Re: [bolger] Dovekie hull vibration (resonance?)
On Wed, 11 Jul 2001kayaker37@...wrote:
any circumstances. Personally, I've used leather, but rubber would
probably be better (the leather was easy to get).
It's nothing to do with flat-bottom boats--none of my (3) flat-bottomed
boats that I've powered with small and vibrating outboards have done this
(at least not to the degree of mentioning it).
> Is vibration like this bad for the boat? Does anyone know how I canIsolating the motor vibration with a rubber pad is not a bad idea under
> reduce or eliminate it? Would it help to put some sort of rubber sheet
> under the motor clamps. Or is this common with flat bottom boats. I'll
> have to name the boat Buzz at this rate.
any circumstances. Personally, I've used leather, but rubber would
probably be better (the leather was easy to get).
It's nothing to do with flat-bottom boats--none of my (3) flat-bottomed
boats that I've powered with small and vibrating outboards have done this
(at least not to the degree of mentioning it).
I just had two weeks vacation and got a chance to take out the
new/used Dovekie. It has a Mercury 4hp two stroke motor on a four
year old factory mount.
The factory motor mount consists of a fiberglass shell which is
molded to fit over the coaming/gunwale area, and is then formed into
a vertical flat piece of fiberglass with a piece of wood (1.5 x 7 x
14 or so) screwed to the back. The wood is further attatched to the
hull with a small clamp.
Some notes. I have to start out motor speed very slowly or the
prop "slips" in the water. If it is very calm water I can get it
going at a good clip. However, there is a nasty vibration induced in
the hull from the motor in the middle of its throttle setting. The
vibration is there throughout the motors throttle setting, but I
think the hull is resonating in midrange. This is the first boat I've
had with a motor, so I don't know if I need a different size prop, or
a different pitch?
I emailed someone else I know with a Dovekie who has a 2hp two stroke
on a homemade mount and he says his does the same thing. He has a
friend with a Honda 2 hp 4 stroke which also vibrates ( I don't know
what kind of mount though).
My motor mount had a slight crack in it when I started, which I
noticed grew at the end of the two weeks. I don't think the crack in
the mount is causing the vibration, as the other two Dovekies vibrate
also.
Is vibration like this bad for the boat? Does anyone know how I can
reduce or eliminate it? Would it help to put some sort of rubber
sheet under the motor clamps. Or is this common with flat bottom
boats. I'll have to name the boat Buzz at this rate.
Thanks,
Paul
new/used Dovekie. It has a Mercury 4hp two stroke motor on a four
year old factory mount.
The factory motor mount consists of a fiberglass shell which is
molded to fit over the coaming/gunwale area, and is then formed into
a vertical flat piece of fiberglass with a piece of wood (1.5 x 7 x
14 or so) screwed to the back. The wood is further attatched to the
hull with a small clamp.
Some notes. I have to start out motor speed very slowly or the
prop "slips" in the water. If it is very calm water I can get it
going at a good clip. However, there is a nasty vibration induced in
the hull from the motor in the middle of its throttle setting. The
vibration is there throughout the motors throttle setting, but I
think the hull is resonating in midrange. This is the first boat I've
had with a motor, so I don't know if I need a different size prop, or
a different pitch?
I emailed someone else I know with a Dovekie who has a 2hp two stroke
on a homemade mount and he says his does the same thing. He has a
friend with a Honda 2 hp 4 stroke which also vibrates ( I don't know
what kind of mount though).
My motor mount had a slight crack in it when I started, which I
noticed grew at the end of the two weeks. I don't think the crack in
the mount is causing the vibration, as the other two Dovekies vibrate
also.
Is vibration like this bad for the boat? Does anyone know how I can
reduce or eliminate it? Would it help to put some sort of rubber
sheet under the motor clamps. Or is this common with flat bottom
boats. I'll have to name the boat Buzz at this rate.
Thanks,
Paul