Sorry, another typo..

"Steve" wrote in message
...

Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm.


Should read .... 2"X20"X 1 1/8" cylinder, .......

Steve
s/v Good Intentions

Your power requirement is pretty close to what I got for Rutu. Now you
will find that there are so many alternatives that your brain will start
fogging over.

You have a starting point but the cylinder is going to be pretty big and
heavy and the tiller arm will have to be 18 to 19" long. You have
plenty of room to work with the pressure. With 700 lb. on a 12" throw
you can get by with a much smaller rod diameter. Look for a 1.5" to 2"
cylinder with a 5/8 to 3/4" rod and 12 to 14" of throw. It will be a
lot lighter and you can use a shorter tiller. The displacement will be
less and the pressure will go up about the same so the required HP will
be about the same.

Also, small 12VDC motors develop HP with RPM more than torque and the
lower you gear it the less efficient it gets. Try to stay under 3:1.

For example a 2x12x.625 cylinder will take about 34 cu. in. for a full
throw or about 136 CI/minute for a 15 second hard over. Now say we
choose a 3600 RPM PM motor (Surplus Center #10-1779 would be close but a
little over powered) and start with a belt ratio of 2:1 so the pump is
running 1800 RPM. 136/1800 is .075 so we need a pump with about that
displacement. The Surplus Center #9-5567 is a little small so the belt
ratio would have to be more like 1.8:1

Admitedly that is not an ideal setup but it will be very hard to get the
perfect match with surplus parts. The thing is, when you add up the
cost of all the parts including the mounts, fittings, hoses etc, you
will come out spending $500-600 and many hours of thinking and labor and
still not be quite sure that it will work the way you want. That makes
the $1,200 price of a complete professionally designed unit seem a lot
more attractive. You would have to be a compulsive DIYer like me to
rationalize it. :-)

OTOH, if you go through the exercise of designing one you have a lot
better understanding of how they work and know more about how to select
the correct one for your boat.

Steve wrote:

Sorry, another typo..

"Steve" wrote in message
...

Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm.



Should read .... 2"X20"X 1 1/8" cylinder, .......

Steve
s/v Good Intentions



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Thanks again Glenn.. Makes sense, however (as always), as you can see in
this picture http://hood.hctc.com/~esteve/launch15.jpg
the rudder pintle line extends up and behind the head of the rudder. So this
would require a tiller arm of at least 20" and even that is awkward due to
the rudder angle of 37.5 degrees. The cylinder could be rail mounted and
reach over the tiller head but that wouldn't be very elegant.

Looking at this problem and the picture, I am thinking of a cylinder mount
on the boomkin and a tiller arm lower down and perpendicular to the rudder.

I could resolve this by installing the tiller arm though the stern post into
the lazarette, but I really hate to give up all that storage. And then there
is the engage/disengage problem and sealing up the opening for the tiller
arm

Just about anything that is behind the stern rail would require a method to
remotely engage, disengage from the helm position.

Strange how a serious cruiser would call it a problem while DIYer will see
this as a mental challenge.

The (mental) wheels are turning. I'll start a new topic in
Rec.boats.cruising when I get some ideas.

Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller
design. Haven't actually found anything here that I could get my head
around.

Thanks again.

Steve
s/v Good Intentions

oh,oh,oh, I forgot you have an outboard rudder. 15 seconds is probably
a pretty good rate. That ol' girl should keep her head pretty well with
no help and probably will not want to turn any faster than that anyway.

Don't ask me about the control box. The electronic side of my brain
overheated on that remote control light switch and blew out completely
after figuring out the automatic flush/backwash circuit for the
watermaker. :-)

Steve wrote:

Thanks again Glenn.. Makes sense, however (as always), as you can see in
this picture http://hood.hctc.com/~esteve/launch15.jpg
the rudder pintle line extends up and behind the head of the rudder. So this
would require a tiller arm of at least 20" and even that is awkward due to
the rudder angle of 37.5 degrees. The cylinder could be rail mounted and
reach over the tiller head but that wouldn't be very elegant.

Looking at this problem and the picture, I am thinking of a cylinder mount
on the boomkin and a tiller arm lower down and perpendicular to the rudder.

I could resolve this by installing the tiller arm though the stern post into
the lazarette, but I really hate to give up all that storage. And then there
is the engage/disengage problem and sealing up the opening for the tiller
arm

Just about anything that is behind the stern rail would require a method to
remotely engage, disengage from the helm position.

Strange how a serious cruiser would call it a problem while DIYer will see
this as a mental challenge.

The (mental) wheels are turning. I'll start a new topic in
Rec.boats.cruising when I get some ideas.

Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller
design. Haven't actually found anything here that I could get my head
around.

Thanks again.

Steve
s/v Good Intentions



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I gotta say that this is one of the better discussions I have read on this group
in a long, long time. I am enjoying this immensely. Steve, you have a neat boat,
and I hope you can do some decent traveling in her. Glen, you have a great
head..good to have you around.

Cheers,

Larry DeMers


Glenn Ashmore wrote:

oh,oh,oh, I forgot you have an outboard rudder. 15 seconds is probably
a pretty good rate. That ol' girl should keep her head pretty well with
no help and probably will not want to turn any faster than that anyway.

Don't ask me about the control box. The electronic side of my brain
overheated on that remote control light switch and blew out completely
after figuring out the automatic flush/backwash circuit for the
watermaker. :-)

Steve wrote:

Thanks again Glenn.. Makes sense, however (as always), as you can see in
this picture http://hood.hctc.com/~esteve/launch15.jpg
the rudder pintle line extends up and behind the head of the rudder. So this
would require a tiller arm of at least 20" and even that is awkward due to
the rudder angle of 37.5 degrees. The cylinder could be rail mounted and
reach over the tiller head but that wouldn't be very elegant.

Looking at this problem and the picture, I am thinking of a cylinder mount
on the boomkin and a tiller arm lower down and perpendicular to the rudder.

I could resolve this by installing the tiller arm though the stern post into
the lazarette, but I really hate to give up all that storage. And then there
is the engage/disengage problem and sealing up the opening for the tiller
arm

Just about anything that is behind the stern rail would require a method to
remotely engage, disengage from the helm position.

Strange how a serious cruiser would call it a problem while DIYer will see
this as a mental challenge.

The (mental) wheels are turning. I'll start a new topic in
Rec.boats.cruising when I get some ideas.

Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller
design. Haven't actually found anything here that I could get my head
around.

Thanks again.

Steve
s/v Good Intentions



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com