[Public-list] another outboard discussion
Mike Lehman
sail_505 at hotmail.com
Fri Sep 30 05:12:31 PDT 2005
J
Try for 25 HP
Mike Lehman
~~~_/)_/)~~_/)~~~
----Original Message Follows----
From: "J Bergquist" <JOHN.R.BERGQUIST at saic.com>
Reply-To: j at ship.saic.com,Alberg 30 Public List -- open to all
<public-list at alberg30.org>
To: <dk.campbell at sympatico.ca>, <j at ship.saic.com>,"'Alberg 30 Public List --
open to all'" <public-list at alberg30.org>
Subject: RE: [Public-list] another outboard discussion
Date: Thu, 29 Sep 2005 21:56:20 -0400
Don-
Thanks for your comments. All well taken.
1. Not sure about longevity. You might have a good point there. The
longevity of a brand new 4-stroke outboard vs. a reconditioned Atomic 4
built no later than 1982 would, indeed, be an interesting celebrity death
match. I think I'd bet on the Yamaha, personally. But maybe I'd lose.
However, there's a brisk market in used outboards, and 4 strokes bring a
premium. They're hard to come by, so they must be doing something
right...???
2. Okay if 9.9 hp is insufficient, then a 15 hp model costs only $500 more
and still over $1000 less than a rebuilt A4. And - can you believe this -
weighs the SAME as the 9.9! I know at least one owner who has a diesel of 13
hp which he says is sufficient. In big chop, I would hope that I'd be
sailing anyway. I have never understood people's concern with being able to
use the motor in chop. But maybe I am just not experienced enough. Seems to
me it's a sailboat, and if there's chop, there's probably wind. But I
digress from the topic...since an outboard is not hooked up to a 55 or 70
amp alternator or freshwater pump (I would want FW cooling if I got an
inboard), it has more available power to drive the propeller. Of course, the
gearbox losses are probably somewhat higher than a stuffing box and cutless
bearing. But I bet that in the net the outboard produces more available SHP,
in an even comparison. And most people I have spoken to are adamant that the
Atomic 4 never developed 30 HP in an operating Alberg in the first place. If
you look at the power curve for the motor, it develops 25 hp at 3000 RPM.
Depending on the propeller match, most boats are probably using less than
this. The curve is pretty steep as a function of RPM. Note also that the
outboards are available in both standard and high-thrust models, which
basically have different propulsion matching (gearing and propeller). Then
there is the fact that the outboard probably has a much higher propulsive
efficiency (3 blade prop, with only a small stick instead of a full keel in
front of it, and not much in the way of inflow wake), not to mention the
fact that, for racing, you pull the thing out of the water and voila...zero
auxiliary propulsion system drag! In the net, I'd be willing to bet that an
outboard puts FAR more effective power into the water than an inboard of
identical power, on our boats. I don't know if it's 2 to 1, but I'd bet it's
a significant difference.
3. I am not planning to mount the motor on the transom. I thought I was
quite careful to explain I would mount it on the starboard side near where
my existing fuel tank sits. This would put it longitudinally somewhere
between my winch and the aft end of the coaming. I am not sure how you
figure that removing 500# of atomic 4 and adding 100# of outboard about 3
feet further aft is not going to result in a net trim by the bow. I'll let
you work out the arms, trimming moments, and net resultant trim based on the
change in LCG if you want to. And as for roll, I figured I'd add my extra
batteries on the starboard side in such a way that the boat would have a net
zero shift in TCG (and maybe just maybe move LCG far enough back to get the
boat back on her original lines, otherwise I'd have to start figuring how to
take stuff out of the bow). It seems to me that Yves is a pretty smart guy
and he managed to make this kind of system work well. He sure has a lot more
miles of sailing experience than I've got. I don't know. Maybe he sails
around with his bow sticking way up in the air, but somehow I doubt it. By
the way, he claims on his website that his 9.9 hp motor pushes his boat at 6
knots. By my calcs, hull speed at zero heel is 6.25 knots, so that's about
as good as one can expect, I guess. Granted, he's not carrying around 500#
of Atom bomb...maybe that gives him a slightly shorter waterline, and lower
hull speed, but let's not split hairs, eh?
4. Though I am, indeed, a SNAME card carrying naval architect and marine
engineer, unfortunately I don't own a towing tank or a good model of the A30
to figure out the real EHP curve so we could answer our propulsion power
questions with authority. Of course, I could spend some time lofting,
building, and testing one, and I could maybe get a friend who works at the
USNA hydro lab to let me into their teaching tank one night or weekend, but
really I'd rather go sailing. So instead of doing that, I'm asking questions
to this list.
Kind regards,
J Bergquist
Calliope #287
PS. Gail, thanks for the brief on the rules! That would be awesome if I
could still race the boat with this different propulsion system installed!!!
PPS. Anybody have good ideas about how to plug my stern tube? I'd like to
avoid anything too permanent in case somebody else comes along later and
wants to install an inboard... But then again, would also like to avoid
springing a leak!!!
-----Original Message-----
From: dk.campbell at sympatico.ca [mailto:dk.campbell at sympatico.ca]
Sent: Thursday, September 29, 2005 8:08 PM
To: j at ship.saic.com; Alberg 30 Public List -- open to all
Subject: Re: [Public-list] another outboard discussion
I am always amazed at the way modern engineers try to get horsepower or
kilowatts out of small blocks. The way they do it is with fuel injection and
turbochargers - very simple more fuel and or more air. The life of these
smaller
blocks is not what the old long stroke, big bore motors gave us. Be
prepared to
buy several of these over the lifetime of a good inboard.
At the current time, there are a number of unhappy owners of A4s,
primarily
due to either wear on the rings and cylinders from extended usage or poor
maintenance procedures over the 35 or more years that the motor has been in
the
boat. This unhappiness is the result of these motors now not developing the
hoprsepower they were designed to operate at, which was at least over 18,
with a
potential to go over 30. How will a 9.9 HP unit ever provide you with the
safety
you require if your sails won't work against a tide, current or chop? As I
have
said earlier this month, the 9.9 is hard at work to propel an Alberg 22
which
weighs 4000 lbs and the same hull design as ours, only on a much smaller
scale.
Since you are a naval architect and engineer, for a quick test, try
the
Alberg hull in a wave tank and see what the drag coefficient does with this
motor that far out on the transom! I have the feeling that 110 lbs on the
transom will be worse than the 350 lbs under the bridge deck for waterline
balance. The other option is to work the propulsion formulae backwards to
determine the required HP with the hull shape/ displacement and desired
cruising
speed for the AL30 hull.With the slippage or efficiency factor that you
engineers seem to build in at around 50% , the 9.9 should look very small
indeed, in fact harebrained as you say.
Don
#528
J Bergquist wrote:
> Dear List,
>
>
>
> Me again, with the busted atomic 4.
>
>
>
> So I have been kicking around all kinds of harebrained ideas about how to
> propel my boat when there is no wind. Today I went to the marina where I
am
> coming out of the water for the winter (Fairwinds on the Magothy), and I
> discovered that they do a lot of business in outboard motors. I found out
> that I can buy a brand new, four stroke 9.9 hp Yamaha high thrust long
shaft
> motor with electric start for only $2200. It comes with a 2 year
warranty.
> It weighs just over 100 #.
>
>
>
> Now, my other options are as follows:
>
>
>
> 1. Install a rebuilt Atomic 4. My short block is worthless. But my
> alternator and carburetor are good. Head and manifold need replacing. By
my
> calculations, I need about $4000 to get a rebuild A4 from Moyer. Plus a
> bunch of time and effort to install it.
> 2. Install a new diesel. This seems to be a good option, but I'm
> currently estimating at least $8000 after I buy shafting, propeller,
> dripless packing, new fuel system, and a few other while-you're-at-its.
Plus
> even more time and effort spent installing it.
> 3. Install electric propulsion. I love everything about this option
> except the range limitation (severe!), the longevity (electronics and
> water.no no), and the unconventional nature (might be tough to sell to a
new
> owner). Its cost is more difficult to estimate because there is not much
in
> the way of comparables, but it would be at least $5000 and maybe as much
as
> $9000. Depending on how many batteries I buy and what kind of onboard
> charging system investment I make (solar, wind, fuel cell - yikes), it
could
> be a lot more. Then there is the risk.there's nobody out there who has a
> comparable system and can say yes it works or no it doesn't.
>
>
>
> So I know that Yves Gelinas repowered Jean du Sud with an outboard. And
he
> seems to have come up with a nice way of mounting it on an articulating
> bracket on the port side. My existing gas tank is on the starboard side.
I
> am thinking that I could make a real nice bracket and install the
plumbing
> for gasoline from my existing tank right out to the motor and hook it
into
> my existing electrical system (of course, it only has a 10 amp
> alternator.wouldn't charge batteries very fast).
>
>
>
> Even considering the cost differential between this motor and an A4, I
could
> buy some really nice canvas, a second bank of batteries to make up for
the
> additional time I would have to go between charging (boosting my capacity
> from 200 to 400 amp hours), and a super nice shore-power based charging
and
> monitoring system and still have cash left over. Not to mention my boat
> would be a couple of hundred # lighter (would y'all still let me race?)
>
>
>
> Can someone tell me what is silly about this idea? It seems to me a
really
> good option. Allows me to invest more time and money in sailing, rather
than
> in my motor. It is, after all, a sailboat. Sometimes I think I might
forget
> that.
>
>
>
> Your pal,
>
>
>
> J Bergquist
>
> Calliope #287
>
>
>
> PS. Is anybody out there interested in helping me sail my boat up to
> Fairwinds Marina on the Magothy this Saturday? I need crew!
>
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