For a P-19, you may want to use half-inch line.
uhh... but seriously folks, Jim's playful note has prompted me to
scratch head and consider the comparative impact (on the transom
structure) of an accelerating motor in the water versus a bouncing
motor on the transom.
I've been following what I took to be the mailing list's group
consensus that it was foolish to trailer the boat with the motor
mounted on the motor mount--that this could easily generate forces
that were far in excess of what the transom was designed to handle.
I don't recall how we calculate impact, but I would guess that we'd
have to figure in the strength of the prop shear pin ... and the
stiffness of the trailer springs (here in Hawaii, we blow off skip
all pothole-impact adjustments).
Has anyone got a good handle on what the math says about this stuff?
Especially with regards to a skimpy little 3.5 Nissan on a P-14
transom?
> - - - - - - - - - - - - - - - - - - - - - - - - - - -
> West Wight Potter Website at URL
> http://www.lesbois.com/wwpotter/
> - - - - - - - - - - - - - - - - - - - - - - - - - - -
> All this talk about trailing the P-19 with the outboard has me worried.
> I'm not too worried about the weight of the motor lifting the rear wheels
> of the towing vehicle off of the ground because you can still steer and
> brake with the front wheels making contact. What really worries me is if
> you put the whole thing in the water, lower the motor mount and actually
> start it. The numbers don't look good: besides the weight of the motor,
> the moment arm of the motor mount increases the motor gravitational torque
> against the hull by a factor of 2-3 when lowered. The problems are only
> beginning. Suppose you start the motor. 4 hp translates into about 200 lbs
> of thrust which is a 4-5 g force of the motor. Since the driving force
> (propeller) is off center from the motor mount there is additional torque
> (over 200 ft lbs) in vector addition to the gravity induced torque. Now
> you add some chop and the motor is going up and down, so at full throttle
> in chop you can have much greater than 6 g motor forces on the transom.
> Add the entrainment effects of the water on the motor and I'm really
> worried. If the transom tears off the boat, all those pieces of styrofoam
> will come out and it won't float like the brochure. Even worse is if the
> motor propels itself through the transom into the cabin. I'm at a
> crossroads for an effective solution. Should I build a second inner
> bulkhead to act as a transom when the real transom is compromised? Should
> I install a net to catch the motor as it chops its weigh through the boat?
> Would a safety cutoff switch on the motor be more helpful? Would putting
> the boat on the trailer backwards reduce the effect when towing? (I've
> tried sideways a few times, but this has its own problems).
>
> Jim Nolan P-15 #1055, P-19 #426, L138T, LGYC #6
>
>
>
>
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Rich Duffy
P-14 #362
Kula, Hawaii