Flatbottom Dory: Speed, seaworthy?
 

(Backyard Renegade) wrote in message . com...
"Lloyd Sumpter" wrote in message ...
Hi,
I want to design and build a "riverboat" for the Fraser River, with some
... "unique" design considerations (eg I want it to look ugly because it
will be on a "questionable" dock and I don't want it stolen!). Basically
I'm looking for something between an east-coast fishing dory and Bogie's
"African Queen". Something like Bateau Boat's FL14, but 16 ft, inboard and
probably not Stitch'n'glue.

Anyway, I need some anecdotal feedback: First, a 16ft boat has a
theoretical hull speed of about 5.5 knots. HOWEVER, I've seen many boats
(such as my 12ft alum) that exceeds hull speed without truly planing
(semi-plane?) Does anyone have some performance numbers for 14-16ft
flat-bottomed skiff as to how fast they go before planing? I'm looking at
maybe 6-10hp engine.

Second, I'm unfamiliar with how a flat-bottom hull performs in waves -
are they seaworthy?

Thanks for any comments, stories, etc!

Lloyd Sumpter



Hello:

Three comments.

First, had a 15' sprit rigged sailing dory. I enjoyed it for 15 years.
Are flat bottomed dories seaworthy? The only reason traditional (bank)
dories look the way they do is so they could be stacked (nested) on
each other on fishing scooners. Small deack load if stacked like
pancakes. Reseve boyance and weight carring ability were also needed.
Seaworthness depends on you. Had mine in small craft warnings on SF
Bay CA and 4 miles off Newport, OR in 18' rollers.

Second, find one of several books by Chapell for turn of the century
workboats.

Third, the St. P. dory is a double ended flat bottom displacment hull
not designed for planning. You might try a Calkins Bar Tender. The
USCG liked them enough to use them for life boat service on the NW
coast.

Last, if you want speed, flat botom, and reasonable ability to break
trough surf try any version of the "pacific city" or "Oregon" dories.
They were known as the mosquito fleet along Oregon - North CA salmon
fishery during the 1970s. They usually were 18'-24'LOA. The Smitsonian
"Watercraft" library would also be a great place for "free" lines.

I still see a few sitting on rusted trailors covered by black berries.

If you are in AK talk to any AK sea grant or ADF&G marine agent or
look at the library under ....guess what.... dory.


Chris











OK, a ten horse might get the 14-16 on plane but with effort and light
loads. You probably should look at a 15.
My 12 foot skiff noted earlier in the post planes at about 12 mph with
a load of me and another 300 lbs or so.
A pointy skiff blends in well, holds a tremendous amount of weight,
are very stable for fishing and such, a 14 footer will hold two to
three kids on one gunnel and still not near flip over, they can be run
all day long at a strong hull speed with a 5 horse or even a three on
a lake, a 14 will still row nicely with properly sized oars, beach
nicely...
A pointy skiff of typical design with flat sides and bottom will plane
off easily and can be a lot of fun but for practical use, you will not
spend to much time on plane. At high speeds you will get somewhat if
not all the way airborne which is waaaaaaay cool, but these boats do
not "fly" well and a slight yaw and roll means you catch a sharp edge
in a wave and abrubtly turn or in extreme cases roll (which btw is not
as bad as it sounds if you are prepared for it and just out playing in
the waves;)), at plane you can have a condition called "chine walk"
which can lead to rollover, flat sided pointy skiffs are very wet
boats and if you or your fishing partner are sensitive to being wet
all day, do not build one, even in a slight breeze at hull speed you
get spray in most typical instances. Flat bottom skiffs slap, even at
slow speeds (typical with little rocker) and on plane this slapping
means catching edges and putting up spray. Flat sided pointy skiffs
don't usually have a lot of bearing up front so they tend to dive into
or through waves, taking a lot of water... especially when you don't
expect it like the 9yo decides to go up front abruptly for chips and
the dog decides to join her at about 8 mph... nice wooden swimming
pool in the middle of the lake!
Ok, sounds like I hate these boats, on the contrary, I have made my
business on them. I just like to see that folks who get them, know
what they are getting in to. Did I say, these are wet boats, period!
That being said, here is what I would do if I were you and still want
a pointy skiff:
Go with the 14 footer. Make it 6.5 to 7 feet wide in the center and 6
inches narrower in the transom. Cut a couple of pieces of 1/4 inch
plywood and lay them lengthwise, tack em' down. On one end draw a
point 20 inches up and put a nail in with 1/2 inch left visible. Go to
the other end, come in two feet (for a 14 footer) and put a nail 28
inches up in a similar fashion. Connect the two nails and lay a line.
Cut out your side panels and butt joint them together, cut back wider
ends (bow) 30 degrees and the stern say, 10-15 degrees. Take a four
foot 4x4 and knock off two chunks at 30 degrees and make a stem.
Sharpen the stem and drive it into the ground at a 30 degree angle,
where you will build your hull and attach your side panels to it. Make
a 24 inch high transom or 2x4's and 3/4 inch plywood and attach two
stakes to it temporarily so you can drive it into the ground, 14 feet
from your stem! A ten degree rake from bottom to top of transom
should do for 10 degrees sides at the transom. Make a quick jig of
scrap to wrap the sides around see:
http://rbbpix.com/images/stanley_sie_03_450.jpg
If you wish your chine logs (1x4, where sides will meet bottom) to be
inside of the hull, make notches in your jig to accept the 1x4's, make
the notches oversize and use wedges later to make up for the spaces.
Using whatever means possible, wrap the side panels around the jig and
attach to the transom, now it starts to look like a boat! Apply your
chine logs, inside or outside, yes outside, looks funny like you
wanted ;) and it is actually much easier then trying to size and force
inside gunnels without long ends to hold on to and remove later as in
outer chine logs. Many Bolger boats have the "logs" on the outside of
the hull, anyway, attach your chine logs.
Well, seems simple don't it and it just begun. Anyway, stay tuned as
tonight I will try to get to the bottom, seating, flotation,
motormount etc. For now, it is beautiful out there today and I got an
itch...
Scotty

Flatbottom Dory: Speed, seaworthy?
 

"Lloyd Sumpter" wrote in message

Ok, where were we? Oh yeah, the bottom. Lay your bottom panels across
the boat and mark the edges on the hull, mark the bottom pieces for
cutting. leave at least 1/4" inch extra to be removed later. This
helps nails go in without splitting out the edges and just makes
things easier. Now fasten 4x4's across the chine logs, flush with the
bottom, and where they will be the seams for the bottom panels. So,
there should be a crossmember at 4 feet from the transom, 8 feet, 12,
I think you get it now. fasten and glue the bottom panels to the stem,
transom, chinelogs, crossmembers. Note, it is a good idea to cut some
small notches in what will be the bottom of the crossmembers so as to
allow water to flow fore and aft. I usually put a strip or two of 4"
fiberglass tape bedded in resin on the outside seams of the boat,
mostly to protect the edges of the plywood, in this build, this step
is not structural so it is a matter of choice. Put on a skeg or two
and then flip her upright. Fasten some chunks of 2x2 to the sides, ten
inches up from the floor and attach some seats. You should take a
chunk of 2x6 from seat to floor in the center to support the width of
the seat top. Double up the plywood on the inside of the bottom with a
3x8x3/4" plate for the seat support to sit on. Next put in a breast
hook and quarter knees. Rabbit the front and back of the seats to
accept a 1/4" plywood to cover the foam which you should stuff under
the seats. Fasten on the gunnels 1x4 or 2x6 for more strength. 2x6's
can be bent in a few days by simply laying them over a big rock and
putting weight on either end... It wont take much, a cinder block or
two in each end will do the trick. Put on the hardware, paint, and
float.

Ok, we got a boat simple right? Uh, no you say? You don't understand
parts or I am not complete enough? That's ok.. Get the book "Instant
Boats" from Dynamite Payson at instantboats.com for about 20 bucks and
this will all make sense in a matter of a couple of hours of reading.
Note, Payson is a client of mine in another business. Anyway, happy
building and as always, I can be contacted directly at my website if
you have any specific questions.
Later guys, getting started about 6 weeks early this year, I will
hopefully have some nice pic's of the coming projects.
Scotty from SmallBoats.com