[Public-List] Reversing the A-30

Sun Apr 3 13:54:01 PDT 2011

As long as you are not doing this with a single cyl. diesel that takes 20
seconds from full power in one direction to full power in the other. I think
the flywheel was half the weight of the engine. Its gone now.
Richard 609 Into The Blue

On Sun, Apr 3, 2011 at 11:41 AM, Gordon Laco <mainstay at csolve.net> wrote:

> Well I guess I asked for it.... Sorry this is so long but it's not easy to
> describe briefly without access to diagrams
>
> When backing up, the key is to only engage the transmission in short
> bursts.
> Remember that the boat will always try to weathercock her head down wind
> and
> make a plan that accommodates this.   If you have to make a turn while
> reversing, don't rely on the rudder to be effective;  instead, use 'burps'
> of power ahead (with lots of rudder) to shove the stern in the direction
> you
> need it to go.  Be aggressive with the throttle and picture a blast or jet
> of water being directed by the rudder when doing this, but not so
> aggressive
> that you stop movement astern.
>
> Where we keep SURPRISE a south wind, luckily rare here, can make getting
> out
> of our slip complicated because the usual backing out and turning involves
> turning the stern away from the wind, the opposite to what the boat wants
> to
> do.  Since I know SURPRISE just won't want to turn her stern away from the
> wind while backing out, I don't ask it of her.  We either turn the 'wrong'
> way until she's done a 180 in reverse ( a complete U), then apply full
> opposite rudder with full throttle to shove her head up so we can turn
> again
> and get out.... Or just back out.   The A30 will quite happily track
> straight in reverse if she's backing upwind.  The natural tendency for the
> bow to fall off helps in this case.   Once can avoid prop walk being a
> problem by keeping the engine in neutral or just idling in reverse with
> burps of reverse power keeping her moving.  If a sharper course adjustment
> is needed, one can put the transmission in forward and give it a hard bash
> instantly followed by going back into neutral before sternway is lost.  At
> the first opportunity, we spin the boat in her length so that we can more
> elegantly leave in forward.
>
> To spin the boat in her length, a useful thing in tight quarters, one can
> use the A30's weight and overhangs to help.  If at rest, get her moving
> astern, but before she gets much way on, put the helm hard over and burp
> sharply in reverse.  She'll stop, stunned, but her head will begin
> swinging.
> Get her moving astern again, but before much speed gets on her, do it
> again.
> The A30, like most traditional vessels, can use the heavy ends' tremendous
> momentum which is developed once she starts a swinging motion.
>
> This is easier if the boat has forward way on, such as for example coming
> up
> to a wharf that has a space between boats made fast alongside.  (in a car
> we'd call it parallel parking)  Say we want to spin to port so as to slide
> into the space, ending up with the bow facing the way back out...  approach
> slowly... Start a turn in as if aiming for the centre of the space with
> full
> rudder then as the bow begins to spin to port put the transmission in
> reverse and burp up to full power for a second.  The boat will stop
> (stunned
> is how I visualize it) but keep swinging to port... Let her start backing
> then give her a burp ahead - remember the helm is still hard over causeing
> the prop wash to shove the bow to port again.  She'll start moving forward
> but before she gets much way on, go into reverse and stun her again.
>  She'll
> swing faster.  Do this a couple or a few times and the boat will be halted
> with regard to way through the water, but will be swinging.  Once she has
> nearly done her 180, give her a little reverse helm and slow ahead...
> She'll
> gently stop swinging and slowly slide forward into the space.
>
> I appreciate this may be unclear when one is not watching it being done...
> But I recommend people try it out in open water on a quiet day.
>
> The reason we can do this better than most fin keeled yachts is because the
> prop wash plays directly upon the rudder.  The cut out and the rudder
> position in our boats is about perfect to direct the prop wash as a jet of
> water shoving the stern forward or aft.  The A30's relatively great weight
> imparts great momentum.... The prop wash will tend to spin the boat before
> it starts it moving ahead or astern.
>
> Back to reversing.... Imagine the boat doing 1.5 or 2 knots astern backing
> down a channel.  The prop walk, the wind or whatever starts her tending off
> course.  You know the rudder won't do anything so you krank the helm over
> to
> full in the direction you want the bow to swing... And burp a lot of power
> just for a second, in forward.  The boat will slow... But so long as you
> judge the amount of power correctly she won't stop, and you'll have shoved
> the stern back into line and you can burp in reverse to keep her moving.
> Obviously one can't do this too many times in a row or she will stop... But
> that's good, because now you can spin her and finish the passage out in
> forward.
>
> In a cross wind, you'd be better off spinning as described above and then
> motoring out normally because nothing will prevent the bow from falling
> away
> from the wind.
>
> Sorry this is so Long and I hope it makes sense.
>
> Gord #426 SURPRISE
>
>
> On 03/04/11 8:18 AM, "Greg Bover" <gregbover at cbfisk.com> wrote:
>
> > <<<<<<I've heard of that sort of thing.  My feeling is that full keeled
> > yachts are
> > 'less maneauvreable' than fin keeled yachts only when they are handled by
> > sailors who aren't used to them.   Any full keeled yacht with a prop in
> an
> > aperture can be made to spin in its own length by use of rudder and
> engine.
> > Fin keeled yachts have made people lazy and forget how to handle their
> > boats.
> > Do I sound like I'm getting on a high horse?  I guess so! Sorry.
> > Gord<<<<<<
> >
> > All right, Gord, I'll admit it. I can't back up Linnet worth a damn. Care
> to
> > expand on your comment with some instruction?
> >
> > Greg
> >
> > Greg Bover
> > Frances Fitch
> > Linnet #114
> > Gloucester
> >
> >
> > Gregory R. Bover
> > VP Operations, Project Manager
> > C. B. Fisk, Inc
> > 978 283 1909
> > www.cbfisk.com
> >
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