- About Flapdoodle
- The plans are in HTML format in two files: The Flapdoodle 2 and Flapdoodle 3. FD2 has metal hinges with wooden fixtures and fasteners, FD3 has stitched hinging and a clever metal transom lock, but is eaiser to build and has the rigidity approaching that of an aluminum boat.
- You will download a zipped file. Unzip it and you will find two folders - one for FD2 and one for FD3. Open either of these folders and scroll down to the <index.htm> file and double click it. This will open the plans in a browser.
New... a high quality DIY
folding sail dinghy. What's more, you can build it your
way. Bill Weller has produced plans in easy to navigate
HTML format that give step-by-step instructions plus customizing
options along the way. There are over twenty pages of
instructions and dozens of photographs and diagrams to
help even a novice builder.
Mr Weller started this project about six years ago and
and finally has plans ready to sell. The availability
of PVC laminated cloth was key to making it work. The
name Flapdoodle Dinghy was given to it by his 80 year
The dinghy is mostly composed of hardwood plywood, but
has some hardwood pieces. It folds down flat about the
size of a surfboard and the main body can be carried under
one arm. Open, it becomes a rigid 7'10" x 4 foot
beam dinghy of classic proportions. It could be built
for about $300; much less if desired by using the construction
of the Flapdoodle Design
The classic dinghy shape dates back to the 1800's as
a tried and proven design and is responsible for the Flapdoodle's
ability to glide through the water with hardly a ripple,
even when heavily loaded.
First, the curves of the panels not only define this
shape, but give it the necessary rigidity.
Secondly, shear forces were employed where possible instead
of putting the materials in compression, or tension.
Forces in Shear
The PVC cloth used to make the waterproof panel hinges
is laminated to Dacron. When it is glued to the hull panels
and the covers glued on, #4 x 3/8" screws hold everything
firmly. When the boat is loaded, shear force (mostly)
tries to pull the cloth laminates sideways, out from under
the layers of glue and wood. It takes considerable force
to do this.
The entire dinghy design is a result of natural curves.
The red curve below defines the keel, and the black curve
makes the gracefull hull shape. Both curves are designed
to follow the natural bend of the wood just as classic
dinghy did a century ago; a tried and proven shape.
As a result of this, any two of the spreading components
below will produce the final shape:
(not to scale)
There is no need for hinges to force the seat or transom
to open the boat. During assembly the center seat will
spread the sides with only moderate force by you. The
transom and bow plate drop into place smoothly.
Surprisingly, trying to spread the sides further will
force the ends together. Included as side forces are the
mast and daggerboard.
A load on the bottom of the boat (including the seat
which is supported via a pedestal to the keel) forces
the sides in this direction:
The transom tries to move in the directions indicated
below. In addition, a trolling motor or small outboard
causes considerable force (right).
It was a challenge to find a way to handle these forces
and keep the weight and complexity of design within reason,
but locking T slots provided a solution. As a result,
the transom slides smoothly into place during assembly.
The peculiar inner curve of the stern lock post was dictated
by accessibility to the large brass screws (red) that
attach it to the keel and skeg (not shown). More screws
are used on the bottom. The transom has a "T"
slot that slips onto a mating "T" on the post.At
the top is a similar T that mates with the rear seat,
locking the entire stern into a rigid unit.
The foredeck uses a similar locking arrangement.
FAQs - Answers by
Q: Obviously, there is a waterproof fabric at
the joints. Is it exposed on the bottom where it could
become damaged in beaching the boat or is it somewhat
protected by what appears to be a centerline keel plan?
A: Obviously, metal would be the best
choice for "beach scooching" as my family calls
it, since it is a highly abrasive operation.. I kept this
in mind when I designed the Flapdoodle. The waterproof
part of the seam is under a layer of Dacron laminated
to it with Acrylic latex caulk and I recommend a finish
coat of varnish. The seam for the most part resides in
a groove for protection. You will laugh at this one....
I roll my own cigarettes and the rolling machine material
does not last very long. I made a replacement out of scrap
fabric from the Flapdoodle. After several months, it shows
no wear even under high magnification, and is still flexible..
Outlasted 3 or 4 rolling machines and looks like it did
at the beginning.
Q: Would luan plywood work (the kind you can
get at Home Depot or Lowe's) for construction or would
one need to use marine plywood?
A: I was half through the second Flapdoodle
design when I found a sheet of luan at Home Depot that
is the best piece of plywood I have ever found of any
species. I keep looking to see if they got more. Another
sheet later from HD sucked so bad it was not usable for
anything structural, yet had a sticker from the same manufacturer.
The veneer was about 1/3 the thickness of the good sheet.
Look for a thick layer of the final outside veneer with
the least fancy grain. IE, plain looking. Also, the good
sheet tested 20% lighter! I vowed it would be the material
of choice for the Flapdoodle III if my health will allow
a third version.
Q: Assuming that I opted to leave out the daggerboard
trunk, what would the Flapdoole weigh?
A: It is not possible to give a weight
(plywood varies + or - 20% regardless of strength), but
I can carry the folded part under one arm with all the
options such as daggerboard box, but figure about 45#
for the folded part.
Q: In your opinion, could it be assembled and
launched from the cockpit of a sailboat?
A: I have no idea yet, but it is easy
to assemble (more so than the Seahopper type). My guess
would be if you can launch any other type of dinghy, you
can launch a Flapdoodle. Incidentally, the Flapdoodle
assembles without any tools.
Q: Can a leeboard be rigged instead in order
to save weight?
A: Leaving the DB box out will save
a lot in weight and ease of building. I plan to add a
leeboard design later to the plans. But since this is
a real dinghy when assembled, there is no reason any dinghy
style leeboard would not work. There is an excellent essay
by Jim Michalak here.
Other weight saving suggestion are given as you go through
Q: What is the folded length of the boat? Is
it still 7' 11" or is it longer?
A: The Flapdoodle is longer when closed...
about 8' 3". This is due to the geometry changes
between the open and closed positions. If you lower the
height of the foredeck and stem (not the height of the
boat) the overall closed length is reduced. Since much
of the fore part is out of the water in use, you could
start building the FD and when you get to the section
where the front plate is installed, cut off say, 6".
The bowplate would have to be wider of course, and so
would the PVC front panel. Again, I had thought of all
this during design, but keep in mind where the mast step,
etc. would be if you did this. Also, the skeg could be
shortened if you do not intend a rudder.
Q: Can I add to the length of the Flapdoodle
by splicing two feet (or more) onto a eight foot panel
cut from a 4 x 8 sheet of plywood?
A: I do not know for sure, but I have
serious doubts. I fear it would make hinging the panels
a nightmare. The geometry of the Flapdoodle was painstakingly
worked out. Changing the length at random would most certainly
change everything else, including strength of the dinghy.
For more information, visit the Flapdoodle website