[Alberg30] 2 blade prop

[Michael]

>All that being said, my partner is getting itchy to put the two-blade
>back on because he's concerned the prop is slowing us down when racing.

I find myself focusing on the things I know compromise speed when racing-It
affects tactical decisions I make, whether actual speed difference is real
or imagined; actually I start thinking of albatrosses and Ancient Mariners
:-).

Even when cruising, I think  in terms of where I would be if I hadn't lost
speed/time back on that sand bar, for example-or, Gee, I'd still have fair
tide if I had rigged that preventer earlier. Having a sailboat optimized for
sailing helps my mental health. I think.

Michael
#220

----- Original Message -----
From: Kevin Blanc <t.k.blanc at att.net>
To: Alberg 30 public list <public-list at alberg30.org>
Sent: Friday, April 11, 2003 8:24 PM
Subject: Re: [Alberg30] 2 blade prop


> We're using the 3x10x7.4 prop sold by Indigo Electronics
> (www.atomic4.com). It's (advertised as being) designed specifically for
> the A4 engine. Since all that Indigo does is A4 stuff, I don't  think
> that's hype. It's an oddly shaped prop with little winglets on it that
> are meant to cut down on cavitation.
>
> It's much better backing. It backs straighter, steers a little better,
> and starts moving backwards sooner.
>
> It vibrates less.
>
> It provides a slightly lower idle speed and, I think,a higher high
> speed. That's a seat of the pants thing, though, I can't prove it.
>
> Boat speed recovers faster after banging into chop. This is a seat of
> the pants thing that I'm sure about.
>
> The engine runs at a higher RPM, but more quietly (less "boom"). Some
> folks contend that that's worse for an older engine, but I don't see
> how. There's less pressure on everything inside the engine if it's
> running faster per knot of forward motion. Of course, I wouldn't spin
> much faster than 2500 even if I could. It cruises at about 2K or 2.1K. I
> would imagine that the increased water flow and charging current are
> bonuses, too, but again, I can't measure that.
>
> All that being said, my partner is getting itchy to put the two-blade
> back on because he's concerned the prop is slowing us down when racing.
> Of course, he's right. How much, I'm not sure, but it does have slightly
> more surface area (less than 10 percent more, I think) than the original
> Columbia 13x7, and you can't tuck it behind the deadwood. Once we get
> better at racing (there's so many other things to improve at), I'm sure
> it'll come off.
>
> If you sail no matter the wind speed, think twice. If, however, you find
> yourself motoring a lot and sailing when the wind is reasonable, you
> might like it.
>
>
> Mary & Bill Mahony wrote:
>
> >Kevin--Curious, because I'm pondering this myself.  When you say
noticeably
> >better, could you elaborate?  I've read the 3-blade makes a difference
> >particularly in regards to backing--do you find this to be the case?
> >
> >Thanks for your time,
> >
> >Bill
> >#276 "Mary Ann"
> >
> >
> >----- Original Message -----
> >From: "Kevin Blanc" <t.k.blanc at att.net>
> >To: "Alberg 30 public list" <public-list at alberg30.org>
> >Sent: Thursday, April 10, 2003 5:14 PM
> >Subject: Re: [Alberg30] 2 blade prop
> >
> >
> >>George, in my opinion, it's better with a three-blade. Not a panacea,
> >>but noticeably better.
> >>
> >>George Dinwiddie wrote:
> >>
> >>>Yves,
> >>>
> >>>I would keep the old 2 blade.  In fact, I've done so.  The fact is,
> >>>when in reverse you've effectively got a large fixed rudder and a
> >>>small moveable keel, because the waterflow is reversed.  No prop is
> >>>going to change that.  Instead, you should learn how to use what
> >>>you've got.
> >>>
> >>>To make the boat turn well, you need water flowing past the rudder,
> >>>and that means the boat has to be moving.  Going forward, you can
> >>>motor slowly and the prop will add to the water flow.  In reverse, you
> >>>need to be moving faster, so give it a good jolt of gas.
> >>>
> >>>Then, you don't want to be going too fast, so shift to neutral and let
> >>>the boat's momentum carry you.  In fact, I like to give a smaller
> >>>burst of forward, but not enough to slow the boat down.  It seems to
> >>>help the waterflow across the rudder.
> >>>
> >>>It works, but because of the prop walk, you'll find the boat wants to
> >>>turn in one direction (bow to starboard, stern to port).  Use that,
> >>>and choose to turn that way, even if you have to turn further.
> >>>
> >>> - George
> >>>
> >>>Yves Parenteau wrote:
> >>>
> >>>>I'm a first time boat owner and just wondering if I should replace the
> >>>>
> >2
> >
> >>>>blade prop for a 3 blade right away before the boat hits the water.
> >>>>It's a
> >>>>$600 dollars expense I could do without right now. any comments
> >>>>please( I
> >>>>concern about reverse capabilities )
> >>>>
> >>>
> >>
> >> +---------------------------------------------------------------+
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