so that the chine edge rests on the floor.  Now you bend the plywood along a curve, keeping the chine edge on the floor.  You do not allow the plywood to flex other than along the bend curve.  The sides of the plywood are otherwise maintained at 90 deg. to the floor.  The plan view of this curve is shown in my third screen capture.  The sheer edge is directly above the chine edge and all you see is a single curve.

The bend curve has a lot to do with the design on the boat.  I chose a Catenary curve to experiment with, but there are infinite possibilities.

Now think of an imaginary x-axis.  This x-axis is parallel to the floor, runs along the centerline of the boat, and touches the forward-most point of the boat (the sheer/stem point).  The y-direction is from side to side and the z-direction is up and down.  Now imagine that this x-axis serves as a rotational axis and you rotate the side panel until the stem closes the gap (all points along the stem have the same y-axis coordinate of zero).  The plan and profile views of the sheer edge and chine edge are shown in my fourth screen capture.

Does this design make a good drift boat?  I'm not sure.

But I do see the importance of the "straight edge" side panel design.  And I do see the importance of thus bending the side panel around a curve and rotating it into position.  This makes a perfectly "developable" side panel and all of the internal side frame members have EXACTLY the same angle relative to the horizontal.  But there is nothing sacred about the Catenary curve and I may experiment with variations of the bend curve.  So yes, I think this basic approach (or a variation of it) is pretty versital.

For example, if you bend curve has a "flat length", then the bottom of the boat will have a "flat length".  It's interesting to see how these design considerations all relate to each other.

I knew nothing about drift boats until I read Fletcher's book.  That is a great book; very well thought out.  I just may make a paper model once I think I've finalized the design.

Guy,

     As for materials, give MacBeath Hardwood a call.  They're in Salt Lake.  I was looking at building a Don Hill boat, I inquired with them about materials.  Though it's not on their web site, they do have marine woods.

There is a MacBeath in San Jose. Great place! All the types of wood you would need at some of the best prices around. What a find!

Thank you for the tip.  I will give them a call!

Here is the latest.  I imported the coordinates of the chine edge and sheer edge calculated by my spreadsheet into Pilot3D and rendered the boat.  This design is based on the Catenary curve approach.  Here are the stats...

1) Elevation from bottom to sheer at oarlocks: 26.5 in.

2) Centerline length: 16 ft 9.5 in.

3) Maximum bottom width: 56 in.

4) Elevation of chine at transom: 7 in.

5) Elevation of chine at stem: 9.5 in.

Here are the results in pictures...

 

 

 

 

 

 

 

 

Please everyone... I'm very interested in your opinions.  Thanks

 

These pictures may look a little odd because the program does not add perspective.  All dimensions far and near are scaled the same in the image.

Good looking boat. 

It's a little hard to be sure but I think that shape is going to rock forward on the continuous rocker because of center of gravity of the materials. If it rocks forward it could make your transom rake a little too shallow and your stem rake a little too steep for the high side boat you are building. 

Stem is a little more important than transom.  If you are going to do the high side then I'm assuming you will be in big waves.  When in big waves you want the stem angle to be more straight up and down so it doesn't dive into the bottom of a hole.  It looks good as is but if you take the entire shape and rotate it toward the stem to approximate the center of gravity shift I'm guessing your transom and stem elevations at the chine would swap.

It's also common to move the center of the widest beam of the bottom toward the stem about six to twelve inches.  When you look at the bottom you can see that the boat has more displacement on the transom end of the boat than on the stem end of the boat.

I prefer a balanced boat to have an equal amount of displacement end to end.  I prefer a forward-balanced boat to have the center of the bottom displacement right at the rowers feet.

Interesting.  Looks nice.  Build a scale model and set it on a flat surface.  I wonder where the natural low spot will be.  Forward of middle, dead on middle or slightly back?   You've gone for what looks like holding the same flare as shown in the second last picture. The boat appears exactly symmetrical from a half breadth or top view except for the section cut short for a transom.  How about leaving it a true double ender?  I think that is a sexy look for a big boat.  Transoms are overrated! haha.

What you may want to do next is refine your measurements based on the materials "standard sizes".  What I mean is, will you be able to get both side panels out of a single scarfed 4'x18' panel?  If not, you might be buying twice as much wood.  On the biggest boats, you have no choice.  But you are awfully close to that 16 foot mark where a few adjustments here or there would allow a more efficient use of the wood. If you look at that standard DET 16x48 in Rogers book, there is no waste whatsoever in extracting both side panels from a single 4'x16' scarfed panel. 

When I designed the Flyfisher Skiff, like I said before, we went through three or so iterations and refined all the materials, tweaking ever so slightly the lines so we didn't have much waste left over when making cuts. It all worked out nicely. And cheaply.

love the stern view. my preferences, which may or may not make for a good boat are generally (can i say 'generally' when I've only built one boat?):

1. a little more flair out on the side panels keeping the 56" beam on the bottom. This creates a little more storage room in your side sections, lowers the center gunwhale slightly, bringing the oars closer to the water and making it a little easier to get in a high side boat.

2. more rake on the transom (shallower angle). This gives a little more room for mounting a swivel seat on the rear deck, allows more room for the anchor to hang without banging the transom and just plain looks cool. mine is very shallow to the point of having to add little side panel pieces to the upper corners, but you can't even tell.

3. as for efficient use of 4x8 panelling, I'm sure everyone will tell you not to do what I did and they are most probably right, but for the bottom, I joined two 4x8 sheets and ran them down the middle, leaving a narrow strip along the sides about 3 feet long. Since there is ample attachment opportunity with 3 bulkheads and the side panel, it made for a solid contruction there in any case. By the way, I wasn't confident in being to get good scarf joints, so I have butt joints, not terribly aesthetically pleasing, but plenty strong. the butt joint in the side panels has a lot of screws which are fairly ugly (I could not get depth enough to hide with wood putty and I wanted clear epoxy/polyurethane finish on the outside), so I used epoxy with pigments to "paint" a steelhead trout over this section. If I had anything to do over again it would be to go slower on the panel joints. 

 

 

Guy are you confused yet? Breaking a new path can be a challenge, however using an already trodden path can make the trip a wee bit easier also perhaps less expensive in time and materials.

Something to consider is that many of the drift boat side panels you see on these pages were built from a  single, scarfed piece of plywood 48" wide. A diagonal line bisected the length of the stock often with a width of 22" at one end and 28" at the other. This allows two identical panels to be formed. As Randy stated the traditional McKenzie boats conformed to similar numbers resulting in the characteristics he outlined. Changing the dimensions to 23 or 23.5" and 25 or 24.5" drops the bow height down and makes the boat less susceptible to wind. This also keeps you wood costs down and the need for full length scarfs to obtain additional width.

I like the work you have done and appreciate that you sent me the spread sheets I haven't yet experimented with them to see their ease of use. I would love to plug in the 22"/26" cuts to see how things work out.

Keep us informed!

Rick Newman

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