Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 14-10-2016, 16:11   #106
Registered User

Join Date: Jun 2015
Posts: 707
Re: Max righting moment question

Quote: "I'll take "the ce is in midships allowing me to Wear or tack for 500.?"

Nope! The Centre of Effort [CE] of the rig is a movable feast. Just where it is located at any given moment depends on what sails you are wearing, what you are doing with the sheets and how much the boat is heeled! What DOESN'T move [much :-)] is the Centre of Effort of the underwater profile. Although that does move somewhat, too, depending on the angle of heel

So what you are interested in for balance is NOT where the CE of the rig lies in relation to the boat's hull. You are interested in where it lies in relation to the CE of the underwater profile. And good luck with determining that theoretically. You can really ONLY do it by the feel of the tiller. Which is one reason wheel steering is dysfunctional in small boats. There are others :-) If two extended fingers of your hand resting gently against the leeward side of the fore end of the tiller keeps the boat on course, but the boat turns gently to weather when you remove your fingers from the tiller, you know you've got it right :-) For any given combination of sail, you can find that sweet spot by fiddling with your sheets.

As for the roller-furl: Yes, okay, if you are going to be sailing in conditions it sounds like you are not yet quite ready for, then there is merit in being able to strike your hdsl without leaving the cockpit. But King Neptune may well get very, very cross with you unless you learn to handle yourself on deck before you graduate to the use of mod cons ;-) "One hand for the ship and the other for yourself!"

Now here is an educational exercise for you: Trim your mainsl so it drives her on a beam reach. Then roll out your window blind so it only fills, say, 1/2 of your fore-triangle. The jib won't draw worth a hoot, and it won't help to drive her, cos the canvas will be all bundled up on the forestay and wrecking the airflow. You'll be using the hdsl only to balance the boat. Do it on a day with about 10 knots of wind. in 20 knts you'd only confuse yourself :-) Note how the tiller feels when you do it. Then, keeping her on a beam reach, roll out some more canvas so it fills the foretriangle completely. Note what that does to the feel of the tiller. Then retract the hdsl completely, while still keeping her on a beam reach, and note what THAT does to the feel of the tiller. I guarantee you that you will now have an intuitive understanding of "balance" :-).

TrentePieds
__________________

__________________
TrentePieds is offline   Reply With Quote
Old 14-10-2016, 16:43   #107
Registered User

Join Date: Jun 2015
Posts: 707
Re: Max righting moment question

Quote: "Lazy jacks don't make single handing easier?"

No, they don't! Lazy jacks are for when you have more canvas to handle than you can do with your bare fists all by yourself. Depending on the deck layout (because of the need to keep your footing) that means that they are unnecessary until you get somewhere above 45 foot LOA and your canvas grows to over 400 SqFt per piece. On a little toy-ship like the EH24 they are, IMO, just a silly affectation. In BIG sailboats they are often a necessary evil, just like wheel steering is. Big ships and little ships are NOT the same! Two different breedsacat that require different kindsa handling!

Now jiffy reefing, that's the cat's pyjamas in a little toy-ship, but like every other kinda gear it has to be set up right, and what is "right" is hardly intuitive :-) I asked about your spars because what they are made of determines what kinda hardware you use. We can come back to that.

What canal is that, then :-)? Hood Canal? Or did you mean THE Channel? or mebbe Catalina Channel? Whatever canal you meant - you're on :-0)!!!

TrentePieds
__________________

__________________
TrentePieds is offline   Reply With Quote
Old 14-10-2016, 16:49   #108
Registered User
 
Don C L's Avatar

Join Date: Sep 2014
Location: Channel Islands, CA
Boat: 1962 Columbia 29 MK 1 #37
Posts: 2,624
Images: 16
Re: Max righting moment question

Quote:
Originally Posted by TrentePieds View Post
What DOESN'T move [much :-)] is the Centre of Effort of the underwater profile. Although that does move somewhat, too, depending on the angle of heel

TrentePieds
small point of correction: Center of Lateral Resistance
it's actually not hard to find if you want to go to the trouble. Take the boat out, have somebody throw you a line from a boat to pull you. You stand in the middle or so of the boat and you go fore and aft till the boat is being pulled directly sideways. Voila! Where you are standing is the CLR. But really, if you have the original rig up, it will sail as designed and will have a certain amount of weather helm.
__________________
DL
Pythagoras
1962 Columbia 29 MKI #37
Don C L is offline   Reply With Quote
Old 14-10-2016, 17:07   #109
Registered User

Join Date: Sep 2016
Location: Chesapeake southern new jersey
Boat: Eastward ho 24
Posts: 69
Re: Max righting moment question

Yes I've been getting the "feel" of her my last few trips and as you mentioned I had my fingers on the tiller gently feeling that sweet spot. Hah I can't remember if it was lee or weather helm I was feeling, but on a reach is where it really seemed to be easiest for me to feel like I was letting her sail as she needed rather then wrestle it the tiller. If my ( burnt out) memory suits me I think I was gently correcting weather helm. But I'm gonna do exactly as you say there when I'm on a beam reach I would always pull the boom down keeping her in the center and stiff. But lately I've been easing it out a little bit and it feels better. When I'm on a run she handles very well some times it seems my main will steal the air from the gen you and she'll luff even though the mainsail is nice and full. Haven't figured that on yet. Yes I need the time behind the tiller but it's good to hear what I should be looking for. Got home from work neighbors were gone able to get a good pic of boat showing the mast and the "rake" that's been on my mind , look ok? And as for the sprit been looking for "Jsp" dimension and no luck. I did get out the micrometer put it to the screen and figured looks like 28 " according to the boat on sailboat data pic. Or the same distance as the fore bottom edge of dog hose window to the bottom leading edge of the aft dog house window. That too is roughly 28 " thoughts on that ,longer , shorter ? I'm a union welder I can tig weld the crack of dawn ( haha welder humor). I can tig stainless was thinking of getting some 316l and whipping something up. The wood ones are so nice looking my boomkin wood and I hate that , I don't trust wood. Been reading Douglas fir planks epoxied w grains opposing is the usual route....The rabbit hole gets deeper. Looking at other eh24 I see more w/o bowsprits then with but I'm thinking adding can only help.
Attached Thumbnails
Click image for larger version

Name:	IMG_0247.jpg
Views:	19
Size:	404.6 KB
ID:	132888  
__________________
Eastward ho 24 is online now   Reply With Quote
Old 14-10-2016, 17:13   #110
Registered User

Join Date: Sep 2016
Location: Chesapeake southern new jersey
Boat: Eastward ho 24
Posts: 69
Re: Max righting moment question

Meant the Panama Canal haha or I'll hit the straits of Magellan and head up your way
__________________
Eastward ho 24 is online now   Reply With Quote
Old 14-10-2016, 17:42   #111
Registered User

Join Date: Jun 2015
Posts: 707
Re: Max righting moment question

Quote: "Take the boat out, have somebody throw you a line from a boat.."

Right you are, Don ;-0)! But - "baby steps", eh :-)?

I was waiting for the right moment to tell our new friend about the trick with the cardboard cut-out of the underwater profile. THEN, after that, we'll have a go at finding the CE of the sailplan by using Grade IX trig :-)

We are after basic comprehension here - not elegance of exposition :-)!

Cheers

TrentePieds
__________________
TrentePieds is offline   Reply With Quote
Old 14-10-2016, 18:03   #112
Registered User

Join Date: Jun 2015
Posts: 707
Re: Max righting moment question

Quote: " But lately I've been easing it out a little bit and it feels better."

PrrreeeCISEly :-)! Now don't let the hot shot racing types among us get in your way with explanations that will indeed be true and potentially valuable to you. For now, just go with this: Next time you are out in 10 knots, furl your hdsl so you can focus on what you are doing with your main. Keep the wind on your beam. Let your mainsheet out until the sail luffs (flaps about), then SLOOOWLY haul your sheet until the luff of the sail JUST fills with wind. Now look carefully at the shape of the sail. The "backside" of it, the lee side, will have a curved shape just like the top surface on a sailplane's wing. THAT's where you drive comes from. Wait a few moments and you'll feel the boat begin to accelerate, but she won't be heeling very much. When she's going as fast as she'll go, like that, haul some more on the sheet, and you'll find that she'll begin to heel more, and she'll begin to slow down. So now you've found one more "sweet spot" to work with :-)

An EH24 will sail best when you trim the main so as to JUST "kill the luff", i.e just make the first foot or two of the main "fill with wind". In terms of aerodynamics that is not, actually, what happens. What DOES happen is that a partial vacuum is created on the "backside" (the lee side) of the sail, and that is what makes the sail take up its intended shape, and that is what sucks the boat forward. The boat isn't being PUSHED forward - it is being SUCKED forward. You really need to come to understand that thoroughly.

So what is the "intended shape"? Well, that depends. For now just know that the shape of the sail when JUST drawing as explained above, is determined mainly by what the sailmaker has done with the "mitre seam", the seam that runs from the tack to the leech. No need to go into that now. Just know that the sail HAS an "intended shape", and that it is YOUR job as "sailing master" to learn all you have to learn to ensure that the sail does, indeed, take that shape.

TrentePieds
__________________
TrentePieds is offline   Reply With Quote
Old 15-10-2016, 07:27   #113
Registered User

Join Date: Sep 2016
Location: Chesapeake southern new jersey
Boat: Eastward ho 24
Posts: 69
Re: Max righting moment question

It is getting cold out here cardboard cut outs sound promising
__________________
Eastward ho 24 is online now   Reply With Quote
Old 15-10-2016, 11:20   #114
Registered User

Join Date: Jun 2015
Posts: 707
Re: Max righting moment question

If you want to do the cardboard number, you'll need a decent surface on which to draw out the profile to an appropriate scale. Since she's 24 feet long, drawing her at 1 inch = 1 foot you'd need a drafting surface about 30" long so you have a bit of overhang both ends, and commensurately high.

That might be a bit cumbersone, but 1/2 inch = 1 foot would be a bit small for our purposes, so settle for the compromise of 3/4 inch = 1 foot.

Now print out the profile from sailboatdata.com and draw on it a grid of equally spaced lines so the whole printout is covered with squares made by the lines you draw. They should all be spaced the same, namely i/12th of whatever the boat's actual length is on the print-out.

Then on your cardboard you draw a grid with lines spaced 1 1/2 inches. Do the math. At 3/4" to the foot, 1 1/2" represents 2 feet, so if you have 12 spaces between lines the total length is 24 feet, and the actual length of the drawing on the cardboard will be 18".

Now, using your eyeball, sketch in the outline of the profile on the cardboard so that the places where the outline you're drawing cuts the grid lines on the cardboard at the same as the places where the outline on the Print-out cuts the grid lines on it.

Now cut out the cardboard profile. Pin it to a wall with a drawing pin near one of its extremities, and using a plumb bob to find the place, put a mark at the other extremity immediately below the suspension point. Use a straight edge to draw a line connecting the two. Then turn the cut-out through about 90 degrees and suspend it again, and mark it again as before. Where the two lines cross somewhere in the middle of your cutout is the Lateral Centre of Effort.

It's that simple. This is how it was done for hundreds of years before computers came along and made a sailor and a naval architect of very Tom, Dick and Harry ;-)!

Next time: Finding the CE of a sail, and finding the Combined Centre of Effort (CCE) of several sails together.

TrentePieds
__________________
TrentePieds is offline   Reply With Quote
Old 15-10-2016, 11:48   #115
Registered User

Join Date: Sep 2016
Location: Chesapeake southern new jersey
Boat: Eastward ho 24
Posts: 69
Re: Max righting moment question

Sounds like a very useful tool I'm gonna do it. Don't have a printer though. I'll figure somthing out.
__________________
Eastward ho 24 is online now   Reply With Quote
Old 15-10-2016, 12:03   #116
Registered User

Join Date: Sep 2016
Location: Chesapeake southern new jersey
Boat: Eastward ho 24
Posts: 69
Re: Max righting moment question

A little yacht that looks good and sails well - Cruising Sailboats Reference

Already done for me? I'll have to pull it up on laptop to get a better look I'm on my phone ( at work of course )
__________________
Eastward ho 24 is online now   Reply With Quote
Old 15-10-2016, 14:01   #117
Registered User

Join Date: Jun 2015
Posts: 707
Re: Max righting moment question

No, not really - not all of it. The CE of each sail, and the CCE of the two sails together, are indicated by conventional notations on the sail plan. Immediately under the waterline on the sail plan you'll see two marks. They are where the perpendiculars dropped from the CE(main) and the CCE intersect the waterline. This gives you an indication of the "lead" when under all sail and under main alone, except that we are still missing the location of the Centre of Effort of the underwater part of the hull. That point is called the Centre of Lateral Resistance or CLR. The sailplan also implies that EH24 is meant to be sailed under main alone, rather than under hdsl alone, for if the latter had been the case, the intersect from the CE(hdsl) woulda been shown.

"Lead" is the distance by which the CCE of the rig lags or precedes the CLR, and it is this distance that determines the "balance", i.e. how the boat steers under canvas.

You also learn from the sail plan that "no sprit" is a viable option for this boat, and that the hdsl is a club-footed jib, i.e a jib on a boom. The reason that it is made club-footed is that that makes tacking ("going about") a LOT easier. It also makes the sail steadier when before the wind and wung out which is nice for single-handing. The boom would ideally have a gooseneck attaching to a samson post sticking up from the deck cos this samson post is the cats whiskers for belaying your anchor rode. More about stuff like that later. The jib boom obviously needs to clear the mast as it swings, and that tells us that a 150% genny is an aberration on this boat.

You can also tell by eyeballing the sailplan that rake is normal, and that the degree of rake is that a line dropped vertically from the truck should intersect the sheer just about at the aftermost chainplate. If I remember, you said that using your halyard for a plumb line it drops to just forward of the "pilot house". So you are good in that department.

As for the CLR, it doesn't seem to have been indicated. That's where the cardboard trick comes in :-). The CG mark near the bottom of the keel indicates the weight of the ballast keel and its centre of gravity which is important in calculating how the boat will float on her lines, but sez nothing about the "lead".

But by this time, considerations of lead are becoming somewhat academic for you have already told me that when you trim your sheets correctly, rather than strap the main down tight, she has a slight weather helm. That's exactly what you want.

So stop worrying about naval architecture and start learning to be a competent boat handler and deck screw. When you have that under your belt, we can start to think about becoming a competent skipper :-).

TrentePieds
__________________
TrentePieds is offline   Reply With Quote
Old 16-10-2016, 05:41   #118
Registered User

Join Date: Sep 2016
Location: Chesapeake southern new jersey
Boat: Eastward ho 24
Posts: 69
Re: Max righting moment question

I have the job boom, and there's a gooseneck on a forestay wire ( not attached to the deck just a kind of goose neck on a swivel on the forestry wire), the po said it was a self tacking jib, or a self tending jib with 2 head sails the po gave me all in very good shape..do you think I should add a sprit put the 150% on it out as far as feesable and reattach the self tacking jib. Would that be worth any advantage options it may give me?
__________________
Eastward ho 24 is online now   Reply With Quote
Old 16-10-2016, 21:30   #119
Registered User
 
Don C L's Avatar

Join Date: Sep 2014
Location: Channel Islands, CA
Boat: 1962 Columbia 29 MK 1 #37
Posts: 2,624
Images: 16
Re: Max righting moment question

Quote:
Originally Posted by Eastward ho 24 View Post
I have the job boom, and there's a gooseneck on a forestay wire ( not attached to the deck just a kind of goose neck on a swivel on the forestry wire), the po said it was a self tacking jib, or a self tending jib with 2 head sails the po gave me all in very good shape..do you think I should add a sprit put the 150% on it out as far as feesable and reattach the self tacking jib. Would that be worth any advantage options it may give me?
My vote is yes to that. I believe that is how it was meant to be. The self tending jib would then be used in higher winds.
__________________
DL
Pythagoras
1962 Columbia 29 MKI #37
Don C L is offline   Reply With Quote
Old 17-10-2016, 01:04   #120
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 2,601
Re: Max righting moment question

Quote:
Originally Posted by Eastward ho 24 View Post
I have the job boom, and there's a gooseneck on a forestay wire ( not attached to the deck just a kind of goose neck on a swivel on the forestry wire), the po said it was a self tacking jib, or a self tending jib with 2 head sails the po gave me all in very good shape..do you think I should add a sprit put the 150% on it out as far as feesable and reattach the self tacking jib. Would that be worth any advantage options it may give me?
I'd personally set it up as a removable stay solent type stay, prehaps dynex dux. But for now maybe simplicity counts while you learn the ropes.

To me the rake in the pictures looks excessive.
__________________

__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Reply

Tags
men

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Righting a Capsized Tri DaveOnCudjoe Multihull Sailboats 32 21-11-2013 09:40
Righting Moment Data - Fisher 46 blue merlin Monohull Sailboats 4 18-12-2009 19:48
righting a multi gone turtle sail_the_stars Multihull Sailboats 110 15-06-2008 04:31


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:27.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.