T&T: Dinghy lessons learned

[Jeff Barfett]

Larry,

Thanks for the report and the description of your sound engineering on this
project! I look forward to seeing the pictures and your findings after
further sea trials.

Please keep us updated!

Jeff



I have been building this boat from a bare downeast hull for the past 
five years. It has a modest 36" transom height and a nice aft cockpit, 
both prerequisites for this to work hand.  Since  the 
outboard  only turns 45deg I designed and built a motor mount that has 
a vertical travel of 20" and swivels the other 45deg to give me  
perpendicular thrust. The motor is a long shaft (20") and that clears 
the water nicely in the up position while not playing submarine when down. I
had to add a 5" riser to the dinghy transom which does not seem to effect
performance.

I have just completed the boat and am waiting for hurricane season to 
end (mid Nov) to launch so have not tried it yet. The Yamaha is a brute 
and I have no fear it will move the boat around. Just hope my mount which I
designed for 15hp is 
up to the task. It is made of 1 1/2x .185 square stainless tube  and a
number 
of 3/16" plates. The actuator is  a 25inch 5/8 stainless threaded rod that I
drive 
with a cordless drill. Materials for the mount were less than $150 plus
several hours of TIG welding by a friend. Onlinemetals.com has almost every
dimension and shape stainless and will sell by the inch or foot and fair
prices. I use 304 (too cheep to buy 316 ) and cut it easily with an angle
grinder and inexpensive 4 1/2" disks just for stainless by Rexcut. They also
offer 7" disks which I use on an old Sears radial arm saw. Cuts like butter.
With a little patience and some grinding you can even do rounded shapes. I
passivate the stainless with citric acid available inexpensively in bath and
jell. The 304 will still bleed a bit of rust in the salt environment which
can removed periodically with a reapplication of the gell.

The starboard davit is almost directly over the motor mount so it is a
simple matter to sling the motor from the dinghy to the mount using the
dinghy winch.  

My wife and I have cruised before and she is quite handy. I plan to 
post her by the idling and lowered motor and then give her a number via
radio
corresponding to the direction of thrust I desire and a percentage of 
throttle. I.m sure it will get the stern off of a lee dock fairly handily.
Hopefully with about 45deg reverse to starboard on the outboard and a little
forward on the main it might just move the boat sideways in calm conditions
such as lock walls. That would be nice.

The downeast hull moves very easily (hull speed on 45 diesel hp) so I am
hoping for 3-4k at 70%  with the outboard. 

I will post again and put up some pictures if the scheme works when I get it
in the water.


Larry Ropka
42'Homebuilt pilothouse
Ft Walton Bch Fl
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