Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 10-08-2016, 04:33   #31
Registered User

Join Date: Feb 2016
Location: Great Lakes
Boat: Mid size sloop rigged
Posts: 182
Re: Max Draft?

I'm not saying don't leave a margin of safety, you still leave a margin of safety.

But if your margin of safety is 6 inches and your draft reading is out by 3" then you are blindly reducing your margin of safety by 3".

I am comfortable with 4" over a cill, in a lock I am very familiar with, say a lock I use 20 times a year. I just go real slow.
__________________

__________________
Ungvar is offline   Reply With Quote
Old 10-08-2016, 05:05   #32
Registered User
 
Group9's Avatar

Join Date: Sep 2010
Posts: 1,579
Images: 7
Re: Max Draft???

Quote:
Originally Posted by edsailing View Post
I don't understand what your concern is. Inches don't normally matter as prudent sailors will keep a reasonable depth under the keel. Weather conditions can cause big differences in depth of the sea. Relax and enjoy your new boat!
Maybe in place with rocks all over the bottom. We have mud and sand where I live, and I have skidded my sailboat on the bottom countless times to get to a place I really wanted to go.
__________________

__________________
Cruising again!
Group9 is offline   Reply With Quote
Old 10-08-2016, 05:14   #33
Registered User

Join Date: Feb 2016
Location: Great Lakes
Boat: Mid size sloop rigged
Posts: 182
Re: Max Draft?

Quote:
Originally Posted by El Pinguino View Post
Oh dear....

Thinking that you can safely navigate anywhere ( lock sills included ) to a depth tolerance measured in inches is akin to giving position reports to the third decimal of a minute of arc......
2" of error on a 5' draft is a 3.3% margin of error. In terms of a circle, that is equivalent to 12 degrees. When you are plotting a course, are you cool with a 12 degree margin of error in your course? At any given time you may be off course by 20 degrees, just like when you are in the bottom of a trough your draft might be 6 feet deeper then when you are on a crest. If you know what your course should be, to within the degree you can correct, if you're okay with a 12 degree error in plotting a course, in a static environment, you certainly would not be welcome to navigate my boat.

The kind of inaccuracy your talking about could mean departing New York for Morocco and hitting Northern Spain. You might be okay with that,
but I sail in thin water, all the time and thousands of other people do too. I know my draft to within a couple of inches, and armed with that knowledge, I can make informed decisions. If I chose to be ignorant of my actual draft (at the time I leave dock, not at any given moment in time), I would be aground a lot more than I am or alternatively, I'd be to frightened to ever leave the dock.

If the OP asked the question, then there might be a very real reason they are concerned about their actual draft, which can only be determined as other posters have said, with a measuring tape. They might be playing in very marginal water, some of us do that you know? I get it, you and Jim don't, you play offshore in blue water, but not every body does.
__________________
Ungvar is offline   Reply With Quote
Old 10-08-2016, 06:28   #34
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 16,529
Re: Max Draft?

I don't really know exactly what my draft is, yet I am pretty sure exactly how much water is under my keel.
I'm not real smart and don't like doing math, so what I did was very slowly ran my boat aground in a very gently sloping area of the bay in calm water, then set my depth finder to read zero, Now I know when I see 1 ft, I have 1 ft under the keel.
For me, thats good enough, cause I have not yet been somewhere where the exact depth of an underwater object has been known, I just go real slow and have always so far done no damage and have always been able to back off easily.
It may be like bridges, you think the exact height is known, there is a board indicating it right at the bridge, but it seems bridges are a little higher? Maybe that height is to the lowest point, that light in the middle or something?
__________________
a64pilot is offline   Reply With Quote
Old 10-08-2016, 08:23   #35
Registered User

Join Date: Feb 2016
Location: Great Lakes
Boat: Mid size sloop rigged
Posts: 182
Re: Max Draft?

Uncivilized, the issue here isn't the accuracy of Jim's statements, I think we agreed a measuring tape was the best tool for the job and that for the OPs purposes it probably didn't matter.

The issue is the condescension. Using exclamation "tides" to explain what tides are is extremely condescending.

On the place that I referenced- the Rideau Canal which sees hundreds if not thousands of cruising boats annually is depth controlled to 60". That means even a power boat- like say a 30' Sea Ray only has 22" under the drive leg, so any fixed keel sailboat who is visiting the area is going to want to know their draft to within a couple of inches (which is a potential total range of 4") if they are going to attempt to cross the 60" cills.

People can heckle me all they want because I'm not a regular poster, but the fact is, I go into 60" water with a 56" draft on a regular basis. As do a lot of other people. If water levels are down by a couple of inches I want to know about it before I get there, and I do call ahead to lock stations for depth readings and the lock masters are happy to give them to me because they don't want a big cruising sailboat stuck in their lock.
__________________
Ungvar is offline   Reply With Quote
Old 10-08-2016, 08:32   #36
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,157
Re: Max Draft???

Quote:
Originally Posted by roverhi View Post
Don't know what the advertised draft Is based on but assume it's a bare boat with fuel water and basic equipment. FWIW our Westsail 32 fully loaded with provisions for at least 6 months, spare fuel and water in Gerry jugs, 3 anchors, 230' of 3/8" chain and everything we accumulated for our living needs, was 6" down on the molded in waterline. On my current boat with a much lighter but still extensive loading, have raised the waterline 2".
Yep, my Passport 47 was down 5" fully loaded. All that stuff went across the dock to the 42 ft catamaran, which was only down <2".
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 10-08-2016, 08:47   #37
Registered User

Join Date: Feb 2016
Location: Great Lakes
Boat: Mid size sloop rigged
Posts: 182
Re: Max Draft?

See attached rule curves for the Rideau canal, this isn't a place I have made up.


Rideau Lakes' Rule Curves


But I do stand corrected on point I made, I said 100's if not thousands of boats visited the Rideau annually. The actual figure for 2015 was in the neighbourhood of 58000. So I'm not the only person doing this.
__________________
Ungvar is offline   Reply With Quote
Old 10-08-2016, 09:13   #38
Senior Cruiser
 
hpeer's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: Philadelphia
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 3,807
Re: Max Draft?

1- I set our depth finder to zero, then the damn thing reset itself, 3times. Now I just leave it alone and add 3 feet for th offset. Under 3 feet I'm aground.
2- Or should be, because often I ain't. The sounder is reading weeds or loose silt or whatever.
3- sometimes the depth changes upon my passage. Leave a 26" wide channel behind me as I go.
4- sometimes that 26" wide channel abruptly stops. Sigh!

All joking aside, they are new sailors, they will run aground and survive, especially if they sail in muddy water. So my advice is be careful, but don't ruin your trip ruminating. If you sail in rocks, then be very careful and ruminate a bit.
__________________
hpeer is offline   Reply With Quote
Old 10-08-2016, 14:42   #39
Registered User
 
El Pinguino's Avatar

Join Date: Aug 2013
Location: Port Stanley, Falkland Islands, waiting on weather..
Boat: 39' Westerly Sealord
Posts: 3,906
Re: Max Draft?

Quote:
Originally Posted by Ungvar View Post
2" of error on a 5' draft is a 3.3% margin of error. In terms of a circle, that is equivalent to 12 degrees. When you are plotting a course, are you cool with a 12 degree margin of error in your course? At any given time you may be off course by 20 degrees, just like when you are in the bottom of a trough your draft might be 6 feet deeper then when you are on a crest. If you know what your course should be, to within the degree you can correct, if you're okay with a 12 degree error in plotting a course, in a static environment, you certainly would not be welcome to navigate my boat.

The kind of inaccuracy your talking about could mean departing New York for Morocco and hitting Northern Spain. You might be okay with that,
but I sail in thin water, all the time and thousands of other people do too. I know my draft to within a couple of inches, and armed with that knowledge, I can make informed decisions. If I chose to be ignorant of my actual draft (at the time I leave dock, not at any given moment in time), I would be aground a lot more than I am or alternatively, I'd be to frightened to ever leave the dock.

If the OP asked the question, then there might be a very real reason they are concerned about their actual draft, which can only be determined as other posters have said, with a measuring tape. They might be playing in very marginal water, some of us do that you know? I get it, you and Jim don't, you play offshore in blue water, but not every body does.
I don't always play in blue water but I do play in areas where precise depths aren't known so my thought processes reflect that.
I will grant that... yes... if in home waters and dealing with sills where absolute water depths are known you can work to very fine tolerances. Just look at the clearances they live with daily in the Panama canal frinstance.

__________________

El Pinguino is offline   Reply With Quote
Reply

Tags
draft

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:30.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.