Hello Gardner, glad to hear you are still
working on the plan.
I don't think there is a good answer to
this, only opinions. Glad you asked; here's mine:
Other than overturning, the thing that scares me
most is hitting submerged junk. But overturning is something at least partly in
my control since I can always change the way I'm sailing. Hitting something is
pure fate. Like all multihullers I've seen big nasty things slide
between the hulls of my boat and also felt them slide along the hull.
I've even hit a few small trees and misc. flotsam some good licks. I
haven't hit a big log at sailing speed, but enough people have to make it
worth some thought.
Part of it can be analyzed and always
is: ....the weight of a big log, the speed of the boat, angles, and
the boat skin's resistance to penetration. So we can at least do that
much.
After that it's simple for me. If I have
any chance to try to push a log aside I'll take that chance
everytime in preference to the damage from riding up and over that log. I
want to minimize damage to the daggerboard, the daggerboard
case (ugh!!), rudder, and even the motor as the stern settles back down. All of
those except the motor are a time consuming and immediately
necessary repair. A couple of feet of crushed sacrificial bow can
be done at my convenience. Or not....
But I'm afraid it mostly comes down
to opinion and bias.
If I had a centerboard and cassette rudder I
might feel differently. But I don't.
Roger L.
F28cc
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----- Original Message -----From: Gardner PomperSent: Tuesday, April 23, 2013 5:34 AMSubject: Re: [harryproa] Logs under bowRoger,I have been having the same discussion with Rob on my design. We keep going back and forth and I still don't understand. I am with Doug on the idea that a sloped bow would tend to ride up on top of a log and avoid any structural damage. Why is it preferable to crush part of the bow and have to haul the boat out and rebuild it? Is there some disadvantage to angling the bow back a foot or so? the harrys have such a small draft and fine bow that you would lose practically no buoyancy.- GardnerOn Tue, Apr 23, 2013 at 6:24 AM, Roger L <rogerlov@ix.netcom.com> wrote:
"And on another matter, I was reading in Cruising Helmsman magazine about looking out for floating submerged logs around PNG/Indo.
This would be a worry on harrys. Perhaps an extra foot of bow that angles up to take the hit and ride up over the top of the log?"In the PNW (USA) and in the big channels and rivers everywhere it seems that submerged logs are a problem. You hear of boats hitting logs squarely, riding over, and losing daggerboard or rudder or prop or everything.So is an angled bow an advantage or maybe not? And how much of that depends on the angle of the log?I've hit a few logs myself and most of the time the boat moves over a little and the log also moves over and what you have is just a sudden stop and big scrapes down the sides of the hull. The sudden stop can be worse than the scrapes. The only time I had any damage other than scrapes was when I hit a log almost squarely while motoring in my small tri and it took off the prop and bent the shaft as we rode over.My own preference is for a straight bow with the forward foot or two being made to crush and easily replaced. That puts the actual structural hull a foot or two behind the crush bow.Obviously there's an advantage if pieces protruding beneath the hull are able to pivot. If that can't happen, I'd prefer things to break away cleanly in a manner of my choosing. Makes repairs easier.Roger L.....................
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